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Sample records for 193-nm excimer laser

  1. Advances in 193 nm excimer lasers for mass spectrometry applications

    NASA Astrophysics Data System (ADS)

    Delmdahl, Ralph; Esser, Hans-Gerd; Bonati, Guido

    2016-03-01

    Ongoing progress in mass analysis applications such as laser ablation inductively coupled mass spectrometry of solid samples and ultraviolet photoionization mediated sequencing of peptides and proteins is to a large extent driven by ultrashort wavelength excimer lasers at 193 nm. This paper will introduce the latest improvements achieved in the development of compact high repetition rate excimer lasers and elaborate on the impact on mass spectrometry instrumentation. Various performance and lifetime measurements obtained in a long-term endurance test over the course of 18 months will be shown and discussed in view of the laser source requirements of different mass spectrometry tasks. These sampling type applications are served by excimer lasers delivering pulsed 193 nm output of several mJ as well as fast repetition rates which are already approaching one Kilohertz. In order to open up the pathway from the laboratory to broader market industrial use, sufficient component lifetimes and long-term stable performance behavior have to be ensured. The obtained long-term results which will be presented are based on diverse 193 nm excimer laser tube improvements aiming at e.g. optimizing the gas flow dynamics and have extended the operational life the laser tube for the first time over several billion pulses even under high duty-cycle conditions.

  2. 193 nm excimer laser sclerostomy in pseudophakic patients with advanced open angle glaucoma.

    PubMed Central

    Allan, B D; van Saarloos, P P; Cooper, R L; Constable, I J

    1994-01-01

    A modified open mask system incorporating an en face air jet to dry the target area during ablation and a conjunctival plication mechanism, which allows ab externo delivery of the 193 nm excimer laser without prior conjunctival dissection, has been developed to form small bore sclerostomies accurately and atraumatically. Full thickness sclerostomies, and sclerostomies guarded by a smaller internal ostium can be created. A pilot therapeutic trial was conducted in pseudophakic patients with advanced open angle glaucoma. Six full thickness sclerostomies (200 microns and 400 microns diameter) and three guarded sclerostomies were created in nine patients by 193 nm excimer laser ablation (fluence per pulse 400 mJ/cm2, pulse rate 16 Hz, air jet pressure intraocular pressure +25 mm Hg). After 6 months' follow up, intraocular pressure was controlled (< or = 16 mm Hg) in eight of the nine patients (6/9 without medication). Early postoperative complications included hyphaema (trace--2.5 mm) (6/9), temporary fibrinous sclerostomy occlusion (4/9), profound early hypotony (all patients without fibrinous occlusion), and suprachoroidal haemorrhage in one case. Conjunctival laser wounds were self sealing. Small bore laser sclerostomy procedures are functionally equivalent to conventional full thickness procedures, producing early postoperative hypotony, with an increased risk of suprachoroidal haemorrhage in association with this. Further research is required to improve control over internal guarding in excimer laser sclerostomy before clinical trials of this technique can safely proceed. Images PMID:8148335

  3. Microsurgery of the retina with a needle-guided 193-nm excimer laser.

    PubMed

    Lewis, A; Palanker, D; Hemo, I; Pe'er, J; Zauberman, H

    1992-07-01

    This article presents a method used to guide the beam from an argon fluoride excimer laser to make it suitable for microsurgical purposes and confine it to areas that can be varied in dimension from 1 micron to tens or hundreds of microns. This approach guides the excimer laser beam with an articulated mechanical arm and confines it with variable-diameter tapered tubes, possibly allowing the use of this laser in in vitro retinal surgery with endolaser techniques. Currently, because of the lack of a delivery and focusing system for the 193-nm argon fluoride beam and its absorption by biologic liquids, this laser is used exclusively in ophthalmology for topical applications, such as corneal sculpting. This new method resolves these problems in a unique way with impressive results. Specifically, it was shown that, with this needle-guided excimer laser, it is possible to remove retinal tissue accurately without detectable damage to surrounding cells. Applications of this new technique in retinal surgery are discussed. PMID:1634334

  4. 193 nm Excimer laser processing of Si/Ge/Si(100) micropatterns

    NASA Astrophysics Data System (ADS)

    Gontad, F.; Conde, J. C.; Chiussi, S.; Serra, C.; González, P.

    2016-01-01

    193 nm Excimer laser assisted growth and crystallization of amorphous Si/Ge bilayer patterns with circular structures of 3 μm diameter and around 25 nm total thickness, is presented. Amorphous patterns were grown by Laser induced Chemical Vapor Deposition, using nanostencils as shadow masks and then irradiated with the same laser to induce structural and compositional modifications for producing crystalline SiGe alloys through fast melting/solidification cycles. Compositional and structural analyses demonstrated that pulses of 240 mJ/cm2 lead to graded SiGe alloys with Si rich discs of 2 μm diameter on top, a buried Ge layer, and Ge rich SiGe rings surrounding each feature, as predicted by previous numerical simulation.

  5. White-Light Emission from Silicone Rubber Modified by 193 nm ArF Excimer Laser

    NASA Astrophysics Data System (ADS)

    Okoshi, Masayuki; Sekine, Daisuke; Inoue, Narumi; Yamashita, Tsugito

    2007-04-01

    The photochemical surface modification of silicone ([SiO(CH3)2]n) rubber has been successfully demonstrated using a 193 nm ArF excimer laser, and white light of strong intensity was emitted upon exposure to a 325 nm He-Cd laser. The photoluminescence spectra of the modified silicone showed broad peaks centered at 410, 550, and 750 nm wavelengths. The modified surface was carbon-free silicon oxide, and the chemical composition ratio of O/Si was approximately 2. However, the surface was not silica glass (SiO2), as clarified by IR spectroscopy. Instead, nanometer-size particles of silicon oxide were formed on the surface of the modified silicone rubber.

  6. Photoacoustic injury and bone healing following 193nm excimer laser ablation.

    PubMed

    Lustmann, J; Ulmansky, M; Fuxbrunner, A; Lewis, A

    1992-01-01

    The argon-fluoride excimer laser was investigated as a cutting-ablating tool for bone surgery. A total of 52 rats were divided into two experimental groups and two control groups. In one experimental group cortical bone defects were made; in another experimental group defects penetrating into the medullary space were performed. In the two control groups similar defects were achieved using water-cooled carbide burs. The rats were sacrificed on each of the 3, 7, 10, 20, 30, and 40 postoperative day. The cortical bone, the medullary space, and the extrabony tissue were examined by means of light microscopy. In both experimental groups, bone damage, represented by osteocyte destruction, extended to 1,050-1,450 microns ahead from the irradiated site, and bone healing was very much impaired. In the control groups no histological changes could be identified and bone healing appeared to be within normal limits. We believe this extensive bone damage, following 193 nm irradiation, to be a result of photoacoustic waves propagating in the bone following each pulse. In view of our results we feel that excimer lasers presently in use are not suitable for bone surgery. This problem of photoacoustic damage can be overcome in one of two ways: by designing a CW excimer laser or by reducing the pulse width to the picosecond regime. PMID:1495367

  7. Photon-controlled fabrication of amorphous superlattice structures using ArF (193 nm) excimer laser photolysis

    SciTech Connect

    Lowndes, D.H.; Geohegan, D.B.; Eres, D.; Pennycook, S.J.; Mashburn, D.N.; Jellison G.E. Jr.

    1988-05-30

    Pulsed ArF (193 nm) excimer laser photolysis of disilane, germane, and disilane-ammonia mixtures has been used to deposit amorphous superlattices containing silicon, germanium, and silicon nitride layers. Transmission electron microscope cross-section views demonstrate that structures having thin (5--25 nm) layers and sharp interlayer boundaries can be deposited at substrate temperatures below the pyrolytic threshold, entirely under laser photolytic control.

  8. Soft-tissue removal by the 193-nm excimer laser in a strongly absorbing liquid environment

    NASA Astrophysics Data System (ADS)

    Palanker, Daniel; Hemo, Itzhak; Turovets, Igor; Lewis, Aaron

    1994-08-01

    The 193 nm excimer laser delivered through special tips into biological liquid environments was applied to two different fields of microsurgery and two mechanism of tissue ablation were found to be operative. In vitreoretinal surgical applications, where the tip exit diameter was about 250 micrometers , the effective cutting regime of retina and vitreoretinal membranes occurred at energy fluences of about 250 - 350 mJ/cm2/pulse with a corresponding cutting depth of 50 - 150 micrometers /pulse. Gas bubbles, formed at the tip exit when it touched the tissue during irradiation, seem to be the driving force underlying the cutting process. This enabled us to achieve a much deeper cut in tissue than a micron-sized laser penetration depth. The system was applied to bovine and rabbit retina and rabbit vitreoretinal membranes and it was found that such tissue removal is fast enough for real vitreoretinal applications and the cut depth control is still good enough for this microsurgery. In the application of this system to drilling of 4 - 8 micrometers diameter holes in the zona pellucida of oocytes the optimal energy fluence is about 40 mJ/cm2/pulse with an ablation depth of about 2 micrometers /pulse. In this case no bubbles are formed and the process seems to be a non-explosive photodissociation of the tissue with subsequent slow dissolution of the products. This mechanism, in contrast to the vitreoretinal tissue removal, was found to be very selective to the type of material being ablated. This process was studied on a model of 20% gelatin gel, which is very close to the ablation properties of the zona pellucida.

  9. Extremely long life and low-cost 193nm excimer laser chamber technology for 450mm wafer multipatterning lithography

    NASA Astrophysics Data System (ADS)

    Tsushima, Hiroaki; Katsuumi, Hisakazu; Ikeda, Hiroyuki; Asayama, Takeshi; Kumazaki, Takahito; Kurosu, Akihiko; Ohta, Takeshi; Kakizaki, Kouji; Matsunaga, Takashi; Mizoguchi, Hakaru

    2014-04-01

    193nm ArF excimer lasers are widely used as light sources for the lithography process of semiconductor production. 193nm ArF exicmer lasers are expected to continue to be the main solution in photolithography, since advanced lithography technologies such as multiple patterning and Self-Aligned Double Patterning (SADP) are being developed. In order to apply these technologies to high-volume semiconductor manufacturing, the key is to reduce the total operating cost. To reduce the total operating cost, life extension of consumable part and reduction of power consumption are an important factor. The chamber life time and power consumption are a main factor to decide the total operating cost. Therefore, we have developed the new technology for extension of the chamber life time and low electricity consumption. In this paper, we will report the new technology to extend the life time of the laser chamber and to reduce the electricity consumption.

  10. Update on laser vision correction using wavefront analysis with the CustomCornea system and LADARVision 193-nm excimer laser

    NASA Astrophysics Data System (ADS)

    Maguen, Ezra I.; Salz, James J.; McDonald, Marguerite B.; Pettit, George H.; Papaioannou, Thanassis; Grundfest, Warren S.

    2002-06-01

    A study was undertaken to assess whether results of laser vision correction with the LADARVISION 193-nm excimer laser (Alcon-Autonomous technologies) can be improved with the use of wavefront analysis generated by a proprietary system including a Hartman-Schack sensor and expressed using Zernicke polynomials. A total of 82 eyes underwent LASIK in several centers with an improved algorithm, using the CustomCornea system. A subgroup of 48 eyes of 24 patients was randomized so that one eye undergoes conventional treatment and one eye undergoes treatment based on wavefront analysis. Treatment parameters were equal for each type of refractive error. 83% of all eyes had uncorrected vision of 20/20 or better and 95% were 20/25 or better. In all groups, uncorrected visual acuities did not improve significantly in eyes treated with wavefront analysis compared to conventional treatments. Higher order aberrations were consistently better corrected in eyes undergoing treatment based on wavefront analysis for LASIK at 6 months postop. In addition, the number of eyes with reduced RMS was significantly higher in the subset of eyes treated with a wavefront algorithm (38% vs. 5%). Wavefront technology may improve the outcomes of laser vision correction with the LADARVISION excimer laser. Further refinements of the technology and clinical trials will contribute to this goal.

  11. Excimer laser photochemistry of silane-ammonia mixtures at 193 nm

    SciTech Connect

    Beach, D.B.; Jasinski, J.M. )

    1990-04-05

    The ArF excimer laser induced photochemistry of silane-ammonia mixtures has been studied with molecular beam sampling mass spectrometry. The observed products include disilane, trisilane, and all possible aminosilanes, SiH{sub x}(NH{sub 2}){sub 4-x}, x = 0-3. These products are formed under steady-state photolysis conditions and under single-laser-pulse conditions. A mechanism for the formation of these species is proposed and quantitatively evaluated.

  12. 193-nm excimer laser sclerostomy using a modified open mask delivery system in rhesus monkeys with experimental glaucoma.

    PubMed

    Allan, B D; van Saarloos, P P; Cooper, R L; Keogh, E J; Constable, I J

    1993-11-01

    Excimer laser sclerostomy is a new glaucoma filtration procedure in which the argon fluoride excimer laser at 193 nm is delivered ab externo through a modified open mask system incorporating an en-face air jet to dry the target area and preserve hemostasis during ablation and a conjunctival plication mechanism, which allows the conjunctival and scleral wounds created by through-and-through ablation to separate once the mask is removed. No preparatory dissection of the conjunctiva is required. Five 200-microns and five 500-microns sclerostomies were formed by ablation at a pulse repetition rate of 20 Hz and a fluence per pulse of 400 mJ/cm2 in fellow eyes of five rhesus monkeys with experimental glaucoma. Overall, seven of the ten eyes attained a functional result, with intraocular pressures remaining below 21 mmHg for 6 +/- 1 days and rising to the pre-operative level after 10 +/- 3 days without adjunctive antifibroblast medication. The duration of filtration for 200-microns and 500-microns sclerostomies was similar, and parallels that previously observed for posterior lip sclerectomy in the same animal model. The three eyes with no functional result all had incorrectly positioned sclerostomies. Choroidal detachment and significant shallowing of the anterior chamber did not occur. Excimer laser sclerostomy appears to be a viable technique for filtration, provided that mask placement is accurate. PMID:8258402

  13. Surface morphology and subsurface damaged layer of various glasses machined by 193-nm ArF excimer laser

    NASA Astrophysics Data System (ADS)

    Liao, Yunn-shiuan; Chen, Ying-Tung; Chao, Choung-Lii; Liu, Yih-Ming

    2005-01-01

    Owing to the high bonding energy, most of the glasses are removed by photo-thermal rather than photo-chemical effect when they are ablated by the 193 or 248nm excimer lasers. Typically, the machined surface is covered by re-deposited debris and the sub-surface, sometimes surface as well, is scattered with micro-cracks introduced by thermal stress generated during the process. This study aimed to investigate the nature and extent of the surface morphology and sub-surface damaged (SSD) layer induced by the laser ablation. The effects of laser parameters such as fluence, shot number and repetition rate on the morphology and SSD were discussed. An ArF excimer laser (193 nm) was used in the present study to machine glasses such as soda-lime, Zerodur and BK-7. It is found that the melt ejection and debris deposition tend to pile up higher and become denser in structure under a higher energy density, repetition rate and shot number. There are thermal stress induced lateral cracks when the debris covered top layer is etched away. Higher fluence and repetition rate tend to generate more lateral and median cracks which propagate into the substrate. The changes of mechanical properties of the SSD layer were also investigated.

  14. Effect of hydrogen bonding on far-ultraviolet water absorption and potential implications for 193-nm ArF excimer laser-tissue interaction

    NASA Astrophysics Data System (ADS)

    Walsh, Joseph T., Jr.; Staveteig, Paul T.

    1995-05-01

    The mechanisms causing transient 193-nm optical absorption of collagen during ablative-fluence ArF excimer pulses are poorly understood. The preponderance of hypotheses proposed to explain this phenomenon, such as ultrafast secondary-structure denaturation of proteins and transient free radical formation, focus on the protein matrix and ignore potential contributions from other tissue components such as water. A substantial body of spectroscopic literature places 193 nm adjacent to a steep absorption edge of water that rises to 60,000 cm-1 at 163 nm; other evidence shows that this absorption edge shifts toward 193 nm upon hydrogen-bond breakage. In this paper we show that heating of water from 20-100°C increases the liquid's absorption coefficient. Further investigations using an infrared pump laser show a significant increase in absorption by water of a 193-nm probe beam. Based on this evidence, we speculate that 193-nm laser ablation of tissue may contain a photothermal component related to dynamic absorption of incident radiation by water.

  15. The interaction of 193-nm excimer laser irradiation with single-crystal zinc oxide: Neutral atomic zinc and oxygen emission

    SciTech Connect

    Kahn, E. H.; Langford, S. C.; Dickinson, J. T.; Boatner, Lynn A

    2013-01-01

    We report mass-resolved time-of-flight measurements of neutral particles from the surface of single-crystal ZnO during pulsed 193-nm irradiation at laser fluences below the threshold for avalanche breakdown. The major species emitted are atomic Zn and O. We examine the emissions of atomic Zn as a function of laser fluence and laser exposure. Defects at the ZnO surface appear necessary for the detection of these emissions. Our results suggest that the production of defects is necessary to explain intense sustained emissions at higher fluence. Rapid, clean surface etching and high atomic zinc kinetic energies seen at higher laser fluences are also discussed.

  16. Development of high coherence high power 193nm laser

    NASA Astrophysics Data System (ADS)

    Tanaka, Satoshi; Arakawa, Masaki; Fuchimukai, Atsushi; Sasaki, Yoichi; Onose, Takashi; Kamba, Yasuhiro; Igarashi, Hironori; Qu, Chen; Tamiya, Mitsuru; Oizumi, Hiroaki; Ito, Shinji; Kakizaki, Koji; Xuan, Hongwen; Zhao, Zhigang; Kobayashi, Yohei; Mizoguchi, Hakaru

    2016-03-01

    We have been developing a hybrid 193 nm ArF laser system that consists of a solid state seeding laser and an ArF excimer laser amplifier for power-boosting. The solid state laser consists of an Yb-fiber-solid hybrid laser system and an Er-fiber laser system as fundamentals, and one LBO and three CLBO crystals for frequency conversion. In an ArF power amplifier, the seed laser passes through the ArF gain media three times, and an average power of 110 W is obtained. As a demonstration of the potential applications of the laser, an interference exposure test is performed.

  17. Evaluation of corneal ablation by an optical parametric oscillator (OPO) at 2.94 μm and an Er:YAG laser and comparison to ablation by a 193-nm excimer laser

    NASA Astrophysics Data System (ADS)

    Telfair, William B.; Hoffman, Hanna J.; Nordquist, Robert E.; Eiferman, Richard A.

    1998-06-01

    Purpose: This study first evaluated the corneal ablation characteristics of (1) an Nd:YAG pumped OPO (Optical Parametric Oscillator) at 2.94 microns and (2) a short pulse Er:YAG laser. Secondly, it compared the histopathology and surface quality of these ablations with (3) a 193 nm excimer laser. Finally, the healing characteristics over 4 months of cat eyes treated with the OPO were evaluated. Methods: Custom designed Nd:YAG/OPO and Er:YAG lasers were integrated with a new scanning delivery system to perform PRK myopic correction procedures. After initial ablation studies to determine ablation thresholds and rates, human cadaver eyes and in-vivo cat eyes were treated with (1) a 6.0 mm Dia, 30 micron deep PTK ablation and (2) a 6.0 mm Dia, -5.0 Diopter PRK ablation. Cadaver eyes were also treated with a 5.0 mm Dia, -5.0 Diopter LASIK ablation. Finally, cats were treated with the OPO in a 4 month healing study. Results: Ablation thresholds below 100 mJ/cm2 and ablation rates comparable to the excimer were demonstrated for both infrared systems. Light Microscopy (LM) showed no thermal damage for low fluence treatments, but noticeable thermal damage at higher fluences. SEM and TEM revealed morphologically similar surfaces for low fluence OPO and excimer samples with a smooth base and no evidence of collagen shrinkage. The Er:YAG and higher fluence OPO treated samples revealed more damage along with visible collagen coagulation and shrinkage in some cases. Healing was remarkably unremarkable. All eyes had a mild healing response with no stromal haze and showed topographic flattening. LM demonstrated nothing except a moderate increase in keratocyte activity in the upper third of the stroma. TEM confirmed this along with irregular basement membranes. Conclusions: A non- thermal ablation process called photospallation is demonstrated for the first time using short pulse infrared lasers yielding damage zones comparable to the excimer and healing which is also comparable to

  18. Rayleigh rejection filters for 193-nm ArF laser Raman spectroscopy

    NASA Technical Reports Server (NTRS)

    Mckenzie, Robert L.

    1993-01-01

    Selected organic absorbers and their solvents are evaluated as spectral filters for the rejection of 193-nm Rayleigh light associated with the use of an ArF excimer laser for Raman spectroscopy. A simply constructed filter cell filled with 0.5 percent acetone in water and an optical path of 7 mm is shown effectively to eliminate stray Rayleigh light underlying the Raman spectrum from air while transmitting 60 percent of the Raman light scattered by O2.

  19. Collateral damage-free debridement using 193nm ArF laser

    NASA Astrophysics Data System (ADS)

    Wynne, James J.; Felsenstein, Jerome M.; Trzcinski, Robert; Zupanski-Nielsen, Donna; Connors, Daniel P.

    2011-03-01

    Burn eschar and other necrotic areas of the skin and soft tissue are anhydrous compared to the underlying viable tissue. A 193 nm ArF excimer laser, emitting electromagnetic radiation at 6.4 eV at fluence exceeding the ablation threshold, will debride such necrotic areas. Because such radiation is strongly absorbed by aqueous chloride ions through the nonthermal process of electron photodetachment, debridement will cease when hydrated (with chloride ions) viable tissue is exposed, avoiding collateral damage to this tissue. Such tissue will be sterile and ready for further treatment, such as a wound dressing and/or a skin graft.

  20. Generation of intense 10-ps, 193-nm pulses using simple distributed feedback dye lasers and an ArF(*) amplifier.

    PubMed

    Hatten, D L; Cui, Y; Iii, W T; Mikes, T; Goldhar, J

    1992-11-20

    A pair of holographic distributed feedback dye lasers is used to generate 10-ps pulses at two selected wavelengths that are mixed in a BBO crystal to produce a pulse ~ 10 ps in duration at 193 nm. This seed pulse is subsequently amplified in an ArF(*) excimer laser to an energy of 10-15 mJ with <40 microJ in amplified spontaneous emission. The pulses are nearly transform limited and diffraction limited. PMID:20802565

  1. Improving vacuum-UV (VUV) photolysis of organic compounds in water with a phosphor converted xenon excimer lamp emitting at 193 nm.

    PubMed

    Schulze-Hennings, U; Pötschke, L; Wietor, C; Bringmann, S; Braun, N; Hayashi, D; Linnemann, V; Pinnekamp, J

    2016-01-01

    A novel vacuum ultraviolet excimer lamp emitting light at 193 nm was used to investigate the degradation of organic micropollutants in ultrapure water and wastewater treatment plant (WWTP) effluent. Overall, light at 193 nm proved to be efficient to degrade the investigated micropollutants (diclofenac, diatrizoic acid, sulfamethoxazole). Experiments with WWTP effluent proved the ability of radiation at 193 nm to degrade micropollutants which are hardly removed with commonly used oxidation technologies like ozonation (diatrizoic acid, ethylenediaminetetraacetic acid, perfluorooctanoic acid, and perfluorooctanesulfonic acid). PMID:27533863

  2. Excimer lasers

    NASA Technical Reports Server (NTRS)

    Palmer, A. J.; Hess, L. D.; Stephens, R. R.

    1976-01-01

    A theoretical and experimental investigation into the possibility of achieving CW discharge pumped excimer laser oscillation is reported. Detailed theoretical modeling of capillary discharge pumping of the XeF and KXe and K2 excimer systems was carried out which predicted the required discharge parameters for reaching laser threshold on these systems. Capillary discharge pumping of the XeF excimer system was investigated experimentally. The experiments revealed a lower excimer level population density than predicted theoretically by about an order of magnitude. The experiments also revealed a fluorine consumption problem in the discharge in agreement with theory.

  3. Excimer lasers

    NASA Technical Reports Server (NTRS)

    Palmer, A. J.; Hess, L. D.; Stephens, R. R.; Pepper, D. M.

    1977-01-01

    The results of a two-year investigation into the possibility of developing continuous wave excimer lasers are reported. The program included the evaluation and selection of candidate molecular systems and discharge pumping techniques. The K Ar/K2 excimer dimer molecules and the xenon fluoride excimer molecule were selected for study; each used a transverse and capillary discharges pumping technique. Experimental and theoretical studies of each of the two discharge techniques applied to each of the two molecular systems are reported. Discharge stability and fluorine consumption were found to be the principle impediments to extending the XeF excimer laser into the continuous wave regime. Potassium vapor handling problems were the principal difficulty in achieving laser action on the K Ar/K2 system. Of the four molecular systems and pumping techniques explored, the capillary discharge pumped K Ar/K2 system appears to be the most likely candidate for demonstrating continuous wave excimer laser action primarily because of its predicted lower pumping threshold and a demonstrated discharge stability advantage.

  4. Next-generation 193-nm laser for sub-100-nm lithography

    NASA Astrophysics Data System (ADS)

    Duffey, Thomas P.; Blumenstock, Gerry M.; Fleurov, Vladimir B.; Pan, Xiaojiang; Newman, Peter C.; Glatzel, Holger; Watson, Tom A.; Erxmeyer, J.; Kuschnereit, Ralf; Weigl, Bernhard

    2001-09-01

    The next generation 193 nm (ArF) laser has been designed and developed for high-volume production lithography. The NanoLithTM 7000, offering 20 Watts average output power at 4 kHz repetition rates is designed to support the highest exposure tool scan speeds for maximum productivity and wafer throughput. Fundamental design changes made to the laser core technologies are described. These advancements in core technology support the delivery of highly line-narrowed light with

  5. Dynamics of ions produced by laser ablation of several metals at 193 nm

    SciTech Connect

    Baraldi, G.; Perea, A.; Afonso, C. N.

    2011-02-15

    This work reports the study of ion dynamics produced by ablation of Al, Cu, Ag, Au, and Bi targets using nanosecond laser pulses at 193 nm as a function of the laser fluence from threshold up to 15 J cm{sup -2}. An electrical (Langmuir) probe has been used for determining the ion yield as well as kinetic energy distributions. The results clearly evidence that ablation of Al shows unique features when compared to other metals. The ion yield both at threshold (except for Al, which shows a two-threshold-like behavior) and for a fixed fluence above threshold scale approximately with melting temperature of the metal. Comparison of the magnitude of the yield reported in literature using other wavelengths allows us to conclude its dependence with wavelength is not significant. The evolution of the ion yield with fluence becomes slower for fluences above 4-5 J cm{sup -2} with no indication of saturation suggesting that ionization processes in the plasma are still active up to 15 J cm{sup -2} and production of multiple-charged ions are promoted. This dependence is mirrored in the proportion of ions with kinetic energies higher than 200 eV. This proportion is not significant around threshold fluence for all metals except for Al, which is already 20%. The unique features of Al are discussed in terms of the energy of laser photons (6.4 eV) that is enough to induce direct photoionization from the ground state only in the case of this metal.

  6. Development of high coherence, 200mW, 193nm solid-state laser at 6 kHz

    NASA Astrophysics Data System (ADS)

    Nakazato, T.; Tsuboi, M.; Onose, T.; Tanaka, Y.; Sarukura, N.; Ito, S.; Kakizaki, K.; Watanabe, S.

    2015-02-01

    The high coherent, high power 193-nm ArF lasers are useful for interference lithography and microprosessing applications. In order to achieve high coherence ArF lasers, we have been developing a high coherence 193 nm solid state laser for the seeding to a high power ArF laser. We used the sum frequency mixing of the fourth harmonic (FH) of a 904-nm Ti:sapphire laser with a Nd:YVO4 laser (1342 nm) to generate 193-nm light. The laser system consists of a single-mode Ti:sapphire oscillator seeded by a 904-nm external cavity laser diode, a Pockels cell, a 6-pass amplifier, a 4-pass amplifier, a 2-pass amplifier and a wavelength conversion stage. The required repetition rate of 6 kHz corresponding to the ArF laser, along with a low gain at 904 nm induces serious thermal lens effects; extremely short focal lengths of the order of cm and bi-foci in the vertical and horizontal directions. From the analysis of thermal lens depending on pump intensity, we successfully compensated the thermal lens by dividing a 527-nm pump power with 15, 25 and 28 W to 3-stage amplifiers with even passes, resulting in the output power above 10W with a nearly diffraction limited beam. This 904-nm output was converted to 3.8 W in the second harmonic by LBO, 0.5 W in FH by BBO sequentially. Finally the output power of 230 mW was obtained at 193 nm by mixing the FH with a 1342-nm light in CLBO.

  7. Excimer laser photorefractive surgery of the cornea

    NASA Astrophysics Data System (ADS)

    Gaster, Ronald N.

    1998-09-01

    The 193 nm argon fluoride (ArF) excimer laser can effectively be used to change the radius of curvature of the cornea and thus alter the refractive state of the eye. This change allows myopic (nearsighted) patients to see well with less dependence on glasses or contact lenses. The two major techniques of laser refractive surgery currently in effect in the United States are photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). This paper will discuss these refractive cornea surgical techniques.

  8. 300-mW narrow-linewidth deep-ultraviolet light generation at 193 nm by frequency mixing between Yb-hybrid and Er-fiber lasers.

    PubMed

    Xuan, Hongwen; Zhao, Zhigang; Igarashi, Hironori; Ito, Shinji; Kakizaki, Kouji; Kobayashi, Yohei

    2015-04-20

    A narrow-linewidth, high average power deep-ultraviolet (DUV) coherent laser emitting at 193 nm is demonstrated by frequency mixing a Yb-hybrid laser with an Er-fiber laser. The Yb-hybrid laser consists of Yb-fiber lasers and an Yb:YAG amplifier. The average output power of the 193 nm laser is 310 mW at 6 kHz, which corresponds to a pulse energy of 51 μJ. To the best of our knowledge, this is the highest average power and pulse energy ever reported for a narrow-linewidth 193 nm light generated by a combination of solid-state and fiber lasers with frequency mixing. We believe this laser will be beneficial for the application of interference lithography by seeding an injection-locking ArF eximer laser. PMID:25969096

  9. A 193 nm laser photofragmentation time-of-flight mass spectrometric study of chloroiodomethane

    SciTech Connect

    Zhang, Tao; Ng, C.Y.; Qi Fei; Lam, C.-S.; Li, W.-K.

    2005-11-01

    The photodissociation dynamics of chloroiodomethane (CH{sub 2}ICl) at 193 nm has been investigated by employing the photofragment time-of-flight (TOF) mass spectrometric method. Using tunable vacuum ultraviolet undulator synchrotron radiation for photoionization sampling of nascent photofragments, we have identified four primary dissociation product channels: CH{sub 2}Cl+I({sup 2}P{sub 1/2})/I({sup 2}P{sub 3/2}), CH{sub 2}I+Cl({sup 2}P{sub 1/2})/Cl({sup 2}P{sub 3/2}), CHI+HCl, and CH{sub 2}+ICl. The state-selective detection of I({sup 2}P{sub 3/2}) and I({sup 2}P{sub 1/2}) has allowed the estimation of the branching ratio for I({sup 2}P{sub 1/2}):I({sup 2}P{sub 3/2}) to be 0.73: 0.27. Theoretical calculations based on the time-dependent density-functional theory have been also made to investigate excited electronic potential-energy surfaces, plausible intermediates, and transition structures involved in these photodissociation reactions. The translation energy distributions derived from the TOF measurements suggest that at least two dissociation mechanisms are operative for these photodissociation processes. One involves the direct dissociation from the 2 {sup 1}A{sup '} state initially formed by 193 nm excitation, leading to significant kinetic-energy releases. For the I-atom and Cl-atom elimination channels, the fragment kinetic-energy releases observed via this direct dissociation mechanism are consistent with those predicted by the impulsive dissociation models. Other mechanisms are likely predissociative or statistical in nature from the lower 1 {sup 1}A{sup '} and 1 {sup 1}A{sup ''} states and/or the ground X-tilde {sup 1}A{sup '} state populated by internal conversion from the 2 {sup 1}A{sup '} state. On the basis of the maximum kinetic-energy release for the formation of CH{sub 2}Cl+I({sup 2}P{sub 1/2}), we have obtained a value of 53{+-}2 kcal/mol for the 0 K bond dissociation energy of I-CH{sub 2}Cl. The intermediates and transition structures for the CHI

  10. Electron stimulated desorption of the metallic substrate at monolayer coverage: Sensitive detection via 193 nm laser photoionization of neutral aluminum desorbed from CH3O/Al(111)

    NASA Astrophysics Data System (ADS)

    Young, C. E.; Whitten, J. E.; Pellin, M. J.; Gruen, D. M.; Jones, P. L.

    A fortuitous overlap between the gain profile of the 193 nm ArF excimer laser and the Al autoionizing transition (sup 2)S(sub 1/2) (512753/cm) yields to the left (sup 2)P(sup 0)J has been exploited in the direct observation of substrate metal atoms in an electron simulated desorption (ESD) process from the monolayer adsorbate system CH3O/Al(111). The identity of the mass 27 photoion was established as Al(+) by (1) isotopic substitution of C-13 in the methanol employed for methoxy formation, and (2) tunable laser scans utilizing the DJ-2 (J = 3/2, 5/2) intermediate levels at approximately 32436/cm and a 248 nm ionization step. An ESD yield of approximately x 10(exp -6) Al atoms/(electron at 1 keV) was established by comparison with a sputtering experiment in the same apparatus. Velocity distributions measured for the desorbed Al species showed some differences in comparison with methoxy velocity data: a slightly lower peak velocity and a significantly less prominent high-velocity component.

  11. Effect of excimer laser on microbiological organisms

    SciTech Connect

    Keates, R.H.; Drago, P.C.; Rothchild, E.J.

    1988-10-01

    The effect of radiation emitted from an excimer laser filled with argon fluoride gas at 193 nm on Serratia marcescens, Pseudomonas aeruginosa, Staphylococcus aureus, streptococcus faecalis, Hemophilus influenzae, Candida albicans, and Aspergillus niger (collectively labeled the microorganisms) was examined. Colonies were subjected to a variable number of radiation pulses from the excimer laser applied after a 36-hour period of incubation at 37 degrees C, at which time the colonies were fully grown and showed no viability. The lack of viability was confirmed with a subculture from each area that received radiation; all subcultures were negative. The characteristics of the radiation paralleled those used by Serdavic, Darrell, Krueger, et al in 1985. This radiation treatment is believed to be within a therapeutic range, which suggests that the excimer laser, pending further investigation, may be useful in the treatment of corneal infections.

  12. Novel single-layer photoresist containing cycloolefins for 193 nm

    NASA Astrophysics Data System (ADS)

    Park, Joo Hyeon; Seo, Dong-Chul; Kim, Ki-Dae; Park, Sun-Yi; Kim, Seong-Ju; Lee, Hosull; Jung, Jae Chang; Bok, Cheol-Kyu; Baik, Ki-Ho

    1998-06-01

    New matrix resins containing maleic anhydride and cycloolefin units for ArF excimer laser resist have been developed. Several series of these matrix resins having good dry-etching durability were prepared by free radical polymerization using AlBN as free radical initiator. All of the resists using the matrix resins revealed good coating uniformity and adhesion to silicon wafer, and were readily soluble in a variety of resist solvents such as MMP, EEP, PGMEA and EL. In preliminary 193 nm testing a resist formulated with the matrix resins sulfonium triflate as photoacid generator afforded positive images with 0.14 micrometers L/S resolution. In this paper, we will discuss the polymerization results and lithographic properties for 193 nm exposure tool.

  13. A comparative study of corneal incisions induced by diamond and steel knives and two ultraviolet radiations from an excimer laser.

    PubMed Central

    Marshall, J; Trokel, S; Rothery, S; Krueger, R R

    1986-01-01

    This paper reviews the potential role of excimer lasers in corneal surgery. The morphology of incisions induced by two wavelengths of excimer laser radiation, 193 nm and 248 nm, are compared with the morphology of incisions produced by diamond and steel knives. Analysis suggests that ablation induced by excimer laser results from highly localised photochemical reactions and that 193 nm is the optimal wavelength for surgery. The only significant complication of laser surgery is loss of endothelial cells when incisions are within 40 micron of Descemet's membrane. Images PMID:3013283

  14. Excimer laser ablation of the lens.

    PubMed

    Nanevicz, T M; Prince, M R; Gawande, A A; Puliafito, C A

    1986-12-01

    Ablation of the bovine crystalline lens was studied using radiation from an excimer laser at four ultraviolet wave lengths as follows: 193 nm (argon fluoride), 248 nm (krypton fluoride), 308 nm (xenon chloride), and 351 nm (xenon fluoride). The ablation process was quantitated by measuring mass ablated with an electronic balance, and characterized by examining ablation craters with scanning electron microscopy. The highest ablation rate was observed at 248 nm with lower rates at 193 and 308 nm. No ablation was observed at 351 nm. Scanning electron microscopy revealed the smoothest craters at 193 nm while at 248 nm there was vacuolization in the crater walls and greater disruption of surrounding tissue. The craters made at 308 nm did not have as smooth a contour as the 193-nm lesions. The spectral absorbance of the bovine lens was calculated at the wavelengths used for ablation and correlated with ablation rates and thresholds. High peak-power, pulsed ultraviolet laser radiation may have a role in surgical removal of the lens. PMID:3789982

  15. Development of high-power, 6 kHz, single-mode Ti:sapphire laser at 904 nm for generating 193 nm light

    NASA Astrophysics Data System (ADS)

    Tsuboi, Mizuki; Nakazato, Tomoharu; Onose, Takashi; Tanaka, Yuichi; Sarukura, Nobuhiko; Kakizaki, Kouji; Watanabe, Shuntaro

    2015-04-01

    A high power, 6 kHz, single-mode Ti:sapphire laser operating at 904 nm has been developed to produce a 193 nm light source. The output power was above 10 W with a bandwidth of 160 MHz. The Hänsch-Couillaud locking scheme was successfully applied to stabilize the frequency of the pulse laser. The thermal lens in the Ti:sapphire crystal having a focal length down to 10 mm along with strong astigmatism was compensated by distributing thermal load to three amplifiers with an even number of passes, resulting in a nearly diffraction limited beam. This Ti:sapphire laser contributed to the generation of 193 nm light with an output power above 200 mW.

  16. Corneal topography of excimer laser photorefractive keratectomy.

    PubMed

    Klyce, S D; Smolek, M K

    1993-01-01

    The application of the 193 nm excimer laser for keratorefractive surgery promises to deliver a higher degree of precision and predictability than traditional procedures such as radial keratotomy. The development and evaluation of keratorefractive surgery have benefited from the parallel advances made in the field of corneal topography analysis. We used the Computed Anatomy Topography Modeling System (TMS-1) to analyze a Louisiana State University (LSU) Eye Center series of patients who had photorefractive keratectomy for the treatment of myopia with the VISX Twenty/Twenty excimer laser system. The excimer ablations were characterized by a relatively uniform distribution of surface powers within the treated zone. In the few cases that exhibited marked refractive regression, corneal topography analysis showed correlative changes. With topographical analysis, centration of the ablations relative to the center of the pupil could be evaluated. Marked improvement in centration occurred in the patients of LSU Series IIB in which the procedure to locate the point on the cornea directly over the pupil's center during surgery was refined. Corneal topographical analysis provides objective measures of keratorefractive surgical results and is able to measure the precise tissue removal effect of excimer laser ablation without the uncertainties caused by measuring visual acuity alone. Our observations forecast the need for improved aids to center the laser ablations and for the development of a course of treatment to prevent post-ablation stromal remodeling. PMID:8450433

  17. Excimer Laser Etching

    SciTech Connect

    Boatner, Lynn A; Longmire, Hu Foster; Rouleau, Christopher M; Gray, Allison S

    2008-04-01

    Excimer laser radiation at a wavelength of = 248 nm represents a new etching method for the preparation of metallographic specimens. The method is shown to be particularly effective for enhancing the contrast between different phases in a multiphase metallographic specimen.

  18. Preliminary characterisation of new glass reference materials (GSA-1G, GSC-1G, GSD-1G and GSE-1G) by laser ablation-inductively coupled plasma-mass spectrometry using 193 nm, 213 nm and 266 nm wavelengths

    USGS Publications Warehouse

    Guillong, M.; Hametner, K.; Reusser, E.; Wilson, S.A.; Gunther, D.

    2005-01-01

    New glass reference materials GSA-1G, GSC-1G, GSD-1G and GSE-1G have been characterised using a prototype solid state laser ablation system capable of producing wavelengths of 193 nm, 213 nm and 266 nm. This system allowed comparison of the effects of different laser wavelengths under nearly identical ablation and ICP operating conditions. The wavelengths 213 nm and 266 nm were also used at higher energy densities to evaluate the influence of energy density on quantitative analysis. In addition, the glass reference materials were analysed using commercially available 266 nm Nd:YAG and 193 nm ArF excimer lasers. Laser ablation analysis was carried out using both single spot and scanning mode ablation. Using laser ablation ICP-MS, concentrations of fifty-eight elements were determined with external calibration to the NIST SRM 610 glass reference material. Instead of applying the more common internal standardisation procedure, the total concentration of all element oxide concentrations was normalised to 100%. Major element concentrations were compared with those determined by electron microprobe. In addition to NIST SRM 610 for external calibration, USGS BCR-2G was used as a more closely matrix-matched reference material in order to compare the effect of matrix-matched and non matrix-matched calibration on quantitative analysis. The results show that the various laser wavelengths and energy densities applied produced similar results, with the exception of scanning mode ablation at 266 nm without matrix-matched calibration where deviations up to 60% from the average were found. However, results acquired using a scanning mode with a matrix-matched calibration agreed with results obtained by spot analysis. The increased abundance of large particles produced when using a scanning ablation mode with NIST SRM 610, is responsible for elemental fractionation effects caused by incomplete vaporisation of large particles in the ICP.

  19. Excimer Laser Application For Cataract Surgery

    NASA Astrophysics Data System (ADS)

    Bath, Patricia E.; Mueller, Gerhard; Apple, David J.; Stolzenburg, Norbert M.

    1988-06-01

    The ablation threshold of bovine lenses was determined for excimer laser radiatiF at 308 nanreters. The ablation th5eshold for bovine lenses was approximately 0.6J/cm +/-0.1J/cm , for cortex and 1J/cm for nucleus. The threshold for bovine nucleus was higher than the threshold for cortex and difference was statistically significant at the 0.05 level. The relatively low ablation threshold for bovine lenses demonstrates the potential effectiveness of excimer laser radiation at 308 nm for cataract surgery. An experimental prototype has been developed and results of its application demonstrated. Further experiments to demonstrate safety for the retina and adjacent ocular structures are necessary because of the well known hazards of ultraviolet radiation. The potential of theleymir laser for keratorefractive surgery is currently under intensive investigation. In preliminary studies the ablation behavior of bovine lenses was investigated. The objective of this study was to quantify ablation rates as the first step in determining the specification for a laser system which would be practical in the clinical setting. Although excimer laser systems are available at 193 nm (ArF), 248 (KrF) and 351 (xeF) we selected 308 nm because of the availability of fiberoptics for the transmission of 308 nm as well as the known absorbance of human lenses in the 280 nm region.

  20. Excimer Lasers In Medicine

    NASA Astrophysics Data System (ADS)

    Tittel, Frank K.; Saidi, Iyad S.; Pettit, George H.; Wisoff, P. J.; Sauerbrey, Roland A.

    1989-06-01

    Excimer lasers emit light energy, short optical pulses at ultraviolet wavelengths, that results in a unique laser tissue interaction. This has led to an increasing number of studies into medical applications of these lasers in fields such as ophthalmology, urology, cardiology and neurology.

  1. Laser ablation of ceramic Al2O3 at 193 nm and 248 nm: The importance of single-photon ionization processes

    NASA Astrophysics Data System (ADS)

    Peláez, R. J.; Afonso, C. N.; Bator, M.; Lippert, T.

    2013-06-01

    The aim of this work is to demonstrate that single-photon photoionization processes make a significant difference in the expansion and temperature of the plasma produced by laser ablation of ceramic Al2O3 in vacuum as well as to show their consequences in the kinetic energy distribution of the species that eventually will impact on the film properties produced by pulsed laser deposition. This work compares results obtained by mass spectrometry and optical spectroscopy on the composition and features of the plasma produced by laser ablation at 193 nm and 248 nm, i.e., photon energies that are, respectively, above and below the ionization potential of Al, and for fluences between threshold for visible plasma and up to ≈2 times higher. The results show that the ionic composition and excitation of the plasma as well as the ion kinetic energies are much higher at 193 nm than at 248 nm and, in the latter case, the population of excited ions is even negligible. The comparison of Maxwell-Boltzmann temperature, electron temperatures, and densities of the plasmas produced with the two laser wavelengths suggests that the expansion of the plasma produced at 248 nm is dominated by a single population. Instead, the one produced at 193 nm is consistent with the existence of two populations of cold and hot species, the latter associated to Al+ ions that travel at the forefront and produced by single photon ionization as well as Al neutrals and double ionized ions produced by electron-ion impact. The results also show that the most energetic Al neutrals in the plasma produced at the two studied wavelengths are in the ground state.

  2. Excimer laser system Profile-500

    NASA Astrophysics Data System (ADS)

    Atejev, V. V.; Bukreyev, V. S.; Vartapetov, Serge K.; Semenov, A. D.; Sugrobov, V. A.; Turin, V. S.; Fedorov, Sergei N.

    1999-07-01

    The description of ophthalmological excimer laser system 'PROFILE-500' for photorefractive and physiotherapeutic keratectomy is presented. Excimer Laser Systems 'PROFILE- 500' are optical system that use ArF excimer lasers to perform photorefractive keratectomy or LASIK; surgical procedures used to correct myopia, hyperopia and astigmatism.

  3. Excimer laser machining of optical fiber taps

    NASA Astrophysics Data System (ADS)

    Coyle, Richard J.; Serafino, Anthony J.; Grimes, Gary J.; Bortolini, James R.

    1991-05-01

    Precision openings for construction of an optical backplane have been machined in an optical fiber using an excimer laser operating at a wavelength of 193 nm. The openings were made by imaging the laser beam onto the polymer fiber cladding with a telescope, then ablating the cladding with a sufficient number of pulses to expose the core. Circular openings measuring 250 and 625 microns and elliptical openings measuring 650 X 350 microns have been made in the cladding of a 1 mm polymer-clad silica fiber. Examination by scanning electron microscopy reveals that the best quality openings are obtained with either the smaller circular geometry or the elliptical geometry. For various reasons, elliptical openings, with the major axis oriented along the longitudinal axis of the fiber, appear more suitable for tap construction. Individual optical fiber taps have been constructed by attaching a tap fiber to a laser machined opening in a central fiber using an ultraviolet-curable acralate. Individual tap measurements were made on the elliptical and the 250 micron circular openings. In addition, a triple tap assembly was made using elliptical tap openings. These results indicate that the excimer laser machining technique may be applicable to the construction of a linear tapped bus for optical backplanes.

  4. Optimal design and fabrication method for antireflection coatings for P-polarized 193 nm laser beam at large angles of incidence (68°-74°).

    PubMed

    Jin, Jingcheng; Jin, Chunshui; Li, Chun; Deng, Wenyuan; Chang, Yanhe

    2013-09-01

    Most of the optical axes in modern systems are bent for optomechanical considerations. Antireflection (AR) coatings for polarized light at oblique incidence are widely used in optical surfaces like prisms or multiform lenses to suppress undesirable reflections. The optimal design and fabrication method for AR coatings with large-angle range (68°-74°) for a P-polarized 193 nm laser beam is discussed in detail. Experimental results showed that after coating, the reflection loss of a P-polarized laser beam at large angles of incidence on the optical surfaces is reduced dramatically, which could greatly improve the output efficiency of the optical components in the deep ultraviolet vacuum range. PMID:24323257

  5. Human excimer laser corneal surgery: preliminary report.

    PubMed Central

    L'Esperance, F A; Taylor, D M; Del Pero, R A; Roberts, A; Gigstad, J; Stokes, M T; Warner, J W; Telfair, W B; Martin, C A; Yoder, P R

    1988-01-01

    The first human trial utilizing the argon fluoride excimer laser at 193 nm to produce a superficial keratectomy in ten human eyes has been described with the histopathological evaluation of four eyes and the longer gross appearance of six eyes at intervals extending to 10 months post-excimer laser treatment. The process of laser superficial keratectomy has proved to be one of the promising areas of surgical intervention for reconstructive or refractive keratoplasty in the future. Intensive investigations need to be undertaken on the corneal wound healing process following laser ablation as well as the nature, and long-term stability of the corneal excisions or induced refractive corrections. It is essential that the optimal laser parameters be established for the various refractive corrections and other corneal surgical techniques, and that pathophysiologic and histopathologic changes that have been induced by the excimer laser-corneal tissue interaction in animals and humans be critically and extensively analyzed. Images FIGURE 1 FIGURE 19 A FIGURE 19 B FIGURE 20 A FIGURE 20 B FIGURE 21 A FIGURE 21 B FIGURE 22 A FIGURE 22 B FIGURE 23 FIGURE 24 FIGURE 25 FIGURE 26 FIGURE 27 FIGURE 28 FIGURE 29 A FIGURE 29 B FIGURE 29 C FIGURE 29 D FIGURE 30 A FIGURE 30 B FIGURE 31 A FIGURE 31 B FIGURE 32 FIGURE 33 FIGURE 34 FIGURE 35 FIGURE 36 FIGURE 37 A FIGURE 37 B FIGURE 37 C FIGURE 38 A FIGURE 38 B FIGURE 39 A FIGURE 39 B FIGURE 39 C FIGURE 40 A FIGURE 40 B PMID:2979049

  6. Excimer laser photoresist stripping

    NASA Astrophysics Data System (ADS)

    Genut, Menachem; Tehar-Zahav, Ofer; Iskevitch, Eli; Livshits, Boris

    1996-06-01

    A new method for stripping the most challenging photoresists on deep sub-micron technology semiconductor wafers has been developed. The method uses a combination of UV excimer laser ablation and reactive chemistry to strip the photoresist in a single dry process, eliminating the wet acids or solvents often used following ashing of high dose implantation (HDI) and reactive ion etching (RIE). The stripping process combines new removal mechanisms: chemical assisted UV excimer laser ablation/etching, laser induced chemical etching of side walls and residues, and enhanced combustion. During the laser pulses photolysis of the process gas occurs, UV laser radiation breaks the photoresist polymer chain bonds, and the photoresist (including foreign materials imbedded in it) is ablated. The combustion is ignited by the ablative impact of laser radiation and enhanced by the radicals formed during photo-thermal decomposition of the process gases. Following this process, the volatilized products and gases are evacuated. The optimum laser stripping conditions were developed to provide a wide process window for the most challenging stripping conditions, such as after HDI and RIE (metal, polysilicon), without causing damage to the wafer devices. A photoresist stripping system based on the described technology was designed and built. The system has been designated as the L-StripperTM and provides stripping time of 0.15 s/(micrometer cm2).

  7. The Excimer Laser: Its Impact on Science and Industry

    NASA Astrophysics Data System (ADS)

    Basting, Dirk

    2010-03-01

    After the laser was demonstrated in 1960, 15 years were required to develop a practical method for extending laser emission into the UV: the Excimer laser. This historical review will describe the challenges with the new medium and provide an insight into the technological achievements. In the transition from Science to Industry it will be shown how start-ups successfully commercialized laboratory prototypes. The pioneers in this rapidly expanding field will be identified and the influence of government-funded research as well as the role of venture capital will be discussed. In scientific applications, the fields of photochemistry and material research were particularly stimulated by the advent of a reliable UV light source. Numerous industrial applications and worldwide research in novel applications were fueled In the early and mid 80's by progress in excimer laser performance and technology. The discovery of ablative photocomposition of polymer materials by Srinivasan at IBM opened the door to a multitude of important excimer applications. Micromachining with extreme precision with an excimer laser enabled the success of the inkjet printer business. Biological materials such as the human cornea can also be ``machined'' at 193nm, as proposed in 1983 by Trokel and Srinivasan. This provided the foundation of a new medical technology and an industry relying on the excimer laser to perform refractive surgery to correct vision Today, by far the largest use of the excimer laser is in photolithography to manufacture semiconductor chips, an application discovered by Jain at IBM in the early 80's. Moore's law of shrinking the size of the structure to multiply the number of transistors on a chip could not have held true for so long without the deep UV excimer laser as a light source. The presentation will conclude with comments on the most recent applications and latest market trends.

  8. Refractive index change during exposure for 193-nm chemically amplified resists

    NASA Astrophysics Data System (ADS)

    Oh, Hye-Keun; Sohn, Young-Soo; Sung, Moon-Gyu; Lee, Young-Mi; Lee, Eun-Mi; Byun, Sung Hwan; An, Ilsin; Lee, Kun-Sang; Park, In-Ho

    1999-06-01

    Some of the important areas to be improved for lithography simulation are getting correct exposure parameters and determining the change of refractive index. It is known that the real and imaginary refractive indices are changed during exposure. We obtained these refractive index changes during exposure for 193 nm chemically amplified resists. The variations of the transmittance as well as the resist thickness were measured during ArF excimer laser exposure. We found that the refractive index change is directly related to the concentration of the photo acid generator and de-protected resin. It is important to know the exact values of acid concentration from the exposure parameters since a small difference in acid concentration magnifies the variation in the amplified de-protection during post exposure bake. We developed and used a method to extract Dill ABC exposure parameters for 193 nm chemically amplified resist from the refractive index change upon exposure.

  9. An anti-reflection coating for use with PMMA at 193 nm

    NASA Technical Reports Server (NTRS)

    Yen, Anthony; Smith, Henry I.; Schattenburg, M. L.; Taylor, Gary N.

    1992-01-01

    An antireflection coating (ARC) for use with poly(methyl methacrylate) (PMMA) resist for ArF excimer laser lithography (193 nm) was formulated. It consists of PMMA and a bis-azide, 4.4-prime-diazidodiphenyl sulfone (DDS) which crosslinks the film after deep UV (260 nm) irradiation and subsequent annealing. The reacted DDS then serves as the absorber for the 193 nm radiation and also prevents mixing of the ARC and PMMA during PMMA spin-coating and development. The effectiveness of the ARC was demonstrated by exposing, in PMMA, using achromatic holographic lithography, gratings of 100 nm period (about 50 nm linewidth) that are almost entirely free of an orthogonal standing wave.

  10. An anti-reflection coating for use with PMMA at 193 nm

    NASA Astrophysics Data System (ADS)

    Yen, Anthony; Smith, Henry I.; Schattenburg, M. L.; Taylor, Gary N.

    1992-02-01

    An antireflection coating (ARC) for use with poly(methyl methacrylate) (PMMA) resist for ArF excimer laser lithography (193 nm) was formulated. It consists of PMMA and a bis-azide, 4.4-prime-diazidodiphenyl sulfone (DDS) which crosslinks the film after deep UV (260 nm) irradiation and subsequent annealing. The reacted DDS then serves as the absorber for the 193 nm radiation and also prevents mixing of the ARC and PMMA during PMMA spin-coating and development. The effectiveness of the ARC was demonstrated by exposing, in PMMA, using achromatic holographic lithography, gratings of 100 nm period (about 50 nm linewidth) that are almost entirely free of an orthogonal standing wave.

  11. Production excimer laser equipment overview

    NASA Astrophysics Data System (ADS)

    Sercel, Jeffrey P.

    1993-04-01

    Excimer lasers were commercialized in the late 1970's. The laser community thought that by the early 1980's these UV lasers would enjoy a fruitful industrial market position. CO2 and solid state lasers required almost two decades to be fully accepted as industrial machine while the excimer laser was expected to be a fast learner benefiting from the learning curve of its big brothers. In retrospect, early excimer lasers had a bad reputation for being complicated, expensive and frequently out of commission. By the late 1980's a few excimer laser manufacturers had engineered the problems to acceptable levels for successful pilot lines and small scale manufacturing to begin. At this time, the real industrial learning curves began as engineers worked to refine many subsystems and support technologies. Today, excimer lasers are being used as true industrial lasers. They have a bright future with numerous and diverse market opportunities. This paper is an overview of the technologies proven to be successful in adapting modern excimer lasers to successful full production situations.

  12. Applications of the 308-nm excimer laser in dermatology

    NASA Astrophysics Data System (ADS)

    Farkas, A.; Kemeny, L.

    2006-05-01

    Excimer lasers contain a mixture of a noble inert gas and a halogen, which form excited dimers only in the activated state. High-energy current is used to produce these dimers, which have a very short lifetime, and after their fast dissociation they release the excitation energy through ultraviolet photons. The application of these lasers proved to be successful in medicine, including the field of ophthalmology, cardiology, angiology, dentistry, orthopaedics, and, in recent years, dermatology. For medical purposes, the 193-nm argon fluoride, the 248-nm krypton fluoride, the 351-nm xenon fluoride, and the 308-nm xenon chloride lasers are used. Recently, the 308-nm xenon chloride laser has gained much attention as a very effective treatment modality in dermatological disorders. It was successfully utilized in psoriasis; later, it proved to be useful in handling other lightsensitive skin disorders and even in the treatment of allergic rhinitis. This review summarizes the possible applications of this promising tool in dermatology.

  13. High power excimer laser micromachining

    NASA Astrophysics Data System (ADS)

    Herbst, Ludolf; Paetzel, Rainer

    2006-02-01

    Today's excimer lasers are well-established UV laser sources for a wide variety of micromachining applications. The excimer's high pulse energy and average power at short UV wavelengths make them ideal for ablation of various materials, e. g., polyimide, PMMA, copper, and diamond. Excimer micromachining technology, driven by the ever-shrinking feature sizes of micro-mechanical and micro-electronic devices, is used for making semiconductor packaging microvias, ink jet nozzle arrays, and medical devices. High-power excimer laser systems are capable of processing large areas with resolution down to several microns without using wet chemical processes. For instance, drilling precise tapered holes and reel-to-reel manufacturing of disposable sensors have proven to be very cost-effective manufacturing techniques for volume production. Specifically, the new industrial excimer laser-the LAMBDA SX 315C-easily meets the high demands of cost-effective production. The stabilized output power of 315 watts at 300 Hz (308 nm) and its outstanding long-term stability make this laser ideal for high-duty-cycle, high-throughput micromachining. In this paper, high-power excimer laser technology, products, applications, and beam delivery systems will be discussed.

  14. Wavelength conversion with excimer lasers

    SciTech Connect

    Booker, J.; Eichner, L.; Storz, R.H.; Bucksbaum, P.H.; Freeman, R.R.

    1983-01-01

    Harmonic generation was studied using a high powered, ultrashort pulse KrF excimer laser. Third, fifth, and seventh harmonic outputs were observed at 82.8 nm, 49.7 nm, and 35.5 nm. The nonlinear interaction took place at the intersection of the laser focus with a pulsed, supersonic gas jet expansion.

  15. Behavior of 157 nm excimer-laser-induced refractive index changes in silica

    SciTech Connect

    Smith, Charlene M.; Borrelli, Nicholas F.

    2006-09-15

    This study describes the observation of large induced refractive index changes produced by 157 nm excimer laser exposure in high-purity synthetic silica glasses. With 157 nm exposure, large induced changes are observed within a few hundred thousand pulses of exposure. Similar to 193 nm exposures, exposure with polarized 157 nm light yields polarization-induced birefringence (PIB). However, the 157 nm exposure also exhibits a behavior not observed with 193 nm exposures; namely, the initial response of the glass is a decrease in refractive index, followed by an increase with continued exposure. An explanation of the behaviors for both wavelength results is proposed where the induced refractive index is considered to arise from two different concurrent phenomena. One produces a decreased refractive index and also accounts for the PIB. The other, which accounts for the increased refractive index, is associated with an isotropic laser-induced volume change.

  16. Vacuum barrier for excimer lasers

    DOEpatents

    Shurter, Roger P.

    1992-01-01

    A barrier for separating the vacuum area of a diode from the pressurized gas area of an excimer laser. The barrier is a composite material comprising layers of a metal such as copper, along with layers of polyimide, and a matrix of graphite fiber yarns impregnated with epoxy. The barrier is stronger than conventional foil barriers, and allows greater electron throughput.

  17. Vacuum barrier for excimer lasers

    DOEpatents

    Shurter, R.P.

    1992-09-15

    A barrier for separating the vacuum area of a diode from the pressurized gas area of an excimer laser. The barrier is a composite material comprising layers of a metal such as copper, along with layers of polyimide, and a matrix of graphite fiber yarns impregnated with epoxy. The barrier is stronger than conventional foil barriers, and allows greater electron throughput. 3 figs.

  18. Absorption of 308-nm excimer laser radiation by balanced salt solution, sodium hyaluronate, and human cadaver eyes

    SciTech Connect

    Keates, R.H.; Bloom, R.T.; Schneider, R.T.; Ren, Q.; Sohl, J.; Viscardi, J.J. )

    1990-11-01

    Absorption of the excimer laser radiations of 193-nm argon fluorine and 308-nm xenon chloride in balanced salt solution, sodium hyaluronate, and human cadaver eyes was measured. The absorption of these materials as considerably different for the two wavelengths; we found that 308-nm light experienced much less absorption than the 193-nm light. The extinction coefficient (k) for 308 nm was k = 0.19/cm for balanced salt solution and k = 0.22/cm for sodium hyaluronate. In contrast to this, the extinction coefficient for 193 nm was k = 140/cm for balanced salt solution and k = 540/cm for sodium hyaluronate. Two 1-day-old human phakic cadaver eyes showed complete absorption with both wavelengths. Using aphakic eyes, incomplete absorption was noted at the posterior pole with 308 nm and complete absorption was noted with 193 nm. The extinction in the anterior part of aphakic eyes (the first 6 mm) was 4.2/cm for 308 nm, meaning that the intensity of the light is reduced by a factor of 10 after traveling the first 5.5 mm. However, we observed that the material in the eye fluoresces, meaning the 308 nm is transformed into other (longer) wavelengths that travel through the total eye with minimal absorption. Conclusions drawn from this experiment are that the use of the 308-nm wavelength may have undesirable side effects, while the use of the 193-nm wavelength should be consistent with ophthalmic use on both the cornea and the lens.

  19. Semiconductor processing with excimer lasers

    SciTech Connect

    Young, R.T.; Narayan, J.; Christie, W.H.; van der Leeden, G.A.; Rothe, D.E.; Cheng, L.J.

    1983-01-01

    The advantages of pulsed excimer lasers for semiconductor processing are reviewed. Extensive comparisons of the quality of annealing of ion-implanted Si obtained with XeCl and ruby lasers have been made. The results indicate that irrespective of the large differences in the optical properties of Si at uv and visible wavelengths, the efficiency of usage of the incident energy for annealing is comparable for the two lasers. However, because of the excellent optical beam quality, the XeCl laser can provide superior control of the surface melting and the resulting junction depth. Furthermore, the concentrations of electrically active point defects in the XeCl laser annealed region are 2 to 3 orders of magnitude lower than that obtained from ruby or Nd:YAG lasers. All these results seem to suggest that XeCl lasers should be suitable for fabricating not only solar cells but also the more advanced device structures required for VLSI or VHSIC applications.

  20. Excimer laser in arthroscopic surgery

    NASA Astrophysics Data System (ADS)

    Koort, Hans J.

    1991-05-01

    The development of efficient high-power lasersystems for use in surgery, especially in arthroscopic fields, leads to a new push for all endoscopic techniques. Both techniques, laser and endoscope, complete each other in an ideal way and allow applications which could not be reached with conventional techniques. One of the newer laser types is the excimer laser, which will be a good choice for surface treatment because of its very considerate interaction with tissue. One example is the ablation or smoothing of articular cartilage and meniscal shaving in orthopaedics. On the other hand, the power of this laser system is high enough to cut tissue, for instance in the lateral release, and offers therefore an alternative to the mechanical and electrical instruments. All lasers can only work fine with effective delivery systems. Sometimes there is only a single fiber, which becomes very stiff at diameters of more than 800 micrometers . This fiber often allows only the tangential treatment of tissue, most of the laser power is lost in the background. New fiber systems with many, sometimes hundreds of very thin single fibers, could offer a solution. Special handpieces and fibersystems offer distinct advantages in small joint arthroscopy, especially those for use with excimer lasers will be discussed.

  1. Laser mass spectrometric detection of AlH molecules as collision-free excimer laser photoproducts from aluminum alkyls

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Stuke, M.

    1988-08-01

    Aluminum hydride molecules AlH are detected and identified by tunable dye-laser mass spectroscopy as collision-free UV excimer laser photoproducts of the Al alkyls TEA (triethylaluminum (C 2H 5) 3Al) and TIBA (triisobutylaluminum ( i-C 4H 9) 3Al) at 248 and 193 nm. An internal energy distribution analysis of the photoproducts shows only minor vibrational excitation of ν″ = 1 and a Boltzmann-type rotational energy distribution with a temperature of about 0.03 eV, compared to the incoming photon energy of 5.0 or 6.42 eV.

  2. Alternatives to chemical amplification for 193nm lithography

    NASA Astrophysics Data System (ADS)

    Baylav, Burak; Zhao, Meng; Yin, Ran; Xie, Peng; Scholz, Chris; Smith, Bruce; Smith, Thomas; Zimmerman, Paul

    2010-04-01

    Research has been conducted to develop alternatives to chemically amplified 193 nm photoresist materials that will be able to achieve the requirements associated with sub-32 nm device technology. New as well as older photoresist design concepts for non-chemically amplified 193 nm photoresists that have the potential to enable improvements in line edge roughness while maintaining adequate sensitivity, base solubility, and dry etch resistance for high volume manufacturing are being explored. The particular platforms that have been explored in this work include dissolution inhibitor photoresist systems, chain scissioning polymers, and photoresist systems based on polymers incorporating formyloxyphenyl functional groups. In studies of two-component acidic polymer/dissolution inhibitor systems, it was found that compositions using ortho-nitrobenzyl cholate (NBC) as the dissolution inhibitor and poly norbornene hexafluoro alcohol (PNBHFA) as the base resin are capable of printing 90 nm dense line/space patterns upon exposure to a 193 nm laser. Studies of chain scission enhancement in methylmethacrylate copolymers showed that incorporating small amounts of absorptive a-cleavage monomers significantly enhanced sensitivity with an acceptable increase in absorbance at 193 nm. Specifically, it was found that adding 3 mol% of α-methyl styrene (α-MS) reduced the dose to clear of PMMA-based resist from 1400 mJ/cm2 to 420 mJ/cm2. Preliminary data are also presented on a direct photoreactive design concept based on the photo-Fries reaction of formyloxyphenyl functional groups in acrylic copolymers.

  3. Excimer laser chemical problems

    SciTech Connect

    Tennant, R.; Peterson, N.

    1982-01-01

    Techniques need to be developed to maintain XeF and XeCl laser performance over long periods of time without degradation resulting from chemical processes occurring within the laser. The dominant chemical issues include optical damage, corrosions of laser materials, gas contamination, and control of halogen concentration. Each of these issues are discussed and summarized. The methods of minimizing or controlling the chemical processes involved are presented.

  4. Excimer laser superficial keratectomy for proud nebulae in keratoconus.

    PubMed Central

    Moodaley, L; Liu, C; Woodward, E G; O'Brart, D; Muir, M K; Buckley, R

    1994-01-01

    Contact lens intolerance in keratoconus may be due to the formation of a proud nebula at or near the apex of the cone. Excimer laser superficial keratectomy was performed as an outpatients with proud nebulae as treatment patients with proud nebulae as treatment for their contact lens intolerance. The mean period of contact lens wear before the development of intolerance was 13.4 years (range 2 to 27 years). Following the development of intolerance, three patients abandoned contact lens wear in the affected eye while the remainder experienced a reduction in comfortable wearing time (mean = 3.75 hours; range: 0-14 hours). All patients had good potential Snellen visual acuity with a contact lens of 6/9 (nine eyes) and 6/12 (one eye). The proud nebulae were directly ablated with a 193 nm ArF excimer laser using a 1 mm diameter beam. Between 100-150 pulses were sufficient to ablate the raised area. Patients experienced no pain during the procedure and reported minimal discomfort postoperatively. In all cases flattening of the proud nebulae was achieved. Seven patients were able to resume regular contact lens wear (mean wearing time = 10.17 hours; range 8 to 16 hours). In three patients, resumption of contact lens wear was unsuccessful because of cone steepness. All patients achieved postoperative Snellen visual acuity of 6/12 or better with a contact lens. Four patients experienced a loss of one line in Snellen acuity. The mean follow up period was 8.3 months (range 2 to 17 months). Excimer laser superficial keratectomy is a useful technique for the treatment of contact lens intolerance caused by proud nebulae in patients with keratoconus. Penetrating keratoplasty is thus avoided. Images PMID:8060928

  5. Excimer laser superficial keratectomy for proud nebulae in keratoconus.

    PubMed

    Moodaley, L; Liu, C; Woodward, E G; O'Brart, D; Muir, M K; Buckley, R

    1994-06-01

    Contact lens intolerance in keratoconus may be due to the formation of a proud nebula at or near the apex of the cone. Excimer laser superficial keratectomy was performed as an outpatients with proud nebulae as treatment patients with proud nebulae as treatment for their contact lens intolerance. The mean period of contact lens wear before the development of intolerance was 13.4 years (range 2 to 27 years). Following the development of intolerance, three patients abandoned contact lens wear in the affected eye while the remainder experienced a reduction in comfortable wearing time (mean = 3.75 hours; range: 0-14 hours). All patients had good potential Snellen visual acuity with a contact lens of 6/9 (nine eyes) and 6/12 (one eye). The proud nebulae were directly ablated with a 193 nm ArF excimer laser using a 1 mm diameter beam. Between 100-150 pulses were sufficient to ablate the raised area. Patients experienced no pain during the procedure and reported minimal discomfort postoperatively. In all cases flattening of the proud nebulae was achieved. Seven patients were able to resume regular contact lens wear (mean wearing time = 10.17 hours; range 8 to 16 hours). In three patients, resumption of contact lens wear was unsuccessful because of cone steepness. All patients achieved postoperative Snellen visual acuity of 6/12 or better with a contact lens. Four patients experienced a loss of one line in Snellen acuity. The mean follow up period was 8.3 months (range 2 to 17 months). Excimer laser superficial keratectomy is a useful technique for the treatment of contact lens intolerance caused by proud nebulae in patients with keratoconus. Penetrating keratoplasty is thus avoided. PMID:8060928

  6. Excimer laser ablation of ferrites

    NASA Astrophysics Data System (ADS)

    Tam, A. C.; Leung, W. P.; Krajnovich, D.

    1991-02-01

    Laser etching of ferrites was previously done by scanning a focused continuous-wave laser beam on a ferrite sample in a chemical environment. We study the phenomenon of photo-ablation of Ni-Zn or Mn-Zn ferrites by pulsed 248-nm KrF excimer laser irradiation. A transfer lens system is used to project a grating pattern of a mask irradiated by the pulsed KrF laser onto the ferrite sample. The threshold fluence for ablation at the ferrite surface is about 0.3 J/cm2. A typical fluence of 1 J/cm2 is used. The etched grooves produced are typically 20-50 μm wide, with depths achieved as deep as 70 μm . Groove straightness is good as long as a sharp image is projected onto the sample surface. The wall angle is steeper than 60 degrees. Scanning electron microscopy of the etched area shows a ``glassy'' skin with extensive microcracks and solidified droplets being ejected that is frozen in action. We found that this skin can be entirely removed by ultrasonic cleaning. A fairly efficient etching rate of about 10 nm/pulse for a patterned area of about 2 mm×2 mm is obtained at a fluence of 1 J/cm2. This study shows that projection excimer laser ablation is useful for micromachining of ferrite ceramics, and indicates that a hydrodynamic sputtering mechanism involving droplet emission is a cause of material removal.

  7. Detection of lead in soil with excimer laser fragmentation fluorescence spectroscopy (ELFFS)

    SciTech Connect

    Choi, J.H.; Damm, C.J.; O'Donovan, N.J.; Sawyer, R.F.; Koshland, C.P.; Lucas, D.

    2004-03-01

    Excimer laser fragmentation fluorescence spectroscopy (ELFFS) is used to monitor lead in soil sample and investigate laser-solid interactions. Pure lead nitrate salt and soil doped with lead nitrate are photolyzed with 193 nm light from an ArF excimer at fluences from 0.4 to 4 J/cm{sup 2}. Lead emission is observed at 357.2, 364.0, 368.3, 373.9 and 405.8 nm. Time-resolved data show the decay time of the lead emission at 405.8 nm grows with increasing fluence, and a plasma is formed above fluences of 2 J/cm{sup 2}, where a strong continuum emission interferes with the analyte signal. Fluences below this threshold allow us to achieve a detection limit of approximately 200 ppm in soil.

  8. Excimer laser sclerostomy: the in vitro development of a modified open mask delivery system.

    PubMed

    Allan, B D; van Saarloos, P P; Russo, A V; Cooper, R L; Constable, I J

    1993-01-01

    The argon fluoride (ArF) excimer laser at 193 nm ablates the ocular tissues with a new order of precision and virtually no adjacent damage. A glaucoma filtration operation has been designed in which small-bore sclerostomies are created using the ArF excimer laser delivered through an open mask. The mask plicates the conjunctiva at the limbus prior to ablation. Removing the mask at the end of the procedure allows the conjunctiva to relax back to its original position, separating the conjunctival and scleral wounds. Formal conjunctival dissection is thus avoided. Feasibility studies in cadaver pig eyes, using a fluence per pulse of 400 mJ/cm2 and a pulse repetition rate of 20 Hz, indicate that sclerostomies of 300 microns diameter can be reliably formed if an en-face air jet is built into the mask to raise the pressure in the target area, preventing aqueous flooding. PMID:8325423

  9. Negative-tone 193-nm resists

    NASA Astrophysics Data System (ADS)

    Cho, Sungseo; Vander Heyden, Anthony; Byers, Jeff D.; Willson, C. Grant

    2000-06-01

    A great deal of progress has been made in the design of single layer positive tone resists for 193 nm lithography. Commercial samples of such materials are now available from many vendors. The patterning of certain levels of devices profits from the use of negative tone resists. There have been several reports of work directed toward the design of negative tones resists for 193 nm exposure but, none have performed as well as the positive tone systems. Polymers with alicyclic structures in the backbone have emerged as excellent platforms from which to design positive tone resists for 193 nm exposure. We now report the adaptation of this class of polymers to the design of high performance negative tone 193 nm resists. New systems have been prepared that are based on a polarity switch mechanism for modulation of the dissolution rate. The systems are based on a polar, alicyclic polymer backbone that includes a monomer bearing a glycol pendant group that undergoes the acid catalyzed pinacol rearrangement upon exposure and bake to produce the corresponding less polar ketone. This monomer was copolymerized with maleic anhydride and a norbornene bearing a bis-trifluoromethylcarbinol. The rearrangement of the copolymer was monitored by FT-IR as a function of temperature. The synthesis of the norbornene monomers will be presented together with characterization of copolymers of these monomers with maleic anhydride. The lithographic performance of the new resist system will also be presented.

  10. Excimer lasers drive large-area microprocessing

    NASA Astrophysics Data System (ADS)

    Delmdahl, Ralph; Tapié, Jean-Luc

    2012-09-01

    Excimer lasers emitting in the UV to far UV region are by nature the laser sources enabling the highest optical resolution and strongest material-photon interaction. At the same time, excimer lasers deliver unmatched UV pulse energies and output powers up to the kilowatt range. Thus, they are the key to fast and effective large area processing of smallest structures with micron precision. As a consequence, excimer lasers are the UV technology of choice when it comes to high-performance microstructuring with unsurpassed quality and process repeatability in applications such as drilling advanced ink jet nozzles or patterning biomedical sensor structures.

  11. 308nm excimer laser in dermatology.

    PubMed

    Mehraban, Shadi; Feily, Amir

    2014-01-01

    308nm xenon-chloride excimer laser, a novel mode of phototherapy, is an ultraviolet B radiation system consisting of a noble gas and halide. The aim of this systematic review was to investigate the literature and summarize all the experiments, clinical trials and case reports on 308-nm excimer laser in dermatological disorders. 308-nm excimer laser has currently a verified efficacy in treating skin conditions such as vitiligo, psoriasis, atopic dermatitis, alopecia areata, allergic rhinitis, folliculitis, granuloma annulare, lichen planus, mycosis fungoides, palmoplantar pustulosis, pityriasis alba, CD30+ lympho proliferative disorder, leukoderma, prurigo nodularis, localized scleroderma and genital lichen sclerosus. Although the 308-nm excimer laser appears to act as a promising treatment modality in dermatology, further large-scale studies should be undertaken in order to fully affirm its safety profile considering the potential risk, however minimal, of malignancy, it may impose. PMID:25606333

  12. Granuloma Annulare Treated with Excimer Laser

    PubMed Central

    Ragi, Jennifer; Milgraum, Sandy

    2012-01-01

    Objective: To review the current therapy for granuloma annulare and report a case of refractory generalized granuloma annulare successfully treated with excimer laser. A discussion about the characteristics of excimer laser and the mechanism of its effectiveness is presented. Design: Patient case report and literature review. Setting: Outpatient dermatology practice. Participants: A 73-year-old woman suffering from generalized granuloma annulare for more than 40 years. Measurements: Change in clinical appearance of lesions. Results: Use of excimer laser therapy resulted in prompt and complete resolution in treated areas with no residual skin changes or side effects. Conclusion: Excimer laser therapy is a powerful treatment modality with minimal side effects for patients with granuloma annulare. Further study is necessary to elucidate optimal dosing, long-term efficacy, and safety profile. PMID:23198013

  13. AlGaAs growth by OMCVD using an excimer laser

    SciTech Connect

    Warner, J.D.; Wilt, D.M.; Pouch, J.J.; Aron, P.R.

    1986-12-01

    AlGaAs has been grown on GaAs by laser assisted OMCVD using an excimer laser, wavelength 193 nm, and a Cambridge OMCVD reactor. Films were grown at temperatures of 450 and 500 C with the laser beam parallel to the surface and impinging onto the surface at 15 deg from parallel. The samples were heated by RF coils while the laser beam was perpendicular to the gas flow. Typical gas flow parameters are 12 slm of H/sub 2/, 15 sccm of Ga(CH3)3, 13 sccm of Al(CH3)3, and a pressure of 250 mbar. The initial energy density of the beam at the surface was 40 mJ/sq cm, the pulse rate was 20 pps, and the growth time was 7 min. The films were analyzed by Auger electron spectroscopy for the aluminum concentration and by TEM for the surface morphology.

  14. AlGaAs growth by OMCVD using an excimer laser

    NASA Technical Reports Server (NTRS)

    Warner, Joseph D.; Wilt, David M.; Pouch, John J.; Aron, Paul R.

    1986-01-01

    AlGaAs has been grown on GaAs by laser assisted OMCVD using an excimer laser, wavelength 193 nm, and a Cambridge OMCVD reactor. Films were grown at temperatures of 450 and 500 C with the laser beam parallel to the surface and impinging onto the surface at 15 deg from parallel. The samples were heated by RF coils while the laser beam was perpendicular to the gas flow. Typical gas flow parameters are 12 slm of H2, 15 sccm of Ga(CH3)3, 13 sccm of Al(CH3)3, and a pressure of 250 mbar. The initial energy density of the beam at the surface was 40 mJ/sq cm, the pulse rate was 20 pps, and the growth time was 7 min. The films were analyzed by Auger electron spectroscopy for the aluminum concentration and by TEM for the surface morphology.

  15. Colouring fabrics with excimer lasers to simulate encoded images: the case of the Shroud of Turin

    NASA Astrophysics Data System (ADS)

    Di Lazzaro, P.; Baldacchini, G.; Fanti, G.; Murra, D.; Santoni, A.

    2008-10-01

    The faint body image embedded into the Turin Shroud has not yet explained by traditional science. We present experimental results of excimer laser irradiation (wavelengths 308 nm and 193 nm) of a raw linen fabric and of a linen cloth, seeking for a possible mechanism of image formation. The permanent coloration of both linens is a threshold effect on the laser beam intensity and it can be achieved only in a surprisingly narrow range of irradiation parameters: the shorter the wavelength, the narrower the range. We also obtained the first direct evidence of latent images impressed on linen that appear in a relatively long period (one year) after a laser irradiation that at first did not generate a clear image. The results are compared to the characteristics of the Turin Shroud, commenting the possibility that a burst of directional ultraviolet radiation may have played a role in the formation of the Shroud image.

  16. Optical extension at the 193-nm wavelength

    NASA Astrophysics Data System (ADS)

    Zandbergen, Peter; McCallum, Martin; Amblard, Gilles R.; Domke, Wolf-Dieter; Smith, Bruce W.; Zavyalova, Lena; Petersen, John S.

    1999-07-01

    Lithography at 193nm is the first optical lithography technique that will be introduced for manufacturing of technology levels. where the required dimensions are smaller than the actual wavelength. This paper explores several techniques to extend 193nm to low k1 lithography. Most attention is given to binary mask solution in at 130nm dimensions, where k1 is 0.4. Various strong and Gaussian quadrupole illuminators were designed, manufactured and tested for this application. Strong quadrupoles show that largest DOF improvements. The drawback however, is that these strong quadrupoles are very duty cycle and dimensions specific, resulting in large proximity biases between different duty cycles. Due to their design, Gaussian quadrupoles sample much wider frequency ranges, resulting in less duty cycles specific DOF improvements and less proximity basis. At sub-130nm dimensions, strong phase shift masks provide significant latitude improvements, when compared to binary masks with quadrupole illumination. However, differences in dose to size for different duty cycles were up to 25 percent. For definition of contact holes, linewidth biasing through silylation, a key feature of the CARL bi-layer resist approach, demonstrated significant DOF latitude improvements compared to SLR at 140nm and 160nm contact holes.

  17. Modulation of corneal wound healing after excimer laser keratomileusis using topical mitomycin C and steroids

    SciTech Connect

    Talamo, J.H.; Gollamudi, S.; Green, W.R.; De La Cruz, Z.; Filatov, V.; Stark, W.J. )

    1991-08-01

    A 193-nm excimer laser system was used to create deep stromal ablations in seven New Zealand white rabbits and shallow ablations in three. Eyes were randomized for treatment with topical mitomycin C, steroids, and erythromycin; topical steroids and erythromycin; or topical erythromycin only. All treatment regimens were instituted twice daily for 14 days. All eyes reepithelialized normally within 3 to 5 days. During 10 weeks of follow-up, all eyes developed moderate reticular subepithelial haze without significant differences among treatment groups. Results of light, fluorescence, and electron microscopic examination showed anterior stromal scarring and markedly reduced new subepithelial collagen formation in the group treated with mitomycin C, corticosteroids, and erythromycin. Focal abnormalities of Descemet's membrane and endothelial abnormalities were present in all treatment groups. Combination therapy with topical steroids, mitomycin C, and erythromycin to control the corneal wound healing response after refractive laser surgery appears promising and warrants further study.

  18. Excimer laser texturing of natural composite polymer surfaces for studying cell-to-substrate specific response

    NASA Astrophysics Data System (ADS)

    Dinca, V.; Alloncle, P.; Delaporte, P.; Ion, V.; Rusen, L.; Filipescu, M.; Mustaciosu, C.; Luculescu, C.; Dinescu, M.

    2015-10-01

    Surface modifications of biocompatible materials are among the main factors used for enhancing and promoting specific cellular activities (e.g. spreading, adhesion, migration, and differentiation) for various types of medical applications such as implants, microfluidic devices, or tissue engineering scaffolds. In this work an excimer laser at 193 nm was used to fabricate chitosan-collagen roughness gradients. The roughness gradients were obtained in one step by applying single laser pulses and sample tilting. Fourier transform infrared spectroscopy measurements, atomic force microscopy (AFM), scanning electron microscopy (SEM), and spectro-ellipsometry (SE) were used for sample characterization. The goal is to determine the optimal morpho-chemical characteristics of these structures for in vitro tailoring of protein adsorption and cell behavior. The response induced by the roughness gradient onto various cell lines (i.e. L 929 fibroblasts, HEP G2 hepatocytes, OLN 93 oligodendrocytes, M63 osteoblasts) and bovine serum albumin (BSA) protein absorption was investigated.

  19. Application Of The Excimer Laser To Area Recontouring Of The Cornea

    NASA Astrophysics Data System (ADS)

    Yoder, Paul R.; Telfair, William B.; Warner, John W.; Martin, Clifford A.; L'Esperance, Francis A.

    1989-04-01

    Excimer lasers operating at 193 nm are being used experimentally in a special type of materials processing wherein the central portion of the anterior surface of the human cornea is selectively ablated so as to change its refractive power and, hopefully, improve impaired vision. Research to date has demonstrated recontouring as a potential means for reducing myopia and hyperopia of cadaver eyes while studies of ablations on the corneas of living monkeys and of blind human volunteers show promise of prompt and successful healing. The procedure has also shown merit in removing superficial scars from the corneal surface. In this paper, we describe the electro-optical system used to deliver the UV laser beam in these experiments and report some preliminary results of the ablation studies.

  20. Binary 193nm photomasks aging phenomenon study

    NASA Astrophysics Data System (ADS)

    Dufaye, Félix; Sartelli, Luca; Pogliani, Carlo; Gough, Stuart; Sundermann, Frank; Miyashita, Hiroyuki; Hidenori, Yoshioka; Charras, Nathalie; Brochard, Christophe; Thivolle, Nicolas

    2011-05-01

    193nm binary photomasks are still used in the semiconductor industry for the lithography of some critical layers for the nodes 90nm and 65nm, with high volumes and over long period. These 193nm binary masks seem to be well-known but recent studies have shown surprising degrading effects, like Electric Field induced chromium Migration (EFM) [1] or chromium migration [2] [3] . Phase shift Masks (PSM) or Opaque MoSi On Glass (OMOG) might not be concerned by these effects [4] [6] under certain conditions. In this paper, we will focus our study on two layers gate and metal lines. We will detail the effects of mask aging, with SEM top view pictures revealing a degraded chromium edge profile and TEM chemical analyses demonstrating the growth of a chromium oxide on the sidewall. SEMCD measurements after volume production indicated a modified CD with respect to initial CD data after manufacture. A regression analysis of these CD measurements shows a radial effect, a die effect and an isolated-dense effect. Mask cleaning effectiveness has also been investigated, with sulphate or ozone cleans, to recover the mask quality in terms of CD. In complement, wafer intrafield CD measurements have been performed on the most sensitive structure to monitor the evolution of the aging effect on mask CD uniformity. Mask CD drift have been correlated with exposure dose drift and isolated-dense bias CD drift on wafers. In the end, we will try to propose a physical explanation of this aging phenomenon and a solution to prevent from it occurring.

  1. 308-nm excimer laser in endodontics

    NASA Astrophysics Data System (ADS)

    Liesenhoff, Tim

    1992-06-01

    Root canal preparation was performed on 20 extracted human teeth. After opening the coronal pulp, the root canals were prepared by 308 nm excimer laser only. All root canals were investigated under SEM after separation in the axial direction. By sagittal separation of the mandibles of freshly slaughtered cows, it was possible to get access to the tissues and irradiate under optical control. Under irradiation of excimer laser light, tissue starts to fluoresce. It was possible to demonstrate that each tissue (dentin, enamel, bone, pulpal, and connective tissue) has a characteristic spectral pattern. The SEM analyses showed that it is well possible to prepare root canals safely. All organic soft tissue has been removed by excimer laser irradiation. There was no case of via falsa. The simultaneous spectroscopic identification of the irradiated tissue provides a safe protection from overinstrumentation. First clinical trials on 20 patients suffering of chronical apical parodontitis have been carried out successfully.

  2. Custom specific fabrication of integrated optical devices by excimer laser ablation of polymers

    NASA Astrophysics Data System (ADS)

    Klotzbuecher, Thomas; Popp, Martin; Braune, Torsten; Haase, Jens; Gaudron, Anne; Smaglinski, Ingo; Paatzsch, Thomas; Bauer, Hans-Dieter; Ehrfeld, Wolfgang

    2000-06-01

    Excimer laser ablation was used for direct writing of multimode waveguide structures with passive fiber alignment grooves in polymers. First, integrated optical multimode components were simulated by the method of beam propagation to optimize the optical performance of the design. Then the CNC codes for laser machining were created directly from the corresponding CAD data. ArF Excimer laser radiation of wavelength (lambda) equals 193 nm was used for ablation of adjacent grooves with a cross sectional area of 50 X 50 micrometers 2 and lengths in the order of several mm. The laser-written grooves were filled with a liquid pre-polymer which after UV-curing served as the waveguiding structures. The smoothest surfaces during laser ablation were achieved by applying several ablation scans with reduced material removal rates but higher feedrates. Debris formation, also influencing the surface roughness, was suppressed or minimized by making use of capable polymers. With the method of laser ablation linear waveguides of length 1 equals 10 mm with insertion losses Li in the rang of 1.3 to 1.9 dB have been realized for (lambda) equals 1310 nm, depending on the polymer used. By means of 1 X 2-splitters, 4 X 4 as well as 4 X 16 starcouplers it was shown that laser ablation is a well suited tool for rapid prototyping of integrated optical multimode elements.

  3. Valacyclovir for the prevention of recurrent herpes simplex virus eye disease after excimer laser photokeratectomy.

    PubMed Central

    Asbell, P A

    2000-01-01

    PURPOSE: A variety of factors have been reported as inducing the reactivation of latent herpes simplex virus (HSV), among them stress, trauma, and UV radiation. Excimer laser photorefractive keratectomy (PRK) is a surgical procedure utilizing a 193 nm ultraviolet light to alter the curvature of the cornea and hence correct vision. Reactivation of ocular herpes simplex keratitis following such excimer laser PRK has been reported. All published cases of HSV reactivation following excimer laser treatment in humans are reviewed. The present study evaluates whether stress, trauma of the corneal de-epithelialization prior to the laser, or the excimer laser treatment itself to the stromal bed induces this ocular reactivation of the latent HSV, and whether a systemic antiviral agent, valacyclovir, would prevent such laser PRK-induced reactivation of the HSV. METHODS: Forty-three normal 1.5- to 2.5-kg New Zealand white rabbits were infected on the surface of the cornea with HSV-1, strain RE. The animals were monitored until resolution, and then all animals were divided into 5 treatment groups: (1) de-epithelialization only, intraperitoneal (i.p.) saline for 14 days; (2) de-epithelialization plus laser, i.p. saline for 14 days; (3) de-epithelialization plus laser, valacyclovir 50 mg/kg per day i.p. for 14 days; (4) de-epithelialization plus laser, valacyclovir 100 mg/kg per day i.p. for 14 days; (5) de-epithelialization plus laser, valacyclovir 150 mg/kg per day i.p. for 14 days. Animals were evaluated in a masked fashion by clinical examination biweekly and viral cultures biweekly through day 28. RESULTS: The reactivation rates were as follows: group 1, 0%; group 2, 67%; group 3, 50%; group 4, 17%; and group 5, 0%. Viral titers were negative in animals that had no reactivation but persistently positive in those that had reactivation (day 6 through day 28). CONCLUSIONS: Excimer laser (193 nm) treatment can trigger reactivation of ocular herpes disease (67%) and viral

  4. Percutaneous angioscopy after excimer laser angioplasty

    NASA Astrophysics Data System (ADS)

    Nakamura, Fumitaka; Kvasnicka, Jan; Geschwind, Herbert J.; Uchida, Yasumi

    1992-08-01

    Angioscopy has proved to provide more detailed information on lesion morphology before and after interventional procedures than angiography. Therefore, to evaluate the effects of laser angioplasty, angioscopy was performed in five patients with peripheral or coronary vascular disease who underwent excimer laser angioplasty. The excimer laser was operated at 308 nm, 135 nsec, 25 Hz, and 40 - 60 mJ/mm2 and was coupled into multifiber wire-guided catheters of 1.4 to 2.0 mm diameter for coronary lesions and 2.2 mm for peripheral lesions. There were three coronary (one left anterior descending, one circumflex, one right coronary artery) and two peripheral (one common iliac artery, one superficial femoral artery) lesions. Angioscopy was successfully performed before and after laser ablation without any complications in all five lesions. The characteristics of angioscopic findings after excimer laser angioplasty consisted of flaps, fractures of plaques, and abundant tissue remnants. There was no apparent thermal injury. Recanalized channels were small and irregular. These results indicate that (1) angioscopy is effective and safe for evaluation of lesion morphology after laser angioplasty, (2) laser ablation does not result in thermal injury, and (3) irregular channels after recanalization and abundant tissue remnants may explain the suboptimal results after laser angioplasty.

  5. Pulsed laser deposition of polyhydroxybutyrate biodegradable polymer thin films using ArF excimer laser

    NASA Astrophysics Data System (ADS)

    Kecskemeti, G.; Smausz, T.; Kresz, N.; Tóth, Zs.; Hopp, B.; Chrisey, D.; Berkesi, O.

    2006-11-01

    We demonstrated the pulsed laser deposition (PLD) of high quality films of a biodegradable polymer, the polyhydroxybutyrate (PHB). Thin films of PHB were deposited on KBr substrates and fused silica plates using an ArF ( λ = 193 nm, FWHM = 30 ns) excimer laser with fluences between 0.05 and 1.5 J cm -2. FTIR spectroscopic measurements proved that at the appropriate fluence (0.05, 0.09 and 0.12 J cm -2), the films exhibited similar functional groups with no significant laser-produced modifications present. Optical microscopic images showed that the layers were contiguous with embedded micrometer-sized grains. Ellipsometric results determined the wavelength dependence ( λ ˜ 245-1000 nm) of the refractive index and absorption coefficient which were new information about the material and were not published in the scientific literature. We believe that our deposited PHB thin films would have more possible applications. For example to our supposal the thin layers would be applicable in laser induced forward transfer (LIFT) of biological materials using them as absorbing thin films.

  6. New excimer laser technique for the correction of strabismus and diplopia

    NASA Astrophysics Data System (ADS)

    Azar, Dimitri T.

    1994-06-01

    We used the ArF excimer laser to determine the feasibility of performing prismatic photoablations in model eyes (plastic spheres simulating the eye), and in rabbit corneas. This would correct diplopia and small angles of deviation, and result in minimal refractive alterations. We modified excimer laser delivery system that achieved the desired corneal contour of prismatic ablations. 193-nm argon fluoride laser was used at fluence of 160 mJ/cm2 and ablation rate 5 Hz. 5.0-mm diameter, 40 um corneal epithelial ablation were followed by 5.0- mm diameter, prismatic photokeratectomy (PPK). We were able to achieve prismatic photoablation of PMMA blocks and lenses. No other refractive changes accompanied the prismatic photoablation of PMMA blocks and lenses. No other refractive changes accompanied the prismatic effect. In rabbits re-epithelialization of the 5-mm ablations was complete by day 3, and corneal haze was not observed by gross examination. Epithelial hyperplasia and subepithelial scarring were noted at the deep edges. PPK holds important therapeutic potential for fine-tuning results of conventional strabismus surgery, and for patients with stable diplopia following nerve palsy and ocular surgery.

  7. Excimer laser ablation of thick SiOx-films: Etch rate measurements and simulation of the ablation threshold

    NASA Astrophysics Data System (ADS)

    Ihlemann, J.; Meinertz, J.; Danev, G.

    2012-08-01

    Excimer laser ablation of 4.5 μm thick SiOx-films with x ≈ 1 is investigated at 193 nm, 248 nm, and 308 nm. Strong absorption enables precisely tunable removal depths. The ablation rates correlate with laser penetration depths calculated from low level absorption coefficients. The experimental ablation thresholds are in agreement with numerical simulations on the basis of linear absorption and one-dimensional heat flow. This behaviour is similar to that of strongly UV-absorbing polymers, leading to well controllable micro machining prospects. After laser processing, SiOx can be converted to SiO2, opening a route to laser based fabrication of micro optical components.

  8. A new high-aperture 193 nm microscope for the traceable dimensional characterization of micro- and nanostructures

    NASA Astrophysics Data System (ADS)

    Ehret, G.; Pilarski, F.; Bergmann, D.; Bodermann, B.; Buhr, E.

    2009-08-01

    A new deep UV transmission microscope for traceable micro- and nanometrology is currently being set up at the Physikalisch-Technische Bundesanstalt (PTB), the National Metrology Institute of Germany. The new microscope is especially designed to enable linewidth measurements of micro- and nanostructures with an unsurpassed absolute measurement uncertainty of down to 10 nm (95% confidence interval). The optical resolution is about 100 nm. The main field of this tool will be critical dimension (CD) metrology of photomasks used in optical lithography. In particular, this system offers the possibility of 'at-wavelength' metrology for the currently applied 193 nm lithography technology. The high lateral resolution will be attained by means of 193 nm excimer laser radiation for illumination in conjunction with a high-aperture objective (NA = 0.9). The illumination and imaging system will provide various imaging modalities, ranging from ordinary brightfield to specially structured illumination schemes. Traceability to the SI unit 'meter' will be accomplished by means of laser interferometry. The mechanical set-up is characterized by an ultra-stable bridge construction on a granite base and has been designed with special emphasis on realizing a positioning stability in the nanometer range. The instrument is being set up in the Clean Room Centre of the PTB and will be ready for operation in mid 2009. Simulation calculations, based on a rigorous optical modeling of the expected microscope images, are presented. These simulations are made for the important application of measuring Cr structures on quartz photomasks. Based on these simulations and on available data of the uncertainties of various experimental parameters—including instrument and sample parameters—expected uncertainty budgets for the measurement of the width of Cr lines on quartz substrates are estimated.

  9. Photoinitiated decomposition of substituted ethylenes: The photodissociation of vinyl chloride and acrylonitrile at 193 nm

    SciTech Connect

    Blank, D.A.; Suits, A.G.; Lee, Y.T.

    1997-04-01

    Ethylene and its substituted analogues (H{sub 2}CCHX) are important molecules in hydrogen combustion. As the simplest {pi}-bonded hydrocarbons these molecules serve as prototypical systems for understanding the decomposition of this important class of compounds. The authors have used the technique of photofragment translational spectroscopy at beamline 9.0.2.1 to investigate the dissociation of vinyl chloride (X=Cl) and acrylonitrile (X=CN) following absorption at 193 nm. The technique uses a molecular beam of the reactant seeded in helium which is crossed at 90 degrees with the output of an excimer laser operating on the ArF transition, 193.3 nm. The neutral photoproducts which recoil out of the molecular beam travel 15.1 cm where they are photoionized by the VUV undulator radiation, mass selected, and counted as a function of time. The molecular beam source is rotatable about the axis of the dissociation laser. The authors have directly observed all four of the following dissociation channels for both systems: (1) H{sub 2}CCHX {r_arrow} H + C{sub 2}H{sub 2}X; (2) H{sub 2}CCHX {r_arrow} X + C{sub 2}H{sub 3}; (3) H{sub 2}CCHX {r_arrow} H{sub 2} + C{sub 2}HX; and (4) H{sub 2}CCHX {r_arrow} HX + C{sub 2}H{sub 2}. They measured translational energy distributions for all of the observed channels and measured the photoionization onset for many of the photoproducts which provided information about their chemical identity and internal energy content. In the case of acrylonitrile, selective product photoionization provided the ability to discriminate between channels 2 and 4 which result in the same product mass combination.

  10. Progress in discharge-pumped excimer lasers

    NASA Astrophysics Data System (ADS)

    Pike, Charles T.

    1993-04-01

    This paper describes recent results achieved in the development of discharge pumped excimer lasers at the Textron Defense Systems organization (formerly the Avco Research Laboratory). Included is a description of a KrF laser with more than one Joule output at 2.4% efficiency, a 200 mJ XeCl laser operating with a 500 nsec wide pulse, and a several Joule, discharge pumped, KrCl laser operating at 222 nm. All of these devices are switched using thyratrons and are therefore capable of repetitive performance. The KrF and XeCl experiments were conducted with the same laser device operating with a conventional capacitor transfer excitation circuit for the KrF experiments but modified to operate with a pulser-sustainer discharge circuit using magnetic switching for the XeCl tests. The KrCl device is a 40 liter volume system built by Northrop and also operates with a magnetically switched discharge.

  11. Perspectives of using the 223-nm wavelength of the KrCl excimer laser for refractive surgery and for the treatment of some eye diseases

    NASA Astrophysics Data System (ADS)

    Bagayev, Sergei N.; Chernikh, Valery V.; Razhev, Alexander M.; Zhupikov, Andrey A.

    2000-06-01

    The new surgical UV ophthalmic laser system Medilex based on the KrCl (223 nm) excimer laser for refractive surgery was created. The comparative analysis of using the UV ophthalmic laser systems Medilex based on the ArF (193 nm) and the KrCl (223 nm) excimer lasers for the correction of refractive errors was performed. The system with the radiation wavelength of 223 nanometer of the KrCl excimer laser for refractive surgery was shown to have several medical and technical advantages over the system with the traditionally used radiation wavelength of 193 nanometer of the ArF excimer laser. In addition the use of the wavelength of 223 nanometer extends functional features of the system, allowing to make not only standard for this type systems surgical and therapeutic procedures but also to treat such ocular diseases as the glaucoma and herpetic keratities. For the UV ophthalmic laser systems Medilex three variations of the beam delivery system including special rotating masks and different beam homogenize systems were developed. All created beam delivery systems are able to make the correction of myopia, hyperopia, astigmatism and myopic or hyperopic astigmatism and may be used for therapeutic procedures. The results of the initial treatments of refractive error corrections using the UV ophthalmic laser systems Medilex for both photorefractive keratectomy (PRK) and LASIK procedures are presented.

  12. Research of the quenched dye lasers pumped by excimer lasers

    SciTech Connect

    Xue Shaolin; Lou Qihong

    1996-12-31

    In this paper, the quenched dye lasers pumped by XeCl and KrF excimer lasers were investigated theoretically and experimentally. Dye laser pulses with duration of 0.8 ns for XeCl laser pumping and 2 ns for KrF laser pumping were obtained. The dye Rhodamine 6G dissolved in methyl was used as the active medium in the quenched dye laser. When the pump laser was KrF and the active medium was Coumarin 498 the quenched dye laser emitted pulse with duration of about 2 ns. The characteristics of the quenched dye laser was also investigated in detail.

  13. Excimer laser irradiation of metal surfaces

    NASA Astrophysics Data System (ADS)

    Kinsman, Grant

    In this work a new method of enhancing CO2 laser processing by modifying the radiative properties of a metal surface is studied. In this procedure, an excimer laser (XeCl) or KrF) exposes the metal surface to overlapping pulses of high intensity, 10(exp 8) - 10(exp 9) W cm(exp -2), and short pulse duration, 30 nsec FWHM (Full Width Half Maximum), to promote structural and chemical change. The major processing effect at these intensities is the production of a surface plasma which can lead to the formation of a laser supported detonation wave (LSD wave). This shock wave can interact with the thin molten layer on the metal surface influencing to a varying degree surface oxidation and roughness features. The possibility of the expulsion, oxidation and redeposition of molten droplets, leading to the formation of micron thick oxide layers, is related to bulk metal properties and the incident laser intensity. A correlation is found between the expulsion of molten droplets and a Reynolds number, showing the interaction is turbulent. The permanent effects of these interactions on metal surfaces are observed through scanning electron microscopy (SEM), transient calorimetric measurements and Fourier transform infrared (FTIR) spectroscopy. Observed surface textures are related to the scanning procedures used to irradiate the metal surface. Fundamental radiative properties of a metal surface, the total hemispherical emissivity, the near-normal spectral absorptivity, and others are examined in this study as they are affected by excimer laser radiation. It is determined that for heavily exposed Al surface, alpha' (10.6 microns) can be increased to values close to unity. Data relating to material removal rates and chemical surface modification for excimer laser radiation is also discussed. The resultant reduction in the near-normal reflectivity solves the fundamental problem of coupling laser radiation into highly reflective and conductive metals such as copper and aluminum. The

  14. Optical Pattern Generator Using Excimer Laser

    NASA Astrophysics Data System (ADS)

    Hafner, Bernhard F.

    1988-01-01

    Reticles (masks on enlarged scale) are needed for optical pattern transfer in the production of integrated semiconductor circuits. In order to meet present requirements for 5X reticles only a direct writing technique is feasible. This means direct exposing of photoresist either with light or an electron beam. Many of todays highly dense reticles require some 10 5 to 10 6 discrete exposures when generated with an optical pattern generator. Optical pattern generators normally use mercury arc lamps to expose positive photoresist, which in turn need 200 milliseconds for each of these discrete exposures, thus requiring to stop the table at every exposure position ("stop and go" mode). This results in running times of several days per reticle. Therefore most reticles are nowadays being manufactured with very expensive e-beam machines. In the early 80's we started the first experiments to expose photoresist with an excimer laser. In order to obtain the maximum gain in speed, the goal was to operate with only one excimer laser pulse per exposure, so that a fast "flash on the fly" operation with an optical pattern generator became true. Equipping a conventional optical pattern generator with an excimer laser as the light source, it has become possible to expose substrates coated with standard photoresist in the "flash on the fly" mode with only 13 nanoseconds per flash. So the thruput could be increased up to 25 times in comparison to a pattern generator equipped with a mercury lamp. A comparison of both operation modes will show that an immense increase of speed is possible, even when a ten years old M3600 pattern generator is used. This system is in function now with very high reliability since more than three years in our IC development line.

  15. High Spatial Resolution Analysis of Carbonates by In Situ Excimer Laser Ablation MC-ICP-MS

    NASA Astrophysics Data System (ADS)

    Shuttleworth, S.; Lloyd, N.; Douthitt, C.

    2012-12-01

    Speleothems are important climate archives. The time resolution of the paleochlimate proxies depends on the growth rates and the precision limitation of the analytical instrumentation [1]. As a consequence, for speleothems, better analytical precision combined with better spatial resolution will always be the goal, driven by a need to probe the timing and duration of climate events [1]. The Thermo Scientific NEPTUNE Plus with Jet Interface option offers unparalleled MC-ICP-MS sensitivity for heavy elements. An ion yield of >3 % has previously been reported for uranium solutions introduced by desolvating nebulizer[2]. For laser ablation Hf, the Jet Interface with N2 addition significantly improved sensitivity, which allowed precise and accurate 176Hf/177Hf ratios to be calculated using a spot size of just 25 μm diameter [3]. A Thermo Scientific NEPTUNE Plus with Jet Interface option was coupled with a Photon Machines excimer laser ablation system. This system features a short pulse width (4ns) 193 nm excimer laser and the HELEX 2 volume sample cell. The 193nm wavelength has been shown to reduce the particle size distribution of the aerosol produced by the laser ablation process [4] and this in turn has been shown to help minimize the effects of fractionation by ensuring that particles are in a size range so as to avoid incomplete vaporization and ionization in the plasma [5]. In this work we investigate U-Th dating of carbonates. Accurate LA U-Th isotope measurements on carbonates with U concentrations smaller than 1 μg/g are difficult due to small ion beams [1]. Hoffman et. al. [1] noted individual LA U-Th ratio precisions of about 2% (2 sigma) on a 134 ka sample with 134 μg/g U concentration. In this work we apply a combination of the high sampling efficiency two volume cell plus mixed gas plasmas to further enhance the capability. [1] Hoffman, D.L., et al. (2009). Chemical Geology. 259 253-261 [2] Bouman, C., et al. (2009). Geochim. Cosmochim. Acta. 73

  16. Excimer laser annealing for low-voltage power MOSFET

    NASA Astrophysics Data System (ADS)

    Chen, Yi; Okada, Tatsuya; Noguchi, Takashi; Mazzamuto, Fulvio; Huet, Karim

    2016-08-01

    Excimer laser annealing of lumped beam was performed to form the P-base junction for high-performance low-voltage-power MOSFET. An equivalent shallow-junction structure for the P-base junction with a uniform impurity distribution is realized by adopting excimer laser annealing (ELA). The impurity distribution in the P-base junction can be controlled precisely by the irradiated pulse energy density and the number of shots of excimer laser. High impurity activation for the shallow junction has been confirmed in the melted phase. The application of the laser annealing technology in the fabrication process of a practical low-voltage trench gate MOSFET was also examined.

  17. Excimer laser induced nanostructuring of silicon surfaces.

    PubMed

    Kumar, Prashant; Krishna, Mamidipudi Ghanashyam; Bhattacharya, Ashok

    2009-05-01

    The effect of KrF excimer laser energy density (below and above the ablation threshold), number of shots and angle of laser incidence on the morphological reconstruction, structure and specular reflectance of Si[311] surfaces is reported. At low energy densities (0.1 to 0.3 J/cm2) laser irradiation results in a variety of nanostructures, depending on laser energy density and number of shots, such as nanopores (40-60 nm dia) and nanoparticles (40-80 nm dia). At energies greater than the laser ablation threshold (2 to 5 J/cm2) the formation of nanowires (200 nm dia, 6-8 microm length), and closely spaced silicon nanograins (100-150 nm dia) is observed. Experiments to study the effect of laser irradiation in the proximity of a fixed shape such as a linear step edge in the form of a stainless steel blade and a cylindrical cross-section Cu wire were also carried out. In both cases, linearly organized nanoparticles (150-200 nm diameter) and nanowires (60-80 nm diameter) formed close to the edge. There is a systematic degradation of long-range order with the number of shots and laser energy density as evidenced from X-ray diffraction studies. At an energy density of 2 J/cm2, and 100 shots the [311] oriented silicon surface made a transition to a randomly oriented nanocrystalline state. PMID:19452995

  18. Ignition by excimer laser photolysis of ozone

    SciTech Connect

    Lucas, D.; Dunn-Rankin, D.; Hom, K.; Brown, N.J.

    1987-08-01

    The authors have ignited mixtures of hydrogen, oxygen, and ozone in closed cells with 248 nm radiation from a KrF excimer laser. Ozone, the only significant absorber in this system, absorbs a single photon and produces oxygen atoms which initiate combustion. A discretized, time-dependent Beer's law model is used to demonstrate that the radical concentration immediately after photolysis is a function of laser power, ozone concentration, focal length, and separation between the lens and reactions cell. Spark schlieren photographs are used to visualize the ignition events and identify the ignition sites. The effects of equivalence ratio, pressure, and the initial gas temperature on the minimum ozone concentration needed to produce ignition are presented, and only the initial temperature has a significant effect.

  19. Excimer laser ablation of ferrite ceramics

    NASA Astrophysics Data System (ADS)

    Tam, A. C.; Leung, W. P.; Krajnovich, D.

    We study the ablation of Ni-Zn or Mn-7n ferrites by 248-nm KrF excimer laser irradiation for high-resolution patterning. A transfer lens system is used to project the image of a mask irradiated by the pulsed KrF laser onto the ferrite sample. The threshold fluente for ablation of the ferrite surface is about 0.3 J/cm2. A typical fluente of 1 J/cm2 is used to produce good-quality patterning. Scanning electron microscopy of the ablated area shows a "glassy" skin with extensive microcracks and solidified droplets being ejected that is frozen in action. This skin can be removed by ultrasonic cleaning.

  20. [Is there a future for the Excimer laser in refractive surgery?].

    PubMed

    Pouliquen, Y; Hanna, K; Waring, G; Savoldelli, M

    1990-02-01

    The refractive surgery concerns all the surgical procedures implicated in the refractive power change of the cornea. Its clinical results are just known, and a new physical procedure is becoming capable to replace surgery: the Excimer laser. Without any instrumental contact with the corneal surface, the laser beam is able to remodel the corneal tissue, and to treat astigmatism, myopia, hypermetropia. Millions of people could be treated by such a laser, and could leave their glasses. Biological effects on rabbit and monkeys are presented. An argon fluoride excimer laser (193 nm) with a moving slit delivery system was used to perform anterior myopic keratomileusis in both eyes of 37 rabbits and 15 monkeys. Histological analysis of the corneas was made after ablation and at intervals up to 20 months. By slit examination at the longer follow up time, 60% of treated rabbits and 40% of treated monkeys keep a clear cornea, but the others had central spotty subepithelial haze. Light and electron microscopy documented corneal healing. In the clear corneas a good reconstitution of the epithelium, its basal lamina was observed, and anterior stromal corneas contained few active fibrocytes with a good preservation of the connective lamellar structure. On the contrary, in the cornea with opacification focal areas of 20 microns thick subepithelial scarring were present and the interface between epithelial cells and anterior stroma remained disturbed by incomplete, disrupted or duplicated basal lamina. Differences between the responses of monkeys, rabbits corneas to the same photoablation procedure remain unclear.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2115392

  1. Glass etching initiated by excimer laser photolysis of CF/sub 2/Br/sub 2/

    SciTech Connect

    Brannon, J.H.

    1986-04-24

    KrF and ArF excimer laser irradiation of glass surfaces immersed in gaseous CF/sub 2/Br/sub 2/ is found to induce etching. The etch mechanism is considered to be nonthermal on the basis of the small value of the glass absorption coefficent and wavelength variable etching experiments. The etch rate dependence on surface fluence is presented for three pressures. SEM photos reveal a rough surface morphology in the etched region that apparently is not a chemical effect but results solely from the laser irradiation. Photochemical and spectroscopic analysis of the irradiated gas provides evidence for CF/sub 2/ and CF/sub 2/Br as being major photolysis products. C/sub 2/F/sub 4/ was also found to cause etching at 248 and 193 nm. This is evidence that CF/sub 2/, resulting from C/sub 2/F/sub 4/ photolysis, is alone capable of initiating glass etching in the presence of laser light. The paper concludes by discussing the observed inability of the CF/sub 3/ releasing parent gases CF/sub 3/Br and CF/sub 3/I to significantly etch glass when irradiated in their appropriate absorption bands. 31 references, 9 figures, 1 table.

  2. Focused excimer laser initiated and radio frequency sustained plasma formation in high pressure air

    NASA Astrophysics Data System (ADS)

    Giar, Ryan

    A doctoral thesis project was performed to experimentally investigate the feasibility of focused excimer laser initiation of air plasmas for radio frequency sustainment. A 193 nm, 15 MW, 300 mJ laser was focused with a 18 cm focal length lens to form a small, high density (ne ~ 10 14 cm--3) seed plasma. These laser plasmas were produced inside a borosilicate glass tube around which was wrapped a 5 turn helical antenna. This antenna was powered with 5 kW of 13.56 MHz of radiation for 1.5 s. This was accomplished at a pressure of 22 Torr, resulting in a large volume (300 cm3) air plasma. Diagnostic measurements of this air plasma determined an electron density of 5E10 cm-3 and an electron temperature 1.3 eV with a neutral temperature of 3500 K. The collision frequency was measured to be 9E10 Hz which resulted in a plasma-loaded antenna resistance of 6 O with a voltage reflection coefficient of 0.7.

  3. Properties of AlF3 and LaF3 films at 193nm

    NASA Astrophysics Data System (ADS)

    Xue, Chunrong; Shao, Jianda

    2010-10-01

    In order to develop low loss, high-performance 193nm Fluoride HR mirrors and anti-reflection coatings, LaF3 and AlF3 materials, used for a single-layer coating, were deposited by a molybdenum boat evaporation process. Various microstructures that formed under different substrate temperatures and with deposition rates were investigated. The relation between these microstructures (including cross section morphology, surface roughness and crystalline structure), the optical properties (including refractive index and optical loss) and mechanical properties (stress) were investigated. Furthermore, AlF3 used as a low-index material and LaF3 used as a high-index material were designed and deposited for multilayer coatings. Transmittance, reflectance, stress, and the laser-induced damage threshold (LIDT) were studied. It is shown that AlF3 and LaF3 thin films, deposited on the substrate at a temperature of 300 °C, obtained good quality thin films with high transmittance and little optical loss at 193 nm. For multilayer coatings, the absorption mainly comes from LaF3. Based on these studies, The thickness of 193nm films was controled by a 1/3 baffle with pre-coating technology. the LaF3/AlF3 AR coantings and HR mirrors at 193nm were designed and deposited. Under the present experimental conditions, the reflectance of LaF3/AlF3 HR mirror is up to 96%, and its transmittance is 1.5%. the LaF3/AlF3 AR coanting's residual reflectance is less than 0.14%, and single-sided transmittance is 93.85%. To get a high-performance 193nm AR coating, super-polished substrate is the best choice.

  4. XeCl excimer laser excited by longitudinal discharge

    SciTech Connect

    Zhou, Z.; Zeng, Y.; Qiu, M.

    1983-08-15

    XeCl excimer laser excited by longitudinal gas discharge is reported. The main characteristics of the laser output and the laser energy in dependence of the operating parameters were measured. The laser pulse duration was 35 ns and the maximum laser energy 317 ..mu..J with improvement by preionization.

  5. VUV spectrophotometry for photomasks characterization at 193 nm

    NASA Astrophysics Data System (ADS)

    Yang, Minghong; Leiterer, Jork; Gatto, Alexandre; Kaiser, Norbert; Höllein, Ingo; Teuber, Silvio; Bubke, Karsten

    2005-10-01

    This paper intends to develop a measurement system to characterize photomasks for 193 nm lithography applications. Based on the VUV spectrophotometer at the Fraunhofer IOF institute, some modifications have been addressed to fulfil these special measurements. Characterizations on photomasks have been successfully carried out, which show good correlations to simulations.

  6. High-performance 193nm photoresists based on fluorosulfonamide

    NASA Astrophysics Data System (ADS)

    Li, Wenjie; Chen, Kuang-Jung; Kwong, Ranee; Lawson, Margaret C.; Khojasteh, Mahmoud; Popova, Irene; Varanasi, P. Rao; Shimokawa, Tsutomu; Yamaguchi, Yoshikazu; Kusumoto, Shiro; Sugiura, Makoto; Kawakami, Takanori; Slezak, Mark; Dabbagh, Gary; Liu, Zhi

    2007-03-01

    The combination of immersion lithography and reticle enhancement techniques (RETs) has extended 193nm lithography into the 45nm node and possibly beyond. In order to fulfill the tight pitch and small critical dimension requirements of these future technology nodes, the performance of 193nm resist materials needs to further improve. In this paper, a high performance 193nm photoresist system based on fluorosulfonamide (FSM) is designed and developed. The FSM group has good transparency at 193nm. Compared to the commonly used hexafluoroalcohol (HFA) group, the trifluoromethyl sulfonamide (TFSM) functionality has a lower pKa value and contains less fluorine atoms. Polymers containing the TFSM functionality have exhibited improved dissolution properties and better etch resistance than their HFA counterparts. Resists based on the FSM-containing polymers have shown superior lithographic performance for line, trench and contact hole levels under the 45nm node exposure conditions. In addition, FSM resists have also demonstrated excellent bright field and dark field compatibility and thereby make it possible to use one resist for both bright field and dark field level applications. The structure, property and lithographic performance of the FSM resist system are reported.

  7. The excimer laser: science fiction fantasy or practical tool?

    PubMed

    Biamino, Giancarlo

    2004-12-01

    Nearly 20 years ago, in vitro experiments left no doubt about the fact that laser light can ablate atherosclerotic plaque. The initial enthusiastic results with the technology, particularly in coronary arteries, were followed by reports showing unacceptably high restenosis and complication rates. These poor results were due to the premature application of an underdeveloped technology, a lack of understanding of laser/tissue interaction, and the use of incorrect lasing techniques. Consequently, and without discrimination, all lasers were banned from the catheterization laboratories for nearly a decade. Technological enhancements of the excimer laser, combined with refined catheter lasing techniques, resulted in greater debulking of atherosclerotic material in long superficial femoral artery occlusions. These results triggered the application of the excimer laser technique as an atherectomy tool in more complex lesions below the knee. The multicenter Laser Atherectomy for Critical Ischemia study clearly demonstrated that the excimer laser technology resulted in limb salvage rates >90% in patients with critical limb ischemia (CLI). Furthermore, new clinical results indicate that the excimer laser is very effective in dissolving thrombotic obstructions, redirecting this technology to the coronary field. The results of the excimer laser in CLI validate the role of the cool laser in treating complex peripheral vascular disease. The results suggest a larger indication for this technology and support a more aggressive use of these interventional techniques in the treatment of this large patient cohort. However, all lasers are not equally effective in debulking atherosclerotic material. Only the athermic process associated with the excimer laser produces a safe and effective endovascular ablation of obstructive atherosclerotic and/or thrombotic material. The appropriate and safe utilization of the equipment and lasing techniques, combined with correct indications and

  8. Study of 193-nm resist degradation under various etch chemistries

    NASA Astrophysics Data System (ADS)

    Bazin, Arnaud; May, Michael; Pargon, Erwine; Mortini, Benedicte; Joubert, Olivier

    2007-03-01

    The effectivity of 193nm photoresists as dry etch masks is becoming more and more critical as the size of integrated devices shrinks. 193nm resists are known to be much less resistant to dry etching than 248nm resists based on a poly(hydroxystyrene) polymer backbone. The decrease in the resist film budget implies a better etch resistance to use single layer 193nm photoresists for the 65nm node and beyond. In spite of significant improvements made in the past decade regarding the etch resistance of photoresists, much of the fundamental chemistry and physics that could explain the behaviour of these materials has to be better understood. Such knowledge is necessary in order to propose materials and etch processes for the next technology nodes (45nm and below). In this paper, we report our studies on the etch behaviour of different 193nm resist materials as a function of etch chemistry. In a first step, we focus our attention on the interactions between photoresists and the reactive species of a plasma during a dry etch step. Etch experiments were carried out in a DPS (Decoupled Plasma Source) high density chamber. The gas chemistry in particular was changed to check the role of the plasma reactive species on the resist. O II, Cl II, CF 4, HBr and Ar gas were used. Etch rates and chemical modifications of different materials were quantified by ellipsometry, Fourier Transformed Infrared Spectroscopy (FTIR), and X-Ray Photoelectrons Spectroscopy (XPS). We evaluated different materials including 248nm model polymer backbones (pure PHS or functionalized PHS), and 193nm model polymers (PMMA and acrylate polymers) or resist formulations. Besides the influence of resist chemistry, the impact of plasma parameters was addressed.

  9. Excimer laser ceramic and metal surface alloying applications

    NASA Astrophysics Data System (ADS)

    Hontzopoulos, E.; Zervaki, A.; Zergioti, Y.; Hourdakis, G.; Raptakis, E.; Giannacopoulos, A.; Fotakis, C.

    1991-02-01

    Recent excimer laser based deposition and surface modification techniques for ceramic and metallurgical engineering applications are reported. These include the improvement of the anti-corrosion and erosion properties and wear resistance of metal alloys and the formation of surface conducting patterns on ceramic materials. Excimer laser chemical vapour deposition (LCVD) applications B, AI and Hf or multielement combinations are discussed together with studies which aim at a better understanding of the fundamental processes governing the deposition process.

  10. Characterization of AlF3 thin films at 193 nm by thermal evaporation

    NASA Astrophysics Data System (ADS)

    Lee, Cheng-Chung; Liu, Ming-Chung; Kaneko, Masaaki; Nakahira, Kazuhide; Takano, Yuuichi

    2005-12-01

    Aluminum fluoride (AlF3) was deposited by a resistive heating boat. To obtain a low optical loss and high laser-induced damage threshold (LIDT) at 193 nm, the films were investigated under different substrate temperatures, deposition rates, and annealing after coating. The optical property (the transmittance, refractive index, extinction coefficient, and optical loss) at 193 nm, microstructure (the cross-sectional morphology, surface roughness, and crystalline structure), mechanical property (stress), and LIDT of AlF3 thin films have been studied. AlF3 thin films deposited at a high substrate temperature and low deposition rate showed a lower optical loss. The highest LIDT occurred at the substrate temperature of 150 °C. The LIDT of the films prepared at a deposition rate of 2 Å/s was higher than that at other deposition rates. The annealing process did not influence the optical properties too much, but it did increase the LIDT and stress.

  11. Characterization of AlF3 thin films at 193 nm by thermal evaporation.

    PubMed

    Lee, Cheng-Chung; Liu, Ming-Chung; Kaneko, Masaaki; Nakahira, Kazuhide; Takano, Yuuichi

    2005-12-01

    Aluminum fluoride (AlF3) was deposited by a resistive heating boat. To obtain a low optical loss and high laser-induced damage threshold (LIDT) at 193 nm, the films were investigated under different substrate temperatures, deposition rates, and annealing after coating. The optical property (the transmittance, refractive index, extinction coefficient, and optical loss) at 193 nm, microstructure (the cross-sectional morphology, surface roughness, and crystalline structure), mechanical property (stress), and LIDT of AlF3 thin films have been studied. AlF3 thin films deposited at a high substrate temperature and low deposition rate showed a lower optical loss. The highest LIDT occurred at the substrate temperature of 150 degrees C. The LIDT of the films prepared at a deposition rate of 2 A/s was higher than that at other deposition rates. The annealing process did not influence the optical properties too much, but it did increase the LIDT and stress. PMID:16353803

  12. Temperature- and pressure-dependent absorption coefficients for CO2 and O2 at 193 nm

    NASA Astrophysics Data System (ADS)

    Hartinger, K. T.; Nord, S.; Monkhouse, P. B.

    Absorption of laser radiation at 193 nm by CO2 and O2 was studied at a series of different temperatures up to 1273 K and pressures up to 1 bar. The spectrum for CO2 was found to be broadband, so that absorption could be fitted to a Beer-Lambert law. On the other hand, the corresponding O2 spectrum is strongly structured and parameterisation requires a more complex relation, depending on both temperature and the product (pressure × absorption path length). In this context, the influence of spectral structure on the resulting spectrally integrated absorption coefficients is discussed. Using the fitting parameters obtained, effective transmissions at 193 nm can be calculated for a wide range of experimental conditions. As an illustration of the practical application of these data, the calculation of effective transmission for a typical industrial flue gas is described.

  13. Calcified lesion modeling for excimer laser ablation

    NASA Astrophysics Data System (ADS)

    Scott, Holly A.; Archuleta, Andrew; Splinter, Robert

    2009-06-01

    Objective: Develop a representative calcium target model to evaluate penetration of calcified plaque lesions during atherectomy procedures using 308 nm Excimer laser ablation. Materials and Methods: An in-vitro model representing human calcified plaque was analyzed using Plaster-of-Paris and cement based composite materials as well as a fibrinogen model. The materials were tested for mechanical consistency. The most likely candidate(s) resulting from initial mechanical and chemical screening was submitted for ablation testing. The penetration rate of specific multi-fiber catheter designs and a single fiber probe was obtained and compared to that in human cadaver calcified plaque. The effects of lasing parameters and catheter tip design on penetration speed in a representative calcified model were verified against the results in human cadaver specimens. Results: In Plaster of Paris, the best penetration was obtained using the single fiber tip configuration operating at 100 Fluence, 120 Hz. Calcified human lesions are twice as hard, twice as elastic as and much more complex than Plaster of Paris. Penetration of human calcified specimens was highly inconsistent and varied significantly from specimen to specimen and within individual specimens. Conclusions: Although Plaster of Paris demonstrated predictable increases in penetration with higher energy density and repetition rate, it can not be considered a totally representative laser ablation model for calcified lesions. This is in part due to the more heterogeneous nature and higher density composition of cadaver intravascular human calcified occlusions. Further testing will require a more representative model of human calcified lesions.

  14. Ignition by excimer laser photolysis of ozone

    SciTech Connect

    Lucas, D.; Dunn-Rankin, D.; Hom, K.; Brown, N.J.

    1986-10-01

    We have ignited mixtures of hydrogen, oxygen, and ozone in closed cells with 248 nm radiation from a KrF excimer laser. Ozone, the only significant absorber in this system, absorbs a single photon and produces oxygen atoms which initiate combustion. A discretized, time-dependent Beer's law model is used to demonstrate that the radical concentration immediately after photolysis is a function of laser power, ozone concentration, focal length, and separation between the lens and reaction cell. Spark schileren photographs are used to visualize the ignition events and identify the ignition sites. The effects of equivalence ratio, pressure, and the initial gas temperature on the minimum ozone concentration needed to produce ignition are presented, and only the initial temperature has a significant effect. Modelling studies of the ignition process aid in the interpretation of the experimental results, and show that the ignition we observe is not due solely to thermal effects, but is strongly dependent on the number and type of radicals present initially after photolysis. Ignition using other hydocarbons as fuels was also demonstrated. 30 refs., 9 figs. 2 tabs.

  15. Ignition by excimer laser photolysis of ozone

    SciTech Connect

    Lucas, D.; Dunn-Rankin, D.; Hom, K.; Brown, N.J.

    1986-01-01

    The authors have ignited mixtures of hydrogen, oxygen, and ozone in closed cells with 248 nm radiation from a KrF excimer laser. Ozone, the only significant absorber in this system, absorbs a single photon and produces oxygen atoms which initiate combustion. A discretized, time-dependent Beer's law model is used to demonstrate that the radical concentration immediately after photolysis is a function of laser power, ozone concentration, focal length, and separation between the lens and reaction cell. Spark schlieren photographs are used to visualize the ignition events and identify the ignition sites. The effects of equivalence ratio, pressure, and the initial gas temperature on the minimum ozone concentration needed to produce ignition are presented, and only the initial temperature has a significant effect. Modelling studies of the igniton process aid in the interpretation of the experimental results, and show that the ignition is not due solely to thermal effects, but is strongly dependent on the number and type of radicals present initially after photolysis. Ignition using other hydrocarbons as fuels was also demonstrated.

  16. Determination of flue gas alkali concentrations in fluidized-bed coal combustion by excimer-laser-induced fragmentation fluorescence

    SciTech Connect

    Hartinger, K.T.; Monkhouse, P.B.; Wolfrum, J.; Baumann, H.; Bonn, B.

    1994-12-31

    Gas-phase sodium concentrations were measured for the first time in situ in the flue gas of a fluidized-bed reactor by the excimer-laser-induced fragmentation fluorescence (ELIF) technique. This method involves using ArF-excimer laser light at 193 nm to simultaneously photodissociate the alkali compounds of interest and excite electronically the alkali atoms formed. The resulting fluorescence from Na (3{sup 2}P) atoms can he readily detected at 589 nm. Measured signals were converted to absolute concentrations using a calibration system that monitors alkali compounds under known conditions of temperature, pressure, and composition and rising the same optical setup as at the reactor. Several different coals were investigated under a specific set of reactor conditions at total pressures close to 1 bar. Sodium concentrations ranging from the sub-ppb region to 20 ppb were obtained, and a detection limit for sodium of 0.1 ppb under the present conditions was estimated. Over the course of the reactor program, contrasting concentration histories were observed for the two lignites and the hard coal investigated. In particular, significantly higher sodium concentrations were found for the hard coal, consistent with both the higher chlorine and sodium contents determined in the corresponding coal analysis.

  17. Novel high refractive index fluids for 193nm immersion lithography

    NASA Astrophysics Data System (ADS)

    Santillan, Julius; Otoguro, Akihiko; Itani, Toshiro; Fujii, Kiyoshi; Kagayama, Akifumi; Nakano, Takashi; Nakayama, Norio; Tamatani, Hiroaki; Fukuda, Shin

    2006-03-01

    Despite the early skepticism towards the use of 193-nm immersion lithography as the next step in satisfying Moore's law, it continuous to meet expectations on its feasibility in achieving 65-nm nodes and possibly beyond. And with implementation underway, interest in extending its capability for smaller pattern sizes such as the 32-nm node continues to grow. In this paper, we will discuss the optical, physical and lithographic properties of newly developed high index fluids of low absorption coefficient, 'Babylon' and 'Delphi'. As evaluated in a spectroscopic ellipsometer in the 193.39nm wavelength, the 'Babylon' and 'Delphi' high index fluids were evaluated to have a refractive index of 1.64 and 1.63 with an absorption coefficient of 0.05/cm and 0.08/cm, respectively. Lithographic evaluation results using a 193-nm 2-beam interferometric exposure tool show the imaging capability of both high index fluids to be 32-nm half pitch lines and spaces.

  18. Cycloolefin-maleic anhydride copolymers for 193-nm resist compositions

    NASA Astrophysics Data System (ADS)

    Rahman, M. D.; Bae, Jun-Bom; Cook, Michelle M.; Durham, Dana L.; Kudo, Takanori; Kim, Woo-Kyu; Padmanaban, Munirathna; Dammel, Ralph R.

    2000-06-01

    Cycloolefin/maleic anhydride systems are a favorable approach to dry etch resistant resists for 193 nm lithography. This paper reports on poly(BNC/HNC/NC/MA) tetrapolymers, from t- butylnorbornene carboxylate (BNC), hydroxyethyl-norbornene carboxylate (HNC), norbornene carboxylic acid (NC) and maleic anhydride (MA). It was found that moisture has to be excluded in the synthesis of these systems if reproducible results are to be obtained. Lithographic evaluation of an optimized, modified polymer has shown linear isolated line resolution down to 100 nm using conventional 193 nm illumination. Possible reactions of the alcohol and anhydride moieties are discussed, and the effect of the anhydride unit on polymer absorbance is discussed using succinnic anhydride as a model compound.

  19. Matrix metalloproteinase expression in excimer laser wounded rabbit corneas

    NASA Astrophysics Data System (ADS)

    Hahn, Taewon; Chamon, Wallace; Akova, Yonja; Stark, Walter J.; Stetler-Stevenson, William G.; Azar, Dimitri T.

    1994-06-01

    This study was performed to obtain information about matrix metalloproteinase (MMP) expression in excimer-wounded corneas and to determine whether MMPs expression correlates with the depth of the ablation. 6-mm excimer keratectomy (60 or 180 micrometers ) was performed using the 193-mm ArF excimer laser on 12 NZW rabbits. Corneas treated with mechanical epithelial debridement and untreated corneas served as controls. Rabbits were killed at 20 and 30 hr after laser ablation. Zymography after SDS extraction was performed on regenerated central epithelium and the central stroma to determine MMPs expression. We observed enzymatic activity of a 92 KDa band in the epithelium of excimer-ablated corneas but not in that following debridement wounds and untreated controls. The expression of the 92 KDa MMP was most pronounced with the deeper excimer ablation. A 72 KDa band of enzymatic activity present in the stroma of all treated and control eyes was also seen in the epithelium of excimer-ablated corneas. These proteolytic enzymes may play an important role in wound healing and remodelling after excimer keratectomy.

  20. Characterization of calcium phosphate coatings doped with Mg, deposited by pulsed laser deposition technique using ArF excimer laser.

    PubMed

    Mróz, W; Jedyński, M; Prokopiuk, A; Slósarczyk, A; Paszkiewicz, Z

    2009-01-01

    Calcium phosphate layers were deposited on Ti6Al4V substrates with TiN buffer layers by use of pulsed laser deposition method. With this technique three pressed pellets consisted of tricalcium phosphate (TCP, Ca(3)(PO(4))(2)), hydroxyapatite (HA, Ca(10)(PO(4))(6)(OH)(2)) and hydroxyapatite-doped with magnesium (HA with 4% of Mg and trace amount of (Ca,Mg)(3)(PO(4))(2)) were ablated using ArF excimer laser (lambda=193 nm). The using of different targets enabled to determine the influence of target composition on the nature of deposited layers. The obtained deposits were characterized by means of Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction method (XRD). The obtained Fourier spectras revealed differences in terms of intensity of spectral bands of different layers. The analysis from XRD showed that Mg-doped HA layer has crystalline structure and TCP and HA layers composition is characterized by amorphous nature. PMID:18407507

  1. 193 nm photodissociation of larger multiply-charged biomolecules

    NASA Astrophysics Data System (ADS)

    Guan, Ziqiang; Kelleher, Neil L.; O'Connor, Peter B.; Aaserud, David J.; Little, Daniel P.; McLafferty, Fred W.

    1996-12-01

    In contrast to most ion dissociation methods, 193 nm ultraviolet photodissociation of electrosprayed melittin (2.8 kDa) and ubiquitin (8.6 kDa) molecular ions yields new c and z ions (backbone amine bond dissociation) that provide additional sequence information. Dissociation by collisions or infrared photons produce b and y ions; for cleavages between the same amino acids the c ion represents the addition of NH2 to the b ion, and z the loss of NH2 from the y ion, so that these ions can be differentiated by this ± 16.02 Da difference. However, 193 nm photodissociation of 12-29 kDa ions as yet does not give collectable product ions, and that of the very stable y182+ ion from ubiquitin only effects a side chain loss. 193 nm irradiation of negative ions of all-T 30-mer DNA appears to eject electrons; apparently this is the first observation of electron photodetachment from multiply-charged negative ions.

  2. Inorganic immersion fluids for ultrahigh numerical aperture 193 nm lithography

    NASA Astrophysics Data System (ADS)

    Zhou, Jianming; Fan, Yongfa; Bourov, Anatoly; Smith, Bruce W.

    2006-05-01

    Immersion lithography has become attractive since it can reduce critical dimensions by increasing numerical aperture (NA) beyond unity. Among all the candidates for immersion fluids, those with higher refractive indices and low absorbance are desired. Characterization of the refractive indices and absorbance of various inorganic fluid candidates has been performed. To measure the refractive indices of these fluids, a prism deviation angle method was developed. Several candidates have been identified for 193 nm application with refractive indices near 1.55, which is approximately 0.1 higher than that of water at this wavelength. Cauchy parameters of these fluids were generated and approaches were investigated to tailor the fluid absorption edges to be close to 193 nm. The effects of these fluids on photoresist performance were also examined with 193 nm immersion lithography exposure at various NAs. Half-pitch 32 nm lines were obtained with phosphoric acid as the immersion medium at 1.5 NA. These fluids are potential candidates for immersion lithography technology.

  3. Excimer Laser Surface Treatment Of Non-Ferrous Alloys

    NASA Astrophysics Data System (ADS)

    Georgiopoulos, Michael; Hontzopoulos, Elias I.; Fotakis, Costas; Tsipas, D. N.; Floros, T.

    1989-04-01

    Excimer laser (KrF, ArF) radiation has been used for the surface modification of Al - Si and Ni alloys with the aim to improve their corrosion-errosion and hardness properties. A variety of experimental techniques including direct laser surface treatment and laser assisted chemical vapour deposition (CVD) have been employed and the parameters for process optimization have been determined.

  4. The influence of ArF excimer laser micromachining on physicochemical properties of bioresorbable poly(L-lactide)

    NASA Astrophysics Data System (ADS)

    Stepak, Bogusz D.; Antończak, Arkadiusz J.; Szustakiewicz, Konrad; Pezowicz, Celina; Abramski, Krzysztof M.

    2016-03-01

    The main advantage of laser processing is a non-contact character of material removal and high precision attainable thanks to low laser beam dimensions. This technique enables forming a complex, submillimeter geometrical shapes such as vascular stents which cannot be manufactured using traditional techniques e.g. injection moulding or mechanical treatment. In the domain of nanosecond laser sources, an ArF excimer laser appears as a good candidate for laser micromachining of bioresorbable polymers such as poly(L-lactide). Due to long pulse duration, however, there is a risk of heat diffusion and accumulation in the material. In addition, due to short wavelength (193 nm) photochemical process can modify the chemical composition of ablated surfaces. The motivation for this research was to evaluate the influence of laser micromachining on physicochemical properties of poly(L-lactide). We performed calorimetric analysis of laser machined samples by using differential scanning calorimetry (DSC). It allowed us to find the optimal process parameters for heat affected zone (HAZ) reduction. The chemical composition of the ablated surface was investigated by FTIR in attenuated total reflectance (ATR) mode.

  5. Surface treatment of metals with excimer and CO2 lasers

    NASA Astrophysics Data System (ADS)

    Haidemenopoulos, G. N.; Zervaki, A.; Papadimitriou, K.; Tsipas, D. N.; McIntosh, J.; Zergioti, G.; Manousaki, G.; Hontzopoulos, Elias I.

    1993-05-01

    The availability of a variety of lasers including the high-power cw CO2 lasers, the pulsed- mode infrared Nd-YAG, and the pulsed-mode ultraviolet excimer laser has led to the development of many interesting applications of laser technology to materials processing. Among them the surface modification of metallic alloys appears to be one of the most important and very close to implementation in various industries. Specifically the applications of excimer lasers have been discussed in a recent workshop in the framework of the Eureka EU 205 program. The major topics concerned with surface modifications that were discussed in this workshop were surface smoothing and roughening, surface cleaning of Ti and Cu, mixing and interdiffusion of predeposited layers, surface irradiation of Cu-alloys to improve the corrosion resistance, surface remelting of Al-alloys for grain refinement through rapid solidification, and surface remelting of Ni-P electroless coatings on Al alloys for the improvement of corrosion resistance. Laser alloying of Ni-base superalloys has also been discussed. Applications discussed here include the surface treatment of Ni-base superalloys with high-power CO2 laser, the surface treatment of aluminum alloys with excimer lasers, the laser assisted chemical vapor deposition (LCVD) of wear and corrosion resistant layers of Ti, TiC, and TiN on tool steels, and the fracture surface sulphur printing with excimer lasers.

  6. An AC phase measuring interferometer for measuring dn/dT of fused silica and calcium fluoride at 193 nm

    SciTech Connect

    Shagam, R.N.

    1998-09-01

    A novel method for the measurement of the change in index of refraction vs. temperature (dn/dT) of fused silica and calcium fluoride at the 193 nm wavelength has been developed in support of thermal modeling efforts for the development of 193 nm-based photolithographic exposure tools. The method, based upon grating lateral shear interferometry, uses a transmissive linear grating to divide a 193 nm laser beam into several beam paths by diffraction which propagate through separate identical material samples. One diffracted order passing through one sample overlaps the undiffracted beam from a second sample and forms interference fringes dependent upon the optical path difference between the two samples. Optical phase delay due to an index change from heating one of the samples causes the interference fringes to change sinusoidally with phase. The interferometer also makes use of AC phase measurement techniques through lateral translation of the grating. Results for several samples of fused silica and calcium fluoride are demonstrated.

  7. High-power gas-discharge excimer ArF, KrCl, KrF and XeCl lasers utilising two-component gas mixtures without a buffer gas

    NASA Astrophysics Data System (ADS)

    Razhev, A. M.; Kargapol'tsev, E. S.; Churkin, D. S.

    2016-03-01

    Results of an experimental study of the influence of a gas mixture (laser active medium) composition on an output energy and total efficiency of gas-discharge excimer lasers on ArF* (193 nm), KrCl* (222 nm), KrF* (248 nm) and XeCl* (308 nm) molecules operating without a buffer gas are presented. The optimal ratios of gas components (from the viewpoint of a maximum output energy) of an active medium are found, which provide an efficient operation of laser sources. It is experimentally confirmed that for gas-discharge excimer lasers on halogenides of inert gases the presence of a buffer gas in an active medium is not a necessary condition for efficient operation. For the first time, in two-component gas mixtures of repetitively pulsed gas-discharge excimer lasers on electron transitions of excimer molecules ArF*, KrCl*, KrF* and XeCl*, the pulsed energy of laser radiation obtained under pumping by a transverse volume electric discharge in a low-pressure gas mixture without a buffer gas reached up to 170 mJ and a high pulsed output power (of up to 24 MW) was obtained at a FWHM duration of the KrF-laser pulse of 7 ns. The maximal total efficiency obtained in the experiment with two-component gas mixtures of KrF and XeCl lasers was 0.8%.

  8. Overview on the high power excimer laser technology

    NASA Astrophysics Data System (ADS)

    Liu, Jingru

    2013-05-01

    High power excimer laser has essential applications in the fields of high energy density physics, inertial fusion energy and industry owing to its advantages such as short wavelength, high gain, wide bandwidth, energy scalable and repetition operating ability. This overview is aimed at an introduction and evaluation of enormous endeavor of the international high power excimer laser community in the last 30 years. The main technologies of high power excimer laser are reviewed, which include the pumping source technology, angular multiplexing and pulse compressing, beam-smoothing and homogenous irradiation, high efficiency and repetitive operation et al. A high power XeCl laser system developed in NINT of China is described in detail.

  9. Molecular design and synthesis of 3-oxocyclohexyl methacrylate for ArF and KrF excimer laser resist

    SciTech Connect

    Kozaki, Koji; Kaimoto, Yuko; Takahashi, Makoto

    1994-09-01

    The authors originally designed 3-oxocyclohexyl methacrylate (OCMA) for an acid-labile component in chemical amplification. The key concept of the molecular design of the 3-oxocyclohexyl substituent was the introduction of acidic protons at the {alpha}-position of the elimination site by using a ketone functional group. OCMA was synthesized by esterification of 1,3-cyclohexanediol and methacryloyl chloride followed by pyridinium dichromate oxidation. Using AIBN as an initiator, the authors also prepared poly(OCMA-co-AdMA) (AdMA: adamantyl methacrylate) by a thermally induced radical copolymerization of OCMA and AdMA. The resist comprises the copolymer and 10 wt % of triphenylsulfonium hexafluoroantimonate as a photoacid generator (PAG). This resist has high sensitivity, good thermal stability, good dry etch resistance, and good postexposure delay durability. Using a KrF excimer laser stepper (NA = 0.45) and 2-propanol mixed aqueous alkali developer, the authors obtained 0.3-{mu}m line and space patterns with this resist. A resist with 1 wt % of the PAG has an acceptable transmittance at 193 nm, proving that this resist is suitable for ArF excimer lithography. 29 refs., 10 figs., 2 tabs.

  10. Numbers Of Merit In Excimer Laser Reliability Analysis

    NASA Astrophysics Data System (ADS)

    Austin, Lindsay; Basting, Dirk; Kahlert, Hans-Jurgen; Rebhan, Ulrich; Muckenheim, Wolfgang

    1989-04-01

    Recent results confirm new advances in XeC1 excimer laser discharge design have achieved major milestones in reliability - 1010 pulses without replacing the thyratron, electrodes, capacitors or power supply. Other data on standard KrF excimer lasers allow statistical analysis of numbers of merit, including MTBF and maintenance intervals. Projections are made of operating costs and maintenance for both continuous operation and low duty cycle of two different size lasers with all major gases: XeCl, KrF and ArF.

  11. Excimer laser interaction with dentin of the human tooth

    NASA Technical Reports Server (NTRS)

    Hammond, Ernest C., Jr.; Gilliam, Ruth L.; Baker, George R.

    1989-01-01

    The use an excimer laser produced many unusual conical structures within the dentin of the inner part of the human tooth. By varying the frequency of the laser one can disperse the energy and cause more bleeding in laser surgery, but not destroy the cells associated with the incision. Therefore, the healing process will virtually be without scarring. Whereas, using the infrared laser the blood loss would be less, but the healing process would tend to be longer because cells are being destroyed due to the cauterization effect of the laser. The question is, are these structures produced as an interaction with the laser or are they an intrinsic part of the structure. The effects of the laser interaction upon dentin was studied, and in using electron microscopy the interaction of the excimer laser upon the tooth dentin and other various biological tissue is more clearly understood.

  12. Excimer laser processing of backside-illuminated CCDS

    NASA Technical Reports Server (NTRS)

    Russell, S. D.

    1993-01-01

    An excimer laser is used to activate previously implanted dopants on the backside of a backside-illuminated CCD. The controlled ion implantation of the backside and subsequent thin layer heating and recrystallization by the short wavelength pulsed excimer laser simultaneously activates the dopant and anneals out implant damage. This improves the dark current response, repairs defective pixels and improves spectral response. This process heats a very thin layer of the material to high temperatures on a nanosecond time scale while the bulk of the delicate CCD substrate remains at low temperature. Excimer laser processing backside-illuminated CCD's enables salvage and utilization of otherwise nonfunctional components by bringing their dark current response to within an acceptable range. This process is particularly useful for solid state imaging detectors used in commercial, scientific and government applications requiring a wide spectral response and low light level detection.

  13. Cleaning of large area by excimer laser ablation

    NASA Astrophysics Data System (ADS)

    Sentis, Marc L.; Delaporte, Philippe C.; Marine, Wladimir I.; Uteza, Olivier P.

    2000-01-01

    Surface removal technologies are being challenged from environmental and economic perspectives. This paper is concerned with laser ablation applied to large surface cleaning with an automatized excimer laser unit. The study focused on metallic surfaces that are oxidized and are representative of contaminated surfaces with radionuclides in a context of nuclear power plant maintenance. The whole system is described: laser, beam deliver, particle collection cell, real time control of cleaning processes. Results concerning surface laser interaction and substrate modifications are presented.

  14. Pulsed excimer laser processing for cost-effective solar cells

    NASA Technical Reports Server (NTRS)

    Wong, David C.

    1985-01-01

    The application of excimer laser in the fabrication of photovoltaic devices was investigated extensively. Processes included junction formation, laser assisted chemical vapor deposition metallization, and laser assisted chemical vapor deposition surface passivation. Results demonstrated that implementation of junction formation by laser annealing in production is feasible because of excellent control in junction depth and quality. Both metallization and surface passivation, however, were found impractical to be considered for manufacturing at this stage.

  15. Analytical Characterization of CFRP Laser Treated by Excimer Laser Radiation

    NASA Astrophysics Data System (ADS)

    Kreling, S.; Fischer, F.; Delmdahl, R.; Gäbler, F.; Dilger, K.

    Due to the increasing interest in lightweight structures, carbon-fiber reinforced plastics are increasingly applied, especially in the transportation industry. An interesting technology for joining these materials is adhesive bonding due to numerous advantages compared to conventional techniques like riveting. However, to achieve a strong and durable bond, surface pre-treatment is necessary to remove residues of release agents that are transferred to the surface during manufacturing. This paper describes analytical experiments, namely SEM and XPS, performed on CFRP surfaces pre-treated with 308 nm excimer laser radiation.

  16. Improved corrosion resistance of excimer laser treated stainless steel

    NASA Astrophysics Data System (ADS)

    Emmel, A.; Schubert, Emil; Barnikel, J.; Stiele, H. J.; Bergmann, Hans W.

    1994-09-01

    Excimer laser surface processing is well-known for material ablation, cleaning, deoxidation, smoothing or roughening. A typical industrial application is the polymer ablation for electronic components, however, the treatment of metals is only on the threshold of industrial use. A novel application reported here, may be an excimer treatment in air leading to oxide and nitrogen dissolution, resulting in an improved corrosion resistance. It is known from literature that corrosion resistance can be enhanced by laser surface alloying e.g. gas nitriding of Ti using CO2-lasers. However, all these techniques have the disadvantage of producing inhomogeneous layers. The aim of this study was to use the reactions during excimer laser irradiation of steel in air to produce layers in the thickness range of 0,1 to 2 micrometers with novel properties. Using the Siemens XP2020 excimer laser it was possible to scan technologically reasonable surface areas with energy densities in the range of 20 to 80 mJ/mm2 and several pulses per area. Steel sheets of 1.4541 (DIN) were irradiated in air and subsequently analyzed by XRD, SEM, TEM, AES and Mossbauer spectroscopy. The corrosion behavior was tested potentio-dynamically in 0,5 N H2SO4 and by gravimetric measurements of the weight loss. The XRD results showed, that the remaining delta-ferrite was eliminated. Both Mossbauer and Auger spectroscopy indicated a strong N- dissolution, hereby stabilizing the austenite. The TEM-investigations revealed fine dispersed oxides (chromites) and an increased dislocation density, resulting in pre-cellular arrangements after relaxation. Corrosion tests suggested the reduction of the material removal rates by a factor of 10 compared to untreated samples. The U(i) curves showed that after the excimer treatment less Cr is presented due to oxide formation in the surface layer. These Cr-oxides are the main reason for the improved corrosion resistance of excimer laser treated stainless steel.

  17. Nanocomposite liquids for 193 nm immersion lithography: a progress report

    NASA Astrophysics Data System (ADS)

    Chumanov, George; Evanoff, David D., Jr.; Luzinov, Igor; Klep, Viktor; Zdryko, Bogdan; Conley, Will; Zimmerman, Paul

    2005-05-01

    Immersion lithography is a new promising approach capable of further increasing the resolution of semiconductor devices. This technology requires the development of new immersion media that satisfy the following conditions: the media should have high refractive index, be transparent and photochemically stable in DUV spectral range. They should also be inert towards photoresists and optics and be liquid to permit rapid scanning. Here we propose and explore a novel strategy in which high refractive index medium is made of small solid particles suspended in liquid phases (nanocomposite liquids). The dielectric particles have high refractive index and the refractive index of nanocomposite liquids becomes volume weighted average between refractive indices of nanoparticles and the liquid phase. We investigate aluminum oxide (alumina) nanoparticles suspended in water. Alumina is known to have high (1.95) refractive index and low absorption coefficient at 193 nm. Alumina nanoparticles were prepared by chemical methods followed by removal of organic molecules left after hydrolysis reactions. Measurements of optical and reological properties of the nanocomposite liquid demonstrated potential advantage of this approach for 193 nm immersion lithography.

  18. High-index nanocomposite photoresist for 193-nm lithography

    NASA Astrophysics Data System (ADS)

    Bae, Woo Jin; Trikeriotis, Makros; Rodriguez, Robert; Zettel, Michael F.; Piscani, Emil; Ober, Christopher K.; Giannelis, Emmanuel P.; Zimmerman, Paul

    2009-03-01

    In immersion lithography, high index fluids are used to increase the numerical aperture (NA) of the imaging system and decrease the minimum printable feature size. Water has been used in first generation immersion lithography at 193 nm to reach the 45 nm node, but to reach the 38 and 32 nm nodes, fluids and resists with a higher index than water are needed. A critical issue hindering the implementation of 193i at the 32 nm node is the availability of high refractive index (n > 1.8) and low optical absorption fluids and resists. It is critical to note that high index resists are necessary only when a high refractive index fluid is in use. High index resist improves the depth of focus (DOF) even without high index fluids. In this study, high refractive index nanoparticles have been synthesized and introduced into a resist matrix to increase the overall refractive index. The strategy followed is to synthesize PGMEA-soluble nanoparticles and then disperse them into a 193 nm resist. High index nanoparticles 1-2 nm in diameter were synthesized by a combination of hydrolysis and sol-gel methods. A ligand exchange method was used, allowing the surface of the nanoparticles to be modified with photoresist-friendly moieties to help them disperse uniformly in the resist matrix. The refractive index and ultraviolet absorbance were measured to evaluate the quality of next generation immersion lithography resist materials.

  19. Generation of strongly coupled plasmas by high power excimer laser

    NASA Astrophysics Data System (ADS)

    Zhu, Yongxiang; Liu, Jingru; Zhang, Yongsheng; Hu, Yun; Zhang, Jiyan; Zheng, Zhijian; Ye, Xisheng

    2013-05-01

    (ultraviolet). To generate strongly coupled plasmas (SCP) by high power excimer laser, an Au-CH-Al-CH target is used to make the Al sample reach the state of SCP, in which the Au layer transforms laser energy to X-ray that heating the sample by volume and the CH layers provides necessary constraints. With aid of the MULTI-1D code, we calculate the state of the Al sample and its relationship with peak intensity, width and wavelength of laser pulses. The calculated results suggest that an excimer laser with peak intensity of the magnitude of 1013W/cm2 and pulse width being 5ns - 10ns is suitable to generate SCP with the temperature being tens of eV and the density of electron being of the order of 1022/cm-3. Lasers with shorter wavelength, such as KrF laser, are preferable.

  20. Laser plume dynamics during excimer laser nitriding of iron

    NASA Astrophysics Data System (ADS)

    Han, M.; Carpene, E.; Lieb, K. P.; Schaaf, Peter

    2003-11-01

    Laser nitriding of iron is an interesting phenomenon both in physics and industry. On the time scale of hundreds nanoseconds, high intensity (~108 W/cm2) pulsed excimer laser irradiation on iron in nitrogen atmosphere produced a thin iron nitride layer (thickness > 400 nm) with a mean nitrogen concentration exceeding 10 at which greatly improves the iron surface mechanical properties and the corrosion or erosion resistance. Laser plasma/plume plays a crucial role in the complicated interplay of the laser-plasma-metal system. Since the nitrogen pressure is one of the most important parameters determining the laser plume dynamics, a nitrogen pressure series ranging from 0.05 bar to 10 bar is conducted. The characteristic parameters of the nitrogen depth profile are extracted and their pressure dependence is qualitatively discussed. By isotopic experiments in 15N and natural nitrogen environment, the evolution of the nitrogen depth profile during laser nitriding process is successfully traced. Both of the experimental results suggested that a 1D laser supported combustion wave model is reasonable to describe the lasers plume dynamics.

  1. Novel technique for high-quality microstructuring with excimer lasers

    NASA Astrophysics Data System (ADS)

    Roth, Stephan; Geiger, Manfred

    2000-06-01

    Laser micromachining has become increasingly established in many microsystem applications during the past years. These new fields occasion higher demands on the quality of micromachiend devices combined with high resolution and working velocity. Due to the disadvantages of conventional excimer laser processing, a novel technique is required to meet these demands. The main problems of conventional excimer laser machining are the redeposition of ablated material on the irradiated work piece and the formation of a strong melting phase especially for metals. These difficulties greatly reduce the applicability of excimer laser material processing for manufacturing microsystems technology components. By applying a thin water film to the substrate surface, the redeposition of ablated material can be completely avoided, which results in a better quality of the microstructures. Usage of a water film, however, has proved to lead to a marked reduction of the ablation rate for the examined materials - ceramics and stainless steel. Therefore, one of the objectives of future research will be to raise the ablation rate in order to render excimer laser processing more interesting economically. Adding alcoholic additives, among others, has improved the wetting of the liquid films on the surface. The effect of the modified chemical composition of the liquid on ablation rate and structure quality for various materials is presented here.

  2. Excimer laser ablation of polymer-clay nanocomposites

    NASA Astrophysics Data System (ADS)

    Chang, I.-Ta

    The ablation behavior of Polystyrene-Organically Modified Montmorillonite (OMMT) nanocomposites was evaluated by measuring the weight loss induced by KrF excimer laser irradiation of the nanocomposite specimens under air atmosphere. The characteristic values of ablation, ablation threshold fluence and effective absorption coefficient for polystyrene and its naonocomposites were calculated based on the weight loss data. The effects of morphology due to spatial variation in injection molded samples are also discussed in this work. Results demonstrate that both the dispersion state and the concentration of clay play important roles in excimer laser ablation. The sensitivity of threshold fluence and absorption coefficient to dispersion state of OMMT depends on the clay concentration. The excimer laser induced surface micro/nano structure formation and modification of PS-Clay Nanocomposites at various OMMT concentrations were also investigated. Scanning electron microscopy, atomic force microscopy and Fourier Transform Infrared (FTIR) spectroscopy with attenuated total reflectance accessory were utilized to analyze the ablated surface. Results show that, in general, better dispersion of OMMT leads to less continuous surface structures and more pronounced carbonyl regions on FTIR spectra. Clay nanoparticles are exposed on ablated surfaces and affect surface structure formation after irradiation by laser. A mechanism for the formation of excimer laser induced surface structures on injection molded parts is thus proposed.

  3. Excimer-laser-induced oxidation of diborane: Formation and isolation of HBO, HB 18O AND H 3B 3O 3 in argon matrices

    NASA Astrophysics Data System (ADS)

    Ault, Bruce S.

    1989-05-01

    An excimer laser operating at 193 nm has been employed in conjunction with the matrix isolation technique to study the reaction of B 2H 6 with oxygen atoms. N 2O and O 2 were used as photolytic oxygen atom sources, and a number of oxidation products were detected. Absorptions near 750 and 1813 cm -1 were assigned to H 11BO; experiments with 18O led to production of HB 18O for the first time, and the identification of two of the fundamentals of this species. Also, H 3B 3O 3 was detected near 910, 1380 and 2610 cm -1. In addition, the most intense fundamental of BH 3 was tentatively identified at 1138 cm -1. These observations support the most recently postulated mechanism for the oxidation of diborane, and the suggested intermediacy of HBO in the process.

  4. Boron trichloride purification with a KrF excimer laser

    SciTech Connect

    Hyer, R.C.; Hartford, A. Jr.; Atencio, J.H.

    1980-01-01

    Selective ultraviolet photolysis using a KrF excimer laser has been used to substantially reduce the phosgene impurity in a binary mixture of boron trichloride and phosgene. Infrared spectroscopic analysis of the sample before and after irradiation shows that it is possible to highly purify commercially available boron trichloride with this technique.

  5. Analysis of glycosaminoglycans in rabbit cornea after excimer laser keratectomy

    PubMed Central

    Kato, T.; Nakayasu, K.; Ikegami, K.; Obara, T.; Kanayama, T.; Kanai, A.

    1999-01-01

    BACKGROUND/AIMS—The biochemical basis for the development of subepithelial opacity of the cornea after excimer laser keratectomy has yet to be fully defined. The aim of this study was to evaluate the alterations of glycosaminoglycans (GAGs) after excimer laser keratectomy.
METHODS—Rabbit corneas were harvested on days 5, 10, 20, and 30 after excimer laser photoablation. The amount of main disaccharide units was determined by high performance liquid chromatography (HPLC). In addition, immunohistochemical studies were performed on corneal sections 20 days after the ablation.
RESULTS—The concentrations of ΔDi-0S at 5 and 10 days were significantly lower than before the ablation. ΔDi-6S showed a significant increase 5 days after the ablation but ΔDi-4S did not show any significant change. There was a significant increase in ΔDi-HA at 20 and 30 days after ablation. In immunohistochemistry, the positive staining for ΔDi-6S and hyaluronic acid was observed in the subepithelial region. These immunohistochemical results were well correlated with the HPLC findings.
CONCLUSIONS—The increase in chondroitin-6 sulphate and hyaluronic acid may be related to corneal subepithelial opacity after excimer laser keratectomy.

 PMID:10216064

  6. High-index optical materials for 193nm immersion lithography

    NASA Astrophysics Data System (ADS)

    Burnett, John H.; Kaplan, Simon G.; Shirley, Eric L.; Horowitz, Deane; Clauss, Wilfried; Grenville, Andrew; Van Peski, Chris

    2006-03-01

    We report on our comprehensive survey of high-index UV optical materials that may enable extension of immersion lithography beyond a numerical aperture of 1.45. Band edge, refractive index, and intrinsic birefringence (IBR) at 193 nm determine basic viability. Our measurements of these properties have reduced the list of potential candidates to: ceramic spinel, lutetium aluminum garnet, and a class of germanium garnets. We discuss our measurements of the intrinsic properties of these materials and assess the present status of their material quality relative to requirements. Ceramic spinel has no significant IBR, but transmission and scatter for the best samples remain at least two orders of magnitude from specifications. Improving these would require a major development effort. Presently available lutetium aluminum garnet has material quality much closer to the specifications. However, the IBR is about three times the required value. The germanium garnets offer the possibility of a lower IBR, but a suitable candidate material has yet to be established.

  7. Excimer laser lead extraction catheter with increased laser parameters

    NASA Astrophysics Data System (ADS)

    Coe, M. Sean; Taylor, Kevin D.; Lippincott, Rebecca A.; Sorokoumov, Oleg; Papaioannou, Thanassis

    2001-05-01

    A fiber optic catheter connected to a pulsed excimer laser (308 nm) is currently used to extract chronically implanted pacemaker and defibrillator leads at Fluence of 60 mJ/mm2 and repetition rate of 40 Hz. The object of this study was to determine the effect of higher repetition rates (80 Hz) in the catheter's cutting performance. The penetration rate (micrometers /sec), and the associated mechanical and thermal effects were measured in soft (porcine myocardium) and hard tissue (bovine tendon) at 60 mJ/mm2-80 Hz, and were compared to the corresponding values at commercially available laser parameters (60 mJ/mm2-40 Hz). Ablation rates were measured with perforation experiments and the extent of thermal and mechanical damage was measured under polarized light microscopy. For hard (soft) tissue, the laser catheter demonstrated penetration speed of 106 +/- 32 (302 +/- 101) micrometers /sec at 40 Hz and 343 +/- 120 (830 +/- 364) micrometers /sec at 80 Hz. Maximum extent of thermal effects at 40 Hz and 80 Hz was 114 +/- 35 micrometers (72 +/- 18) and 233 +/- 63 micrometers (71 +/- 16) respectively. Maximum extent of mechanical effects at 40 Hz and 80 Hz was 188 +/- 63 micrometers (590 +/- 237) and 386 +/- 100 micrometers (767 +/- 160) respectively. In vitro testing of the laser catheter with 80 Hz laser parameters has demonstrated increased penetration speed in both soft and hard fibrous tissue, while maintaining associated thermal and mechanical effects within limited ranges.

  8. Excimer laser ophthalmic surgery: evaluation of a new technology.

    PubMed Central

    Infeld, D. A.; O'Shea, J. G.

    1998-01-01

    The aim of this article is to provide information and an overview of the potential risks and benefits of excimer laser surgery, a new and promising technique in ophthalmic surgery. Although this review concentrates on the use of the laser for refractive purposes, novel therapeutic techniques are also discussed. It is hoped that this will enable general practitioners, optometrists and physicians to provide appropriate advice and counselling for patients. Images Figure 1 Figure 2 Figure 3 Figure 4 PMID:10211324

  9. Excimer Laser Ablation of Egg Tempera Paints and Varnishes

    NASA Astrophysics Data System (ADS)

    Morais, P. J.; Bordalo, R.; Santos, L. dos; Marques, S. F.; Salgueiredo, E.; Gouveia, H.

    In this work a series of egg tempera paint and varnish systems have been prepared, artificially aged and irradiated with KrF excimer laser at a wavelength of 248 nm. The samples were prepared with pure pigments and selected mixtures. It was found that, for some pigments, the colour changed upon laser irradiation even at low energy densities, below the ablation threshold while for other inorganic pigmented egg temperas the degree of discoloration is very small at moderate fluence of ˜0.30 J cm?2. The varnish systems did not present signs of discoloration. The thickness, superficial roughness and magnitude of the colour changes of the samples were measured. X-ray diffraction, Raman spectroscopy and UV/visible spectroscopy were used in order to investigate the changes induced by the KrF excimer laser radiation.

  10. Lactones in 193 nm resists: What do they do?

    NASA Astrophysics Data System (ADS)

    Ito, Hiroshi; Truong, Hoa D.; Brock, Phil J.

    2008-03-01

    Lactones are almost ubiquitously employed in 193 nm resists to increase the polarity of hydrophobic alicyclic polymers. What else do lactones do in 193 nm resists? We studied the behavior of methacrylate (MA) resists consisting of different protecting groups, hexafluoroalcohols, and norbornane lactone methacrylate (NLM, 2-oxo-3-oxatricyclo[4.2.1.04,8]nonan-5-yl methacrylate). When the protecting group is large [ethylcyclooctyl (ECO) and methyladamantyl (MAd)], thinning of the resist film that occurs in highly exposed areas upon postexposure bake (PEB) is significantly smaller than what is expected from the polymer composition. When the concentration of isopropylhexafluoroalcohol methacrylate (iPrHFAMA) is increased in the ECOMA-NLM polymer, the thinning increases and reaches 100% of theory and the ECOMA-norbornenehexafluoroalcohol methacrylate (NBHFAMA) resist loses quantitative thickness in highly-exposed areas upon PEB at 90 °C. This indicates that small lactones which are more basic than esters can trap deprotection fragments especially when the protecting group is large. Such entrapment was detected by IR spectroscopy and also observed at temperatures as high as 200 °C in thermogravimetric analysis (TGA). Incorporation of lactone appears to decrease the bake temperature sensitivity and the sensitivity of the resist perhaps due to trapping of photochemically generated acids by basic lactone. The lactone ring can be hydrolyzed during aqueous base development but does not seem to affect the dissolution rate, indicating that hydrolysis occurs in aqueous base solution after dissolution. Poly(methacrylic acid-NLM) dissolves as fast as poly(methacrylic acid) in 0.26 N tetramethylammonium hydroxide (TMAH) aqueous solution. While exposed P(ECOMA 47-NLM 53) resist dissolves in 0.26 N developer at about the same rate as authentically prepared poly(methacrylic acid 47-NLM 53), the dissolution rate of highly-exposed P(MAdMA 44-NLM 56) resist is much slower, indicating

  11. Adamantane based molecular glass resist for 193 nm lithography

    NASA Astrophysics Data System (ADS)

    Tanaka, Shinji; Ober, Christopher K.

    2006-03-01

    As the feature dimensions decreases there are several issues must be addressed to implement the corresponding technology in high volume production. Line width roughness (LWR) and line edge roughness (LER) are the most important technological issue arises as the feature dimension decreases. In order to improve both of LWR and LER, we have developed novel low molecular weight glass resists as high performance resist materials. These molecular glass resists are adamantane derivatives and are highly transparent at 193 nm. We have prepared series of new molecular glass resists based on adamantane core carrying acetal and ester protecting groups. Particularly, adamantane core derivatives of tripod structure were investigated in detail. Several compositions of them showed glass transition temperatures (Tg) above 120 °C. Lithographic evaluation confirmed their high sensitivity at 254 nm and e-beam exposure. It also resolved feature size as small as 200 nm line/space when it evaluated using e-beam lithography. These new molecular glass resists also have high plasma-etch resistance.

  12. Modeling chemically amplified resists for 193-nm lithography

    NASA Astrophysics Data System (ADS)

    Croffie, Ebo H.; Cheng, Mosong; Neureuther, Andrew R.; Houlihan, Francis M.; Cirelli, Raymond A.; Sweeney, James R.; Dabbagh, Gary; Watson, Pat G.; Nalamasu, Omkaram; Rushkin, Ilya L.; Dimov, Ognian N.; Gabor, Allen H.

    2000-06-01

    Post exposure bake (PEB) models in the STORM program have been extended to study pattern formation in 193 nm chemically amplified resists. Applications to resists formulated with cycloolefin-maleic anhydride copolymers, cholate based dissolution inhibitor, nonaflate photoacid generator and base quencher are presented. The PEB modeling is based on the chemical and physical mechanisms including the thermally induced deprotection reaction, acid loss due to base neutralization and protected-sites-enhanced acid diffusion. Simplifying assumptions are made to derive analytical expressions for PEB. The model parameters are extracted from the following experiments. UV-visible spectroscopy is used to extract the resist absorbance parameters. The generation of acid is monitored using the method of 'base additions.' The extent of deprotection that occurs during the bake is determined by monitoring the characteristic FTIR absorbance band around 1170 cm-1 over a range of exposure doses and bake temperatures. Diffusion parameters are extracted from line end shortening (LES) measurements. These parameters are optimized using the Method of Feasible Directions algorithm. Application results show good agreement with experimental data for different LES features.

  13. Excimer laser coronary angioplasty: relative risk analysis of clinical results

    NASA Astrophysics Data System (ADS)

    Bittl, John A.

    1992-08-01

    Reports of successful use of excimer laser coronary angioplasty for complex coronary artery disease abound, yet firm indications for its use have not been defined. We attempted to treat 858 coronary stenoses in 764 consecutive patients (mean age 61 years; range 32 - 91 years; 75% men; 76% with Class III or IV angina) with excimer laser angioplasty at 308 nm. Successful treatment was achieved in 86% of patients, as indicated by excimer laser angioplasty, we used relative risk analysis. This showed that certain angiographic features, such as lesions at a vessel bifurcation (odds ratio, OR equals 0.46; 95% confidence interval 0.23, 0.88; P equals 0.017;) or in a tortuous segment (OR equals 0.54; 95% CI equals 0.34, 0.88; P equals 0.041), have decreased likelihood of clinical success. On the other hand, ostial stenoses (OR equals 1.06; 95% CI equals 0.44, 2.56, P equals 0.903) and saphenous vein graft lesions (OR equals 2.17; 95% CI equals 0.98, 4.82; P equals 0.051) have acceptable success rates. Diffuse disease (> 20 mm), total occlusions and calcified lesions were treated as successfully as all other lesion types. Successful treatment with excimer laser coronary angioplasty was also achieved in almost all patients (15/16) who had a prior unsuccessful attempt at balloon angioplasty in the lesion was crossed with a guidewire yet resists either balloon catheter passage or full dilatation. Follow-up angiography was obtained in 70% of eligible patients. Angiographic restenosis, defined by > 50% stenosis, was seen in 60% of patients. Relative risk analysis showed an increased risk of restenosis when adjunctive balloon angioplasty was not used (OR equals 1.68; 95% CI equals 1.02, 2.28; P equals 0.039). Other variables known to affect the outcome of balloon angioplasty, such as lesion length or stenosis in degenerated saphenous vein bypass graft, did not influence the

  14. Triggering Excimer Lasers by Photoionization from Corona Discharges

    NASA Astrophysics Data System (ADS)

    Xiong, Zhongmin; Duffey, Thomas; Brown, Daniel; Kushner, Mark

    2009-10-01

    High repetition rate ArF (192 nm) excimer lasers are used for photolithography sources in microelectronics fabrication. In highly attaching gas mixtures, preionization is critical to obtaining stable, reproducible glow discharges. Photoionization from a separate corona discharge is one technique for preionization which triggers the subsequent electron avalanche between the main electrodes. Photoionization triggering of an ArF excimer laser sustained in multi-atmosphere Ne/Ar/F2/Xe gas mixtures has been investigated using a 2-dimensional plasma hydrodynamics model including radiation transport. Continuity equations for charged and neutral species, and Poisson's equation are solved coincident with the electron temperature with transport coefficients obtained from solutions of Boltzmann's equation. Photoionizing radiation is produced by a surface discharge which propagates along a corona-bar located adjacent to the discharge electrodes. The consequences of pulse power waveform, corona bar location, capacitance and gas mixture on uniformity, symmetry and gain of the avalanche discharge will be discussed.

  15. 193-nm full-field step-and-scan prototype at MIT Lincoln Laboratory

    NASA Astrophysics Data System (ADS)

    Hibbs, Michael S.; Kunz, Roderick R.

    1995-05-01

    Optical lithography at a 193-nm exposure wavelength has been under development at MIT Lincoln Laboratory for several years, supported by ARPA's Advanced Lithography Program. As part of this program, a prototype 193-nm full-field step-and-scan lithographic exposure system was built and installed in the clean-room facilities of MIT Lincoln Laboratory. This exposure system has now been in use for one year, supporting a program of photoresist and lithographic process development at 193 nm. This paper describes the characteristics of the exposure system and some of the advances in 193-nm lithography that have been achieved with the system.

  16. 308-nm Excimer laser treatment of palmoplantar psoriasis.

    PubMed

    Goldberg, David J; Chwalek, Jennifer; Hussain, Mussarrat

    2011-04-01

    Psoriasis is a chronic inflammatory condition affecting 1-3% of the population. The incidence of palmoplantar involvement has been estimated to be between 2.8% and 40.9%. Significant psychosocial distress and difficulty performing activities of daily living can result. Treatment is often challenging. Traditional treatments include topical steroids, anthralin, calcipotriene, PUVA, methotrexate, cyclosporine, retinoids and biologics. In this case series, we report our success with the 308-nm excimer laser in the treatment of palmoplantar psoriasis. PMID:21401376

  17. Nebulae at keratoconus--the result after excimer laser removal.

    PubMed

    Fagerholm, P; Fitzsimmons, T; Ohman, L; Orndahl, M

    1993-12-01

    Ten patients underwent excimer laser ablation due to nebula formation at keratoconus. The nebulae interfered significantly with contact lens fit or wearing time. The mean follow-up time in these patients was 16.5 months. Following surgery all patients could be successfully fitted with a contact lens and thereby obtain good visual acuity. Furthermore, contact lens wearing time was 8 hours or more in all cases. In 2 patients the nebulae recurred but were successfully retreated. PMID:8154261

  18. Assessment of the Suitability of Excimer Lasers in Treating Onychomycosis

    NASA Astrophysics Data System (ADS)

    Kymplová, Jaroslava; Jelínek, Miroslav; Urzová, Jana; Mikšovský, Jan; Dušek, Karel; Bauerová, Lenka

    2014-04-01

    Since it is known that UV-C radiation kills fungus, we wanted to verify the hypothesis that the use of excimer laser could be an alternative method for treating onychomycosis - nail fungus. The aim of the first stage of this work was to determine the transmission, reflection and absorption of nails. In the following stage we focused on irradiation of fungi. Our final task is to assess whether it is possible to determine the parameters of radiation (a total dose,a dose per pulse frequency, a repetition rate, a number of pulses) for which the elimination of fungi would be the most effective but without damaging the nail and soft tissue underneath it. The results so far have showed that UV-C radiation does not pass through a fingernail to such an extent that it could damage the soft tissue beneath it. Fungi are destroyed by the application of only small doses of radiation using the excimer laser. Additional measurements will be required to determine the modulation parameters of the excimer laser radiation for the treatment of onychomycosis.

  19. Inline detection of Chrome degradation on binary 193nm photomasks

    NASA Astrophysics Data System (ADS)

    Dufaye, Félix; Sippel, Astrid; Wylie, Mark; García-Berríos, Edgardo; Crawford, Charles; Hess, Carl; Sartelli, Luca; Pogliani, Carlo; Miyashita, Hiroyuki; Gough, Stuart; Sundermann, Frank; Brochard, Christophe

    2013-09-01

    193nm binary photomasks are still used in the semiconductor industry for the lithography of some critical layers for the nodes 90nm and 65nm, with high volumes and over long periods. However, these 193nm binary photomasks can be impacted by a phenomenon of chrome oxidation leading to critical dimensions uniformity (CDU) degradation with a pronounced radial signature. If not detected early enough, this CDU degradation may cause defectivity issues and lower yield on wafers. Fortunately, a standard cleaning and repellicle service at the mask shop has been demonstrated as efficient to remove the grown materials and get the photomask CD back on target.Some detection methods have been already described in literature, such as wafer CD intrafield monitoring (ACLV), giving reliable results but also consuming additional SEM time with less precision than direct photomask measurement. In this paper, we propose another approach, by monitoring the CDU directly on the photomask, concurrently with defect inspection for regular requalification to production for wafer fabs. For this study, we focused on a Metal layer in a 90nm technology node. Wafers have been exposed with production conditions and then measured by SEM-CD. Afterwards, this photomask has been measured with a SEM-CD in mask shop and also inspected on a KLA-Tencor X5.2 inspection system, with pixels 125 and 90nm, to evaluate the Intensity based Critical Dimension Uniformity (iCDU) option. iCDU was firstly developed to provide feed-forward CDU maps for scanner intrafield corrections, from arrayed dense structures on memory photomasks. Due to layout complexity and differing feature types, CDU monitoring on logic photomasks used to pose unique challenges.The selection of suitable feature types for CDU monitoring on logic photomasks is no longer an issue, since the transmitted intensity map gives all the needed information, as shown in this paper. In this study, the photomask was heavily degraded after more than 18,000 300

  20. Automatic alignment of double optical paths in excimer laser amplifier

    NASA Astrophysics Data System (ADS)

    Wang, Dahui; Zhao, Xueqing; Hua, Hengqi; Zhang, Yongsheng; Hu, Yun; Yi, Aiping; Zhao, Jun

    2013-05-01

    A kind of beam automatic alignment method used for double paths amplification in the electron pumped excimer laser system is demonstrated. In this way, the beams from the amplifiers can be transferred along the designated direction and accordingly irradiate on the target with high stabilization and accuracy. However, owing to nonexistence of natural alignment references in excimer laser amplifiers, two cross-hairs structure is used to align the beams. Here, one crosshair put into the input beam is regarded as the near-field reference while the other put into output beam is regarded as the far-field reference. The two cross-hairs are transmitted onto Charge Coupled Devices (CCD) by image-relaying structures separately. The errors between intersection points of two cross-talk images and centroid coordinates of actual beam are recorded automatically and sent to closed loop feedback control mechanism. Negative feedback keeps running until preset accuracy is reached. On the basis of above-mentioned design, the alignment optical path is built and the software is compiled, whereafter the experiment of double paths automatic alignment in electron pumped excimer laser amplifier is carried through. Meanwhile, the related influencing factors and the alignment precision are analyzed. Experimental results indicate that the alignment system can achieve the aiming direction of automatic aligning beams in short time. The analysis shows that the accuracy of alignment system is 0.63μrad and the beam maximum restoration error is 13.75μm. Furthermore, the bigger distance between the two cross-hairs, the higher precision of the system is. Therefore, the automatic alignment system has been used in angular multiplexing excimer Main Oscillation Power Amplification (MOPA) system and can satisfy the requirement of beam alignment precision on the whole.

  1. Microstructure of magnesium fluoride films deposited by boat evaporation at 193 nm.

    PubMed

    Liu, Ming-Chung; Lee, Cheng-Chung; Kaneko, Masaaki; Nakahira, Kazuhide; Takano, Yuuichi

    2006-10-01

    Single layer magnesium fluoride (MgF2) was deposited on fused-silica substrates by a molybdenum boat evaporation process at 193 nm. The formation of various microstructures in relation to the different substrate temperatures and deposition rates were investigated. The relation between these microstructures (including cross-sectional morphology, surface roughness, and crystalline structures), the optical properties (including refractive index and optical loss) and stress, were all investigated. It was found that the laser-induced damage threshold (LIDT) would be affected by the microstructure, optical loss, and stress of the thin film. To obtain a larger LIDT value and better optical characteristics, MgF2 films should be deposited at a high substrate temperature (300 degrees C) and at a low deposition rate (0.05 nm s(-1)). PMID:16983421

  2. Microstructure of magnesium fluoride films deposited by boat evaporation at 193 nm

    NASA Astrophysics Data System (ADS)

    Liu, Ming-Chung; Lee, Cheng-Chung; Kaneko, Masaaki; Nakahira, Kazuhide; Takano, Yuuichi

    2006-10-01

    Single layer magnesium fluoride (MgF2) was deposited on fused-silica substrates by a molybdenum boat evaporation process at 193 nm. The formation of various microstructures in relation to the different substrate temperatures and deposition rates were investigated. The relation between these microstructures (including cross-sectional morphology, surface roughness, and crystalline structures), the optical properties (including refractive index and optical loss) and stress, were all investigated. It was found that the laser-induced damage threshold (LIDT) would be affected by the microstructure, optical loss, and stress of the thin film. To obtain a larger LIDT value and better optical characteristics, MgF2 films should be deposited at a high substrate temperature (300 °C) and at a low deposition rate (0.05 nm s-1).

  3. Photoinduced absorption and refractive-index induction in phosphosilicate fibres by radiation at 193 nm

    SciTech Connect

    Rybaltovsky, A A; Sokolov, V O; Plotnichenko, V G; Lanin, Aleksei V; Semenov, S L; Dianov, Evgenii M; Gur'yanov, A N; Khopin, V F

    2007-04-30

    The photoinduced room-temperature-stable increase in the refractive index by {approx}5x10{sup -4} at a wavelength of 1.55 {mu}m was observed in phosphosilicate fibres without their preliminary loading with molecular hydrogen. It is shown that irradiation of preliminary hydrogen-loaded fibres by an ArF laser at 193 nm enhances the efficiency of refractive-index induction by an order of magnitude. The induced-absorption spectra of preforms with a phosphosilicate glass core and optical fibres fabricated from them are studied in a broad spectral range from 150 to 5000 nm. The intense induced-absorption band ({approx}800 cm{sup -1}) at 180 nm is found, which strongly affects the formation of the induced refractive index. The quantum-chemical model of a defect related to this band is proposed. (optical fibres)

  4. Surface Structuring of CFRP by using Modern Excimer Laser Sources

    NASA Astrophysics Data System (ADS)

    Fischer, F.; Kreling, S.; Dilger, K.

    High demands for lightweight construction can be attained by the use of carbon fiber-reinforced plastics (CFRP) including one major challenge: the joining technology. Adhesive bonding may allow an increased utilization of the lightweight potential of CFRP. But this technology requires a surface pre-treatment because of residues of release agents. This paper describes surface pre-treatment of CFRP specimens by using modern excimer laser and the mechanical tests that compare the achieved strength to manually abraded ones. The laser process is suitable for achieving cohesive failure within the adhesive and bond strengths in the magnitude of the abraded specimen.

  5. Chemical surface modification of fluorocarbon polymers by excimer laser processing

    NASA Astrophysics Data System (ADS)

    Niino, Hiroyuki; Yabe, Akira

    1996-04-01

    Surface of poly(tetrafluoroethylene) [PTFE] film was modified chemically by an ArF excimer laser-induced reaction in a hydrazine gas atmosphere. The polymer surface modified upon the irradiation of 1000 pulses at 27 mJ cm -2, which was a fairly lower fluence than the ablation threshold for usual polymer films, showed hydrophilicity (contact angle for water: 30°) enough to be metallized by chemical plating. The mechanism for chemical surface modification was investigated by FTIR, XPS, and SIMS analyses. The laser-treated PTFE film was metallized by a chemical plating process. These processes will be used to fabricate printed wiring boards for high frequency electronics.

  6. Photodissociation dynamics of 2-nitropropane and 2-methyl-2-nitropropane at 248 and 193 nm.

    PubMed

    Sengupta, Sumana; Indulkar, Yogesh; Kumar, Awadhesh; Dhanya, Suresh; Naik, Prakash Dattatray; Bajaj, Parma Nand

    2008-12-11

    Dynamics of formation of electronically excited NO2 and formation of OH fragment, during photo dissociation of 2-nitropropane (NP) and 2-methyl-2-nitropropane (MNP), were investigated at 193 and 248 nm. The radiative lifetime of the electronically excited NO2 fragment, observed at 193 nm, was measured to be 1.2 ( 0.1 micros and the rate coefficient of quenching of its emission by MNP was measured as (2.7 ( 0.1) x 10(-10) molecule(-1) cm3 s(-1). Formation of the ground electronic state of OH was confirmed in both molecules. State selective laser induced fluorescence technique was used to detect the nascent OH (X 2Pi, v'', J'') fragments in different ro-vibrational states, and to obtain information on energy partitioning. Though MNP and NP differ in the types of the available H atoms, the dynamics of OH formation is found to be the same in both. The relative population in different rotational states does not follow Boltzmann equilibrium distribution in both the molecules at 193 and 248 nm. The translational energies of the OH fragments, calculated from the Doppler width, are 21.2 ( 7.2 and 25.0 ( 2.5 kcal mol-1 for NP at 248 and 193 nm, respectively. The translational energies of the OH fragments, in the case of MNP, are found to be lower, 17.5 ( 4.1 and 22.0 ( 3.2 kcal mol-1,respectively, at 248 nm 193 nm. These results are compared with the earlier reports on photodissociation of nitromethane (NM), nitroethane (NE), and other nitroalkanes. All possible dissociation pathways of these molecules--NM, NE, NP, and MNPs leading to the formation of the OH fragment were investigated computationally, with geometry optimization at the B3LYP/6-311+G(d,p) level and energy calculation at the MP4(SDQ)/6-311+G (d,p) level. The results suggest that in NM, OH is formed after isomerization to CH2N(OH)O, whereas in all other cases OH is formed from HONO, a primary product of molecular elimination of nitroalkanes, formed with sufficient internal energy. PMID:19053556

  7. Pixel diamond detectors for excimer laser beam diagnostics

    NASA Astrophysics Data System (ADS)

    Girolami, M.; Allegrini, P.; Conte, G.; Salvatori, S.

    2011-05-01

    Laser beam profiling technology in the UV spectrum of light is evolving with the increase of excimer lasers and lamps applications, that span from lithography for VLSI circuits to eye surgery. The development of a beam-profiler, able to capture the excimer laser single pulse and process the acquired pixel current signals in the time period between each pulse, is mandatory for such applications. 1D and 2D array detectors have been realized on polycrystalline CVD diamond specimens. The fast diamond photoresponse, in the ns time regime, suggests the suitability of such devices for fine tuning feedback of high-power pulsed-laser cavities, whereas solar-blindness guarantees high performance in UV beam diagnostics, also under high intensity background illumination. Offering unique properties in terms of thermal conductivity and visible-light transparency, diamond represents one of the most suitable candidate for the detection of high-power UV laser emission. The relatively high resistivity of diamond in the dark has allowed the fabrication of photoconductive vertical pixel-detectors. A semitransparent light-receiving back-side contact has been used for detector biasing. Each pixel signal has been conditioned by a multi-channel read-out electronics made up of a high-sensitive integrator and a Σ-Δ A/D converter. The 500 μs conversion time has allowed a data acquisition rate up to 2 kSPS (Sample Per Second).

  8. Histological study of excimer laser on carotid artery

    NASA Astrophysics Data System (ADS)

    Chavantes, Maria C.; Pasqualucci, C. A.; Zamorano, Lucia J.

    1992-06-01

    The employment of photoablative effect on coronary artery angioplasty has been a new exciting field as a treatment option. Guided by good results in the literature, our group decided to study the laser/tissue interaction on carotid arteries with the intent of a less invasive treatment of intracranial and extracranial obstructed disease in vascular neurosurgery. We studied human cartoid arteries from ten male autopsy specimens with an average age of 53 years (34 - 37 years old) which a total of 22 laser applications were performed. Using the same repetition rate and energy, 20 Hz and 30 mJ, we compared the effect of the laser energy on 'normal' and 'pathologic' areas of the carotid arteries. The pathologic specimens, presenting calcified and non-calcified plaques, the same as the macroscopical 'normal' specimens, were submitted to the energy of the Excimer Laser with 308 nm wavelength. The laser beam was delivered perpendicularly through continuous flushing of saline on the targeted artery wall varying from 200 to 400 pulses. Histological studies were done and statistical analysis was performed. The results showed that the depth of penetration varied from 113 micrometers to 1200 micrometers , with a width of the lesion ranging from 150 micrometers - 1500 micrometers . In our study we found that the range between non-effective and destructive effect caused by the laser was around 400 pulses. We encountered minimal degree of carbonization while lasering on calcified plaques. We concluded that Excimer laser is a feasible and secure tool to prevent thermical complications of laser treatment, which will allow neurosurgeons in the future athermic laser angioplasty. Progress in this field must rely on further in vitro and in vivo research, before it can be clinically applied as well as improvements in delivery systems.

  9. Three-body dissociations: The photodissociation of dimethyl sulfoxide at 193 nm

    SciTech Connect

    Blank, D.A.; North, S.W.; Stranges, D.

    1997-04-01

    When a molecule with two equivalent chemical bonds is excited above the threshold for dissociation of both bonds, how the rupture of the two bonds is temporally coupled becomes a salient question. Following absorption at 193 nm dimethyl sulfoxide (CH{sub 3}SOCH{sub 3}) contains enough energy to rupture both C-S bonds. This can happen in a stepwise (reaction 1) or concerted (reaction 2) fashion where the authors use rotation of the SOCH{sub 3} intermediate prior to dissociation to define a stepwise dissociation: (1) CH{sub 3}SOCH{sub 3} {r_arrow} 2CH{sub 3} + SO; (2a) CH{sub 3}SOCH{sub 3} {r_arrow} CH{sub 3} + SOCH{sub 3}; and (2b) SOCH{sub 3} {r_arrow} SO + CH{sub 3}. Recently, the dissociation of dimethyl sulfoxide following absorption at 193 nm was suggested to involve simultaneous cleavage of both C-S bonds on an excited electronic surface. This conclusion was inferred from laser induced fluorescence (LIF) and resonant multiphoton ionization (2+1 REMPI) measurements of the internal energy content in the CH{sub 3} and SO photoproducts and a near unity quantum yield measured for SO. Since this type of concerted three body dissociation is very interesting and a rather rare event in photodissociation dynamics, the authors chose to investigate this system using the technique of photofragment translational spectroscopy at beamline 9.0.2.1. The soft photoionization provided by the VUV undulator radiation allowed the authors to probe the SOCH{sub 3} intermediate which had not been previously observed and provided good evidence that the dissociation of dimethyl sulfoxide primarily proceeds via a two step dissociation, reaction 2.

  10. The interaction of 193 nm excimer laser radiation with single-crystal zinc oxide: Generation of long lived highly excited particles with evidence of Zn Rydberg formation

    SciTech Connect

    Khan, Enamul H.; Langford, S. C.; Dickinson, J. T.; Boatner, L. A.

    2014-08-28

    In past studies, we have observed copious emissions of ionic and atomic Zn from single-crystal ZnO accompanying irradiation of single-crystal ZnO with 193-nm excimer laser irradiation at fluences below the onset of optical breakdown. The Zn{sup +} and ground state Zn° are studied using time-of-flight techniques and are mass selected using a quadrupole mass spectrometer. Simultaneously, we have observed emitted particles that are detectable with a Channeltron electron multiplier but cannot be mass selected. It is a reasonable hypothesis that these particles correspond to a neutral atom or molecule in highly excited long lived states. We provide strong evidence that they correspond to high lying Rydberg states of atomic Zn. We propose a production mechanism involving laser excitation via a two photon resonance excitation of Zn°.

  11. Three years of clinical experiences on excimer laser angioplasty

    NASA Astrophysics Data System (ADS)

    Viligiardi, Riccardo; Galiberti, Sandra; Pini, Roberto; Salimbeni, Renzo

    1992-03-01

    We report here the experience of our multidisciplinary group that has been working since 1986 on excimer laser angioplasty. After having selected the excimer laser between the available sources because of the negligible lesions left on the residual tissue, we had the purpose to develop a suitable laser and catheter system. Neglecting here all the preliminary studies, we outline only a typical phenomenon related to the energy delivery and useful for the comprehension of the recanalization process. The energy emitted by every single fiber determines, under a certain threshold, independent recanalized channels in the plaque with residual flaps. At a higher energy level the overposition of the lobes, due to the intrinsic divergence, up to the recanalization in a single large channel. In our opinion this condition is crucial in the design of the catheters to obtain an optical instead of a mechanical recanalization. The biological experimentation conducted during the preliminary tests on human hearts obtained from transplants or cadavers, convinced us that the correct goal to pursue was unique laser angioplasty without the need for further balloon dilation.

  12. Excimer laser photorefractive keratectomy with different ablation zones.

    PubMed

    Hassan, Z; Lampé, Z; Békési, L; Berta, A

    1997-01-01

    In this study we would like to introduce the excimer laser, and to demonstrate our results and complications by using different ablation zones during photorefractive keratectomy (PRK) in the correction of myopia and astigmatismus. In 1996 we performed photorefractive keratectomy on 100 myopic eyes of 52 patients (28 females, 24 males). Mean age was 26.21 years (ranged from 19 to 54 years). The preoperative refraction ranged from -1.0 D to -18.0 Diopters. The diameter of the ablation zones were between 5 and 6.5 mm. We evaluated the results and the complications of the surgeries of 100 eyes which were performed with Schwind keratom F excimer laser. After 2 days, 1 week, 1 month, 3 months, and 6 months postoperatively we tested the best uncorrected and corrected visual acuities, and performed intraocular pressure measurement, slit lamp examination as well as corneal topography. The postoperative refractions were between +/- 0.5 to +/- 1.0 Diopters. After six months postoperatively the slit lamp examination showed that 80% of the patients had no corneal haze while 20% had stage I (Hanna) corneal haze. The smaller the diameter of the ablation zone was, the more pronounced the corneal haze and the night-glare were. The photorefractive excimer laser keratectomy is judged to be a safe method, although it might have some side-effects. The different ablation zones of this treatment means an important modification, that not only allows the method to meet the individual requirements, but reduces the chance of the complications as well. Based on the authors' experiences PRK for moderate myopia with large diameter ablation zones appears more predictable than than with smaller ablation zone diameters. PMID:9408312

  13. Blunt atrial transseptal puncture using excimer laser in swine

    PubMed Central

    Elagha, Abdalla A.; Kim, Ann H.; Kocaturk, Ozgur; Lederman, Robert J.

    2009-01-01

    Objectives We describe a new approach that may enhance safety of atrial transseptal puncture, using a commercially available laser catheter that is capable of perforation only when energized. We test this approach in swine. Background Despite wide application, conventional needle transseptal puncture continues to risk inadvertent non-target perforation and its consequences. Methods We used a commercial excimer laser catheter (0.9mm Clirpath, Spectranetics). Perforation force was compared in vitro with a conventional Brockenbrough needle. Eight swine underwent laser transseptal puncture under X-ray fluoroscopy steered using a variety of delivery catheters. Results The 0.9mm laser catheter traversed in vitro targets with reduced force compared with a Brockenbrough needle. In vitro, the laser catheter created holes that were 25–30% larger than the Brockenbrough needle. Laser puncture of the atrial septum was successful and accurate in all animals, evidenced by oximetry, pressure, angiography, and necropsy. The laser catheter was steered effectively using a modified Mullins introducer sheath and using two different deflectable guiding catheters. The mean procedure time was 15 ± 6 minutes, with an average 3.0 ± 0.8 seconds of laser activation. There were no adverse sequelae after prolonged observation. Necropsy revealed discrete 0.9mm holes in all septae. Conclusion Laser puncture of the interatrial septum is feasible and safe in swine, using a blunt laser catheter that perforates tissues in a controlled fashion. PMID:17896413

  14. Multifiber excimer laser catheter design strategies for various medical applications

    NASA Astrophysics Data System (ADS)

    Verdaasdonck, Rudolf M.; van Swol, Christiaan F. P.; van Leeuwen, Ton G. J. M.; Tulleken, Cees A. F.; Boon, Tom A.

    1994-07-01

    For the XeCl Excimer laser (308 nm, 115 ns), special design multifiber laser catheters were developed and theoretically as well as experimentally evaluated. Monte Carlo simulations showed that the penetration depth of 308 nm XeCl excimer light varied from 50 to 200 micrometers for fiber diameters from 50 to 550 micrometers and larger. Tissue ablation is expected to be restricted to this irradiated area. In order to ablate larger tissue areas, a flexible bundle of fibers is used introducing gaps in the irradiance distribution due to dead space in between the individual fibers. Multifiber catheters were developed for a unique neurosurgery bypass procedure and for urethra stricture surgery. Real-time, close-up, high speed video imaging showed that tissue ablation mechanism of these catheters is predominately governed by explosive short-life vapor bubbles fragmenting the tissue to small particles. In order to temper the ablation process, laser energy was delivered in 8 pulses divided over 8 sectors of a multifiber catheter (multiplexing), keeping the same fluence instead of one pulse addressing all the fibers at once.

  15. Carbon dioxide gas purification and analytical measurement for leading edge 193nm lithography

    NASA Astrophysics Data System (ADS)

    Riddle Vogt, Sarah; Landoni, Cristian; Applegarth, Chuck; Browning, Matt; Succi, Marco; Pirola, Simona; Macchi, Giorgio

    2015-03-01

    The use of purified carbon dioxide (CO2) has become a reality for leading edge 193 nm immersion lithography scanners. Traditionally, both dry and immersion 193 nm lithographic processes have constantly purged the optics stack with ultrahigh purity compressed dry air (UHPCDA). CO2 has been utilized for a similar purpose as UHPCDA. Airborne molecular contamniation (AMC) purification technologies and analytical measurement methods have been extensively developed to support the Lithography Tool Manufacturers purity requirements. This paper covers the analytical tests and characterizations carried out to assess impurity removal from 3.0 N CO2 (beverage grade) for its final utilization in 193 nm and EUV scanners.

  16. Laser dentistry: A new application of excimer laser in root canal therapy

    SciTech Connect

    Pini, R.; Salimbeni, R.; Vannini, M.; Barone, R.; Clauser, C.

    1989-01-01

    We report the first study of the application of excimer lasers in dentistry for the treatment of dental root canals. High-energy ultraviolet (UV) radiation emitted by an XeCl excimer laser (308 nm) and delivered through suitable optical fibers can be used to remove residual organic tissue from the canals. To this aim, UV ablation thresholds of dental tissues have been measured, showing a preferential etching of infiltrated dentin in respect to healthy dentin, at laser fluences of 0.5-1.5 J/cm{sup 2}. This technique has been tested on extracted tooth samples, simulating a clinical procedure. Fibers of decreasing core diameters have been used to treat different sections of the root canal down to its apical portion, resulting in an effective, easy, and fast cleaning action. Possible advantages of excimer laser clinical applications in respect to usual procedures are also discussed.

  17. Excimer laser annealing to fabricate low cost solar cells

    NASA Technical Reports Server (NTRS)

    1984-01-01

    The objective is to show whether or not pulsed excimer laser annealing (PELA) of ion-implanted junctions is a cost effective replacement for diffused junctions in fabricating crystalline silicon solar cells. The preliminary economic analysis completed shows that the use of PELA to fabricate both the front junction and back surface field (BSF) would cost approximately 35 cents per peak watt (Wp), compared to a cost of 15 cents/Wp for diffusion, aluminum BSF and an extra cleaning step in the baseline process. The cost advantage of the PELA process depends on improving the average cell efficiency from 14% to 16%, which would lower the overall cost of the module by about 15 cents/Wp. An optimized PELA process compatible with commercial production is to be developed, and increased cell efficiency with sufficient product for adequate statistical analysis demonstrated. An excimer laser annealing station was set-up and made operational. The first experiment used 248 nm radiation to anneal phosphorus implants in polished and texture-etched silicon.

  18. Excimer Laser Beam Analyzer Based on CVD Diamond

    NASA Astrophysics Data System (ADS)

    Girolami, Marco; Salvatori, Stefano; Conte, Gennaro

    2010-11-01

    1-D and 2-D detector arrays have been realized on CVD-diamond. The relatively high resistivity of diamond in the dark allowed the fabrication of photoconductive "sandwich" strip (1D) or pixel (2D) detectors: a semitransparent light-receiving back-side contact was used for detector biasing. Cross-talk between pixels was limited by using intermediate guard contacts connected at the same ground potential of the pixels. Each pixel photocurrent was conditioned by a read-out electronics composed by a high sensitive integrator and a Σ-Δ ADC converter. The overall 500 μs conversion time allowed a data acquisition rate up to 2 kSPS. The measured fast photoresponse of the samples in the ns time regime suggests to use the proposed devices for fine tuning feedback of high-power pulsed-laser cavities, whereas solar-blindness guarantees high performance in UV beam diagnostics also under high intensity background illumination. Offering unique properties in terms of thermal conductivity and visible-light transparency, diamond represents one of the most suitable candidate for the detection of high-power UV laser emission. The technology of laser beam profiling is evolving with the increase of excimer lasers applications that span from laser-cutting to VLSI and MEMS technologies. Indeed, to improve emission performances, fine tuning of the laser cavity is required. In such a view, the development of a beam-profiler, able to work in real-time between each laser pulse, is mandatory.

  19. Boron distribution in silicon after multiple pulse excimer laser annealing

    SciTech Connect

    Monakhov, E.V.; Svensson, B.G.; Linnarsson, M.K.; La Magna, A.; Italia, M.; Privitera, V.; Fortunato, G.; Cuscuna, M.; Mariucci, L.

    2005-08-22

    We have studied B redistribution in Si after excimer laser annealing (ELA) with multiple laser pulses. B was implanted with energies of 1 and 10 keV and doses of 1x10{sup 14} and 1x10{sup 15} cm{sup -2}. ELA with the number of pulses from 1 to 100 was performed at room temperature and 450 deg. C in vacuum. Irrespective of the implantation parameters and the ELA conditions used, a pile-up in the B concentration is observed near the maximum melting depth after ten pulses of ELA. Moreover, a detailed study has revealed that B accumulates at the maximum melt depth gradually with the number of ELA pulses. Besides, an increase in the carrier concentration is observed at the maximum melt depth, suggesting electrical activity of the accumulated B. Formation of Si-B complexes and vacancy accumulation during multiple ELA are discussed as possible mechanisms for the B build-up.

  20. Laser excited fluorescence in the cesium-xenon excimer and the cesium dimer

    NASA Technical Reports Server (NTRS)

    Exton, R. J.; Snow, W. L.; Hillard, M. E.

    1978-01-01

    Argon ion laser lines are used to excite fluorescence in a mixture of cesium and xenon. Excimer band fluorescence is observed at higher pressures (about 1 atm) while at lower pressures (several torr) a diffuse fluorescence due to the cesium dimer is observed whose character changes with exciting wavelength. The excimer fluorescence is shown to be directly related to the location of the exciting wavelength within previously measured Cs/Xe line shapes. This fact suggests that the excimer systems may be efficiently pumped through these line shapes. Qualitative energy-level schemes are proposed to explain the observations in both the excimer and dimer systems.

  1. Product channels in the 193-nm photodissociation of HCNO (fulminic acid)

    NASA Astrophysics Data System (ADS)

    Feng, Wenhui; Hershberger, John F.

    2016-06-01

    IR diode laser spectroscopy was used to detect the products of HCNO (fulminic acid) photolysis at 193 nm. Six product channels are energetically possible at this photolysis wavelength: O + HCN, H + NCO/CNO, CN + OH, CO + NH, NO + CH and HNCO. In some experiments, isotopically labeled 15N18O, C2D6 or C6H12 reagents were included into the photolysis mixture in order to suppress and/or redirect possible secondary reactions. HCN, OC18O, 15N15NO, CO, DCN and HNCO molecules were detected upon laser photolysis of HCNO/reagents/buffer gas mixtures. Analysis of the yields of product molecules leads to the following photolysis quantum yields: ϕ1a (O + HCN) = 0.38 ± 0.04, ϕ1b (H + (NCO)) = 0.07 ± 0.02, ϕ1c (CN + OH) = 0.24 ± 0.03, ϕ1d (CO + NH(a1Δ)) < 0.22 ± 0.1, ϕ1e (HNCO) = 0.02 ± 0.01 and ϕ1f (CH + NO) = 0.21 ± 0.1, respectively.

  2. Influence of thermal annealing and ultraviolet light irradiation on LaF3 thin films at 193 nm.

    PubMed

    Lee, Cheng-Chung; Liu, Ming-Chung; Kaneko, Masaaki; Nakahira, Kazuhide; Takano, Yuuichi

    2005-11-10

    Lanthanum fluoride (LaF3) thin films were prepared by resistive heating evaporation and electron-beam gun evaporation under the same deposition rate, deposition substrate temperature, and vacuum pressure. The coated LaF3 films were then treated by heat annealing and UV light irradiation. The optical properties, microstructures, stress, and laser-induced damage threshold (LIDT) at a wavelength of 193 nm were investigated. The surface roughness, optical loss, stress, and LIDT of the films were improved after the annealing. The films had better properties when irradiated by UV light as compared with heat annealing. PMID:16294967

  3. Nd:YAG laser cleaning of ablation debris from excimer-laser-ablated polyimide

    NASA Astrophysics Data System (ADS)

    Gu, Jianhui; Low, Jason; Lim, Puay K.; Lim, Pean

    2001-10-01

    In the processing of excimer laser ablation of nozzles on polyimide in air, both gases like CO2, CO and HCN and solid debris including C2 approximately C12 are produced in laser ablation area. In this paper, we reported for the first time a Nd:YAG laser cleaning of ablation debris generated in excimer laser ablation of polyimide. It demonstrated effective cleaning with the advantages of shortening cleaning cycle time and simplifying cleaning process. The laser used for the cleaning was a Q-switched and frequency doubled Nd:YAG laser with wavelength of 532 nm and repetition rate of 10 Hz. The laser cleaning effect was compared with conventional plasma ashing. AFM measurement showed that the Nd:YAG laser cleaning had no damage to the substrate. XPS results indicated that the polyimide surface cleaned with laser beam had a lower oxygen/carbon ratio than that of plasma ashing. The study shows that frequency doubled Nd:YAG laser cleaning is effective in ablation debris removal from excimer laser ablated polyimide.

  4. Understanding dissolution behavior of 193nm photoresists in organic solvent developers

    NASA Astrophysics Data System (ADS)

    Lee, Seung-Hyun; Park, Jong Keun; Cardolaccia, Thomas; Sun, Jibin; Andes, Cecily; O'Connell, Kathleen; Barclay, George G.

    2012-03-01

    Herein, we investigate the dissolution behavior of 193-nm chemically amplified resist in different organic solvents at a mechanistic level. We previously reported the effect of solvent developers on the negative tone development (NTD) process in both dry and immersion lithography, and demonstrated various resist performance parameters such as photospeed, critical dimension uniformity, and dissolution rate contrast are strongly affected by chemical nature of the organic developer. We further pursued the investigation by examining the dependence of resist dissolution behavior on their solubility properties using Hansen Solubility Parameter (HSP). The effects of monomer structure, and resist composition, and the effects of different developer chemistry on dissolution behaviors were evaluated by using laser interferometry and quartz crystal microbalance. We have found that dissolution behaviors of methacrylate based resists are significantly different in different organic solvent developers such as OSDTM-1000 Developer* and n-butyl acetate (nBA), affecting their resist performance. This study reveals that understanding the resist dissolution behavior helps to design robust NTD materials for higher resolution imaging.

  5. Fabrication of Fresnel microlens with excimer laser contour ablation

    NASA Astrophysics Data System (ADS)

    Wójcik, Michał R.; Antończak, Arkadiusz J.; Kozioł, Paweł E.; Łazarek, Łukasz K.; Stepak, Bogusz D.; Abramski, Krzysztof M.

    2014-08-01

    Laser micromachining systems based on excimer lasers are usually oriented to work with mask projection regime because of the low pulse repetition rate as well as large beam aperture of the laser source. In case of fabricating of the complex 3D structures, this approach introduces a number of limitations. Alternative solution might be usage of direct writing laser mode. Some examples of the so called contour ablation approach for fabricating microlenses with an absolutely monotonically changing cross-sectional profile are presented in the literature. Based on this idea and introducing new variables like automatic mask selection as well as optimizing process algorithms led us to obtain more versatile method for shape approximation. Hence, there were fabricated structures with cross-sectional profiles described as functions that are monotonic on specified intervals such as Fresnel microlenses. In this paper we describe approximation of process parameters for obtaining desired cross-sectional profiles and finally fabrication of few exemplary microlenses. All structures were characterized by a digital optical microscopy and compared to the given profiles. The accuracy of reproduction of the desired structures at the level of single microns was achieved.

  6. Studies in fiber guided excimer laser surgery for cutting and drilling bone and meniscus.

    PubMed

    Dressel, M; Jahn, R; Neu, W; Jungbluth, K H

    1991-01-01

    Our experiments on transmitting high-power excimer laser pulses through optical fibers and our investigations on excimer laser ablation of hard tissue show the feasibility of using the excimer laser as an additional instrument in general and accident surgery involving minimal invasive surgery. By combining XeCl-excimer lasers and tapered fused silica fibers we obtained output fluences up to 32 J/cm2 and ablation rates of 3 microns/pulse of hard tissue. This enables us to cut bone and cartilage in a period of time which is suitable for clinical operations. Various experiments were carried out on cadavers in order to optimize the parameters of the excimer laser and fibers: e.g., wavelength, pulse duration, energy, repetition rate, fiber core diameter. The surfaces of the cut tissue are comparable to cuts with conventional instruments. No carbonisation was observed. The temperature increase is below 40 degrees C in the tissue surrounding the laser spot. The healing rate of an excimer laser cut is not slower than mechanical treatments; the quality is comparable. PMID:1661360

  7. A survey of advanced excimer optical imaging and lithography

    NASA Astrophysics Data System (ADS)

    Matsumoto, Koichi; Suwa, Kyoichi

    1998-11-01

    The first item discussed in this paper is to estimate the future trend regarding minimum geometry and the optical parameters, such as NA and wavelength. Simulations based on aerial images are performed for the estimation. The resolution limit is defined as a minimum feature size which retains practical depth of focus (DOF). Pattern geometry is classified into two categories, which are dense lines and isolated lines. Available wavelengths are assumed to be KrF excimer laser (λ=248 nm), ArF excimer laser (λ=193 nm) and F2 excimer laser (λ=157 nm). Based upon the simulation results, the resolution limit is estimated for each geometry and each wavelength. The second item is to survey ArF optics. At present, the ArF excimer laser is regarded as one of the most promising candidates as a next-generation light source. Discussions are ranging over some critical issues. The lifetime of ArF optics supposedly limited by the radiation compaction of silica glass is estimated in comparison with KrF optics. Availability of calcium fluoride (CaF2) is also discussed. As a designing issue, a comparative study is made about the optical configuration, dioptric or catadioptric. In the end, our resist-based performance is shown.

  8. Excimer-laser-assisted deposition of diamondlike carbon hard coatings

    NASA Astrophysics Data System (ADS)

    Wei, Mao-Kuo; Popp, Angelika; Lang, Adolf; Schutte, Karsten; Bergmann, Hans W.

    1997-08-01

    Diamond-like carbon (DLC) films were deposited using the excimer laser assisted physical vapor deposition at room temperature. The films deposited at high vacuum (10-5 mbar) revealed more diamond-like character than under other atmospheres of argon and hydrogen. DLC- films can be deposited with a thickness more than 1 micrometers with the help of either an additional Ti-buffer layer or an in-situ laser treatment during the deposition. The adhesion of the films was qualitatively determined by using the indentation and bending tests. Additionally, the adhesion was found to be dependent on the power densities for the target ablation (IT) and for the in-situ laser treatment (IS), as well as, on the applied buffer layer. The roughness was found to be proportional to the film thickness at various surface morphologies of the substrate. The friction coefficient of DLC-films against steel (100Cr6) was found to be approximately 0.1 and the wear loss of the films was dependent on the properties of substrate material.

  9. Advanced excimer laser technologies enable green semiconductor manufacturing

    NASA Astrophysics Data System (ADS)

    Fukuda, Hitomi; Yoo, Youngsun; Minegishi, Yuji; Hisanaga, Naoto; Enami, Tatsuo

    2014-03-01

    "Green" has fast become an important and pervasive topic throughout many industries worldwide. Many companies, especially in the manufacturing industries, have taken steps to integrate green initiatives into their high-level corporate strategies. Governments have also been active in implementing various initiatives designed to increase corporate responsibility and accountability towards environmental issues. In the semiconductor manufacturing industry, there are growing concerns over future environmental impact as enormous fabs expand and new generation of equipments become larger and more powerful. To address these concerns, Gigaphoton has implemented various green initiatives for many years under the EcoPhoton™ program. The objective of this program is to drive innovations in technology and services that enable manufacturers to significantly reduce both the financial and environmental "green cost" of laser operations in high-volume manufacturing environment (HVM) - primarily focusing on electricity, gas and heat management costs. One example of such innovation is Gigaphoton's Injection-Lock system, which reduces electricity and gas utilization costs of the laser by up to 50%. Furthermore, to support the industry's transition from 300mm to the next generation 450mm wafers, technologies are being developed to create lasers that offer double the output power from 60W to 120W, but reducing electricity and gas consumption by another 50%. This means that the efficiency of lasers can be improve by up to 4 times in 450mm wafer production environments. Other future innovations include the introduction of totally Heliumfree Excimer lasers that utilize Nitrogen gas as its replacement for optical module purging. This paper discusses these and other innovations by Gigaphoton to enable green manufacturing.

  10. Absorption coefficients for water vapor at 193 nm from 300 to 1073 K

    NASA Technical Reports Server (NTRS)

    Kessler, W. J.; Carleton, K. L.; Marinelli, W. J.

    1993-01-01

    Measurements of the water absorption coefficient at 193 nm from 300 to 1073 K are reported. The measurements were made using broadband VUV radiation and a monochromator-based detection system. The water vapor was generated by a saturator and metered into a flowing, 99 cm absorption cell via a water vapor mass flow meter. The 193 nm absorption coefficient measurements are compared to room temperature and high temperature shock tube measurements with good agreement. The absorption can be parameterized by a nu3 vibrational mode reaction coordinate and the thermal population of the nu3 mode.

  11. Design, synthesis, and characterization of fluorine-free PAGs for 193-nm lithography

    NASA Astrophysics Data System (ADS)

    Liu, Sen; Glodde, Martin; Varanasi, Pushkara R.

    2010-04-01

    Photoacid generators (PAGs) are a key component in chemically amplified resists used in photolithography. Perfluorooctanesulfonates (PFOS) and other perfluoroalkylsulfonates (PFAS) have been well adopted as PAGs in 193 nm photoresist. Recently, concerns have been raised about their environmental impact due to their chemical persistency, bioaccumulation and toxicity. It is a general interest to find environmentally benign PAGs that are free of fluorine atoms. Here we describe the design, synthesis and characterization of a series of novel fluorine-free onium salts as PAGs for 193 nm photoresists. These PAGs demonstrated desirable physical and lithography properties when compared with PFAS-based PAGs for both dry and immersion exposures.

  12. Microencapsulation of silicon cavities using a pulsed excimer laser

    NASA Astrophysics Data System (ADS)

    Sedky, S.; Tawfik, H.; Ashour, M.; Graham, A. B.; Provine, J.; Wang, Q.; Zhang, X. X.; Howe, R. T.

    2012-07-01

    This work presents a novel low thermal-budget technique for sealing micromachined cavities in silicon. Cavities are sealed without deposition, similar to the silicon surface-migration sealing process. In contrast to the 1100 °C furnace anneal required for the migration process, the proposed technique uses short excimer laser pulses (24 ns), focused onto an area of 23 mm2, to locally heat the top few microns of the substrate, while the bulk substrate remains near ambient temperature. The treatment can be applied to selected regions of the substrate, without the need for special surface treatments or a controlled environment. This work investigates the effect of varying the laser pulse energy from 400 mJ cm-2 to 800 mJ cm-2, the pulse rate from 1 Hz to 50 Hz and the pulse count from 200 to 3000 pulses on sealing microfabricated cavities in silicon. An analytical model for the effect of holes on the surface temperature distribution is derived, which shows that much higher temperatures can be achieved by increasing the hole density. A mechanism for sealing the cavities is proposed, which indicates how complete sealing is feasible.

  13. Atomic force microscopy analysis of human cornea surface after UV (λ=266 nm) laser irradiation

    NASA Astrophysics Data System (ADS)

    Spyratou, E.; Makropoulou, M.; Moutsouris, K.; Bacharis, C.; Serafetinides, A. A.

    2009-07-01

    Efficient cornea reshaping by laser irradiation for correcting refractive errors is still a major issue of interest and study. Although the excimer laser wavelength of 193 nm is generally recognized as successful in ablating corneal tissue for myopia correction, complications in excimer refractive surgery leads to alternative laser sources and methods for efficient cornea treatment. In this work, ablation experiments of human donor cornea flaps were conducted with the 4th harmonic of an Nd:YAG laser, with different laser pulses. AFM analysis was performed for examination of the ablated cornea flap morphology and surface roughness.

  14. Average power scaling of UV excimer lasers drives flat panel display and lidar applications

    NASA Astrophysics Data System (ADS)

    Herbst, Ludolf; Delmdahl, Ralph F.; Paetzel, Rainer

    2012-03-01

    Average power scaling of 308nm excimer lasers has followed an evolutionary path over the last two decades driven by diverse industrial UV laser microprocessing markets. Recently, a new dual-oscillator and beam management concept for high-average power upscaling of excimer lasers has been realized, for the first time enabling as much as 1.2kW of stabilized UV-laser average output power at a UV wavelength of 308nm. The new dual-oscillator concept enables low temperature polysilicon (LTPS) fabrication to be extended to generation six glass substrates. This is essential in terms of a more economic high-volume manufacturing of flat panel displays for the soaring smartphone and tablet PC markets. Similarly, the cost-effective production of flexible displays is driven by 308nm excimer laser power scaling. Flexible displays have enormous commercial potential and can largely use the same production equipment as is used for rigid display manufacturing. Moreover, higher average output power of 308nm excimer lasers aids reducing measurement time and improving the signal-to-noise ratio in the worldwide network of high altitude Raman lidar stations. The availability of kW-class 308nm excimer lasers has the potential to take LIDAR backscattering signal strength and achievable altitude to new levels.

  15. Theoretical Modeling of the Discharge-Pumped Xenon - Excimer Laser.

    NASA Astrophysics Data System (ADS)

    Zhu, Sheng-Bai

    The present dissertation is dedicated to a theoretical study of the discharge pumped XeCl excimer laser. For a better description of our system, Two modelings which supplement each other from different angles have been successfully developed. The first one, a comprehensive kinetics model which can be applied to the detailed simulations of the temporal behavior of the discharge characteristics and laser performance, is constructed by a set of coupled first -order differential equations, such as the rate equations, the Boltzmann equation, the external electric circuit equations, the energy balance equation, and the equations of optical resonator. The starting and termination of the discharge are taken into deliberation for the first time, especially for the Blumlein case. Some 70 kinetic processes and 23 chemical species are included. Such a problem can only be numerically solved by means of an elaborate computer code. Another model, on the other hand, pays attention to the quasi-steady-state to facilitate parametric study. A group of rate coefficients for the kinetic processes involving free electrons are approximated by analytic expressions using numerical results compiled from computer code calculations. Explicit expressions of the number densities for all relevant chemical species are obtained. Among them, HCI(O), H, and Cl can never reach steady-state population. Time history of the concentrations for these species are computed instead. With the discussions about the effect of vibrational relaxation and state-to-state transfer in the upper energy level, and the discussions about the rotational structure, collisional broadening, and dissociation of the diatomic ground state, we have extensively investigated the spontaneous emission spectra, the small-signal gain, the non-saturable absorption, the steady-state laser output power, and various efficiencies. Saturation effects in laser oscillators and laser amplifiers are discussed as well. These topics relate to the

  16. Results from a new 193nm die-to-database reticle inspection platform

    NASA Astrophysics Data System (ADS)

    Broadbent, William H.; Alles, David S.; Giusti, Michael T.; Kvamme, Damon F.; Shi, Rui-fang; Sousa, Weston L.; Walsh, Robert; Xiong, Yalin

    2010-05-01

    A new 193nm wavelength high resolution reticle defect inspection platform has been developed for both die-to-database and die-to-die inspection modes. In its initial configuration, this innovative platform has been designed to meet the reticle qualification requirements of the IC industry for the 22nm logic and 3xhp memory generations (and shrinks) with planned extensions to the next generation. The 22nm/3xhp IC generation includes advanced 193nm optical lithography using conventional RET, advanced computational lithography, and double patterning. Further, EUV pilot line lithography is beginning. This advanced 193nm inspection platform has world-class performance and the capability to meet these diverse needs in optical and EUV lithography. The architecture of the new 193nm inspection platform is described. Die-to-database inspection results are shown on a variety of reticles from industry sources; these reticles include standard programmed defect test reticles, as well as advanced optical and EUV product and product-like reticles. Results show high sensitivity and low false and nuisance detections on complex optical reticle designs and small feature size EUV reticles. A direct comparison with the existing industry standard 257nm wavelength inspection system shows measurable sensitivity improvement for small feature sizes

  17. Study of barrier coats for application in immersion 193-nm lithography

    NASA Astrophysics Data System (ADS)

    Houlihan, Francis; Kim, Wookyu; Sakamuri, Raj; Hamilton, Keino; Dimerli, Alla; Abdallah, David; Romano, Andrew; Dammel, Ralph R.; Pawlowski, Georg; Raub, Alex; Brueck, Steve

    2005-05-01

    We will describe our barrier coat approach for use in immersion 193 nm lithography. These barrier coats may act as either simple barriers providing protection against loss of resist components into water or in the case of one type of these formulations which have a refractive index at 193 nm which is the geometric mean between that of the resist and water provide, also top antireflective properties. Either type of barrier coat can be applied with a simple spinning process compatible with PGMEA based resin employing standard solvents such as alcohols and be removed during the usual resist development process with aqueous 0.26 N TMAH. We will discuss both imaging results with these materials on acrylate type 193 nm resists and also show some fundamental studies we have done to understand the function of the barrier coat and the role of differing spinning solvents and resins. We will show LS (55 nm) and Contact Hole (80 nm) resolved with a 193 nm resist exposed with the interferometric tool at the University of New Mexico (213 nm) with and without the use of a barrier coat.

  18. Ablation algorithms and corneal asphericity in myopic correction with excimer lasers

    NASA Astrophysics Data System (ADS)

    Iroshnikov, Nikita G.; Larichev, Andrey V.; Yablokov, Michail G.

    2007-06-01

    The purpose of this work is studying a corneal asphericity change after a myopic refractive correction by mean of excimer lasers. As the ablation profile shape plays a key role in the post-op corneal asphericity, ablation profiles of recent lasers should be studied. The other task of this research was to analyze operation (LASIK) outcomes of one of the lasers with generic spherical ablation profile and to compare an asphericity change with theoretical predictions. The several correction methods, like custom generated aspherical profiles, may be utilized for mitigation of unwanted effects of asphericity change. Here we also present preliminary results of such correction for one of the excimer lasers.

  19. Excimer lasers. (Latest citations from the US Patent bibliographic file with exemplary claims). Published Search

    SciTech Connect

    1995-01-01

    The bibliography contains citations of selected patents concerning the design and development of excimer laser devices, apparatus, and systems for use in industrial and medical applications. Citations discuss ablation and lithography technology, compact excimer lasers, laser gas purification and recycling, microwave and discharge excited lasers, and rare gas halides. Applications are considered, including metallization and patterning, manufacturing of ophthalmic lenses, profiling of optical surfaces, treatment of engine parts, prosthetic surgery, and corneal ablation. (Contains a minimum of 106 citations and includes a subject term index and title list.)

  20. Excimer lasers. (Latest citations from the US Patent Bibliographic file with exemplary claims). Published Search

    SciTech Connect

    1996-01-01

    The bibliography contains citations of selected patents concerning the design and development of excimer laser devices, apparatus, and systems for use in industrial and medical applications. Citations discuss ablation and lithography technology, compact excimer lasers, laser gas purification and recycling, microwave and discharge excited lasers, and rare gas halides. Applications are considered, including metallization and patterning, manufacturing of ophthalmic lenses, profiling of optical surfaces, treatment of engine parts, prosthetic surgery, and corneal ablation. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  1. Effectiveness of a 308-nm excimer laser in treatment of vitiligo: a review.

    PubMed

    Alhowaish, Alauldin Khalef; Dietrich, Nathalie; Onder, Meltem; Fritz, Klaus

    2013-05-01

    Vitiligo is a relatively common acquired disorder, characterized by progressive loss of melanocytes from the epidermis and the epidermal appendages. The disease is associated with considerable morbidity because of a major impact on the quality of life. The treatment for vitiligo is generally unsatisfactory and challenging. There are a variety of therapeutic possibilities including topical corticosteroids, topical calcineurin inhibitors, as well as phototherapy with Psoralen plus UVA (PUVA), narrow-band UVB, and a 308-nm excimer laser and/or lamps. Furthermore, surgical methods encompass grafting and transplantation while depigmentation treatments and psychological support may also be considered. The objective is to assess the effect of the 380-nm excimer laser in the treatment of vitiligo based on the available studies and case series. We searched the relevant literature about vitiligo and excimer laser published between 1990 and 2012 using the MEDLINE database. We reviewed all relevant articles about 308-nm excimer laser and light sources assessing their efficacy in the management of vitiligo as well as their side effects. The value of combination treatment methods was also analyzed. The available studies provide strong evidence that the excimer laser represents the most effective approach to treat vitiligo compared to ordinary phototherapy. Excimer laser is relatively safe and effective for localized disease. UV-sensitive areas respond best as well as a short duration of the disease. More frequent treatments achieve better results. Compared to other treatment modalities, the excimer laser most likely constitutes the treatment of choice for localized vitiligo. Its efficacy can be further improved in combination with other therapies such as corticosteroids, pimecrolimus, or tacrolimus. PMID:22892613

  2. A Decade Of Excimer Laser Research And Development At Avco Research Laboratory

    NASA Astrophysics Data System (ADS)

    Boness, M. J. W.

    1987-01-01

    This paper presents a brief overview of excimer laser research and development performed at the Avco Research Laboratory during the past decade from 1975 to the present day. Progress and highlights are depicted against a backdrop of parallel developmental paths connecting the original search and discovery activities of the mid-seventies to the development of high power repetitively-pulsed Raman shifted excimer devices in progress today.

  3. New high repetition rate, high energy 308 nm excimer laser for material processing

    NASA Astrophysics Data System (ADS)

    Herbst, Ludolf; Klaft, Ingo; Schmidt, Kai; Bragin, Igor; Albrecht, Hans-Stephan

    2007-02-01

    High power excimer lasers are well established as work horses for various kinds of micro material processing. The applications are ranging from drilling holes, trench formation, thin film ablation to the crystallization of amorphous-Si into polycrystalline-Si. All applications use the high photon energy and large pulse power of the excimer technology. The increasing demand for micro scale products has let to the demand for UV lasers which support high throughput production. We report the performance parameters of a newly developed XeCl excimer laser with doubled repetition rate compared to available lasers. The developed laser system delivers up to 900 mJ stabilized pulse energy at 600 Hz repetition rate. The low jitter UV light source operates with excellent energy stability. The outstanding energy stability was reached by using a proprietary solid-state pulser discharge design.

  4. Breakdown voltages for discharges initiated from plasma pulses produced by high-frequency excimer lasers

    SciTech Connect

    Yamaura, Michiteru

    2006-06-19

    The triggering ability under the different electric field was investigated using a KrF excimer laser with a high repetition rate of kilohertz order. Measurements were made of the magnitude of impulse voltages that were required to initiate a discharge from plasmas produced by a high-frequency excimer laser. Breakdown voltages were found to be reduced by 50% through the production of plasmas in the discharge gap by a high-frequency excimer laser. However, under direct-current electric field, triggering ability decreased drastically due to low plasma density. It is considered that such laser operation applied for laser-triggered lightning due to the produced location of plasma channel is formed under the impulse electric field since an electric field of the location drastically reduces temporary when the downward leader from thunderclouds propagates to the plasma channel.

  5. KrF excimer laser precision machining of hard and brittle ceramic biomaterials.

    PubMed

    Huang, Yao-Xiong; Lu, Jian-Yi; Huang, Jin-Xia

    2014-06-01

    KrF excimer laser precision machining of porous hard-brittle ceramic biomaterials was studied to find a suitable way of machining the materials into various desired shapes and sizes without distorting their intrinsic structure and porosity. Calcium phosphate glass ceramics (CPGs) and hydroxyapatite (HA) were chosen for the study. It was found that KrF excimer laser can cut both CPGs and HA with high efficiency and precision. The ablation rates of CPGs and HA are respectively 0.081 µm/(pulse J cm(-2)) and 0.048 µm/(pulse  J cm(-2)), while their threshold fluences are individually 0.72 and 1.5 J cm(-2). The cutting quality (smoothness of the cut surface) is a function of laser repetition rate and cutting speed. The higher the repetition rate and lower the cutting speed, the better the cutting quality. A comparison between the cross sections of CPGs and HA cut using the excimer laser and using a conventional diamond cutting blade indicates that those cut by the excimer laser could retain their intrinsic porosity and geometry without distortion. In contrast, those cut by conventional machining had distorted geometry and most of their surface porosities were lost. Therefore, when cutting hard-brittle ceramic biomaterials to prepare scaffold and implant or when sectioning them for porosity evaluation, it is better to choose KrF excimer laser machining. PMID:24784833

  6. Excimer laser debridement of necrotic erosions of skin without collateral damage

    NASA Astrophysics Data System (ADS)

    Wynne, James J.; Felsenstein, Jerome M.; Trzcinski, Robert; Zupanski-Nielsen, Donna; Connors, Daniel P.

    2011-07-01

    Pulsed ArF excimer laser radiation at 6.4 eV, at fluence exceeding the ablation threshold, will debride burn eschar and other dry necrotic erosions of the skin. Debridement will cease when sufficiently moist viable tissue is exposed, due to absorption by aqueous chloride ions (Cl-) through the non-thermal process of electron photodetachment, thereby inhibiting collateral damage to the viable tissue. ArF excimer laser radiation debrides/ablates ~1 micron of tissue with each pulse. While this provides great precision in controlling the depth of debridement, the process is relatively time-consuming. In contrast, XeCl excimer laser radiation debrides ~8 microns of tissue with each pulse. However the 4.0 eV photon energy of the XeCl excimer laser is insufficient to photodetach an electron from a Cl- ion, so blood or saline will not inhibit debridement. Consequently, a practical laser debridement system should incorporate both lasers, used in sequence. First, the XeCl excimer laser would be used for accelerated debridement. When the necrotic tissue is thinned to a predetermined thickness, the ArF excimer laser would be used for very precise and well-controlled debridement, removing ultra-thin layers of material with each pulse. Clearly, the use of the ArF laser is very desirable when debriding very close to the interface between necrotic tissue and viable tissue, where the overall speed of debridement need not be so rapid and collateral damage to viable tissue is undesirable. Such tissue will be sterile and ready for further treatment, such as a wound dressing and/or a skin graft.

  7. Initial experience in the extraction of chronically implanted pacemaker leads using the Excimer laser sheath

    PubMed Central

    Levy, T; Walker, S; Paul, V

    1999-01-01

    OBJECTIVE—To assess the safety and efficiency of the Excimer laser sheath in extracting chronically implanted pacemaker leads.
PATIENTS—Eight patients were studied (one female, mean age 62 years, range 34 to 77) with 17 pacemaker leads (five atrial, 10 ventricular, two implantable defibrillator). The mean implantation time was 65 months (range 23 to 188). The indications for lead extraction were chronic infection (7), superior vena cava obstruction (4), lead malfunction (4), and pain (2).
METHODS—A prospective analysis of the use of the Excimer laser sheath in extracting chronically implanted pacemaker leads. Laser sheath extraction was undertaken if conventional extraction techniques with simple traction or traction with a locking stylet had failed. If laser sheath extraction was unsuccessful, basket retrieval of the lead from the groin was performed.
RESULTS—Complete lead removal was achieved in 16 leads (94%). In one case the electrode tip was left behind without complication. Extraction was achieved with the laser sheath alone in 16 leads. Basket retrieval was required in one case after laser failure. There were no complications.
CONCLUSIONS—The Excimer laser sheath appears to be an effective and safe technique for extracting chronically implanted pacemaker leads. It can be used in combination with the currently available techniques for successful lead extraction.


Keywords: Excimer laser sheath; lead extraction; pacing PMID:10377320

  8. Laser-induced fluorescence of fused silica irradiated by ArF excimer laser

    SciTech Connect

    Zhang Haibo; Yuan Zhijun; Zhou Jun; Dong Jingxing; Wei Yunrong; Lou Qihong

    2011-07-01

    Laser-induced fluorescence (LIF) of high-purity fused silica irradiated by ArF excimer laser is studied experimentally. LIF bands of the fused silica centered at 281 nm, 478 nm, and 650 nm are observed simultaneously. Furthermore, the angular distribution of the three fluorescence peaks is examined. Microscopic image of the laser modified fused silica indicates that scattering of the generated fluorescence by laser-induced damage sites is the main reason for the angular distribution of LIF signals. Finally, the dependence of LIF signals intensities of the fused silica on laser power densities is presented. LIF signals show a squared power density dependence, which indicates that laser-induced defects are formed mainly via two-photon absorption processes.

  9. Mesoscale Laser Processing using Excimer and Short-Pulse Ti: Sapphire Lasers

    SciTech Connect

    Shirk, M D; Rubenchik, A M; Gilmer, G H; Stuart, B C; Armstrong, J P; Oberhelman, S K; Baker, S L; Nikitin, A J; Mariella, R P

    2003-07-28

    Targets to study high-energy density physics and inertial confinement fusion processes have very specific and precise tolerances that are pushing the state-of-the-art in mesoscale microsculpting technology. A significant effort is required in order to advance the capabilities to make these targets with very challenging geometries. Ultrashort pulsed (USP) Ti:Sapphire lasers and excimer lasers are proving to be very effective tools in the fabrication of the very small pieces that make up these targets. A brief description of the dimensional and structural requirements of these pieces will be presented, along with theoretical and experimental results that demonstrate to what extent these lasers are achieving the desired results, which include sub-{mu}m precision and RMS surface values well below 100 nm. This work indicates that excimer lasers are best at sculpting the polymer pieces and that the USP lasers work quite well on metal and aerogel surfaces, especially for those geometries that cannot be produced using diamond machining and where material removal amounts are too great to do with focused ion beam milling in a cost effective manner. In addition, the USP laser may be used as part of the procedure to fill target capsules with fusion fuel, a mixture of deuterium and tritium, without causing large perturbations on the surface of the target by keeping holes drilled through 125 {micro}m of beryllium below 5 {micro}m in diameter.

  10. Excimer laser annealing: A gold process for CZ silicon junction formation

    NASA Technical Reports Server (NTRS)

    Wong, David C.; Bottenberg, William R.; Byron, Stanley; Alexander, Paul

    1987-01-01

    A cold process using an excimer laser for junction formation in silicon has been evaluated as a way to avoid problems associated with thermal diffusion. Conventional thermal diffusion can cause bulk precipitation of SiOx and SiC or fail to completely activate the dopant, leaving a degenerate layer at the surface. Experiments were conducted to determine the feasibility of fabricating high quality p-n junctions using a pulsed excimer laser for junction formation at remelt temperature with ion-implanted surfaces. Solar-cell efficiency exceeding 16 percent was obtained using Czochralski single-crystal silicon without benefit of back surface field or surface passivation. Characterization shows that the formation of uniform, shallow junctions (approximately 0.25 micron) by excimer laser scanning preserves the minority carrier lifetime that leads to high current collection. However, the process is sensitive to initial surface conditions and handling parameters that drive the cost up.

  11. Studies on a cross-linking type positive 193nm photoresist material

    NASA Astrophysics Data System (ADS)

    Wang, Liyuan; Guo, Xin; Chu, Zhanxing; Wang, Wenjun

    2006-03-01

    A kind of diacid, acrylpimaric acid, with condensed alicyclic structure and good film-forming property, was prepared by the Diels-Alder reaction of abietic acid and acrylic acid. In their solid film, the diacid can react with divinyl ether, such as 1,3-divinyloxyethoxybenzene when baked above 80 °C and become insoluble in dilute aqueous base. Thus formed compound can be quickly decomposed at the presence of strong acid generated by PAG above 100 °C and become easily soluble in dilute aqueous base. A positive photoresist can be formed by the diacid, divinyl ether and PAG. The measured photosensitivity is less than 50 mj/cm2 when exposed to low pressure Hg lamp (254nm). The diacid mixture displayed lower transparency than estimated at 193 nm and should be further purified to be used in 193 nm photoresist.

  12. IBM-JSR 193-nm negative tone resist: polymer design, material properties, and lithographic performance

    NASA Astrophysics Data System (ADS)

    Patel, Kaushal S.; Lawson, Margaret C.; Varanasi, Pushkara Rao; Medeiros, David R.; Wallraff, Gregory M.; Brock, Phillip J.; DiPietro, Richard A.; Nishimura, Yukio; Chiba, Takashi; Slezak, Mark

    2004-05-01

    It has been previously proposed that negative-tone resist process would have an intrinsic advantage for printing narrow trench geometry. To demonstrate this for 193nm lithography, a negative resist with performance comparable to a leading positive resist is required. In this paper we report the joint development of a hexafluoroalcohol containing, 193nm, negative-tone, chemically amplified resist based on the crosslinking approach. Lithographic performance is presented which includes the ability of the negative-tone resist to print 90nm line/space and isolated trenches with standard resist processing. The impact of the fluorinated polymer on etch performance is also quantified. Finally, key resist characteristics and their influence on performance and limiting factors such as microbridging are discussed.

  13. A comparison of excimer laser, thermal probe, and mechanical devices for recanalizing occluded human arteries.

    PubMed

    Moriuchi, M; Tobis, J M; Mcrae, M; Mallery, J A; Macleay, L; Moussabeck, O; Berns, M; Henry, W L

    1991-06-01

    To evaluate the mechanism of excimer laser recanalization and compare the results with those of laser-assisted thermal probe recanalization and mechanical recanalization, a total of 42 human atherosclerotic totally occluded arterial segments (2-15 cm long) were recanalized by excimer laser with a 400-800 micron quartz fiber pulsed at 20 Hz with 50 mJ/mm2 of energy (n = 21), an Argon heated thermal probe at 10-12 watts (n = 11), a guidewire directed through a 6 Fr multipurpose catheter, or an angioplasty balloon catheter (n = 10). On histologic examination, the excimer laster created a single round lumen or multiple lumens ("Swiss-cheese" like appearance) with no evidence of thermal injury at the perimeter of the lumen. The incidence of perforation in vitro was less with an excimer laser catherter (8/21 or 38%) than with the thermal prove (10/11 or 91%) (p less than 0.01). However, serial histologic cross-sectional examination showed that the pathway of the devices were essentially the same in all recanalization procedures. The pathway of the device was located outside the atheroma but proximal to the internal elastic membrane in 13 arteries with the excimer laser (62%), in 10 arteries with the thermal probe (91%), and 8 arteries with mechanical devices (80%). These results indicate that although the eximer laser could recanalize human atherosclerotic arteries without thermal injury, the fiber frequently deflected around firm atherosclerotic plaque and advanced in a dissection plane between the plaque and media. A similar course was noted for the thermal probe or during mechanical recanalization with a guidewire and catheter. To insure the safety of an excimer fiber or a thermal probe to reopen complete occlusions, better guidance systems must be developed. PMID:1875527

  14. Early and late healing responses of normal canine artery to excimer laser irradiation.

    PubMed

    Prevosti, L G; Leon, M B; Smith, P D; Dodd, J T; Bonner, R F; Robinowitz, M; Clark, R E; Virmani, R

    1988-07-01

    Acute in vitro histologic studies have shown that the pulsed xenon chloride excimer laser causes precise microablation without the surrounding thermal tissue injury associated with frequently used continuous-wave lasers such as the argon, carbon dioxide, and neodymium:yttrium aluminum garnet lasers. However, the in vivo healing response of artery wall to excimer laser injury is not known. Accordingly, a xenon chloride excimer laser (308 nm, 40 nsec pulse width, 39 mJ/mm2/pulse) was transmitted via a 600 micron fused silica fiber to create 420 craters of varying depths (30 to 270 micron) in 21 normal canine femoral and carotid arteries. At 2 hours, 2 days, 10 days, and 42 days after excimer laser ablation, the artery segments were perfusion fixed in situ and analyzed by light, scanning, and transmission electron microscopy. At 2 hours, craters were covered by a carpet of platelets and entrapped red blood cells. Fibrin and exposed collagen fibers were seen at the crater base. There was a sharp demarcation of the crater-artery wall interface without lateral laser tissue injury. At 2 days, adherent platelets persisted with thrombus covering the base of the craters. Early healing responses were present, consisting of polymorphonucleated leukocytes and new endothelial cells, which extended over the crater rims. At 10 days, no thrombi were seen, and healing continued with almost complete reendothelialization. Macrophages, fibroblasts, fibrin, and entrapped red blood cells were present below the reendothelialized surface. At 42 days, healing was complete with obliteration of the craters by fibrointimal ingrowth. The surface was completely covered by a smooth monolayer of axially aligned endothelial cells. There were no aneurysms or surface hyperplastic responses. These favorable healing responses in normal canine arteries suggest that pulsed lasers with high tissue absorption coefficients, such as the xenon chloride excimer laser, may be suitable energy sources for

  15. Faster qualification of 193-nm resists for 100-nm development using photo cell monitoring

    NASA Astrophysics Data System (ADS)

    Jones, Chris M.; Kallingal, Chidam; Zawadzki, Mary T.; Jeewakhan, Nazneen N.; Kaviani, Nazila N.; Krishnan, Prakash; Klaum, Arthur D.; Van Ess, Joel

    2003-05-01

    The development of 100-nm design rule technologies is currently taking place in many R&D facilities across the world. For some critical alyers, the transition to 193-nm resist technology has been required to meet this leading edge design rule. As with previous technology node transitions, the materials and processes available are undergoing changes and improvements as vendors encounter and solve problems. The initial implementation of the 193-nm resits process did not meet the photolithography requirements of some IC manufacturers due to very high Post Exposure Bake temperature sensitivity and consequently high wafer to wafer CD variation. The photoresist vendors have been working to improve the performance of the 193-nm resists to meet their customer's requirements. Characterization of these new resists needs to be carried out prior to implementation in the R&D line. Initial results on the second-generation resists evaluated at Cypress Semicondcutor showed better CD control compared to the aelrier resist with comparable Depth of Focus (DOF), Exposure Latitute, Etch Resistance, etc. In addition to the standard lithography parameters, resist characterization needs to include defect density studies. It was found that the new resists process with the best CD control, resulted in the introduction of orders of magnitude higher yield limiting defects at Gate, Contact adn Local Interconnect. The defect data were shared with the resists vendor and within days of the discovery the resist vendor was able to pinpoint the source of the problem. The fix was confirmed and the new resists were successfully released to production. By including defect monitoring into the resist qualification process, Cypress Semiconductor was able to 1) drive correction actions earlier resulting in faster ramp and 2) eliminate potential yield loss. We will discuss in this paper how to apply the Micro Photo Cell Monitoring methodology for defect monitoring in the photolithogprhay module and the

  16. Defectivity reduction by optimization of 193-nm immersion lithography using an interfaced exposure-track system

    NASA Astrophysics Data System (ADS)

    Carcasi, Michael; Hatakeyama, Shinichi; Nafus, Kathleen; Moerman, Richard; van Dommelen, Youri; Huisman, Peter; Hooge, Joshua; Scheer, Steven; Foubert, Philippe

    2006-03-01

    As the integration of semiconductor devices continues, pattern sizes required in lithography get smaller and smaller. To achieve even more scaling down of these patterns without changing the basic infrastructure technology of current cutting-edge 193-nm lithography, 193-nm immersion lithography is being viewed as a powerful technique that can accommodate next-generation mass productions needs. Therefore this technology has been seriously considered and after proof of concept it is currently entering the stage of practical application. In the case of 193-nm immersion lithography, however, because liquid fills the area between the projection optics and the silicon wafer, several causes of concern have been raised - namely, diffusion of moisture into the resist film due to direct resist-water interaction during exposure, dissolution of internal components of the resist into the de-ionized water, and the influence of residual moisture generated during exposure on post-exposure processing. To prevent these unwanted effects, optimization of the three main components of the lithography system: materials, track and scanner, is required. For the materials, 193nm resist formulation improvements specifically for immersion processing have reduced the leaching and the sensitivity to water related defects, further benefits can be seen by the application of protective top coat materials. For the track component, optimization of the processing conditions and immersion specific modules are proven to advance the progress made by the material suppliers. Finally, by optimizing conditions on the 3 rd generation immersion scanner with the latest hardware configuration, defectivity levels comparable to dry processing can be achieved. In this evaluation, we detail the improvements that can be realized with new immersion specific track rinse modules and formulate a hypothesis for the improvements seen with the rinsing process. Additionally, we show the current status of water induced

  17. CO2 laser cleaning of black deposits formed during the excimer laser etching of polyimide in air

    NASA Astrophysics Data System (ADS)

    Koren, G.; Donelon, J. J.

    1988-01-01

    Pulsed CO2 laser cleaning of black debris formed during the excimer laser ablation of polyimide in air is demonstrated. The 10.6 μm CO2 laser radiation is strongly absorbed in the debris but only weakly absorbed in polyimide thus enabling the clean removal of the debris without damaging the polyimide.

  18. Front-end-of-line process development using 193-nm lithography

    NASA Astrophysics Data System (ADS)

    Pollentier, Ivan K.; Ercken, Monique; Eliat, Astrid; Delvaux, Christie; Jaenen, Patrick; Ronse, Kurt G.

    2001-04-01

    It is expected that 193nm lithography will be introduced in front-end-of-line processing for all critical layers at the 100nm node, and possibly also for some layers at the 130nm node, where critical layers are required to have the lowest mask cost. These processes are currently being investigated at IMEC for CMOS logic applications. While the lithographic performance of 193 nm resists has improved significantly in the last year, most materials still have important processing issues that need further improvement. On one hand, the resists material itself suffers from for example poor dry etch resistance and SEM CD shrinkage. On the other hand, interaction with other materials such as SiON inorganic ARCs becomes more challenging in terms of footing behavior, adhesion, and line edge roughness. In this paper, the 193nm processing experience gained at IMEC will be outlined, as well as solutions for manufacturability. Front- end-of-line integration results will also be shown, mainly for gate applications. It will be demonstrated that currently several commercial resist are capable of printing 130nm gates within the +/- 10 percent CD tolerance, even after gate etch. The impact of line edge roughness will also be discussed. Finally, the feasibility of printing 100nm logic patterns using only binary masks has been demonstrated, including gate etch.

  19. [PKP for Keratoconus - From Hand/Motor Trephine to Excimer Laser and Back to Femtosecond Laser].

    PubMed

    Seitz, B; Szentmáry, N; Langenbucher, A; Hager, T; Viestenz, A; Janunts, E; El-Husseiny, M

    2016-06-01

    For patients with keratoconus, rigid gas-permeable contact lenses are the first line correction method and allow good visual acuity for quite some time. In severe stages of the disease with major cone-shaped protrusion of the cornea, even specially designed keratoconus contact lenses are no longer tolerated. If there are contraindications for intrastromal ring segments, corneal transplantation typically has a very good prognosis. In patients with advanced keratoconus - especially after corneal hydrops due to rupture of Descemet's membrane - penetrating keratoplasty (PKP) is still the first line surgical method. Non-contact excimer laser trephination seems to be especially beneficial for eyes with iatrogenic keratectasia after LASIK and for patients with repeat grafts due to "keratoconus recurrences" due to small grafts with thin host cornea. For donor trephination from the epithelial side, an artificial chamber is used. Wound closure is achieved with a double running cross-stitch suture according to Hoffmann. Graft size is adapted individually, depending on corneal size ("as large as possible - as small as necessary"). Limbal centration is preferred intraoperatively, due to optical displacement of the pupil. During the last 10 years, femtosecond laser trephination has been introduced from the USA as a potentially advantageous approach. Prospective clinical studies have shown that the technique of non-contact excimer laser PKP improves donor and recipient centration, reduces "vertical tilt" and "horizontal torsion" of the graft in the recipient bed, and thus results in significantly less "all-sutures-out" keratometric astigmatism (2.8 vs. 5.7 D), more regular topography (surface regularity index [SRI] 0.80 vs. 1.0) and better visual acuity (0.80 vs. 0.60), in comparison to the motor trephine. The stage of the disease does not influence functional outcome after excimer laser PKP. However, the refractive outcome of femtosecond laser keratoplasty resembles that with

  20. A comparison of the characteristics of excimer and femtosecond laser ablation of acrylonitrile butadiene styrene (ABS)

    NASA Astrophysics Data System (ADS)

    See, Tian Long; Liu, Zhu; Li, Lin; Zhong, Xiang Li

    2016-02-01

    This paper presents an investigation on the ablation characteristics of excimer laser (λ = 248 nm, τ = 15 ns) and femtosecond laser (λ = 800 nm, τ = 100 fs) on ABS polymer sheets. The laser-material interaction parameters (ablation threshold, optical penetration depth and incubation factor) and the changes in material chemical properties were evaluated and compared between the two lasers. The work shows that the ablation threshold and effective optical penetration depth values are dependent on the wavelength of laser beam (photon energy) and the pulse width. The ablation threshold value is lower for the excimer laser ablation of ABS (Fth = 0.087 J/cm2) than that for the femtosecond laser ablation of ABS (Fth = 1.576 J/cm2), demonstrating a more dominating role of laser wavelength than the pulse width in influencing the ablation threshold. The ablation depth versus the logarithmic scale of laser fluence shows two linear regions for the fs laser ablation, not previously known for polymers. The effective optical penetration depth value is lower for excimer laser ablation (α-1 = 223 nm) than that for femtosecond laser ablation (α-1 = 2917 nm). The ablation threshold decreases with increasing number of pulses (NOP) due to the chain scission process that shortens the polymeric chains, resulting in a weaker polymeric configuration and the dependency is governed by the incubation factor. Excimer laser treatment of ABS eliminates the Cdbnd C bond completely through the chain scission process whereas Cdbnd C bond is partially eliminated through the femtosecond laser treatment due to the difference in photon energy of the two laser beams. A reduction in the Cdbnd C bond through the chain scission process creates free radical carbons which then form crosslinks with each other or react with oxygen, nitrogen and water in air producing oxygen-rich (Csbnd O and Cdbnd O bond) and nitrogen-rich (Csbnd N) functional groups.

  1. The mechanism of the surface morphology transformation for the carbon nanotube thin film irradiated via excimer laser

    SciTech Connect

    Chien, Yun-Shan; Lee, I-Che; Yang, Po-Yu; Wang, Chao-Lung; Tsai, Wan-Lin; Wang, Kuang-Yu; Chou, Chia-Hsin; Cheng, Huang-Chung

    2013-05-06

    In this paper, the surface morphology transformation of the sprayed carbon nanotube (CNT) thin film irradiated with the excimer laser has been systematically investigated. Under the excimer-laser irradiation, two phenomena, including the annealing and ablation effects, were found to be dependent on the incident laser energy and overlapping ratios. Moreover, the extremely high protrusions would be produced in the interface between the annealing and ablation regions. The mechanism of the CNT thin film under the excimer laser irradiation was, therefore, proposed to derive the surface morphology modifications and the further reinforced crystallinity with proper laser energy densities and overlapping ratios.

  2. Top surface imaging through vapor phase silylation for 193 nm lithography

    NASA Astrophysics Data System (ADS)

    Somervell, Mark Howell

    The microelectronics industry has experienced enormous growth in the recent past. Most of this growth can be attributed to the constantly decreasing size of transistors and integrated circuits. The shrinkage of these devices has been made possible through advances in the photolithographic processes used to print circuit patterns on silicon wafers. Currently, the most advanced photolithographic processes use 193 nm exposure sources, and a variety of lithographic technologies have been investigated for use at this wavelength. This dissertation describes the application of atop surface imaging (TSI) process to 193 nm photolithography. The TSI scheme studied here uses light to modulate the reactivity of a photoresist film toward a silylating agent. Only the top surface of the photoresist is exposed so that polymers having high absorbance at the actinic wavelength can be used. The silylation reaction selectively incorporates silicon into the exposed regions of the photoresist while leaving the unexposed portions unchanged. An oxygen reactive ion etch (RIE) process is then used to transfer the silylated image at the top of the resist through the full photoresist thickness to generate a three-dimensional pattern. Two polymer platforms were studied for use in this system. The first, based on a protected poly(p-hydroxystyrene) resin, was optimized by incorporating different chemical components into the resist, exploring the use of novel silylating agents, and developing RIE processes especially for this photoresist resin. This system is capable of printing high resolution features at relatively low exposure doses, but these features have a large degree of line edge roughness (LER). Experiments indicate that the LER is caused by both the extremely high optical density of this polymer at 193 nm and the low glass transition temperature of the silylated material. As a second platform, certain alicyclic polymers offering both improved transparency and increased glass transition

  3. Particle Generation by Pulsed Excimer Laser Ablation in Liquid: Hollow Structures and Laser-Induced Reactions

    NASA Astrophysics Data System (ADS)

    Yan, Zijie

    2011-12-01

    Pulsed laser ablation of solid targets in liquid media is a powerful method to fabricate micro-/nanoparticles, which has attracted much interest in the past decade. It represents a combinatorial library of constituents and interactions, and one can explore disparate regions of parameter space with outcomes that are impossible to envision a priori. In this work, a pulsed excimer laser (wavelength 248 nm, pulse width 30 ns) has been used to ablate targets in liquid media with varying laser fluences, frequencies, ablation times and surfactants. It is observed that hollow particles could be fabricated by excimer laser ablation of Al, Pt, Zn, Mg, Ag, Si, TiO2, and Nb2O5 in water or aqueous solutions. The hollow particles, with sizes from tens of nanometers to micrometers, may have smooth and continuous shells or have morphologies demonstrating that they were assembled from nanoparticles. A new mechanism has been proposed to explain the formation of these novel particle geometries. They were formed on laser-produced bubbles through bubble interface pinning by laser-produced solid species. Considering the bubble dynamics, thermodynamic and kinetic requirements have been discussed in the mechanism that can explain some phenomena associated with the formation of hollow particles, especially (1) larger particles are more likely to be hollow particles; (2) Mg and Al targets have stronger tendency to generate hollow particles; and (3) the 248 nm excimer laser is more beneficial to fabricate hollow particles in water than other lasers with longer wavelengths. The work has also demonstrated the possiblities to fabricate novel nanostructures through laser-induced reactions. Zn(OH)2/dodecyl sulfate flower-like nanostructures, AgCl cubes, and Ag2O cubes, pyramids, triangular plates, pentagonal rods and bars have been obtained via reactions between laser-produced species with water, electrolyes, or surfactant molecules. The underlying mechanisms of forming these structures have been

  4. Primary success and one-year followup of percutaneous peripheral excimer laser angioplasty

    NASA Astrophysics Data System (ADS)

    Visona, Adriana; Liessi, Guido; Miserocchi, Luigi; Bonanome, Andrea; Lusiani, Luigi; Breggion, Giovanni; Pagnan, Antonio

    1992-08-01

    Excimer laser angioplasty was performed in 59 patients (44 males and 17 females, mean age 63 +/- 9 years, range 39 - 77) affected by peripheral vascular disease. Fifty patients had a total occlusion of the superficial femoral artery, three of the iliac artery, and one of the popliteal artery; seven patients showed a subocclusive stenosis of the superficial femoral artery. A commercial excimer laser (Technolas Max-10) was used at the Xenon-Chloride wavelength of 308 nm. The laser operated at 120 ns pulse length and at 20 Hz repetition rate. Applied energy fluence was 20 mJ/pulse. The energy was delivered through a multifiber catheter, which combines 12 (7F) or 18 (9F) fibers (260 micron diameter each), concentrically arranged. Balloon dilatation was associated in 51 patients. Successful recanalization was obtained in 59 out of 61 patients (97%). Failure to recanalize the occluded arteries occurred in two cases, and was due to dissection. Early thrombosis and reocclusion (within 48 hours) was observed in five patients. The cumulative patency rate was 56% at one year. On the basis of these results, excimer laser assisted angioplasty seems a feasible and safe procedure. However, this technique did not solve the restenosis problem. A wide application of excimer laser as a stand alone approach can be foreseen for treatment of peripheral vascular disease.

  5. Formation of short high-power laser radiation pulses in excimer mediums

    NASA Astrophysics Data System (ADS)

    Losev, V. F., Sr.; Ivanov, N. G.; Panchenko, Yu. N.

    2007-06-01

    Presently an excimer mediums continue are examined as one of variants for formation of powerful and over powerful pulses of laser radiation with duration from units of nanosecond up to tens femtosecond. The researches on such powerful installations as "NIKE" (USA) and << SUPER ASHURA >>, Japan) proceed in this direction. The main advantage of excimer mediums is the opportunity to work in a frequency mode, absence of restriction on the size of active area, high uniformity of a gas working medium, high efficiency (up to 10 %) and wide spectral range of laser radiation (KrF, XeCl ~ 2nm, XeF (C-A), Xe IICl ~ 50-100 nanometers). Research in area of high quality laser beams formation in excimer mediums and its amplification in high power amplifiers are carried out the long time in Institute of High Current Electronics SB RAS, Tomsk, Russia. The wide aperture XeCl laser system of MELS-4k is used for these investigations. Last time we take part in program on development of high power excimer laser system with a petawatt level of power. This system supposes the formation and amplification high quality laser beams with different pulse duration from units of nanosecond up to tens femtosecond. We research the possibility of laser beams formation in excimer mediums with ps-ns pulse duration having the low noise and divergence near to diffraction limit. In other hand, we are developing the wide aperture XeF(C-A) amplifier with optical pump on base electron accelerator. According to our estimations of the XeF(C-A) amplifier based on the converter of e-beam energy to the Xe II* fluorescence at 172 nm will allow to obtain up to 100 TW peak power in a 30 fs pulse.

  6. Temperature sensitivity of an atmospheric Raman lidar system based on a XeF excimer laser

    NASA Technical Reports Server (NTRS)

    Whiteman, David N.; Murphy, William F.; Walsh, Nita W.; Evans, Keith D.

    1993-01-01

    The temperature sensitivity of Raman backscattering from atmospheric nitrogen, oxygen, and water vapor is considered over the range of temperatures expected in the troposphere. These results are applied to the Raman spectrum induced by a XeF excimer laser, which produces three line groups centered at approximately 349, 351, and 353 nm. Bandpass filter characteristics are determined for this case.

  7. Successful use of the excimer laser for generalized psoriasis in an ustekinumab non-responder.

    PubMed

    Malakouti, Mona; Brown, Gabrielle Elena; Sorenson, Eric; Leon, Argentina; Koo, John; Levin, Ethan Charles

    2015-03-01

    Effective treatments for moderate to severe psoriasis are phototherapy and biologics. These treatments are similar in that they both decrease cutaneous immune system hyperactivity yet do so via different mechanisms. Our patient, a 63 year old Asian male had a rapid response to treatment with the high dose excimer laser, having previously failed treatment with 28 weeks of ustekinumab therapy. A pre-treatment biopsy of a psoriatic plaque was found to contain relatively low levels of IFN-γ (Th1) and IL-17 (Th17) secreting T cells. Following treatment with the excimer laser, the patient had a quick improvement in PASI that was reflected by a 3-fold reduction in the number of live T cells found in the post-treatment biopsy. Although ustekinumab and the excimer laser both result in decreased levels of these cytokines, the excimer laser directly causes apoptosis of T cells and induces DNA damage in antigen presenting cells. Thus, the broader effects of phototherapy on immune cells compared to the targeted inhibition of IL-12 and IL-23 by ustekinumab likely account for the superior response observed. PMID:25780961

  8. Excimer v. Nd:YAG: comparative analysis of initial ultrastructural alterations produced by two distinct lasers

    NASA Astrophysics Data System (ADS)

    Nevorotin, Alexey J.

    1990-09-01

    Fine structural alteratious produced iediate1y after irradiation with either XeC1 excimer or Nd:Y.AG laser have been studied in rat liver samples processed histochemically for glucose-6-phosphatase (GP) activity, a marker enzyme for the endoplasmic reticulum (ER) of hepatocytes. General vesiculation of ER along with moderate inactivation of GP was apparent following excimer lazing which contrasted with better structural but poorer enzymatic preservation of ER in the hepatocytes irradiated with Nd:YAG laser. c'i the basis of this and our recent study. (A. Nevorotin, M. Kul 1 . 1989. Arch. Pathol . v. 51, N 7, pp. 63'TO ) a conclus ion is drawn on a potential surgical advantage of excimer laser over its Nd:YAG counterpart due presumably to lesser extent of cellular and macromolecular damage implicative in the process of healing of laser-inflicted lesions. A mechanism of ER vesiculation is considered in the iignt of probable dynamic impact transferred to the ER membranes by excimer irradiation by analogy with other nign energy mechanical forces (e.g. nign gravitation or ultrasonication) known to interfere with membrane structural organization.

  9. [Percutaneous coronary Excimer laser angioplasty in patients with coronary heart disease].

    PubMed

    Karsch, K R; Haase, K K; Mauser, M; Ickrath, O; Voelker, W; Baumbach, A; Seipel, L

    1990-07-01

    To verify the efficacy and safety of percutaneous coronary excimer laser angioplasty in patients with coronary artery disease a prospective study was conducted in 60 patients. The application of laser light was possible in 55 of the 60 patients. A novel 1.4-mm diameter catheter with 20 quartz fibers of 100-microns diameter, each arranged concentrically around a central lumen suitable for an 0.014-inch flexible guide wire was used. The light source was a commercial excimer laser emitting energy at a wavelength of 308 nm, with a pulse duration of 60 ns. The laser was operated at 20 Hz; mean energy transmission was 30 +/- 5 mJ/mm2. In 23 of the 55 patients treated with excimer laser energy the qualitative angiographic results were sufficient. In 32 patients additional balloon angioplasty was necessary, either because of an insufficient result or due to vessel closure after laser ablation. In 47 of the 55 patients control angiography was performed within the 6-month follow-up period. Rate of restenosis was higher in patients treated with laser ablation and subsequent balloon angioplasty (16 of 28) than in patients treated with laser ablation alone (6 of 19). Results of the 6-month observation period suggest that 1) coronary excimer laser angioplasty in combination with subsequent balloon angioplasty results in a considerable increase of the restenosis rate; 2) the exclusive use of laser ablation also results in a restenosis rate comparable to balloon angioplasty alone; and 3) the impact of this new method using improved application systems and higher energy transmission has to be determined in further studies. PMID:2399764

  10. Excimer-pumped alkali vapor lasers: a new class of photoassociation lasers

    NASA Astrophysics Data System (ADS)

    Readle, J. D.; Wagner, C. J.; Verdeyen, J. T.; Spinka, T. M.; Carroll, D. L.; Eden, J. G.

    2010-02-01

    Excimer-pumped alkali vapor lasers (XPALs) are a new class of photoassociation lasers which take advantage of the spectrally broad absorption profiles of alkali-rare gas collision pairs. In these systems, transient alkali-rare gas molecules are photopumped from the thermal continuum to a dissociative X2Σ+ 1/2 interaction potential, subsequently populating the n2P3/2 state of the alkali. The absorption profiles >=5 nm and quantum efficiencies >98% have been observed in oscillator experiments, indicating XPAL compatibility with conventional high power laser diode arrays. An alternative technique for populating the n2P3/2 state is direct photoexcitation on the n2P3/2<--n2S1/2 atomic transition. However, because the XPAL scheme employs an off-resonant optical pump, the strengths of resonantly-enhanced nonlinear processes are minimized. Additionally, the absorption coefficient may be adjusted by altering the number densities of the lasing species and/or perturbers, a valuable asset in the design of large volume, high power lasers. We present an overview of XPAL lasers and their operation, including the characteristics of recently demonstrated systems photopumped with a pulsed dye laser. Lasing has been observed in Cs at both 894 nm and 852 nm by pumping CsAr or CsKr pairs as well as in Rb at 795 nm by pumping RbKr. These results highlight the important role of the perturbing species in determining the strength and position of the excimer absorption profile. It is expected that similar results may be obtained in other gas mixtures as similar collision pair characteristics have historically been observed in a wide variety of transient diatomic species.

  11. Chemical trimming overcoat: an enhancing composition and process for 193nm lithography

    NASA Astrophysics Data System (ADS)

    Liu, Cong; Rowell, Kevin; Joesten, Lori; Baranowski, Paul; Kaur, Irvinder; Huang, Wanyi; Leonard, JoAnne; Jeong, Hae-Mi; Im, Kwang-Hwyi; Estelle, Tom; Cutler, Charlotte; Pohlers, Gerd; Yin, Wenyan; Fallon, Patricia; Li, Mingqi; Jeon, Hyun; Xu, Cheng Bai; Trefonas, Pete

    2016-03-01

    As the critical dimension of devices is approaching the resolution limit of 193nm photo lithography, multiple patterning processes have been developed to print smaller CD and pitch. Multiple patterning and other advanced lithographic processes often require the formation of isolated features such as lines or posts by direct lithographic printing. The formation of isolated features with an acceptable process window, however, can pose a challenge as a result of poor aerial image contrast at defocus. Herein we report a novel Chemical Trimming Overcoat (CTO) as an extra step after lithography that allows us to achieve smaller feature size and better process window.

  12. Radiation sensitive developable bottom anti-reflective coatings (DBARC) for 193nm lithography: first generation

    NASA Astrophysics Data System (ADS)

    Toukhy, Medhat; Oberlander, Joseph; Mullen, Salem; Lu, PingHung; Neisser, Mark

    2007-03-01

    A first generation DBARC applicable for 1 st minimum 193nm lithography is described in this paper. The polymer used in this DBARC is insoluble in the casting solvent of the resist, which is propyleneglycolmonomethyletheracetate (PGMEA). Photo acid generator (PAG) and base extractions from the DBARC coating by the resist casting solvent were examined by the DBARC dissolution rates in the developer, before and after solvent treatments. Although the resist and the DBARC do not appear to intermix, strong interaction between the two is evident by their lithographic performance and dissolution rate study.

  13. Substantial H-atom production from the 193 nm photolysis of triethylaluminum

    NASA Astrophysics Data System (ADS)

    Brum, Jeffrey L.; Deshmukh, Subhash; Koplitz, Brent

    1990-01-01

    The 193 nm irradiation of triethylaluminum (TEA) produces a significant amount of atomic hydrogen. Doppler profiles at Lyman-α (121.6 nm) reveal that the H atoms have little kinetic energy, the mean kinetic energy being ⩽ 0.35 eV. These observations are interpreted in the context of possible photodissociation pathways. The most likely route involves a single-photon absorption followed by dissociation to form the ethyl radical, which can further dissociate to produce C 2H 4 and H.

  14. Preparation and disinfection of root canals by 308-nm excimer laser light

    NASA Astrophysics Data System (ADS)

    Liesenhoff, Tim; Folwaczny, Matthias; Lehn, Norbert

    1994-09-01

    Conventional root canal treatments often fail due to insufficient removal of root canal contents and due to ineffective reduction of bacterial growth. In vitro investigations on the 308 nm excimer laser root canal preparation showed excellent results concerning the preparation quality. The aim of the present study was to investigate the influence of 308 nm excimer laserlight on the growth of bacteria. Bacterial suspensions of Staph. aureus, E. coli, and Enterococcus faec. were irradiated with various energy densities and different time duration. In order to exclude thermal side effects the temperature rise inside the suspensions was registered during irradiation. It was able to demonstrate that 308 nm excimer laserlight effects a log reduction of germ concentration at energy densities of 0.5 - 2.4 J/cm2. Laserlight effects germ reduction even without tissue removal. The effectiveness is dependent on the type of bacteria, the energy density, and the time of irradiation. The antimicrobial effect is independent from temperature.

  15. Mechanism of injurious effect of excimer (308 nm) laser on the cell

    NASA Astrophysics Data System (ADS)

    Nevorotin, Alexey J.; Kallikorm, A. P.; Zeltzer, Gregory L.; Kull, Mart M.; Mihkelsoo, Virgo T.

    1991-06-01

    A Lameta 22710 excimer laser operating at 70 mJ/mm2 per pulse, with pulse duration of 70 nsec, and pulse repetition rate of 10 Hz, equipped with a quartz filament as energy conductor was used to make incisions on rat liver. 2 to 5 sec after irradiation the specimens were fixed and further processed for electron microscopy and histochemical visualization of the endoplasmic reticulum (ER) marker enzyme glucose-6- phosphatase at the ultrastructural level. The additional series were: fixation before irradiation-(A); lasing with Nd:YAG laser (1064 nm, continuous wave mode, 40 J/mm2)-(B); incision with a white-hot steel needle-(C); and incision with an Esto-Rex ultrasound scalpel (66 kHz, 6 Wt, vibration amplitude of 15 micrometers )-(D). The results showed that unlike Series C and B, in which high temperature caused severe damage to all cellular organellae, the excimer action was much more specific. It caused vesiculation of ER without significant injuries to other cellular structures. The analogous effect was noted after US scalpel cutting, thereby allowing a conclusion that a kind of dynamic rather than thermal factor is responsible for the observed phenomenon of vesiculation. The time schedule of vesicle formation and molecular background of membrane transformation is considered in the light of the data of Series A and D, and also on the basis of available information of membrane behavior. Photoablative effect of pulsed excimer laser is thought to be based on chemical decomposition of organic molecules and their ejection from the tissue to the action of high energy photons. Pressure waves (either acoustic or shock) are presumably generated powerful enough to cause tissue and cell damage beyond the site of ablation. Some thermal and fluorescence events are also implicative in biological targets irradiated with excimer lasers. In our previous studies electron histochemistry was employed for the analysis of cellular alterations caused with a continuous wave mode

  16. Comparison of KrF and ArF excimer laser treatment of biopolymer surface

    NASA Astrophysics Data System (ADS)

    Michaljaničová, I.; Slepička, P.; Heitz, J.; Barb, R. A.; Sajdl, P.; Švorčík, V.

    2015-06-01

    The goal of this work was the investigation of the impact of two different excimer lasers on two biocompatible and biodegradable polymers (poly-L-lactide and poly hydroxybutyrate). Both polymers find usage in medical and pharmaceutical fields. The polymers were modified by KrF and ArF excimer lasers. Subsequently the impact on surface morphology, surface chemistry changes, and thermal properties was studied by means of confocal and AFM microscopy, FTIR and XPS spectroscopy and DSC calorimetry. Under the same conditions of laser treatment it was observed that ArF laser causes more significant changes on surface chemistry, surface morphology and pattern formation on the polymers under investigation. The data obtained in this work can be used for a wide range of possible applications, in tissue engineering or in combination with metallization in electronics, e.g. for biosensors.

  17. Spectrally narrowed lasing of a self-injection KrF excimer laser

    NASA Astrophysics Data System (ADS)

    Shimada, Yasuhiro; Wani, Koichi; Miki, Tadaaki; Kawahara, Hidehito; Mimasu, Mutsumi; Ogata, Yoshiro

    1990-08-01

    Spectrally nantwed lasing of a KrF excimer laser has teen ahieved by a self-injection technique using abeam splitter for power extraction aixi intravity etalons for spectral-narrowing. The laser cavity is divithi into an amplifying branch aix! a spectralnarrowing branch. The spectral bandwidth was narrowed to <3pm FWHM with air-sed etalons placed in the spectral-narrowing branch. A laser propagation model was intrOdUced for describing the laser intensity traveling in the laser cavity. The calculated intensityincident onthe intracavityetalons wassmaller thanthat in theconventional Fabry-Perotcavity withplane-parallel mirrors.

  18. Excimer laser absorption on PMMA plate and on cornea: a practical approach using volume luminance

    NASA Astrophysics Data System (ADS)

    Digulescu, Petre P.; Carstocea, Benone D.; Sterian, Livia

    2001-04-01

    Excimer laser refractive surgery used in Ophthalmology in order to treat the human eye refraction problems has been performed over 10 years around the world. However a systematic approach of the physical phenomena and especially of the absorption on the cornea during the laser treatment is missing in the literature and the doctors are usually using empiric nomograms in order to achieve good results. The theoretical approach is difficult because of the complexity of the phenomena interconnected each to the others. The UV excimer laser beam used to controllably ablate the cornea is highly absorbed in the air and also is supplementary absorbed in the plume generated almost instantaneous as consequence of the ablation on the cornea. Because of this non-linear proces the energy of the laser beam delivered to the eye must be calibrated before each intervention on a patient. The purpose of the present work is to develop a mathematical model of the excimer laser absorption on PMMA and on human cornea based on a new physical notion, the Volume Luminance. The Volume Luminance is defined as volume density of the intensity of laser radiation. A brief theory of the Volume Luminance is also presented.

  19. Bioactive glass surface for fiber reinforced composite implants via surface etching by Excimer laser.

    PubMed

    Kulkova, Julia; Moritz, Niko; Huhtinen, Hannu; Mattila, Riina; Donati, Ivan; Marsich, Eleonora; Paoletti, Sergio; Vallittu, Pekka K

    2016-07-01

    Biostable fiber-reinforced composites (FRC) prepared from bisphenol-A-glycidyldimethacrylate (BisGMA)-based thermosets reinforced with E-glass fibers are promising alternatives to metallic implants due to the excellent fatigue resistance and the mechanical properties matching those of bone. Bioactive glass (BG) granules can be incorporated within the polymer matrix to improve the osteointegration of the FRC implants. However, the creation of a viable surface layer using BG granules is technically challenging. In this study, we investigated the potential of Excimer laser ablation to achieve the selective removal of the matrix to expose the surface of BG granules. A UV-vis spectroscopic study was carried out to investigate the differences in the penetration of light in the thermoset matrix and BG. Thereafter, optimal Excimer laser ablation parameters were established. The formation of a calcium phosphate (CaP) layer on the surface of the laser-ablated specimens was verified in simulated body fluid (SBF). In addition, the proliferation of MG63 cells on the surfaces of the laser-ablated specimens was investigated. For the laser-ablated specimens, the pattern of proliferation of MG63 cells was comparable to that in the positive control group (Ti6Al4V). We concluded that Excimer laser ablation has potential for the creation of a bioactive surface on FRC-implants. PMID:27134152

  20. Double-exposure materials for pitch division with 193nm lithography: requirements, results

    NASA Astrophysics Data System (ADS)

    Bristol, Robert; Shykind, David; Kim, Sungwon; Borodovsky, Yan; Schwartz, Evan; Turner, Courtney; Masson, Georgeta; Min, Ke; Esswein, Katherine; Blackwell, James M.; Suetin, Nikolay

    2009-03-01

    We present the results of both theoretical and experimental investigations of materials for application either as a reversible Contrast Enhancement Layer (rCEL) or a Two-Stage PAG. The purpose of these materials is to enable Litho- Litho-Etch (LLE) patterning for Pitch Division (PD) at the 16nm logic node (2013 Manufacturing). For the rCEL, we find from modeling using an E-M solver that such a material must posses a bleaching capability equivalent to a Dill A parameter of greater than 100. This is at least a factor of ten greater than that achieved so far at 193nm by any usable organic material we have tested. In the case of the Two-Stage PAG, analytical and lithographic modeling yields a usable material process window, in terms of reversibility and two-photon vs. one-photon acid production rates (branching ratio). One class of materials, based on the cycloadduct of a tethered pair of anthracenes, has shown promise under testing at 193nm in acetonitrile. Sufficient reversibility without acid production, enabled by near-UV exposure, has been achieved. Acid production as a function of dose shows a clear quadratic component, consistent with a branching ratio greater than 1. The experimental data also supports a acid contrast value of approximately 0.05 that could in principle be obtained with this molecule under a pitch division double-exposure scenario.

  1. Photodissociation dynamics of propyne at 193 nm: a trajectory surface hopping study.

    PubMed

    Ghosh, Subhendu; Rauta, Akshaya Kumar; Maiti, Biswajit

    2016-03-01

    Photodissociation dynamics of propyne at 193 nm are studied using the fewest switches nonadiabatic trajectory surface hopping method on its first excited singlet electronic state (1(1)A''). The trajectories are propagated based on potential energies, gradients and nonadiabatic couplings calculated at the MRCIS(6,7) level with the 6-31++G(d,p) basis set. Our trajectory calculations have revealed that H + H3CCC is the major dissociation channel, which has also been predicted experimentally. For the primary photodissociation channel H + H3CCC we demonstrate that nonadiabatic dynamics do not play a significant role. This observation is however contradictory to most of the previously reported experimental predictions. The calculated product translation energy distribution for the acetylenic H atom elimination peaked at ∼18 kcal mol(-1), indicating that the dissociation occurs adiabatically on a moderately repulsive excited surface that correlates with the ground state products (CH3C[triple bond, length as m-dash]C + H). The H atom elimination process from the methyl fragment involving a transition state, which has to compete with the acetylenic H atom dissociation channel with no barrier in the excited singlet surface, was found to be too less probable to make a contribution to product branching. We observed that a fewer but significant number of trajectories led to CH3 + CCH product formation which has not been observed experimentally when propyne is excited at 193 nm. PMID:26928947

  2. Raman-shifting an ArF excimer laser to generate new lines for obtaining optical diagnostic based information in flow fields

    NASA Technical Reports Server (NTRS)

    Koker, Edmond B.

    1994-01-01

    of the gas near the focal region. Furthermore, since the Raman shifting process is polarization sensitive, it is necessary to have all of the laser energy in a single polarization. These factors were taken into consideration in the execution of the project. The implementation of the Raman shift was accomplished by focusing the 193 nm output of an ArF excimer laser (Lamda-Physik LPX 150) into a 1-meter long high pressure recirculating Raman cell filled with H2 gas. The laser system was modified in order to improve the mode quality of the pump beam to enhance the Raman shifting. To accomplish this feat, a prism beam expander and grating on the oscillator discharge provided wavelength tuning over the excimer gain profile. Furthermore, a triple-pass configuration, as opposed to unstable resonator optics, was employed in the operation of the amplifier cavity so that when the oscillator output radiation, focused by a 51-cm focal length fused silica lens through a 50 micron pinhole (serving as a spatial filter) and recollimated with a 25-cm focal length lens, was fed into the amplifier, it was injection locked, thereby providing tunable radiation with relatively low divergence. The forward scattered radiation emanating from the impingement of the modified pump beam on the Raman cell was detected using an energy meter after the latter had been separated from it using a dispersing prism.

  3. 300 W XeCl excimer laser annealing and sequential lateral solidification in low temperature poly silicon technology

    NASA Astrophysics Data System (ADS)

    Herbst, Ludolf; Kahlert, Hans-Juergen; Fechner, Burkhard; Rebhan, Ulrich; Osmanow, Rustem

    2003-05-01

    Industrial production of low temperature p-Si back plates for LCDs by high power excimer laser annealing was introduced several years ago. Regarding the economy of the process, one of the major advantages of excimer laser annealing is the opportunity to make use of low cost glass substrates due to the low temperature of the annealing process. The Lambda Physik high power excimer laser series are operated with the MicroLas 370 mm line beam optics, integrated by Japan Steel Works into industrial systems. The MicroLas line beam optics for conventional excimer laser annealing (ELA) process converts the raw laser beam profile into a stable and homogeneous rectangular illumination field with high aspect ratio. The excimer laser light source, the LAMBDA STEEL 1000, delivers stabilized pulse energies up to 1 Joule at repetition rates up to 300Hz. The crystallization using excimer lasers allows to produce films with electron mobility of 100-150 cm2/Vsec with the Line beam technique. The new SLS-method, which is currently under industrial investigation, even allows to obtain electron mobility between 200-400 cm2/Vsec.

  4. 193nm immersion lithography for high-performance silicon photonic circuits

    NASA Astrophysics Data System (ADS)

    Selvaraja, Shankar K.; Winroth, Gustaf; Locorotondo, Sabrina; Murdoch, Gayle; Milenin, Alexey; Delvaux, Christie; Ong, Patrick; Pathak, Shibnath; Xie, Weiqiang; Sterckx, Gunther; Lepage, Guy; Van Thourhout, Dries; Bogaerts, Wim; Van Campenhout, Joris; Absil, Philippe

    2014-04-01

    Large-scale photonics integration has been proposed for many years to support the ever increasing requirements for long and short distance communications as well as package-to-package interconnects. Amongst the various technology options, silicon photonics has imposed itself as a promising candidate, relying on CMOS fabrication processes. While silicon photonics can share the technology platform developed for advanced CMOS devices it has specific dimension control requirements. Though the device dimensions are in the order of the wavelength of light used, the tolerance allowed can be less than 1% for certain devices. Achieving this is a challenging task which requires advanced patterning techniques along with process control. Another challenge is identifying an overlapping process window for diverse pattern densities and orientations on a single layer. In this paper, we present key technology challenges faced when using optical lithography for silicon photonics and advantages of using the 193nm immersion lithography system. We report successful demonstration of a modified 28nm- STI-like patterning platform for silicon photonics in 300mm Silicon-On-Insulator wafer technology. By careful process design, within-wafer CD variation (1sigma) of <1% is achieved for both isolated (waveguides) and dense (grating) patterns in silicon. In addition to dimensional control, low sidewall roughness is a crucial to achieve low scattering loss in the waveguides. With this platform, optical propagation loss as low as ~0.7 dB/cm is achieved for high-confinement single mode waveguides (450x220nm). This is an improvement of >20 % from the best propagation loss reported for this cross-section fabricated using e-beam lithography. By using a single-mode low-confinement waveguide geometry the loss is further reduced to ~0.12 dB/cm. Secondly, we present improvement in within-device phase error in wavelength selective devices, a critical parameter which is a direct measure of line

  5. Focused excimer laser initiated, radio frequency sustained high pressure air plasmas

    SciTech Connect

    Giar, Ryan; Scharer, John

    2011-11-15

    Measurements and analysis of air breakdown processes and plasma production by focusing 193 nm, 300 mJ, 15 MW high power laser radiation inside a 6 cm diameter helical radio frequency (RF) coil are presented. Quantum resonant multi-photon ionization (REMPI) and collisional cascade laser ionization processes are exploited that have been shown to produce high-density (n{sub e} {approx} 7 x 10{sup 16}/cm{sup 3}) cylindrical seed plasmas at 760 Torr. Air breakdown in lower pressures (from 7-22 Torr), where REMPI is the dominant laser ionization process, is investigated using an UV 18 cm focal length lens, resulting in a laser flux of 5.5 GW/cm{sup 2} at the focal spot. The focused laser power absorption and associated shock wave produce seed plasmas for sustainment by the RF (5 kW incident power, 1.5 s) pulse. Measurements of the helical RF antenna load impedance in the inductive and capacitive coupling regimes are obtained by measuring the loaded antenna reflection coefficient. A 105 GHz interferometer is used to measure the plasma electron density and collision frequency. Spectroscopic measurements of the plasma and comparison with the SPECAIR code are made to determine translational, rotational, and vibrational neutral temperatures and the associated neutral gas temperature. From this and the associated measurement of the gas pressure the electron temperature is obtained. Experiments show that the laser-formed seed plasma allows RF sustainment at higher initial air pressures (up to 22 Torr) than that obtained via RF-only initiation (<18 Torr) by means of a 0.3 J UV laser pulse.

  6. Simulation of excimer laser micromachined 3D surface using a CAD solid modeling package

    NASA Astrophysics Data System (ADS)

    Hume, Richard G.; Iovenitti, Pio G.; Hayes, Jason P.; Harvey, Erol C.

    2002-11-01

    This paper describes the research on the development of a visualisation tool to generate 3D solid models of structures produced by micromachining using an excimer laser system. Currently, the development of part programs to achieve a desired microstructure is by a trial and error approach. This simulation tool assists designers and excimer machine programmers to produce microstructures using the excimer laser. Users can develop their microstructures and part programs with the assistance of digital prototypes rather than designing products using expensive laser micromachining equipment. The methods to simulate micromachining using the solid modelling package, SolidWorks, are described, and simulation and actual machined examples are reported. A basic knowledge of the solid modelling package is required to develop the simulations, and complex models take time to prepare, however, the development time can be minimised by working from previous simulations. The models developed can be parameterised so that families of designs can be investigated for little additional effort to optimise the design before committing to laser micromachining.

  7. Application of optical tweezers and excimer laser to study protoplast fusion

    NASA Astrophysics Data System (ADS)

    Kantawang, Titirat; Samipak, Sompid; Limtrakul, Jumras; Chattham, Nattaporn

    2015-07-01

    Protoplast fusion is a physical phenomenon that two protoplasts come in contact and fuse together. Doing so, it is possible to combine specific genes from one protoplast to another during fusion such as drought resistance and disease resistance. There are a few possible methods to induce protoplast fusion, for example, electrofusion and chemical fusion. In this study, chemical fusion was performed with laser applied as an external force to enhance rate of fusion and observed under a microscope. Optical tweezers (1064 nm with 100X objective N.A. 1.3) and excimer laser (308 nm LMU-40X-UVB objective) were set with a Nikon Ti-U inverted microscope. Samples were prepared by soaking in hypertonic solution in order to induce cell plasmolysis. Elodea Canadensis and Allium cepa plasmolysed leaves were cut and observed under microscope. Concentration of solution was varied to induce difference turgor pressures on protoplasts pushing at cell wall. Free protoplasts in solution were trapped by optical tweezers to study the effect of Polyethylene glycol (PEG) solution. PEG was diluted by Ca+ solution during the process to induced protoplast cell contact and fusion. Possibility of protoplast fusion by excimer laser was investigated and found possible. Here we report a novel tool for plant cell fusion using excimer laser. Plant growth after cell fusion is currently conducted.

  8. High speed AFM studies of 193 nm immersion photoresists during TMAH development

    NASA Astrophysics Data System (ADS)

    Ngunjiri, Johnpeter; Meyers, Greg; Cameron, Jim; Suzuki, Yasuhiro; Jeon, Hyun; Lee, Dave; Choi, Kwang Mo; Kim, Jung Woo; Im, Kwang-Hwyi; Lim, Hae-Jin

    2016-03-01

    In this paper we report on our studies of the dynamic process of resist development in real time. Using High Speed - Atomic Force Microscopy (HS-AFM) in dilute developer solution, changes in morphology and nanomechanical properties of patterned resist were monitored. The Bruker Dimension FastScan AFMTM was applied to analyze 193 nm acrylic-based immersion resists in developer. HS-AFM operated in Peak Force mapping mode allowed for concurrent measurements of image topography resist stiffness, adhesion to AFM probe and deformation during development. In our studies we focused on HS-AFM topography data as it readily revealed detailed information about initial resist morphology, followed by a resist swelling process and eventual dissolution of the exposed resist areas. HS-AFM showed potential for tracking and understanding development of patterned resist films and can be useful in evaluating the dissolution properties of different resist designs.

  9. Optimization of 193-nm single-layer resists through statistical design

    NASA Astrophysics Data System (ADS)

    Gabor, Allen H.; Dimov, Ognian N.; Medina, Arturo N.; Neisser, Mark O.; Slater, Sydney G.; Wang, Ruey H.; Houlihan, Francis M.; Cirelli, Raymond A.; Dabbagh, Gary; Hutton, Richard S.; Rushkin, Ilya L.; Sweeney, James R.; Timko, Allen G.; Nalamasu, Omkaram; Reichmanis, Elsa

    1999-06-01

    Through a series of statistical design experiments we optimized the lithographic performance of a 193 nm single layer resists based on a norbornene-maleic anhydride matrix resin. Several interesting findings were found including that having the PEB temperature improved the performance of the resist. The polymer composition was found to strongly influence the lithographic performance of the resist. Variables that we examined included acrylate loading and blocking level. By optimizing the composition of the polymer, we have obtained resist with high etch resistance, square profiles and 0.130 micron dense line ultimate resolution in 0.5 micron thick films. The resist formulations are compatible with industry standard 0.262 N TMAH. During exposure the resists does not suffer from the outgassing of volatile species.

  10. Measurement and evaluation methods for beam characterization of commercial excimer lasers

    NASA Astrophysics Data System (ADS)

    Albrecht, Hans Stephen; Rebhan, Ulrich; Mann, Klaus R.; Ohlenbusch, J.

    1996-11-01

    This paper describes the specific requirements for measurement of excimer laser beam profiles for standardized characterization 'of commercial excimer lasers. A corresponding measurement system is presented which allows a simultaneous characterization of energy density distribution in the near field as well as in the focal plane of a lens (far field). Specially adapted UV-cameras make possible sings pulse diagnostic. Beam widths are calculated from the digitized camera data by different methods corresponding to the proposals of ISO 11146 (second moment, moving knife edge, and moving slit) and the results are compared. In particular, the influence of background signals as well as the typical shape of energy density distribution in the near field to the determined beam widths are analyzed.

  11. Improved model for the angular dependence of excimer laser ablation rates in polymer materials

    SciTech Connect

    Pedder, J. E. A.; Holmes, A. S.; Dyer, P. E.

    2009-10-26

    Measurements of the angle-dependent ablation rates of polymers that have applications in microdevice fabrication are reported. A simple model based on Beer's law, including plume absorption, is shown to give good agreement with the experimental findings for polycarbonate and SU8, ablated using the 193 and 248 nm excimer lasers, respectively. The modeling forms a useful tool for designing masks needed to fabricate complex surface relief by ablation.

  12. Phosphorus doping of 4H SiC by liquid immersion excimer laser irradiation

    SciTech Connect

    Ikeda, Akihiro; Nishi, Koji; Ikenoue, Hiroshi; Asano, Tanemasa

    2013-02-04

    Phosphorus doping of 4H SiC is performed by KrF excimer laser irradiation of 4H SiC immersed in phosphoric acid. Phosphorus is incorporated to a depth of a few tens of nanometers at a concentration of over 10{sup 20}/cm{sup 3} without generating significant crystal defects. Formation of a pn junction diode with an ideality factor of 1.06 is demonstrated.

  13. Narrow bandwidth tuning of rhodamine 6G dye pumped by a XeCl excimer laser

    SciTech Connect

    Shangguan Cheng; Ling Ying-yi; Wang Yi-man; Dou Ai-rong; Huang Dan-hong

    1986-03-01

    In this paper the experimental study for narrow bandwidth tuning of ethylene glycol solution of rhodamine 6G pumped by a XeCl excimer laser is reported. The tunable range from 572.7 nm to 612.9 nm with linewidth of 0.004 nm has been obtained. The conversion efficiency is 16.0%. The experimental results of seven other dyes are also presented.

  14. Holographic Generation Of Gratings With Periodicities Below 150 nm With An Excimer Laser

    NASA Astrophysics Data System (ADS)

    Ahlhorn, T.; Pohlmann, Hauke; Kotthaus, Jorg P.

    1989-04-01

    Holographic generation of gratings with periodicities down to 140nm in thin polymethyl methacrylate (PMMA) layers on Si-substrates using a narrow band KrF-excimer laser (λ=248 nm) is reported. At low single pulse energy densities (<3OmJ/cm2) the gratings are prepared by conventional photolithography. At higher single pulse energy densities (>70mJ/cm2) we directly write gratings in the PMMA by photoetching (ablation).

  15. Novel low-reflective index fluoropolymers-based top anti-reflective coatings (TARC) for 193-nm lithography

    NASA Astrophysics Data System (ADS)

    Yamashita, Tsuneo; Hayami, Takashi; Ishikawa, Takuji; Kanemura, Takashi; Aoyama, Hirokazu

    2007-03-01

    Implant lithography, which has up to now utilized 365-nm (i-line) and 248-nm (KrF) light sources, must now turn to 193-nm (ArF) sources. In implant lithography, an anti-reflective material is often used to coat the resist-film. The top anti-reflective coating (abbreviated to TARC) is most often used to reduce CD swing. TARC materials must have low refractive index and water solubility. The TARC materials for used 193-nm use must have very low reflective index and alternatives to perfluorooctylsulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) must be found. We synthesized some novel fluorinated amorphous polymers as 193-nm TARC candidates. Their fundamental properties were characterized, such as transparency and reflective index at 193-nm (wavelength) along with their solubility in water and a standard alkaline developer. High transparency, i.e., k value less than 0.01, and very low reflective index, i.e., lower than n=1.4 at 193-nm wavelength are confirmed. Their dissolution behaviors are studied using the Quartz Crystal Microbalance (QCM) method. In surprise finding, we find that several of the polymers examined, those that have high fluorine content, dissolved in water. Test results show that the proposed polymers can be applied as top anti reflective coatings .

  16. Vessel wall perforation mechanism of the excimer laser-assisted non-occlusive anastomosis technique.

    PubMed

    Bremmer, Jochem; van Doormaal, Tristan P C; Verweij, Bon H; van der Zwan, Albert; Tulleken, Cornelius A F; Verdaasdonk, Rudolf

    2016-08-01

    The excimer laser assisted non-occlusive anastomosis (ELANA) technique is used to make anastomoses on intracerebral arteries. This end-to-side anastomosis is created without temporary occlusion of the recipient artery using a 308-nm excimer laser with a ring-shaped multi-fiber catheter to punch an opening in the arterial wall. Over 500 patients have received an ELANA bypass. However, the vessel wall perforation mechanism of the laser catheter is not known exactly and not 100 % successful. In this study, we aimed to understand the mechanism of ELANA vessel perforation using specialized imaging techniques to ultimately improve its effectiveness. High-speed imaging, high-contrast imaging, and high-sensitivity thermal imaging were used to study the laser wall perforation mechanism and reveal the mechanical and thermal effects involved. In vitro, rabbit arteries were exposed with the special designed laser catheter in a setup representative for the clinical setting, in which blood was replaced with a transparent UV absorbing liquid for visualization. We observed that laser vessel wall perforation was caused by explosive vapor bubbles tearing through the vessel wall, mostly within the first 20 of the total 200 pulses. Thermal effects were minimal. Unsymmetrical tension in the vessel wall inducing migration of the flap during laser exposure was observed in case of unsuccessful wall perforations. The laser wall perforation mechanism in the ELANA technique is primarily mechanical. Symmetric tension in the recipient vessel wall is essential and should be trained by neurosurgeons. PMID:27220531

  17. Expression of Epidermal c-Kit+ of Vitiligo Lesions Is Related to Responses to Excimer Laser

    PubMed Central

    Park, Oun Jae; Han, Ji Su; Lee, Sang Hyung; Park, Chan-Sik; Won, Chong Hyun; Lee, Mi Woo; Choi, Jee Ho

    2016-01-01

    Background The survival and growth of melanocytes are controlled by the binding of stem cell factor to its cell surface receptor c-kit+ (CD117). We have observed that c-kit+ melanocytes existed in some lesions of vitiligo, while Melan A+ cells were absent. Objective To verify possible relation between c-kit+ expression and treatment response in non-segmental vitiligo lesions Methods Skin biopsies were done from the center of the 47 lesions from the 47 patients with non-segmental vitiligo. Expression of c-kit+ and Melan A, and amounts of melanin in the epidermis were assessed in each lesion, and treatment responses to excimer laser were evaluated. Results Thirty-five of the 47 lesions (74.5%) had c-kit+ phenotypes. There was significant difference of c-kit staining value between good responders in 3 months of excimer laser treatment (average of 24 sessions) and the others. Conclusion c-Kit expression in vitiliginous epidermis may be related to better treatment responses to excimer laser. PMID:27489428

  18. Elaboration of excimer lasers dosimetry for bone and meniscus cutting and drilling using optical fibers

    NASA Astrophysics Data System (ADS)

    Jahn, Renate; Dressel, Martin; Neu, Walter; Jungbluth, Karl-Heinz

    1991-05-01

    In order to optimize bone and cartilage ablation, various excimer laser systems at 308 nm wavelength (pulse width 28 ns, 60 ns, 300 ns) and tapered fibers (core diameter 400 micrometers , 600 micrometers , 1000 micrometers ) were combined. By varying the major parameters such as fluence, pulselength, repetition rate, fiber diameter, medium, manner of application (drilling, cutting); analysis was made of the interaction of the excimer laser beam with different organic material (meniscus, bone tissue). More than 300 cuts and drillings have been realized with different parameters. The ablation rate mainly depends on fluence, repetition rate and pulse duration. The achieved ablation rate was 3 micrometers /pulse in bone. The drilling speed of the meniscus was 6 mm/s. The samples showed no carbonization at all, when being cut or drilled in liquid medium. This might be a breakthrough in fiber guided excimer laser surgery. From these and further experiments the authors obtained the dosimetry, which will be the basis for the elaboration of necessary operation guidelines for accident surgery.

  19. Practical resolution enhancement effect by new complete antireflective layer in KrF excimer laser lithography

    NASA Astrophysics Data System (ADS)

    Ogawa, Tohru; Kimura, Mitsumori; Gocho, Tetsuo; Tomo, Yoichi; Tsumori, Toshiro

    1993-08-01

    A new complete anti-reflective layer (ARL) for KrF excimer laser lithography, which becomes an excimer laser lithography to a practical mass production tool beyond 0.35 micrometers rule devices, is developed. This new ARL, whose material is a type of hydro silicon oxynitride film (SiOxNy:H), can be applied to tungsten silicide (W-Si) and even to aluminum silicon (Al- Si) substrates by controlling deposition conditions in plasma enhanced chemical vapor deposition systems. Using this SiOxNy:H film with 30 nm and 25 nm thicknesses on W-Si and Al-Si substrates respectively, critical dimension variations for both substrates are drastically reduced to within 0.02 micrometers for 0.30 micrometers imaging. On actual device structures, with these SiOxNy:H film as an ARL, notching effects by halation are completely reduced. Moreover, these SiOxNy:H film can not only be deposited with topographical uniformity but also etched with conventional SiO2 etching conditions. Another advantage with ARL is a depth of focus enhancement effect. With a SiOxNy:H film depth of focus for the critical dimension is enlarged more than 23% for 0.35 micrometers line and space patterns. Accordingly, practical resolution is enhanced. From the above effect, the limitations of KrF excimer laser lithography for ideal substrate conditions are considered from the point of view of optimal projection lens NA for various feature sizes.

  20. A study of structure formation on PET, PBT, and PS surfaces by excimer laser ablation

    NASA Astrophysics Data System (ADS)

    Kim, Jongdae

    Usually polymer surface treatment is performed to modify surface layers by inserting some functional group and/or by inducing roughness on surfaces to improve their wettability, printability, and adhesion to other polymers or metals. In this work, different polymer surfaces were treated using an excimer laser (LPX 240i, Lambda Physik). Polystyrene, polyethylene terephtalate, and polybutylene terephtalate were chosen as model materials for this study. Films were made by cast film processing and stretched with biaxial stretching machine. With excimer laser treatment on polymer surfaces, it was found that we could produce 1--2 micron size structures depending on material properties and film processing conditions. Materials with lower UV absorption coefficient produced double digit micron size structures, while those with higher UV absorption coefficients produced single digit micron size structures. In all these cases the structures formed only on stretched films. In addition to those microstructure developments, the determination of ablation threshold fluence was of interest mainly for understanding fundamentals of ablation behavior and technical applications. In this study, ablation thresholds were measured by various methods including ablation depth, ablation weight, and ablation sound level measurements. Among these methods, we confirmed that the measurement by ablation sound level gives the most reliable results, because this method is based on single pulse ablation. To understand the ablation phenomenon, and how microstructures can be developed during ablation, different material processing and excimer laser conditions were chosen for experimentation. During our experiments, we observed incubation phenomenon during laser ablation and showed that this incubation was significant for materials with low UV absorption coefficients. Based on UV absorption value change after excimer laser irradiation, we proposed a mechanism to explain the ablation of PS films. From

  1. Composition of the excimer laser-induced plume produced during LASIK refractive surgery

    NASA Astrophysics Data System (ADS)

    Glickman, Randolph D.; Liu, Yun; Mayo, George L.; Baribeau, Alan D.; Starck, Tomy; Bankhead, Tom

    2003-07-01

    Because of concerns about potential hazards to surgical personnel of the plume associated with laser refractive surgery, this study was performed to characterize the composition of such plumes. Filter elements were removed from the smoke evacuator of a VISX S3 excimer laser (filter pore size ~0.3 microns) and from a Mastel Clean Room ( filter pore size ~0.2 microns) used with a LADARVISION excimer laser. The filters from both laser systems captured the laser-induced plumes from multiple, routine, LASIK patient procedures. Some filters were processed for scanning electron microscopy, while others were extracted with methanol and chloroform for biochemical analysis. Both the VISX "Final Air" filter and the Mastel "Clean Room" filter captured material that was not observed in filters that had clean operating room air only passed through them. In the VISX system, air flows through the filter unit parallel to the filter matrix. SEM analysis showed these filters captured discrete particles of 0.3 to 3.0 microns in size. In the Mastel Clean Room unit, air flows orthogonally through the filter, and the filter matrix was heavily layered with captured debris so that individual particles were not readily distinguished. Amino acid analysis and gel electrophoresis of extracted material revealed proteinaceous molecules as large as 5000 molecular weight. Such large molecules in the laser plume are not predicted by the existing theory of photochemical ablation. The presence of relatively large biomolecules may constitute a risk of allergenic reactions in personnel exposed to the plume, and also calls into question the precise mechanism of excimer laser photochemical ablation. Supported by the RMG Research Endowment, and Research to Prevent Blindness

  2. Precision drilling of fused silica with 157-nm excimer laser radiation

    NASA Astrophysics Data System (ADS)

    Temme, Thorsten; Ostendorf, Andreas; Kulik, Christian; Meyer, Klaus

    2003-07-01

    μFor drilling fused silica, mechanical techniques like with diamond drills, ultrasonic machining, sand blasting or water jet machining are used. Also chemical techniques like laser assisted wet etching or thermal drilling with CO2-lasers are established. As an extension of these technologies, the drilling of micro-holes in fused silica with VUV laser radiation is presented here. The high absorption of the 157 nm radiation emitted by the F2 excimer laser and the short pulse duration lead to a material ablation with minimised impact on the surrounding material. Contrary to CO2-laser drilling, a molten and solidified phase around the bore can thus be avoided. The high photon energy of 7.9 eV requires either high purity nitrogen flushing or operation in vacuum, which also effects the processing results. Depending on the required precision, the laser can be used for percussion drilling as well as for excimer laser trepanning, by applying rotating masks. Rotating masks are especially used for high aspect ratio drilling with well defined edges and minimised debris. The technology is suitable particularly for holes with a diameter below 200 μm down to some microns in substrates with less than 200 μm thickness, that can not be achieved with mechanical methods. Drilling times in 200 μm fused silica substrates are in the range of ten seconds, which is sufficient to compete with conventional methods while providing similar or even better accuracy.

  3. The development and progress of XeCl Excimer laser system

    NASA Astrophysics Data System (ADS)

    Zhang, Yongsheng; Ma, Lianying; Wang, Dahui; Zhao, Xueqing; Zhu, Yongxiang; Hu, Yun; Qian, Hang; Shao, Bibo; Yi, Aiping; Liu, Jingru

    2015-05-01

    A large angularly multiplexed XeCl Excimer laser system is under development at the Northwest Institute of Nuclear Technology (NINT). It is designed to explore the technical issues of uniform and controllable target illumination. Short wavelength, uniform and controllable target illumination is the fundamental requirement of high energy density physics research using large laser facility. With broadband, extended light source and multi-beam overlapping techniques, rare gas halide Excimer laser facility will provide uniform target illumination theoretically. Angular multiplexing and image relay techniques are briefly reviewed and some of the limitations are examined to put it more practical. The system consists of a commercial oscillator front end, three gas discharge amplifiers, two electron beam pumped amplifiers and the optics required to relay, encode and decode the laser beam. An 18 lens array targeting optics direct and focus the laser in the vacuum target chamber. The system is operational and currently undergoing tests. The total 18 beams output energy is more than 100J and the pulse width is 7ns (FWHM), the intensities on the target will exceed 1013W/cm2. The aberration of off-axis imaging optics at main amplifier should be minimized to improve the final image quality at the target. Automatic computer controlled alignment of the whole system is vital to efficiency and stability of the laser system, an array of automatic alignment model is under test and will be incorporated in the system soon.

  4. Photochemical and thermal changes in tissue autofluorescence during excimer laser irradiation

    NASA Astrophysics Data System (ADS)

    McAuliffe, Daniel J., Sr.; Jacques, Steven L.; Hayes, Amy S.

    1990-06-01

    A striking consequence of 248-nm excimer laser irradiation of skin is a stable vivid blue fluorescence easily visualized under UVA illumination. Its spectral properties (excitation maximum at "335 nm; emission maximum at ''43O nm) are somewhat similar to those of the fluorescent pigments associated with aging of tissue and peroxidation of lipids, and the fluorescent pigments formed during exposure to high temperatures. This study explores the spectral properties, magnitude, dose response, and laser pulse intensity dependence of this phenomenon in both isolated stratum corneum and epidermal cell suspensions from human skin.

  5. Excimer laser phototherapy for the dissolution of vascular obstruction

    DOEpatents

    Gruen, D.M.; Young, C.E.; Pellin, M.J.

    1984-01-09

    Removal of abnormal human tissue with reduced thermal damage is achieved by selecting a laser having a wavelength in the order of 290 to 400 nm, orienting a laser-transmitting glass member toward the abnormal tissue and directing the laser through the glass member at power densities, pulse rates, and times sufficient to cause multiphoton absorption and bond breaking by Coulomb repulsion rather than thermal destruction. 2 figures.

  6. Advances in hardware, software, and automation for 193nm aerial image measurement systems

    NASA Astrophysics Data System (ADS)

    Zibold, Axel M.; Schmid, R.; Seyfarth, A.; Waechter, M.; Harnisch, W.; Doornmalen, H. v.

    2005-05-01

    A new, second generation AIMS fab 193 system has been developed which is capable of emulating lithographic imaging of any type of reticles such as binary and phase shift masks (PSM) including resolution enhancement technologies (RET) such as optical proximity correction (OPC) or scatter bars. The system emulates the imaging process by adjustment of the lithography equivalent illumination and imaging conditions of 193nm wafer steppers including circular, annular, dipole and quadrupole type illumination modes. The AIMS fab 193 allows a rapid prediction of wafer printability of critical mask features, including dense patterns and contacts, defects or repairs by acquiring through-focus image stacks by means of a CCD camera followed by quantitative image analysis. Moreover the technology can be readily applied to directly determine the process window of a given mask under stepper imaging conditions. Since data acquisition is performed electronically, AIMS in many applications replaces the need for costly and time consuming wafer prints using a wafer stepper/ scanner followed by CD SEM resist or wafer analysis. The AIMS fab 193 second generation system is designed for 193nm lithography mask printing predictability down to the 65nm node. In addition to hardware improvements a new modular AIMS software is introduced allowing for a fully automated operation mode. Multiple pre-defined points can be visited and through-focus AIMS measurements can be executed automatically in a recipe based mode. To increase the effectiveness of the automated operation mode, the throughput of the system to locate the area of interest, and to acquire the through-focus images is increased by almost a factor of two in comparison with the first generation AIMS systems. In addition a new software plug-in concept is realised for the tools. One new feature has been successfully introduced as "Global CD Map", enabling automated investigation of global mask quality based on the local determination of

  7. Excimer laser phototherapy for the dissolution of abnormal growth

    DOEpatents

    Gruen, Dieter M.; Young, Charles E.; Pellin, Michael J.

    1987-01-01

    Removal of abnormal human tissue with reduced thermal damage is achieved by selecting a laser having a wavelength in the order of 290-400 nm, orienting a laser-transmitting glass member toward the abnormal tissue and directing the laser through the glass member at power densities, pulse rates, and times sufficient to cause multiphoton absorption and bond breaking by Coulomb repulsion rather than thermal destruction. The glass member may include a laser beam concentrator provided by a lens or cone at the tissue-treatment end to increase the beam energy per unit area and reduce the treatment area.

  8. Excimer laser phototherapy for the dissolution of abnormal growth

    DOEpatents

    Gruen, D.M.; Young, C.E.; Pellin, M.J.

    1985-02-19

    Removal of abnormal human tissue with reduced thermal damage is achieved by selecting a laser having a wavelength in the order of 290 to 400 nm, orienting a laser-transmitting glass member toward the abnormal tissue and directing the laser through the glass member at power densities, pulse rates, and times sufficient to cause multiphoton absorption and bond breaking by Coulomb repulsion rather than thermal destruction. The glass member may include a laser beam concentrator provided by a lens or cone at the tissue-treatment end to increase the beam energy per unit area and reduce the treatment area. 6 figs.

  9. Beam pen lithography based on focused laser diode beam with single microlens fabricated by excimer laser.

    PubMed

    Hasan, Md Nazmul; Lee, Yung-Chun

    2015-02-23

    A method is proposed to minimize the focused spot size of an elliptically-diverging laser diode beam by means of a circular aperture and a single plano-convex aspherical microlens. The proposed microlens is fabricated using an excimer laser dragging method and has two different profiles in the x- and y-axis directions. The focused spot size of the beam is examined both numerically and experimentally. The feasibility of the proposed approach for beam pen lithography applications is demonstrated by patterning dotted, straight-line and spiral features on a photo resist layer followed by thin gold layer deposition and metal lift-off. The minimum feature size for dotted pattern is around 2.57 μm, while the minimum line-widths for straight-line and spiral pattern are 3.05 μm and 4.35 μm, respectively. Thus, the technique can be applied to write any arbitrary pattern for high-resolution lithography. PMID:25836486

  10. Formation of a narrow beam from an excimer laser pumped by gamma rays

    SciTech Connect

    Lazhintsev, B V; Nor-Arevyan, V A

    2002-06-30

    A laser pumped by a travelling gamma-radiation wave and consisting of a cylindrical part forming spontaneous superradiation and a conical amplifier is considered. The energy parameters of an excimer conical KrF amplifier are investigated. The factors influencing the divergence of induced radiation at the output of the conical amplifier are analysed for various durations of a pump pulse. It is shown that the divergence of radiation emitted by the laser with an active medium length of 10 m may be as high as 10{sup -4} rad. The scheme of laser-beam focusing on the target for the purposes of laser-induced fusion is considered. (control of laser radiation parameters)

  11. Photodissociation of the Propargyl (C3D3) Radicals at 248 nm and 193 nm

    SciTech Connect

    Neumark., D.M.; Crider, P.E.; Castiglioni, L.; Kautzman, K.K.

    2009-01-21

    The photodissociation of perdeuterated propargyl (D{sub 2}CCCD) and propynyl (D{sub 3}CCC) radicals was investigated using fast beam photofragment translational spectroscopy. Radicals were produced from their respective anions by photodetachment at 540 nm and 450 nm (below and above the electron affinity of propynyl). The radicals were then photodissociated by 248 nm or 193 nm light. The recoiling photofragments were detected in coincidence with a time- and position-sensitive detector. Three channels were observed: D{sub 2} loss, CD + C{sub 2}D{sub 2}, and CD{sub 3} + C{sub 2}. Obervation of the D loss channel was incompatible with this experiment and was not attempted. Our translational energy distributions for D{sub 2} loss peaked at nonzero translational energy, consistent with ground state dissociation over small (< 1 eV) exit barriers with respect to separated products. Translational energy distributions for the two heavy channels peaked near zero kinetic energy, indicating dissociation on the ground state in the absence of exit barriers.

  12. 193 nm Ultraviolet Photodissociation Mass Spectrometry for Phosphopeptide Characterization in the Positive and Negative Ion Modes.

    PubMed

    Robinson, Michelle R; Taliaferro, Juliana M; Dalby, Kevin N; Brodbelt, Jennifer S

    2016-08-01

    Advances in liquid chromatography tandem mass spectrometry (LC-MS/MS) have permitted phosphoproteomic analysis on a grand scale, but ongoing challenges specifically associated with confident phosphate localization continue to motivate the development of new fragmentation techniques. In the present study, ultraviolet photodissociation (UVPD) at 193 nm is evaluated for the characterization of phosphopeptides in both positive and negative ion modes. Compared to the more standard higher energy collisional dissociation (HCD), UVPD provided more extensive fragmentation with improved phosphate retention on product ions. Negative mode UVPD showed particular merit for detecting and sequencing highly acidic phosphopeptides from alpha and beta casein, but was not as robust for larger scale analysis because of lower ionization efficiencies in the negative mode. HeLa and HCC70 cell lysates were analyzed by both UVPD and HCD. While HCD identified more phosphopeptides and proteins compared to UVPD, the unique matches from UVPD analysis could be combined with the HCD data set to improve the overall depth of coverage compared to either method alone. PMID:27425180

  13. Tuning and simulating a 193-nm resist for 2D applications

    NASA Astrophysics Data System (ADS)

    Howard, William B.; Wiaux, Vincent; Ercken, Monique; Bui, Bang; Byers, Jeff D.; Pochkowski, Mike

    2002-07-01

    For some applications, the usefulness of lithography simulation results depends strongly on the matching between experimental conditions and the simulation input parameters. If this matching is optimized and other sources of error are minimized, then the lithography model can be used to explain printed wafer experimental results. Further, simulation can be useful in predicting the results or in choosing the correct set of experiments. In this paper, PROLITH and ProDATA AutoTune were used to systematically vary simulation input parameters to match measured results on printed wafers used in a 193 nm process. The validity of the simulation parameters was then checked using 3D simulation compared to 2D top-down SEM images. The quality of matching was evaluated using the 1D metrics of average gate CD and Line End Shortening (LES). To ensure the most accurate simulation, a new approach was taken to create a compound mask from GDSII contextual information surrounding an accurate SEM image of the reticle region of interest. Corrections were made to account for all metrology offsets.

  14. The stability of allyl radicals following the photodissociation of allyl iodide at 193 nm.

    SciTech Connect

    Fan, H.; Pratt, S. T.; Chemistry

    2006-01-01

    The photodissociation of allyl iodide (C{sub 3}H{sub 5}I) at 193 nm was investigated by using a combination of vacuum-ultraviolet photoionization of the allyl radical, resonant multiphoton ionization of the iodine atoms, and velocity map imaging. The data provide insight into the primary C-I bond fission process and into the dissociative ionization of the allyl radical to produce C{sub 3}H{sup 3+}. The experimental results are consistent with the earlier results of Szpunar et al. [J. Chem. Phys. 119, 5078 (2003)], in that some allyl radicals with internal energies higher than the secondary dissociation barrier are found to be stable. This stability results from the partitioning of available energy between the rotational and vibrational degrees of freedom of the radical, the effects of a centrifugal barrier along the reaction coordinate, and the effects of the kinetic shift in the secondary dissociation of the allyl radical. The present results suggest that the primary dissociation of allyl iodide to allyl radicals plus I*({sup 2}P{sub 1/2}) is more important than previously suspected.

  15. The stability of allyl radicals following the photodissociation of allyl iodide at 193 nm.

    PubMed

    Fan, H; Pratt, S T

    2006-10-14

    The photodissociation of allyl iodide (C3H5I) at 193 nm was investigated by using a combination of vacuum-ultraviolet photoionization of the allyl radical, resonant multiphoton ionization of the iodine atoms, and velocity map imaging. The data provide insight into the primary C-I bond fission process and into the dissociative ionization of the allyl radical to produce C3H3+. The experimental results are consistent with the earlier results of Szpunar et al. [J. Chem. Phys. 119, 5078 (2003)], in that some allyl radicals with internal energies higher than the secondary dissociation barrier are found to be stable. This stability results from the partitioning of available energy between the rotational and vibrational degrees of freedom of the radical, the effects of a centrifugal barrier along the reaction coordinate, and the effects of the kinetic shift in the secondary dissociation of the allyl radical. The present results suggest that the primary dissociation of allyl iodide to allyl radicals plus I*(2P(1/2)) is more important than previously suspected. PMID:17042585

  16. Mechanisms involved in HBr and Ar cure plasma treatments applied to 193 nm photoresists

    NASA Astrophysics Data System (ADS)

    Pargon, E.; Menguelti, K.; Martin, M.; Bazin, A.; Chaix-Pluchery, O.; Sourd, C.; Derrough, S.; Lill, T.; Joubert, O.

    2009-05-01

    In this article, we have performed detailed investigations of the 193 nm photoresist transformations after exposure to the so-called HBr and Ar plasma cure treatments using various characterization techniques (x-ray photoelectron spectroscopy, Fourier transformed infrared, Raman analyses, and ellipsometry). By using windows with different cutoff wavelengths patched on the photoresist film, the role of the plasma vacuum ultraviolet (VUV) light on the resist modifications is clearly outlined and distinguished from the role of radicals and ions from the plasma. The analyses reveal that both plasma cure treatments induce severe surface and bulk chemical modifications of the resist films. The synergistic effects of low energetic ion bombardment and VUV plasma light lead to surface graphitization or cross-linking (on the order of 10 nm), while the plasma VUV light (110-210 nm) is clearly identified as being responsible for ester and lactone group removal from the resist bulk. As the resist modification depth depends strongly on the wavelength penetration into the material, it is found that HBr plasma cure that emits near 160-170 nm can chemically modify the photoresist through its entire thickness (240 nm), while the impact of Ar plasmas emitting near 100 nm is more limited. In the case of HBr cure treatment, Raman and ellipsometry analyses reveal the formation of sp2 carbon atoms in the resist bulk, certainly thanks to hydrogen diffusion through the resist film assisted by the VUV plasma light.

  17. Mechanisms involved in HBr and Ar cure plasma treatments applied to 193 nm photoresists

    SciTech Connect

    Pargon, E.; Menguelti, K.; Martin, M.; Bazin, A.; Joubert, O.; Lill, T.

    2009-05-01

    In this article, we have performed detailed investigations of the 193 nm photoresist transformations after exposure to the so-called HBr and Ar plasma cure treatments using various characterization techniques (x-ray photoelectron spectroscopy, Fourier transformed infrared, Raman analyses, and ellipsometry). By using windows with different cutoff wavelengths patched on the photoresist film, the role of the plasma vacuum ultraviolet (VUV) light on the resist modifications is clearly outlined and distinguished from the role of radicals and ions from the plasma. The analyses reveal that both plasma cure treatments induce severe surface and bulk chemical modifications of the resist films. The synergistic effects of low energetic ion bombardment and VUV plasma light lead to surface graphitization or cross-linking (on the order of 10 nm), while the plasma VUV light (110-210 nm) is clearly identified as being responsible for ester and lactone group removal from the resist bulk. As the resist modification depth depends strongly on the wavelength penetration into the material, it is found that HBr plasma cure that emits near 160-170 nm can chemically modify the photoresist through its entire thickness (240 nm), while the impact of Ar plasmas emitting near 100 nm is more limited. In the case of HBr cure treatment, Raman and ellipsometry analyses reveal the formation of sp{sup 2} carbon atoms in the resist bulk, certainly thanks to hydrogen diffusion through the resist film assisted by the VUV plasma light.

  18. Top-coatless 193nm positive-tone development immersion resist for logic application

    NASA Astrophysics Data System (ADS)

    Liu, Lian Cong; Yeh, Tsung Ju; Lin, Yeh-Sheng; Huang, Yu Chin; Kuo, Chien Wen; Huang, Wen Liang; Lin, Chia Hung; Yu, Chun Chi; Hsu, Ray; Wan, I.-Yuan; Lin, Jeff; Im, Kwang-Hwyi; Lim, Hae Jin; Jeon, Hyun K.; Suzuki, Yasuhiro; Xu, Cheng Bai

    2015-03-01

    In this paper, we summarize our development efforts for a top-coatless 193nm immersion positive tone development (PTD) contact hole (C/H) resist with improved litho and defect performances for logic application specifically with an advance node. The ultimate performance goal was to improve the depth of focus (DoF) margin, mask error enhancement factor (MEEF), critical dimension uniformity (CDU), contact edge roughness (CER), and defect performance. Also, the through pitch CD difference was supposed to be comparable to the previous control resist. Effects of polymer and PAG properties have been evaluated for this purpose. The material properties focused in the evaluation study were polymer activation energy (Ea), polymer solubility differentiated by polymerization process types, and diffusion length (DL) and acidity (pKa) of photoacid generator (PAG). Additionally, the impact of post exposure bake (PEB) temperature was investigated for process condition optimization. As a result of this study, a new resist formulation to satisfy all litho and defect performance was developed and production yield was further improved.

  19. 193nm single layer photoresists: defeating tradeoffs with a new class of fluoropolymers

    NASA Astrophysics Data System (ADS)

    Varanasi, Pushkara R.; Kwong, Ranee W.; Khojasteh, Mahmoud; Patel, Kaushal; Chen, Kuang-Jung; Li, Wenjie; Lawson, M. C.; Allen, Robert D.; Sooriyakumaran, Ratnam; Brock, P.; Sundberg, Linda K.; Slezak, Mark; Dabbagh, Gary; Liu, Z.; Nishimura, Yukio; Chiba, Takashi; Shimokawa, Tsutomu

    2005-05-01

    The focus of this paper is to utilize the acidity of hexafluoroalcohol (HFA) in addressing performance deficiencies associated with current 193nm methacrylate resist materials. In this study, we have designed and developed a variety of HFA pendant methacrylate monomers and the corresponding imaging polymers for ArF lithography. It was shown that typical swelling behavior observed in methacrylate resists can be substantially reduced or eliminated by replacing commonly used multicylcic lactone polar functionalities with acidic HFA side chains. The incorporation of aliphatic spacers between HFA and polymer backbone were found to be more effective than cyclic hindered moieties, in achieving linear dissolution characteristics. The typical poor etch stability associated with fluorine atoms in HFA can be substantially minimized by designing side chains with a combination of appropriate cyclic and aliphatic moieties and fine-tuning the corresponding polymer compositions. PEB sensitivity of high activation energy protecting group (e.g., methyladamentyl group) based methacrylate resists can be substantially improved through the incorporation of acidic HFA side chains (6nm/C to <1 nm/C). The key application space for HFA-methacrylate resists appears to be trench level lithography. It was also demonstrated that these HFA materials are compatible with immersion lithography and result in dramatically improved process windows for iso trench features, in addition to other lines/space features.

  20. Surface modification of polytetrafluoroethylene by excimer-laser radiation

    SciTech Connect

    Nishii, M.; Sugimoto, S.; Shimizu, Y.; Suzuki, N.; Kewanishi, S.; Nagese, T.; Endo, M.; Eguchi, Y.

    1993-12-31

    The adhesive strength of polytetrafluoroethylene (PTFE) films was enhanced remarkably by KrF-laser irradiation in air when a small amount of aromatic polymers such as aromatic polyester, polyetheretherketone and polyimide were blended with PTFE. From the surface analysis of the laser-irradiated PTFE by an X-ray photoelectron spectroscopy and a scanning electron microscopy, it was found that the enhancement in the adhesive properties was attributable to both the chemical effect owing to the formation of the polar groups such as carbonyl group and ethylene linkage and the physical one owing to the formation of the uneveness by the KrF-laser irradiation.

  1. Finite element simulation for ultraviolet excimer laser processing of patterned Si/SiGe/Si(100) heterostructures

    SciTech Connect

    Conde, J. C.; Chiussi, S.; Gontad, F.; Gonzalez, P.; Martin, E.; Serra, C.

    2010-07-05

    Ultraviolet (UV) Excimer laser assisted processing is an alternative strategy for producing patterned silicon germanium heterostructures. We numerically analyzed the effects caused by pulsed 193 Excimer laser radiation impinging on patterned amorphous hydrogenated silicon (a-Si:H) and germanium (a-Ge:H) bilayers deposited on a crystalline silicon substrate [Si(100)]. The proposed two dimensional axisymmetric numerical model allowed us to estimate the temperature and concentration gradients caused by the laser induced rapid melting and solidification processes. Energy density dependence of maximum melting depth and melting time evolution as well as three dimensional temperature and element distribution have been simulated and compared with experimentally obtained results.

  2. XeCl excimer laser with new prism resonator configurations and its performance characteristics

    SciTech Connect

    Benerji, N. S. E-mail: bsingh@rrcat.gov.in; Singh, A.; Varshnay, N.; Singh, Bijendra E-mail: bsingh@rrcat.gov.in

    2015-07-15

    New resonator cavity configurations, namely, the prism resonator and unstable prism resonator, are demonstrated for the first time in an excimer (XeCl) laser with interesting and novel results. High misalignment tolerance ∼50 mrad is achieved with considerably reduced beam divergence of less than ∼1 mrad without reduction in output power capabilities of the laser. The misalignment tolerance of ∼50 mrad is a dramatic improvement of ∼25 times compared to ∼2 mrad normally observed in standard excimer laser with plane-plane cavity. Increase in depth of focus from 3 mm to 5.5 mm was also achieved in case of prism resonator configuration with an improvement of about 60%. Unstable prism resonator configuration is demonstrated here in this paper with further reduction in beam divergence to about 0.5 mrad using plano-convex lens as output coupler. The misalignment tolerance in case of unstable prism resonator was retained at about 30 mrad which is a high value compared to standard unstable resonators. The output beam spot was completely filled with flat-top profile with prism resonator configurations, which is desired for various material processing applications. Focusing properties and beam divergence in case of prism resonator have been investigated using SEM (scanning electron microscope) images. SEM images of the focused spot size (∼20 μm holes) on metal sheet indicate beam divergence of about 0.05 mrad which is about 1.5 times diffraction limit. Energy contained in this angle is thus sufficient for micro-machining applications. Clean and sharp edges of the micro-holes show high pointing stability with multiple shot exposures. Such characteristics of the excimer laser system will be extremely useful in micro-machining and other field applications.

  3. XeCl excimer laser with new prism resonator configurations and its performance characteristics.

    PubMed

    Benerji, N S; Singh, A; Varshnay, N; Singh, Bijendra

    2015-07-01

    New resonator cavity configurations, namely, the prism resonator and unstable prism resonator, are demonstrated for the first time in an excimer (XeCl) laser with interesting and novel results. High misalignment tolerance ∼50 mrad is achieved with considerably reduced beam divergence of less than ∼1 mrad without reduction in output power capabilities of the laser. The misalignment tolerance of ∼50 mrad is a dramatic improvement of ∼25 times compared to ∼2 mrad normally observed in standard excimer laser with plane-plane cavity. Increase in depth of focus from 3 mm to 5.5 mm was also achieved in case of prism resonator configuration with an improvement of about 60%. Unstable prism resonator configuration is demonstrated here in this paper with further reduction in beam divergence to about 0.5 mrad using plano-convex lens as output coupler. The misalignment tolerance in case of unstable prism resonator was retained at about 30 mrad which is a high value compared to standard unstable resonators. The output beam spot was completely filled with flat-top profile with prism resonator configurations, which is desired for various material processing applications. Focusing properties and beam divergence in case of prism resonator have been investigated using SEM (scanning electron microscope) images. SEM images of the focused spot size (∼20 μm holes) on metal sheet indicate beam divergence of about 0.05 mrad which is about 1.5 times diffraction limit. Energy contained in this angle is thus sufficient for micro-machining applications. Clean and sharp edges of the micro-holes show high pointing stability with multiple shot exposures. Such characteristics of the excimer laser system will be extremely useful in micro-machining and other field applications. PMID:26233361

  4. Excimer laser coronary angioplasty: experience with a prototype multifibre catheter in patients with stable angina pectoris.

    PubMed

    Kochs, M; Haerer, W; Eggeling, T; Hoeher, M; Schmidt, A; Hombach, V

    1992-03-01

    Percutaneous excimer laser coronary angioplasty (ELCA) was performed in a first group of 20 patients with stable angina pectoris caused by significant coronary stenosis, and long-term follow-up was evaluated. Prototype 4 to 5.5 French multifibre catheters with 18-20 quartz fibres of 100 microns diameter, concentrically arranged around a central lumen for taking up a guide wire, were coupled to a commercial XeCl excimer laser. Energy was delivered at a wavelength of 308 nm with a pulse duration of 60 or 120 ns. Operating at a repetition rate of 20 Hz, mean energy transmission was 13.4 +/- 6.8 mJ per pulse. In all but one patient the lesion could be passed by the catheter. Percent diameter stenosis decreased from 77.1 +/- 10.8% to 53.1 +/- 11.8% after ELCA. Complications were frequently observed, intracoronary thrombus formation in eight instances, dissection in six patients and spasm in five cases, causing total vessel occlusion in five procedures. All complications could be managed efficaciously by thrombolytic and vasodilating drugs and/or balloon angioplasty. Subsequent PTCA was performed in case of complication or insufficient stenosis reduction after ELCA in 18 patients with adequate results (residual stenosis, 28.5 +/- 10.2%). Long-term follow-up angiography, which could be performed in 16 of 19 laser treatments, demonstrated significant restenosis in only three patients. Our preliminary results suggest that, using ELCA, ablation of atherosclerotic lesions is feasible in most cases. However, compared with PTCA, stenosis reduction is significantly less, and the acute complication rate is much higher. Thus, further improvements of the catheter system are necessary in order to realize the advantages of excimer laser ablation, which can be demonstrated by experimental studies. PMID:1597220

  5. Random noise can help to improve synchronization of excimer laser pulses

    PubMed Central

    Mingesz, Róbert; Barna, Angéla; Mellár, János

    2016-01-01

    Recently, we have reported on a compact microcontroller-based unit developed to accurately synchronize excimer laser pulses (Mingesz et al. 2012 Fluct. Noise Lett. 11, 1240007 (doi:10.1142/S021947751240007X)). We have shown that dithering based on random jitter noise plus pseudorandom numbers can be used in the digital control system to radically reduce the long-term drift of the laser pulse from the trigger and to improve the accuracy of the synchronization. In this update paper, we present our new experimental results obtained by the use of the delay-controller unit to tune the timing of a KrF excimer laser as an addition to our previous numerical simulation results. The hardware was interfaced to the laser using optical signal paths in order to reduce sensitivity to electromagnetic interference and the control algorithm tested by simulations was applied in the experiments. We have found that the system is able to reduce the delay uncertainty very close to the theoretical limit and performs well in real applications. The simple, compact and flexible system is universal enough to also be used in various multidisciplinary applications. PMID:26998325

  6. Random noise can help to improve synchronization of excimer laser pulses.

    PubMed

    Mingesz, Róbert; Barna, Angéla; Gingl, Zoltán; Mellár, János

    2016-02-01

    Recently, we have reported on a compact microcontroller-based unit developed to accurately synchronize excimer laser pulses (Mingesz et al. 2012 Fluct. Noise Lett. 11, 1240007 (doi:10.1142/S021947751240007X)). We have shown that dithering based on random jitter noise plus pseudorandom numbers can be used in the digital control system to radically reduce the long-term drift of the laser pulse from the trigger and to improve the accuracy of the synchronization. In this update paper, we present our new experimental results obtained by the use of the delay-controller unit to tune the timing of a KrF excimer laser as an addition to our previous numerical simulation results. The hardware was interfaced to the laser using optical signal paths in order to reduce sensitivity to electromagnetic interference and the control algorithm tested by simulations was applied in the experiments. We have found that the system is able to reduce the delay uncertainty very close to the theoretical limit and performs well in real applications. The simple, compact and flexible system is universal enough to also be used in various multidisciplinary applications. PMID:26998325

  7. Effects of xenon gas on generation and propagation of shock waves in the cavity of excimer laser

    NASA Astrophysics Data System (ADS)

    Kosugi, Shinichiroh; Maeno, Kazuo; Honma, Hiroki

    1993-05-01

    High repetition rate excimer lasers are expected for wide industrial application. The power of excimer laser, however, decreases rapidly in a higher repetition rate operation. Shock or acoustic waves, which are caused by the periodic pulse discharge, may limit the repetition rate of an excimer laser up to 2.5 kHz. Such waves cause inhomogeneity of gas density in the discharge region of the excimer laser. In high repetition rate operation this inhomogeneity remains at the next discharge. Arcing may be generated by this inhomogeneity and the homogeneous excitation of the laser gas is obstructed. Although these phenomena have been reported, the research for the effects of shock waves has remained insufficient. And the relation between these shock waves and discharge phenomena has not been clarified. To resolve this problem, we developed a scaling model chamber of a UV preionized excimer laser cavity with windows for flow visualization. We report the first result by using this model and Schlieren technique in a pure helium gas case. In our experiment three types of shock waves are found in the discharge cavity. Those shock waves are generated from the boundary of the main discharge area, from sparking pin gaps, and from the main electrode surfaces. In this study we focus on the effect of xenon gas on the generation and the propagation of shock waves. Components of the Xe-Cl excimer laser gas are helium, xenon, and hydrogen chloride. In those gases xenon has the largest molecular weight of 131.29. So we conclude xenon plays an important role in the shock wave propagation and in discharge phenomenon.

  8. Coloring linens with excimer lasers to simulate the body image of the Turin Shroud.

    PubMed

    Baldacchini, Giuseppe; Di Lazzaro, Paolo; Murra, Daniele; Fanti, Giulio

    2008-03-20

    The body image of the Turin Shroud has not yet been explained by traditional science; so a great interest in a possible mechanism of image formation still exists. We present preliminary results of excimer laser irradiation (wavelength of 308 nm) of a raw linen fabric and of a linen cloth. The permanent coloration of both linens is a threshold effect of the laser beam intensity, and it can be achieved only in a narrow range of irradiation parameters, which are strongly dependent on the pulse width and time sequence of laser shots. We also obtained the first direct evidence of latent images impressed on linen that appear in a relatively long period (one year) after laser irradiation that at first did not generate a clear image. The results are compared with the characteristics of the Turin Shroud, reflecting the possibility that a burst of directional ultraviolet radiation may have played a role in the formation of the Shroud image. PMID:18709075

  9. Multi-level diffractive optical elements produced by excimer laser ablation of sol-gel.

    PubMed

    Neiss, Estelle; Flury, Manuel; Mager, Loïc; Rehspringer, Jean-Luc; Fort, Alain; Montgomery, Paul; Gérard, Philippe; Fontaine, Joël; Robert, Stéphane

    2008-09-01

    Material ablation by excimer laser micromachining is a promising approach for structuring sol-gel materials as we demonstrate in the present study. Using the well-known direct etching technique, the behaviour of different hybrid organic/inorganic self-made sol-gel materials is examined with a KrF* laser. Ablated depths ranging from 0.1 to 1.5 microm are obtained with a few laser pulses at low fluence (< 1 J/cm(2)). The aim is to rapidly transfer surface relief multi-level diffractive patterns in such a substrate, without intermediate steps. The combination with the 3D profilometry technique of coherence probe microscopy permits to analyse the etching process with the aim of producing multi-level Diffractive Optical Elements (DOE). Examples of four-level DOEs with 10 microm square elementary cells are presented, as well as their laser reconstructions in the infrared. PMID:18773015

  10. Coloring linens with excimer lasers to simulate the body image of the Turin Shroud

    NASA Astrophysics Data System (ADS)

    Baldacchini, Giuseppe; di Lazzaro, Paolo; Murra, Daniele; Fanti, Giulio

    2008-03-01

    The body image of the Turin Shroud has not yet been explained by traditional science; so a great interest in a possible mechanism of image formation still exists. We present preliminary results of excimer laser irradiation (wavelength of 308 nm) of a raw linen fabric and of a linen cloth. The permanent coloration of both linens is a threshold effect of the laser beam intensity, and it can be achieved only in a narrow range of irradiation parameters, which are strongly dependent on the pulse width and time sequence of laser shots. We also obtained the first direct evidence of latent images impressed on linen that appear in a relatively long period (one year) after laser irradiation that at first did not generate a clear image. The results are compared with the characteristics of the Turin Shroud, reflecting the possibility that a burst of directional ultraviolet radiation may have played a role in the formation of the Shroud image.

  11. Combination Of Narrow Bandwidth Excimer Laser And Monochromatic Reduction Projection Lens

    NASA Astrophysics Data System (ADS)

    Kajiyama, K.; Saito, K.; Moro, N.; Maeda, Y.; Natsuaki, H.

    1988-01-01

    This paper will discuss the problems associated with excimer laser photo-lithography -the combination of a KrF narrow band width excimer laser (non-injection locked type) with a large field fused silica monochromatic reduction lens. An excimer laser with a KrF narrow bandwidth, in combination with a large field monochromatic lens which is appropriate for use with such laser, have been developed and tested. The system's resolution capability has been confirmed at 0.4 um L/S with MP2400 resist. The laser has been designed so as to be installed and maintained in a clean room environment as well as to have a very narrow spectrum line. A very narrow band-width beam, down to 0.003nm, has been attained through a stable resonator with more than 20mJ pulse energy. The ultra-compact laser head (300mm x 545mm x 1100mm) contains a small laser discharge unit (182mm x 156mm x 584mm), and no amplifier because the oscillator is highly efficient in spite of the narrow line emission. Maintenance is much easier in the clean room environment. Users can replace the discharge unit as easily as they would change Hg-lamp, only taking twenty minutes, and while they clean the window and check the electrodes of the removed unit, the laser can be operated with the easily installed replacement -already passivated discharge unit. The laser head unit is separated from a gas circulating unit and trigger pulse circuit - vibration, heat, EMI noise and particle generation. Therefore, it can be installed even in the thermal clean chamber of a stepper. The N.A. (numerical aperture) of the monochromatic lens is 0.36 and the field size is 15mm x 15mm. In fact, three kinds of lenses with N.A.s of 0.4, 0.35 and 0.3 respectively, were designed and individually evaluated for their OTF's and defocus's dependence on the light source's spectral width, and also their co-relationship. In parallel, simulations on the relationship between each lens' chromatic aberration and laser spectral width were completed and

  12. Photolysis of Pure Solid O3 and O2 Films at 193nm

    NASA Technical Reports Server (NTRS)

    Raut, U.; Loeffler, M. J.; Fama, M.; Baragiola, R. A.

    2011-01-01

    We studied quantitatively the photochemistry of solid O3 and O2 films at 193 nm and 22 K with infrared spectroscopy and microgravimetry. Photolysis of pure ozone destroyed O3, but a small amount of ozone remained in the film at high fluence. Photolysis of pure O2 produced O3 in an amount that increased with photon fluence to a stationary level. For both O2 and O3 films, the O3:O2 ratio at large fluences is ?0.07, about two orders of magnitude larger than those obtained in gas phase photolysis. This enhancement is attributed to the increased photodissociation of O2 due to photoabsorption by O2 dimers, a process significant at solid-state densities. We obtain initial quantum yield for ozone synthesis from solid oxygen, phi (O3) = 0.24 0.06, and quantum yields for destruction of O3 and O2 in their parent solids, phi(-O3) = 1.0 0.2 and phi(-O2) = 0.36 0.1. Combined with known photoabsorption cross sections, we estimate probabilities for geminate recombination of 0.5 0.1 for O3 fragments and 0.88 0.03 for oxygen atoms from O2 dissociation. Using a single parameter kinetic model, we deduce the ratio of reaction cross sections for an O atom with O2 vs. O3 to be 0.1 0.2. The general good agreement of the model with the data suggests the validity of the central assumption of efficient energy and spin relaxation of photofragments in the solid prior to their reactions with other species.

  13. Primary and secondary processes in the 193 nm photodissociation of vinyl chloride

    SciTech Connect

    Blank, D.A.; Sun, W.; Suits, A.G.; Lee, Y.T.; North, S.W.; Hall, G.E.

    1998-04-01

    We have investigated the photodissociation of vinyl chloride (H{sub 2}CCHCl) at 193 nm using the technique of photofragment translational spectroscopy. The experiments were performed at the Chemical Dynamics Beamline at the Advanced Light Source and used vacuum ultraviolet synchrotron radiation for product photoionization. We have observed five primary dissociation channels following an initial {pi}{sup {asterisk}}{l_arrow}{pi} excitation. The majority of Cl atoms originate from an excited-state dissociation. The remaining dissociation channels are consistent with competition on the ground electronic state following internal conversion from the optically prepared state. These channels include atomic and molecular hydrogen elimination, HCl elimination, and a translationally slow Cl elimination channel. We have also identified and characterized two secondary decomposition channels: (1) the elimination of Cl from chlorovinyl radicals following the primary atomic hydrogen elimination channel, and (2) hydrogen atom elimination from vinyl radicals following the primary atomic Cl elimination. By measuring the truncation in the translational energy distribution for C{sub 2}H{sub 2}Cl products from primary atomic hydrogen elimination we deduce a barrier for the reverse reaction of Cl+acetylene of 11{plus_minus}2kcal/mol. Since Cl is known to add rapidly to acetylene with no activation barrier, we conclude that H loss primarily forms the ClCCH{sub 2} isomer, and that the observed 11 kcal/mol barrier pertains to a concerted addition/rearrangement path to form the {alpha}-chlorovinyl radical. Finally, we report low-resolution photoionization spectra for the nascent vinyl radical and HCl photoproducts, in which redshifts in the ionization onsets can be related to the internal energy content. {copyright} {ital 1998 American Institute of Physics.}

  14. New insights into the photodissociation of methyl iodide at 193 nm: stereodynamics and product branching ratios.

    PubMed

    Marggi Poullain, Sonia; González, Marta G; Samartzis, Peter C; Kitsopoulos, Theofanis N; Rubio-Lago, Luis; Bañares, Luis

    2015-11-28

    The stereodynamics of methyl iodide photodissociation after excitation at 193 nm has been studied using a combination of slice imaging and resonance enhanced multiphoton ionization (REMPI) detection of the methyl and iodine products. A weak anisotropic ring appearing in the image corresponding to vibrationally excited CH3(ν1 = 1) confirms the production of ground state I((2)P3/2) atoms at this excitation wavelength as a signature of the predissociation channel reported previously [M. G. González et al., J. Chem. Phys., 2011, 135, 021102] tentatively assigned to the coupling between the B-band (3)R1 Rydberg state and the A-band (1)Q1 repulsive state. Direct REMPI detection of ground state iodine atoms indicates that most of the I((2)P3/2) species are produced in correlation with highly internally excited methyl radicals, in excellent agreement with the recent results of Xu and Pratt [Xu et al., J. Chem. Phys., 2013, 139, 214310; Xu et al., J. Phys. Chem. A, 2015, 119, 7548]. From the comparison between the CH3(ν) second order Dixon's bipolar moments β(2)(0)(20), β(0)(0)(22), β(2)(0)(02) and β(2)(0)(22) measured in this work and those reported previously for the B-band origin and the A-band, a general picture of the CH3I photodissociation stereodynamics in terms of different effects, such as the breakdown of the unique recoil direction (URD) approximation, the non-adiabatic curve crossings and the depolarization induced by the parent molecule rotation, is drawn. PMID:26489797

  15. Photodissociation of vinyl cyanide at 193 nm: Nascent product distributions of the molecular elimination channels

    SciTech Connect

    Wilhelm, Michael J.; Nikow, Matthew; Letendre, Laura; Dai Hailung

    2009-01-28

    The photodissociation dynamics of vinyl cyanide (H{sub 2}CCHCN, acrylonitrile) and deuterated vinyl cyanide (D{sub 2}CCDCN) at 193 nm are examined using time-resolved Fourier transform infrared emission spectroscopy. Prior photofragment translational spectroscopy studies [D. A. Blank et al., J. Chem. Phys. 108, 5784 (1998)] of the dissociation have observed the presence of four main dissociation channels; two molecular and two radical in nature. However, with the exception of a<0.01 quantum yield determined for the CN radical loss channel, the branching ratios of the remaining three elimination channels were not measured. The time-resolved emission spectra, including those from the deuterated samples, revealed the presence of acetylene, hydrogen cyanide (HCN), as well as the energetically less stable isomer hydrogen isocyanide (HNC). Acetylene is found in two distinct energetic distributions, suggesting that both three- and four-centered elimination reactions are occurring significantly in the dissociation. In contrast to prior ab initio studies that have suggested the dominant nature of the three-center elimination of molecular hydrogen (H{sub 2}) and cyanovinylidene (:C=CHCN), we find this reaction channel to be of little importance as there is no evidence to support any significant presence of rovibrationally excited cyanoacetylene. Spectral modeling of the product distributions allows for the first experimental determination of the relative occurrence of the three-centered (resulting in HCN+vinylidene) versus four-centered (HNC+acetylene) elimination channels as 3.34 to 1.00, in contrast to the previously calculated value of 126:1. Rice-Ramsperger-Kassel-Marcus analysis depicts that the transition state energy of the four-centered reaction should be about 10 kcal mole{sup -1} lower than the three-centered reaction.

  16. Sample temperature profile during the excimer laser annealing of silicon nanoparticles

    NASA Astrophysics Data System (ADS)

    Caninenberg, M.; Verheyen, E.; Kiesler, D.; Stoib, B.; Brandt, M. S.; Benson, N.; Schmechel, R.

    2015-11-01

    Based on the heat diffusion equation we describe the temperature profile of a silicon nanoparticle thin film on silicon during excimer laser annealing using COMSOL Multiphysics. For this purpose system specific material parameters are determined such as the silicon nanoparticle melting point at 1683 K, the surface reflectivity at 248 nm of 20% and the nanoparticle thermal conductivity between 0.3 and 1.2 W/m K. To validate our model, the simulation results are compared to experimental data obtained by Raman spectroscopy, SEM microscopy and electrochemical capacitance-voltage measurements (ECV). The experimental data are in good agreement with our theoretical findings and support the validity of the model.

  17. Surface modification and metallization of fluorocarbon polymers by excimer laser processing

    NASA Astrophysics Data System (ADS)

    Niino, Hiroyuki; Yabe, Akira

    1993-12-01

    The surface chemical modification of poly(tetrafluoroethylene) and poly(tetrafluoroethylene- co-hexafluoropropylene) films was carried out in hydrazine gas photolyzed with ArF excimer laser irradiation. The contact angle of the modified surfaces with water changed from 130° to 30° due to the reaction with hydrazine. Nitrogen on the surface was detected with x-ray photoelectron spectroscopy, suggesting that amino groups were introduced onto the surface. In addition, on the basis of hydrophilic behavior, we succeeded in selective-area electroless plating of nickel metal on the chemically modified surface.

  18. Sub-500-nm patterning of glass by nanosecond KrF excimer laser ablation

    NASA Astrophysics Data System (ADS)

    Bekesi, J.; Meinertz, J.; Simon, P.; Ihlemann, J.

    2013-01-01

    The surface of flint glass of type F2 is patterned by nanosecond KrF excimer laser ablation. Strong UV absorption provides a comparatively low ablation threshold and precise ablation contours. By using a two-grating interferometer, periodic surface patterns with 330 nm period and 100 nm modulation depth are obtained. This method enables the fabrication of 7 mm×13 mm wide grating areas with perfectly aligned grooves without the need of high-precision sample positioning. By double exposure, crossed gratings with adjustable depths in the two orthogonal directions can be generated.

  19. Pulsed Excimer Laser Processing for Cost-Effective Solar Cells

    NASA Technical Reports Server (NTRS)

    Wong, D.

    1985-01-01

    Residual lattice damage by 5 keV ion implantation and surface flaws induced by wafer cleaning are proven to affect the V sub oc more adversely for laser annealed cells than conventional thermal diffusion. However, an alternative, molecular implantation of molecular species holds potential. The first experimental results are encouraging. The lack of a commercially available mass analyzed implantation with low energy, high fluence ions is constraining.

  20. Ablation of bone and polymethylmethacrylate by an XeCl (308 nm) excimer laser

    SciTech Connect

    Yow, L.; Nelson, J.S.; Berns, M.W.

    1989-01-01

    One of the main problems in orthopaedics is the surgical removal of hard substances, such as bone and polymethylmethacrylate (PMMA). Such materials are often very difficult to remove without mechanical trauma to the remaining tissue. This study investigated the feasibility of the ultraviolet 308 nm excimer laser in the ablation of these materials. The beam was delivered through a 1 mm-diameter fiber optic at 40 Hz with energy densities at the target surface of 20-80 J/cm2 per pulse. The goal of the study was to establish the ideal dosimetry for removing bone and PMMA with minimum trauma to the adjacent tissue. Histology revealed that the 308 nm laser effectively removed bone leaving a thermal damage zone of only 2-3 microns in the remaining tissue. Increasing the energy per pulse gave correspondingly larger and deeper cuts with increasing zones of thermal damage. The excimer laser was also effective in the ablation of PMMA, creating craters in the substrate with a thermal damage zone of 10-40 microns. The debris from both substrates was evaluated.

  1. Towards excimer-laser-based stereolithography: a rapid process to fabricate rigid biodegradable photopolymer scaffolds.

    PubMed

    Beke, S; Anjum, F; Tsushima, H; Ceseracciu, L; Chieregatti, E; Diaspro, A; Athanassiou, A; Brandi, F

    2012-11-01

    We demonstrate high-resolution photocross-linking of biodegradable poly(propylene fumarate) (PPF) and diethyl fumarate (DEF) using UV excimer laser photocuring at 308 nm. The curing depth can be tuned in a micrometre range by adjusting the total energy dose (total fluence). Young's moduli of the scaffolds are found to be a few gigapascal, high enough to support bone formation. The results presented here demonstrate that the proposed technique is an excellent tool for the fabrication of stiff and biocompatible structures on a micrometre scale with defined patterns of high resolution in all three spatial dimensions. Using UV laser photocuring at 308 nm will significantly improve the speed of rapid prototyping of biocompatible and biodegradable polymer scaffolds and enables its production in a few seconds, providing high lateral and horizontal resolution. This short timescale is indeed a tremendous asset that will enable a more efficient translation of technology to clinical applications. Preliminary cell tests proved that PPF : DEF scaffolds produced by excimer laser photocuring are biocompatible and, therefore, are promising candidates to be applied in tissue engineering and regenerative medicine. PMID:22696484

  2. Photo-triggering and secondary electron produced ionization in electric discharge ArF* excimer lasers

    NASA Astrophysics Data System (ADS)

    Xiong, Zhongmin; Kushner, Mark J.

    2011-10-01

    Electric discharge excimer lasers are sustained in multi-atmosphere attaching gas mixtures that are typically preionized to enable a reproducible, uniform glow, which maximizes optical quality and gain. This preionization is often accomplished using UV light produced by a corona discharge within the plasma cavity. To quantify the relationship between corona discharge properties and those of the laser discharge, the triggering of electron avalanche by preionizing UV light in an electric discharge-pumped ArF* excimer laser was numerically investigated using a two-dimensional model. The preionizing UV fluxes were generated by a corona-bar discharge driven by the same voltage pulse as the main discharge sustained in a multi-atmospheric Ne/Ar/Xe/F2 gas mixture. The resulting peak photo-electron density in the inter-electrode spacing is around 108 cm-3, and its distribution is biased toward the UV source. The preionization density increases with increasing dielectric constant and capacitance of the corona bar. The symmetry and uniformity of the discharge are, however, improved significantly once the main avalanche develops. In addition to bulk electron impact ionization, the ionization generated by sheath accelerated secondary electrons was found to be important in sustaining the discharge current at experimentally observed values. At peak current, the magnitude of the ionization by sheath accelerated electrons is comparable to that from bulk electron impact in the vicinity of the cathode.

  3. Formation of nickel silicides by excimer laser CVD of Ni(CO)4

    NASA Astrophysics Data System (ADS)

    Borsella, E.; Kompa, Karl L.; Reiner, H.; Schroeder, Hartmut

    1990-08-01

    Nickel silicides have been grown on single crystal silicon sub- strates. A XeCl excimer laser was used for all process steps: substrate cleaning, nickel deposition , silicide formation and annealing. The nickel films were grown by photodecoxnposition of Ni(CO)4 adsorbate layers with an excess of CO to prevent homogeneous nucleation and hence the formation of dust. The samples were analysed by X-ray fluorescence, SIMS and RBS. The results indicate that epitaxial silicide layers with a thickness of 50 ma can be obtained after careful choice of laser fluence and Ni film thickness. In an alternative approach we used a molecular beam of Ni(CO)4, part of which is laser excited prior to impinging on the substrate. This allows the combination of CVD and conventional MBE techniques. In this experiment we also investigate the interaction of photofragments with substrate surfaces and other processes responsible for material deposition.

  4. Tribology and hardness of excimer-laser-processed titanium layers on cubic zirconia

    SciTech Connect

    Zaleski, M.A.; Jervis, T.R. . Dept. of Materials Science and Engineering Los Alamos National Lab., NM ); Mayer, J.W. . Dept. of Materials Science and Engineering)

    1993-02-01

    The authors have examined the wear and friction and surface hardness of excimer-laser-processed Ti layers on cubic zirconia substrates. The film exhibits a complex array of cracking following processing that is related to the crystallographic orientation of the substrate. The friction between the laser-processed layers and both steel and ruby pins is reduced by approximately one-third relative to that of untreated zirconia. In the untreated case, wear is characterized by pin wear and debris, whereas the laser-processed layer wears by film transfer to the pin. The surface hardness of the processed layer is lower than that of both the untreated zirconia and the deposited Ti film. Indentation tests indicate that the surface is brittle following processing.

  5. Excimer laser channel creation in polyethersulfone hollow fibers for compartmentalized in vitro neuronal cell culture scaffolds.

    PubMed

    Brayfield, Candace A; Marra, Kacey G; Leonard, John P; Tracy Cui, X; Gerlach, Jörg C

    2008-03-01

    Hollow fiber scaffolds that compartmentalize axonal processes from their cell bodies can enable neuronal cultures with directed neurite outgrowth within a three-dimensional (3-D) space for controlling neuronal cell networking in vitro. Controllable 3-D neuronal networks in vitro could provide tools for studying neurobiological events. In order to create such a scaffold, polyethersulfone (PES) microporous hollow fibers were ablated with a KrF excimer laser to generate specifically designed channels for directing neurite outgrowth into the luminal compartments of the fibers. Excimer laser modification is demonstrated as a reproducible method to generate 5microm diameter channels within PES hollow fiber walls that allow compartmentalization of neuronal cell bodies from their axons. Laser modification of counterpart flat sheet PES membranes with peak surface fluences of 1.2Jcm(-2) results in increased hydrophobicity and laminin adsorption on the surface compared with the unmodified PES surface. This is correlated to enhanced PC12 cell adhesion with increasing fluence onto laser-modified PES membrane surfaces coated with laminin when compared with unmodified surfaces. Adult rat neural progenitor cells differentiated on PES fibers with laser-created channels resulted in spontaneous cell process growth into the channels of the scaffold wall while preventing entrance of cell bodies. Therefore, laser-modified PES fibers serve as scaffolds with channels conducive to directing neuronal cell process growth. These hollow fiber scaffolds can potentially be used in combination with perfusion and oxygenation hollow fiber membrane sets to construct a hollow fiber-based 3-D bioreactor for controlling and studying in vitro neuronal networking in three dimensions between compartmentalized cultures. PMID:18060849

  6. Laser Machining For Fabrication Of Hohlraums And Capsules

    SciTech Connect

    Shirk, M D; Kelly, B T; Haynes, S M; Stuart, B C; Sanchez, J J; Moody, J D; Cook, R C

    2005-06-24

    Laser machining technology has been used to demonstrate the ability to rapidly perform jobs on all aspects of ICF targets. Lasers are able to rapidly perform modifications and repairs to the gold metal parts on hohlraums, make cuts in the delicate polymer parts of the hohlraum, and drill holes in the capsules to enable them to be filled with fuel. Lasers investigated in this work include 193 nm ArF and 248 nm KrF excimers and 810 nm chirped-pulse amplification Ti:Sapphire lasers. The excimer lasers showed a definite advantage in drilling and machining of polymeric materials and the ultrashort infrared pulses of the Ti:Sapphire laser were far better for the gold structures.

  7. Competing C-Br and O-NO Photofission upon Excitation of BrCH2CH2ONO at 193 nm.

    PubMed

    Wang, Lei; Scrape, Preston G; Roberts, Trevor D; Joshi, Prakriti P; Butler, Laurie J

    2015-12-17

    This study characterizes two of the primary photodissociation channels of 2-bromoethyl nitrite, BrCH2CH2ONO, at 193 nm and the subsequent unimolecular dissociation channels of the nascent vibrationally excited BrCH2CH2O radicals produced from the O-NO bond photofission. We use a crossed laser-molecular beam scattering apparatus with electron bombardment detection. Upon photodissociation of BrCH2CH2ONO at 193 nm, the measured branching ratio between primary O-NO photofission and C-Br photofission is 3.9:1 (O-NO/C-Br). The measured O-NO photofission recoil kinetic energy distribution (P(ET)) peaks near 30 kcal/mol and extends from 20 to 50 kcal/mol. We use the O-NO photofission P(ET) to characterize the internal energy distribution in the nascent ground-electronic-state BrCH2CH2O radicals. At 193 nm, all of the BrCH2CH2O radicals are formed with enough internal energy to unimolecularly dissociate to CH2Br + H2CO or to BrCH2CHO + H. We also investigated the possibility of the BrCH2CH2O → CH2CHO + HBr reaction arising from the vibrationally excited BrCH2CH2O radicals produced from O-NO primary photodissociation. Signal strengths at HBr(+), however, demonstrate that the vinoxy product does not have HBr as a cofragment, so the BrCH2CH2O → HBr + vinoxy channel is negligible compared to the CH2Br + H2CO channel. We also report our computational prediction of the unimolecular dissociation channels of the vibrational excited CH2CH2ONO radical resulting from C-Br bond photofission. Our theoretical calculations on the ground-state CH2CH2ONO potential energy surface at the G4//B3LYP/6-311++G(3df,2p) level of theory give the energetics of the zero-point corrected minima and transition states. The lowest accessible barrier height for the unimolecular dissociation of CH2CH2ONO is a 12.7 kcal/mol barrier from the cis-ONO conformer, yielding NO2 + ethene. Our measured internal energy distribution of the nascent CH2CH2ONO radicals together with this computational result suggests

  8. Characterization of excimer laser ablation generated pepsin particles using multi-wavelength photoacoustic instrument

    NASA Astrophysics Data System (ADS)

    Hopp, B.; Kecskeméti, G.; Smausz, T.; Ajtai, T.; Filep, A.; Utry, N.; Kohut, A.; Bozóki, Z.; Szabó, G.

    2012-05-01

    Preparation of organic thin layers on various special substrates using the pulsed laser deposition (PLD) technique is an important task from the point of view of bioengineering and biosensor technologies. Earlier studies demonstrated that particle ejection starts during the ablating laser pulse resulting in significant shielding effects which can influence the real fluence on the target surface and consequently the efficiency of layer preparation. In this study, we introduce a photoacoustic absorption measurement technique for in-situ characterization of ablated particles during PLD experiments. A KrF excimer laser beam ( λ=248 nm, FWHM=18 ns) was focused onto pepsin targets in a PLD chamber; the applied laser fluences were 440 and 660 mJ/cm2. We determined the wavelength dependence of optical absorption and mass specific absorption coefficient of laser ablation generated pepsin aerosols in the UV-VIS-NIR range. On the basis of our measurements, we calculated the absorbance at the ablating laser wavelength, too. We demonstrated that when the laser ablation generated pepsin aerosols spread through the whole PLD chamber the effect of absorptivity is negligible for the subsequent pulses. However, the interaction of the laser pulse and the just formed particle cloud generated by the same pulse is more significant.

  9. Raman scattering measurements in flames using a tunable KrF excimer laser.

    PubMed

    Wehrmeyer, J A; Cheng, T S; Pitz, R W

    1992-04-01

    Using a narrow-band tunable KrF excimer laser as a spontaneous vibrational Raman scattering source, we demonstrate that single-pulse concentration and temperature measurements, with only minimal fluorescence interference, are possible for all major species (O(2), N(2), H(2)O, and H(2)) at all stoichiometries (fuel-lean to fuel-rich) of H(2)-air flames. Photon-statistics-limited precisions in these instantaneous and spatially resolved single-pulse measurements are typically 5%, which are based on the relative standard deviations of single-pulse probability distributions. Optimal tuning of the narrow-band KrF excimer laser (248.623 nm) for the minimization of OH A(2)Sigma-X(2)II and O(2)B(3)Sigma(u)(-)-X(3)Sigma(g)(-) fluorescence interference is determined from fluorescence excitation spectra. In addition to the single-pulse N(2) Stokes/anti-Stokes ratio temperature measurement technique, a time-averaged temperature measurement technique ispresented that matches the N(2) Stokes Raman spectrum to theoretical spectra by using a single intermediate sta frequency to account for near-resonance enhancement. Raman flame spectra in CH(4)-air flames are presented that have good signal-to-noise characteristics and show promise for single-pulse UV Raman measurements in hydrocarbon flames. PMID:20720783

  10. Percutaneous peripheral excimer laser angioplasty: immediate success rate and short-term outcome

    NASA Astrophysics Data System (ADS)

    Visona, Adriana; Liessi, Guido; Bonanome, Andrea; Lusiani, Luigi; Miserocchi, Luigi; Pagnan, Antonio

    1991-05-01

    Excimer Laser Angioplasty was attempted in 47 patients (36 males, 11 females, mean age 62+/- 7 years, range 39-77 years), affected by peripheral vascular disease. Thirty-seven patients had a total occlusion of the superficial femoral artery, 3 of the iliac artery and 1 of the popliteal artery; 6 patients showed a subocclusive stenosis of the superficial femoral artery. Occlusions and subocclusive stenoses were classified by length: < 10 cm (28 cases), > 10 cm (19 cases). A commercial excimer laser (Technolas Max-10) was used at the Xenon- Chloride wavelength of 308 nm. The laser operated at 60 ns pulse length and at 20-40 Hz repetition rate. Applied energy fluence was 20 mJ/pulse. The energy was delivered through a multifiber catheter, which combines 12 (7F) or 18 (9F) fibers (260 micron diameter each), concentrically arranged. Balloon dilatation was associated to complete the procedure in 38 cases. The treated arteries were successfully recanalized in 41 out of 47 patients (87%). Hemodynamic improvement was confirmed by a significant increase of ankle/brachial systolic pressure index (from 0.60+/- 0.17 to 0.79+/- 0.20, p < 0.005). Failure to recanalize arterial occlusion occurred in 6 cases, and was due to dissection in 3 patients and inability to cross the final segment of a long occlusion in 3 patients. The success rate was higher for lesions < 10 cm in length. Early reocclusion was observed in 7 patients and was associated with poor run-off. The cumulative patency rate at 1 month was 90.7%. Preliminary results are encouraging. More suitable catheters and better selection of patients should improve the efficacy of laser angioplasty and should allow to perform laser procedures without combining balloon angioplasty.

  11. The investigation of selective pre-pattern free self-assembled Ge nano-dot formed by excimer laser annealing

    PubMed Central

    2012-01-01

    Localized Ge nano-dot formation by laser treatment was investigated and discussed in terms of strain distribution. The advantage of this technique is patterning localization of nano-dots without selective epitaxial growth, reducing costs and improving throughput. Self-assembled Ge nano-dots produced by excimer laser annealing statistically distributed dot density and size dependent on laser energy. Improvement in the crystallization quality of the dots was also studied, and a strain analysis was undertaken. PMID:22709630

  12. THE FIRST LASING OF 193 NM SASE, 4TH HARMONIC HGHG AND ESASE AT THE NSLS SDL.

    SciTech Connect

    WANG, X.J.; SHEN Y.; WATANABE, T.; MURPHY, J.B.; ROSE, J.; TSANG, T.

    2006-08-28

    The first lasing of three types of single-pass high-gain FELs, SASE at 193 nm, 4th harmonic HGHG at 199 nm and ESASE at the Source Development Lab (SDL) of Brookhaven National Laboratory (BNL) is reported. The saturation of 4th harmonic HGHG and ESASE FELs was observed. We also observed the spectral broadening and instability of the 4th harmonic HGHG.

  13. Photo-fragmentation of selenium powder by Excimer laser ablation in liquids

    NASA Astrophysics Data System (ADS)

    Van Overschelde, O.; Guisbiers, G.

    2015-10-01

    Laser ablation in liquids is especially adapted to produce nanoparticles free of any contamination as suited for biological and medical applications. A KrF Excimer laser delivering an UV light at 248 nm and operating at low fluence (F~0.5 J/cm2) was used to irradiate a micro-sized powder of selenium dispersed into a de-ionized water solution. To avoid any agglomeration of the selenium nanoparticles during the irradiation, surfactants (SDS and CTAB) were added to the solution and their efficiency was compared. The concentration of surfactants had to be chosen around the critical micellar concentration to produce small selenium nanoparticles (<60 nm). Moreover, SDS shows better mono-disperse size distribution compared to CTAB. Finally, photo-fragmentation is found to be more efficient than bulk thermal ablation to produce very small selenium nanoparticles (less than 10 nm).

  14. Blue satellites of absorption spectrum study of sodium based excimer-pumped alkali vapor laser

    NASA Astrophysics Data System (ADS)

    Hu, Shu; Gai, Baodong; Guo, Jingwei; Tan, Yannan; Liu, Jinbo; Li, Hui; Cai, Xianglong; Shi, Zhe; Liu, Wanfa; Jin, Yuqi; Sang, Fengting

    2015-02-01

    Sodium based excimer-pump alkali laser (Na-XPAL) is expected to be an efficient method to generate sodium beacon light, but the information about the spectroscopic characters of Na-XPAL remains sparse so far. In this work, we utilized the relative fluorescence intensity to study the absorption spectrum of blue satellites of complexes of sodium with different collision partners. The yellow fluorescence of Na D1 and D2 line was clearly visible. After processing the fluorescence intensity and the input pumping laser relative intensity, we obtained the Na-CH4 system's blue satellites was from 553nm to 556nm. Meanwhile, we experimentally demonstrated the Na-Ar and Na-Xe system's wavelength range of blue satellites. Also, it was observed that the Na-Xe system's absorption was stronger than the other two systems.

  15. Automated generation of NC part programs for excimer laser ablation micromachining from known 3D surfaces

    NASA Astrophysics Data System (ADS)

    Mutapcic, Emir; Iovenitti, Pio G.; Hayes, Jason P.

    2002-11-01

    The purpose of this research project is to improve the capability of the laser micromachinning process, so that any desired 3D surface can be produced by taking the 3D information from a CAD system and automatically generating the NC part programs. In addition, surface quality should be able to be controlled by specifying optimised parameters. This paper presents the algorithms and a software system, which processes 3D geometry in an STL file format from a CAD system and produces the NC part program to mill the surface using the Excimer laser ablation process. Simple structures are used to demonstrate the prototype system's part programming capabilities, and an actual surface is machined.

  16. Time-resolved spectroscopy and fluorescence resonance energy transfer in the study of excimer laser damage of chromatin

    NASA Astrophysics Data System (ADS)

    Radu, L.; Mihailescu, I.; Radu, S.; Gazdaru, D.

    2007-09-01

    The analysis of chromatin damage produced by a 248 nm excimer laser radiation, for doses of 0.3-3 MJ/m 2 was carried out by time-resolved spectroscopy and fluorescence resonance energy transfer (FRET). The chromatin was extracted from a normal and a tumoral tissue of Wistar rats. The decrease with laser dose of the relative contribution of the excited state lifetimes of ethidium bromide (EtBr) bounded to chromatin constitutes an evidence of the reduction of chromatin deoxyribonucleic acid (DNA) double-strand structure. FRET was performed from dansyl chloride to acridine orange, both coupled to chromatin. The increase of the average distance between these ligands, under the action of laser radiation, reflects a loosening of the chromatin structure. The radiosensitivity of tumor tissue chromatin is higher than that of a normal tissue. The determination of the chromatin structure modification in an excimer laser field can be of interest in laser therapy.

  17. Pure, single crystal Ge nanodots formed using a sandwich structure via pulsed UV excimer laser annealing.

    PubMed

    Liao, Ting-Wei; Chen, Hung-Ming; Shen, Kuan-Yuan; Kuan, Chieh-Hsiung

    2015-04-24

    In this paper, a sandwich structure comprising a SiO2 capping layer, amorphous Germanium (a-Ge) nanodots (NDs), and a pit-patterned Silicon (Si) substrate is developed, which is then annealed by utilizing a pulsed ultraviolet excimer laser in order to fabricate an array of pure, single crystal Ge NDs at room temperature. A wide bandgap SiO2 capping layer is used as a transparent thermally isolated layer to prevent thermal loss and Si-Ge intermixing. The two-dimensional pit-patterned Si substrate is designed to confine the absorbed laser energy, reduce the melting point, and block the surface migration of the Ge. After optimizing the laser radiation parameters such that the laser energy density is 200 mJ cm(-2), the laser annealing period is 10 s, and the number of laser shots is 10, pure, single crystal Ge NDs that have both a regular arrangement and a uniform size distribution are obtained in the pits of the Si substrates. The Raman spectrum shows a highly symmetric Ge transversal optical peak with a full width at half maximum of 4.2 cm(-1) at 300.7 cm(-1), which is close to that of the original Ge wafer. In addition, the high-resolution transmission electron microscopy image for the Ge NDs and the corresponding selected area electron diffraction pattern shows a clear single crystalline structure without any impurities. PMID:25815515

  18. Pure, single crystal Ge nanodots formed using a sandwich structure via pulsed UV excimer laser annealing

    NASA Astrophysics Data System (ADS)

    Liao, Ting-Wei; Chen, Hung-Ming; Shen, Kuan-Yuan; Kuan, Chieh-Hsiung

    2015-04-01

    In this paper, a sandwich structure comprising a SiO2 capping layer, amorphous Germanium (a-Ge) nanodots (NDs), and a pit-patterned Silicon (Si) substrate is developed, which is then annealed by utilizing a pulsed ultraviolet excimer laser in order to fabricate an array of pure, single crystal Ge NDs at room temperature. A wide bandgap SiO2 capping layer is used as a transparent thermally isolated layer to prevent thermal loss and Si-Ge intermixing. The two-dimensional pit-patterned Si substrate is designed to confine the absorbed laser energy, reduce the melting point, and block the surface migration of the Ge. After optimizing the laser radiation parameters such that the laser energy density is 200 mJ cm-2, the laser annealing period is 10 s, and the number of laser shots is 10, pure, single crystal Ge NDs that have both a regular arrangement and a uniform size distribution are obtained in the pits of the Si substrates. The Raman spectrum shows a highly symmetric Ge transversal optical peak with a full width at half maximum of 4.2 cm-1 at 300.7 cm-1, which is close to that of the original Ge wafer. In addition, the high-resolution transmission electron microscopy image for the Ge NDs and the corresponding selected area electron diffraction pattern shows a clear single crystalline structure without any impurities.

  19. Glare sensitivity and visual acuity after excimer laser photorefractive keratectomy for myopia

    PubMed Central

    Niesen, U.; Businger, U.; Hartmann, P.; Senn, P.; Schipper, I.

    1997-01-01

    BACKGROUND—Following excimer laser photorefractive keratectomy (PRK), an increase in glare sensitivity and a reduction in contrast sensitivity can occur owing to changes in the cornea (structure and topography). In this study, an attempt was made to quantify and document objectively a change in those subjective perceptual factors.
METHODS—Snellen visual acuity and disability glare were measured with the Berkeley glare test preoperatively as well as 1, 3, 6, 9, and 12 months postoperatively, after excimer laser photorefractive keratectomy (PRK) on 32 myopic patients (46 eyes). During the postoperative progress checks, haze was graded and contrast sensitivity was measured with the Vistech chart. All the data were statistically analysed by multiple regression.
RESULTS—One year after PRK, a reduction in visual acuity (VA) measured with the low acuity contrast chart (10%) with and without glare could still be found, despite the fact that acuity measurements with a high contrast Snellen chart showed the same VA 6 months postoperatively as well as before the treatment. The lowest VA could be measured 1 month postoperatively; thereafter, the acuity increased despite the increase in haze that occurred during the first 3 months.
CONCLUSION—Disability glare and a reduction in contrast sensitivity could be observed in most patients after PRK treatment with the Meditec laser system with its scanning slit. The future will show if new technology and a broader flattening area of 6 to 7 mm can minimise these postoperative complications.

 PMID:9059248

  20. Self-control study of combination treatment of 308 nm excimer laser and calcipotriene ointment on stable psoriasis vulgaris

    PubMed Central

    Tang, Ya-Juan; Xu, Wan-Wen; Liu, Xiao-Ming; Zhang, Ru-Zhi; Xu, Chun-Xing; Xu, Bin; Cheng, Sai; Liu, Qi

    2014-01-01

    Objective: This study aims to compare the differences of clinical efficacy and safety of treatment of stable psoriasis vulgaris with calcipotriene ointment in combination with 308 nm excimer laser to 308 nm excimer laser alone. Methods: Randomized, open and self-control trial was conducted in 36 selected patients. The skin lesions from these patients with stable psoriasis vulgaris were divided into two sides along the midline of torso, one side was treated with 308 nm excimer laser, 2 times/week, at meantime Calcipotriene was applied externally, 2 times/day (treatment group); the other side was given 308 nm excimer laser alone, 2 times/week, the treatment period was 6 weeks (control group). Skin lesion area, PASI scores and cumulative doses of 308 nm excimer laser in patients with psoriasis were assessed before treatment and on weeks 2, 4 and 6 after treatment. Results: 32 of 36 patients with stable psoriasis vulgaris completed study, effective rates in two groups were better on week 6 (84.37%, 56.25%) than on week 4 (53.12%, 37.5%) and on week 2 (31.25%, 18.75%) (P < 0.05). Effective rate on week 6 in control group (56.25%) was lower than treatment group (84.37%) (P < 0.05). The two groups showed that PASI scores on weeks 2 and 4 after treatment were significantly lower than before treatments (P < 0.05), and PASI scores on week 6 in treatment group was significantly lower than control group (P < 0.05). The average cumulative laser doses in treatment group at the end of trial was 4.69 (2.03) J/cm2, which was significantly lower than in control group 8.41 (2.42) J/cm (P < 0.05). Treatment efficacies in the head, folds, back, abdomen and limbs were similar and no serious adverse effects, however the number of treatment and irradiation doses in the head and folds were significantly less than in back, abdomen and limbs (P < 0.05). Conclusions: Treatment of psoriasis vulgaris with 308 nm excimer laser in combination with external application of Calcipotriene ointment

  1. Excimer laser crystallization of amorphous silicon carbide produced by ion implantation

    NASA Astrophysics Data System (ADS)

    Hedler, A.; Urban, S.; Falk, F.; Hobert, H.; Wesch, W.

    2003-01-01

    4H-SiC was implanted with 100-250 keV Ge + and Xe + ions and doses of 1×10 14 to 1×10 16 cm -2 at room temperature in order to produce 40-200 nm thick amorphous surface layers. The samples were irradiated with 1-50,000 pulses of a KrF excimer laser (248 nm wavelength, 30 ns pulse duration) using fluences of 150-900 mJ/cm 2 to investigate the crystallization process as a function of the laser parameters. Crystallization as well as redistribution of the impurity atoms were analyzed by Rutherford backscattering spectrometry and infrared reflection measurements. Phase transitions occurring during the irradiation were studied by means of time-resolved reflectivity measurements. In order to explain the observed phase transitions numerical analysis was performed by solving the inhomogeneous heat flow equation using the parameters of the corresponding phases. In this work, we give a consistent description of the experimental results by the numerical simulations for the given laser setup. Depending on the amorphous layer thickness, melting, solidification, and crystallization of the amorphous phase can be effectively controlled by both the laser fluence and the number of laser pulses.

  2. High-performance thin-film transistors fabricated using excimer laser processing and grain engineering

    SciTech Connect

    Giust, G.K.; Sigmon, T.W.

    1998-04-01

    High-performance polysilicon thin-film transistors (TFT`s) are fabricated using an excimer laser to recrystallize the undoped channel and dope the source-drain regions. Using a technique the authors call grain engineering they are able to control grain microstructure using laser parameters. Resulting polysilicon films are obtained with average grain sizes of {approximately}4--9 {micro}m in sub-100 nm thick polysilicon films without substrate heating during the laser recrystallization process. Using a simple four-mask self-aligned aluminum top-gate structure, they fabricate TFT`s in these films. By combining the grain-engineered channel polysilicon regions with laser-doped source-drain regions, TFT`s are fabricated with electron mobilities up to 260 cm{sup 2}/Vs and on/off current ratios greater than 10{sup 7} To their knowledge, these devices represent the highest performance laser-processed TFT`s reported to date fabricated without substrate heating or hydrogenation.

  3. Effect of ambient environment on excimer laser induced micro and nano-structuring of stainless steel

    NASA Astrophysics Data System (ADS)

    Umm-i-Kalsoom; Bashir, Shazia; Ali, Nisar; Akram, Mahreen; Mahmood, Khaliq; Ahmad, Riaz

    2012-11-01

    The effect of laser fluence and an ambient environment on the formation and development of the micro and nano-structures on the laser irradiated stainless steel (AISI-304) targets have been investigated. For this purpose KrF excimer laser (λ = 248 nm, t = 20 ns, repetition rate 20 Hz) has been used. The targets are exposed for various laser fluences ranging from 0.72 J cm-2 to 1.27 J cm-2 under the vacuum condition and in the oxygen environment at a pressure of 133 mbar. Various features of treated targets, such as surface morphology, chemical composition and crystalline structure are analyzed by scanning electron microscope, energy dispersive X-ray spectroscopy and X-ray diffraction techniques, respectively. Scanning electron microscope analysis reveals the formation of laser-induced periodic surface structures (LIPSS), cavities, hillocks in both ambient environments (vacuum, oxygen). Cone-formation on the top of wave like ridges is observed under vacuum condition. In case of oxygen only redeposition is observed. Energy dispersive X-ray spectroscopy analysis exhibits that there is variation in chemical composition in both environments. When the target is treated in oxygen environment enhancement of the surface oxygen content is observed. X-ray diffraction exhibits that no new phases are formed under vacuum condition but a phase change in oxygen ambient is observed. For various fluences the variation in the peak intensity, crystallinity and d-spacing is observed under both ambient conditions.

  4. Irradiation planning for automated treatment of psoriasis with a high-power excimer laser

    NASA Astrophysics Data System (ADS)

    Klämpfl, Florian; Schmidt, Michael; Hagenah, Hinnerk; Görtler, Andreas; Wolfsgruber, Frank; Lampalzer, Ralf; Kaudewitz, Peter

    2006-02-01

    American and European statistics have shown that 1-2 per cent of the human population is affected by the skin disease psoriasis. Recent research reports promising treatment results when irradiating skin areas affected by psoriasis with high powered excimer lasers with a wavelength of 308 nm. In order to apply the necessary high energy dose without hurting healthy parts of the skin new approaches regarding the system technology must be considered. The aim of the current research project is the development of a sensor-based, automated laser treatment system for psoriasis. In this paper we present the algorithms used to cope with the diffculties of irradiating irregularly shaped areas on curved surfaces with a predefined energy level using a pulsed laser. Patients prefer the treatment to take as little time as possible. This also helps to reduce costs. Thus the distribution of laser pulses on the surface to achieve the given energy level on every point of the surface has to be calculated within a limited time frame. The remainder of the paper will describe in detail an efficient method to plan and optimize the laser pulse distribution. Towards the end, some first results will be presented.

  5. Microlens Array Fabricated by Excimer Laser Micromachining with Gray-tone Photolithography

    NASA Astrophysics Data System (ADS)

    Tien, Chung-Hao; Chien, Yeh-En; Chiu, Yi; Shieh, Han-Ping D.

    2003-03-01

    We demonstrate the fabrication of a refractive microlens array by using 248 nm excimer laser micromachining with coded gray-tone mask photolithography. With pre-corrections to the nonlinear exposure process, the maximum deviation from the designed shape was below 5%. The fabricated hemispherical lens of 30 μm radius was used as a solid immersion lens (SIL) and combined with a 0.54 numerical aperture (NA) objective to achieve a 0.87 effective NA through the knife-edge scanning test. The experimental results agreed with those of the simulation. Unlike the methods such as the thermal melting process, this one-step optical exposure method with a coded mask provides a relatively fast and cost-effective way to realize a microlens array in optical data storage, information processing, and optical interconnection applications.

  6. An electrically triggered 200 kV rail-gap switch for wide aperture excimer lasers

    NASA Astrophysics Data System (ADS)

    Endoh, A.; Watanabe, S.; Watanabe, M.

    1984-03-01

    A wide aperture (7 x 7 sq cm), high output energy (5 J in KrF and 13.8 J in XeCl), UV preionized excimer laser is described. A self-breakdown rail gap was employed as an output switch with the maximum voltage and current up to 230 kV and 300 kA, respectively. To solve the switching jitter problem associated with the self-breakdown, an electrical triggering was investigated. The measured minimum switching time delay and gap closing time were 40 and 10 ns, respectively. The number of channels up to 50 was observed with a uniform distribution over the 80-cm electrode length. The triggering jitter was measured to be less than a nanosecond. The maximum operation voltage of the triggered rail gap was 200 kV. The successful trigger operation was obtained in the range 30-98 percent of the self-breakdown voltage.

  7. The effect of excimer laser pretreatment on diffusion and activation of boron implanted in silicon

    SciTech Connect

    Monakhov, E.V.; Svensson, B.G.; Linnarsson, M.K.; La Magna, A.; Italia, M.; Privitera, V.; Fortunato, G.; Cuscuna, M.; Mariucci, L.

    2005-11-07

    We have investigated the effect of excimer laser annealing (ELA) on transient enhanced diffusion (TED) and activation of boron implanted in Si during subsequent rapid thermal annealing (RTA). It is observed that ELA with partial melting of the implanted region causes reduction of TED in the region that remains solid during ELA, where the diffusion length of boron is reduced by a factor of {approx}4 as compared to the as-implanted sample. This is attributed to several mechanisms such as liquid-state annealing of a fraction of the implantation induced defects, introduction of excess vacancies during ELA, and solid-state annealing of the defects beyond the maximum melting depth by the heat wave propagating into the Si wafer. The ELA pretreatment provides a substantially improved electrical activation of boron during subsequent RTA.

  8. Studies of Preionization Processes of High Pressure Gases for Excimer Laser Discharges

    NASA Astrophysics Data System (ADS)

    Kataoka, N.; Uchino, K.; Muraoka, K.; Okada, T.; Maeda, M.; Sunaka, E.; Enami, T.; Mizoguchi, H.

    1998-10-01

    The aim of this research is to understand and control the preionization process in high pressure discharges used for excimer lasers. For this purpose, a test chamber with a spark light source was designed and fabricated, to achieve ultra high vacuum and to control the base pressure. Photocharge signals produced by the spark light source were collected by pairs of plate electrodes placed inside the test chamber. In order to study the effect of gaseous impurities on the preionization process, measurements were performed for different base pressure conditions. The results showed that the photocharge signal was linearly correlated with the base pressure. Also, the possibility of actively controlling the preionization by adding small amount of Xe gas to the gas mixture was examined. The maximum signal at the Xe partial pressure of 0.1 Torr was 10 times higher than the signal for the Ne and Kr mixture without Xe, suggesting that active control may be possible.

  9. Interaction of 308-nm excimer laser light with temporomandibular joint related structures

    NASA Astrophysics Data System (ADS)

    Liesenhoff, Tim; Funk, Armin

    1994-02-01

    Arthroscopy of TMJ has become a clinically important and more and more accepted method for diagnosis and treatment of TMJ alteration. This minimal invasive method is clearly limited by the anatomical dimensions of the TMJ. A 308 nm excimer laserlight has already found clinical applications in angioplasty, ophthalmology, and dentistry. The aim of the presented study was to find out if it is possible to ablate TMJ related structures under arthroscopic conditions. It also aims to evaluate the energy-threshold for ablation and the maximal possible rate of ablation. Contrary to other laser systems it offers a unique combination of minimal tissue alteration, precise tissue ablation guidability through optical fibers, and a good transmission through water.

  10. Analysis of the change in peak corneal temperature during excimer laser ablation in porcine eyes

    NASA Astrophysics Data System (ADS)

    Mosquera, Samuel Arba; Verma, Shwetabh

    2015-07-01

    The objective is to characterize the impact of different ablation parameters on the thermal load during corneal refractive surgery by means of excimer laser ablation on porcine eyes. One hundred eleven ablations were performed in 105 porcine eyes. Each ablation was recorded using infrared thermography and analyzed mainly based on the two tested local frequencies (40 Hz, clinical local frequency; 1000 Hz, no local frequency). The change in peak corneal temperature was analyzed with respect to varying ablation parameters [local frequency, system repetition rate, pulse energy, optical zone (OZ) size, and refractive correction]. Transepithelial ablations were also compared to intrastromal ablations. The average of the baseline temperature across all eyes was 20.5°C±1.1 (17.7°C to 22.2°C). Average of the change in peak corneal temperature for all clinical local frequency ablations was 5.8°C±0.8 (p=3.3E-53 to baseline), whereas the average was 9.0°C±1.5 for all no local frequency ablations (p=1.8E-35 to baseline, 1.6E-16 to clinical local frequency ablations). A logarithmic relationship was observed between the changes in peak corneal temperature with increasing local frequency. For clinical local frequency, change in peak corneal temperature was comparatively flat (r2=0.68 with a range of 1.5°C) with increasing system repetition rate and increased linearly with increasing OZ size (r2=0.95 with a range of 2.4°C). Local frequency controls help maintain safe corneal temperature increase during excimer laser ablations. Transepithelial ablations induce higher thermal load compared to intrastromal ablations, indicating a need for stronger thermal controls in transepithelial refractive procedures.

  11. High Power Pulsed Gas Lasers

    NASA Astrophysics Data System (ADS)

    Witteman, W. J.

    1987-09-01

    Gas lasers have shown to be capable of delivering tens of terrawatt aspeak power or tens of kilowatt as average power. The efficiencies of most high power gas lasers are relatively high compared with other types of lasers. For instance molecular lasers, oscillating on low lying vibrational levels, and excimer lasers may have intrinsic efficiencies above 10%.The wavelengths of these gas lasers cover the range from the far infrared to the ultra-violet region, say from 12000 to 193 nm. The most important properties are the scalability, optical homogeneity of the excited medium, and the relatively low price per watt of output power. The disadvantages may be the large size of the systems and the relatively narrow line width with limited tunability compared with solid state systems producing the same peak power. High power gas lasers group into three main categories depending on the waste-heat handling capacity.

  12. Excimer versus Femtosecond Laser Assisted Penetrating Keratoplasty in Keratoconus and Fuchs Dystrophy: Intraoperative Pitfalls

    PubMed Central

    El-Husseiny, Moatasem; Seitz, Berthold; Langenbucher, Achim; Akhmedova, Elena; Szentmary, Nora; Hager, Tobias; Tsintarakis, Themistoklis; Janunts, Edgar

    2015-01-01

    Purpose. To assess the intraoperative results comparing two non-mechanical laser assisted penetrating keratoplasty approaches in keratoconus and Fuchs dystrophy. Patients and Methods. 68 patients (age 18 to 87 years) with keratoconus or Fuchs dystrophy were randomly distributed to 4 groups. 35 eyes with keratoconus and 33 eyes with Fuchs dystrophy were treated with either excimer laser ([Exc] groups I and II) or femtosecond laser-assisted ([FLAK] groups III and IV) penetrating keratoplasty. Main intraoperative outcome measures included intraoperative decentration, need for additional interrupted sutures, alignment of orientation markers, and intraocular positive pressure (vis a tergo). Results. Intraoperative recipient decentration occurred in 4 eyes of groups III/IV but in none of groups I/II. Additional interrupted sutures were not necessary in groups I/II but in 5 eyes of groups III/IV. Orientation markers were all aligned in groups I/II but were partly misaligned in 8 eyes of groups III/IV. Intraocular positive pressure grade was recognized in 12 eyes of groups I/II and in 19 eyes of groups III/IV. In particular, in group III, severe vis a tergo occurred in 8 eyes. Conclusions. Intraoperative decentration, misalignment of the donor in the recipient bed, and need for additional interrupted sutures as well as high percentage of severe intraocular positive pressure were predominantly present in the femtosecond laser in keratoconus eyes. PMID:26483974

  13. [Analysis of images in the prophylaxis and treatment of complications after kerato-refractive excimer laser surgeries].

    PubMed

    Makarov, I A

    2003-01-01

    A total of 236 eyes of patients with myopia and hypermetropia of different severity degrees after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) were observed. The densitometry and planimetry analysis of corneal images, obtained through storing them in the computer memory, was used to evaluate postoperatively the corneal condition. Planimetry was used to forecast the time of epithelization and to assess the efficiency of drug therapy. The optic density was found to increase, after excimer-laser surgeries, in all patients and it depended on a type of refraction and its degree. The optic-density dynamics of corneal images also depended on a degree and type of refraction as well as on a type of drug therapy. Hence, densitometry and planimetry, as objective methods used to follow up the patients after keratorefractive excimer-laser surgeries, make it possible to diagnose early enough the presence of complications related with disorders in transparency and healing of the cornea. PMID:12698885

  14. Statistical Examination of the a and a + 1 Fragment Ions from 193 nm Ultraviolet Photodissociation Reveals Local Hydrogen Bonding Interactions

    NASA Astrophysics Data System (ADS)

    Morrison, Lindsay J.; Rosenberg, Jake A.; Singleton, Jonathan P.; Brodbelt, Jennifer S.

    2016-05-01

    Dissociation of proteins and peptides by 193 nm ultraviolet photodissociation (UVPD) has gained momentum in proteomic studies because of the diversity of backbone fragments that are produced and subsequent unrivaled sequence coverage obtained by the approach. The pathways that form the basis for the production of particular ion types are not completely understood. In this study, a statistical approach is used to probe hydrogen atom elimination from a + 1 radical ions, and different extents of elimination are found to vary as a function of the identity of the C-terminal residue of the a product ions and the presence or absence of hydrogen bonds to the cleaved residue.

  15. Statistical Examination of the a and a + 1 Fragment Ions from 193 nm Ultraviolet Photodissociation Reveals Local Hydrogen Bonding Interactions

    NASA Astrophysics Data System (ADS)

    Morrison, Lindsay J.; Rosenberg, Jake A.; Singleton, Jonathan P.; Brodbelt, Jennifer S.

    2016-09-01

    Dissociation of proteins and peptides by 193 nm ultraviolet photodissociation (UVPD) has gained momentum in proteomic studies because of the diversity of backbone fragments that are produced and subsequent unrivaled sequence coverage obtained by the approach. The pathways that form the basis for the production of particular ion types are not completely understood. In this study, a statistical approach is used to probe hydrogen atom elimination from a + 1 radical ions, and different extents of elimination are found to vary as a function of the identity of the C-terminal residue of the a product ions and the presence or absence of hydrogen bonds to the cleaved residue.

  16. Enhanced efficiency of the dye-sensitized solar cells by excimer laser irradiated carbon nanotube network counter electrode

    SciTech Connect

    Chien, Yun-San Fu, Wei-En; Yang, Po-Yu; Lee, I-Che; Chu, Chih-Chieh; Chou, Chia-Hsin; Cheng, Huang-Chung

    2014-02-03

    The carbon nanotube network decorated with Pt nanoparticles (PtCNT) irradiated by excimer laser as counter electrode (CE) of dye-sensitized solar cells (DSSCs) has been systematically demonstrated. The conversion efficiency would be improved from 7.12% to 9.28% with respect to conventional Pt-film one. It was attributed to the enhanced catalytic surface from Pt nanoparticles and the improved conductivity due to the adjoining phenomenon of PtCNTs irradiated by laser. Moreover, the laser annealing could also promote the interface contact between CE and conductive glass. Therefore, such a simple laser-irradiated PtCNT network is promising for the future flexible DSSCs applications.

  17. The Role of Crystalline Water in the Interaction of Excimer Laser Light with Brushite

    NASA Astrophysics Data System (ADS)

    Dawes, M. L.; Langford, S. C.; Dickinson, J. T.

    1998-03-01

    A number of minerals of environmental interest contain waters of hydration, sometimes called crystalline water. Hydrated crystals often show dramatic changes in optical properties as well as mechanical properties, both influencing the response of the material to radiation. From an analytic point of view, very little is known about the influence of hydration regarding laser desorption and ablation phenomena. We explore the interaction of excimer laser light (KrF 248 nm) with single crystal brushite (CaHPO_4.2H_2O), a model biomineral phosphate containing H_2O. We first show that defects dominate the interactions as revealed by high sensitivity detection of Ca^+ at low fluences and that this ion emission predicts ablation thresholds. The most probable ion energy, which occurs at 11 eV, is much higher than the incident photon energy of 5 eV. The ion intensities also display a highly nonlinear fluence dependence, typically 6-8th order, entirely consistent with ion emission models we have recently presented. We show that laser coupling can be enhanced several orders of magnitude by generation of defects, i.e., by mechanical treatment, heating, or exposure to electron beams and that the consequences of crystalline H_2O and HPO_4^2- decomposition play major and related roles in this defect production.

  18. Photodissociation dynamics of the methyl perthiyl radical at 248 and 193 nm using fast-beam photofragment translational spectroscopy

    NASA Astrophysics Data System (ADS)

    Harrison, Aaron W.; Ryazanov, Mikhail; Sullivan, Erin N.; Neumark, Daniel M.

    2016-07-01

    The photodissociation dynamics of the methyl perthiyl radical (CH3SS) have been investigated using fast-beam coincidence translational spectroscopy. Methyl perthiyl radicals were produced by photodetachment of the CH3SS- anion followed by photodissociation at 248 nm (5.0 eV) and 193 nm (6.4 eV). Photofragment mass distributions and translational energy distributions were measured at each dissociation wavelength. Experimental results show S atom loss as the dominant (96%) dissociation channel at 248 nm with a near parallel, anisotropic angular distribution and translational energy peaking near the maximal energy available to ground state CH3S and S fragments, indicating that the dissociation occurs along a repulsive excited state. At 193 nm, S atom loss remains the major fragmentation channel, although S2 loss becomes more competitive and constitutes 32% of the fragmentation. The translational energy distributions for both channels are very broad at this wavelength, suggesting the formation of the S2 and S atom products in several excited electronic states.

  19. A study on effect of point-of-use filters on defect reduction for advanced 193nm processes

    NASA Astrophysics Data System (ADS)

    Vitorino, Nelson; Wolfer, Elizabeth; Cao, Yi; Lee, DongKwan; Wu, Aiwen

    2009-03-01

    Bottom Anti-Reflective Coatings (BARCs) have been widely used in the lithography process for decades. BARCs play important roles in controlling reflections and therefore improving swing ratios, CD variations, reflective notching, and standing waves. The implementation of BARC processes in 193nm dry and immersion lithography has been accompanied by defect reduction challenges on fine patterns. Point-of-Use filters are well known among the most critical components on a track tool ensuring low wafer defects by providing particle-free coatings on wafers. The filters must have very good particle retention to remove defect-causing particulate and gels while not altering the delicate chemical formulation of photochemical materials. This paper describes a comparative study of the efficiency and performance of various Point-of-Use filters in reducing defects observed in BARC materials. Multiple filter types with a variety of pore sizes, membrane materials, and filter designs were installed on an Entegris Intelligent(R) Mini dispense pump which is integrated in the coating module of a clean track. An AZ(R) 193nm organic BARC material was spin-coated on wafers through various filter media. Lithographic performance of filtered BARCs was examined and wafer defect analysis was performed. By this study, the effect of filter properties on BARC process related defects can be learned and optimum filter media and design can be selected for BARC material to yield the lowest defects on a coated wafer.

  20. UV excimer laser and low temperature plasma treatments of polyamide materials

    NASA Astrophysics Data System (ADS)

    Yip, Yiu Wan Joanne

    Polyamides have found widespread application in various industrial sectors, for example, they are used in apparel, home furnishings and similar uses. However, the requirements for high quality performance products are continually increasing and these promote a variety of surface treatments for polymer modification. UV excimer laser and low temperature plasma treatments are ideally suited for polyamide modification because they can change the physical and chemical properties of the material without affecting its bulk features. This project aimed to study the modification of polyamides by UV excimer laser irradiation and low temperature plasma treatment. The morphological changes in the resulting samples were analysed by scanning electron microscopy (SEM) and tapping mode atomic force microscopy (TM-AFM). The chemical modifications were studied by x-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and chemical force microscopy (CFM). Change in degree of crystallinity was examined by differential scanning calorimetry (DSC). After high-fluence laser irradiation, topographical results showed that ripples of micrometer size form on the fibre surface. By contrast, sub-micrometer size structures form on the polyamide surface when the applied laser energy is well below its ablation threshold. After high-fluence laser irradiation, chemical studies showed that the surface oxygen content of polyamide is reduced. A reverse result is obtained with low-fluence treatment. The DSC result showed no significant change in degree of crystallinity in either high-fluence or low-fluence treated samples. The same modifications in polyamide surfaces were studied after low temperature plasma treatment with oxygen, argon or tetrafluoromethane gas. The most significant result was that the surface oxygen content of polyamide increased after oxygen and argon plasma treatments. Both treatments induced many hydroxyl (-OH) and carboxylic acid (-COOH

  1. The effect on the ultrastructure of dental enamel of excimer-dye, argon-ion and CO2 lasers.

    PubMed

    Palamara, J; Phakey, P P; Orams, H J; Rachinger, W A

    1992-12-01

    This study aimed to investigate the ultrastructural changes that occur in dental enamel irradiated with pulsed excimer-dye, continuous-wave (CW) argon-ion and CW CO2 lasers. The pulsed excimer-dye laser produced deep craters, rough damaged surfaces with underlying porosity and amorphous vitrified material. The vitrification of the enamel indicated that the temperature in these areas must have been at least in the range 1280 to 1600 degrees C. The CW argon-ion laser irradiation produced a changed non-cratered surface with inter-crystalline porosity and a mixture of small and some large irregularly packed recrystallized enamel crystals. The CW CO2 laser produced shallow craters, surface crazing and lifting off the removal of the surface layer to expose the underlying roughened enamel. The ultrastructure revealed inter- and intra-crystalline porosity, a mixture of small but variable size irregularly packed recrystallized enamel crystals and also well packed large crystals which indicated further grain growth. The porosity in lased enamel was overall very similar to that seen in enamel heated in an electric furnace to a temperature of 600 degrees C. The presence of recrystallized enamel crystals indicated a temperature rise of approximately 1000 degrees C and the grain growth indicated that a temperature > or = 1000 degrees C existed for some time after the laser irradiation. In general the excimer-dye laser produced most surface destruction because of its higher power density and shorter interaction time and the argon-ion laser produced least damage. These results indicated that the lasers used in this study require much more refinement before they can find therapeutic application to dental enamel, and this may well be the case for other lasers being investigated for clinical dental practise. PMID:1295076

  2. CAD/CAM interface design of excimer laser micro-processing system

    NASA Astrophysics Data System (ADS)

    Jing, Liang; Chen, Tao; Zuo, Tiechuan

    2005-12-01

    Recently CAD/CAM technology has been gradually used in the field of laser processing. The excimer laser micro-processing system just identified G instruction before CAD/CAM interface was designed. However the course of designing a part with G instruction for users is too hard. The efficiency is low and probability of making errors is high. By secondary development technology of AutoCAD with Visual Basic, an application was developed to pick-up each entity's information in graph and convert them to each entity's processing parameters. Also an additional function was added into former controlling software to identify these processing parameters of each entity and realize continue processing of graphic. Based on the above CAD/CAM interface, Users can design a part in AutoCAD instead of using G instruction. The period of designing a part is sharply shortened. This new way of design greatly guarantees the processing parameters of the part is right and exclusive. The processing of complex novel bio-chip has been realized by this new function.

  3. N-type doping of Ge by As implantation and excimer laser annealing

    SciTech Connect

    Milazzo, R.; Napolitani, E. De Salvador, D.; Mastromatteo, M.; Carnera, A.; Impellizzeri, G.; Boninelli, S.; Priolo, F.; Privitera, V.; Fisicaro, G.; Italia, M.; La Magna, A.; Cuscunà, M.; Fortunato, G.

    2014-02-07

    The diffusion and activation of arsenic implanted into germanium at 40 keV with maximum concentrations below and above the solid solubility (8 × 10{sup 19} cm{sup −3}) have been studied, both experimentally and theoretically, after excimer laser annealing (λ = 308 nm) in the melting regime with different laser energy densities and single or multiple pulses. Arsenic is observed to diffuse similarly for different fluences with no out-diffusion and no formation of pile-up at the maximum melt depth. The diffusion profiles have been satisfactorily simulated by assuming two diffusivity states of As in the molten Ge and a non-equilibrium segregation at the maximum melt depth. The electrical activation is partial and decreases with increasing the chemical concentration with a saturation of the active concentration at 1 × 10{sup 20} cm{sup −3}, which represents a new record for the As-doped Ge system.

  4. Adhesion strength measurements of excimer-laser-treated PTFE surfaces using liquid photoreagents

    NASA Astrophysics Data System (ADS)

    Hopp, Bela; Smausz, Tomi; Kresz, Norbert; Ignacz, Ferenc

    2003-04-01

    The most known feature of polytetrafluoroethylene (PTFE) is its adhesion behavior: it is hydrophobic and oleophobic at the same time. This can cause serious problems and obstacles during the surface treatment and fixing of PTFE objects. During our experiments Teflon films were irradiated by an ArF excimer laser beam in presence of liquid photoreagents containing amine groups (aminoethanol, 1,2-diaminoethane, triethylene-tetramine). In consequence of the treatment the adhesion of the modified surfaces significantly increased, the samples could be glued and moistened. The adhesion strength of the glued surfaces was measured in the function of the applied laser fluence. The adhesion strength increased drastically between 0 - 1 mJ/cm2 and showed saturation above 1 mJ/cm2 at approximately 5 - 9 MPa values depending on the applied photoreagents. On the basis of our experiments it was found that the treatment with triethylene-tetramine was the most effective. The surface chemical modifications of the treated Teflon samples can be due to the incorporation of amine groups into the surface layer.

  5. Surface properties modifications obtained on ceramics and metals resulting from excimer laser processing technique

    NASA Astrophysics Data System (ADS)

    Nicolas, Gines; Autric, Michel L.; Ocana, Jose L.

    1998-09-01

    The unique properties of a UV laser beam (high energy, short pulse duration) allow to transform the surface of ultrahard materials such as ceramics. In this way, a KrF excimer laser was used in this study in order to modify in selected zones, the surface of metals (aluminum alloy, titanium alloy and stainless steel) and oxides (Al2O3, ZrO2), carbide (SiC) and nitride (AlN). These ceramics possess good mechanical and thermal properties but exhibit a brittle behavior due to the granular structure. In a suitable range where the irradiated zone is melted and defects are removed, initial properties are modified (roughness, porosity, hardness, chemical composition). A cleaned and smoothed surface can be obtained without pores and cracks. These sites where corrosion attack starts are minimized and can lead to improve functions in potential industrial applications. The results presented in this work have been obtained by different analysis techniques such as scanning electron microscopy (SEM) to examine morphology, Auger spectroscopy (AES) to give chemical composition and depths profiles, mechanical tests to show roughness and hardness, grazing X-ray diffraction (XRD) to find structure.

  6. Morphological and structural effects of excimer laser treatment of amorphous silicon

    PubMed

    Loreti; della Sala D; Garozzo

    2000-06-01

    The excimer laser irradiation of thin film amorphous silicon (a-Si) precursors on glass is a suitable method for obtaining high-performance polycrystalline silicon (p-Si) active layers for devices and circuits. By changing the experimental conditions, the recrystallization method generates a variety of microstructures that have direct impact on the material performance. An additional reason for microstructural characterization is introduced by the methods for spatially locating the recrystallization nuclei, used in more ergonomic concepts of device fabrication. Metal and SiO2 strip overlayers have been applied here, on a-Si to fix the position of the solidification seeds after laser melting. The control of many aspects of the thin film microstructure can be achieved with a collection of a few inspection techniques like AFM, SEM, EC contrast, TEM, X-ray diffraction (XRD), some of which require preliminary grain decoration treatment, and some do not. The results of different irradiation experiments, are herein illustrated, enlightened by the above characterization techniques, for providing information on surface morphology, grain arrangement, preferred orientation. PMID:10702980

  7. The Effect of Excimer Laser Treatment on the Surface Roughness and Fracture Strength of Alumina Substrates

    SciTech Connect

    Smoot, J.E.

    1998-05-13

    The microelectronics industry requires alumina substrates with exceptionally smooth surfaces and few surface defects to allow successful deposition of metallic films for reliable electronic performance. Irradiation by a 248-nm wavelength excimer laser beam (KrF) at a fluence of 125 mJ/mm{sup 2} and at various angles of incidence is shown to significantly reduce the surface roughness of alumina substrates. However, irradiation also creates a fine particulate deposit of alumina that only partially adheres to the substrate and impedes deposition of metal films. Annealing in air between 1350 C and 1450 C was found to remove the particles by sintering. As-received material showed surface roughness average (R{sub a}) mean values of 457 nm, which was reduced to 60 nm (mean) following irradiation and 71 nm (mean) following irradiation and annealing at 1350 C. Irradiation also produced a decrease in the number and severity of surface defects. The flexural strength and Weibull modulus were both increased by laser irradiation and thermal treatment. Flexural strength went from an as-received value of 450 MPa to 560 MPa following irradiation/sintering, measured at 10% probability of failure. The Weibull modulus was increased from the as-received value of about 9, to about 13 following irradiation/sintering. It was concluded that irradiation at an angle of incidence of 60{degree} from perpendicular was most effective in producing a low surface roughness.

  8. Automated superficial lamellar keratectomy augmented by excimer laser masked PTK in the management of severe superficial corneal opacities

    PubMed Central

    Alio, J L; Javaloy, J; Merayo, J; Galal, A

    2004-01-01

    Aim: To assess superficial lamellar keratectomy augmented by excimer laser smoothening with sodium hyaluronate 0.25%, for the management of superficial corneal opacities. Methods: Consecutive procedure performed in 14 eyes (13 patients) with an automated microkeratome and excimer laser phototherapeutic keratectomy (PTK) smoothening using sodium hyaluronate 0.25%. Main outcome measures: UCVA, BCVA, pachymetry, degree of haze, ray tracing analysis, and complications. Mean follow up was 12 (SD 1.6) months. Results: Mean preoperative haze from previous corneal refractive surgeries was 3.5 (SD 0.5) (11/14 cases). In one case, opacity was caused by ocular trauma and in two by infectious keratitis. The mean preoperative UCVA was 0.7 logMAR (0.2 (SD 0.13) decimal value). BCVA was 0.4 logMAR (0.4 (SD 0.17) decimal value). Mean preoperative corneal pachymetry was 508 (SD 62.5) µm and mean opacity depth measured by corneal confocal microscopy was 115.2 (SD 49.4) µm. At 6 months, 71.4% of the eyes with previous corneal refractive surgery showed grade I haze or less. Mean postoperative corneal pachymetry at 6 months was 352.36 (SD 49.05) µm. Conclusions: Automated superficial lamellar keratectomy combined with excimer laser PTK smoothening assisted by sodium hyaluronate 0.25% induces a significant improvement of corneal transparency and visual acuity in cases of corneal opacity caused by previous refractive surgery, ocular trauma, and keratitis. PMID:15377553

  9. KrF excimer laser lithography with a phase-shifting mask for gigabit-scale ultra large scale integration

    NASA Astrophysics Data System (ADS)

    Imai, Akira; Terasawa, Tsuneo; Hasegawa, Norio; Asai, Naoko; Tanaka, Toshihiko P.; Okazaki, Shinji

    1996-10-01

    Resolution-enhancement technologies such as alternating-type phase-shifting masks (PSMs), half-tone PSMs, and the off- axis illumination method in optical lithography are necessary for manufacturing gigabit-scale ultra large scale integration (ULSI) devices. Because an alternating-type PSM is the most effective way to enhance resolution, we examine the resolution capabilities of KrF excimer laser lithography combined with the use of an alternating-type PSM through simulations. Our goal is to apply this technique to attain pattern delineation smaller than 200 nm. We simulate light intensity profiles for various types of PSMs in terms of the 3-D mask structure, and find that a PSM structure with a spin-on glass (SOG) phase shifter on a Cr layer that is thinner than in a conventional mask is one of the best choices for KrF excimer laser lithography. We examine potential problems such as the durability of the SOG phase shifters to KrF excimer laser irradiation exposure, and phase angle error due to the surface topography of the Cr aperture patterns. From our experimental results, we confirm that the optical characteristics of the PSM are not degraded, and the phase angle can be controlled with an accuracy sufficient for gigabit-scale ULSI device fabrication. Improved PSMs with a thin Cr layer and SOG phase shifters were successfully used to fabricate several layers of experimental 1-Gbit dynamic random access memory (DRAM) devices with sufficient resolution capability.

  10. Study of effects of sidewall angle on process window using 193nm CPL masks in a 300mm wafer manufacturing environment

    NASA Astrophysics Data System (ADS)

    Cheng, Yung Feng; Chou, Yueh Lin; Lin, C. L.; Huang, Peter

    2005-11-01

    As semiconductor process technology moves down below 90nm and 65nm, more and more wafer fabs are starting to apply 193nm CPL (Chromeless Phase Lithography) technology as the main lithography strategy for their most critical layers. However the 3D pattern profile is another critical factor, which affects image intensity and final process window. Since 193nm CPL is a relatively new technology in the semiconductor industry, it is important for us to understand the key mask specifications of 193nm CPL and their impact on wafer-level imaging. In this paper, we will study the effects of sidewall angle on process window and wafer CD using 193nm CPL masks in a 300mm wafer manufacturing environment. We begin our experiment by making several special 193nm CPL masks. These masks have been specially designed with different sidewall angles (SWA) with phase of 180 degrees. The sidewall angle spread represents approximately 10 degrees. We use specially designed test patterns that are compatible at the 65nm technology node. In our experiment, we first study the correlation between AFM (atomic force microscope)-determined profile angle and lithographic process behavior. In addition, simulation was also used to predict the impact of 3D profile on process performance. All lithographic experiments were performed on 300mm wafers using a high NA ASML 193nm scanner and high contrast resist. In this study, we have focused on the impact of sidewall angle on wafer process performance by comparing the wafer CD and pattern profile through focus. In order to establish more effective specifications of angle control in 193nm CPL between mask shop and wafer fabs, all AFM, wafer CD, and simulation results will be compared and correlated.

  11. Analyzing velocity map images to distinguish the primary methyl photofragments from those produced upon C-Cl bond photofission in chloroacetone at 193 nm.

    PubMed

    Alligood, Bridget W; Straus, Daniel B; Butler, Laurie J

    2011-07-21

    We use a combination of crossed laser-molecular beam scattering experiments and velocity map imaging experiments to investigate the three primary photodissociation channels of chloroacetone at 193 nm: C-Cl bond photofission yielding CH(3)C(O)CH(2) radicals, C-C bond photofission yielding CH(3)CO and CH(2)Cl products, and C-CH(3) bond photofission resulting in CH(3) and C(O)CH(2)Cl products. Improved analysis of data previously reported by our group quantitatively identifies the contribution of this latter photodissociation channel. We introduce a forward convolution procedure to identify the portion of the signal, derived from the methyl image, which results from a two-step process in which C-Cl bond photofission is followed by the dissociation of the vibrationally excited CH(3)C(O)CH(2) radicals to CH(3) + COCH(2). Subtracting this from the total methyl signal identifies the methyl photofragments that result from the CH(3) + C(O)CH(2)Cl photofission channel. We find that about 89% of the chloroacetone molecules undergo C-Cl bond photofission to yield CH(3)C(O)CH(2) and Cl products; approximately 8% result in C-C bond photofission to yield CH(3)CO and CH(2)Cl products, and the remaining 2.6% undergo C-CH(3) bond photofission to yield CH(3) and C(O)CH(2)Cl products. PMID:21786998

  12. Choice of the laser wavelength for a herpetic keratitis treatment

    NASA Astrophysics Data System (ADS)

    Razhev, Alexander M.; Bagayev, Sergei N.; Chernikh, Valery V.; Kargapoltsev, Evgeny S.; Trunov, Alexander; Zhupikov, Andrey A.

    2002-06-01

    For the first time the effect of the UV laser radiation to human eye cornea with herpetic keratitis was experimentally investigated. In experiments the UV radiation of ArF (193 nm), KrCl (223 nm), KrF (248 nm) excimer lasers were used. Optimal laser radiation parameters for the treatment of the herpetic keratitis were determined. The immuno-biochemical investigations were carried out and the results of clinical trials are presented. The maximum ablation rate was obtained for the 248 nm radiation wavelength. The process of healing was successful but in some cases the haze on the surface of the cornea was observed. When used the 193 nm radiation wavelength the corneal surface was clear without any hazes but the epithelization process was slower than for 248 nm wavelength and in some cases the relapse was occurred. The best results for herpetic keratitis treatment have been achieved by utilizing the 223 nm radiation wavelength of the KrCl excimer laser. The use of the 223 nm radiation wavelength allows treating the herpetic keratitis with low traumatic process of ablation and provides high quality of corneal surface.

  13. Characterization of individual atmospheric aerosol particles with SIMS and laser-SNMS

    NASA Astrophysics Data System (ADS)

    Peterson, R. E.; Nair, A.; Dambach, S.; Arlinghaus, H. F.; Tyler, B. J.

    2006-07-01

    The surface chemistry of atmospheric aerosol particles is important in determining how these particles will effect human health, visibility, climate and precipitation chemistry. In previous work, it has been shown that ToF-SIMS can provide significant valuable information on both organic and inorganic constituents of the aerosol. It has been found, however, that ToF-SIMS with a Ga + primary ion beam offers very low sensitivity to poly-aromatic hydrocarbons (PAHs) and heavy metals, two important classes of pollutants. In this work the utility of laser-SNMS for detection of these pollutants has been explored. Two laser systems, a 193 nm excimer laser and a 157 nm excimer laser have been utilized. Each approach has advantages. ToF-SIMS has the highest sensitivity to alkali metals and aliphatic hydrocarbons. The 193 nm laser provides very high sensitivity to lead and other metals. The 157 nm laser greatly enhances sensitivity to PAHs which has enabled detection of PAHs on the surface of individual particles.

  14. Surface structural transformation of sintered alumina induced by excimer laser irradiation

    NASA Astrophysics Data System (ADS)

    Dupas-Bruzek, C.; Laude, L. D.; Langenhorst, F.; Kolev, K.

    2003-04-01

    Laser surface processing of ceramics is important for several structural, tribological, optical and electronic applications. However, little is known on the transformation mechanism of alumina under excimer laser irradiation. In this work, a sintered alumina type was typically irradiated at 0.8 J cm-2 and cooled at two drastically different rates. Optical investigations on the irradiated specimens allow to conclude that the amount of transformation products is very much dependant on the cooling rates. Transmission electron microscopy observations show that the transformation product is constituted of an amorphous matrix in which are embedded either (i) copper grains (size up to 1 μm) in slowly cooled samples or (ii) smaller copper or CuAl2O4 spinel grains (size up to 100 nm) in rapidly cooled samples. The cement that is present in the starting material at grain boundaries is found to play an important role on the formation of the new amorphous or crystalline materials. All the copper grains exhibit a <120> common zone axis perpendicular to the irradiated surface and parallel to the bulk-to-surface thermal gradient, which drives that preferred orientation. These results reveal the details of the phenomenology of the laser-induced material transformation. This latter decomposes into (i) the incipient formation of tiny γ-Al2O3 nuclei, (ii) integration of Cu ions present in the melt into these tiny γ-Al2O3 nuclei that transform into CuAl2O4 spinel, and (iii) further sedimentation of Cu ions onto the resulting spinel grains acting as nucleation centers and finally formation of larger copper-rich grains. The minimum nucleation rate of crystalline grains is estimated to be equal to 1024 cm-3 s-1, while the growth rate is of the order of 0.1 m s-1 in both samples. Both bulk thermal diffusive and convective transports control the transformation of matter.

  15. Etching of fused silica and glass with excimer laser at 351 nm

    NASA Astrophysics Data System (ADS)

    Zimmer, K.; Braun, A.; Böhme, R.

    2003-03-01

    The etching of solid surfaces at the interface to liquids is a new promising method for micro-machining of transparent materials. To extend the method to additional materials the pulsed radiation of a XeF-excimer laser (351 nm) was used for etching different types of glass (Corning Inc.: Pyrex, 7059 and Schott Group: D263, AF45) and fused silica for comparison. The etch rates of the investigated materials increase almost linear at low laser fluences. Threshold fluences for glass as low as 0.5 J/cm 2 and etch rates from 6 to 10 nm per pulse at 1 J/cm 2 have been determined. The etch rate and the threshold fluence depend also on the used liquid, consisting of a solvent (acetone, toluene) and a certain concentration of dissolved pyrene, but only little on the glass type. Due to the low etch rate typically very smooth surfaces are achieved. The surface roughness measured by AFM on Corning 7059-glass at an etch depth of 3.7 μm is as low as 4 nm. Contrary to the other glasses the surface roughness of Pyrex is much higher and dominated by typical arbitrary etch pits with micron dimensions. Comparing the etching of fused silica at a wavelength of 248 and 351 nm the used solution influences both the etch threshold and the etch rate. In accordance to earlier investigations at 248 nm also XeF-laser etching at the interface to an absorbing liquid results in a good surface quality, well defined patterns and almost no debris deposition. Thus, this technique is a good candidate for precise micro-machining applications.

  16. Optical spectroscopy study of pulsed excimer laser generated plasma from CuO

    SciTech Connect

    Adhi, K.P.; Kale, S.; Padhye, Y.; Limaye, A.V.; Ogale, S.B.

    1995-12-15

    Optical emissions from pulsed excimer laser induced plasma emanating from CuO target are studied by an Optical Multichannel Analyzer system in the context of its implications for thin film growth by Pulsed Laser Deposition. The plasma is generated in four different ambients viz. hydrogen, helium, oxygen (pressure of 100 mTorr in each case) and vacuum (2 {times} 10{sup {minus}5} Torr) at different energy densities from 1 to 3.5 J/cm{sup 2}. The plasma constituents and their evolution in the growth space (i.e. at a distance of 1.5 cm from the target) has been studied. Various transitions corresponding to Cu(I), H(I), Cu(II) and O(II) are observed. The observation of strong transitions due to O(II) in the plasma formed in vacuum, hydrogen and helium suggests significant degree of ionization of atoms via molecular splitting and inverse Bremsstrahlung process during early plasma formation. The persistence of ionicity in the plasma can be attributed to long recombination lifetimes for the specific conditions used. In the case of ablation in oxygen ambient a very significant and remarkably selective enhancement of the copper vapor lasing transition at 510.5 nm is observed which brings out the role of oxygen molecules in sustaining the radiation trapping condition. The changes in the concentrations of neutrals and ions are a function of the laser energy density are also examined. It is argued that impingement of ions/atoms in an excited state on the growing surface can potentially lead to localized energy deposition via non-radiative deexcitation resulting into enhancement of film quality and density.

  17. 193 nm Ultraviolet Photodissociation Mass Spectrometry of Tetrameric Protein Complexes Provides Insight into Quaternary and Secondary Protein Topology.

    PubMed

    Morrison, Lindsay J; Brodbelt, Jennifer S

    2016-08-31

    Protein-protein interfaces and architecture are critical to the function of multiprotein complexes. Mass spectrometry-based techniques have emerged as powerful strategies for characterization of protein complexes, particularly for heterogeneous mixtures of structures. In the present study, activation and dissociation of three tetrameric protein complexes (streptavidin, transthyretin, and hemoglobin) in the gas phase was undertaken by 193 nm ultraviolet photodissociation (UVPD) for the characterization of higher order structure. High pulse energy UVPD resulted in the production of dimers and low charged monomers exhibiting symmetrical charge partitioning among the subunits (the so-called symmetrical dissociation pathways), consistent with the subunit organization of the complexes. In addition, UVPD promoted backbone cleavages of the monomeric subunits, the abundances of which corresponded to the more flexible loop regions of the proteins. PMID:27480400

  18. Collision-induced desorption in 193-nm photoinduced reactions in (O{sub 2}+CO) adlayers on Pt(112)

    SciTech Connect

    Han Song; Ma Yunsheng; Matsushima, Tatsuo

    2005-09-01

    The spatial distribution of desorbing O{sub 2} and CO{sub 2} was examined in 193-nm photoinduced reactions in O{sub 2}+CO adlayers on stepped Pt (112)=[(s)3(111)x(001)]. The O{sub 2} desorption collimated in inclined ways in the plane along the surface trough, confirming the hot-atom collision mechanism. In the presence of CO(a), the product CO{sub 2} desorption also collimated in an inclined way, whereas the inclined O{sub 2} desorption was suppressed. The inclined O{sub 2} and CO{sub 2} desorption is explained by a common collision-induced desorption model. At high O{sub 2} coverage, the CO{sub 2} desorption collimated closely along the (111) terrace normal.

  19. Scanning electron microscopy and thermal characteristics of dentin ablated by a short-pulse XeCl excimer laser.

    PubMed

    Neev, J; Stabholtz, A; Liaw, L H; Torabinejad, M; Fujishige, J T; Ho, P D; Berns, M W

    1993-01-01

    The interaction of a short pulse XeCl excimer laser radiation with human dentin was investigated. The dependence of surface temperatures and temperature gradients into the treated teeth on laser parameters such as fluence (0.5J/cm2-7J/cm2), pulse repetition rate (1Hz-35Hz), and spot size (0.004cm2-0.12cm2) was studied. Additionally, the effect of fluence and pulse repetition rate on dentin microstructure was studied using scanning electron microscopy (SEM). It is demonstrated that this "cold ablation" excimer laser can result in significant thermal modification in the dentin surfaces. Changes include the formation of melted dentin grains, which uniformly cover the surface and the exposed dentin tubules. Maximum temperatures of the ablated surfaces, however, remained relatively low at most laser parameters used. Also, the immediate neighborhood of the root canal was essentially undisturbed at most laser parameters. These observations suggest that with the appropriate choice of parameters XeCl lasers can be effective in producing surface structures that may prove useful in enhancing bond strength or other applications in dentistry, without exposing tooth pulp to significant temperature elevation. PMID:8515674

  20. Identical Excimer Laser PTK Treatments in Rabbits Result in Two Distinct Haze Responses

    PubMed Central

    McCally, Russell L.; Connolly, Patrick J.; Stark, Walter J.; Jain, Sandeep; Azar, Dimitri T.

    2006-01-01

    Purpose. To obtain objective light-scattering measurements to test a hypothesis that identical PTK treatments cause distinct low- and high-level light-scattering responses in rabbit corneas. Methods. An excimer laser was used to produce identical 6-mm diameter phototherapeutic keratectomy treatments (PTK) in 32 pigmented rabbits. Eyes were treated by performing a 40-μm epithelial ablation, followed by a 100-μm stromal PTK. Objective scattering measurements were made before treatment, weekly up to 5 weeks, and then biweekly to 9 weeks. Confocal microscopy was performed on several corneas at 4 and 7 weeks. Results. Mean scattering levels split into distinct low- and high-scattering groups 2 weeks after treatment and remained distinct until week 7 (P < 0.003). Scattering in the low group reached a broad peak that lasted from weeks 2 to 4 at approximately 3 times the pretreatment level. Scattering in the high group peaked at 3 weeks at approximately 12 times the pretreatment level. Scattering levels diminished after reaching their peaks. Confocal images showed a band of highly reflective material in the anterior stroma that extended much deeper in corneas from the high group. The reflective band in the highly scattering corneas obscured the posterior stroma from view for up to 5 weeks. Conclusions. Quantitative scattering data obtained with the scatterometer suggest that identical PTK treatments indeed result in distinct low- and high-level light-scattering responses in rabbits. PMID:17003417

  1. Electrical activation phenomena induced by excimer laser annealing in B-implanted silicon

    SciTech Connect

    Fortunato, G.; Mariucci, L.; La Magna, A.; Alippi, P.; Italia, M.; Privitera, V.; Svensson, B.; Monakhov, E.

    2004-09-20

    The activation process induced by excimer laser annealing (ELA) has been investigated in 10 keV B-implanted samples. It is found that for energy densities inducing melt depths of the order or larger of the implanted region the junction depth is controlled by the melt depth, with activation approaching 100% and box-shaped carrier density distributions with abrupt junction profile. For energy densities inducing a melting shallower than the implanted region, two different activation mechanisms have been identified: the first occurring in the molten region and leading to complete B activation; the second occurring in the region immediately below the molten zone and leading to thermal activation of B, induced by the heat wave propagating into the Si wafer. This last process is characterized by an activation energy of 5 eV and is not accompanied by B diffusion. As a consequence, a deep tail of active B is produced, preventing the possibility to form abrupt and ultrashallow junctions. These results suggest that for the formation of ultrashallow junctions it is essential to combine ELA with ultralow energy ion implantation.

  2. Raman scattering measurements in flames using a tunable KrF excimer laser

    NASA Technical Reports Server (NTRS)

    Wehrmeyer, Joseph A.; Cheng, Tsarng-Sheng; Pitz, Robert W.

    1992-01-01

    A narrow-band tunable KrF excimer laser is used as a spontaneous vibrational Raman scattering source to demonstrate that single-pulse concentration and temperature measurements, with only minimal fluorescence interference, are possible for all major species (O2, N2, H2O, and H2) at all stoichiometries (fuel-lean to fuel rich) of H2-air flames. Photon-statistics-limited precisions in these instantaneous and spatially resolved single-pulse measurements are typically 5 percent, which are based on the relative standard deviations of single-pulse probability distributions. In addition to the single-pulse N2 Stokes/anti-Stokes ratio temperature measurement technique, a time-averaged temperature measurement technique is presented that matches the N2 Stokes Raman spectrum to theoretical spectra by using a single intermediate state frequency to account for near-resonance enhancement. Raman flame spectra in CH4-air flames are presented that have good signal-to-noise characteristics and show promise for single-pulse UV Raman measurements in hydrocarbon flames.

  3. Multilevel diffractive optical element manufacture by excimer laser ablation and halftone masks

    NASA Astrophysics Data System (ADS)

    Quentel, Francois; Fieret, Jim; Holmes, Andrew S.; Paineau, Sylvain

    2001-06-01

    A novel method is presented to manufacture multilevel diffractive optical elements (DOEs) in polymer by single- step KrF excimer laser ablation using a halftone mask. The DOEs have a typical pixel dimension of 5 micrometers and are up to 512 by 512 pixels in size. The DOEs presented are Fresnel lenses and Fourier computer generated holograms, calculated by means of a conventional iterative Fourier transform algorithm. The halftone mask is built up as an array of 5 micrometers -square pixels, each containing a rectangular or L- shaped window on an opaque background. The mask is imaged onto the polymer with a 5x, 0.13 NA reduction lens. The pixels are not resolved by the lens, so they behave simply as attenuators, allowing spatial variation of the ablation rate via the window size. The advantages of halftone mask technology over other methods, such as pixel-by-pixel ablation and multi-mask overlay, are that it is very fast regardless of DOE size, and that no high-precision motion stages and alignment are required. The challenges are that the halftone mask is specific to the etch curve of the polymer used, that precise calibration of each grey-level is required, and that the halftone mask must be calculated specifically for the imaging lens used. This paper describes the design procedures for multilevel DOEs and halftone masks, the calibration of the various levels, and some preliminary DOE test results.

  4. Post-growth annealing of germanium-tin alloys using pulsed excimer laser

    SciTech Connect

    Wang, Lanxiang; Wang, Wei; Zhou, Qian; Yeo, Yee-Chia; Pan, Jisheng; Zhang, Zheng; Tok, Eng Soon

    2015-07-14

    We investigate the impact of pulsed excimer laser anneal on fully strained germanium-tin alloys (Ge{sub 1−x}Sn{sub x}) epitaxially grown on Ge substrate by molecular beam epitaxy. Using atomic force microscopy, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy, the morphological and compositional evolution of Ge{sub 1−x}Sn{sub x} with Sn content up to 17% after annealing using various conditions is studied. Ge{sub 0.83}Sn{sub 0.17} samples annealed at 80 mJ/cm{sup 2} or 150 mJ/cm{sup 2} have no observable changes with respect to the as-grown sample. However, Ge{sub 0.83}Sn{sub 0.17} samples annealed at 250 mJ/cm{sup 2} or 300 mJ/cm{sup 2} have Sn-rich islands on the surface, which is due to Sn segregation in the compressively strained epitaxial film. For Ge{sub 0.89}Sn{sub 0.11}, significant Sn redistribution occurs only when annealed at 300 mJ/cm{sup 2}, indicating that it has better thermal stability than Ge{sub 0.83}Sn{sub 0.17}. A mechanism is proposed to explain the formation of Sn-rich islands and Sn-depleted regions.

  5. Characteristics of excitation discharge of an excimer laser in gas density depletion

    NASA Astrophysics Data System (ADS)

    Imada, Go; Masuda, Wataru; Yatsui, Kiyoshi

    1998-12-01

    The influences of gas density depletion on the highly- repetitive, high-pressure, pulsed glow discharge for excitation of excimer laser have been investigated eliminating the other instabilities, such as shock waves, residual ions, discharge products and electrode heating. The gas density depletion is simulated by utilizing a subsonic flow between the curved electrodes. The comparison has been made on the discharge occurred in the presence of the gas density depletion with the second discharge on the double-pulse experiment. We have found that the big gas density non uniformity, (Delta) (rho) /(rho) 0 approximately 3.6% corresponding to a pulse repetition rate (PRR) of approximately 20 Hz, tends to cause the arc discharge without the shocks, ions, discharge products and electrode heating. On the other hand, the second discharge on the double-pulse experiment becomes arc discharge in much smaller non uniformity ((Delta) (rho) /(rho) 0 approximately 1.2% corresponding to PRR approximately 3 Hz). The arc discharge in the double-pulse experiment might be driven by the residual ions and/or discharge products other than gas density depletion except for PRR greater than 20 Hz.

  6. Tribology and mechanical properties of excimer laser-processed Ti--Si{sub 3}N{sub 4} surfaces

    SciTech Connect

    Jervis, T.R.; Hirvonen, J.; Nastasi, M.; Kung, H.

    1995-08-01

    Titanium films were mixed, using excimer laser radiation, into the surface of bulk Si{sub 3}N{sub 4} materials. The tribological and mechanical properties of these surfaces were then evaluated using pin-on-disk and nanoindenter techniques, respectively. Reduced friction and a change in the wear mechanism that resulted in a more benign failure mode were observed. These results are interpreted as resulting from the establishment of a transfer film, changes in the compliance of the surface which reduces instantaneous stresses in the surface, and toughening of the surface, all results of the laser process.

  7. Fabrication of self-organized conical microstructures by excimer laser irradiation of cyanoacrylate-carbon nanotube composites

    NASA Astrophysics Data System (ADS)

    Liu, Yuming; Liu, Liang; Fan, Shoushan

    2005-02-01

    Self-organized conical microstructures are fabricated by 308 nm XeCl excimer laser irradiation of cyanoacrylate-carbon nanotube composites in air. The morphology of the surface on the composite films is studied, varying the total number and fluence of the applied laser pulses. A simple mechanism of the fabrication based on the evaporation of cyanoacrylate and the burning of carbon nanotubes is proposed. The conical peak structures of cyanoacrylate-carbon nanotube composite films show good field-emission properties. Similar structures are also observed on carbon nanotube arrays.

  8. Results of excimer laser photorefractive keratectomy for the correction of myopia at Cedars-Sinai Medical Center: 1993

    NASA Astrophysics Data System (ADS)

    Maguen, Ezra I.; Salz, James J.; Nesburn, Anthony B.; Warren, Cathy; Macy, Jonathan I.; Papaioannou, Thanassis; Hofbauer, John; Berlin, Michael S.

    1994-06-01

    This report summarizes the authors' 3-year experience with excimer laser photorefractive keratectomy (PRK) on 240 eyes of 161 patients. With constant laser emission parameters, nitrogen (N2) flow across the cornea was used on 79 eyes while 161 eyes had no N2 flow. 74 eyes were operated on without fixation with a suction ring. Postoperative pain management included patching and oral analgesics in 77 eyes and the use of topical Diclofenac or Ketorolac, and a therapeutic soft contact lens in 163 eyes. Follow up ranged from 1 month (206 eyes) to 36 months (10 eyes).

  9. Terraced copper growth deposited onto Teflon AF1600 by the excimer laser irradiation of Cu(hfac)TMVS

    SciTech Connect

    Popovici, D.; Piyakis, K.; Sacher, E.; Meunier, M.

    1996-12-31

    The authors are studying the feasibility of constructing Cu/fluoropolymer multilayer devices, in an effort to reduce both metal R and insulator C, a necessary condition in VLSI and GSI microelectronic applications. The laser chemical vapor deposition (LCVD) of the organometallic precursor Cu(hfac)TMVS (hexafluoroacetylacetonate)(trimethylvinylsilane) is used to grow copper films on a Teflon AF1600 substrate. Exposure to excimer laser radiation at 248 nm results in a terraced copper growth. A simple model, based on interference effects in the Teflon and copper layers, is presented to account for this structure.

  10. Research on the characteristics of H sub 2 Raman conversion pumping by a 1-J XeCl excimer laser

    SciTech Connect

    Lou, Q. , P. O. Box 8730, Beijing, China and Shanghai Institute of Optics and Fine Mechanics, Academia Sinica, P. O. Box 8211, Shanghai, China )

    1989-09-15

    Detailed results are presented of a high-efficiency Raman conversion of a 1-J XeCl excimer laser with an unstable resonator. We had 90% photon conversion of 18-MW-power XeCl laser radiation with 39% photon efficiency to the third Stokes order at 499 nm. The effects of rare-gas concentration in a H{sub 2}--rare-gas mixture on the Raman conversion characteristics were investigated. Finally, stimulated Raman scattering between the excited states of H{sub 2} at high gas pressure was observed, and conditions for generating these lines are discussed.

  11. Outcomes of excimer laser enhancements in pseudophakic patients with multifocal intraocular lens

    PubMed Central

    Schallhorn, Steven C; Venter, Jan A; Teenan, David; Schallhorn, Julie M; Hettinger, Keith A; Hannan, Stephen J; Pelouskova, Martina

    2016-01-01

    Purpose The aim of this study was to assess visual and refractive outcomes of laser vision correction (LVC) to correct residual refraction after multifocal intraocular lens (IOL) implantation. Patients and methods In this retrospective study, 782 eyes that underwent LVC to correct unintended ametropia after multifocal IOL implantation were evaluated. Of all multifocal lenses implanted during primary procedure, 98.7% were refractive and 1.3% had a diffractive design. All eyes were treated with VISX STAR S4 IR excimer laser using a convectional ablation profile. Refractive outcomes, visual acuities, patient satisfaction, and quality of life were evaluated at the last available visit. Results The mean time between enhancement and last visit was 6.3±4.4 months. Manifest spherical equivalent changed from −0.02±0.83 D (−3.38 D to +2.25 D) pre-enhancement to 0.00±0.34 D (−1.38 D to +1.25 D) post-enhancement. At the last follow-up, the percentage of eyes within 0.50 D and 1.00 D of emmetropia was 90.4% and 99.5%, respectively. Of all eyes, 74.9% achieved monocular uncorrected distance visual acuity 20/20 or better. The mean corrected distance visual acuity remained the same before (−0.04±0.06 logMAR [logarithm of the minimum angle of resolution]) and after LVC procedure (−0.04±0.07 logMAR; P=0.70). There was a slight improvement in visual phenomena (starburst, halo, glare, ghosting/double vision) following the enhancement. No sight-threatening complications related to LVC occurred in this study. Conclusion LVC in pseudophakic patients with multifocal IOL was safe, effective, and predictable in a large cohort of patients. PMID:27175059

  12. Interstitial trapping in Fe-implanted Al after excimer laser annealing

    NASA Astrophysics Data System (ADS)

    Swanson, M. L.; Howe, L. M.; Quenneville, A. F.; Nilson, J. A.

    1983-12-01

    Laser annealing was used to create a supersaturated solution of Fe atoms in Al, in order that channeling measurements of self-interstitial trapping could be made. A single crystal of Al was implanted with 40 keV 56Fe to a fluence of 1.6×10 15 ions cm -2. A 4 mm diameter region of the crystal was annealed in air with a XeCl excimer laser at an energy density of ˜ 6 J cm -2. This treatment produced a relatively perfect crystal; the normalized yield of 1 MeV He + ions from near-surface Al atoms for <110> alignment at 35 K was 0.04. The Fe atoms were ˜ 90% substitutional, corresponding to a solubility of ˜ 0.3 at%, as compared with only ˜ 0.02 at% obtained by a water quench from 873 K. The crystal was then irradiated with 1 MeV He + at 70 K to a fluence of ˜ 5 × 10 15 ions cm -2, in order to create mobile Al self-interstitial atoms which could be trapped by the Fe atoms. A channeling analysis of the resulting displacement of Fe atoms indicated that they trapped self-interstitials strongly, as observed for other small solute atoms in Al. As no flux peaking in the backscattering yield from Fe atoms was observed for a <110> angular scan, the results indicate that the trapping configuration may differ from that observed for Cr, Mn or Cu solute atoms in Al. The trapped interstitials were annihilated by vacancy migration near 200 K.

  13. Investigation into the interaction of a XeCl excimer laser with hard tissue

    NASA Astrophysics Data System (ADS)

    Murray, Andrea K.; Dickinson, Mark R.

    2000-06-01

    An investigation into the interaction of a fiber deliverable, long pulse, xenon chloride (308 nm) excimer laser with hard biotissue has been carried out. The laser produces pulses of 200+ ns as opposed to around 10 - 20 ns for most of the previously reported data. The threshold of ablation and the maximum ablation depth (AD) in human molar dentine were found to be 0.30 +/- 0.05 J/cm2 and 1.57 +/- 0.04 micrometer/pulse respectively. The threshold for enamel was found to be above the achievable fluence with the available optics. The ablation process was investigated as a function of fluence (approximately 0.1 - 6 J/cm2), pulse repetition rate (PRR) (5 - 25 Hz) and number of pulses (500 - 4000). Each variable was altered independently of the other two. At a constant number of pulses, ablation depth per pulse was found to increase linearly as a function of fluence, up to a saturation fluence of approximately 4 J/cm2. Variation of the PRR alone was found to affect both the ablation threshold and the AD. For constant fluence and PRR, AD decreases non- linearly with an increasing number of pulses. This could be because at high pulse numbers the craters are deep, the walls of the crater absorb more energy and as it is increasingly difficult for the debris to escape, shielding of the tissue occurs. Shielding may also be due to absorption in a luminescent plume. At high fluence and PRR, sharp holes were formed in the dentine although charring was sometimes found around the edges. High PRR also induced considerable mechanical damage.

  14. The effect of microarc oxidation and excimer laser processing on the microstructure and corrosion resistance of Zr-1Nb alloy

    NASA Astrophysics Data System (ADS)

    Yang, Jiaoxi; Wang, Xin; Wen, Qiang; Wang, Xibing; Wang, Rongshan; Zhang, Yanwei; Xue, Wenbin

    2015-12-01

    The main purpose of this research was to investigate the effect of microarc oxidation (MAO) and excimer laser processing on the corrosion resistance of Zr-1Nb alloy in service environment. The pre-oxide film was fabricated on the surface of Zr-1Nb cladding tubes by MAO processing, and then subjected to KrF excimer laser irradiation. The surface morphology of the pre-oxide film was observed using a scanning electron microscope; phase compositions and quantities were determined using an X-ray diffraction; surface roughness was determined using a profilometer; and thermal expansion coefficient was measured using a dilatometer. Autoclave experiments were conducted for 94 days in an aqueous condition of 360 °C under 18.6 MPa in 0.01 mol/L LiOH solutions. The results showed that MAO + laser treatment resulted in a significant increase in the corrosion resistance of Zr-1Nb cladding tubes at high temperatures, because laser melting and etching could lead to a reduction in surface roughness and an increase in compactness of the pre-oxide film, and laser processing could promote the transformation of m-ZrO2 phase to t-ZrO2 phase. The best corrosion resistance was obtained when the pulse energy was 500 mJ, scanning speed was 0.13 mm/s, and pulse number was 2400.

  15. Effect of triggered discharge using an excimer laser with high-repetition-rate of the order of kilohertz

    SciTech Connect

    Yamaura, Michiteru; Watanabe, Takashi; Hayashi, Nobuya; Ihara, Satoshi

    2005-03-28

    The triggering ability of the laser-triggered lightning method is improved by using a KrF excimer laser with a high-repetition-rate of the order of kHz order. It is clarified that the effect of a triggered discharge is considerably enhanced when the plasma density is greater than 10{sup 13} cm{sup -3}. Thus far, the laser-triggered lightning method has not been expected to display a triggering ability since one pulse of an excimer laser possesses energy of less than 1 J, and the produced plasma has a low density of 10{sup 12} cm{sup -3}, its plasma density is one order lower than that required for its application in the triggering and guiding of lightning discharge. The enhancement of plasma density achieved by utilizing the accumulation effect of charged particles generated by the high-repetition-rate laser was 10{sup 13} cm{sup -3}. This led to an effective a 50% reduction in the self-breakdown voltage.

  16. Analysis of damage threshold of K9 glass irradiated by 248-nm KrF excimer laser

    NASA Astrophysics Data System (ADS)

    Wang, Xi; Shao, Jingzhen; Li, Hua; Nie, Jinsong; Fang, Xiaodong

    2016-02-01

    The theoretical model of K9 glass irradiated by a 248-nm KrF excimer laser was established, and a numerical simulation was performed to calculate temperature and thermal stress fields in the K9 glass sample using the finite element method. The laser-induced damage thresholds were defined and calculated, and the effect of repetition frequency and the number of pulses on the damage threshold were also studied. Furthermore, the experiment research was carried out to confirm the numerical simulation. The damage threshold and damage morphology were analyzed by means of a metallurgical microscope and scanning electron microscopy. The simulation and experimental results indicated that the damage mechanism of K9 glass irradiated by a KrF excimer laser was melting damage and stress damage, and the stress damage first appeared inside the K9 glass sample. The tensile stress damage threshold, the compressive stress damage threshold, and the melting damage threshold were 0.64, 0.76, and 1.05 J/cm2, respectively. The damage threshold decreased with increasing repetition frequency and number of laser pulses. The experimental results indicated that the damage threshold of K9 glass was 2.8 J/cm2.

  17. Preparation of Ultrafine Fe–Pt Alloy and Au Nanoparticle Colloids by KrF Excimer Laser Solution Photolysis

    PubMed Central

    2009-01-01

    We prepared ultrafine Fe–Pt alloy nanoparticle colloids by UV laser solution photolysis (KrF excimer laser of 248 nm wavelength) using precursors of methanol solutions into which iron and platinum complexes were dissolved together with PVP dispersant to prevent aggregations. From TEM observations, the Fe–Pt nanoparticles were found to be composed of disordered FCC A1 phase with average diameters of 0.5–3 nm regardless of the preparation conditions. Higher iron compositions of nanoparticles require irradiations of higher laser pulse energies typically more than 350 mJ, which is considered to be due to the difficulty in dissociation of Fe(III) acetylacetonate compared with Pt(II) acetylacetonate. Au colloid preparation by the same method was also attempted, resulting in Au nanoparticle colloids with over 10 times larger diameters than the Fe–Pt nanoparticles and UV–visible absorption peaks around 530 nm that originate from the surface plasmon resonance. Differences between the Fe–Pt and Au nanoparticles prepared by the KrF excimer laser solution photolysis are also discussed. PMID:20596425

  18. Excimer laser assisted re-oxidation of BaTiO3 thin films on Ni metal foils

    NASA Astrophysics Data System (ADS)

    Bharadwaja, S. S. N.; Rajashekhar, A.; Ko, S. W.; Qu, W.; Motyka, M.; Podraza, N.; Clark, T.; Randall, C. A.; Trolier-McKinstry, S.

    2016-01-01

    Excimer laser assisted re-oxidation for reduced, crystallized BaTiO3 thin films on Ni-foils was investigated. It was found that the BaTiO3 can be re-oxidized at an oxygen partial pressure of ˜50 mTorr and substrate temperature of 350 °C without forming a NiOx interface layer between the film and base metal foil. The dielectric permittivity of re-oxidized films was >1000 with loss tangent values <2% at 100 Hz, 30 mVrms excitation signal. Electron Energy Loss Spectroscopy indicated that BaTiO3 thin films can be re-oxidized to an oxygen stoichiometry close to ˜3 (e.g., stoichiometric). High resolution cross sectional transmission electron microscopy showed no evidence of NiOx formation between the BaTiO3 and the Ni foil upon excimer laser re-oxidation. Spectroscopic ellipsometry studies on laser re-oxidized [001]C and [111]C BaTiO3 single crystals indicate that the re-oxidation of BaTiO3 single crystals is augmented by photo-excitation of the ozone, as well as laser pulse induced temperature and local stress gradients.

  19. Effect of excimer laser surface melting on the corrosion performance of a SiCp/Al metal matrix composite

    NASA Astrophysics Data System (ADS)

    Qian, D. S.; Zhong, X. L.; Hashimoto, T.; Yan, Y. Z.; Liu, Z.

    2015-03-01

    Excimer laser surface melting (LSM) was performed to improve the corrosion resistance of the SiCp/AA2124 metal matrix composite (MMC). Corrosion evaluation of the MMCs showed evident improvement of the corrosion resistance after LSM, which was mainly attributed to the formation of a highly homogeneous surface layer with the dissolution of intermetallic particles and the redistribution of the alloying elements, as well as Si and C resulted from the decomposition of SiC particles. The elimination of micro-pores and micro-crevices introduced by the SiC particles after LSM also contributed to the improved corrosion resistance of the MMC.

  20. Stimulated Raman scattering in lead vapor pumped by a long-pulse 1-J XeCl excimer laser

    SciTech Connect

    Lou, Q.; Huo, Y.

    1988-08-15

    The parametric dependence of the output energies and efficiencies for the Raman conversion of the radiation from a long-pulse 1-J XeCl excimer laser in Pb vapor was investigated. The effects of atom depletion and buffer gas on the stimulated Raman scattering output were discussed in detail. Multipeak structures of the waves of the Raman-shifted pulses were observed which could be attributed to the coherent effects in Raman scattering. A computer model was introduced to explain the multipeak structures of the stimulated Raman scattering waveforms.

  1. High-NA high-throughput scanner compatible 2-kHz KrF excimer laser for DUV lithography

    NASA Astrophysics Data System (ADS)

    Nakarai, Hiroaki; Hisanaga, Naoto; Suzuki, Natsushi; Matsunaga, Takeshi; Asayama, Takeshi; Akita, Jun; Igarashi, Toru; Ariga, Tatsuya; Bushida, Satoru; Enami, Tatsuo; Nodomi, Ryoichi; Takabayashi, Yuichi; Sakanishi, Syouich; Suzuki, Takashi; Tomaru, Hitoshi; Nakao, Kiyoharu

    2000-07-01

    We have succeeded in the development of an excimer laser with ultra narrow bandwidth applicable to high N.A. scanners targeting on the 0.13micrometers -design rule. Key word of our solution for 0.13micrometers -design rule was 'extended technologies of currently available KrF excimer laser unit. As the result we could shorten development time remarkably. The narrower the laser spectrum, the less the influence of chromatic aberration on exposure projection lens; this is a well-known fact. We have developed the technologies to achieve spectral bandwidths less than 0.5pm, 20 percent narrower than our current model G20K. In order to attain this number, the major design change was made on line narrowing module, which was redesigned to minimize the dispersion of wavelength element. In addition gas condition was fine-tuned for the new line narrowing module. Integrated energy stability has been improved within +/- 0.35 percent with 35 pulses window by the introduction of a high efficiency pules power module and a faster gas circulation system. The rest of oscillation performances and durability equate with the base model G20K. The intelligent gas control system extended gas exchange interval up to 200 million pulses or 7 days. The G20K already passed through 10 billion-pulse test. Total energy loss was within 4mJ which is small enough to be compensated by gas injection and voltage change; it is a unique compensation system of Komatsu.

  2. Photodissociation of the CHFCl 2 and CHCl 3 molecules and the CHCl 2 radical in a beam at 193 nm

    NASA Astrophysics Data System (ADS)

    Yang, Xuefeng; Felder, Peter; Robert Huber, J.

    1994-11-01

    The collision-free photodissociation of CHFCl 2 and CHCl 3 at 193 nm has been studied by photofragment translational spectroscopy. In both systems the primary dissociation proceeds: exclusively via the rupture of a CCl bond. The broad and unstructured UV spectra of the parent molecules and the rather high kinetic energy release ˜45% of the available energy) in conjunction with the narrow translational energy distributions of the fragments are consistent with the CCl bond fission being a direct dissociation process. The photofragment angular distributions are characterized by anisotropy parameter β=0.5±0.1 (CHFCl 2) and β=0.0±0.1 (CHCl 3). Therefore, the photolysis of CHFCl2 involves an electronic transition polarised parallel to the line connecting the two Cl atoms. In the case of CHCl3, the nearly isotropic fragment recoil is attributed to the excitation of overlapping transitions of A 1←A 1 and E←A 1 type, respectively, hence leading to an effective anisotropy parameter βeff= aβA1 + bβE˜0. The CHCl 2 radical produced in the primary reaction CHCl 3 + hν→ CHCl 2 + Cl can absorb a further photon and is then selectively dissociated by molecular elimination of HCl according to CHCl 2 + hν→CCl + HCl

  3. Photodissociation of the CHFCl2 and CHCl3 molecules and the CHCl2 radical in a beam at 193 nm

    NASA Astrophysics Data System (ADS)

    Yang, Xuefeng; Felder, Peter; Huber, J. Robert

    1994-11-01

    The collision-free photodissociation of CHFCl2 and CHCl3 at 193 nm has been studied by photofragment translational spectroscopy. In both systems the primary dissociation proceeds exclusively via the rupture of a C-Cl bond. The broad and unstructured UV spectra of the parent molecules and the rather high kinetic energy release (approximately = 45% of the available energy) in conjunction with the narrow translational energy distributions of the fragments are consistent with the C-Cl bond fission being a direct dissociation process. The photofragment angular distributions are characterized by anisotropy parameters beta = 0.5 +/- 0.1 (CHFCl2) and beta = 0.0 +/- 0.1 (CHCl3). Therefore, the photolysis of CHFCl2 involves an electronic transition polarised parallel to the line connecting the two Cl atoms. In the case of CHCl3, the nearly isotropic fragment recoil is attributed to the excitation of overlapping transitions of A(sub 1) from A(sub 1) and E from A(sub 1) type, respectively, hence leading to an effective anisotropy parameter beta(sub eff) = a(beta) A(sub 1) +b(beta)(sub E) approximately = 0. The CHCl2 radical produced in the primary reaction CHCl3 + h(nu) yields CHCl2 + Cl can absorb a further photon and is then selectively dissociated by molecular elimination of HCl according to CHCl2 + h(nu) yields CCl + HCl.

  4. Top-Down 193-nm Ultraviolet Photodissociation Mass Spectrometry for Simultaneous Determination of Polyubiquitin Chain Length and Topology

    PubMed Central

    2016-01-01

    Protein ubiquitin modifications present a vexing analytical challenge, because of the dynamic changes in the site of modification on the substrate, the number of ubiquitin moieties attached, and the diversity of linkage patterns in which they are attached. Presented here is a method to confidently assign size and linkage type of polyubiquitin modifications. The method combines intact mass measurement to determine the number of ubiquitin moieties in the chain with backbone fragmentation by 193-nm ultraviolet photodissociation (UVPD) to determine the linkage pattern. UVPD fragmentation of proteins leads to reproducible backbone cleavage at almost every inter-residue position, and in polyubiquitin chains, the N-terminally derived fragments from each constituent monomer are identical, up to the site of conjugation. The N-terminal ubiquitin fragment ions are superimposed to create a diagnostic pattern that allows easy recognition of the dominant chain linkages. The method is demonstrated by achieving almost-complete fragmentation of monoubiquitin and then, subsequently, fragmentation of dimeric, tetrameric, and longer Lys48- and Lys63-linked ubiquitin chains. The utility of the method for the analysis of mixed linkage chains is confirmed for mixtures of Lys48 and Lys63 tetramers with known relative concentrations and for an in vitro-formulated ubiquitin chain attached to a substrate protein. PMID:25559986

  5. Characterization of Therapeutic Monoclonal Antibodies at the Subunit-Level using Middle-Down 193 nm Ultraviolet Photodissociation.

    PubMed

    Cotham, Victoria C; Brodbelt, Jennifer S

    2016-04-01

    Monoclonal antibodies (mAbs) are a rapidly advancing class of therapeutic glycoproteins that possess wide clinical utility owing to their biocompatibility, high antigen specificity, and targeted immune stimulation. These therapeutic properties depend greatly on the composition of the immunoglobulin G (IgG) structure, both in terms of primary sequence and post-translational modifications (PTMs); however, large-scale production in cell culture often results in heterogeneous mixtures that can profoundly affect clinical safety and efficacy. This places a high demand on analytical methods that afford comprehensive structural characterization of mAbs to ensure their stringent quality control. Here we report the use of targeted middle-down 193 nm ultraviolet photodissociation (UVPD) to provide detailed primary sequence analysis and PTM site localization of therapeutic monoclonal antibody subunits (∼25 kDa) generated upon digestion with recombinant immunoglobulin G-degrading enzyme of Streptococcus pyogenes (IdeS) followed by chemical reduction. Under optimal conditions, targeted UVPD resulted in approximately 60% overall coverage of the IgG sequence, in addition to unambiguous glycosylation site localization and extensive coverage of the antigen-binding complementarity determining regions (CDRs) in a single LC-MS/MS experiment. Combining UVPD and ETD data afforded even deeper sequencing and greater overall characterization of IgG subunits. Overall, this targeted UVPD approach represents a promising new strategy for the comprehensive characterization of antibody-based therapeutics. PMID:26947921

  6. High-performance 193-nm photoresist materials based on a new class of polymers containing spaced ester finctionalities

    NASA Astrophysics Data System (ADS)

    Khojasteh, Mahmoud; Chen, K. Rex; Kwong, Ranee W.; Lawson, Margaret C.; Varanasi, Pushkara R.; Patel, Kaushal S.; Kobayashi, Eiichi

    2003-06-01

    ArF lithography has been selected as the imaging method for the 90 nm technology node. Manufacturing related issues will have to be addressed when designing advanced 193 nm resists that are production worthy. Post exposure bake (PEB) sensitivity, dissolution properties and process window are some issues that need continuous improvement. Initially our investigation focused on a cyclic olefin (CO) platform which led us to a better understanding of the relationship between polymer structure and physical properties and how to improve cyclic olefin resist performance. Since then we have developed a new class of acrylate polymers with pendant "spaced ester" functionality. We have investigated the potential use of "spaced ester" functionality on improving the lithographic performance of CO and acrylate resist platforms. We have found that with "spaced ester" as pending group in CO polymer structures, it can lower the Tg and improve the dissolution properties of the CO resists. Resists formulated with acrylate containing "spaced ester" group exhibit excellent PEB temperature sensitivity (1 nm/°C), and are soluble in PGMEA. In addition, we have demonstrated sub-100 nm resolution with excellent process window through formulation optimization for acrylate based resists. This paper will focus on the "spaced ester" based polymer design, material properties; resist characteristics, and the lithographic performance for logic dense line applications.

  7. Extension of 193 nm dry lithography to 45-nm half-pitch node: double exposure and double processing technique

    NASA Astrophysics Data System (ADS)

    Biswas, Abani M.; Li, Jianliang; Hiserote, Jay A.; Melvin, Lawrence S., III

    2006-10-01

    Immersion lithography and multiple exposure techniques are the most promising methods to extend lithography manufacturing to the 45nm node. Although immersion lithography has attracted much attention recently as a promising optical lithography extension, it will not solve all the problems at the 45-nm node. The 'dry' option, (i.e. double exposure/etch) which can be realized with standard processing practice, will extend 193-nm lithography to the end of the current industry roadmap. Double exposure/etch lithography is expensive in terms of cost, throughput time, and overlay registration accuracy. However, it is less challenging compared to other possible alternatives and has the ability to break through the κ I barrier (0.25). This process, in combination with attenuated PSM (att-PSM) mask, is a good imaging solution that can reach, and most likely go beyond, the 45-nm node. Mask making requirements in a double exposure scheme will be reduced significantly. This can be appreciated by the fact that the separation of tightly-pitched mask into two less demanding pitch patterns will reduce the stringent specifications for each mask. In this study, modeling of double exposure lithography (DEL) with att-PSM masks to target 45-nm node is described. In addition, mask separation and implementation issues of optical proximity corrections (OPC) to improve process window are studied. To understand the impact of OPC on the process window, Fourier analysis of the masks has been carried out as well.

  8. Analyzing velocity map images to distinguish the primary methyl photofragments from those produced upon C-Cl bond photofission in chloroacetone at 193 nm

    SciTech Connect

    Alligood, Bridget W.; Straus, Daniel B.; Butler, Laurie J.

    2011-07-21

    We use a combination of crossed laser-molecular beam scattering experiments and velocity map imaging experiments to investigate the three primary photodissociation channels of chloroacetone at 193 nm: C-Cl bond photofission yielding CH{sub 3}C(O)CH{sub 2} radicals, C-C bond photofission yielding CH{sub 3}CO and CH{sub 2}Cl products, and C-CH{sub 3} bond photofission resulting in CH{sub 3} and C(O)CH{sub 2}Cl products. Improved analysis of data previously reported by our group quantitatively identifies the contribution of this latter photodissociation channel. We introduce a forward convolution procedure to identify the portion of the signal, derived from the methyl image, which results from a two-step process in which C-Cl bond photofission is followed by the dissociation of the vibrationally excited CH{sub 3}C(O)CH{sub 2} radicals to CH{sub 3}+ COCH{sub 2}. Subtracting this from the total methyl signal identifies the methyl photofragments that result from the CH{sub 3}+ C(O)CH{sub 2}Cl photofission channel. We find that about 89% of the chloroacetone molecules undergo C-Cl bond photofission to yield CH{sub 3}C(O)CH{sub 2} and Cl products; approximately 8% result in C-C bond photofission to yield CH{sub 3}CO and CH{sub 2}Cl products, and the remaining 2.6% undergo C-CH{sub 3} bond photofission to yield CH{sub 3} and C(O)CH{sub 2}Cl products.

  9. Time-resolved diagnostics of excimer laser-generated ablation plasmas used for pulsed laser deposition

    SciTech Connect

    Geohegan, D.B.

    1994-09-01

    Characteristics of laser plasmas used for pulsed laser deposition (PLD) of thin films are examined with four in situ diagnostic techniques: Optical emission spectroscopy, optical absorption spectroscopy, ion probe studies, and gated ICCD (intensified charge-coupled-device array) fast photography. These four techniques are complementary and permit simultaneous views of the transport of ions, excited states, ground state neutrals and ions, and hot particulates following KrF laser ablation of YBCO, BN, graphite and Si in vacuum and background gases. The implementation and advantages of the four techniques are first described in order to introduce the key features of laser plasmas for pulsed laser deposition. Aspects of the interaction of the ablation plume with background gases (i.e., thermalization, attenuation, shock formation) and the collision of the plasma plume with the substrate heater are then summarized. The techniques of fast ICCD photography and gated photon counting are then applied to investigate the temperature, velocity, and spatial distribution of hot particles generated during KrF ablation of YBCO, BN, Si and graphite. Finally, key features of fast imaging of the laser ablation of graphite into high pressure rare gases are presented in order to elucidate internal reflected shocks within the plume, redeposition of material on a surface, and formation of hot nanoparticles within the plume.

  10. Excimer laser annealing to fabricate low cost solar cells. Quarterly technical report No. 1, 26 March-30 June 1984

    SciTech Connect

    Not Available

    1984-07-01

    The objective of this research is to show whether or not pulsed excimer laser annealing (PELA) of ion-implanted junctions is a cost effective replacement for diffused junctions in fabricating crystalline silicon solar cells. The preliminary economic analysis completed during the first quarter of this program shows that the use of PELA to fabricate both the front junction and back surface field (BSF) would cost approximately 35 cents per peak watt (Wp), compared to a cost of 15 cents/Wp for diffusion, aluminum BSF and an extra cleaning step in the baseline process described by JPL. The cost advantage of the PELA process depends on improving the average cell efficiency from 14% to 16%, which would lower the overall cost of the module by about 15 cents/Wp. The technical goal of this research is to develop an optimized PELA process compatible with commercial production, and to demonstrate increased cell efficiency with sufficient product for adequate statistical analysis. During the first quarter of this program an excimer laser annealing station was set-up and made operational. The first experiment used 248 nm radiation to anneal phosphorus implants in polished and texture-etched silicon. Preliminary results showed that the PELA processed cells had overall efficiencies comparable to furnace annealed ion implanted controls, and that texture-etched material requires lower fluence for annealing than polished silicon. Process optimization will be carried out in the second quarter.

  11. How predictable are the results of excimer laser photorefractive keratectomy? A review.

    PubMed

    Grosvenor, T

    1995-10-01

    At the close of 1994, the AOA News reported that at least 14 companies were preparing to market equipment for excimer laser photorefractive keratectomy (PRK). More than a dozen PRK centers had been formed for the purpose of recruiting optometrists to co-manage PRK patients. Because the surgery is a "no-touch" computer-driven procedure whose duration is measured in seconds, the preoperative and postoperative care of PRK patients will assume major importance. Optometrists who will be asked to take part in the management of PRK patients must be able to counsel patients on matters such as the predictability of the procedure in terms of postoperative refractive error and visual acuity, as well as the possibility of unintended consequences such as difficulty in night driving. Information currently available, mainly as a result of studies conducted in other countries, shows that the results of PRK are highly predictable for preoperative myopia up to about -3.00 D and somewhat less predictable for myopia between -3.00 and -6.00 D, whereas for myopia greater than -6.00 D the probability of achieving a full correction decreases rapidly with increasing amounts of myopia. As compared to radial keratotomy (RK) in which the postoperative refractive error drifts relentlessly in the hyperopic direction, PRK brings about an initial hyperopic shift followed by regression leading to increasing myopia. Researchers disagree on the cause of the postoperative hyperopic shift and regression, and on the value of various methods of controlling regression including the use of wider and deeper ablation profiles and the postoperative use of corticosteroids and nonsteroid anti-inflammatory drugs. It is too early to determine whether the myopic creep in PRK will be as persistent as the hyperopic creep in RK, but it is likely that whereas presbyopic post-RK patients may have adequate distance vision but require corrective lenses for reading, presbyopic post-PRK patients may be sufficiently myopic

  12. Effect of laser radiation wavelength and reepithelization process on optical quality of eye cornea after laser correction of vision

    NASA Astrophysics Data System (ADS)

    Kitai, M. S.; Semchishen, A. V.; Semchishen, V. A.

    2015-10-01

    The optical quality of the eye cornea surface after performing the laser vision correction essentially depends on the characteristic roughness scale (CRS) of the ablated surface, which is mainly determined by the absorption coefficient of the cornea at the laser wavelength. Thus, in the case of using an excimer ArF laser (λ = 193 nm) the absorption coefficient is equal to 39000 cm-1, the darkening by the dissociation products takes place, and the depth of the roughness relief can be as large as 0.23 mm. Under irradiation with the Er : YAG laser (λ = 2940 nm) the clearing is observed due to the rupture of hydrogen bonds in water, and the relief depth exceeds 1 μm. It is shown that the process of reepithelization that occurs after performing the laser vision correction leads to the improvement of the optical quality of the cornea surface.

  13. Excimer lamp stereolithography

    NASA Astrophysics Data System (ADS)

    Satoh, Saburoh; Tanaka, Takao; Ihara, Satoshi; Yamabe, Chobei

    2000-06-01

    For the laser stereo-lithography, a XeCl excimer lamp with cylindrical tube has been adopted to achieve a lower cost type UV light source. Because of excellent high output efficiency, it is possible to be down sizing of a power supplier and a lamp head and to be air-cooling. And moreover to extract the maximum output power and efficiency, we applied an optical fiber system for its lithography optics. With this excimer lamp the maximum UV emission per pulse 25 (mu) J at 100 Hz and the maximum average power 10 mW at 1000 Hz were obtained.

  14. Study on the surface chemical properties of UV excimer laser irradiated polyamide by XPS, ToF-SIMS and CFM

    NASA Astrophysics Data System (ADS)

    Yip, Joanne; Chan, Kwong; Sin, Kwan Moon; Lau, Kai Shui

    2003-01-01

    Polyamide (nylon 6) was irradiated by a pulsed ultraviolet (UV) excimer laser with a fluence below its ablation threshold. Chemical modifications on laser treated nylon were studied by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (Tof-SIMS) and chemical force microscopy (CFM). XPS study provides information about changes in chemical composition and the chemical-state of atom types on the fiber surface. The high sensitivity of ToF-SIMS to the topmost layers was used to detect crosslinking after the laser treatment. Gold-coated AFM tips modified with COOH terminated self-assembled alkanethiol monolayers (SAMs) were used to measure adhesion forces on the untreated and laser treated samples. XPS results revealed that the irradiated samples have higher oxygen content than prior to laser irradiation. Tof-SIMS analysis illustrated that carbonyl groups in nylon 6 decrease significantly but hydroxyl groups increase after low-fluence laser irradiation. The adhesion force measurements by CFM showed spatial distribution of hydroxyl groups on nylon 6 after the laser treatment.

  15. AFM study of excimer laser patterning of block-copolymer: Creation of ordered hierarchical, hybrid, or recessed structures

    NASA Astrophysics Data System (ADS)

    Švanda, Jan; Siegel, Jakub; Švorčík, Vaclav; Lyutakov, Oleksiy

    2016-05-01

    We report fabrication of the varied range of hierarchical structures by combining bottom-up self-assembly of block copolymer poly(styrene-block-vinylpyridine) (PS-b-P4VP) with top-down excimer laser patterning method. Different procedures were tested, where laser treatment was applied before phase separation and after phase separation or phase separation and surface reconstruction. Laser treatment was performed using either polarized laser light with the aim to create periodical pattern on polymer surface or non-polarized light for preferential removing of polystyrene (PS) part from PS-b-P4VP. Additionally, dye was introduced into one part of block copolymer (P4VP) with the aim to modify its response to laser light. Resulting structures were analyzed by XPS, UV-vis and AFM techniques. Application of polarized laser light leads to creation of structures with hierarchical, recessed or hybrid geometries. Non-polarized laser beam allows pronouncing the block copolymer phase separated structure. Tuning the order of steps or individual step conditions enables the efficient reorientation of block-copolymer domain at large scale, fabrication of hierarchical, hybrid or recessed structures. The obtained structures can find potential applications in nanotechnology, photonics, plasmonics, information storage, optical devices, sensors and smart surfaces.

  16. Single pulse vibrational Raman scattering by a broadband KrF excimer laser in a hydrogen-air flame.

    PubMed

    Pitz, R W; Wehrmeyer, J A; Bowling, J M; Cheng, T S

    1990-05-20

    Spontaneous vibrational Raman scattering (VRS) is produced by a broadband excimer laser at 248 nm (KrF) in a H(2)-air flame and VRS spectra are recorded for lean, stoichiometric, and rich flames. Except at very lean flame conditions, laser-induced fluorescence (LIF) processes interfere with VRS Stokes lines from H(2), H(2)O, and O(2). No interference is found for the N(2) Stokes and N(2) anti-Stokes lines. In a stoichiometric H(2)/air flame, single-pulse measurements of N(2) concentration and temperature (by the VRS Stokes to anti-Stokes ratio) have relative standard deviation of 7.7 and 10%, respectively. These single pulse measurement errors compare well with photon statistics calculations using measured Raman cross sections. PMID:20563170

  17. An open label pilot study of supraerythemogenic excimer laser in combination with clobetasol spray and calcitriol ointment for the treatment of generalized plaque psoriasis.

    PubMed

    Levin, Ethan; Nguyen, Catherine M; Danesh, Melissa J; Beroukhim, Kourosh; Leon, Argentina; Koo, John

    2016-06-01

    A common therapeutic modality for psoriasis includes the combination of phototherapy with topical treatments. The recent development of targeted phototherapy with the excimer laser and spray formulations for topical treatments has increased the efficacy and convenience of these combinational therapies. Herein, we aim to assess the efficacy of a novel combination of therapies using the 308 nm excimer laser, clobetasol propionate spray and calcitriol ointment for the treatment of moderate to severe generalized psoriasis. In this 12-week study, patients with moderate to severe psoriasis received twice weekly treatments with a 308-nm excimer laser combined with clobetasol proprionate twice daily for a month followed by calcitriol ointment twice daily for the next month. Of the 30 patients enrolled, 83% of patients (25/30) achieved PASI-75 [65-94%, 95% confidence interval (CI)] at week 12. For PGA, there was an estimated decrease of 3.6 points (3.1-4.1, 95% CI, p < 0.0005) by week 12. In conclusion, the combination of excimer laser with alternating clobetasol and calcitriol application has shown to be a promising combination of therapies for the treatment of moderate to severe generalized psoriasis. Further evaluation may be conducted with a larger study inclusive of control groups and head-to-head comparisons against topical steroid and UVB therapy as monotherapies. PMID:26329774

  18. Percutaneous coronary excimer laser angioplasty in patients with stable and unstable angina pectoris. Acute results and incidence of restenosis during 6-month follow-up.

    PubMed

    Karsch, K R; Haase, K K; Voelker, W; Baumbach, A; Mauser, M; Seipel, L

    1990-06-01

    A clinical study was conducted to evaluate the efficacy and safety of percutaneous coronary excimer laser angioplasty in 60 patients with coronary artery disease. Forty-nine patients had stable exertional angina, and 11 patients had unstable angina despite medical therapy. A novel 1.4-mm diameter catheter with 20 quartz fibers of 100-microns diameter each arranged concentrically around a central lumen suitable for a 0.014-in. flexible guide wire was coupled to an excimer laser. A commercial excimer laser emitting energy at a wavelength of 308 nm with a pulse duration of 60 nsec was used. The laser was operated at 20 Hz. Mean energy transmission was 30 +/- 5 mJ/mm2. In five of the 60 patients, laser angioplasty was not attempted. In 23 patients with laser ablation alone, percent stenosis decreased from 76 +/- 14% before to 27 +/- 17% after ablation and was 34 +/- 15% at the early follow-up angiogram. In 32 patients, additional balloon angioplasty was performed because of vessel closure after laser ablation in 11 and an insufficient qualitative result in 21 patients. Of the 11 patients with unstable angina, one patient died due to vessel closure 3 hours after intervention, and two patients developed a myocardial infarction. In 22 of 47 patients with late follow-up angiography, restenosis within the 6-month follow-up period occurred. Rate of restenosis was higher in patients treated with laser ablation and balloon angioplasty (16 of 28) than in patients treated with laser ablation alone (six of 19). These results suggest that coronary excimer laser angioplasty for ablation of obstructive lesions is feasible and safe in patients with stable angina. However, development of new catheter systems is necessary for an improved success rate. PMID:2344680

  19. Ablation of hard dental tissues with an ArF-pulsed excimer laser

    NASA Astrophysics Data System (ADS)

    Neev, Joseph; Raney, Daniel; Whalen, William E.; Fujishige, Jack T.; Ho, Peter D.; McGrann, John V.; Berns, Michael W.

    1991-06-01

    The interaction of 15 ns pulses from an ArF excimer laser with hard dental tissue was investigated for the purpose of obtaining practical information on the ablation process. Dark field fast photography utilizing an auxiliary, 15 ns Nd:Yag laser 'probe', was used to study the ablation plume dynamics as a function of time, luminescence were studied at different fluence levels and prr. Dentin ablation was found to be about four times as efficient as ablation of enamel in the higher fluence levels tested (> 10 J/cm2) and about twice as efficient as the ablation in the lower fluence regime (approximately equals 1 J/cm2). The dentin etch depth per pulse was found to increase exponentially with fluence (at least up to the tested level of 11 J/cm2), while in enamel the etch depth per pulse appears to increase logarithmically with fluence. Dentin ablation yields a larger, more dense plume which can be ejected (depending on the fluence level) to a height of several millimeters above the surface with observed ejection velocity in access of 1200 m/s. The dentin plume consisted of a relatively uniform particle size distribution (0.1 micrometers to 10 micrometers in diameter). Enamel ablation, on the other hand, yields a smaller observed ejection velocities (about 800 m/s), and a much smaller plume of fine particles (about 0.1 micrometers in diameter) and gases, confined to within 0.5 mm of the surface. In addition, an even smaller amount of highly non-uniform debris, (from ten to several hundred micrometers in size) is observed to be ejected to higher levels, and reach roughly half the height of the corresponding dentin plume for similar fluence levels. Although both dentin and enamel yield lower ablation efficiencies at 1 Hz, no significant difference is detected between the ablation efficiency at 5 Hz and ablation 10 Hz prr. Both materials remained within 20 degree(s)C of room temperature even at fluences as high as 20 J/cm2 and prr as high as 10 Hz for enamel and 20 Hz for

  20. Species-resolved laser-probing investigations of the hydrodynamics of KrF excimer and copper vapor laser ablation processing of materials

    NASA Astrophysics Data System (ADS)

    Ventzek, Peter L. G.; Gilgenbach, Ronald M.; Ching, Chi H.; Lindley, R. A.

    1993-06-01

    Hydrodynamic phenomena from KrF excimer laser ablation (10-3-20 J/cm2) of polyimide, polyethyleneterephthalate, and aluminum are diagnosed by laser beam deflection, schlieren photography, shadowgraphy, laser-induced-fluorescence and dye-laser- resonance absorption photography (DLRAP). Experiments were performed in vacuum and gaseous environments (10-5 to 760 Torr). In vacuum, the DLRAP diagnostic shows species-resolved plume expansion which is consistent with that of a reflected rarefaction wave. Increasing the background gas pressure reveals the formation of sound/shock compared to CN in the laser-ablated polyimide (Vespel) plume/shock in inert (e.g. argon) and reactive (e.g. air) gases. At low pressures (less than 10 Torr) Al and CN species are in close contact with the shock front. As the pressure increases, the species front tends to recede, until at high pressures (over 200 Torr) the species are restrained to only a few mm above the target surface. After sufficient expansion, Al and CN are no longer detectable; only the shadowgraph of the hot gas plume remains. Since CN is observable in both inert and reactive environments, it can be concluded that CN is not a reaction product between the background gas and the ablated species. By way of comparison to excimer laser ablation processing of materials, copper vapor laser machined polyimide and polymethylmethacrylate (transparent to green and yellow copper vapor laser light) are also investigated. The two polymers are observed to have markedly different machined surfaces. Hydrodynamic effects for the copper vapor laser machined materials are investigated using HeNe laser beam deflection.

  1. Laser radiation at various wavelengths for decompression of intervertebral disk. Experimental observations on human autopsy specimens.

    PubMed

    Choy, D S; Altman, P A; Case, R B; Trokel, S L

    1991-06-01

    The interaction of laser radiation with the nucleus pulposus from autopsy specimens of human intervertebral disks was evaluated at different wavelengths (193 nm, 488 nm & 514 nm, 1064 nm, 1318 nm, 2150 nm, 2940 nm, and 10600 nm). A significant correlation of linear least squares fit of the mass ablated as a function of incident energy was found for all lasers used except the Excimer at 193 nm. The 2940-nm Erbium:YAG laser was most efficient in terms of mass of disk ablated per joule in the limited lower range where this wavelength was observed. At higher energy levels, the CO2 laser in the pulsed mode was most efficient. However, the Nd:YAG 1064-nm and 1318-nm lasers are currently best suited for percutaneous laser disk decompression because of the availability of usable waveguides. Carbonization of tissue with the more penetrating Nd:YAG 1064-nm laser increases the efficiency of tissue ablation and makes it comparable to the Nd:YAG 1318-nm laser. PMID:1904334

  2. Excimer laser in-situ keratomileusis (LASIK) under a corneal flap for myopia of 2 to 20 D.

    PubMed Central

    Salah, T; Waring, G O; el-Maghraby, A; Moadel, K; Grimm, S B

    1995-01-01

    BACKGROUND: We report the results of a recent technique of keratomileusis for myopia: excimer laser in-situ keratomileusis (LASIK). METHODS: We studied retrospectively 88 eyes of 63 patients that received LASIK with the Chiron Automated Corneal Shaper and the Summit OmniMed excimer laser under a hinged corneal flap without sutures. RESULTS: Mean follow-up was 5.2 months. Mean spherical equivalent of the manifest refraction before surgery was -8.24 diopters (D)(range -2.00 to -20.00 D). Mean spherical equivalent refraction after surgery was +0.22 D (SD, 1.42 D). Of 40 eyes with a baseline refraction from -2.00 to -6.00 D, 25 (63%) had a refraction within +/- 0.50 D and 37 eyes (93%) within +/-1.00 D. In 29 eyes with baseline refraction of -6.12 to -12.00 D, postoperative refraction was within +/-1.00 D in 19 (65%). In 19 eyes with baseline refraction of -12.10 to -20.00 D postoperative refraction was +/-1.00 D in 8 (43%). Overall, 64 of 88 eyes (72.8%) had a refraction within +/-1.00 D after surgery. Between three weeks and five months after surgery the change in the mean spherical equivalent refraction was -0.61 D in the myopic direction. Uncorrected visual acuity after surgery was 20/20 or better in 31 eyes (36%) and 20/40 or better in 61 eyes (71%). Three eyes (3.6%) lost two lines or more of spectacle corrected visual acuity, two from progressive myopic maculopathy and one from irregular astigmatism. No eyes had vision threatening complications. CONCLUSION: Excimer laser in-situ keratomileusis (LASIK) under a corneal flap can be an effective method of reducing myopia between -2.00 to -20.00 D, with minimal complications. Current surgical algorithms need modification to improve predictability. Stability of refraction after surgery requires further study. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6 PMID:8719677

  3. KrF- and ArF-excimer-laser-induced absorption in silica glasses produced by melting synthetic silica powder

    SciTech Connect

    Kuzuu, Nobu; Sasaki, Toshiya; Kojima, Tatsuya; Tanaka, Jun-ichiro; Nakamura, Takayuki; Horikoshi, Hideharu

    2013-07-07

    KrF- and ArF-excimer-laser-induced absorption of silica glasses produced by electric melting and flame fusion of synthetic silica powder were investigated. The growth of KrF-laser-induced absorption was more gradual than that of ArF-laser-induced absorption. Induced absorption spectra exhibited a peak at about 5.8 eV, of which the position and width differed slightly among samples and laser species. Widths of ArF-laser-induced absorption spectra were wider than those of KrF-laser-induced spectra. KrF-laser-induced absorption is reproducible by two Gaussian absorption bands peaking at 5.80 eV with full width at half maximum (FWHM) of 0.62 eV and at 6.50 eV with FWHM of 0.74 eV. For reproduction of ArF-laser-induced absorption, Gaussian bands at 5.41 eV with FWHM of 0.62 eV was necessary in addition to components used for reproducing KrF-laser-induced absorption. Based on the discussion of the change of defect structures evaluated from change of absorption components, we proposed that the precursor of the 5.8-eV band ascribed to E Prime center ({identical_to}Si{center_dot}) is {identical_to}Si-H HO-Si{identical_to} structures formed by the reaction between strained Si-O-Si bonds and interstitial H{sub 2} molecules during the irradiation.

  4. Structural properties and impedance spectroscopy of excimer laser ablated Zr substituted BaTiO3 thin films

    NASA Astrophysics Data System (ADS)

    James, A. R.; Prakash, Chandra; Prasad, G.

    2006-04-01

    BaZr0.15Ti0.85O3 thin films were deposited on Pt-coated Si substrates using the pulsed excimer laser ablation technique. X-ray diffraction and atomic force microscope techniques were used to study the structural characteristics of the films. Films with good crystalline quality, with an average grain size of 0.5 µm were obtained, under various oxygen background pressures. Ferroelectric hysteresis loops recorded on the films deposited at 26.66 Pa oxygen pressure showed the best properties. To gain a further understanding of the electrical properties of these films, impedance spectroscopy was used and data acquired at several different temperatures. AC conductivity plots showed the presence of space charge conduction at low frequencies; however, at high frequencies, all the curves merged and expectedly showed an almost dc conduction behaviour. The activation energy obtained from ac conductivity data may be attributed to oxygen vacancy motion.

  5. High-performance p-channel polycrystalline-germanium thin-film transistors via excimer laser crystallization and counter doping

    NASA Astrophysics Data System (ADS)

    Liao, Chan-Yu; Huang, Ching-Yu; Huang, Ming-Hui; Chou, Chia-Hsin; Cheng, Huang-Chung

    2016-04-01

    High-quality polycrystalline-germanium (poly-Ge) thin films have been successfully fabricated by excimer laser crystallization (ELC). Grains as large as 1 µm were achieved by ELC at 300 mJ/cm2. Meanwhile, the defect-generated hole concentrations in Ge thin films were significantly reduced. Furthermore, the majority carriers could then be converted to n-type by counter doping (CD) with a suitable dose. Then, high-performance p-channel Ge thin-film transistors (TFTs) with a high on/off current ratio of up to 1.7 × 103 and a high field-effect mobility of up to 208 cm2 V-1 s-1 were demonstrated for a channel width and length both of 0.5 µm. It was revealed that ELC combined with CD is effective for attaining high-performance p-channel poly-Ge TFTs.

  6. Short-wavelength stimulated raman scattering in a silica fiber pumped by an XeBr excimer laser

    SciTech Connect

    Mizunami, T.; Takagi, K.

    1989-08-01

    A UV-grade silica optical fiber was pumped by a 281.8 nm XeBr excimer laser. The first Stokes spectrum was observed at 285 nm. The spectral width was one half of that of the spontaneous Raman spectrum. A numerical analysis of stimulated Raman scattering which includes two-photon absorption loss is presented. The Raman-gain coefficient was determined by the analysis of observed nonlinearity in Stokes output and was found to be 1.8 x 10/sup -5/ cm/MW. It was also shown that two-photon absorption is a more important loss factor than linear attenuation. The shortest limit of wavelength for amplification by stimulated Raman scattering is also discussed.

  7. A novel approach to pseudopodia proteomics: excimer laser etching, two-dimensional difference gel electrophoresis, and confocal imaging

    PubMed Central

    Mimae, Takahiro; Ito, Akihiko; Hagiyama, Man; Nakanishi, Jun; Hosokawa, Yoichiroh; Okada, Morihito; Murakami, Yoshinori; Kondo, Tadashi

    2014-01-01

    Pseudopodia are actin-rich ventral cellular protrusions shown to facilitate the migration and metastasis of tumor cells. Here, we present a novel approach to perform pseudopodia proteomics. Tumor cells growing on porous membranes extend pseudopodia into the membrane pores. In our method, cell bodies are removed by horizontal ablation at the basal cell surface with the excimer laser while pseudopodia are left in the membrane pores. For protein expression profiling, whole cell and pseudopodia proteins are extracted with a lysis buffer, labeled with highly sensitive fluorescent dyes, and separated by two-dimensional gel electrophoresis. Proteins with unique expression patterns in pseudopodia are identified by mass spectrometry. The effects of the identified proteins on pseudopodia formation are evaluated by measuring the pseudopodia length in cancer cells with genetically modified expression of target proteins using confocal imaging. This protocol allows global identification of pseudopodia proteins and evaluation of their functional significance in pseudopodia formation within one month. PMID:25309719

  8. Electronic and crystalline structure of Si/SiO 2 interface modified by ArF excimer laser

    NASA Astrophysics Data System (ADS)

    Cháb, V.; Lukeš, I.; Ondřejček, M.; Jiříček, P.

    The native oxide layers on Si(100) surface were irradiated under UHV conditions by an ArF excimer laser pulses with energy density varied between melting and evaporating thresholds. The resulting changes were studied by LEED, AES and UPS. The increase of the energy density up to evaporation threshold results in the recrystallisation of native oxide layer. The pulses with energy densities just above the evaporation threshold ablate the top layer leaving an ordered and atomicaly clean surface. The observed (1x1) surface reconstruction is probably stabilised by strains introduced during rapid melting and quenching of the topmost layers. The surface electronic structure is dominated by random satisfaction of dangling bonds swearing a well defined surface states observed on (2x1)Si(100) surface.

  9. Keratin film ablation for the fabrication of brick and mortar skin structure using femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Haq, Bibi Safia; Khan, Hidayat Ullah; Dou, Yuehua; Alam, Khan; Attaullah, Shehnaz; Zari, Islam

    2015-09-01

    The patterning of thin keratin films has been explored to manufacture model skin surfaces based on the "bricks and mortar" view of the relationship between keratin and lipids. It has been demonstrated that laser light is capable of preparing keratin-based "bricks and mortar" wall structure as in epidermis, the outermost layer of the human skin. "Bricks and mortar" pattern in keratin films has been fabricated using an ArF excimer laser (193 nm wavelength) and femtosecond laser (800 and 400 nm wavelength). Due to the very low ablation threshold of keratin, femtosecond laser systems are practical for laser processing of proteins. These model skin structures are fabricated for the first time that will help to produce potentially effective moisturizing products for the protection of skin from dryness, diseases and wrinkles.

  10. Magnetic and crystallographic properties of Co-Cr-(Ta,Pt)/Cr films deposited by excimer laser ablation

    NASA Astrophysics Data System (ADS)

    Ishikawa, A.; Tanahashi, K.; Yahisa, Y.; Hosoe, Y.; Shiroishi, Y.

    1994-05-01

    The crystal structure and magnetic properties of Co-alloy films deposited by KrF excimer laser ablation were investigated. A pulsed laser beam with wavelength of 248 nm was focused onto the deposition targets which were fixed in the vacuum chamber. Cr underlayer and Co-alloy films were successively deposited at a rate of 0.012 nm/pulse. The film surface was microscopically smooth compared to the sputtered films. This may be due to the low shadowing effect during the laser deposition. The composition of the film was reproducibly controlled, though there was a slight difference between the composition of film and target material. The coercivities of Co-Cr-Pt/Cr films formed on the Si and Ni-P substrates at 250 °C were 130 and 220 Oe, which were about one-fifth of the coercivity of sputtered films. Crystallographic analyses showed that Cr underlayer had no crystal orientation, and Co-alloy film consisted of fine fcc-type crystal grains. Low coercivity of the laser-deposited film is probably due to the lack of hcp Co phase.

  11. Surface studies on benzophenone doped PDMS microstructures fabricated using KrF excimer laser direct write lithography

    NASA Astrophysics Data System (ADS)

    Kant, Madhushree Bute; Shinde, Shashikant D.; Bodas, Dhananjay; Patil, K. R.; Sathe, V. G.; Adhi, K. P.; Gosavi, S. W.

    2014-09-01

    This paper discusses microfabrication process for benzophenone doped polydimethylsiloxane (PDMS) using laser lithography. KrF excimer laser of 248 nm with 20 ns pulse width at repetition rate of 1 Hz was used for microfabrication of undoped and benzophenone doped PDMS. The doped-PDMS shows sensitivity below 365 nm, permitting processing under ambient light. The analysis of etch depth revealed that doped PDMS shows self developable sensitivity at lower fluence of ∼250 mJ/cm2. The unexposed and exposed surface was studied using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and Scanning electron microscopy (SEM). Spectrocopic analysis indicated increase in Csbnd O, Cdbnd O, Sisbnd O3 and Sisbnd O4 bonding at the expense of Sisbnd C and Sisbnd O2 bonds of PDMS. In case of laser exposed doped-PDMS, removal of benzophenone from probe depth of spectroscopy was observed. Whereas the surface morphology of exposed and unexposed doped-PDMS was observed to be same, indicating clean development of PDMS micropatterns. The present study indicates that addition of 3.0 wt.% benzophenone in PDMS enhance self development sensitivity of PDMS. The self developable results on doped-PDMS are quite encouraging for its potential use in point of care Lab-On-Chip applications, for fabricating micropatterns using direct write laser lithography technology.

  12. Electron collisions with cesium atoms - benchmark calculations and application to modeling an excimer-pumped alkali laser

    NASA Astrophysics Data System (ADS)

    Zatsarinny, Oleg; Bartschat, Klaus; Babaeva, Natalia; Kushner, Mark

    2014-10-01

    The B-spline R-matrix (BSR) with pseudostates method was employed to describe electron collisions with cesium atoms. Over 300 states were kept in the close-coupling expansion, including a large number of pseudostates to model the effect of the Rydberg spectrum and the ionization continuum on the results for transitions between the discrete physical states of interest. Predictions for elastic scattering, excitation, and ionization for incident energies up to 200 eV are presented and compared to previous results [2,3] and experimental data. Our data were used to model plasma formation in the excimer-pumped alkali laser, XPAL, operating on the Cs (62P3 / 2 , 1 / 2 --> (62S1 / 2) (852nm and 894nm) transitions. At sufficiently high operating temperature, pump power, and repetition rate, plasma formation in excess of 1014--1015cm-3 occurs. This may reduce laser output power by electron collisional mixing of the upper and lower laser levels. Work supported by the NSF under PHY-1068140, PHY-1212450, and the XSEDE allocation PHY-090031 (OZ, KB), and by the DoD High Energy Laser Multidisciplinary Research Initiative (NYB, MJK).

  13. Rapid fabrication of rigid biodegradable scaffolds by excimer laser mask projection technique: a comparison between 248 and 308 nm

    NASA Astrophysics Data System (ADS)

    Beke, S.; Anjum, F.; Ceseracciu, L.; Romano, I.; Athanassiou, A.; Diaspro, A.; Brandi, F.

    2013-03-01

    High-resolution photocrosslinking of the biodegradable poly(propylene fumarate) (PPF) and diethyl fumarate (DEF), using pulsed laser light at 248 and 308 nm is presented. The curing depth can be modulated between a few hundreds of nm and a few μm when using 248 nm and ten to a hundred μm when using 308 nm. By adjusting the total fluence (pulse numbers×laser fluence) dose and the weight ratios of PPF, DEF, and the photoinitiator in the photocrosslinkable mixtures, the height of polymerized structures can be precisely tuned. The lateral resolution is evaluated by projecting a pattern of a grid with a specified line width and line spacing. Young’s modulus of the cured parts is measured and found to be several GPa for both wavelengths, high enough to support bone formation. Several 2D and 2.5D microstructures, as well as porous 3D scaffolds fabricated by a layer-by-layer method, are presented. The results demonstrate that excimer laser-based photocuring is suitable for the fabrication of stiff and biocompatible structures with defined patterns of micrometer resolution in all three spatial dimensions.

  14. Electron collisions with cesium atoms—benchmark calculations and application to modeling an excimer-pumped alkali laser

    NASA Astrophysics Data System (ADS)

    Zatsarinny, Oleg; Bartschat, Klaus; Babaeva, Natalia Yu; Kushner, Mark J.

    2014-06-01

    The B-spline R-matrix (BSR) with pseudostates method is employed to describe electron collisions with cesium atoms. Over 300 states are kept in the close-coupling expansion, including a large number of pseudostates to model the effect of the Rydberg spectrum and, most importantly, the ionization continuum on the results for transitions between the discrete physical states of interest. Predictions for elastic scattering, momentum transfer, excitation and ionization are presented for incident energies up to 200 eV and compared with results from previous calculations and available experimental data. In a second step, the results are used to model plasma formation in an excimer-pumped alkali laser operating on the Cs (62P3/2,1/2 → 62S1/2) (852 nm and 894 nm) transitions. At sufficiently high operating temperature of a Cs-Ar containing quartz cell, pump power, and repetition rate, plasma formation in excess of 1014-1015 cm-3 occurs. This may reduce laser output power by electron collisional mixing of the upper and lower laser levels.

  15. Stimulated Raman scattering in lead vapor heat pipe for tunable and narrow-linewidth XeCl excimer laser

    SciTech Connect

    Rieger, H.

    1989-05-01

    Narrow-linewidth and high-efficiency conversion of stimulated Raman scattering (SRS) in a lead vapor heat pipe was observed using a narrow-linewidth and injection-locked XeCl excimer laser system as the pump source. The XeCl laser was continuously tuned over its entire B-X gain curve, from the (0-0) transition to the (0-3) transition, giving it a range of 0.8 nm (307.65-308.45 nm). The laser linewidth was narrowed down to 0.002 A (0.02 cm/sup -1/). The output energy was 310 mJ/pulse, with a repetition rate up to 50 pps and good beam quality. A lead vapor heat pipe operating at 1225/sup 0/C was used as a single-pass stimulated Raman converter, shifting the radiation from 308 to 459 nm. Photon conversion efficiency as high as 80 percent was achieved, using a pump linewidth of 0.01 A.

  16. Investigation of the utility of laser-secondary neutral mass spectrometry for the detection of polyaromatic hydrocarbons in individual atmospheric aerosol particles.

    PubMed

    Tyler, Bonnie J; Dambach, Steffen; Galla, Sebastian; Peterson, Richard E; Arlinghaus, Heinrich F

    2012-01-01

    The distribution of polyaromatic hydrocarbons (PAHs) in ambient aerosol particles is of importance to both human health and climate forcing. Although time-of-flight secondary ion mass spectrometry (ToF-SIMS) has proven useful for studying the distribution of organic compounds in individual aerosol particles, it is difficult to detect PAHs at relevant concentrations in individual aerosol particles because of their low ion yield. In this study, we explore the potential of using laser secondary neutral mass spectrometry (Laser-SNMS) to study three PAHs: pyrene, anthracene, and naphthalene. Because of the high volatility of PAHs, a cryostage was required for the analysis to prevent sublimation of the molecules into the vacuum chamber. We studied two laser systems, a 157 nm excimer laser, which is capable of single-photon ionization of the PAHs, and a 193 nm laser, which requires multiphoton ionization. Under optimized conditions for laser power density and primary ion pulse length, 193 nm postionization resulted in a 2-50-fold increase in ion yield over ToF-SIMS. Using the 157 nm laser, the yield was increased by more than 3 orders of magnitude for all 3 PAHs studied. The single-photon postionization process proved superior in terms of both yield enhancement and reduced fragmentation. By using the optimized 157 nm laser system and a cryostage, we were able to detect PAHs on the surface of 2 μm diameter ambient aerosol particles. PMID:21823569

  17. Topography and raytracing analysis of patients with excellent visual acuity 3 months after excimer laser photorefractive keratectomy for myopia.

    PubMed

    Maguire, L J; Zabel, R W; Parker, P; Lindstrom, R L

    1991-01-01

    We performed topography and raytracing analysis 3 months after surgery on five consecutive eyes of five patients, which had excimer laser photorefractive keratectomy for myopia. Three of the five eyes had uncorrected postoperative visual acuity of 20/20 or better. Two eyes had an uncorrected vision of 20/40. In three of five eyes, the area of excimer ablation was centered within 1.0 mm of the optical axis. Three other eyes showed decentration that ranged from 1.1 to 1.5 mm. The range of surface power seen within 2 mm of the central keratoscope ring was as follows: patient CK = 37.50 to 39.50 diopters; patient CA = 40.50 D to 44.80 D; patient CW = 37.90 D to 42.20 D; patient AC = 35.50 D to 39.00 D; patient DT = 34.50 D to 41.40 D. Topography patterns differed from eye to eye. A raytracing program modeled refraction of 20/80 and 20/20 "E" of 100%, 50%, 25%, 12.5% and 6.25% contrast through all measured points on the central 10 keratoscope rings of the five postoperative corneas. The five computer-derived images were ranked subjectively according to the observed degree of image degradation by three observers. Two eyes showed discernible 20/20 E's even at the 12.5% contrast level. Little to no ghost image was seen. Two eyes showed degraded but discernible 20/20 letters at higher levels of contrast only. These eyes showed moderate ghost images that were most apparent in the high-contrast 20/80 letters. One eye showed poor resolution of the 100% contrast 20/20 letter and moderately severe ghost images.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2043557

  18. Development of a Silicon Based Electron Beam Transmission Window for Use in a KrF Excimer Laser System

    SciTech Connect

    C.A. Gentile; H.M. Fan; J.W. Hartfield; R.J. Hawryluk; F. Hegeler; P.J. Heitzenroeder; C.H. Jun; L.P. Ku; P.H. LaMarche; M.C. Myers; J.J. Parker; R.F. Parsells; M. Payen; S. Raftopoulos; J.D. Sethian

    2002-11-21

    The Princeton Plasma Physics Laboratory (PPPL), in collaboration with the Naval Research Laboratory (NRL), is currently investigating various novel materials (single crystal silicon, <100>, <110> and <111>) for use as electron-beam transmission windows in a KrF excimer laser system. The primary function of the window is to isolate the active medium (excimer gas) from the excitation mechanism (field-emission diodes). Chosen window geometry must accommodate electron energy transfer greater than 80% (750 keV), while maintaining structural integrity during mechanical load (1.3 to 2.0 atm base pressure differential, approximate 0.5 atm cyclic pressure amplitude, 5 Hz repetition rate) and thermal load across the entire hibachi area (approximate 0.9 W {center_dot} cm superscript ''-2''). In addition, the window must be chemically resistant to attack by fluorine free-radicals (hydrofluoric acid, secondary). In accordance with these structural, functional, and operational parameters, a 22.4 mm square silicon prototype window, coated with 500 nm thin-film silicon nitride (Si{sub 3}N{sub 4}), has been fabricated. The window consists of 81 square panes with a thickness of 0.019 mm {+-} 0.001 mm. Stiffened (orthogonal) sections are 0.065 mm in width and 0.500 mm thick (approximate). Appended drawing (Figure 1) depicts the window configuration. Assessment of silicon (and silicon nitride) material properties and CAD modeling and analysis of the window design suggest that silicon may be a viable solution to inherent parameters and constraints.

  19. Optical Emission Spectroscopy of the Laser Ablation Plume Controled by RF Plasma

    NASA Astrophysics Data System (ADS)

    Suda, Yoshiyuki; Nishimura, Takuma; Mizuno, Manabu; Bratescu, Maria Antoaneta; Sakai, Yosuke

    1999-10-01

    Recently, film deposition has been investigated using laser ablation methods which have a lot of advantages. For the purpose of control of the laser ablation plume, we introduced a radio frequency (RF) plasma. In this report we present position resolved optical emission spectra of the plume observed by an OMA (optical multichannel analyzer). The plume current is also measured. The RF plasma is generated in a helical coil installed between the substrate and the target. An ArF excimer laser (wavelength 193 nm, pulse duration time 20 ns) is used as a light source, and the target material is sintered carbon graphite. The laser fluence on the target surface is changed in a range from 1.2 to 6.4 J/cm^2. Ar gas is introduced to sustain the RF plasma. When the plume goes through the RF plasma, interaction of the plume with the plasma is expected. The possibility of control of the plume behavior is discussed.

  20. A New Approach of Polycrystalline Silicon Film on Plastic Substrate Prepared by Ion Beam Deposition Followed by Excimer Laser Crystallization at Room Temperature

    NASA Astrophysics Data System (ADS)

    Kwon, Jang Yeon; Lim, Hyuck; Park, Kyung Bae; Jung, Ji Sim; Kim, Do Young; Cho, Hans S.; Kim, Seok Pil; Park, Young Soo; Kim, Jong Man; Noguchi, Takashi

    2006-05-01

    In this work, we propose a new polycrystalline silicon (poly-Si) film of large grain for thin film transistor on flexible substrate. Thin films of amorphous silicon were deposited on plastic substrate by using ion beam deposition (IBD) and crystallized by excimer laser annealing. The entire process was carried out at room temperature. Si film formed by IBD has much lower impurity such as Ar, O, and H than that deposited by conventional sputtering method. This high purity of Si film makes large grain size (0.5 μm) and shows high endurance of excimer laser energy both on quartz and plastic substrate for flexible active matrix organic light emitting diode (AMOLED).

  1. The acute phase of inflammatory response involved in the wound-healing process after excimer laser treatment

    PubMed Central

    Resan, Mirko; Vukosavljevic, Miroslav; Vojvodic, Danilo; Pajic-Eggspuehler, Brigitte; Pajic, Bojan

    2016-01-01

    Purpose To evaluate the participation of proinflammatory cytokines in the acute phase of corneal wound-healing response after excimer laser treatment. Methods The study included 68 myopic eyes up to −3.0 diopters divided into two groups: 1) eyes treated with laser in situ keratomileusis (LASIK) (n=31) and 2) eyes treated with photorefractive keratectomy (PRK) (n=37). Each group was then divided into three subgroups based on tear sampling times: before (0 hours), 1 hour after, and 24 hours after treatment. The tear fluid was sampled from lower lateral tear meniscus using a cellulose microsurgical sponge. The levels of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-6, and IL-8 in tear fluid were determined by flow cytometry method. Results Statistical significance was observed in the concentrations of TNF-α (P=0.0421) and IL-1β (P=0.0225) between samples collected 1 and 24 hours after PRK treatment in favor of samples collected 1 hour after treatment. IL-6 concentration changes showed a significant increase in the PRK group in both time intervals following treatment compared to pretreatment (0 hour/1 hour, P=0.0031; 0 hour/24 hours, P=0.0059). For IL-8 concentrations, significant differences were observed between control and experimental groups in samples collected 1 hour after LASIK and 1 hour after PRK treatment (P<0.001 for both groups), and IL-8 concentrations between control and experimental groups in samples collected 24 hours after LASIK and 24 hours after PRK treatment were greater after PRK treatment (P=0.0005). Comparison of average concentration values of proinflammatory cytokines in all the tested samples between LASIK and PRK groups showed significantly higher levels of IL-1β in the LASIK group 24 hours after treatment (P=0.0134), and of IL-6 in the PRK group 24 hours after treatment (P=0.0031). Conclusion The acute phase of corneal wound healing after excimer laser treatment is defined by an intensive inflammatory response. After PRK

  2. Applying low-energy multipulse excimer laser annealing to improve charge retention of Au nanocrystals embedded MOS capacitors

    NASA Astrophysics Data System (ADS)

    Shen, Kuan-Yuan; Chen, Hung-Ming; Liao, Ting-Wei; Kuan, Chieh-Hsiung

    2015-02-01

    The low-energy multipulse excimer laser annealing (LEM-ELA) is proposed to anneal the nanostructure of nanocrystal (NC) embedded in a SiO2 thin film without causing atomic diffusion and damaging the NCs, since the LEM-ELA combining the advantages of laser annealing and UV curing features rapid heating and increasing oxide network connectivity. A Fourier transform infrared spectroscopy (FTIR) characterization of SiO2 thin films annealed using LEM-ELA indicated that the quality was improved through the removal of water-related impurities and the reconstruction of the network Si-O-Si bonds. Then, LEM-ELA was applied to a SiO2 thin film embedded with Au NCs, which were fabricated as MOS capacitors. The charge retention was greatly improved and the percentage of retained charges was about 10% after 3  ×  108 s. To investigate and differentiate the effects of LEM-ELA on charges stored in both oxide traps and in the Au NCs, a double-mechanism charge relaxation analysis was performed. The results indicated that the oxide traps were removed and the confinement ability of Au NCs was enhanced. The separated memory windows contributed from the charges in Au NCs and those in oxide traps were obtained and further confirmed that the LEM-ELA removed oxide traps without damaging the Au NCs.

  3. Plasma characterization and room temperature growth of carbon nanotubes and nano-onions by excimer laser ablation

    NASA Astrophysics Data System (ADS)

    Radhakrishnan, G.; Adams, P. M.; Bernstein, L. S.

    2007-07-01

    The deposition of carbon nanotubes and carbon nano-onions at room temperature using excimer laser radiation to ablate mixed graphite-metal targets is described. Our deposition conditions are in contrast to other investigations on the pulsed laser deposition of carbon nanotubes that have employed high temperatures and high pressures. We find that the formation of these carbon nanostructures is dependent on the ambient gas employed during ablation. In the presence of O 2 gas, carbon nanotubes and nano-onions are produced, while inert atmospheres such as Ar yield amorphous carbon. High-resolution, in situ, time-resolved emission spectroscopy has been used to track the evolution of species (C 2, C 3, Ni/Co) in the ablation plume. Spectral fits on low and high-resolution spectra reveal that the vibrational-rotational temperatures for C 2 produced in O 2 remain at ˜5000 K for nearly 20 μs but drop rapidly in Ar. Details of the formation of carbon nanotubes and nano-onions, and in situ time-resolved optical emission spectroscopy are described.

  4. Cost-effective SU-8 micro-structures by DUV excimer laser lithography for label-free biosensing

    NASA Astrophysics Data System (ADS)

    Sanza, F. J.; Laguna, M. F.; Casquel, R.; Holgado, M.; Barrios, C. A.; Ortega, F. J.; López-Romero, D.; García-Ballesteros, J. J.; Bañuls, M. J.; Maquieira, A.; Puchades, R.

    2011-04-01

    Cost-effective SU-8 micro-structures on a silicon substrate were developed using 248 nm excimer laser KrF projection, studying the influence of the different variables on the final pattern geometry, finding out that the most critical are exposure dose and post-bake condition. Also a novel and cost effective type of photomask based on commercial polyimide Kapton produced by 355 nm DPSS laser microprocessing was developed, studying the influence of the cutting conditions on the photomask. Finally, as a likely application the biosensing capability with a standard BSA/antiBSA immunoassay over a 10 × 10 micro-plates square lattice of around 10 μm in diameter, 15 μm of spacing and 400 nm in height was demonstrated, finding a limit of detection (LOD) of 33.4 ng/ml which is in the order of magnitude of bioapplications such as detection of cortisol hormone or insulin-like growth factor. Low cost fabrication and vertical interrogation characterization techniques lead to a promising future in the biosensing technology field.

  5. Enhanced electrical and optical properties of room temperature deposited Aluminium doped Zinc Oxide (AZO) thin films by excimer laser annealing

    NASA Astrophysics Data System (ADS)

    El hamali, S. O.; Cranton, W. M.; Kalfagiannis, N.; Hou, X.; Ranson, R.; Koutsogeorgis, D. C.

    2016-05-01

    High quality transparent conductive oxides (TCOs) often require a high thermal budget fabrication process. In this study, Excimer Laser Annealing (ELA) at a wavelength of 248 nm has been explored as a processing mechanism to facilitate low thermal budget fabrication of high quality aluminium doped zinc oxide (AZO) thin films. 180 nm thick AZO films were prepared by radio frequency magnetron sputtering at room temperature on fused silica substrates. The effects of the applied RF power and the sputtering pressure on the outcome of ELA at different laser energy densities and number of pulses have been investigated. AZO films deposited with no intentional heating at 180 W, and at 2 mTorr of 0.2% oxygen in argon were selected as the optimum as-deposited films in this work, with a resistivity of 1×10-3 Ω.cm, and an average visible transmission of 85%. ELA was found to result in noticeably reduced resistivity of 5×10-4 Ω.cm, and enhancing the average visible transmission to 90% when AZO is processed with 5 pulses at 125 mJ/cm2. Therefore, the combination of RF magnetron sputtering and ELA, both low thermal budget and scalable techniques, can provide a viable fabrication route of high quality AZO films for use as transparent electrodes.

  6. A novel microsurgery method for intact plant tissue at the single cell level using ArF excimer laser microprojection.

    PubMed

    Kajiyama, Shin'ichiro; Shoji, Takeshi; Okuda, Shinya; Izumi, Yoshihiro; Fukusaki, Ei-ichiro; Kobayashi, Akio

    2006-02-01

    A novel microsurgery technique for the partial removal of rigid cell-walls in intact plant tissue is established. Using a size-variable slit, an ArF excimer laser was microprojected on the surface of the targeted cell, and this method enabled the area- and depth-controllable processing of the cortical structure of plant cells including the cuticle and cell wall layer. In epidermal cells of all tested plants, viabilities of more than 90% were retained 24 h after irradiation. Scanning electron microscope (SEM) observation revealed that the cuticle layer of the irradiated region was completely ablated, and the cellulose microfibrils of the secondary cell wall were partially removed; furthermore, 4 days after laser treatment, the regeneration of cell wall fibrils was observed. As a model experiment, the transient expression of synthetic green fluorescent protein (sGFP) was performed by the microinjection of cauliflower mosaic virus (CMV) 35S promoter-derived sGFP gene through an "aperture" in the treated cell surface. Moreover, micron-sized fluorescent beads were successfully introduced by the same method into the onion cells indicating that this method can be used to introduce foreign materials as large as organelles. PMID:16193516

  7. Thermodynamic measurements in a high pressure hydrogen-oxygen flame using Raman scattering from a broadband excimer laser

    NASA Technical Reports Server (NTRS)

    Hartfield, Roy, Jr.

    1996-01-01

    Raman scattering is an inelastic molecular scattering process in which incident radiation is reemitted at a fixed change in frequency. Raman spectroscopy can be used to measure the number density and temperature of the irradiated species. The strength of the Raman signal is inversely proportional to the wavelength raised to the fourth power. Consequently, high signal to noise ratios are obtained by using ultraviolet (UV) excitation sources. Using UV sources for Raman Spectroscopy in flames is complicated by the fact that some of the primary constituents in hydrogen-oxygen combustion absorb and reemit light in the UV and these fluorescence processes interfere with the Raman signals. This problem has been handled in atmospheric pressure flames in some instances by using a narrowband tunable excimer laser as a source. This allows for detuning from absorption transitions and the elimination of interfering fluorescence signals at the Raman wavelengths. This approach works well in the atmospheric pressure flame; however, it has two important disadvantages. First, injection-locked narrowband tunable excimer lasers are very expensive. More importantly, however, is the fact that at the high pressures characteristic of rocket engine combustion chambers, the absorption transitions are broadened making it difficult to tune to a spectral location at which substantial absorption would not occur. The approach taken in this work is to separate the Raman signal from the fluorescence background by taking advantage of the fact that Raman signal has nonisotropic polarization characteristics while the fluorescence signals are unpolarized. Specifically, for scattering at right angles to the excitation beam path, the Raman signal is completely polarized. The Raman signal is separated from the fluorescence background by collecting both horizontally and vertically polarized signals separately. One of the polarizations has both the Raman signal and the fluorescence background while the

  8. High-temperature-resistant distributed Bragg reflector fiber laser written in Er/Yb co-doped fiber.

    PubMed

    Guan, Bai-Ou; Zhang, Yang; Wang, Hong-Jun; Chen, Da; Tam, Hwa-Yaw

    2008-03-01

    We present a high-temperature-resistant distributed Bragg reflector fiber laser photowritten in Er/Yb codoped phosphosilicate fiber that is capable of long-term operation at 500 degrees C. Highly saturated Bragg gratings are directly inscribed into the Er/Yb fiber without hydrogen loading by using a 193 nm excimer laser and phase mask method. After annealing at elevated temperature, the remained gratings are strong enough for laser oscillation. The laser operates in robust single mode with output power more than 1 dBm and signal-to-noise ratio better than 70 dB over the entire temperature range from room temperature to 500 degrees C. PMID:18542381

  9. Cell selectivity to laser-induced photoacoustic injury of skin.

    PubMed

    Yashima, Y; McAuliffe, D J; Flotte, T J

    1990-01-01

    Cell selectivity to photoacoustic injury induced by argon-fluoride excimer laser (193 nm) was studied. Rats were irradiated through air or water and a 2.5 mm aperture. The laser was adjusted to deliver 150 mJ/cm2 at the skin surface with 12 and 24 pulses. Immediate damage was assessed by transmission electron microscopy. Cell selectivity was observed in dermis and epidermis. Fibroblasts showed alteration of nuclear chromatin and cytoplasmic organelles, while some of the migratory cells adjacent to fibroblasts did not. Similar difference of damage was observed between keratinocytes and Langerhans cells in epidermis. Considering the relationship between cells and their microenvironment in tissue, this selectivity may be due to the difference of acoustical coupling of propagation of acoustic waves rather than to differential sensitivity of the cells to damage. PMID:2345477

  10. Chloroacetone photodissociation at 193 nm and the subsequent dynamics of the CH3C(O)CH2 radical--an intermediate formed in the OH + allene reaction en route to CH3 + ketene.

    PubMed

    Alligood, Bridget W; FitzPatrick, Benjamin L; Szpunar, David E; Butler, Laurie J

    2011-02-01

    We use a combination of crossed laser-molecular beam experiments and velocity map imaging experiments to investigate the primary photofission channels of chloroacetone at 193 nm; we also probe the dissociation dynamics of the nascent CH(3)C(O)CH(2) radicals formed from C-Cl bond fission. In addition to the C-Cl bond fission primary photodissociation channel, the data evidence another photodissociation channel of the precursor, C-C bond fission to produce CH(3)CO and CH(2)Cl. The CH(3)C(O)CH(2) radical formed from C-Cl bond fission is one of the intermediates in the OH + allene reaction en route to CH(3) + ketene. The 193 nm photodissociation laser allows us to produce these CH(3)C(O)CH(2) radicals with enough internal energy to span the dissociation barrier leading to the CH(3) + ketene asymptote. Therefore, some of the vibrationally excited CH(3)C(O)CH(2) radicals undergo subsequent dissociation to CH(3) + ketene products; we are able to measure the velocities of these products using both the imaging and scattering apparatuses. The results rule out the presence of a significant contribution from a C-C bond photofission channel that produces CH(3) and COCH(2)Cl fragments. The CH(3)C(O)CH(2) radicals are formed with a considerable amount of energy partitioned into rotation; we use an impulsive model to explicitly characterize the internal energy distribution. The data are better fit by using the C-Cl bond fission transition state on the S(1) surface of chloroacetone as the geometry at which the impulsive force acts, not the Franck-Condon geometry. Our data suggest that, even under atmospheric conditions, the reaction of OH with allene could produce a small branching to CH(3) + ketene products, rather than solely producing inelastically stabilized adducts. This additional channel offers a different pathway for the OH-initiated oxidation of such unsaturated volatile organic compounds, those containing a C=C=C moiety, than is currently included in atmospheric models

  11. Analysis of the influence of substrate temperature on hydroxyapatite deposited by laser ablation method using ArF laser

    NASA Astrophysics Data System (ADS)

    Mróz, Waldemar; Jedyński, Marcin; Szymański, Zygmunt; Prokopiuk, Artur; Burdyńska, Sylwia

    2007-02-01

    Hydroxyapatite layers (Ca 10(PO 4)6(OH) II) were deposited by means of laser ablation method using an ArF excimer laser (193 nm). The influence of substrate temperature on the structure of deposited layers was studied. The layers were deposited on Ti6Al4V titanium alloy which temperature varied from 250 °C to 700 °C. The characteristics of the hydroxyapatite coatings were determined by means of Fourier Transform Infrared spectroscopy (FTIR). The obtained spectra reveal that the presence and abundance of the PO 4 absorption bands depend on the substrate temperature. The topography of the deposited layers were analyzed with the use of an Atomic Force Microscope.

  12. Effect of the rinse solution to avoid 193-nm resist line collapse: a study for modification of resist polymer and process conditions

    NASA Astrophysics Data System (ADS)

    Masuda, Seiya; Kobayashi, Masakazu; Kim, Woo-Kyu; Anyadiegwu, Clement; Padmanaban, Munirathna; Dammel, Ralph R.; Tanaka, Keiichi; Yamada, Yoshiaki

    2004-05-01

    The device design rule is continuously shrinking toward optical resolution limit where k1 factor is below 0.3. The requirement for 193 nm photoresist below 90 nm node is quite challenging at the manufacturing phase. Using DI water rinse after development gives a significant amount of line collapse when the aspect ratio is over 3. To avoid line collapse, we co-developed special rinse solution for FIRM process with Tokyo Electron Ltd. Utilizing FIRM process, 90 nm dense line collapse was measured by CD SEM using focus-exposure matrices. The line collapse property has been observed using experimental 193 nm positive tone resist by varying monomer ratio of the polymer and process conditions. The surface property of the resist was also studied to investigate the interaction with rinse solution at the de-protected polymer region. However, a high surfactant concentration in the DI water rinse leads the swelling of the resist pattern profile. The resist component is the key to determine adequate surfactant concentration in rinse solution to minimize line collapse and pattern deformation

  13. Laser-induced photodestruction of the organo-phosphates: DIMP and DMMP

    SciTech Connect

    Radziemski, L.J. Jr.

    1981-01-01

    The infrared and ultraviolet laser-induced photodestruction of diisopropyl methylphosphonate (DIMP) and dimethyl methylphosphonate (DMMP) has been surveyed. We used the excimer lasers ArF (193 nm), KrF (248 nm), XeCl (308 nm), and quadrupled Nd:YAG (266 nm) as well as a pulsed CO/sup 2/ laser. Samples were irradiated in the vapor and liquid phases. Photodissociation was observed at all irradiation wavelengths, being most efficient when ArF irradiated DIMP or DMMP in the vapor phase in the presence of air or oxygen. Pulsed, focused CO/sup 2/ radiation led to multiple photon dissociation and pyrolytic destruction. Light hydrocarbon gases were the principal decomposition products. Hydrogen, CO, CO/sup 2/ and water were also detected. The residual liquid is likely to be a phosphorus-bearing acid.

  14. Laser-induced photodestruction of the organo-phosphates: DIMP and DMMP.

    PubMed

    Radziemski, L J

    1981-01-01

    The infrared and ultraviolet laser-induced photodestruction of diisopropyl methylphosphonate (DIMP) and dimethyl methylphosphonate (DMMP) has been surveyed. We used the excimer lasers ArF (193 nm), KrF (248 nm), XeCl (308 nm), and quadrupled Nd:YAG (266 nm) as well as a pulsed CO2 laser. Samples were irradiated in the vapor and liquid phases. Photodissociation was observed at all irradiation wavelengths, being most efficient when ArF irradiated DIMP or DMMP in the vapor phase in the presence of air or oxygen. Pulsed, focused CO2 radiation led to multiple photon dissociation and pyrolytic destruction. Light hydrocarbon gases were the principal decomposition products. Hydrogen, CO, CO2 and water were also detected. The residual liquid is likely to be a phosphorus-bearing acid. PMID:7252066

  15. Excimer laser annealing to fabricate low cost solar cells. Quarterly technical report No. 2, 1 July-30 September 1984

    SciTech Connect

    Not Available

    1984-10-01

    The objective of this research is to determine whether or not pulsed excimer laser annealing (PELA) of ion-implanted junctions is a cost effective replacement for diffused junctions of crystalline silicon solar cells. The preliminary economic analysis completed during the first quarter of this program showed that the use of ion implantation and PELA to fabricate both the front junction and back surface field (BSF) would cost approximately 35 cents per peak watt (Wp), compared to a cost of 15 cents/Wp for a hypothetical baseline diffusion process that it is assumed to yield cells with an average efficiency of 14%. A cost advantage may be attained, however, if the implant-PELA process yields an improvement in the average cell efficiency from 14 to 16%; this improvement would lower the overall cost of the module by about 15 cents/Wp. The technical goal of this research is to develop an optimized PELA process compatible with commercial production, and to demonstrate increased cell efficiency with sufficient product for adequate statistical analysis. During the second quarter of this program, it was shown that the laser chosen for this work, operating with an output power of 50 watts, demonstrated sufficient processing speed for commercial production. Also during this time period, the PELA process was optimized for annealing phosphorus implants in polished p-type silicon wafers. The best solar cell obtained in this way had an efficiency of 10.5% at AM1 illumination withour AR coating. This efficiency is equal to that of co-processed furnace annealed ion-implanted controls. Work planned during the next quarter includes optimization of the PELA process parameters for use with screen printed contacts, optimization of the PELA process for use with texture-etched material, and development of a set of parameters to anneal boron or boron-trifluoride implants.

  16. [In vitro studies of shock wave effects during ablation of normal and atherosclerotic vascular wall by excimer laser].

    PubMed

    Haase, K K; Hanke, H; Baumbach, A; Wehrmann, M; Rose, C; Karsch, K R

    1993-02-01

    Ablation of atherosclerotic plaque and normal arterial wall was performed using a xenon-chloride-excimer laser with a wavelength of 308 nm and a pulse duration of 115 ns. The light was transmitted via a 600 micron fiber and adjusted to an energy density of 3.5 J/cm2. The acoustic signals generated by the laser pulse were measured with hydrophones consisting of polyvinylidenefluoride with active diameters of 0.3 mm and recorded on a dual-channel digital storage oscilloscope using either a 0.5 m coaxial cable or a broadband transmission system. From 19 cadavers human aortic tissue segments were excised and macroscopically classified as either normal or calcified atherosclerotic plaque. Approximately 500 measurements were performed in saline and blood each. Histological analysis was carried out after the experiments to verify the macroscopic diagnosis and to correlate the acoustic responses with the tissue characteristics. For "normal" arterial segments, maximum peak pressure was 1.25 MPa +/- 0.85 MPa, rise time 163 ns +/- 43 ns, and pressure increase 8.2 kPa +/- 5.4 kPa/ns in saline. For calcified, atheromatous segments a significantly higher maximum pressure (2.20 MPa +/- 1.16 MPa), a significantly shorter rise time (69.9 ns +/- 25.8 ns), and a significantly higher pressure increase (32.3 kPa +/- 21.3 kPa/ns) was found in saline (p < or = 0.0001). In blood, maximum peak pressure was 1.29 MPa +/- 0.43 MPa, rise time 93.3 ns +/- 27.7 ns, and pressure increase 14.6 kPa +/- 5.2 kPa/ns for "normal" arterial segments. Maximum peak pressure (2.28 MPa +/- 0.63 MPa) and pressure increase (32.8 kPa +/- Pa/ns) were significantly higher for calcified tissue segments.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8465570

  17. Selective area in situ conversion of Si (0 0 1) hydrophobic to hydrophilic surface by excimer laser irradiation in hydrogen peroxide

    NASA Astrophysics Data System (ADS)

    Liu, Neng; Huang, Xiaohuan; Dubowski, Jan J.

    2014-09-01

    We report on a method of rapid conversion of a hydrophobic to hydrophilic state of an Si (0 0 1) surface irradiated with a relatively low number of pulses of an excimer laser. Hydrophilic Si (0 0 1), characterized by the surface contact angle (CA) of near 15°, is fabricated following irradiation with either KrF or ArF excimer lasers of hydrophobic samples (CA ˜ 75°) immersed in a 0.01% H2O2/H2O solution. The chemical and structural analysis carried with x-ray photoelectron spectroscopy and atomic force microscopy measurements confirmed the formation of OH-terminated Si (0 0 1) surface with no detectable change in the surface morphology of the laser-irradiated material. To investigate the efficiency of this laser-induced hydrophilization process, we demonstrate a selective area immobilization of biotin-conjugated fluorescein-stained nanospheres outside of the laser-irradiated area. The results demonstrate the potential of the method for the fabrication of biosensing architectures and advancements of the Si-based microfluidic device technology.

  18. Pulsed excimer laser processing for cost-effective solar cells. Quarterly report No. 1, May-July 1984

    SciTech Connect

    Wong, D.

    1984-01-01

    The objective of this contract is to develop a solar cell process sequence that incorporates three process steps which use pulsed excimer lasers, to verify that this sequence yields high efficiency cells at a low cost, and to document the feasibility of carrying this technology from the laboratory bench scale to factory size. The three process steps are: junction formation, surface passivation, and front metallization. The effort is to take place during a one-year period. During this reporting period, a series of annealing experiments were conducted. Parameter variations included beam energy density, percentage of beam overlap, sources of diffusant, and different surface conditions such as chemical-mechanical polished, caustic etched, and textured. Diffusant deposition included spin-on liquid dopant and ion implant. Due to the lower surface reflectivity and the wetting effect by the spin-on source, textured wafers experienced more surface damage and stress than polished wafers. Maximum cell efficiency obtained for Cz polished wafers was 9% and for Cz textured wafers was 11.5% (no A/R). Surface damage limited the cell efficiency. Laser annealing on ion-implanted wafers was conducted with phosphorus implant with acceleration energy of 10 keV at fluences of 1-5 x 10/sup 15/ atom/cm/sup 2/. Maximum cell efficiency was less than 8% (no A/R coating). Low J/sub sc/, V/sub oc/, and fill factor suggested incomplete implant damage removal. Decreasing the implant voltage from 10 keV to 5 keV and increasing laser energy to above 0.9 J/cm/sup 2/, some cell efficiencies over 9.4% before A/R. The goal of producing cells of 16.5% has not materialized due to problems in ion implant uniformity, unavailable low keV ion implant, and laser beam inhomogeneity. During the next period, work will focus on developing a 1 keV glow discharge capability and on fabrication of Boron implanted junctions on n type wafers.

  19. Double patterning scheme for sub-0.25 k1 single damascene structures at NA=0.75, λ=193nm

    NASA Astrophysics Data System (ADS)

    Maenhoudt, M.; Versluijs, J.; Struyf, H.; Van Olmen, J.; Van Hove, M.

    2005-05-01

    Using 193nm lithography at NA=0.75, the minimum pitch that can be obtained in a single exposure is 160nm for dark field structures that are used in single damascene interconnect processing. In order to evaluate the critical electrical parameters for the smaller technologies, a double patterning scheme has been developed to obtain electrical structures at pitches from 140nm down to 100nm. This corresponds to k1-factors of 0.27 to 0.19 for dense trenches. The designs have been split up into two layers at more relaxed pitch (twice the final pitch). The first step consists in patterning a small semi-isolated trench at this more relaxed pitch. Because of the limited resist resolution for semi-isolated trenches, shrink techniques such as resist reflow or RELACS are needed. After etching this first layer into a low-k material or metal hard mask, planarization of the topography is critical before performing the second exposure. The second exposure is then identical to the first one, but overlay to the first layer is extremely critical in order to get a reasonable process window. In this paper, we illustrate the feasibility of the double patterning technique for early sub-65nm-node evaluation of low-k materials. The resolution and processing limits will be shown for single layer resist processing with RELACS shrink for 193nm lithography at NA=0.75. The planarization for the second photo is done using organic BARC. We will also quantify the overlay requirements to measured and introduced overlay errors.

  20. Removal of dust particles from metal-mirror surfaces by excimer-laser radiation

    NASA Astrophysics Data System (ADS)

    Mann, Klaus R.; Wolff-Rottke, B.; Mueller, F.

    1995-07-01

    The effect of particle desorption from Al mirror surfaces by the influence of pulsed UV laser radiation has been studied. The investigations are closely related to the demands of astronomers, who are looking for a more effective way of cleaning the Al coatings of future very large telescope mirrors. A systematic parameter study has been performed in order to determine the irradiation conditions which yield the highest dust removal efficiency (i.e. reflectivity increase) on contaminated samples, taking particularly into account laser-induced damage and degradation effects of coating and substrate. The particle removal rate increases with increasing laser fluence, being limited however by the damage threshold of the coating. Therefore, parameters influencing the damage threshold of metal coatings like wavelength, pulse width, and number of pulses have been studied in detail. Data indicate that on Al coated BK7 and Zerodur samples KrF laser radiation yields the optimum result, with cleaning efficiencies comparable to polymer film stripping. The initial reflectivity of the clean coating can nearly be reinstalled, in particular when an additional solvent film on the sample surface is applied. Hence, laser desorption seems to be a viable method of cleaning large Al mirrors for telescopes.

  1. A method of atmospheric density measurements during Shuttle entry using UV laser Rayleigh scattering

    NASA Technical Reports Server (NTRS)

    Mckenzie, Robert L.

    1987-01-01

    A detailed study is described of the performance capabilities and the hardware requirements for a method in which ambient density is measured along the Space Shuttle flight path using on-board optical instrumentation. The technique relies on Rayleigh scattering of light from a pulsed, ultraviolet, ArF excimer laser operating at a wavelength of 193 nm. The method is shown to be capable of providing direct measurements of ambient density with an uncertainty of less than 1 percent and with a spatial resolution of 1 km, over an altitude range from 50 to 90 km. In addition, extensions of this concept are discussed that allow measurements of the shock wave location and the density profile within the shock layer. Two approaches are identified that appear to be feasible, in which the same laser system is used for the extended measurements as that required for the ambient density measurements.

  2. Analysis and differentiation of mineral dust by single particle laser mass spectrometry

    SciTech Connect

    Gallavardin, S. J.; Lohmann, U.; Cziczo, Daniel J.

    2008-05-09

    Abstract This study evaluates the potential of single particle laser desorption/ionization mass spectrometry for the analysis of atmospherically relevant mineral dusts. Samples of hematite, goethite, calcium carbonate, calcium sulfate, silica, quartz, montmorrillonite, kaolinite, illite, hectorite, wollastonite and nephelinsyenit were investigated in positive and negative ion mode with a monopolar time-of-flight mass spectrometer where the desorption/ionization step was performed with a 193 nm excimer laser (~109 W/cm2). Particle size ranged from 500 nm to 3 μm. Positive mass spectra mainly provide elemental composition whereas negative ion spectra provide information on element speciation and of a structural nature. The iron oxide, calcium-rich and aluminosilicate nature of particles is established in positive ion mode. The differentiation of calcium materials strongly relies on the calcium counter-ions in negative mass spectra. Aluminosilicates can be differentiated in both positive and negative ion mode using the relative abundance of various aluminum and silicon ions.

  3. Pulsed laser deposition of bioactive glass films in ammonia and disilane atmospheres

    NASA Astrophysics Data System (ADS)

    Borrajo, J. P.; González, P.; Liste, S.; Serra, J.; Chiussi, S.; León, B.; Pérez-Amor, M.

    2005-07-01

    The effect of two reactive gases on the properties of bioactive glass thin films produced by pulsed laser deposition (PLD) was studied. The ablation of a bioactive silica-based glass was carried out by an ArF excimer laser ( λ = 193 nm, Φ = 4.2 J cm -2, τ = 25 ns, f = 10 Hz) at various pressures of Si 2H 6/Ar and NH 3/Ar reactive mixtures. The bonding configuration and chemical environment of the resulting coatings were followed by Fourier transform infrared spectroscopy (FT-IR). The composition and bond arrangement of bioactive glass films were tuned by varying the chamber atmosphere. The results show how to adjust film characteristics for osteointegration of implants.

  4. Characteristics of 308 nm excimer laser activated arterial tissue photoemission under ablative and non-ablative conditions.

    PubMed

    Laufer, G; Wollenek, G; Rüeckle, B; Buchelt, M; Kuckla, C; Ruatti, H; Buxbaum, P; Fasol, R; Zilla, P

    1989-01-01

    The present study was designed to assess the characteristics of tissue photoemission obtained from normal and atherosclerotic segments of human postmortem femoral arteries by 308 nm excimer laser irradiation of 60 ns pulsewidth. Three ablative (20, 30, and 40 mJ/pulse) and three non-ablative (2.5, 5, and 10 mJ/pulse) energy fluences were employed. Both the activating laser pulses and the induced photoemission were guided simultaneously over one and the same 1,000 micron core optical fiber that was positioned in direct tissue contact perpendicular to the vascular surface. The spectral lineshape of normal arterial and noncalcified atherosclerotic structures was characterized by a broad-continuum, double-peak emission of relevant intensity between wavelengths of 360 and 500 nm, with the most prominent emission in the range of 400-415 (407 nm peak) and 430-445 nm (437 nm peak). Fibrous and lipid atherosclerotic lesions, however, exhibited a significantly reduced intensity at 437 nm compared to normal artery layers (P less than 0.001), expressed as a 407/437 nm ratio of 1.321 +/- 0.075 for fibrous and 1.392 +/- 0.104 for lipid lesions. Normal artery components presented with approximately equal intensity at both emission peaks (407/437 nm ratio: intima, 1.054 +/- 0.033; media, 1.024 +/- 0.019; adventitia, 0.976 +/- 0.021). Comparison of spectral lineshape obtained under various energy fluences within a group of noncalcified tissues disclosed no substantial difference using the 407/437 nm ratio (P greater than 0.05). In contrast, calcified lesions revealed high-intensity multiple-line (397, 442, 461, and 528 nm) emission spectra under ablative energy fluences, whereas a low-intensity broad-continuum, single-peak spectrum resulted from irradiation beyond the ablation threshold. Thus, these findings suggest fluorescence phenomena for broad-continuum spectra, and plasma emission for multiple-line spectra as an underlying photodynamic process. Regardless of the activating

  5. Melting evaporation and recrystallization of a-SiC:H films by excimer laser

    SciTech Connect

    Wickramanayaka, S.; Kitamura, K.; Nakanishi, Y.; Hatanaka, Y.

    1996-12-31

    A study of laser annealing of a-SiC:H films was carried out in order to obtain poly-SiC films. First, a-SiC:H films were fabricated at temperatures ranging from 30 to 400 C. All these films show amorphous structure before the annealing process. After annealing by a single pulse of 248 nm laser, films show poly-SiC structure. The pulse energies used for these anneals varied from 30 to 300 mJ/pulse. After exposing to a laser pulse, the a-SiC:H films melt and recrystallize forming poly-SiC structure. In addition to this process, a fraction of the film is observed to be vaporized. This vaporized fraction depends on the original film composition, hardness and the laser pulse-energy. Electrical resistivity of the films before the annealing process lies in the region of 10{sup 15} {Omega}cm. This resistivity drops drastically after the annealing process.

  6. Pulsed lasers in dentistry: sense or nonsense?

    NASA Astrophysics Data System (ADS)

    Koort, Hans J.; Frentzen, Matthias

    1991-05-01

    The great interest in the field of laser applications in dentistry provokes the question, if all these new techniques may really fulfill advantages, which are expected after initial in-vitro studies. Whereas laser surgery of soft oral tissues has been developed to a standard method, laser treatment of dental hard tissues and the bone are attended with many unsolved problems. Different laser types, especially pulsed lasers in a wide spectrum of wavelengths have been proofed for dental use. Today neither the excimer lasers, emitting in the far uv-range from 193 to 351 nm, nor the mid-infrared lasers like Nd:YAG (1,064 μm), Ho:YAG (2,1 μm) and Er:YAG (2,96 μm) or the C02-laser (10,6 μm) show mechanism of interaction more carefully and faster than a preparation of teeth with diamond drillers. The laser type with the most precise and considerate treatment effects in the moment is the short pulsed (15 ns) ArF-excimer laser with a wavelength of 193 nm. However this laser type has not yet the effectivity of mechanical instruments and it needs a mirror system to deliver the radiation. Histological results point out, that this laser shows no significant pathological alterations in the adjacent tissues. Another interesting excimer laser, filled with XeCI and emitting at a wavelength of 308 nm has the advantage to be good to deliver through quartz fibers. A little more thermal influence is to be seen according to the longer wavelength. Yet the energy density, necessary to cut dental hard tissues will not be reached with the laser systems available now. Both the pulsed Er:YAG- (2,94 μm, pulse duration 250 s) and the Ho:YAG -laser (2,1 μm, pulse duration 250 μs) have an effective coupling of the laser energy to hydrogeneous tissues, but they do not work sufficient on healthy enamel and dentine. The influence to adjacent healthy tissue is not tolerable, especially in regard of the thermal damage dentine and pulp tissues. Moreover, like the 193 nm ArF-excimer laser

  7. Some optical and electron microscope comparative studies of excimer laser-assisted and nonassisted molecular-beam epitaxically grown thin GaAs films on Si

    NASA Technical Reports Server (NTRS)

    Lao, Pudong; Tang, Wade C.; Rajkumar, K. C.; Guha, S.; Madhukar, A.; Liu, J. K.; Grunthaner, F. J.

    1990-01-01

    The quality of GaAs thin films grown via MBE under pulsed excimer laser irradiation on Si substrates is examined in both laser-irradiated and nonirradiated areas using Raman scattering, Rayleigh scattering, and by photoluminescence (PL), as a function of temperature, and by TEM. The temperature dependence of the PL and Raman peak positions indicates the presence of compressive stress in the thin GaAs films in both laser-irradiated and nonirradiated areas. This indicates incomplete homogeneous strain relaxation by dislocations at the growth temperature. The residual compressive strain at the growth temperature is large enough such that even with the introduction of tensile strain arising from the difference in thermal expansion coefficients of GaAs and Si, a compressive strain is still present at room temperature for these thin GaAs/Si films.

  8. Fabrication of functional fibronectin patterns by nanosecond excimer laser direct write for tissue engineering applications.

    PubMed

    Grigorescu, S; Hindié, M; Axente, E; Carreiras, F; Anselme, K; Werckmann, J; Mihailescu, I N; Gallet, O

    2013-07-01

    Laser direct write techniques represent a prospective alternative for engineering a new generation of hybrid biomaterials via the creation of patterns consisting of biological proteins onto practically any type of substrate. In this paper we report on the characterization of fibronectin features obtained onto titanium substrates by UV nanosecond laser transfer. Fourier-transform infrared spectroscopy measurements evidenced no modification in the secondary structure of the post-transferred protein. The molecular weight of the transferred protein was identical to the initial fibronectin, no fragment bands being found in the transferred protein's Western blot migration profile. The presence of the cell-binding domain sequence and the mannose groups within the transferred molecules was revealed by anti-fibronectin monoclonal antibody immunolabelling and FITC-Concanavalin-A staining, respectively. The in vitro tests performed with MC3T3-E1 osteoblast-like cells and Swiss-3T3 fibroblasts showed that the cells' morphology and spreading were strongly influenced by the presence of the fibronectin spots. PMID:23615786

  9. Excimer laser deinsulation of Parylene-C on iridium for use in an activated iridium oxide film-coated Utah electrode array

    PubMed Central

    Yoo, Je-Min; Negi, Sandeep; Tathireddy, Prashant; Solzbacher, Florian; Song, Jong-In; Rieth, Loren W.

    2013-01-01

    Implantable microelectrodes provide a measure to electrically stimulate neurons in the brain and spinal cord and record their electrophysiological activity. A material with a high charge capacity such as activated or sputter-deposited iridium oxide film (AIROF or SIROF) is used as an interface. The Utah electrode array (UEA) uses SIROF for its interface material with neural tissue and oxygen plasma etching (OPE) with an aluminium foil mask to expose the active area, where the interface between the electrode and neural tissue is formed. However, deinsulation of Parylene-C using OPE has limitations, including the lack of uniformity in the exposed area and reproducibility. While the deinsulation of Parylene-C using an excimer laser is proven to be an alternative for overcoming the limitations, the iridium oxide (IrOx) suffers from fracture when high laser fluence (>1000 mJ/cm2) is used. Iridium (Ir), which has a much higher fracture resistance than IrOx, can be deposited before excimer laser deinsulation and then the exposed Ir film area can be activated by electrochemical treatment to acquire the AIROF. Characterisation of the laser-ablated Ir film and AIROF by surface analysis (X-ray photoelectron spectroscopy, scanning electron microscope, and atomic force microscope) and electrochemical analysis (electrochemical impedance spectroscopy, and cyclic voltammetry) shows that the damage on the Ir film induced by laser irradiation is significantly less than that on SIROF, and the AIROF has a high charge storage capacity. The results show the potential of the laser deinsulation technique for use in high performance AIROF-coated UEA fabrication. PMID:23458659

  10. XeCl excimer laser-induced autofluorescence spectroscopy for human cerebral tumor diagnosis: preliminary study

    NASA Astrophysics Data System (ADS)

    Avrillier, Sigrid; Hor, Frederic; Desgeorges, Michel; Ettori, Dominique; Sitbon, Jean R.

    1993-09-01

    Three-hundred-eight nm laser-induced autofluorescence spectra of the normal human brain, astrocytoma grade IV and glioblastoma grade IV specimens, have been recorded in vitro two hours after surgical resection. Typical fluorescence spectra for normal (N) and malignant (M) tissue show 4 maxima at about 352, 362, 383, and 460 nm. These spectra are analyzed in detail. Subtle differences in normalized spectra of N and M tissues appear to be large enough for diagnosis. Several criteria such as maxima and minima absolute intensity and intensity ratios at typical wavelengths are computed and used to classify the tissue. This preliminary study shows that fluorescence spectroscopy with 308 nm UV excitation could be a valid technique for discriminating tumor types. However, it should be noted that these measurements are made in vitro. Living tissues may have different spectral characteristics, therefore future in vivo investigations must be performed.

  11. Excimer laser produced plasmas in copper wire targets and water droplets

    NASA Technical Reports Server (NTRS)

    Song, Kyo-Dong; Alexander, D. R.

    1994-01-01

    Elastically scattered incident radiation (ESIR) from a copper wire target illuminated by a KrF laser pulse at lambda = 248 nm shows a dinstinct two-peak structure which is dependent on the incident energy. The time required to reach the critical electron density (n(sub c) approximately = 1.8 x 10(exp 22) electrons/cu cm) is estimated at 11 ns based on experimental results. Detailed ESIR characteristics for water have been reported previously by the authors. Initiation of the broadband emission for copper plasma begins at 6.5 +/- 1.45 ns after the arrival of the laser pulse. However, the broadband emission occurs at 11 +/- 0.36 ns for water. For a diatomic substance such as water, the electron energy rapidly dissipates due to dissociation of water molecules, which is absent in a monatomic species such as copper. When the energy falls below the excitation energy of the lowest electron state for water, it becomes a subexcitation electron. Lifetimes of the subexcited electrons to the vibrational states are estimated to be of the order of 10(exp -9) s. In addition, the ionization potential of copper (440-530 nm) is approximately 6 eV, which is about two times smaller than the 13 eV ionization potential reported for water. The higher ionization potential contributes to the longer observed delay time for plasma formation in water. After initiation, a longer time is required for copper plasma to reach its peak value. This time delay in reaching the maximum intensity is attributed to the energy loss during the interband transition in copper.

  12. Agreement between Clinical History Method, Orbscan IIz, and Pentacam in Estimating Corneal Power after Myopic Excimer Laser Surgery

    PubMed Central

    Lekhanont, Kaevalin; Nonpassopon, Manachai; Wannarosapark, Khemruetai; Chuckpaiwong, Varintorn

    2015-01-01

    The purpose of this study was to investigate the agreement between the clinical history method (CHM), Orbscan IIz, and Pentacam in estimating corneal power after myopic excimer laser surgery. Fifty five patients who had myopic LASIK/PRK were recruited into this study. One eye of each patient was randomly selected by a computer-generated process. At 6 months after surgery, postoperative corneal power was calculated from the CHM, Orbscan IIz total optical power at the 3.0 and 4.0 mm zones, and Pentacam equivalent keratometric readings (EKRs) at 3.0, 4.0, and 4.5 mm. Statistical analyses included multilevel models, Pearson’s correlation test, and Bland-Altman plots. The Orbscan IIz 3.0-mm and 4.0 mm total optical power, and Pentacam 3.0-mm, 4.0-mm, and 4.5-mm EKR values had strong linear positive correlations with the CHM values (r = 0.90–0.94, P = <0.001, for all comparisons, Pearson’s correlation). However, only Pentacam 3.0-mm EKR was not statistically different from CHM (P = 0.17, multilevel models). The mean 3.0- and 4.0-mm total optical powers of the Orbscan IIz were significantly flatter than the values derived from CHM, while the average EKRs of the Pentacam at 4.0 and 4.5 mm were significantly steeper. The mean Orbscan IIz 3.0-mm total optical power was the lowest keratometric reading compared to the other 5 values. Large 95% LoA was observed between each of these values, particularly EKRs, and those obtained with the CHM. The width of the 95% LoA was narrowest for Orbscan IIz 3.0-mm total optical power. In conclusion, the keratometric values extracted from these 3 methods were disparate, either because of a statistically significant difference in the mean values or moderate agreement between them. Therefore, they are not considered equivalent and cannot be used interchangeably. PMID:25853655

  13. Effects of closed immersion filtered water flow velocity on the ablation threshold of bisphenol A polycarbonate during excimer laser machining

    NASA Astrophysics Data System (ADS)

    Dowding, Colin; Lawrence, Jonathan

    2010-04-01

    A closed flowing thick film filtered water immersion technique ensures a controlled geometry for both the optical interfaces of the flowing liquid film and allows repeatable control of flow-rate during machining. This has the action of preventing splashing, ensures repeatable machining conditions and allows control of liquid flow velocity. To investigate the impact of this technique on ablation threshold, bisphenol A polycarbonate samples have been machined using KrF excimer laser radiation passing through a medium of filtered water flowing at a number of flow velocities, that are controllable by modifying the liquid flow-rates. An average decrease in ablation threshold of 7.5% when using turbulent flow velocity regime closed thick film filtered water immersed ablation, compared to ablation using a similar beam in ambient air; however, the use of laminar flow velocities resulted in negligible differences between closed flowing thick film filtered water immersion and ambient air. Plotting the recorded threshold fluence achieved with varying flow velocity showed that an optimum flow velocity of 3.00 m/s existed which yielded a minimum ablation threshold of 112 mJ/cm 2. This is attributed to the distortion of the ablation plume effected by the flowing immersion fluid changing the ablation mechanism: at laminar flow velocities Bremsstrahlung attenuation decreases etch rate, at excessive flow velocities the plume is completely destroyed, removing the effect of plume etching. Laminar flow velocity regime ablation is limited by slow removal of debris causing a non-linear etch rate over ' n' pulses which is a result of debris produced by one pulse remaining suspended over the feature for the next pulse. The impact of closed thick film filtered water immersed ablation is dependant upon beam fluence: high fluence beams achieved greater etch efficiency at high flow velocities as the effect of Bremsstrahlung attenuation is removed by the action of the fluid on the plume; low

  14. Internal energy of HCl upon photolysis of 2-chloropropene at 193 nm investigated with time-resolved Fourier-transform spectroscopy and quasiclassical trajectories

    SciTech Connect

    Chang, C.-M.; Huang, Y.-H.; Liu, S.-Y.; Lee, Y.-P.; Pombar-Perez, Marta; Martinez-Nunez, Emilio; Vazquez, Saulo A.

    2008-12-14

    Following photodissociation of 2-chloropropene (H{sub 2}CCClCH{sub 3}) at 193 nm, vibration-rotationally resolved emission spectra of HCl ({upsilon}{<=}6) in the spectral region of 1900-2900 cm{sup -1} were recorded with a step-scan time-resolved Fourier-transform spectrometer. All vibrational levels show a small low-J component corresponding to {approx}400 K and a major high-J component corresponding to 7100-18 700 K with average rotational energy of 39{+-}{sub 3}{sup 11} kJ mol{sup -1}. The vibrational population of HCl is inverted at {upsilon}=2, and the average vibrational energy is 86{+-}5 kJ mol{sup -1}. Two possible channels of molecular elimination producing HCl+propyne or HCl+allene cannot be distinguished positively based on the observed internal energy distribution of HCl. The observed rotational distributions fit qualitatively with the distributions of both channels obtained with quasiclassical trajectories (QCTs), but the QCT calculations predict negligible populations for states at small J. The observed vibrational distribution agrees satisfactorily with the total QCT distribution obtained as a weighted sum of contributions from both four-center elimination channels. Internal energy distributions of HCl from 2-chloropropene and vinyl chloride are compared.

  15. 10 x 10 cm-sq aperture 1 Hz repetition rate X-ray preionized-discharge pumped KrF excimer laser

    NASA Astrophysics Data System (ADS)

    Mizoguchi, H.; Endoh, A.; Jethwa, J.; Schaefer, F. P.

    A 10 x 10 sq cm aperture X-ray preionized discharge-pumped KrF excimer amplifier for subpicosecond pulse amplification is demonstrated experimentally in the oscillator mode operation. A fast pulse-forming line (36 nF, 340 kV) together with a peaking capacitor (6 nF) switched with a rail-gap switch, and collimated X-ray preionization is employed to obtain a wide and uniform discharge. The active cross section of the laser beam is about 10 x 8 sq cm and the intense plateau region is about 10 x 5.5 sq cm. The laser pulse energy exceeds 4.7 J in a 28 ns pulse (FWHM).

  16. Formation of densely populated SiOx microtree-like structures on the Si (100) surface using excimer laser irradiation in air

    NASA Astrophysics Data System (ADS)

    Yang, De-Quan; Sacher, Edward; Meunier, Michel

    2004-10-01

    SiOx microforest-like structures have been produced on Si (100) surfaces by pulsed excimer laser irradiation in air. Scanning electron microscopic observations have indicated these structures, which are composed of aggregated nanoparticles, to be 1-5 μm in diameter and 10-20 μm high, and to have the appearance of trees. XPS analysis has shown them to be composed of a-SiOx (1laser irradiation, our microforest-like trees have many sharp nanoscale branches, which may require lower emission voltages in application such as field-emission sources in plasma displays.

  17. A method of atmospheric density measurements during space shuttle entry using ultraviolet-laser Rayleigh scattering

    NASA Technical Reports Server (NTRS)

    Mckenzie, Robert L.

    1988-01-01

    An analytical study and its experimental verification are described which show the performance capabilities and the hardware requirements of a method for measuring atmospheric density along the Space Shuttle flightpath during entry. Using onboard instrumentation, the technique relies on Rayleigh scattering of light from a pulsed ArF excimer laser operating at a wavelength of 193 nm. The method is shown to be capable of providing density measurements with an uncertainty of less than 1 percent and with a spatial resolution along the flightpath of 1 km, over an altitude range from 50 to 90 km. Experimental verification of the signal linearity and the expected signal-to-noise ratios is demonstrated in a simulation facility at conditions that duplicate the signal levels of the flight environment.

  18. Fabrication of 250-nm-hole arrays in glass and fused silica by UV laser ablation

    NASA Astrophysics Data System (ADS)

    Karstens, R.; Gödecke, A.; Prießner, A.; Ihlemann, J.

    2016-09-01

    Parallel nanohole drilling in glass using an ArF excimer laser (193 nm) is demonstrated. For the first time, hole arrays with 500 nm pitch and individual holes with 250 nm diameter and more than 100 nm depth are fabricated by phase mask imaging using a Schwarzschild objective. Holes in soda lime glass are drilled by direct ablation; fused silica is processed by depositing a SiOx-film on SiO2, patterning the SiOx by ablation, and finally oxidizing the remaining SiOx to SiO2. Thermally induced ordered dewetting of noble metal films deposited on such templates may be used for the fabrication of plasmonic devices.

  19. Fabrication of an integrated optical Mach-Zehnder interferometer based on refractive index modification of polymethylmethacrylate by krypton fluoride excimer laser radiation

    NASA Astrophysics Data System (ADS)

    Koerdt, Michael; Vollertsen, Frank

    2011-04-01

    It is known that deep ultraviolet (UV) radiation induces a refractive index increase in the surface layer of polymethylmethacrylate (PMMA) samples. This effect can be used for the fabrication of integrated optical waveguides. PMMA is of considerable interest for bio and chemical sensing applications because it is biocompatible and can be micromachined by several methods, e.g. structuring by photolithography, ablation and hot embossing. In the presented work direct UV irradiation of a common PMMA substrate by a krypton fluoride excimer laser beam through a contact mask has been used to write integrated optical Mach-Zehnder interferometers (MZI). MZI are used as sensitive bio and chemical sensors. The aim was to determine contact mask design and laser irradiation parameters for fabricating single-mode MZI for the infrared region from 1.30 μm to 1.62 μm. Straight and curved waveguides have been generated and characterized to determine the optical losses. The generation of channel waveguide structures has been optimized by a two step irradiation process to minimize the lithographic writing time and optical loss. By flood exposure to UV laser radiation in the first step the optical absorption of PMMA can be increased in the irradiated region. The required refractive index profile is then achieved with a second lithographic irradiation. The spectral behaviour of an unbalanced, integrated optical MZI fabricated by this excimer laser based contact mask method is shown for the first time. Further the optical intensity at the output port of a MZI has been measured while the optical path length difference was tuned by creating a temperature difference between the two arms of the MZI.

  20. Synthesis of diamond on WC-Co substrates using a KrF excimer laser in combination with a combustion flame

    NASA Astrophysics Data System (ADS)

    Han, Y. X.; Ling, H.; Lu, Y. F.

    2007-02-01

    A KrF excimer laser was used in combination with a combustion flame to deposit diamond films on cemented tungsten carbide (WC-Co) substrates. The laser has a wavelength of 248 nm, a pulse width of 23 ns, a pulse energy range of 84~450 mJ, and a repetition rate up to 50 Hz. Using the combustion flame method, diamond films were deposited on the laser-processed WC-Co substrates for 10 min. The morphologies of the deposited diamond films were examined using a scanning electron microscopy (SEM). The composition and bonding structures in the deposited films were studied by energy dispersive X-ray analysis (EDX) and Raman spectroscopy, respectively. The film adhesion was characterized by scratching a razor across the films. It was found that C composition on WC-Co substrate surfaces was eliminated by the laser irradiation. As a consequence, diamond nucleation density decreased and diamond grains grew larger in the laser-processed areas. Based on the experimental results, a film growth mechanism at different deposition temperature ranges corresponding to pre-deposition laser-surface-treatment effects was proposed.

  1. Electrical properties of Sb-doped epitaxial SnO2 thin films prepared using excimer-laser-assisted metal-organic deposition

    NASA Astrophysics Data System (ADS)

    Tsuchiya, Tetsuo; Nakajima, Tomohiko; Shinoda, Kentaro

    2013-12-01

    Excimer-laser-assisted metal-organic deposition (ELAMOD) was used to prepare Sb-doped epitaxial (001) SnO2 thin films on (001) TiO2 substrates at room temperature. The effects of laser fluence, the number of shots with the laser, and Sb content on the electrical properties such as resistivity, carrier concentration, and carrier mobility of the films were investigated. The resistivity of the Sb-doped epitaxial (001) SnO2 thin film prepared using an ArF laser was lower than that of the film prepared using a KrF laser. The van der Pauw method was used to measure the resistivity, carrier concentration, and carrier mobility of the Sb-doped epitaxial (001) SnO2 thin films in order to determine the effect of Sb content on the electrical resistivity of the films. The lowest resistivity obtained for the Sb-doped epitaxial (001) SnO2 thin films prepared using ELAMOD with the ArF laser and 2 % Sb content was 2.5 × 10-3 Ω cm. The difference between the optimal Sb concentrations and resistivities of the films produced using either ELAMOD or conventional thermal MOD was discussed.

  2. Laser induced fluorescence study of the B-italic-tilde /sup 2/B/sub 2/. -->. X /sup 2/A/sub 2/ transition of the furan cation in a supersonic free jet expansion

    SciTech Connect

    Smith, R.S.; Anselment, M.; DiMauro, L.F.; Frye, J.M.; Sears, T.J.

    1987-10-15

    The first experimental observation of laser induced fluorescence from the furan cation, C/sub 4/H/sub 4/O/sup +/, is reported. The ion is formed in a supersonic free jet via a two photon ionization involving the 193 nm output of an ArF excimer laser. The B-italic-tilde..-->..X electronic transition is probed and vibrational assignments are presented for both states. Comparisons to the infrared, Raman, multiphoton ionization, and photoelectron spectrum of the parent molecule are made. The term value T/sub 00/ for the B-italic-tilde..-->..X electronic transition is located at 24 675 cm/sup -1/, which differs drastically with previously reported values from both experimental and theoretical investigations. These differences are discussed and probable explanations proposed. The lifetime of the vibrationless level of the B-italic-tilde state is measured to be 330 ns.

  3. Utilization of the excimer laser and a moving piezoelectric mirror to accomplish the customized contact lens ablation to correct high-order aberrations

    NASA Astrophysics Data System (ADS)

    de Matos, Luciana; Yasuoka, Fátima M. M.; Schor, Paulo; de Oliveira, Enos; Bagnato, Vanderlei S.; Carvalho, Luis A. V.

    2014-02-01

    The use of the Hartman-Shack sensor in ophthalmology allowed the identification of higher-order aberrations, which make possible the search for methods to correct them. Customized refractive surgery is one of the most successful methods, although there are patients which cannot be submitted to this surgery due to a variety of abnormal limiting factors such as cornea thickness and quantity of higher-order aberrations. Being this an irreversible process, the alternative is to develop a non-surgical method. This work proposes a method to obtain personalized contact lenses to correct high-order aberrations via the development of a customized ablation system using an excimer laser and a moving piezoelectric mirror. The process to produce such lenses consists of four steps. 1) The map of total aberrations of the patient's eye is measured by using an aberrometer with a Hartman-Shack sensor. 2) The measured aberration map is used to determine the maps for correction and related distribution of laser pulses for the ablation process with the excimer laser. 3) The lens production is performed following the same principle as customized refractive surgery. 4) The quality control of the lens is evaluated by two tests. 4.1) The lens is measured by a non-commercial lensometer, which is assembled specially for this measurement, as the ones commercially available are not capable of measuring asymmetric and irregular surfaces. 4.2) The evaluation of the lens-eye system is made using the aberrometer of the first step in order to verify the residual aberrations. Here, the lenses are ablated with a customized refractive surgery system.

  4. Improving Anti-Reflection MgF2 Thin Films by Laser Shock Peening and Investigation of its Laser Damage Threshold

    NASA Astrophysics Data System (ADS)

    Maleki, M. H.; Dizaji, H. R.; Ghorbani, A.

    2015-03-01

    This study is divided into two parts. In the first part, the influence of laser shock peening (LSP) on the surface properties of MgF2 thin films is studied. The MgF2 monolayer films with thickness of 100 nm were prepared on a BK7 glass substrate by physical vapor deposition (PVD). An ArF excimer laser with 110 mJ energy, 53 J/cm2 power density, 20 ns pulse duration and wavelength of 193 nm in TEM00 mode was used for the LSP experiments at different (20, 50, 90, and 120) number of the pulses. Transmittance of MgF2 thin films, before and after the LSP treatment, was evaluated by a spectrophotometer and the surface morphology of samples was examined by scanning electron microscope. In the second part, the effect of the LSP treatment on the laser induced damage threshold of a sample irradiated by 90 pulses of the ArF excimer laser was examined.

  5. Designing dual-trench alternating phase-shift masks for 140-nm and smaller features using 248-nm KrF and 193-nm ArF lithography

    NASA Astrophysics Data System (ADS)

    Petersen, John S.; Socha, Robert J.; Naderi, Alex R.; Baker, Catherine A.; Rizvi, Syed A.; Van Den Broeke, Douglas J.; Kachwala, Nishrin; Chen, J. Fung; Laidig, Thomas L.; Wampler, Kurt E.; Caldwell, Roger F.; Takeuchi, Susumu; Yamada, Yoshiro; Senoh, Takashi; McCallum, Martin

    1998-09-01

    One method for making the alternating phase-shift mask involves cutting a trench into the quartz of the mask using an anisotropic dry etch, followed by an isotropic etch to move the corners of the trench underneath the chrome to minimize problems caused by diffraction at the bottom corners of the phase-trench. This manufacturing method makes the addition of subresolution scattering bars and serifs problematic, because the amount of the undercut causes chrome lifting of these small features. Adding an additional anisotropically etched trench to both cut and uncut regions is helpful, but the etch does not move the trench corners under the chrome and result in a loss to intensity and image contrast. At 248 nm illumination and 4X magnification, our work shows that a combination of 240 nm dual-trench and 5 nm to 10 nm undercut produces images with equal intensity between shifted and unshifted regions without loss of image contrasts. This paper demonstrates optical proximity correction for doing 100 nm, 120 nm, 140 nm and 180 nm lines of varying pitch for a simple alternating phase-shift mask, with no dual-trench or undercut. Then the electromagnetic field simulator, TEMPEST, is used to find the best combination of dual-trench depth and amount of undercut for an alternating phase-shift mask. Phase measurement using 248 nm light and depth measurement of thirty-six unique combinations of dual-trench and phase-shift trench are shown. Based on modeling and experimental results, recommendations for making a fine tuned dual-trench 248 nm mask, as well as an extension of the dual-trench alternating phase-shift technique to 193 nm lithography, are made.

  6. Novel spin-coating technology for 248-nm/193-nm DUV lithography and low-k spin on dielectrics of 200-mm/300-mm wafers

    NASA Astrophysics Data System (ADS)

    Gurer, Emir; Zhong, Tom X.; Lewellen, John W.; Lee, Ed C.

    2000-06-01

    An alternative coating technology was developed for 248 nm/193 nm DUV lithography and low-k spin on dielectric (SOD) materials used in the interconnect area. This is a 300 mm enabling technology which overcomes turbulent flow limitations above 2000 rpm and it prevents 40 - 60% reduction on the process latitudes of evaporation-related variables, common to 300 mm conventional coaters. Our new coating technology is fully enclosed and it is capable of controlling the solvent concentration above the resist film dynamically in the gas phase. This feature allows a direct control of the evaporation mass transfer which determines the quality of the final resist profiles. Following process advantages are reported in this paper: (1) Demonstrated that final resist film thickness can be routinely varied by 4000 angstrom at a fixed drying spin speed, thus minimizing the impact of turbulence wall for 300 mm wafers. (2) Evaporation control allows wider range of useful thickness from a fixed viscosity material. (3) Latitudes of evaporation-related process variables is about 40% larger than that of a conventional coater. (4) Highly uniform films of 0.05% were obtained for 8800 angstrom target thickness with tighter wafer-wafer profile control because of the enclosed nature of the technology. (5) Dynamic evaporation control facilitates resist consumption minimization. Preliminary results indicate feasibility of a 0.4 cc process of record (POR) for a 200 mm substrate. (6) Lower COO due to demonstrated relative insensitivity to environmental variables, robust resist consumption minimization and superior process capabilities. (7) Improved planarization and gap fill properties for the new generation photoresist/low-k SOD materials deposited using this enclosed coating technology.

  7. A complete look at the multi-channel dissociation of propenal photoexcited at 193 nm: branching ratios and distributions of kinetic energy.

    PubMed

    Chaudhuri, Chanchal; Lee, Shih-Huang

    2011-04-28

    We observed fifteen photofragments upon photolysis of propenal (acrolein, CH(2)CHCHO) at 193 nm using photofragment translational spectroscopy and selective vacuum-ultraviolet (VUV) photoionization. All the photoproducts arise from nine primary and two secondary dissociation pathways. We measured distributions of kinetic energy of products and determined branching ratios of dissociation channels. Dissociation to CH(2)CHCO + H and CH(2)CH + HCO are two major primary channels with equivalent branching ratios of 33%. The CH(2)CHCO fragment spontaneously decomposes to CH(2)CH + CO. A proportion of primary products CH(2)CH from the fission of bond C-C of propenal further decompose to CHCH + H but secondary dissociation HCO → H + CO is negligibly small. Binary dissociation to CH(2)CH(2) (or CH(3)CH) + CO and concerted three-body dissociation to C(2)H(2) + CO + H(2) have equivalent branching ratios of 14%-15%. The other channels have individual branching ratios of ∼1%. The production of HCCO + CH(3) indicates the formation of intermediate methyl ketene (CH(3)CHCO) and the production of CH(2)CCH + OH and CH(2)CC + H(2)O indicate the formation of intermediate hydroxyl propadiene (CH(2)CCHOH) from isomerization of propenal. Distributions of kinetic energy release and dissociation mechanisms are discussed. This work provides a complete look and profound insight into the multi-channel dissociation mechanisms of propenal. The combination of a molecular beam apparatus and synchrotron VUV ionization allowed us to untangle the complex mechanisms of nine primary and two secondary dissociation channels. PMID:21423979

  8. Periodic structure with a periodicity of 2-3.5 μm on crystalline TiO2 induced by unpolarized KrF excimer lasers

    NASA Astrophysics Data System (ADS)

    He, Rong; Ma, Hongliang; Zheng, Jiahui; Han, Yongmei; Lu, Yuming; Cai, Chuanbing

    2016-08-01

    Laser-induced periodic surface structures (LIPSS) were processed on the TiO2 bulk surface under the irradiation of 248 nm unpolarized KrF excimer laser pulses in air. Spatial LIPSS periods ranging from 2 to 3.5 μm are ascribed to the capillary wave. These microstructures were analyzed at different laser pulse numbers with the laser energy from 192 to 164 mJ. The scanning electron microscopy results indicated eventually stripes that have been disrupted as the increase in the laser pulse numbers, which is reasonably explained by the energy accumulating effect. In addition, investigations were concentrated on the surface modifications at pre-focal plane, focal plane and post-focal plane in the same defocusing amount. Compared with condition at pre-focal plane, in addition to the plasma produced at target, the air was also breakdown for the situation of post-focal plane. So it was reasonable that stripes appeared at pre-focal plane but not at post-focal plane.

  9. Laser photochemical growth of amorphous silicon at low temperatures and comparison with thermal chemical vapor deposition

    SciTech Connect

    Eres, D.; Lowndes, D.H.; Geohegan, D.B.; Mashburn, D.N.

    1987-01-01

    Pulsed ArF (193 nm) excimer laser radiation has been used to dissociate disilane (Si/sub 2/H/sub 6/, resulting in photochemically controlled deposition of amorphous Si thin films. A high stability HeNe (6328 A) laser was used for precise in situ monitoring of film deposition rates, under varying deposition conditions. A helium window purge nearly eliminated Si film deposition on the chamber windows. With the excimer laser beam parallel to the substrate, deposition of amorphous Si can be controlled entirely by the photon fluence (negligible background thermal growth) at temperatures from room temperature up to /approximately/400/degree/C. Reasonable photolytic deposition rate (>1 A/sec) are combined with 'digital' control of film thickness (/approx gt/0.02 A/laser pulse). Activation energies of 1.50 (+-0.1) eV and 0.09 (+-0.02) eV were found for pyrolytic and photolytic deposition, respectively. 15 refs., 3 figs.

  10. Line Raman, Rayleigh, and laser-induced predissociation fluorescence technique for combustion with a tunable KrF excimer laser.

    PubMed

    Mansour, M S; Chen, Y C

    1996-07-20

    We have applied a line UV Raman, Rayleigh, and laser-induced predissociation fluorescence technique for measurement of turbulent hydrocarbon flames. The species concentration of CO(2), O(2), CO, N(2), CH(4), H(2)O, OH, and H(2) and the temperature are measured instantaneously and simultaneously along a line of 11.4 mm, from which the gradients with respect to mixture fraction and spatial direction are obtained. The technique has been successfully tested in a laminar premixed stoichiometric methane flame and a laminar hydrogen diffusion flame. In addition the technique has been tested in a highly turbulent rich premixed methane flame. The data show that the technique can be used to provide instantaneous measurements of local profiles that describe the local flame structure in highly turbulent flames. PMID:21102834

  11. Transformation of medical grade silicone rubber under Nd:YAG and excimer laser irradiation: First step towards a new miniaturized nerve electrode fabrication process

    NASA Astrophysics Data System (ADS)

    Dupas-Bruzek, C.; Robbe, O.; Addad, A.; Turrell, S.; Derozier, D.

    2009-08-01

    Medical grade silicone rubber, poly-dimethylsiloxane (PDMS) is a widely used biomaterial. Like for many polymers, its surface can be modified in order to change one or several of its properties which further allow this surface to be functionalized. Laser-induced surface modification of PDMS under ambient conditions is an easy and powerful method for the surface modification of PDMS without altering its bulk properties. In particular, we profit from both UV laser inducing surface modification and of UV laser micromachining to develop a first part of a new process aiming at increasing the number of contacts and tracks within the same electrode surface to improve the nerve selectivity of implantable self sizing spiral cuff electrodes. The second and last part of the process is to further immerse the engraved electrode in an autocatalytic Pt bath leading in a selective Pt metallization of the laser irradiated tracks and contacts and thus to a functionalized PDMS surface. In the present work, we describe the different physical and chemical transformations of a medical grade PDMS as a function of the UV laser and of the irradiation conditions used. We show that the ablation depths, chemical composition, structure and morphology vary with (i) the laser wavelength (using an excimer laser at 248 nm and a frequency-quadrupled Nd:YAG laser at 266 nm), (ii) the conditions of irradiation and (iii) the pulse duration. These different modified properties are expected to have a strong influence on the nucleation and growth rates of platinum which govern the adhesion and the thickness of the Pt layer on the electrodes and thus the DC resistance of tracks.

  12. Evaluation of some properties of dental ceramic as affected by different types of lasers and gamma radiations

    NASA Astrophysics Data System (ADS)

    Badr, Yehia; El'Khoudary, M. A.; Annan, Iman

    2004-05-01

    Dental ceramic:Duceram porcelain(Ducera,Dental-Gesellschaft mbH, FrankFurt, Germany) low fusing dental porcelain was subjected in this investigation to different types of laser radiations: a) Nd:YAG laser pulses o 8 ns, 200mJ/pulse for 5&10 minutes b) Tsonamy 70 fs laser pulses for 1 & 5 minutes c)193 nm Excimer laser pulses 6 &13 mJ/pulse for 5 & 10 minutes and finally d) 0.1, 0.3, 0.5 and 1 MRad of Gamma radiations using 10 samples for each type of radiation. Knoop hardness values of test samples were measured using a knoop hardness tester(KHN-Ernst Leitz Wetzlar Germany)showing increased hardness values for all test irradiated samples as compared with the control. Highest hardness value were recorded for Excimer laser 13 mJ/pulse-10 minutes(670kg/mm2 as compared with 410kg/mm2 for the control. On the other hand, the highest value for the transverse strength was obtained for Excimer laser 3.8mJ/pulse-10 minutes). To account for the structural changes occurring due to laser irradiations and leading to the detected here improvement in the mechanical properties we used several techniques which are known to be sensitive to any structural changes such as: x-ray diffraction, SE-Microscopy, FTIR & Raman spectroscopy. Our observations showed series of variations indicating good accordance in the introduced here results. A reasonable interpretation is given here for the effects and variations observed in our measurements and spectra as a result of both Gamma and Laser irradiation. Finally, the given here results indicated that Laser irradiation can be used as a powerful tool for improving the hardness and transverse strength of dental ceramic.

  13. Interaction of wide-band-gap single crystals with 248-nm excimer laser irradiation. IX. Photoinduced atomic desorption from cleaved NaCl(100) surfaces

    SciTech Connect

    Nwe, K.H.; Langford, S.C.; Dickinson, J.T.

    2005-07-01

    Neutral atomic sodium and chlorine emissions from cleaved, single-crystal NaCl(100) surfaces due to pulsed, 248-nm excimer laser irradiation have been characterized by time-resolved, quadrupole mass spectroscopy. At laser fluences below the threshold for optical breakdown, the resulting time-of-flight signals are consistent with particles emitted in thermal equilibrium with a laser-heated surface. Activation energy measurements made by varying the substrate temperature are consistent with F-H pair formation under UV excitation. By varying the laser fluence and estimating the effective surface temperature from the time-of-flight signals, additional activation energy measurements were made. The corresponding rate-limiting step is attributed to a thermally assisted, photoelectronic process involving atomic steps. Atomic force microscope images of surfaces irradiated at low fluences show monolayer islands that are created by the aggregation of material desorbed from steps. At somewhat higher fluences, monolayer pits due to F-center aggregation are also observed.

  14. Determining the CH3SO2 --> CH3 + SO2 barrier from methylsulfonyl chloride photodissociation at 193 nm using velocity map imaging.

    PubMed

    Ratliff, Britni J; Tang, Xiaonan; Butler, Laurie J; Szpunar, David E; Lau, Kai-Chung

    2009-07-28

    These imaging experiments study the formation of the methylsulfonyl radical, CH(3)SO(2), from the photodissociation of CH(3)SO(2)Cl at 193 nm and determine the energetic barrier for the radical's subsequent dissociation to CH(3) + SO(2). We first state-selectively detect the angular and recoil velocity distributions of the Cl((2)P(3/2)) and Cl((2)P(1/2)) atoms to further refine the distribution of internal energy partitioned to the momentum-matched CH(3)SO(2) radicals. The internal energy distribution of the radicals is bimodal, indicating that CH(3)SO(2) is formed in both the ground state and low-lying excited electronic states. All electronically excited CH(3)SO(2) radicals dissociate, while those formed in the ground electronic state have an internal energy distribution which spans the dissociation barrier to CH(3) + SO(2). We detect the recoil velocities of the energetically stable methylsulfonyl radicals with 118 nm photoionization. Comparison of the total recoil translational energy distribution for all radicals to the distribution obtained from the detection of stable radicals yields an onset for dissociation at a translational energy of 70+/-2 kcal/mol. This onset allows us to derive a CH(3)SO(2) --> CH(3) + SO(2) barrier height of 14+/-2 kcal/mol; this determination relies on the S-Cl bond dissociation energy, taken here as the CCSD(T) predicted energy of 65.6 kcal/mol. With 118 nm photoionization, we also detect the velocity distribution of the CH(3) radicals produced in this experiment. Using the velocity distributions of the SO(2) products from the dissociation of CH(3)SO(2) to CH(3) + SO(2) presented in the following paper, we show that our fastest detected methyl radicals are not from these radical dissociation channels, but rather from a primary S-CH(3) bond photofission channel in CH(3)SO(2)Cl. We also present critical points on the ground state potential energy surface of CH(3)SO(2) at the //CCSD(T)/aug-cc-pV(Q + d)ZCCSD(T)/6-311++G(2df,p) level

  15. Intersystem crossing and nonadiabatic product channels in the photodissociation of N{sub 2}O{sub 4} at 193 nm

    SciTech Connect

    Mueller, J.A.; Morton, M.L.; Curry, S.L.; Abbatt, J.P.D.; Butler, L.J.

    2000-06-01

    This paper presents velocity and angular distribution measurements of the products of N{sub 2}O{sub 4} photodissociated at 193 nm. The data show evidence for only N-N bond fission, with no significant branching to N-O bond fission or NO elimination products. The translational energy distribution of the N-N bond fission products is bimodal, indicating that at least two different NO{sub 2} + NO{sub 2} product channels contribute significantly to the observed products. Both product channels have an anisotropy parameter of {beta} = 1.7 {+-} 0.2. Using a Franck-Condon-like sudden analysis, the authors tentatively assign the two fragmentation channels observed as NO{sub 2}({tilde X}{sup 2}A{sub 1}) + NO{sub 2}(1{sup 4}B{sub 2}/1{sup 4}A{sub 2}) and NO{sub 2}({tilde X}{sup 2}A{sub 1}) + NO{sub 2}(2{sup 2}B{sub 2}). To further characterize the system the authors present ab initio calculations (at the level of configuration interaction with single excitations) of the relevant excites states of N{sub 2}O{sub 4}. The data considered together with the calculations suggest a model for the product branching in which there is spin-orbit coupling in the Franck-Condon region between the excited state, which has mixed singlet {pi}{pi}* and n{sigma}* character, and a state with {sup 3}{pi}{sigma}* character. Branching to the NO{sub 2}({tilde X}) + NO{sub 2}(1{sup 4}B{sub 2}/1{sup 4}A{sub 2}) channel occurs upon intersystem crossing to the triplet surface, and formation of the {pi}{pi}* diabatic products NO{sub 2}(X) + NO{sub 2}(2{sup 2}B{sub 2}) occurs from the singlet {pi}{pi}* state nonadiabatic dynamics. Finally, the authors note that the observed parallel photofragment anisotropy, unexpected for {pi}{pi}* electronic excitation of N{sub 2}O{sub 4}, likely results from vibronic coupling with a {sigma}{sigma}* electronic state.

  16. The thermodynamic response of soft biological tissues to pulsed ultraviolet laser irradiation.

    PubMed Central

    Venugopalan, V; Nishioka, N S; Mikić, B B

    1995-01-01

    The physical mechanisms that enable short pulses of high-intensity ultraviolet laser radiation to remove tissue, in a process known as laser ablation, remain obscure. The thermodynamic response of biological tissue to pulsed laser irradiation was investigated by measuring and subsequently analyzing the stress transients generated by pulsed argon fluorine (ArF, lambda = 193 nm) and krypton fluorine (KrF, lambda = 248 nm) excimer laser irradiation of porcine dermis using thin-film piezoelectric transducers. For radiant exposures that do not cause material removal, the stress transients are consistent with rapid thermal expansion of the tissue. At the threshold radiant exposure for ablation, the peak stress amplitude generated by 248 nm irradiation is more than an order of magnitude larger than that produced by 193 nm irradiation. For radiant exposures where material removal is achieved, the temporal structure of the stress transient indicates that the onset of material removal occurs during irradiation. In this regime, the variation of the peak compressive stress with radiant exposure is consistent with laser-induced rapid surface vaporization. For 193 nm irradiation, ionization of the ablated material occurs at even greater radiant exposures and is accompanied by a change in the variation of peak stress with radiant exposure consistent with a plasma-mediated ablation process. These results suggest that absorption of ultraviolet laser radiation by the extracellular matrix of tissue leads to decomposition of tissue on the time scale of the laser pulse. The difference in volumetric energy density at ablation threshold between the two wavelengths indicates that the larger stresses generated by 248 nm irradiation may facilitate the onset of material removal. However, once material removal is achieved, the stress measurements demonstrate that energy not directly responsible for target decomposition contributes to increasing the specific energy of the plume (and plasma

  17. F 2 excimer laser (157 nm) radiation modification and surface ablation of PHEMA hydrogels and the effects on bioactivity: Surface attachment and proliferation of human corneal epithelial cells

    NASA Astrophysics Data System (ADS)

    Zainuddin; Chirila, Traian V.; Barnard, Zeke; Watson, Gregory S.; Toh, Chiong; Blakey, Idriss; Whittaker, Andrew K.; Hill, David J. T.

    2011-02-01

    Physical and chemical changes at the surface of poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels modified by ablation with an F 2 excimer laser were investigated experimentally. An important observation was that only the outer exposed surface layers of the hydrogel were affected by the exposure to 157 nm radiation. The effect of the surface changes on the tendency of cells to adhere to the PHEMA was also investigated. A 0.5 cm 2 area of the hydrogel surfaces was exposed to laser irradiation at 157 nm to fluences of 0.8 and 4 J cm -2. The changes in surface topography were analysed by light microscopy and atomic force microscopy, while the surface chemistry was characterized by attenuated total reflection infrared and X-ray photoelectron spectroscopies. Cell-interfacial interactions were examined based on the proliferation of human corneal limbal epithelial (HLE) cells cultured on the laser-modified hydrogels, and on the unexposed hydrogels and tissue culture plastic for comparison. It was observed that the surface topography of laser-exposed hydrogels showed rippled patterns with a surface roughness increasing at the higher exposure dose. The changes in surface chemistry were affected not only by an indirect effect of hydrogen and hydroxyl radicals, formed by water photolysis, on the PHEMA, but also by the direct action of laser radiation on PHEMA if the surface layers of the gel become depleted of water. The laser treatment led to a change in the surface characteristics, with a lower concentration of ester side-chains and the formation of new oxygenated species at the surface. The surface also became more hydrophobic. Most importantly, the surface chemistry and the newly created surface topographical features were able to improve the attachment, spreading and growth of HLE cells.

  18. Temperature Distribution Simulation of the Human Eye Exposed to Laser Radiation

    PubMed Central

    Mirnezami, Seyyed Abbas; Rajaei Jafarabadi, Mahdi; Abrishami, Maryam

    2013-01-01

    Introduction: Human eye is a sensitive part of human body with no direct protection and due to its lack of protection against the external heat waves, studying the temperature distribution of heat waves on the human eye is of utmost importance. Various lasers are widely used in medical applications such as eye surgeries. The most significant issue in the eye surgeries with laser is estimation of temperature distribution and its increase in eye tissues due to the laser radiation intensity. Experimental and invasive methods to measure the eye temperature usually have high risks. Methods: In this paper, human eye has been modeled through studying the temperature distribution of three different laser radiations, using the finite element method. We simulated human eye under 1064 nm Neodymium-Doped Yttrium Aluminium Garnet (Nd: YAG) laser, 193 nm argon fluoride (ArF) excimer laser, and 1340 nm Neodymium doped Yttrium Aluminum Perovskite (Nd: YAP) laser radiation. Results: The results show that these radiations cause temperature rise in retina, lens and cornea region, which will in turn causes serious damages to the eye tissues. Conclusion: This simulation can be a useful tool to study and predict the temperature distribution in laser radiation on the human eye and evaluate the risk involved in using laser to perform surgery. PMID:25606327

  19. Raman Shifting a Tunable ArF Excimer Laser to Wavelengths of 190 to 240 nm With a Forced Convection Raman Cell

    NASA Technical Reports Server (NTRS)

    Balla, R. Jeffrey; Herring, G. C.

    2000-01-01

    Tunable radiation, at ultraviolet wavelengths, is produced by Raman shifting a modified 285-mJ ArF excimer laser. Multiple Stokes outputs are observed in H2, CH4, D2, N2, SF6, and CF4 (20, 22, 53, 21, 2.1, and 0.35 percent, respectively). Numbers in parentheses are the first Stokes energy conversion efficiencies. We can access 70 percent of the frequency range 42000-52000 cm (exp -1) (190-240 nm) with Stokes energies that vary from 0.2 microJoule to 58 mJ inside the Raman cell. By using 110 mJ of pump energy and D 2 , the tunable first Stokes energy varies over the 29-58 mJ range as the wavelength is tuned over the 204-206 nm range. Dependence on input energy, gas pressure, He mixture fraction, and circulation of the gas in the forced convection Raman cell is discussed; Stokes conversion is also discussed for laser repetition rates from 1 to 100 Hz. An empirical equation is given to determine whether forced convection can improve outputs for a given repetition rate.

  20. Effect of excimer laser annealing on a-InGaZnO thin-film transistors passivated by solution-processed hybrid passivation layers

    NASA Astrophysics Data System (ADS)

    Bermundo, Juan Paolo; Ishikawa, Yasuaki; Fujii, Mami N.; Nonaka, Toshiaki; Ishihara, Ryoichi; Ikenoue, Hiroshi; Uraoka, Yukiharu

    2016-01-01

    We demonstrate the use of excimer laser annealing (ELA) as a low temperature annealing alternative to anneal amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) passivated by a solution-processed hybrid passivation layer. Usually, a-IGZO is annealed using thermal annealing at high temperatures of up to 400 °C. As an alternative to high temperature thermal annealing, two types of ELA, XeCl (308 nm) and KrF (248 nm) ELA, are introduced. Both ELA types enhanced the electrical characteristics of a-IGZO TFTs leading to a mobility improvement of ~13 cm2 V-1 s-1 and small threshold voltage which varied from ~0-3 V. Furthermore, two-dimensional heat simulation using COMSOL Multiphysics was used to identify possible degradation sites, analyse laser heat localization, and confirm that the substrate temperature is below 50 °C. The two-dimensional heat simulation showed that the substrate temperature remained at very low temperatures, less than 30 °C, during ELA. This implies that any flexible material can be used as the substrate. These results demonstrate the large potential of ELA as a low temperature annealing alternative for already-passivated a-IGZO TFTs.

  1. Surface 3D Micro Free Forms: Multifunctional Microstructured Mesoporous α-Alumina by in Situ Slip Casting Using Excimer Laser Ablated Polycarbonate Molds.

    PubMed

    Rowthu, Sriharitha; Böhlen, Karl; Bowen, Paul; Hoffmann, Patrik

    2015-11-11

    Ceramic surface microstructuring is a rapidly growing field with a variety of applications in tribology, wetting, biology, and so on. However, there are limitations to large-area microstructuring and fabrication of three-dimensional (3D) micro free forms. Here, we present a route to obtain intricate surface structures through in situ slip casting using polydimethylsiloxane (PDMS) negative molds which are replicated from excimer laser ablated polycarbonate (PC) master molds. PC sheets are ablated with a nanosecond KrF (λ = 248 nm) excimer laser mask projection system to obtain micron-scale 3D surface features over a large area of up to 3 m(2). Complex surface structures that include 3D free forms such as 3D topography of Switzerland, shallow structures such as diffractive optical elements (60 nm step) and conical micropillars have been obtained. The samples are defect-free produced with thicknesses of up to 10 mm and 120 mm diameter. The drying process of the slip cast alumina slurry takes place as a one-dimensional process, through surface evaporation and water permeation through the PDMS membrane. This allows homogeneous one-dimensional shrinkage during the drying process, independent of the sample's lateral dimensions. A linear mass diffusion model has been proposed to predict and explain the drying process of these ceramic colloidal suspensions. The calculated drying time is linearly proportional to the height of the slurry and the thickness of the negatively structured PDMS and is validated by the experimental results. An experimentally observed optimum Sylgard PDMS thickness range of ∼400 μm to 1 mm has achieved the best quality microstructured green compacts. Further, the model predicts that the drying time is independent of the microstructured areas and was validated using experimental observations carried out with microstructured areas of 300 mm(2), 1200 mm(2), and 120 cm(2). Therefore, in principle, the structures can be further replicated in areas up

  2. RN12 and RN30 Epidote anlayses

    DOE Data Explorer

    Andrew Fowler

    2015-01-01

    Results for laser ablation measurement of reare earth elments and electron microprobe analysis of major elments in hydrothermal epidote. Laser ablation measurements were completed using an Agilent 7700 quadrupole ICP-MS coupled with 193nm Photon Instruments Excimer laser.

  3. Effects of beam quality of XeCl excimer laser on Raman conversion efficiency in H/sub 2/ *

    SciTech Connect

    Lou Qihong; Huo Yunshen; Dong Jinxing; Ding Zean; Wei Yunrong; Ding Aizhen; Gao Hongyi

    1988-10-01

    Stimulated Raman scattering (SRS) characteristics in high pressure H/sub 2/ are evaluated for pumping lasers with stable, plane-parallel and unstable laser resonators. By using a ring aperture to select the part of the laser beam with the best beam quality, Raman photon conversion efficiency of more than 90% was obtained with a pumping energy of 40 mJ.

  4. Nano-crystallization in ZnO-doped In2O3 thin films via excimer laser annealing for thin-film transistors

    NASA Astrophysics Data System (ADS)

    Fujii, Mami N.; Ishikawa, Yasuaki; Ishihara, Ryoichi; van der Cingel, Johan; Mofrad, Mohammad R. T.; Bermundo, Juan Paolo Soria; Kawashima, Emi; Tomai, Shigekazu; Yano, Koki; Uraoka, Yukiharu

    2016-06-01

    In a previous work, we reported the high field effect mobility of ZnO-doped In2O3 (IZO) thin film transistors (TFTs) irradiated by excimer laser annealing (ELA) [M. Fujii et al., Appl. Phys. Lett. 102, 122107 (2013)]. However, a deeper understanding of the effect of ELA on the IZO film characteristics based on crystallinity, carrier concentrations, and optical properties is needed to control localized carrier concentrations for fabricating self-aligned structures in the same oxide film and to adequately explain the physical characteristics. In the case of as-deposited IZO film used as the channel, a high carrier concentration due to a high density of oxygen vacancies was observed; such a film does not show the required TFT characteristics but can act as a conductive film. We achieved a decrease in the carrier concentration of IZO films by crystallization using ELA. This means that ELA can form localized conductive or semi-conductive areas on the IZO film. We confirmed that the reason for the carrier concentration decrease was the decrease of oxygen-deficient regions and film crystallization. The annealed IZO films showed nano-crystalline phase, and the temperature at the substrate was substantially less than the temperature limit for flexible films such as plastic, which is 50°C. This paves the way for the formation of self-aligned structures and separately formed conductive and semi-conductive regions in the same oxide film.

  5. Comparison of Immediate and 2-Year Outcomes between Excimer Laser-Assisted Angioplasty with Spot Stent and Primary Stenting in Intermediate to Long Femoropopliteal Disease

    PubMed Central

    Chou, Hsin-Hua; Chang, Shang-Hung; Tsai, Yueh-Ju; Hsieh, Chien-An; Cheng, Shih-Tsung; Yeh, Kuan-Hung; Chang, Hern-Jia; Ko, Yu-Lin; Huang, Hsuan-Li

    2013-01-01

    Background. To compare the clinical outcomes between excimer laser-assisted angioplasty (ELA) with spot stent (group A) and primary stenting (group B) in intermediate to long femoropopliteal disease. Methods. Outcomes of 105 patients totaling 119 legs treated with two different strategies were analyzed retrospectively in a prospectively maintained database. Results. Baseline characteristics were similar in both groups. Better angiographic results and lesser increase of serum C-reactive protein levels (0.60 ± 0.72 versus 2.98 ± 0.97 mg/dL, P < 0.001) after the intervention were obtained in Group B. Group A had inferior 1-year outcomes due to higher rate of binary restenosis (67% versus 32%, P = 0.001) and lower rate of primary patency (40% versus 58%, P = 0.039). Rates of amputation-free survival, target vessel revascularization, assisted primary patency, and stent fracture at 24 months were similar in both groups (80% versus 82%, P = 0.979, 65% versus 45%, P = 0.11, 78% versus 80%, P = 0.75 and 6.3% versus 6.8%, P = 0.71, resp.). Conclusion. Greater vascular inflammation after ELA with spot stent resulted in earlier restenosis and inferior 1-year clinical outcomes than primary stenting. This benefit was lost in the primary stenting group at 2 years due to late catch-up restenosis. Active surveillance with prompt intervention was required to maintain the vessel patency. PMID:24381515

  6. Preliminary results of tracked photorefractive keratectomy (T-PRK) for mild to moderate myopia with the autonomous technologies excimer laser at Cedars-Sinai Medical Center

    NASA Astrophysics Data System (ADS)

    Maguen, Ezra I.; Salz, James J.; Nesburn, Anthony B.

    1997-05-01

    Preliminary results of the correction of myopia up to -7.00 D by tracked photorefractive keratectomy (T-PRK) with a scanning and tracking excimer laser by Autonomous Technologies are discussed. 41 eyes participated (20 males). 28 eyes were evaluated one month postop. At epithelization day mean uncorrected vision was 20/45.3. At one month postop, 92.8 of eyes were 20/40 and 46.4% were 20/20. No eye was worse than 20/50. 75% of eyes were within +/- 0.5 D of emmetropia and 82% were within +/- 1.00 D of emmetropia. Eyes corrected for monovision were included. One eye lost 3 lines of best corrected vision, and had more than 1.00 D induced astigmatism due to a central corneal ulcer. Additional complications included symptomatic recurrent corneal erosions which were controlled with topical hypertonic saline. T-PRK appears to allow effective correction of low to moderate myopia. Further study will establish safety and efficacy of the procedure.

  7. Laser-assisted metalorganic molecular beam epitaxy of GaAs

    NASA Astrophysics Data System (ADS)

    Donnelly, V. M.; Tu, C. W.; Beggy, J. C.; McCrary, V. R.; Lamont, M. G.; Harris, T. D.; Baiocchi, F. A.; Farrow, R. C.

    1988-03-01

    We report preliminary studies of the growth of homoepitaxial GaAs by laser-assisted metalorganic molecular beam epitaxy, using triethylgallium (TEGa) and As4 sources and a 193 nm ArF excimer laser. Laser irradiation results in a high, selective-area growth rate at temperatures below 450 °C, where pyrolytic growth is very slow. The process is extremely efficient, with roughly unit probability for impinging TEGa molecules sticking and being dissociated by laser radiation to form GaAs. From the strong dependence on laser fluence, the growth enhancement process appears to be pyrolytic in nature (because of transient heating by the pulsed laser) and not photolytic. The cross section for photolysis must be at least ten times lower than the gas-phase value (9×10-18 cm2). The surface morphology of films grown at 400 °C is rough at threshold fluences (˜0.10 J/cm2), but becomes smooth at higher fluences (˜0.13 J/cm2). These regions with relatively smooth surfaces exhibit enhanced photoluminescence yields compared to areas receiving less intense laser radiation.

  8. New Applications of Lasers in Photobiology and Photochemistry

    NASA Astrophysics Data System (ADS)

    Badr, Y.; Kareim, M. A.

    2005-03-01

    Photonics spectra and optical medical diagnostic field for examination of biological tissues generally and human body specially cover many spectroscopic and laser technologies based on NIR spectroscopy, fluorescence and Raman spectroscopy, Optical coherent tomography (OCT), Confocal microscopy, Opto-acoustic tomography, photon correlation spectroscopy and imaging, and Speckle monitoring of biological flows. The recent achievements in light scattering and coherent light effects in tissues, and in the design of novel lasers and fiber optic techniques for examination of biological tissues are the real motive and the attracting factor for many labs to consider the mentioned above techniques. Our lab, as it contains most of these facilities, started to use these technologies since 1997 in several applications: 1. Applying a suitable setup for introducing exogenous DNA of pAB (with bar/ Gus gene) into cells of embryonic collie of Egyptian wheat based on 193 and 608 nm, 6 ns Excimer laser pulses introducing a modified procedure of Laser-Mediated gene transfer in Egyptian wheat Tridum Aestivum. 2. Applying laser technologies in early identification of abnormal tissues spectroscopically 3. We considered several types of tissues starting with breast cancer, which was subjected to intensive spectroscopic studies using NIR, MIR, FIR, Raman spectroscopy as well as photo-acoustic spectroscopy and imaging studies. Cell carcinoma was considered using Raman spectroscopy and a clear distinction between normal tissue before and after introduction of cell cancer as well as after treating of the tissues using PDT. 4. The application of 193 nm Excimer laser pulse to study photolysis of Acetone using time resolved spectroscopy. A locally designed setup was used to study the effect of delay time (1μs, 2μs, …., 10μs,….,50μs) on the CO and CH3 radicals resulting from the photolysis.

  9. a Theoretical Study of the Kinetic Processes in a High-Power Xenon Chloride Excimer Laser Oscillator Driven by a Long Transmission Line Pulse Forming Network.

    NASA Astrophysics Data System (ADS)

    Wang, Yuh-Shuh

    1982-03-01

    The avalanche/self-sustained discharge rare gas halide (RGH) excimer lasers driven by a transmission line type pulse forming network (PFN) belong to a novel class of discharge pumped gas lasers operating in the visible and ultraviolet wavelengths efficiently. The kinetics in this class of lasers, however, has not yet been fully understood. Therefore, it seems essential at this point to study the characteristics of the discharge plasma in such a device and determine the major energy flow paths in the active media before one attempts to optimize the operating conditions or deduce the scaling rules. The work presented here is the theoretical modeling of the discharge pumped XeCl laser driven by a long transmission line (two way transit time, 200 nsec). The mathematical formulation consisting of the rate equations, the temperature equation, the circuit equation, and the Boltzmann equation governing the velocity and energy distributions of the free electrons is developed under the assumptions that the applied electric field strength is spatially uniform and the number densities of all important chemical species are spatially homogeneous in the discharge volume. These coupled non-linear differential equations are solved numerically by using the GBS extrapolation method simultaneously with the time evolution of the electron mole fraction during the transient discharge. The time-dependent electron velocity and energy distribution functions are obtained from the numerical solutions of the Boltzmann equation, with all elastic (including electron-electron), inelastic, attachment, recombination, and ionization collisions included, by a self-consistent iteration technique. The kinetic reactions involved in the XeCl laser using Ne/Xe/HCl and He/Xe/HCl mixtures are comprehensively examined. The results of this study reveal that the new processes. e + XeCl('*) (--->) Xe('*) + Cl('-),. e + XeCl (--->) Xe + Cl('-) or Xe + Cl + e,. are important and have to be included in the model

  10. Interaction of Wide-Band-Gap Single Crystals with 248-nm Excimer Laser Irradiation: X. Laser-Induced Near-Surface Absorption in Single-Crystal NaCl

    SciTech Connect

    Nwe, K H.; Langford, Stephen C.; Dickinson, J T.; Hess, Wayne P.

    2005-02-15

    Ultraviolet laser-induced desorption of neutral atoms and molecules from nominally transparent, ionic materials can yield particle velocities consistent with surface temperatures of a few thousand Kelvin, even in the absence of visible surface damage. The origin of the laser required for this surface heating has been often overlooked. In this work, we report simultaneous neutral emission and laser transmission measurements on single crystal NaCl exposed to 248-nm excimer laser radiation. As much as 20% of the incident radiation at 248 nm must be absorbed in the near surface region to account for the observed particle velocities. We show that the laser absorption grows from low values over several pulses and saturates at values sufficient to account for the surface temperatures required to explain the observed particle velocity distributions. The growth of absorption in these early pulses is accompanied by a corresponding increase in the emission intensities. Diffuse reflectance spectra acquired after exposure suggest that near surface V-type centers are responsible for most of the absorption at 248 nm in single crystal NaCl.

  11. Interaction of wide-band-gap single crystals with 248-nm excimer laser irradiation. X. Laser-induced near-surface absorption in single-crystal NaCl

    SciTech Connect

    Nwe, K.H.; Langford, S.C.; Dickinson, J.T.; Hess, W.P.

    2005-02-15

    Ultraviolet laser-induced desorption of neutral atoms and molecules from nominally transparent, ionic materials can yield particle velocities consistent with surface temperatures of a few thousand kelvin even in the absence of visible surface damage. The origin of the laser absorption required for this surface heating has been often overlooked. In this work, we report simultaneous neutral emission and laser transmission measurements on single-crystal NaCl exposed to 248-nm excimer laser radiation. As much as 20% of the incident radiation at 248 nm must be absorbed in the near-surface region to account for the observed particle velocities. We show that the laser absorption grows from low values over several pulses and saturates at values sufficient to account for the surface temperatures required to explain the observed particle velocity distributions. The growth of absorption in these early pulses is accompanied by a corresponding increase in the emission intensities. The diffuse reflectance spectra acquired after exposure suggest that near-surface V-type centers are responsible for most of the absorption at 248 nm in single-crystal NaCl.

  12. Simultaneous fluorescence and breakdown spectroscopy of fresh and aging transformer oil immersed in paper using ArF excimer laser

    NASA Astrophysics Data System (ADS)

    Parvin, P.; Shoursheini, S. Z.; Khalilinejad, F.; Bavali, A.; Moshgel Gosha, M.; Mansouri, B.

    2012-11-01

    HV transformers are taken into account as the heart of the power distribution system. The on-line monitoring based on the oil analysis offers a rapid diagnostic technique to detect the probable faults. In fact, the transformer malfunctions can be detected using UV laser spectroscopic methods. Here, a novel technique is presented based on simultaneous laser induced fluorescence (LIF) and laser induced breakdown (LIB) spectroscopy for hyper sensitive identification of the oil degradation. Oil is mainly degraded due to the internal transformer faults such as overheating and partial discharge. The spectroscopic characteristics of oil in paper substrate were obtained due to ArF laser irradiation. It was shown that the amplitude of fluorescence signal increases when the oil suffers aging and degradation. A couple of additional characteristic carbon and Hα emissions appear in the corresponding breakdown spectra too.

  13. Removal of Metal-Oxide Layers Formed on Stainless and Carbon Steel Surfaces by Excimer Laser Irradiation in Various Atmospheres

    SciTech Connect

    Kameo, Yutaka; Nakashima, Mikio; Hirabayashi, Takakuni

    2002-02-15

    To apply the laser ablation technique for decontamination of metal wastes contaminated with radioactive nuclides, the effect of irradiation atmospheres on removal of oxide layers on steel surfaces by laser ablation was studied. Based on the assumption that the absorption of laser light follows the Lambert-Beer law, ablation parameters, such as absorption length and threshold fluence for ablation, of sintered Fe{sub 2}O{sub 3} and stainless and carbon steels were measured in He, O{sub 2}, Kr, or SF{sub 6} atmospheres. The results indicated that SF{sub 6} was the most effective gas of all irradiation atmospheres studied for the exclusive removal of oxide layers formed on stainless and carbon steel samples in high-temperature pressurized water. Secondary ion mass spectroscopic measurement and scanning electron microscopic observation confirmed that no oxide layer existed on the steel samples after the exclusive removal with laser irradiation.

  14. Surface modifications of Kapton and cured polyimide films by ArF excimer laser: applications to imagewise wetting and metallization

    NASA Astrophysics Data System (ADS)

    Hiraoka, Hiroyuki; Lazare, Sylvain

    1990-12-01

    Polymer surfaces of certain kinds, particularly polyimide, become highly hydrophilic upon irradiation by deep UV or UV laser in air. Unlike UV lamp light, laser exposure in air is extremely efficient in making polymer surfaces hydrophilic and wettable with aqueous solutions or similar liquids. The change in chemical nature of the polymer surfaces upon laser and deep UV irradiation is studied by contact-angle measurements in both advancing and receding modes. The results are compared with those of PPQ, PPES, polystyrene and PMMA. Under UV irradiation in air, polymer surfaces become highly hydrophilic, resulting in a decrease of the contact angles in both modes. Laser exposure in air makes the surfaces highly hydrophilic and wettable by both photo-induced reactions and debris/roughness formation. Water spray reduces the hysteresis by removing the debris, but the polymers still keep certain roughness and hydrophilicity on the remaining surfaces. Laser irradiation makes imagewise wetting possible with polyimide films at a low fluence. Direct imagewise metallization is also observed with polyimides and PPQ films. The laser-exposed areas cannot have electrically conducting metal films deposited on them while on unexposed surfaces uniform metal film deposition took place. Although the mechanism is still not clear, oxygen RIE is found to be possible in the exposed, non-conducting part, while galvanic plating was carried out on unexposed, conducting surfaces with a Au-Pd metallization.

  15. Hydrogen Migration and Vinylidene Pathway for Formation of Methane in the 193 nm Photodissociation of Propene: CH3CH=CH2 and CD3CD=CD2

    NASA Technical Reports Server (NTRS)

    Zhao, Yi-Lei; Laufer, Allan H.; Halpern, Joshua B.; Fahr, Askar

    2007-01-01

    Photodissociation channels and the final product yields from the 193 nm photolysis of propene-h6 (CH2=CHCH3) and propene-d6 (CD2=CDCD3) have been investigated, employing gas chromatography, mass spectroscopy, and flame ionization (GC/MS/FID) detection methods. The yields of methane as well as butadiene relative to ethane show considerable variations when propene-h6 or propene-d6 are photolyzed. This suggests significant variances in the relative importance of primary photolytic processes and/or secondary radical reactions, occurring subsequent to the photolysis. Theoretical calculations suggest the potential occurrence of an intramolecular dissociation through a mechanism involving vinylidene formation, accompanied by an ethylenic H-migration through the pi-orbitals. This process affects the final yields of methane-h4 versus methane-d4 with respect to other products. The product yields from previous studies of the 193 nm photolysis of methyl vinyl ketone-h6 and -d6 (CH2=CHCOCH3, CD2=CDCOCD3), alternative precursors for generating methyl and vinyl radicals, are compared with the current results for propene.

  16. Excimer laser activation of ultra-shallow junctions in doped Si: Modeling, experiments and real time process monitoring

    NASA Astrophysics Data System (ADS)

    Semmar, Nadjib; Darif, Mohamed; Millon, Eric; Petit, Agnès; Etienne, Hasnaa; Delaporte, Philippe

    2012-07-01

    This work concerns the ALDIP (Laser Activation of Doping agents Implanted by Plasma immersion) project that was a successful collaboration with Ion Beam Services (IBS) corporation, the "Lasers, Plasmas and Photonic Processes" (LP3) laboratory and the GREMI laboratory. The aim of this work is to control the melted thickness (i.e. junction thickness in the range 10-100 nm) by the Real Time Reflectivity (TRR) monitoring during the Laser Thermal Processing (LTP). The LTP is achieved by using a KrF laser beam (248 nm, 27 ns) with a homogeneous 'Top-Hat' space distribution to induce a selective melting and the resolidification of the doped Si:B samples on few nanometers. This recrystallization is conducted here after the pre-amorphisation process resulting from the ionic implantation of Si (PIII IBS implanter). Thus, all the studied samples are partially amorphized and boron doped. TRR method allows the accurate evaluation of the melting threshold, the duration of the melting phase, and the maximum melted thickness. Obtained results versus laser fluence are shown in the new case of under vacuum treatment. In order to calibrate the TRR method (to determine the intensity and the profile of the TRR signal versus the melting depth), we have used the secondary ion mass spectrometry (TOF-SIMS) analysis. This technique gives the doping agents profile versus the depth before and after LTP and confirms also the melting kinetics from TRR results.

  17. Surface analysis of the selective excimer laser patterning of a thin PEDOT:PSS film on flexible polymer films

    NASA Astrophysics Data System (ADS)

    Schaubroeck, David; De Smet, Jelle; Willems, Wouter; Cools, Pieter; De Geyter, Nathalie; Morent, Rino; De Smet, Herbert; Van Steenbeerge, Geert

    2016-07-01

    Fast patterning of highly conductive polymers like PEDOT:PSS (poly (3,4-ethylene dioxythiophene): polystyrene sulfonate) with lasers can contribute to the development of industrial production of liquid crystal displays on polymer foils. In this article, the selective UV laser patterning of a PEDOT:PSS film on flexible polymer films is investigated. Based on their optical properties, three polymer films are investigated: polyethylene terephthalate (PET), polymethyl methacrylate (PMMA) and cellulose triacetate (TAC). Ablation parameters for a 110 nm PEDOT:PSS film on these polymer films are optimized. A detailed study of the crater depth, topography and surface composition are provided using optical profilometry, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The electrical insulation of the lines is measured and correlated to the crater analyses for different laser settings. Finally, potential ablation parameters for each of the polymer films are derived.

  18. Cold laser technique for cell surgery

    NASA Astrophysics Data System (ADS)

    Palanker, Daniel V.; Ohad, Shoshanit; Lewis, Aaron; Laufer, Neri

    1992-08-01

    A new cell surgery technique has been developed to produce well-defined alterations in cells and tissues without detectable heating and/or other structural damage in the surroundings. The technique involves the use of a 193 nm argon fluoride excimer laser which is guided through a glass pipette filled with a positive air pressure. To demonstrate the method holes were drilled in the zona pellucida of mouse oocytes. The diameter of the drilled hole was determined by the pipette tip size, and its depth by an energy emitted per pulse and number of pulses. Scanning electron microscopy of the drilled mouse oocytes showed uniform, round, well circumscribed holes with sharp edges. Oocytes that had their zona pellucida drilled with this new method fertilized in vitro and developed to the blastocyst stage in a rate similar to that of control group. These results demonstrate the non-perturbing nature of this cold laser microsurgical procedure. In addition to the extension of our results for clinical in vitro fertilization purposes, such as enhancement of fertilization and embryo biopsy, there are wide ranging possible uses of our method in fundamental and applied investigations that require sub-micron accuracy in cellular alteration.

  19. Pulsed laser deposition of pepsin thin films

    NASA Astrophysics Data System (ADS)

    Kecskeméti, G.; Kresz, N.; Smausz, T.; Hopp, B.; Nógrádi, A.

    2005-07-01

    Pulsed laser deposition (PLD) of organic and biological thin films has been extensively studied due to its importance in medical applications among others. Our investigations and results on PLD of a digestion catalyzing enzyme, pepsin, are presented. Targets pressed from pepsin powder were ablated with pulses of an ArF excimer laser ( λ = 193 nm, FWHM = 30 ns), the applied fluence was varied between 0.24 and 5.1 J/cm 2. The pressure in the PLD chamber was 2.7 × 10 -3 Pa. The thin layers were deposited onto glass and KBr substrates. Our IR spectroscopic measurements proved that the chemical composition of deposited thin films is similar to that of the target material deposited at 0.5 and 1.3 J/cm 2. The protein digesting capacity of the transferred pepsin was tested by adapting a modified "protein cube" method. Dissolution of the ovalbumin sections proved that the deposited layers consisted of catalytically active pepsin.

  20. Excimer laser phototherapeutic keratectomy in eyes with anterior corneal dystrophies: preoperative and postoperative ultrasound biomicroscopic examination and short-term clinical outcomes with and without an antihyperopia treatment.

    PubMed Central

    Rapuano, Christopher J

    2003-01-01

    PURPOSE: To evaluate the use of high-frequency ultrasound biomicroscopy (UBM) in determining the depth of corneal pathology in eyes undergoing excimer laser phototherapeutic keratectomy (PTK) for primary or recurrent anterior stromal corneal dystrophies. Corneal clarity, visual acuity and refractive changes in eyes with and without an antihyperopia treatment were also analyzed. METHODS: Twenty eyes of 14 patients with anterior stromal corneal dystrophies were treated with PTK. Eyes were evaluated preoperatively and 6 to 8 weeks postoperatively with slit-lamp biomicroscopy, manifest refraction, keratometry, computerized corneal topography, ultrasound pachymetry, and UBM. RESULTS: Nineteen of 20 corneas (95%) had greatly improved corneal clarity after PTK. Mean uncorrected Snellen vision improved from 20/102 to 20/69 and best corrected vision improved from 20/62 to 20/38. Nine eyes (45%) improved 2 or more lines of uncorrected vision, and 13 eyes (65%) improved 2 or more lines of best corrected vision. Mean change in spherical equivalent was just -0.92 diopters (D); however, the range was large (-13 to +3.88 D). UBM measurement of central corneal pathology did not correlate with the actual PTK ablation depth (P = .07). The amount of antihyperopia treatment did not correlate with changes in manifest refraction spherical equivalent, keratometry, or computerized corneal topography readings, but did correlate with length of time until corneal reepithelialization after PTK (P = .003). CONCLUSIONS: PTK resulted in improvements in corneal clarity and visual acuity in most patients with superficial corneal stromal dystrophies. UBM was not an effective tool to accurately measure the depth of corneal pathology preoperatively. The combined approach of minimizing ablation depth and selective use of an antihyperopia treatment resulted in minimal mean change in spherical equivalent; however, the range was large. PTK is a very good minimally invasive technique to improve vision in