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Sample records for microwave plasma-enhanced chemical

  1. Robust Ultralow-k Dielectric (Fluorocarbon) Deposition by Microwave Plasma-Enhanced Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Kikuchi, Yoshiyuki; Miyatani, Kotaro; Kobayashi, Yasuo; Kawamura, Kohei; Nemoto, Takenao; Nakamura, Masahiro; Matsumoto, Hirokazu; Ito, Azumi; Shirotori, Akihide; Nozawa, Toshihisa; Matsuoka, Takaaki

    2012-05-01

    A robust fluorocarbon film was successfully deposited on a substrate at a temperature above 400 °C by the new microwave plasma-enhanced chemical vapor deposition (MWPE-CVD) method using the linear C5F8 precursor instead of a conventional cyclic C5F8 one. The fluorocarbon performed keeping the dielectric constant low as a value of 2.25 by controlling the molecular structure forming cross-linked poly(tetrafluoroethylene) (PTFE) chains with configurational carbon atoms. The novel fluorocarbon demonstrates less fluorine degassing at an elevated temperature, with high mechanical strength and without degradation of adhesion of the fluorocarbon film to SiCN and SiOx stacked films after thermal stress at 400 °C and 1 atm N2 for 1 h. Consequently, this robust fluorocarbon film is considered a promising candidate for general porous silicon materials with applications to practical integration processes as an interlayer dielectric.

  2. Carbon nanowalls grown by microwave plasma enhanced chemical vapor deposition during the carbonization of polyacrylonitrile fibers

    SciTech Connect

    Li Jiangling; Su Shi; Kundrat, Vojtech; Abbot, Andrew M.; Ye, Haitao; Zhou Lei; Mushtaq, Fajer; Ouyang Defang; James, David; Roberts, Darren

    2013-01-14

    We used microwave plasma enhanced chemical vapor deposition (MPECVD) to carbonize an electrospun polyacrylonitrile (PAN) precursor to form carbon fibers. Scanning electron microscopy, Raman spectroscopy, and Fourier transform infrared spectroscopy were used to characterize the fibers at different evolution stages. It was found that MPECVD-carbonized PAN fibers do not exhibit any significant change in the fiber diameter, whilst conventionally carbonized PAN fibers show a 33% reduction in the fiber diameter. An additional coating of carbon nanowalls (CNWs) was formed on the surface of the carbonized PAN fibers during the MPECVD process without the assistance of any metallic catalysts. The result presented here may have a potential to develop a novel, economical, and straightforward approach towards the mass production of carbon fibrous materials containing CNWs.

  3. Synthesis of few-layer graphene via microwave plasma-enhanced chemical vapour deposition.

    PubMed

    Malesevic, Alexander; Vitchev, Roumen; Schouteden, Koen; Volodin, Alexander; Zhang, Liang; Tendeloo, Gustaaf Van; Vanhulsel, Annick; Haesendonck, Chris Van

    2008-07-30

    If graphene is ever going to live up to the promises of future nanoelectronic devices, an easy and cheap route for mass production is an essential requirement. A way to extend the capabilities of plasma-enhanced chemical vapour deposition to the synthesis of freestanding few-layer graphene is presented. Micrometre-wide flakes consisting of four to six atomic layers of stacked graphene sheets have been synthesized by controlled recombination of carbon radicals in a microwave plasma. A simple and highly reproducible technique is essential, since the resulting flakes can be synthesized without the need for a catalyst on the surface of any substrate that withstands elevated temperatures up to 700 °C. A thorough structural analysis of the flakes is performed with electron microscopy, x-ray diffraction, Raman spectroscopy and scanning tunnelling microscopy. The resulting graphene flakes are aligned vertically to the substrate surface and grow according to a three-step process, as revealed by the combined analysis of electron microscopy and x-ray photoelectron spectroscopy.

  4. Growth mechanism of carbon nanotubes grown by microwave-plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Okai, M.; Muneyoshi, T.; Yaguchi, T.; Sasaki, S.; Shinohara, H.

    2001-11-01

    To understand the growth mechanism of carbon nanotubes, we have investigated the initial stage of carbon nanotube growth by microwave-plasma-enhanced CVD on a metal substrate. Metal droplets with diameters of 20-180 nm appeared on the substrate surface after plasma cleaning. These metal droplets operate as a catalyst for the growth of carbon nanotubes. The grown nanotubes had a piled-cone structure with metal particles at the top. The diameters of the carbon nanotubes ranged from 60 to 80 nm and the metal particles at the top were the same sizes.

  5. Structure of carbon nanotubes grown by microwave-plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Okai, M.; Muneyoshi, T.; Yaguchi, T.; Sasaki, S.

    2000-11-01

    Carbon nanotubes grown on a Ni substrate and an Fe-Ni-Cr alloy substrate by plasma-enhanced chemical vapor deposition were investigated by transmission electron microscope (TEM) and energy dispersive x-ray (EDX) analysis. TEM showed that the nanotubes on both substrates have a piled-cone structure with metal particles on top which determine the diameter of the nanotubes. Their diameter ranges from 60 to 80 nm. Moreover, EDX showed that the metal particles are composed of Ni when the nanotubes are grown on Ni substrate and of Fe and Ni in the case of the Fe-Ni-Cr alloy substrate.

  6. Microwave plasma enhanced chemical vapor deposition of nanocrystalline diamond films by bias-enhanced nucleation and bias-enhanced growth

    SciTech Connect

    Chu, Yueh-Chieh; Tzeng, Yonhua; Auciello, Orlando

    2014-01-14

    Effects of biasing voltage-current relationship on microwave plasma enhanced chemical vapor deposition of ultrananocrystalline diamond (UNCD) films on (100) silicon in hydrogen diluted methane by bias-enhanced nucleation and bias-enhanced growth processes are reported. Three biasing methods are applied to study their effects on nucleation, growth, and microstructures of deposited UNCD films. Method A employs 320 mA constant biasing current and a negative biasing voltage decreasing from −490 V to −375 V for silicon substrates pre-heated to 800 °C. Method B employs 400 mA constant biasing current and a decreasing negative biasing voltage from −375 V to −390 V for silicon pre-heated to 900 °C. Method C employs −350 V constant biasing voltage and an increasing biasing current up to 400 mA for silicon pre-heated to 800 °C. UNCD nanopillars, merged clusters, and dense films with smooth surface morphology are deposited by the biasing methods A, B, and C, respectively. Effects of ion energy and flux controlled by the biasing voltage and current, respectively, on nucleation, growth, microstructures, surface morphologies, and UNCD contents are confirmed by scanning electron microscopy, high-resolution transmission-electron-microscopy, and UV Raman scattering.

  7. Coating of diamond-like carbon nanofilm on alumina by microwave plasma enhanced chemical vapor deposition process.

    PubMed

    Rattanasatien, Chotiwan; Tonanon, Nattaporn; Bhanthumnavin, Worawan; Paosawatyanyong, Boonchoat

    2012-01-01

    Diamond-like carbon (DLC) nanofilms with thickness varied from under one hundred to a few hundred nanometers have been successfully deposited on alumina substrates by microwave plasma enhanced chemical vapor deposition (MW-PECVD) process. To obtain dense continuous DLC nanofilm coating over the entire sample surface, alumina substrates were pre-treated to enhance the nucleation density. Raman spectra of DLC films on samples showed distinct diamond peak at around 1332 cm(-1), and the broad band of amorphous carbon phase at around 1550 cm(-1). Full width at half maximum height (FWHM) values indicated good formation of diamond phase in all films. The result of nano-indentation test show that the hardness of alumina samples increase from 7.3 +/- 2.0 GPa in uncoated samples to 15.8 +/- 4.5-52.2 +/- 2.1 GPa in samples coated with DLC depending on the process conditions. It is observed that the hardness values are still in good range although the thickness of the films is less than a hundred nanometer.

  8. Reaction Gas Ratio Effect on the Growth of a Diamond Film Using Microwave Plasma-Enhanced Chemical Vapor Deposition.

    PubMed

    Joung, Y H; Kang, F S; Lee, S; Kang, H; Choi, W S; Choi, Y K; Song, B S; Lee, J; Hong, B

    2016-05-01

    In this study, diamond films were prepared using the microwave plasma-enhanced chemical vapor deposition (PECVD) system, which included a DC bias system to enhance the nucleation of the films. The films were synthesized on Si wafers with different ratios of methane (CH4) and hydrogen (H2) gases. We have studied the effects of the CH4-to-H2 ratio on the structural and optical properties of diamond films. The thickness and surface profile of the films were characterized via field emission scanning electron microscopy (FE-SEM). Raman was used to investigate the structural properties of the diamond films. The refractive indexes as functions of the CH4-to-H2 ratio were measured using an ellipsometer. The FE-SEM analysis showed that the 3 and 5 sccm CH4 created diamond films. The Raman analysis indicated that a nanocrystalline diamond film was formed at 3 sccm; a general diamond film, at 5 sccm; and films similar to the a-C:H film, at 7 sccm. The ellipsometer measurement showed that the refractive index of the synthesized diamond film was around 2.42 at 3 sccm. This value decreased as the CH4 volume increased.

  9. Synthesis of thin films in boron-carbon-nitrogen ternary system by microwave plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Kukreja, Ratandeep Singh

    The Boron Carbon Nitorgen (B-C-N) ternary system includes materials with exceptional properties such as wide band gap, excellent thermal conductivity, high bulk modulus, extreme hardness and transparency in the optical and UV range that find application in most fields ranging from micro-electronics, bio-sensors, and cutting tools to materials for space age technology. Interesting materials that belong to the B-C-N ternary system include Carbon nano-tubes, Boron Carbide, Boron Carbon Nitride (B-CN), hexagonal Boron Nitride ( h-BN), cubic Boron Nitride (c-BN), Diamond and beta Carbon Nitride (beta-C3N4). Synthesis of these materials requires precisely controlled and energetically favorable conditions. Chemical vapor deposition is widely used technique for deposition of thin films of ceramics, metals and metal-organic compounds. Microwave plasma enhanced chemical vapor deposition (MPECVD) is especially interesting because of its ability to deposit materials that are meta-stable under the deposition conditions, for e.g. diamond. In the present study, attempt has been made to synthesize beta-carbon nitride (beta-C3N4) and cubic-Boron Nitride (c-BN) thin films by MPECVD. Also included is the investigation of dependence of residual stress and thermal conductivity of the diamond thin films, deposited by MPECVD, on substrate pre-treatment and deposition temperature. Si incorporated CNx thin films are synthesized and characterized while attempting to deposit beta-C3N4 thin films on Si substrates using Methane (CH4), Nitrogen (N2), and Hydrogen (H2). It is shown that the composition and morphology of Si incorporated CNx thin film can be tailored by controlling the sequence of introduction of the precursor gases in the plasma chamber. Greater than 100mum size hexagonal crystals of N-Si-C are deposited when Nitrogen precursor is introduced first while agglomerates of nano-meter range graphitic needles of C-Si-N are deposited when Carbon precursor is introduced first in the

  10. Plasma-enhanced microwave solid-state synthesis of cadmium sulfide: reaction mechanism and optical properties.

    PubMed

    Du, Ke-zhao; Chaturvedi, Apoorva; Wang, Xing-zhi; Zhao, Yi; Zhang, Ke-ke; Iqbal Bakti Utama, M; Hu, Peng; Jiang, Hui; Xiong, Qi-hua; Kloc, Christian

    2015-08-14

    CdS synthesis by plasma-enhanced microwave physical vapor transport (PMPVT) has been developed in this work. The photoluminescence (PL), absorbance, Raman spectra and the mechanism of CdS crystal growth have been investigated. Furthermore, plasma-enhanced microwave chemical vapour transport (PMCVT) synthesis of CdS with additional chemical transport agents has been explored. In addition, other II-VI chalcogenides were also synthesized by PMPVT.

  11. Effect of Gas Sources on the Deposition of Nano-Crystalline Diamond Films Prepared by Microwave Plasma Enhanced Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Weng, Jun; Xiong, Liwei; Wang, Jianhua; Man, Weidong; Chen, Guanhu

    2010-12-01

    Nano-crystalline diamond (NCD) films were deposited on silicon substrates by a microwave plasma enhanced chemical vapor deposition (MPCVD) reactor in C2H5OH/H2 and CH4/H2/O2 systems, respectively, with a constant ratio of carbon/hydrogen/oxygen. By means of atomic force microscopy (AFM) and X-ray diffraction (XRD), it was shown that the NCD films deposited in the C2H5OH/H2 system possesses more uniform surface than that deposited in the CH4/H2/O2 system. Results from micro-Raman spectroscopy revealed that the quality of the NCD films was different even though the plasmas in the two systems contain exactly the same proportion of elements. In order to explain this phenomenon, the bond energy of forming OH groups, energy distraction in plasma and the deposition process of NCD films were studied. The experimental results and discussion indicate that for a same ratio of carbon/hydrogen/oxygen, the C2H5OH/H2 plasma was beneficial to deposit high quality NCD films with smaller average grain size and lower surface roughness.

  12. Diamond nucleation on unscratched silicon substrates coated with various non-diamond carbon films by microwave plasma-enhanced chemical vapor deposition

    SciTech Connect

    Feng, Z. ); Brewer, M.A. ); Komvopoulos, K. ); Brown, I.G. ); Bogy, D.B. )

    1995-01-01

    The efficacy of various non-diamond carbon films as precursors for diamond nucleation on unscratched silicon substrates was investigated with a conventional microwave plasma-enhanced chemical vapor deposition system. Silicon substrates were partially coated with various carbonaceous substances such as clusters consisting of a mixture of C[sub 60] and C[sub 70], evaporated films of carbon and pure C[sub 70], and hard carbon produced by a vacuum arc deposition technique. For comparison, diamond nucleation on silicon substrates coated with submicrometer-sized diamond particles and uncoated smooth silicon surfaces was also examined under similar conditions. Except for evaporated carbon films, significantly higher diamond nucleation densities were obtained by subjecting the carbon-coated substrates to a low-temperature high-methane concentration hydrogen plasma treatment prior to diamond nucleation. The highest nucleation density ([similar to]3[times]10[sup 8] cm[sup [minus]2]) was obtained with hard carbon films. Scanning electron microscopy and Raman spectroscopy demonstrated that the diamond nucleation density increased with the film thickness and etching resistance. The higher diamond nucleation density obtained with the vacuum arc-deposited carbon films may be attributed to the inherent high etching resistance, presumably resulting from the high content of [ital sp][sup 3] atomic bonds. Microscopy observations suggested that diamond nucleation in the presence of non-diamond carbon deposits resulted from carbon layers generated under the pretreatment conditions.

  13. A solid-state nuclear magnetic resonance study of post-plasma reactions in organosilicone microwave plasma-enhanced chemical vapor deposition (PECVD) coatings.

    PubMed

    Hall, Colin J; Ponnusamy, Thirunavukkarasu; Murphy, Peter J; Lindberg, Mats; Antzutkin, Oleg N; Griesser, Hans J

    2014-06-11

    Plasma-polymerized organosilicone coatings can be used to impart abrasion resistance and barrier properties to plastic substrates such as polycarbonate. Coating rates suitable for industrial-scale deposition, up to 100 nm/s, can be achieved through the use of microwave plasma-enhanced chemical vapor deposition (PECVD), with optimal process vapors such as tetramethyldisiloxane (TMDSO) and oxygen. However, it has been found that under certain deposition conditions, such coatings are subject to post-plasma changes; crazing or cracking can occur anytime from days to months after deposition. To understand the cause of the crazing and its dependence on processing plasma parameters, the effects of post-plasma reactions on the chemical bonding structure of coatings deposited with varying TMDSO-to-O2 ratios was studied with (29)Si and (13)C solid-state magic angle spinning nuclear magnetic resonance (MAS NMR) using both single-pulse and cross-polarization techniques. The coatings showed complex chemical compositions significantly altered from the parent monomer. (29)Si MAS NMR spectra revealed four main groups of resonance lines, which correspond to four siloxane moieties (i.e., mono (M), di (D), tri (T), and quaternary (Q)) and how they are bound to oxygen. Quantitative measurements showed that the ratio of TMDSO to oxygen could shift the chemical structure of the coating from 39% to 55% in Q-type bonds and from 28% to 16% for D-type bonds. Post-plasma reactions were found to produce changes in relative intensities of (29)Si resonance lines. The NMR data were complemented by Fourier transform infrared (FTIR) spectroscopy. Together, these techniques have shown that the bonding environment of Si is drastically altered by varying the TMDSO-to-O2 ratio during PECVD, and that post-plasma reactions increase the cross-link density of the silicon-oxygen network. It appears that Si-H and Si-OH chemical groups are the most susceptible to post-plasma reactions. Coatings produced at a

  14. Carbon Nanotubes/Nanofibers by Plasma Enhanced Chemical Vapour Deposition

    NASA Technical Reports Server (NTRS)

    Teo, K. B. K.; Hash, D. B.; Bell, M. S.; Chhowalla, M.; Cruden, B. A.; Amaratunga, G. A. J.; Meyyappan, M.; Milne, W. I.

    2005-01-01

    Plasma enhanced chemical vapour deposition (PECVD) has been recently used for the production of vertically aligned carbon nanotubedfibers (CN) directly on substrates. These structures are potentially important technologically as electron field emitters (e.g. microguns, microwave amplifiers, displays), nanoelectrodes for sensors, filter media, superhydrophobic surfaces and thermal interface materials for microelectronics. A parametric study on the growth of CN grown by glow discharge dc-PECVD is presented. In this technique, a substrate containing thin film Ni catalyst is exposed to C2H2 and NH3 gases at 700 C. Without plasma, this process is essentially thermal CVD which produces curly spaghetti-like CN as seen in Fig. 1 (a). With the plasma generated by biasing the substrate at -6OOV, we observed that the CN align vertically during growth as shown in Fig. l(b), and that the magnitude of the applied substrate bias affects the degree of alignment. The thickness of the thin film Ni catalyst was found to determine the average diameter and inversely the length of the CN. The yield and density of the CN were controlled by the use of different diffusion barrier materials under the Ni catalyst. Patterned CN growth [Fig. l(c)], with la variation in CN diameter of 4.1% and 6.3% respectively, is achieved by lithographically defining the Ni thin film prior to growth. The shape of the structures could be varied from very straight nanotube-like to conical tip-like nanofibers by increasing the ratio of C2H2 in the gas flow. Due to the plasma decomposition of C2H2, amorphous carbon (a-C) is an undesirable byproduct which could coat the substrate during CN growth. Using a combination of depth profiled Auger electron spectroscopy to study the substrate and in-situ mass spectroscopy to examine gas phase neutrals and ions, the optimal conditions for a-C free growth of CN is determined.

  15. Plasma-enhanced chemical vapor deposition of multiwalled carbon nanofibers

    NASA Technical Reports Server (NTRS)

    Matthews, Kristopher; Cruden, Brett A.; Chen, Bin; Meyyappan, M.; Delzeit, Lance

    2002-01-01

    Plasma-enhanced chemical vapor deposition is used to grow vertically aligned multiwalled carbon nanofibers (MWNFs). The graphite basal planes in these nanofibers are not parallel as in nanotubes; instead they exhibit a small angle resembling a stacked cone arrangement. A parametric study with varying process parameters such as growth temperature, feedstock composition, and substrate power has been conducted, and these parameters are found to influence the growth rate, diameter, and morphology. The well-aligned MWNFs are suitable for fabricating electrode systems in sensor and device development.

  16. Quantum cascade laser investigations of CH{sub 4} and C{sub 2}H{sub 2} interconversion in hydrocarbon/H{sub 2} gas mixtures during microwave plasma enhanced chemical vapor deposition of diamond

    SciTech Connect

    Ma Jie; Cheesman, Andrew; Ashfold, Michael N. R.; Hay, Kenneth G.; Wright, Stephen; Langford, Nigel; Duxbury, Geoffrey; Mankelevich, Yuri A.

    2009-08-01

    CH{sub 4} and C{sub 2}H{sub 2} molecules (and their interconversion) in hydrocarbon/rare gas/H{sub 2} gas mixtures in a microwave reactor used for plasma enhanced diamond chemical vapor deposition (CVD) have been investigated by line-of-sight infrared absorption spectroscopy in the wavenumber range of 1276.5-1273.1 cm{sup -1} using a quantum cascade laser spectrometer. Parameters explored include process conditions [pressure, input power, source hydrocarbon, rare gas (Ar or Ne), input gas mixing ratio], height (z) above the substrate, and time (t) after addition of hydrocarbon to a pre-existing Ar/H{sub 2} plasma. The line integrated absorptions so obtained have been converted to species number densities by reference to the companion two-dimensional (r,z) modeling of the CVD reactor described in Mankelevich et al. [J. Appl. Phys. 104, 113304 (2008)]. The gas temperature distribution within the reactor ensures that the measured absorptions are dominated by CH{sub 4} and C{sub 2}H{sub 2} molecules in the cool periphery of the reactor. Nonetheless, the measurements prove to be of enormous value in testing, tensioning, and confirming the model predictions. Under standard process conditions, the study confirms that all hydrocarbon source gases investigated (methane, acetylene, ethane, propyne, propane, and butane) are converted into a mixture dominated by CH{sub 4} and C{sub 2}H{sub 2}. The interconversion between these two species is highly dependent on the local gas temperature and the H atom number density, and thus on position within the reactor. CH{sub 4}->C{sub 2}H{sub 2} conversion occurs most efficiently in an annular shell around the central plasma (characterized by 1400CH{sub 4} is favored in the more distant regions where T{sub gas}<1400 K. Analysis of the multistep interconversion mechanism reveals substantial net consumption of H atoms accompanying the CH{sub 4}->C{sub 2}H{sub 2

  17. Quantum cascade laser investigations of CH4 and C2H2 interconversion in hydrocarbon/H2 gas mixtures during microwave plasma enhanced chemical vapor deposition of diamond

    NASA Astrophysics Data System (ADS)

    Ma, Jie; Cheesman, Andrew; Ashfold, Michael N. R.; Hay, Kenneth G.; Wright, Stephen; Langford, Nigel; Duxbury, Geoffrey; Mankelevich, Yuri A.

    2009-08-01

    CH4 and C2H2 molecules (and their interconversion) in hydrocarbon/rare gas/H2 gas mixtures in a microwave reactor used for plasma enhanced diamond chemical vapor deposition (CVD) have been investigated by line-of-sight infrared absorption spectroscopy in the wavenumber range of 1276.5-1273.1 cm-1 using a quantum cascade laser spectrometer. Parameters explored include process conditions [pressure, input power, source hydrocarbon, rare gas (Ar or Ne), input gas mixing ratio], height (z) above the substrate, and time (t) after addition of hydrocarbon to a pre-existing Ar/H2 plasma. The line integrated absorptions so obtained have been converted to species number densities by reference to the companion two-dimensional (r ,z) modeling of the CVD reactor described in Mankelevich et al. [J. Appl. Phys. 104, 113304 (2008)]. The gas temperature distribution within the reactor ensures that the measured absorptions are dominated by CH4 and C2H2 molecules in the cool periphery of the reactor. Nonetheless, the measurements prove to be of enormous value in testing, tensioning, and confirming the model predictions. Under standard process conditions, the study confirms that all hydrocarbon source gases investigated (methane, acetylene, ethane, propyne, propane, and butane) are converted into a mixture dominated by CH4 and C2H2. The interconversion between these two species is highly dependent on the local gas temperature and the H atom number density, and thus on position within the reactor. CH4→C2H2 conversion occurs most efficiently in an annular shell around the central plasma (characterized by 1400

  18. Transformation of polymer composite nanofibers to diamond fibers and films by microwave plasma-enhanced CVD process

    NASA Astrophysics Data System (ADS)

    Potocký, Š.; Ižák, T.; Rezek, B.; Tesárek, P.; Kromka, A.

    2014-09-01

    In this work, polyvinyl alcohol (PVA) fibers were used as a polymer matrix containing ultra-dispersed diamond (UDD) nanoparticles. Growth of diamond fiber-like structures and films by microwave plasma-enhanced chemical vapor deposition was studied as a function of UDD concentration in the PVA matrix. The influence of surface tension (fibers radii) for nucleation/seeding is discussed. Using a high UDD concentration in the polymer matrix lead to the formation of fiber-like structures. The composite PVA polymer nanofibers with the highest concentration of UDD nanoparticles resulted in the growth of nearly continuous diamond film at low thickness of 250 nm.

  19. Tungsten Deposition on Graphite using Plasma Enhanced Chemical Vapour Deposition.

    NASA Astrophysics Data System (ADS)

    Sharma, Uttam; Chauhan, Sachin S.; Sharma, Jayshree; Sanyasi, A. K.; Ghosh, J.; Choudhary, K. K.; Ghosh, S. K.

    2016-10-01

    The tokamak concept is the frontrunner for achieving controlled thermonuclear reaction on earth, an environment friendly way to solve future energy crisis. Although much progress has been made in controlling the heated fusion plasmas (temperature ∼ 150 million degrees) in tokamaks, technological issues related to plasma wall interaction topic still need focused attention. In future, reactor grade tokamak operational scenarios, the reactor wall and target plates are expected to experience a heat load of 10 MW/m2 and even more during the unfortunate events of ELM's and disruptions. Tungsten remains a suitable choice for the wall and target plates. It can withstand high temperatures, its ductile to brittle temperature is fairly low and it has low sputtering yield and low fuel retention capabilities. However, it is difficult to machine tungsten and hence usages of tungsten coated surfaces are mostly desirable. To produce tungsten coated graphite tiles for the above-mentioned purpose, a coating reactor has been designed, developed and made operational at the SVITS, Indore. Tungsten coating on graphite has been attempted and successfully carried out by using radio frequency induced plasma enhanced chemical vapour deposition (rf -PECVD) for the first time in India. Tungsten hexa-fluoride has been used as a pre-cursor gas. Energy Dispersive X-ray spectroscopy (EDS) clearly showed the presence of tungsten coating on the graphite samples. This paper presents the details of successful operation and achievement of tungsten coating in the reactor at SVITS.

  20. Plasma-enhanced chemical vapor deposition of tungsten films

    NASA Astrophysics Data System (ADS)

    Chu, J. K.; Tang, C. C.; Hess, D. W.

    1982-07-01

    High-purity films of tungsten are deposited from tungsten hexafluoride and hydrogen using plasma-enhanced deposition (PED). At 400 °C deposition temperature, resistivities of ˜40 μΩ cm are attained. After annealing at 1100 °C, the resistivity falls to ˜7 μΩ cm. Below 400 °C, the as-deposited film stress is <6×109 dynes/cm2. Tensile, unlike tungsten, molybdenum films deposited by PED displayed high resistivities.

  1. Diagnostic for Plasma Enhanced Chemical Vapor Deposition and Etch Systems

    NASA Technical Reports Server (NTRS)

    Cappelli, Mark A.

    1999-01-01

    In order to meet NASA's requirements for the rapid development and validation of future generation electronic devices as well as associated materials and processes, enabling technologies ion the processing of semiconductor materials arising from understanding etch chemistries are being developed through a research collaboration between Stanford University and NASA-Ames Research Center, Although a great deal of laboratory-scale research has been performed on many of materials processing plasmas, little is known about the gas-phase and surface chemical reactions that are critical in many etch and deposition processes, and how these reactions are influenced by the variation in operating conditions. In addition, many plasma-based processes suffer from stability and reliability problems leading to a compromise in performance and a potentially increased cost for the semiconductor manufacturing industry. Such a lack of understanding has hindered the development of process models that can aid in the scaling and improvement of plasma etch and deposition systems. The research described involves the study of plasmas used in semiconductor processes. An inductively coupled plasma (ICP) source in place of the standard upper electrode assembly of the Gaseous Electronics Conference (GEC) radio-frequency (RF) Reference Cell is used to investigate the discharge characteristics and chemistries. This ICP source generates plasmas with higher electron densities (approximately 10(exp 12)/cu cm) and lower operating pressures (approximately 7 mTorr) than obtainable with the original parallel-plate version of the GEC Cell. This expanded operating regime is more relevant to new generations of industrial plasma systems being used by the microelectronics industry. The motivation for this study is to develop an understanding of the physical phenomena involved in plasma processing and to measure much needed fundamental parameters, such as gas-phase and surface reaction rates. species

  2. Plasma enhanced metalorganic chemical vapor deposition of amorphous aluminum nitride

    NASA Astrophysics Data System (ADS)

    Harris, H.; Biswas, N.; Temkin, H.; Gangopadhyay, S.; Strathman, M.

    2001-12-01

    Plasma enhanced deposition of amorphous aluminum nitride (AlN) using trimethylaluminum, hydrogen, and nitrogen was performed in a capacitively coupled plasma system. Temperature was varied from 350 to 550 °C, and pressure dependence of the film structure was investigated. Films were characterized by Fourier transform infrared, Rutherford backscattering (RBS), ellipsometry, and x-ray diffraction (XRD). The films are amorphous in nature, as indicated by XRD. Variations in the refractive index were observed in ellipsometric measurements, which is explained by the incorporation of carbon in the films, and confirmed by RBS. Capacitance-voltage, conductance-voltage (G-V), and current-voltage measurements were performed to reveal bulk and interface electrical properties. The electrical properties showed marked dependence on processing conditions of the AlN films. Clear peaks as observed in the G-V characteristics indicated that the losses are predominantly due to interface states. The interface state density ranged between 1010 and 1011eV-1 cm-2. Annealing in hydrogen resulted in lowering of interface state density values.

  3. Microwave remote plasma enhanced-atomic layer deposition system with multicusp confinement chamber.

    PubMed

    Dechana, A; Thamboon, P; Boonyawan, D

    2014-10-01

    A microwave remote Plasma Enhanced-Atomic Layer Deposition system with multicusp confinement chamber is established at the Plasma and Beam Physics research facilities, Chiang Mai, Thailand. The system produces highly-reactive plasma species in order to enhance the deposition process of thin films. The addition of the multicusp magnetic fields further improves the plasma density and uniformity in the reaction chamber. Thus, the system is more favorable to temperature-sensitive substrates when heating becomes unwanted. Furthermore, the remote-plasma feature, which is generated via microwave power source, offers tunability of the plasma properties separately from the process. As a result, the system provides high flexibility in choice of materials and design experiments, particularly for low-temperature applications. Performance evaluations of the system were carried on coating experiments of Al2O3 layers onto a silicon wafer. The plasma characteristics in the chamber will be described. The resulted Al2O3 films-analyzed by Rutherford Backscattering Spectrometry in channeling mode and by X-ray Photoelectron Spectroscopy techniques-will be discussed.

  4. Microwave remote plasma enhanced-atomic layer deposition system with multicusp confinement chamber

    SciTech Connect

    Dechana, A.; Thamboon, P.; Boonyawan, D.

    2014-10-15

    A microwave remote Plasma Enhanced-Atomic Layer Deposition system with multicusp confinement chamber is established at the Plasma and Beam Physics research facilities, Chiang Mai, Thailand. The system produces highly-reactive plasma species in order to enhance the deposition process of thin films. The addition of the multicusp magnetic fields further improves the plasma density and uniformity in the reaction chamber. Thus, the system is more favorable to temperature-sensitive substrates when heating becomes unwanted. Furthermore, the remote-plasma feature, which is generated via microwave power source, offers tunability of the plasma properties separately from the process. As a result, the system provides high flexibility in choice of materials and design experiments, particularly for low-temperature applications. Performance evaluations of the system were carried on coating experiments of Al{sub 2}O{sub 3} layers onto a silicon wafer. The plasma characteristics in the chamber will be described. The resulted Al{sub 2}O{sub 3} films—analyzed by Rutherford Backscattering Spectrometry in channeling mode and by X-ray Photoelectron Spectroscopy techniques—will be discussed.

  5. Microwave remote plasma enhanced-atomic layer deposition system with multicusp confinement chamber

    NASA Astrophysics Data System (ADS)

    Dechana, A.; Thamboon, P.; Boonyawan, D.

    2014-10-01

    A microwave remote Plasma Enhanced-Atomic Layer Deposition system with multicusp confinement chamber is established at the Plasma and Beam Physics research facilities, Chiang Mai, Thailand. The system produces highly-reactive plasma species in order to enhance the deposition process of thin films. The addition of the multicusp magnetic fields further improves the plasma density and uniformity in the reaction chamber. Thus, the system is more favorable to temperature-sensitive substrates when heating becomes unwanted. Furthermore, the remote-plasma feature, which is generated via microwave power source, offers tunability of the plasma properties separately from the process. As a result, the system provides high flexibility in choice of materials and design experiments, particularly for low-temperature applications. Performance evaluations of the system were carried on coating experiments of Al2O3 layers onto a silicon wafer. The plasma characteristics in the chamber will be described. The resulted Al2O3 films—analyzed by Rutherford Backscattering Spectrometry in channeling mode and by X-ray Photoelectron Spectroscopy techniques—will be discussed.

  6. The Role of Plasma in Plasma Enhanced Chemical Vapour Deposition of Nanostructure Growth

    NASA Technical Reports Server (NTRS)

    Hash, David B.; Meyyappan, M.; Teo, Kenneth B. K.; Lacerda, Rodrigo G.; Rupesinghe, Nalin L.

    2004-01-01

    Chemical vapour deposition (CVD) has become the preferred process for high yield growth of carbon nanotubes and nanofibres because of its ability to pattern growth through lithographic positioning of transition metal catalysts on substrates. Many potential applications of nanotubes such as field emitters [1] require not only patterned growth but also vertical alignment. Some degree of ali,ment in thermal CVD processes can be obtained when carbon nanotubes are grown closely together as a result of van der Waals interactions. The ali,onment however is marginal, and the van der Waals prerequisite makes growth of freestanding nanofibres with thermal CVD unrealizable. The application of electric fields as a means of ali,onment has been shown to overcome this limitation [2-5], and highly aligned nanostructures can be grown if electric fields on the order of 0.5 V/microns are employed. Plasma enhanced CVD in various configurations including dc, rf, microwave, inductive and electron cyclotron resonance has been pursued as a means of enabling alignment in the CVD process. However, the sheath fields for the non-dc sources are in general not sufficient for a high degree of ali,pment and an additional dc bias is usually applied to the growth substrate. This begs the question as to the actual role of the plasma. It is clear that the plasma itself is not required for aligned growth as references [3] and [4] employed fields through small applied voltages (3-20 V) across very small electrode spacings (10-100 microns) and thus avoided striking a discharge.

  7. Selective growth of boron nitride nanotubes by plasma-enhanced chemical vapor deposition at low substrate temperature

    NASA Astrophysics Data System (ADS)

    Guo, L.; Singh, R. N.

    2008-02-01

    Hexagonal boron nitride nanotubes (BNNTs) were synthesized at a low substrate temperature of 800 °C on nickel (Ni) coated oxidized Si(111) wafers in a microwave plasma-enhanced chemical vapor deposition system (MPCVD) by decomposition and reaction of gas mixtures consisting of B2H6-NH3-H2. The 1D BN nanostructures grew preferentially on Ni catalyst islands with a small thickness only. In situ mass spectroscopic analysis and optical emission spectroscopy were used to identify the gas reactions responsible for the BNNT formation. The morphology and structural properties of the deposits were analyzed by SEM, TEM, EDX, SAD and Raman spectroscopy. The growth mechanism of the BNNTs was identified.

  8. Plasma-enhanced chemical vapor deposition of low-resistive tungsten thin films

    SciTech Connect

    Kim, Y.T.; Min, S.; Hong, J.S. ); Kim, C.K. )

    1991-02-25

    Controlling the wafer temperatures from 200 to 500 {degree}C at H{sub 2}/WF{sub 6} flow ratio equal to 24, low-resistive (about 11 {mu}{Omega} cm) tungsten thin films are deposited by plasma-enhanced chemical vapor deposition. The as-deposited tungsten films have (110), (200), and (211) oriented bcc structures and Auger depth profile shows that fluorine and oxygen impurities are below the detection limit of Auger electron spectroscopy.

  9. The Relationship Between Chemical Structure and Dielectric Properties of Plasma-Enhanced Chemical Vapor Deposited Polymer Thin Films (Postprint)

    DTIC Science & Technology

    2007-01-01

    Materials Sci & Tech Applications, LLC) N. Venkatasubramanian and John T. Grant (University of Dayton) Kurt Eyink, Jesse Enlow, and Timothy J. Bunning...structure and dielectric properties of plasma-enhanced chemical vapor deposited polymer thin films Hao Jiang b,⁎, Lianggou Hong b, N. Venkatasubramanian c

  10. Properties of Plasma Enhanced Chemical Vapor Deposition Barrier Coatings and Encapsulated Polymer Solar Cells

    NASA Astrophysics Data System (ADS)

    Qi, Lei; Zhang, Chunmei; Chen, Qiang

    2014-01-01

    In this paper, we report silicon oxide coatings deposited by plasma enhanced chemical vapor deposition technology (PECVD) on 125 μm polyethyleneterephthalate (PET) surfaces for the purpose of the shelf lifetime extension of sealed polymer solar cells. After optimization of the processing parameters, we achieved a water vapor transmission rate (WVTR) of ca. 10-3 g/m2/day with the oxygen transmission rate (OTR) less than 0.05 cc/m2/day, and succeeded in extending the shelf lifetime to about 400 h in encapsulated solar cells. And then the chemical structure of coatings related to the properties of encapsulated cell was investigated in detail.

  11. Textured (100) yttria-stabilized zirconia thin films deposited by plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Holzschuh, H.; Suhr, H.

    1991-07-01

    Thin films of yttria-stabilized zirconia were deposited by plasma-enhanced chemical vapor deposition on quartz Si(100), Si(111), Ni, and the steels V2A and Hastelloy at substrate temperatures (Ts): 673-873 K. The metal beta-diketonates Y (thd)3 and Zr(thd)4 were used as precursors. The fully stabilized fluorite-type cubic structure was obtained over a wide range of yttria contents from 3.5 to 80 mol pct (Ts = 773 K). The quality of the films depended on the match of the thermal expansion coefficients of substrate and deposit.

  12. Electrical transport properties of microcrystalline silicon grown by plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Pinto, Nicola; Ficcadenti, Marco; Morresi, Lorenzo; Murri, Roberto; Ambrosone, Giuseppina; Coscia, Ubaldo

    2004-12-01

    The dark conductivity and Hall mobility of hydrogenated silicon films deposited varying the silane concentration f =SiH4/(SiH4+H2) in a conventional plasma enhanced chemical vapor deposition system have been investigated as a function of temperature, taking into account their structural properties. The electrical properties have been studied in terms of a structural two-phase model. A clear transition from the electrical transport governed by a crystalline phase, in the range 1%⩽f⩽3%, to that controlled by an amorphous phase, for f >3%, has been evidenced. Some metastable effects of the dark conductivity have been noticed.

  13. Microstructural modification of nc-Si/SiOx films during plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Zhang, X. W.

    2005-07-01

    Nanocrystalline-silicon embedded silicon oxide films are prepared by plasma-enhanced chemical vapor deposition (PECVD) at 300 °C without post-heat treatment. Measurements of XPS, IR, XRD, and HREM are performed. Microstructural modifications are found occurring throughout the film deposition. The silica network with a high oxide state is suggested to be formed directly under the abduction of the former deposited layer, rather than processing repeatedly from the original low-oxide state of silica. Nanocrystalline silicon particles with a size of 6-10 nm are embedded in the SiOx film matrix, indicating the potential application in Si-based optoelectronic integrity.

  14. Plasma-enhanced chemical vapor deposition of β-tungsten, a metastable phase

    NASA Astrophysics Data System (ADS)

    Tang, C. C.; Hess, D. W.

    1984-09-01

    Plasma-enhanced chemical vapor deposition of a metastable phase of tungsten ( β-W) is performed using tungsten hexafluoride and hydrogen as source gases. At 350 °C, the as-deposited resistivity of these films is ˜50 μΩ cm. After heat treatments between 650 and 750 °C in forming gas, the resistivity drops below 11 μΩ cm. Concomitant with this resistivity change is a phase change to α-W, the equilibrium, body-centered-cubic form.

  15. Amorphous hollow carbon spheres synthesized using radio frequency plasma-enhanced chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Yang, G. M.; Xu, Q.; Tian, H. W.; Wang, X.; Zheng, W. T.

    2008-10-01

    We report a method to synthesize amorphous hollow carbon spheres, with diameters ranging from 100 to 800 nm, which are dispersed among bent graphitized carbon nanotubes using radio frequency plasma-enhanced chemical vapour deposition in mixed CH4/H2 gases. The products are characterized by techniques including scanning electron microscopy, energy-dispersive x-ray spectroscopy, Raman spectroscopy and transmission electron microscopy. It is found that MgO and Ni nanoparticles together with hydrogen play important roles in the formation of the spheres. A possible formation mechanism for the carbon composites has been proposed.

  16. Growth of Er-doped silicon using metalorganics by plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Andry, P. S.; Varhue, W. J.; Ladipo, F.; Ahmed, K.; Adams, E.; Lavoie, M.; Klein, P. B.; Hengehold, R.; Hunter, J.

    1996-07-01

    Epitaxial growth of Er-doped silicon films has been performed by plasma-enhanced chemical vapor deposition at low temperature (430 °C) using an electron cyclotron resonance source. The goal was to incorporate an optically active center, erbium surrounded by nitrogen, through the use of the metalorganic compound tris (bis trimethyl silyl amido) erbium. Films were analyzed by Rutherford backscattering spectrometry, secondary ion mass spectroscopy, and high resolution x-ray diffraction. The characteristic 1.54 μm emission was observed by photoluminescence spectroscopy. Previous attempts to incorporate the complex (ErO6) using tris (2,2,6,6-tetramethyl- 3,5-heptanedionato) erbium (III) indicated that excessive carbon contamination lowered epitaxial quality and reduced photoluminescent intensity. In this study, chemical analysis of the films also revealed a large carbon concentration, however, the effect on epitaxial quality was much less destructive. A factorial design experiment was performed whose analysis identified the key processing parameters leading to high quality luminescent films. Hydrogen was found to be a major cause of crystal quality degradation in our metalorganic plasma-enhanced process.

  17. MICROWAVE TECHNOLOGY CHEMICAL SYNTHESIS APPLICATIONS

    EPA Science Inventory

    Microwave-accelerated chemical syntheses in various solvents as well as under solvent-free conditions have witnessed an explosive growth. The technique has found widespread application predominantly exploiting the inexpensive unmodified household microwave (MW) ovens although th...

  18. MICROWAVE TECHNOLOGY CHEMICAL SYNTHESIS APPLICATIONS

    EPA Science Inventory

    Microwave-accelerated chemical syntheses in various solvents as well as under solvent-free conditions have witnessed an explosive growth. The technique has found widespread application predominantly exploiting the inexpensive unmodified household microwave (MW) ovens although th...

  19. A mathematical model and simulation results of plasma enhanced chemical vapor deposition of silicon nitride films

    NASA Astrophysics Data System (ADS)

    Konakov, S. A.; Krzhizhanovskaya, V. V.

    2015-01-01

    We developed a mathematical model of Plasma Enhanced Chemical Vapor Deposition (PECVD) of silicon nitride thin films from SiH4-NH3-N2-Ar mixture, an important application in modern materials science. Our multiphysics model describes gas dynamics, chemical physics, plasma physics and electrodynamics. The PECVD technology is inherently multiscale, from macroscale processes in the chemical reactor to atomic-scale surface chemistry. Our macroscale model is based on Navier-Stokes equations for a transient laminar flow of a compressible chemically reacting gas mixture, together with the mass transfer and energy balance equations, Poisson equation for electric potential, electrons and ions balance equations. The chemical kinetics model includes 24 species and 58 reactions: 37 in the gas phase and 21 on the surface. A deposition model consists of three stages: adsorption to the surface, diffusion along the surface and embedding of products into the substrate. A new model has been validated on experimental results obtained with the "Plasmalab System 100" reactor. We present the mathematical model and simulation results investigating the influence of flow rate and source gas proportion on silicon nitride film growth rate and chemical composition.

  20. Stress hysteresis and mechanical properties of plasma-enhanced chemical vapor deposited dielectric films

    NASA Astrophysics Data System (ADS)

    Thurn, Jeremy; Cook, Robert F.; Kamarajugadda, Mallika; Bozeman, Steven P.; Stearns, Laura C.

    2004-02-01

    A comprehensive survey is described of the responses of three plasma-enhanced chemical vapor deposited dielectric film systems to thermal cycling and indentation contact. All three films—silicon oxide, silicon nitride, and silicon oxy-nitride—exhibited significant nonequilibrium permanent changes in film stress on thermal cycling or annealing. The linear relationship between stress and temperature changed after the films were annealed at 300 °C, representing a structural alteration in the film reflecting a change in coefficient of thermal expansion or biaxial modulus. A double-substrate method was used to deduce both thermoelastic properties before and after the anneal of selected films and the results were compared with the modulus deconvoluted from small-scale depth-sensing indentation experiments (nanoindentation). Rutherford backscattering spectrometry and hydrogen forward scattering were used to deduce the composition of the films and it was found that all the films contained significant amounts of hydrogen.

  1. Plasma-enhanced chemical vapor deposition of amorphous Si on graphene

    NASA Astrophysics Data System (ADS)

    Lupina, G.; Strobel, C.; Dabrowski, J.; Lippert, G.; Kitzmann, J.; Krause, H. M.; Wenger, Ch.; Lukosius, M.; Wolff, A.; Albert, M.; Bartha, J. W.

    2016-05-01

    Plasma-enhanced chemical vapor deposition of thin a-Si:H layers on transferred large area graphene is investigated. Radio frequency (RF, 13.56 MHz) and very high frequency (VHF, 140 MHz) plasma processes are compared. Both methods provide conformal coating of graphene with Si layers as thin as 20 nm without any additional seed layer. The RF plasma process results in amorphization of the graphene layer. In contrast, the VHF process keeps the high crystalline quality of the graphene layer almost intact. Correlation analysis of Raman 2D and G band positions indicates that Si deposition induces reduction of the initial doping in graphene and an increase of compressive strain. Upon rapid thermal annealing, the amorphous Si layer undergoes dehydrogenation and transformation into a polycrystalline film, whereby a high crystalline quality of graphene is preserved.

  2. Plasma-enhanced chemical vapor deposition method to coat micropipettes with diamond-like carbon

    SciTech Connect

    Kakuta, Naoto; Watanabe, Mayu; Yamada, Yukio; Okuyama, Naoki; Mabuchi, Kunihiko

    2005-07-15

    This article provides a simple method for coating glass micropipettes with diamond-like carbon (DLC) through plasma-enhanced chemical vapor deposition. The apparatus uses a cathode that is a thin-metal-coated micropipette itself and an anode that is a meshed cylinder with its cylinder axis along the micropipette length. To produce a uniform plasma and prevent a temperature increase at the tip due to ion collision concentration, we investigated the effect of the height and diameter of the meshed cylindrical anode on the plasma. Intermittent deposition is also effective for inhibiting the temperature rise and producing high quality DLC films. Measured Raman spectra and electric resistivity indicate that a DLC film suitable for use as an insulating film can be produced on the micropipette. This coating method should also be useful for other extremely small probes.

  3. High Current Emission from Patterned Aligned Carbon Nanotubes Fabricated by Plasma-Enhanced Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Cui, Linfan; Chen, Jiangtao; Yang, Bingjun; Jiao, Tifeng

    2015-12-01

    Vertically, carbon nanotube (CNT) arrays were successfully fabricated on hexagon patterned Si substrates through radio frequency plasma-enhanced chemical vapor deposition using gas mixtures of acetylene (C2H2) and hydrogen (H2) with Fe/Al2O3 catalysts. The CNTs were found to be graphitized with multi-walled structures. Different H2/C2H2 gas flow rate ratio was used to investigate the effect on CNT growth, and the field emission properties were optimized. The CNT emitters exhibited excellent field emission performance (the turn-on and threshold fields were 2.1 and 2.4 V/μm, respectively). The largest emission current could reach 70 mA/cm2. The emission current was stable, and no obvious deterioration was observed during the long-term stability test of 50 h. The results were relevant for practical applications based on CNTs.

  4. High Current Emission from Patterned Aligned Carbon Nanotubes Fabricated by Plasma-Enhanced Chemical Vapor Deposition.

    PubMed

    Cui, Linfan; Chen, Jiangtao; Yang, Bingjun; Jiao, Tifeng

    2015-12-01

    Vertically, carbon nanotube (CNT) arrays were successfully fabricated on hexagon patterned Si substrates through radio frequency plasma-enhanced chemical vapor deposition using gas mixtures of acetylene (C2H2) and hydrogen (H2) with Fe/Al2O3 catalysts. The CNTs were found to be graphitized with multi-walled structures. Different H2/C2H2 gas flow rate ratio was used to investigate the effect on CNT growth, and the field emission properties were optimized. The CNT emitters exhibited excellent field emission performance (the turn-on and threshold fields were 2.1 and 2.4 V/μm, respectively). The largest emission current could reach 70 mA/cm(2). The emission current was stable, and no obvious deterioration was observed during the long-term stability test of 50 h. The results were relevant for practical applications based on CNTs.

  5. Deposition of electrochromic tungsten oxide thin films by plasma-enhanced chemical vapor deposition

    SciTech Connect

    Henley, W.B.; Sacks, G.J.

    1997-03-01

    Use of plasma-enhanced chemical vapor deposition (PECVD) for electrochromic WO{sub 3} film deposition is investigated. Oxygen, hydrogen, and tungsten hexafluoride were used as source gases. Reactant gas flow was investigated to determine the effect on film characteristics. High quality optical films were obtained at deposition rates on the order of 100 {angstrom}/s. Higher deposition rates were attainable but film quality and optical coherence degraded. Atomic emission spectroscopy (AES), was used to provide an in situ assessment of the plasma deposition chemistry. Through AES, it is shown that the hydrogen gas flow is essential to the deposition of the WO{sub 3} film. Oxygen gas flow and tungsten hexafluoride gas flow must be approximately equal for high quality films.

  6. Low temperature plasma enhanced chemical vapor deposition of thin films combining mechanical stiffness, electrical insulation, and homogeneity in microcavities

    SciTech Connect

    Peter, S.; Guenther, M.; Hauschild, D.; Richter, F.

    2010-08-15

    The deposition of hydrogenated amorphous carbon (a-C:H) as well as hydrogenated amorphous silicon carbonitride (SiCN:H) films was investigated in view of a simultaneous realization of a minimum Young's modulus (>70 GPa), a high electrical insulation ({>=}1 MV/cm), a low permittivity and the uniform coverage of microcavities with submillimeter dimensions. For the a-C:H deposition the precursors methane (CH{sub 4}) and acetylene (C{sub 2}H{sub 2}) were used, while SiCN:H films were deposited from mixtures of trimethylsilane [SiH(CH{sub 3}){sub 3}] with nitrogen and argon. To realize the deposition of micrometer thick films with the aforementioned complex requirements at substrate temperatures {<=}200 deg. C, several plasma enhanced chemical vapor deposition methods were investigated: the capacitively coupled rf discharge and the microwave electron cyclotron resonance (ECR) plasma, combined with two types of pulsed substrate bias. SiCN:H films deposited at about 1 Pa from ECR plasmas with pulsed high-voltage bias best met the requirements. Pulsed biasing with pulse periods of about 1 {mu}s and amplitudes of about -2 kV was found to be most advantageous for the conformal low temperature coating of the microtrenches, thereby ensuring the required mechanical and insulating film properties.

  7. Surface modification of silicon-containing fluorocarbon films prepared by plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Jin, Yoonyoung; Desta, Yohannes; Goettert, Jost; Lee, G. S.; Ajmera, P. K.

    2005-07-01

    Surface modification of silicon-containing fluorocarbon (SiCF) films achieved by wet chemical treatments and through x-ray irradiation is examined. The SiCF films were prepared by plasma-enhanced chemical vapor deposition, using gas precursors of tetrafluoromethane and disilane. As-deposited SiCF film composition was analyzed by x-ray photoelectron spectroscopy. Surface modification of SiCF films utilizing n-lithiodiaminoethane wet chemical treatment is discussed. Sessile water-drop contact angle changed from 95°+/-2° before treatment to 32°+/-2° after treatment, indicating a change in the film surface characteristics from hydrophobic to hydrophilic. For x-ray irradiation on the SiCF film with a dose of 27.4 kJ/cm3, the contact angle of the sessile water drop changed from 95°+/-2° before radiation to 39°+/-3° after x-ray exposure. The effect of x-ray exposure on chemical bond structure of SiCF films is studied using Fourier transform infrared measurements. Electroless Cu deposition was performed to test the applicability of the surface modified films. The x-ray irradiation method offers a unique advantage in making possible surface modification in a localized area of high-aspect-ratio microstructures. Fabrication of a Ti-membrane x-ray mask is introduced here for selective surface modification using x-ray irradiation.

  8. Development of a Ge/GaAs HMT (High Mobility Transistor) Technology Based on Plasma Enhanced Chemical Vapor Deposition

    DTIC Science & Technology

    1989-11-01

    R SEARCH TRIANGLE INSTITUTE RTI/3628/89-3QTR November 1089 0 00 DEVELOPMENT OF A Ge/GaAs [MT TECHNOLCGY JBASED ON PLASMA-ENHANCED CHEMICAL VAPOR DE...N00014- 86-C-0838 during:the period -from I July 1080 to 30 September 1089 . Funding is being provided by the Strateg’c Defense Initiative under the

  9. Control of interface nanoscale structure created by plasma-enhanced chemical vapor deposition.

    PubMed

    Peri, Someswara R; Akgun, Bulent; Satija, Sushil K; Jiang, Hao; Enlow, Jesse; Bunning, Timothy J; Foster, Mark D

    2011-09-01

    Tailoring the structure of films deposited by plasma-enhanced chemical vapor deposition (PECVD) to specific applications requires a depth-resolved understanding of how the interface structures in such films are impacted by variations in deposition parameters such as feed position and plasma power. Analysis of complementary X-ray and neutron reflectivity (XR, NR) data provide a rich picture of changes in structure with feed position and plasma power, with those changes resolved on the nanoscale. For plasma-polymerized octafluorocyclobutane (PP-OFCB) films, a region of distinct chemical composition and lower cross-link density is found at the substrate interface for the range of processing conditions studied and a surface layer of lower cross-link density also appears when plasma power exceeds 40 W. Varying the distance of the feed from the plasma impacts the degree of cross-linking in the film center, thickness of the surface layer, and thickness of the transition region at the substrate. Deposition at the highest power, 65 W, both enhances cross-linking and creates loose fragments with fluorine content higher than the average. The thickness of the low cross-link density region at the air interface plays an important role in determining the width of the interface built with a layer subsequently deposited atop the first.

  10. Fluorinated carboxylic membranes deposited by plasma enhanced chemical vapour deposition for fuel cell applications

    NASA Astrophysics Data System (ADS)

    Thery, J.; Martin, S.; Faucheux, V.; Le Van Jodin, L.; Truffier-Boutry, D.; Martinent, A.; Laurent, J.-Y.

    Among the fuel cell technologies, the polymer electrolyte membrane fuel cells (PEMFCs) are particularly promising because they are energy-efficient, clean, and fuel-flexible (i.e., can use hydrogen or methanol). The great majority of PEM fuel cells rely on a polymer electrolyte from the family of perfluorosulfonic acid membranes, nevertheless alternative materials are currently being developed, mainly to offer the alternative workout techniques which are required for the portable energy sources. Plasma polymerization represents a good solution, as it offers the possibility to deposit thin layer with an accurate and homogeneous thickness, even on 3D surfaces. In this paper, we present the results for the growth of proton conductive fluoro carboxylic membranes elaborated by plasma enhanced chemical vapour deposition. These membranes present conductivity values of the same order than the one of Nafion ®. The properties of the membrane, such as the chemical composition, the ionic conductivity, the swelling behaviour and the permeability were correlated to the plasma process parameters. The membranes were integrated in fuel cells on porous substrates and we present here the results regarding the barrier effect and the power output. Barrier effect similar to those of 40 μm Nafion ® layers was reached for 10 μm thick carboxylic membranes. Power outputs around 3 mW cm -2 were measured. We discuss the results regarding the gas barrier effect and the power outputs.

  11. Chain Assemblies from Nanoparticles Synthesized by Atmospheric Pressure Plasma Enhanced Chemical Vapor Deposition: The Computational View.

    PubMed

    Mishin, Maxim V; Zamotin, Kirill Y; Protopopova, Vera S; Alexandrov, Sergey E

    2015-12-01

    This article refers to the computational study of nanoparticle self-organization on the solid-state substrate surface with consideration of the experimental results, when nanoparticles were synthesised during atmospheric pressure plasma enhanced chemical vapor deposition (AP-PECVD). The experimental study of silicon dioxide nanoparticle synthesis by AP-PECVD demonstrated that all deposit volume consists of tangled chains of nanoparticles. In certain cases, micron-sized fractals are formed from tangled chains due to deposit rearrangement. This work is focused on the study of tangled chain formation only. In order to reveal their formation mechanism, a physico-mathematical model was developed. The suggested model was based on the motion equation solution for charged and neutral nanoparticles in the potential fields with the use of the empirical interaction potentials. In addition, the computational simulation was carried out based on the suggested model. As a result, the influence of such experimental parameters as deposition duration, particle charge, gas flow velocity, and angle of gas flow was found. It was demonstrated that electrical charges carried by nanoparticles from the discharge area are not responsible for the formation of tangled chains from nanoparticles, whereas nanoparticle kinetic energy plays a crucial role in deposit morphology and density. The computational results were consistent with experimental results.

  12. Plasma-enhanced chemical vapor deposition synthesis of vertically oriented graphene nanosheets.

    PubMed

    Bo, Zheng; Yang, Yong; Chen, Junhong; Yu, Kehan; Yan, Jianhua; Cen, Kefa

    2013-06-21

    Vertically oriented graphene (VG) nanosheets have attracted growing interest for a wide range of applications, from energy storage, catalysis and field emission to gas sensing, due to their unique orientation, exposed sharp edges, non-stacking morphology, and huge surface-to-volume ratio. Plasma-enhanced chemical vapor deposition (PECVD) has emerged as a key method for VG synthesis; however, controllable growth of VG with desirable characteristics for specific applications remains a challenge. This paper attempts to summarize the state-of-the-art research on PECVD growth of VG nanosheets to provide guidelines on the design of plasma sources and operation parameters, and to offer a perspective on outstanding challenges that need to be overcome to enable commercial applications of VG. The review starts with an overview of various types of existing PECVD processes for VG growth, and then moves on to research on the influences of feedstock gas, temperature, and pressure on VG growth, substrate pretreatment, the growth of VG patterns on planar substrates, and VG growth on cylindrical and carbon nanotube (CNT) substrates. The review ends with a discussion on challenges and future directions for PECVD growth of VG.

  13. Boron nitride nanowalls: low-temperature plasma-enhanced chemical vapor deposition synthesis and optical properties.

    PubMed

    Merenkov, Ivan S; Kosinova, Marina L; Maximovskii, Eugene A

    2017-05-05

    Hexagonal boron nitride (h-BN) nanowalls (BNNWs) were synthesized by plasma-enhanced chemical vapor deposition (PECVD) from a borazine (B3N3H6) and ammonia (NH3) gas mixture at a low temperature range of 400 °C-600 °C on GaAs(100) substrates. The effect of the synthesis temperature on the structure and surface morphology of h-BN films was investigated. The length and thickness of the h-BN nanowalls were in the ranges of 50-200 nm and 15-30 nm, respectively. Transmission electron microscope images showed the obtained BNNWs were composed of layered non-equiaxed h-BN nanocrystallites 5-10 nm in size. The parallel-aligned h-BN layers as an interfacial layer were observed between the film and GaAs(100) substrate. BNNWs demonstrate strong blue light emission, high transparency (>90%) both in visible and infrared spectral regions and are promising for optical applications. The present results enable a convenient growth of BNNWs at low temperatures.

  14. Growth of ultrananocrystalline diamond film by DC Arcjet plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Chen, G. C.; Li, B.; Yan, Z. Q.; Liu, J.; Lu, F. X.; Ye, H.

    2012-06-01

    Self-standing diamond films were grown by DC Arcjet plasma enhanced chemical vapor deposition (CVD). The feed gasses were Ar/H2/CH4, in which the flow ratio of CH4 to H2 (F/F) was varied from 5% to 20%. Two distinct morphologies were observed by scanning electron microscope (SEM), i.e. the "pineapple-like" morphology and the "cauliflower-like" morphology. It was found that the morphologies of the as-grown films are strongly dependent on the flow ratio of CH4 to H2 in the feed gasses. High resolution transmission electron microscope (HRTEM) survey results revealed that there were nanocrystalline grains within the "pineapple-like" films whilst there were ultrananocrystalline grains within "cauliflower-like" films. X-ray diffraction (XRD) results suggested that (110) crystalline plane was the dominant surface in the "cauliflower-like" films whilst (100) crystalline plane was the dominant surface in the "pineapple-like" films. Raman spectroscopy revealed that nanostructured carbon features could be observed in both types of films. Plasma diagnosis was carried out in order to understand the morphology dependent growth mechanism. It could be concluded that the film morphology was strongly influenced by the density of gas phases. The gradient of C2 radical was found to be different along the growth direction under the different growth conditions.

  15. Passivation of aluminum nanoparticles by plasma-enhanced chemical vapor deposition for energetic nanomaterials.

    PubMed

    Shahravan, Anaram; Desai, Tapan; Matsoukas, Themis

    2014-05-28

    We have produced passivating coatings on 80-nm aluminum particles by plasma-enhanced chemical vapor deposition (PECVD). Three organic precursors--isopropyl alcohol, toluene, and perfluorodecalin--were used to fabricate thin films with thicknesses ranging from 5 nm to 30 nm. The coated samples and one untreated sample were exposed to 85% humidity at 25 °C for two months, and the active Al content was determined by thermogravimetric analysis (TGA) in the presence of oxygen. The results were compared with an uncoated sample stored in a glovebox under argon for the same period. We find that all three coatings provide protection against humidity, compared to the control, and their efficacy ranks in the following order: isopropyl alcohol < toluene < perfluorodecalin. This order also correlates with increasing water contact angle of the three solid coatings. The amount of heat released in the oxidation, measured by differential scanning calorimetry (DSC), was found to increase in the same order. Perfluorodecalin resulted in providing the best protection, and it produced the maximum enthalpy of combustion, ΔH = 4.65 kJ/g. This value is higher than that of uncoated aluminum stored in the glovebox, indicating that the coatings promote more complete oxidation of the core. Overall, we conclude that the plasma polymer coatings of this study are suitable passivating thin film for aluminum nanoparticles by providing protection against oxidation while facilitating the complete oxidation of the metallic core at elevated temperature.

  16. Modeling of Sheath Ion-Molecule Reactions in Plasma Enhanced Chemical Vapor Deposition of Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Hash, David B.; Govindan, T. R.; Meyyappan, M.

    2004-01-01

    In many plasma simulations, ion-molecule reactions are modeled using ion energy independent reaction rate coefficients that are taken from low temperature selected-ion flow tube experiments. Only exothermic or nearly thermoneutral reactions are considered. This is appropriate for plasma applications such as high-density plasma sources in which sheaths are collisionless and ion temperatures 111 the bulk p!asma do not deviate significantly from the gas temperature. However, for applications at high pressure and large sheath voltages, this assumption does not hold as the sheaths are collisional and ions gain significant energy in the sheaths from Joule heating. Ion temperatures and thus reaction rates vary significantly across the discharge, and endothermic reactions become important in the sheaths. One such application is plasma enhanced chemical vapor deposition of carbon nanotubes in which dc discharges are struck at pressures between 1-20 Torr with applied voltages in the range of 500-700 V. The present work investigates The importance of the inclusion of ion energy dependent ion-molecule reaction rates and the role of collision induced dissociation in generating radicals from the feedstock used in carbon nanotube growth.

  17. Structural and optical properties of silicon nanocrystals grown by plasma-enhanced chemical vapor deposition.

    PubMed

    Prakash, G V; Daldosso, N; Degoli, E; Iacona, F; Cazzanelli, M; Gaburro, Z; Pucker, G; Dalba, P; Rocca, F; Ceretta Moreira, E; Franzò, G; Pacifici, D; Priolo, F; Arcangeli, C; Filonov, A B; Ossicini, S; Pavesi, L

    2001-06-01

    Silicon nanocrystals (Si-nc) embedded in SiO2 matrix have been prepared by high temperature thermal annealing (1000-1250 degrees C) of substoichiometric SiOx films deposited by plasma-enhanced chemical vapor deposition (PECVD). Different techniques have been used to examine the optical and structural properties of Si-nc. Transmission electron microscopy analysis shows the formation of nanocrystals whose sizes are dependent on annealing conditions and deposition parameters. The spectral positions of room temperature photoluminescence are systematically blue shifted with reduction in the size of Si-nc obtained by decreasing the annealing temperature or the Si content during the PECVD deposition. A similar trend has been found in optical absorption measurements. X-ray absorption fine structure measurements indicate the presence of an intermediate region between the Si-nc and the SiO2 matrix that participates in the light emission process. Theoretical observations reported here support these findings. All these efforts allow us to study the link between dimensionality, optical properties, and the local environment of Si-nc and the surrounding SiO2 matrix.

  18. Conformal encapsulation of three-dimensional, bioresorbable polymeric scaffolds using plasma-enhanced chemical vapor deposition.

    PubMed

    Hawker, Morgan J; Pegalajar-Jurado, Adoracion; Fisher, Ellen R

    2014-10-21

    Bioresorbable polymers such as poly(ε-caprolactone) (PCL) have a multitude of potential biomaterial applications such as controlled-release drug delivery and regenerative tissue engineering. For such biological applications, the fabrication of porous three-dimensional bioresorbable materials with tunable surface chemistry is critical to maximize their surface-to-volume ratio, mimic the extracellular matrix, and increase drug-loading capacity. Here, two different fluorocarbon (FC) precursors (octofluoropropane (C3F8) and hexafluoropropylene oxide (HFPO)) were used to deposit FC films on PCL scaffolds using plasma-enhanced chemical vapor deposition (PECVD). These two coating systems were chosen with the intent of modifying the scaffold surfaces to be bio-nonreactive while maintaining desirable bulk properties of the scaffold. X-ray photoelectron spectroscopy showed high-CF2 content films were deposited on both the exterior and interior of PCL scaffolds and that deposition behavior is PECVD system specific. Scanning electron microscopy data confirmed that FC film deposition yielded conformal rather than blanket coatings as the porous scaffold structure was maintained after plasma treatment. Treated scaffolds seeded with human dermal fibroblasts (HDF) demonstrate that the cells do not attach after 72 h and that the scaffolds are noncytotoxic to HDF. This work demonstrates conformal FC coatings can be deposited on 3D polymeric scaffolds using PECVD to fabricate 3D bio-nonreactive materials.

  19. Optimization of silicon oxynitrides by plasma-enhanced chemical vapor deposition for an interferometric biosensor

    NASA Astrophysics Data System (ADS)

    Choo, Sung Joong; Lee, Byung-Chul; Lee, Sang-Myung; Park, Jung Ho; Shin, Hyun-Joon

    2009-09-01

    In this paper, silicon oxynitride layers deposited with different plasma-enhanced chemical vapor deposition (PECVD) conditions were fabricated and optimized, in order to make an interferometric sensor for detecting biochemical reactions. For the optimization of PECVD silicon oxynitride layers, the influence of the N2O/SiH4 gas flow ratio was investigated. RF power in the PEVCD process was also adjusted under the optimized N2O/SiH4 gas flow ratio. The optimized silicon oxynitride layer was deposited with 15 W in chamber under 25/150 sccm of N2O/SiH4 gas flow rates. The clad layer was deposited with 20 W in chamber under 400/150 sccm of N2O/SiH4 gas flow condition. An integrated Mach-Zehnder interferometric biosensor based on optical waveguide technology was fabricated under the optimized PECVD conditions. The adsorption reaction between bovine serum albumin (BSA) and the silicon oxynitride surface was performed and verified with this device.

  20. Thermal Conductivity of Nanocrystalline Silicon Prepared by Plasma-Enhanced Chemical-Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Jugdersuren, Battogtokh; Liu, Xiao; Kearney, Brian; Queen, Daniel; Metcalf, Thomas; Culbertson, James; Chervin, Christopher; Katz, Michael; Stroud, Rhonda

    Nanocrystallization by ball milling has been used successfully to reduce the thermal conductivity of silicon-germanium alloys (SiGe) and turn them into useful thermoelectric materials at a temperature of a few hundred degrees C. Currently the smallest grain sizes in nanocrystalline SiGe are in the 10 nm range. Germanium is added to scatter short wavelength phonons by impurity scattering. In this work, we report a record low thermal conductivity in nanocrystalline silicon prepared by plasma-enhanced chemical-vapor deposition. By varying hydrogen to silane ratio, we can vary the average grain sizes from greater than 10 nm down to 3 nm, as determined by both the high resolution transmission electron microscopy and X-ray diffraction. The values of thermal conductivity, as measured by the 3 ω technique, can be correspondingly modulated from that of ball-milled nanocrystalline SiGe to a record low level of 0.3 W/mK at room temperature. This low thermal conductivity is only about 1/3 of the minimum thermal conductivity limit of silicon. Possible causes of such a large reduction are discussed. Work supported by the Office of Naval Research.

  1. Structural and chemical analysis of annealed plasma-enhanced atomic layer deposition aluminum nitride films

    SciTech Connect

    Broas, Mikael Vuorinen, Vesa; Sippola, Perttu; Pyymaki Perros, Alexander; Lipsanen, Harri; Sajavaara, Timo; Paulasto-Kröckel, Mervi

    2016-07-15

    Plasma-enhanced atomic layer deposition was utilized to grow aluminum nitride (AlN) films on Si from trimethylaluminum and N{sub 2}:H{sub 2} plasma at 200 °C. Thermal treatments were then applied on the films which caused changes in their chemical composition and nanostructure. These changes were observed to manifest in the refractive indices and densities of the films. The AlN films were identified to contain light element impurities, namely, H, C, and excess N due to nonideal precursor reactions. Oxygen contamination was also identified in the films. Many of the embedded impurities became volatile in the elevated annealing temperatures. Most notably, high amounts of H were observed to desorb from the AlN films. Furthermore, dinitrogen triple bonds were identified with infrared spectroscopy in the films. The triple bonds broke after annealing at 1000 °C for 1 h which likely caused enhanced hydrolysis of the films. The nanostructure of the films was identified to be amorphous in the as-deposited state and to become nanocrystalline after 1 h of annealing at 1000 °C.

  2. Preparation and structure of porous dielectrics by plasma enhanced chemical vapor deposition

    SciTech Connect

    Gates, S. M.; Neumayer, D. A.; Sherwood, M. H.; Grill, A.; Wang, X.; Sankarapandian, M.

    2007-05-01

    The preparation of ultralow dielectric constant porous silicon, carbon, oxygen, hydrogen alloy dielectrics, called 'pSiCOH', using a production 200 mm plasma enhanced chemical vapor deposition tool and a thermal treatment is reported here. The effect of deposition temperature on the pSiCOH film is examined using Fourier transform infrared (FTIR) spectroscopy, dielectric constant (k), and film shrinkage measurements. For all deposition temperatures, carbon in the final porous film is shown to be predominantly Si-CH{sub 3} species, and lower k is shown to correlate with increased concentration of Si-CH{sub 3}. NMR and FTIR spectroscopies clearly detect the loss of a removable, unstable, hydrocarbon (CH{sub x}) phase during the thermal treatment. Also detected are increased cross-linking of the Si-O skeleton, and concentration changes for three distinct structures of carbon. In the as deposited films, deposition temperature also affects the hydrocarbon (CH{sub x}) content and the presence of C=O and C=C functional groups.

  3. Boron nitride nanowalls: low-temperature plasma-enhanced chemical vapor deposition synthesis and optical properties

    NASA Astrophysics Data System (ADS)

    Merenkov, Ivan S.; Kosinova, Marina L.; Maximovskii, Eugene A.

    2017-05-01

    Hexagonal boron nitride (h-BN) nanowalls (BNNWs) were synthesized by plasma-enhanced chemical vapor deposition (PECVD) from a borazine (B3N3H6) and ammonia (NH3) gas mixture at a low temperature range of 400 °C-600 °C on GaAs(100) substrates. The effect of the synthesis temperature on the structure and surface morphology of h-BN films was investigated. The length and thickness of the h-BN nanowalls were in the ranges of 50-200 nm and 15-30 nm, respectively. Transmission electron microscope images showed the obtained BNNWs were composed of layered non-equiaxed h-BN nanocrystallites 5-10 nm in size. The parallel-aligned h-BN layers as an interfacial layer were observed between the film and GaAs(100) substrate. BNNWs demonstrate strong blue light emission, high transparency (>90%) both in visible and infrared spectral regions and are promising for optical applications. The present results enable a convenient growth of BNNWs at low temperatures.

  4. Preparation of amorphous electrochromic tungsten oxide and molybdenum oxide by plasma enhanced chemical vapor deposition

    SciTech Connect

    Tracy, C.E.; Benson, D.K.

    1986-09-01

    Preliminary experiments have been performed to probe the feasibility of using plasma enhanced chemical vapor deposition (PE--CVD) to prepare electrochromic thin films of tungsten oxide and molybdenum oxide by plasma reaction of WF/sub 6/, W(CO)/sub 6/, and Mo(CO)/sub 6/ with oxygen. Thin films produced in a 300 W, electrodeless, radio-frequency (rf), capacitive discharge were found to be electrochromic when tested with either liquid or solid electrolytes. Optical spectroscopy was performed on two electrochromic coatings after Li/sup +/ ion insertion from a propylene carbonate liquid electrolyte. Broad absorption peaks at --900 nm for WO/sub 3/ and 600 nm for MoO/sub 3/ were observed. Optical results for PE--CVD MoO/sub 3/ films differ from those reported for evaporated MoO/sub 3/ films which have an absorption peak at --800 nm. The shorter wavelength absorption in the PE--CVD MoO/sub 3/ films offers the potential for fabricating electrochromic devices with higher contrast ratios and less color change. Optical emission spectroscopy, Auger, and x-ray diffraction analyses indicate these thin film deposits to be predominantly amorphous tungsten and molybdenum oxides.

  5. Characterization of diamond-like nanocomposite thin films grown by plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Santra, T. S.; Liu, C. H.; Bhattacharyya, T. K.; Patel, P.; Barik, T. K.

    2010-06-01

    Diamond-like nanocomposite (DLN) thin films, comprising the networks of a-C:H and a-Si:O were deposited on pyrex glass or silicon substrate using gas precursors (e.g., hexamethyldisilane, hexamethyldisiloxane, hexamethyldisilazane, or their different combinations) mixed with argon gas, by plasma enhanced chemical vapor deposition technique. Surface morphology of DLN films was analyzed by atomic force microscopy. High-resolution transmission electron microscopic result shows that the films contain nanoparticles within the amorphous structure. Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and x-ray photoelectron spectroscopy (XPS) were used to determine the structural change within the DLN films. The hardness and friction coefficient of the films were measured by nanoindentation and scratch test techniques, respectively. FTIR and XPS studies show the presence of CC, CH, SiC, and SiH bonds in the a-C:H and a-Si:O networks. Using Raman spectroscopy, we also found that the hardness of the DLN films varies with the intensity ratio ID/IG. Finally, we observed that the DLN films has a better performance compared to DLC, when it comes to properties like high hardness, high modulus of elasticity, low surface roughness and low friction coefficient. These characteristics are the critical components in microelectromechanical systems (MEMS) and emerging nanoelectromechanical systems (NEMS).

  6. Preparation Of Electrochromic Metal Oxide Films By Plasma-Enhanced Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Benson, D. K.; Tracy, C. E.; Svensson, J. S. E. M.; Liebert, B. E.

    1987-11-01

    Laboratory procedures have been developed for depositing thin films of electrochromic metal oxides by plasma-enhanced chemical vapor deposition (PE-CVD). In this process, vapor phase reactants, such as tungsten hexafluotIde, are mixed with oxygen and excited by RF energy at a frequency of 13.56 MHz and power levels up to≍1W/cm2 substrate area. Large rates of oxide deposition have been achieved (> 8 nm/s) making this process a candidate for high-speed coating of large area substrates, such as window glass. Amorphous WO1 films prepared by PE-CVD have been shown to have electrochromic responses virtually identical to films prepared by vacuum evaporation. The lithium ion diffusion rate, for example, is approximately 1.3 x 10-11 cm2 /s at x = 0.03 in LixWO3 prepared by PE-CVD. On the other hand, molybdenum oxide films and mixed molybdenum/tungsten oxide films prepared by PE-CVD from the hexafluorides differ markedly from vacuum evaporated films. Their electrochromic responses are spectrally different and are much slower. Lithium ion diffusion rates in such Mo03 films are lower by about three orders of magnitude. These differences are tentatively attributed to a large fraction of fluorine (Mo:F ratios of the order of 2:1) which are incorporated into the molybdenum and mixed oxides, but are not incorporated into the tungsten oxides.

  7. Growth and characterization of silicon-nitride films by plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Han, I. K.; Lee, Y. J.; Jo, J. W.; Lee, J. I.; Kang, K. N.

    1991-06-01

    Thin films of silicon nitride were deposited on Si wafers by plasma-enhanced chemical vapor deposition (PECVD). For deposition we designed and made hot wall capacitively coupled PECVD equipment which has a radial flow reactor. Using an RF generator of frequency 13.56 MHz and SiH 4 (5% SiH 4 in N 2) + NH 3 and N 2 as reactive gases and the carrier gas, respectively, we systematically varied the substrate temperature (240-360°C), the partial pressure of reactive gases (0.35

  8. Wetting behaviour of carbon nitride nanostructures grown by plasma enhanced chemical vapour deposition technique

    NASA Astrophysics Data System (ADS)

    Ahmad Kamal, Shafarina Azlinda; Ritikos, Richard; Abdul Rahman, Saadah

    2015-02-01

    Tuning the wettability of various coating materials by simply controlling the deposition parameters is essential for various specific applications. In this work, carbon nitride (CNx) films were deposited on silicon (1 1 1) substrates using radio-frequency plasma enhanced chemical vapour deposition employing parallel plate electrode configuration. Effects of varying the electrode distance (DE) on the films' structure and bonding properties were investigated using Field emission scanning electron microscopy, Atomic force microscopy, Fourier transform infrared and X-ray photoemission spectroscopy. The wettability of the films was analyzed using water contact angle measurements. At high DE, the CNx films' surface was smooth and uniform. This changed into fibrous nanostructures when DE was decreased. Surface roughness of the films increased with this morphological transformation. Nitrogen incorporation increased with decrease in DE which manifested the increase in both relative intensities of Cdbnd N to Cdbnd C and Nsbnd H to Osbnd H bonds. sp2-C to sp3-C ratio increased as DE decreased due to greater deformation of sp2 bonded carbon at lower DE. The films' characteristics changed from hydrophilic to super-hydrophobic with the decrease in DE. Roughness ratio, surface porosity and surface energy calculated from contact angle measurements were strongly dependent on the morphology, surface roughness and bonding properties of the films.

  9. Electrical transport properties of graphene nanowalls grown at low temperature using plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Zhao, Rong; Ahktar, Meysam; Alruqi, Adel; Dharmasena, Ruchira; Jasinski, Jacek B.; Thantirige, Rukshan M.; Sumanasekera, Gamini U.

    2017-05-01

    In this work, we report the electrical transport properties of uniform and vertically oriented graphene (graphene nanowalls) directly synthesized on multiple substrates including glass, Si/SiO2 wafers, and copper foils using radio-frequency plasma enhanced chemical vapor deposition (PECVD) with methane (CH4) as the precursor at relatively low temperatures. The temperature for optimum growth was established with the aid of transmission electron microscopy, scanning electron microscopy, and Raman spectroscopy. This approach offers means for low-cost graphene nanowalls growth on an arbitrary substrate with the added advantage of transfer-free device fabrication. The temperature dependence of the electrical transport properties (resistivity and thermopower) were studied in the temperature range, 30-300 K and analyzed with a combination of 2D-variable range hopping (VRH) and thermally activated (TA) conduction mechanisms. An anomalous temperature dependence of the thermopower was observed for all the samples and explained with a combination of a diffusion term having a linear temperature dependence plus a term with an inverse temperature dependence.

  10. Hydrogen peroxide sensor based on carbon nanowalls grown by plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Tomatsu, Masakazu; Hiramatsu, Mineo; Foord, John S.; Kondo, Hiroki; Ishikawa, Kenji; Sekine, Makoto; Takeda, Keigo; Hori, Masaru

    2017-06-01

    Fabrication of an electrochemical sensor for hydrogen peroxide (H2O2) detection was demonstrated. H2O2 is a major messenger molecule in various redox-dependent cellular signaling transductions. Therefore, sensitive detection of H2O2 is greatly important in health inspection and environmental protection. Carbon nanowalls (CNWs) are composed of few-layer graphenes standing almost vertically on a substrate forming a three-dimensional structure. In this work, CNWs were used as a platform for H2O2 sensing, which is based on the large surface area of conducting carbon and surface decoration with platinum (Pt) nanoparticles (NPs). CNWs were grown on carbon fiber paper (CFP) by inductively coupled plasma-enhanced chemical vapor deposition to increase the surface area. Then, the CNW surface was decorated with Pt-NPs by the reduction of H2PtCl6. Cyclic voltammetry results indicate that the Pt-decorated CNW/CFP electrode possesses excellent electrocatalytic activity for the reduction of H2O2. Amperometric responses indicate the high-sensitivity detection capability of the Pt-decorated CNW/CFP electrode for H2O2.

  11. Stress control of silicon nitride films deposited by plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Li, Dong-ling; Feng, Xiao-fei; Wen, Zhi-yu; Shang, Zheng-guo; She, Yin

    2016-07-01

    Stress controllable silicon nitride (SiNx) films deposited by plasma enhanced chemical vapor deposition (PECVD) are reported. Low stress SiNx films were deposited in both high frequency (HF) mode and dual frequency (HF/LF) mode. By optimizing process parameters, stress free (-0.27 MPa) SiNx films were obtained with the deposition rate of 45.5 nm/min and the refractive index of 2.06. Furthermore, at HF/LF mode, the stress is significantly influenced by LF ratio and LF power, and can be controlled to be 10 MPa with the LF ratio of 17% and LF power of 150 W. However, LF power has a little effect on the deposition rate due to the interaction between HF power and LF power. The deposited SiNx films have good mechanical and optical properties, low deposition temperature and controllable stress, and can be widely used in integrated circuit (IC), micro-electro-mechanical systems (MEMS) and bio-MEMS.

  12. Gettering of interstitial iron in silicon by plasma-enhanced chemical vapour deposited silicon nitride films

    NASA Astrophysics Data System (ADS)

    Liu, A. Y.; Sun, C.; Markevich, V. P.; Peaker, A. R.; Murphy, J. D.; Macdonald, D.

    2016-11-01

    It is known that the interstitial iron concentration in silicon is reduced after annealing silicon wafers coated with plasma-enhanced chemical vapour deposited (PECVD) silicon nitride films. The underlying mechanism for the significant iron reduction has remained unclear and is investigated in this work. Secondary ion mass spectrometry (SIMS) depth profiling of iron is performed on annealed iron-contaminated single-crystalline silicon wafers passivated with PECVD silicon nitride films. SIMS measurements reveal a high concentration of iron uniformly distributed in the annealed silicon nitride films. This accumulation of iron in the silicon nitride film matches the interstitial iron loss in the silicon bulk. This finding conclusively shows that the interstitial iron is gettered by the silicon nitride films during annealing over a wide temperature range from 250 °C to 900 °C, via a segregation gettering effect. Further experimental evidence is presented to support this finding. Deep-level transient spectroscopy analysis shows that no new electrically active defects are formed in the silicon bulk after annealing iron-containing silicon with silicon nitride films, confirming that the interstitial iron loss is not due to a change in the chemical structure of iron related defects in the silicon bulk. In addition, once the annealed silicon nitride films are removed, subsequent high temperature processes do not result in any reappearance of iron. Finally, the experimentally measured iron decay kinetics are shown to agree with a model of iron diffusion to the surface gettering sites, indicating a diffusion-limited iron gettering process for temperatures below 700 °C. The gettering process is found to become reaction-limited at higher temperatures.

  13. Si-nanocrystal-based LEDs fabricated by ion implantation and plasma-enhanced chemical vapour deposition.

    PubMed

    Perálvarez, M; Barreto, J; Carreras, Josep; Morales, A; Navarro-Urrios, D; Lebour, Y; Domínguez, C; Garrido, B

    2009-10-07

    An in-depth study of the physical and electrical properties of Si-nanocrystal-based MOSLEDs is presented. The active layers were fabricated with different concentrations of Si by both ion implantation and plasma-enhanced chemical vapour deposition. Devices fabricated by ion implantation exhibit a combination of direct current and field-effect luminescence under a bipolar pulsed excitation. The onset of the emission decreases with the Si excess from 6 to 3 V. The direct current emission is attributed to impact ionization and is associated with the reasonably high current levels observed in current-voltage measurements. This behaviour is in good agreement with transmission electron microscopy images that revealed a continuous and uniform Si nanocrystal distribution. The emission power efficiency is relatively low, approximately 10(-3)%, and the emission intensity exhibits fast degradation rates, as revealed from accelerated ageing experiments. Devices fabricated by chemical deposition only exhibit field-effect luminescence, whose onset decreases with the Si excess from 20 to 6 V. The absence of the continuous emission is explained by the observation of a 5 nm region free of nanocrystals, which strongly reduces the direct current through the gate. The main benefit of having this nanocrystal-free region is that tunnelling current flow assisted by nanocrystals is blocked by the SiO2 stack so that power consumption is strongly reduced, which in return increases the device power efficiency up to 0.1%. In addition, the accelerated ageing studies reveal a 50% degradation rate reduction as compared to implanted structures.

  14. CHEMICAL SYNTHESIS & TRANSFORMATIONS USING MICROWAVES

    EPA Science Inventory

    A historical account of the utility of microwaves in a variety of chemical synthesis applications will be presented, including a solvent-free strategy that involves microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of recyclable mineral supports such...

  15. CHEMICAL SYNTHESIS & TRANSFORMATIONS USING MICROWAVES

    EPA Science Inventory

    A historical account of the utility of microwaves in a variety of chemical synthesis applications will be presented, including a solvent-free strategy that involves microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of recyclable mineral supports such...

  16. Practical silicon deposition rules derived from silane monitoring during plasma-enhanced chemical vapor deposition

    SciTech Connect

    Bartlome, Richard De Wolf, Stefaan; Demaurex, Bénédicte; Ballif, Christophe; Amanatides, Eleftherios; Mataras, Dimitrios

    2015-05-28

    We clarify the difference between the SiH{sub 4} consumption efficiency η and the SiH{sub 4} depletion fraction D, as measured in the pumping line and the actual reactor of an industrial plasma-enhanced chemical vapor deposition system. In the absence of significant polysilane and powder formation, η is proportional to the film growth rate. Above a certain powder formation threshold, any additional amount of SiH{sub 4} consumed translates into increased powder formation rather than into a faster growing Si film. In order to discuss a zero-dimensional analytical model and a two-dimensional numerical model, we measure η as a function of the radio frequency (RF) power density coupled into the plasma, the total gas flow rate, the input SiH{sub 4} concentration, and the reactor pressure. The adjunction of a small trimethylboron flow rate increases η and reduces the formation of powder, while the adjunction of a small disilane flow rate decreases η and favors the formation of powder. Unlike η, D is a location-dependent quantity. It is related to the SiH{sub 4} concentration in the plasma c{sub p}, and to the phase of the growing Si film, whether the substrate is glass or a c-Si wafer. In order to investigate transient effects due to the RF matching, the precoating of reactor walls, or the introduction of a purifier in the gas line, we measure the gas residence time and acquire time-resolved SiH{sub 4} density measurements throughout the ignition and the termination of a plasma.

  17. Annealing and oxidation of silicon oxide films prepared by plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Chen, X. Y.; Lu, Y. F.; Tang, L. J.; Wu, Y. H.; Cho, B. J.; Xu, X. J.; Dong, J. R.; Song, W. D.

    2005-01-01

    We have investigated phase separation, silicon nanocrystal (Si NC) formation and optical properties of Si oxide (SiOx, 0plasma-enhanced chemical vapor deposition at different nitrous-oxide/silane flow ratios. The physical and optical properties of the SiOx films were studied as a result of high-vacuum annealing and thermal oxidation. X-ray photoelectron spectroscopy (XPS) reveals that the as-deposited films have a random-bonding or continuous-random-network structure with different oxidation states. After annealing at temperatures above 1000 °C, the intermediate Si continuum in XPS spectra (referring to the suboxide) split to Si peaks corresponding to SiO2 and elemental Si. This change indicates the phase separation of the SiOx into more stable SiO2 and Si clusters. Raman, high-resolution transmission electron microscopy and optical absorption confirmed the phase separation and the formation of Si NCs in the films. The size of Si NCs increases with increasing Si concentration in the films and increasing annealing temperature. Two photoluminescence (PL) bands were observed in the films after annealing. The ultraviolet (UV)-range PL with a peak fixed at 370-380 nm is independent of Si concentration and annealing temperature, which is a characteristic of defect states. Strong PL in red range shows redshifts from ˜600 to 900 nm with increasing Si concentration and annealing temperature, which supports the quantum confinement model. After oxidation of the high-temperature annealed films, the UV PL was almost quenched while the red PL shows continuous blueshifts with increasing oxidation time. The different oxidation behaviors further relate the UV PL to the defect states and the red PL to the recombination of quantum-confined excitions.

  18. Automation of a remote plasma-enhanced chemical vapor deposition system using LabVIEW

    NASA Astrophysics Data System (ADS)

    Sharma, Rajan; Fretwell, John L.; Vaihinger, Jochen; Banerjee, Sanjay K.

    1997-08-01

    The remote plasma-enhanced chemical vapor deposition (RPCVD) system is an experimental low temperature Si/Si-Ge epitaxy system. This paper describes an integrated hardware/software automation package developed for the RPCVD system. Aspects of the system controlled by the package include pneumatic gas valves, mass flow controllers (MFCs), and a temperature controller. The package was developed on an Apple Quadra 950 platform using LabVIEWTM 3.1 and associated data acquisition and control hardware supplied by National Instruments and other vendors. The software interface allows the user to operate the system through a virtual control panel which displays critical system parameters such as chamber pressure, chamber temperature and gas flow rates, along with the states of the gas valves and the MFCs. The system can also be run in the recipe mode, in which a sequence of steps are read in from an ExcelTM file. A simulation routine scans each recipe for possible errors such as violation of valve interlocks while the recipe is being loaded. All actions, whether in the manual mode or the recipe mode, are recorded in a log file. Finally, since many of the gases used in the RPCVD process are toxic and/or flammable, there is an emphasis on safety in the entire control scheme. A safety monitor routine constantly checks for valve interlocks and pressure-valve interlocks. Upon detecting an illegal state, it automatically takes necessary action to bring the system into a safe state. In addition to these software safety features, there are also hardware interlocks to deal with such situations as power outages.

  19. In situ nitrogen-doped graphene grown from polydimethylsiloxane by plasma enhanced chemical vapor deposition

    SciTech Connect

    Wang, Chundong; Zhou, Yungang; He, Lifang; Ng, Tsz-Wai; Hong, Guo; Wu, Qi-Hui; Gao, Fei; Lee, Chun-Sing; Zhang, Wenjun

    2013-01-21

    Due to its unique electronic properties and wide spectrum of promising applications, graphene has attracted much attention from scientists in various fields. Control and engineering of graphene’s semiconducting properties is considered to be the key of its applications in electronic devices. Here, we report a novel method to prepare in situ nitrogen-doped graphene by microwave plasma assisted chemical vapor deposition (CVD) using PDMS (Polydimethylsiloxane) as a solid carbon source. Based on this approach, the concentration of nitrogen-doping can be easily controlled via the flow rate of nitrogen during the CVD process. X-ray photoelectron spectroscopy results indicated that the nitrogen atoms doped into graphene lattice were mainly in the forms of pyridinic and pyrrolic structures. Moreover, first-principles calculations show that the incorporated nitrogen atoms can lead to p-type doping of graphene. This in situ approach provides a promising strategy to prepare graphene with controlled electronic properties.

  20. Electrochromic Devices Deposited on Low-Temperature Plastics by Plasma-Enhanced Chemical Vapor Deposition

    SciTech Connect

    Robbins, Joshua; Seman, Michael

    2005-09-20

    Electrochromic windows have been identified by the Basic energy Sciences Advisory committee as an important technology for the reduction of energy spent on heating and cooling in residential and commercial buildings. Electrochromic devices have the ability to reversibly alter their optical properties in response to a small electric field. By blocking ultraviolet and infrared radiation, while modulating the incoming visible radiation, electrochromics could reduce energy consumption by several Quads per year. This amounts to several percent of the total annual national energy expenditures. The purpose of this project was to demonstrate proof of concept for using plasma-enhanced chemical vapor deposition (PECVD) for depositing all five layers necessary for full electrochromic devices, as an alternative to sputtering techniques. The overall goal is to produce electrochromic devices on flexible polymer substrates using PECVD to significantly reduce the cost of the final product. We have successfully deposited all of the films necessary for a complete electrochromic devices using PECVD. The electrochromic layer, WO3, displayed excellent change in visible transmission with good switching times. The storage layer, V2O5, exhibited a high storage capacity and good clear state transmission. The electrolyte, Ta2O5, was shown to functional with good electrical resistivity to go along with the ability to transfer Li ions. There were issues with leakage over larger areas, which can be address with further process development. We developed a process to deposit ZnO:Ga with a sheet resistance of < 50 W/sq. with > 90% transmission. Although we were not able to deposit on polymers due to the temperatures required in combination with the inverted position of our substrates. Two types of full devices were produced. Devices with Ta2O5 were shown to be functional using small aluminum dots as the top contact. The polymer electrolyte devices were shown to have a clear state transmission of

  1. Green light emission from terbium doped silicon rich silicon oxide films obtained by plasma enhanced chemical vapor deposition.

    PubMed

    Podhorodecki, A; Zatryb, G; Misiewicz, J; Wojcik, J; Wilson, P R J; Mascher, P

    2012-11-30

    The effect of silicon concentration and annealing temperature on terbium luminescence was investigated for thin silicon rich silicon oxide films. The structures were deposited by means of plasma enhanced chemical vapor deposition. The structural properties of these films were investigated by Rutherford backscattering spectrometry, transmission electron microscopy and Raman scattering. The optical properties were investigated by means of photoluminescence and photoluminescence decay spectroscopy. It was found that both the silicon concentration in the film and the annealing temperature have a strong impact on the terbium emission intensity. In this paper, we present a detailed discussion of these issues and determine the optimal silicon concentration and annealing temperature.

  2. Green light emission from terbium doped silicon rich silicon oxide films obtained by plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Podhorodecki, A.; Zatryb, G.; Misiewicz, J.; Wojcik, J.; Wilson, P. R. J.; Mascher, P.

    2012-11-01

    The effect of silicon concentration and annealing temperature on terbium luminescence was investigated for thin silicon rich silicon oxide films. The structures were deposited by means of plasma enhanced chemical vapor deposition. The structural properties of these films were investigated by Rutherford backscattering spectrometry, transmission electron microscopy and Raman scattering. The optical properties were investigated by means of photoluminescence and photoluminescence decay spectroscopy. It was found that both the silicon concentration in the film and the annealing temperature have a strong impact on the terbium emission intensity. In this paper, we present a detailed discussion of these issues and determine the optimal silicon concentration and annealing temperature.

  3. Utility of dual frequency hybrid source for plasma and radical generation in plasma enhanced chemical vapor deposition process

    NASA Astrophysics Data System (ADS)

    Shin, Kyung Sik; Bhusan Sahu, Bibhuti; Geon Han, Jeon; Hori, Masaru

    2015-07-01

    Looking into the aspect of material processing, this work evaluates alternative plasma concepts in SiH4/H2 plasmas to investigate the radical and plasma generation in the plasma enhanced chemical vapor deposition (PECVD) synthesis of nanocrystalline Si (nc-Si:H). Simultaneous measurements by vacuum ultraviolet absorption spectroscopy (VUVAS), optical emission spectroscopy (OES), and radio frequency (RF) compensated Langmuir probe (LP) reveal that RF/ultrahigh frequency (UHF) hybrid source can efficiently produce H radicals and plasmas that are accountable for nc-Si:H film synthesis. The efficacy of hybrid plasmas is also discussed.

  4. Microwave assisted chemical vapor infiltration

    SciTech Connect

    Devlin, D.J.; Currier, R.P.; Barbero, R.S.; Espinoza, B.F.; Elliott, N.

    1991-12-31

    A microwave assisted process for production of continuous fiber reinforced ceramic matrix composites is described. A simple apparatus combining a chemical vapor infiltration reactor with a conventional 700 W multimode oven is described. Microwave induced inverted thermal gradients are exploited with the ultimate goal of reducing processing times on complex shapes. Thermal gradients in stacks of SiC (Nicalon) cloths have been measured using optical thermometry. Initial results on the ``inside out`` deposition of SiC via decomposition of methyltrichlorosilane in hydrogen are presented. Several key processing issues are identified and discussed. 5 refs.

  5. Plasma-enhanced chemical vapor deposition of n-heptane and methyl methacrylate for potential cell alignment applications.

    PubMed

    Steinbach, Annina; Tautzenberger, Andrea; Schaller, Andreas; Kalytta-Mewes, Andreas; Tränkle, Sebastian; Ignatius, Anita; Volkmer, Dirk

    2012-10-24

    Plasma-enhanced chemical vapor deposited polymers (plasma polymers) are promising candidates for biomaterials applications. In the present study, plasma deposition as a fast and easily scalable method was adapted to deposit coatings from n-heptane and methyl methacrylate monomers onto glass substrates. Linear patterns with line and groove widths between 1.25 and 160 μm were introduced by degrative UV-lithography for cell alignment. Differential interference contrast optical microscopy, profilometry and atomic force microscopy revealed that the patterned surfaces had a smooth, homogeneous appearance and a pattern height of 8 and 45 nm for plasma deposited n-heptane and methyl methacrylate, respectively. UV-lithography increased the oxygen content on the surface drastically as shown by X-ray photoelectron spectroscopy. After immersion in simulated body fluid for 21 days, the pattern was still intact, and the ester groups were also maintained for the most part as shown by infrared spectroscopy. To test the coatings' potential applicability for biomaterial surfaces in a preliminary experiment, we cultured murine preosteoblastic MC3T3-E1 cells on these coatings. Light and electron microscopically, a normal spindle-shaped and aligned cell morphology was observed. At the mRNA level, cells showed no signs of diminished proliferation or elevated expression of apoptosis markers. In conclusion, plasma-enhanced chemical vapor deposited polymers can be patterned with a fast and feasible method and might be suitable materials to guide cell alignment.

  6. Plasma-enhanced chemical vapor deposition of graphene on copper substrates

    SciTech Connect

    Woehrl, Nicolas Schulz, Stephan; Ochedowski, Oliver; Gottlieb, Steven; Shibasaki, Kosuke

    2014-04-15

    A plasma enhanced vapor deposition process is used to synthesize graphene from a hydrogen/methane gas mixture on copper samples. The graphene samples were transferred onto SiO{sub 2} substrates and characterized by Raman spectroscopic mapping and atomic force microscope topographical mapping. Analysis of the Raman bands shows that the deposited graphene is clearly SLG and that the sheets are deposited on large areas of several mm{sup 2}. The defect density in the graphene sheets is calculated using Raman measurements and the influence of the process pressure on the defect density is measured. Furthermore the origin of these defects is discussed with respect to the process parameters and hence the plasma environment.

  7. Optical emission study of a doped diamond deposition process by plasma enhanced chemical vapor deposition

    SciTech Connect

    Rayar, M.; Supiot, P.; Veis, P.; Gicquel, A.

    2008-08-01

    Standard H{sub 2}/CH{sub 4}/B{sub 2}H{sub 6} plasmas (99% of H{sub 2} and 1% of CH{sub 4}, with 0-100 ppm of B{sub 2}H{sub 6} added) used for doped diamond film growth are studied by optical emission spectroscopy in order to gain a better understanding of the influence of boron species on the gas phase chemistry. Only two boron species are detected under our experimental conditions (9/15/23 W cm{sup -3} average microwave power density values), and the emission spectra used for studies reported here are B({sup 2}S{sub 1/2}-{sup 2}P{sub 1/2,3/2}{sup 0}) and BH[A {sup 1}{pi}-X {sup 1}{sigma}{sup +}(0,0)]. Variations of their respective emission intensities as a function of the ratio B/C, the boron to carbon ratio in the gas mixture, are reported. We confirmed that the plasma parameters (T{sub g}, T{sub e}, and n{sub e}) are not affected by the introduction of diborane, and the number densities of B atoms and BH radical species were estimated from experimental measurements. The results are compared to those obtained from a zero-dimensional chemical kinetic model where two groups of reactions are considered: (1) BH{sub x}+H{r_reversible}BH{sub x-1}+H{sub 2} (x=1-3) by analogy with the well-known equilibrium CH{sub x}+H set of reactions, which occurs, in particular, in diamond deposition reactors; and (2) from conventional organic chemistry, the set of reactions involving boron species: BH{sub x}+C{sub 2}H{sub 2} (x=0-1). The results clearly show that the model based on hydrogen and boron hydrides reactions alone is not consistent with the experimental results, while it is so when taking into account both sets of reactions. Once an upper limit for the boron species number densities has been estimated, axial profiles are calculated on the basis of the plasma model results obtained previously in Laboratoire d'Ingenierie des Materiaux et des Hautes Pressions, and significant differences in trends for different boron species are found. At the plasma-to-substrate boundary

  8. Optical emission study of a doped diamond deposition process by plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Rayar, M.; Supiot, P.; Veis, P.; Gicquel, A.

    2008-08-01

    Standard H2/CH4/B2H6 plasmas (99% of H2 and 1% of CH4, with 0-100ppm of B2H6 added) used for doped diamond film growth are studied by optical emission spectroscopy in order to gain a better understanding of the influence of boron species on the gas phase chemistry. Only two boron species are detected under our experimental conditions (9/15/23Wcm-3 average microwave power density values), and the emission spectra used for studies reported here are B(S1/22-P1/2,3/202) and BH [AΠ1-XΣ+1(0,0)]. Variations of their respective emission intensities as a function of the ratio B /C, the boron to carbon ratio in the gas mixture, are reported. We confirmed that the plasma parameters (Tg, Te, and ne) are not affected by the introduction of diborane, and the number densities of B atoms and BH radical species were estimated from experimental measurements. The results are compared to those obtained from a zero-dimensional chemical kinetic model where two groups of reactions are considered: (1) BHx+H ↔BHx -1+H2 (x=1-3) by analogy with the well-known equilibrium CHx+H set of reactions, which occurs, in particular, in diamond deposition reactors; and (2) from conventional organic chemistry, the set of reactions involving boron species: BHx+C2H2 (x =0-1). The results clearly show that the model based on hydrogen and boron hydrides reactions alone is not consistent with the experimental results, while it is so when taking into account both sets of reactions. Once an upper limit for the boron species number densities has been estimated, axial profiles are calculated on the basis of the plasma model results obtained previously in Laboratoire d'Ingénierie des Matériaux et des Hautes Pressions, and significant differences in trends for different boron species are found. At the plasma-to-substrate boundary, [BH] and [B] drop off in contrast to [BH2], which shows little decrease, and [BH3], which shows little increase, in this region.

  9. Plasma enhanced chemical vapor deposition (PECVD) method of forming vanadium oxide films and vanadium oxide thin-films prepared thereby

    DOEpatents

    Zhang, Ji-Guang; Tracy, C. Edwin; Benson, David K.; Turner, John A.; Liu, Ping

    2000-01-01

    A method is disclosed of forming a vanadium oxide film on a substrate utilizing plasma enhanced chemical vapor deposition. The method includes positioning a substrate within a plasma reaction chamber and then forming a precursor gas comprised of a vanadium-containing chloride gas in an inert carrier gas. This precursor gas is then mixed with selected amounts of hydrogen and oxygen and directed into the reaction chamber. The amounts of precursor gas, oxygen and hydrogen are selected to optimize the final properties of the vanadium oxide film An rf plasma is generated within the reaction chamber to chemically react the precursor gas with the hydrogen and the oxygen to cause deposition of a vanadium oxide film on the substrate while the chamber deposition pressure is maintained at about one torr or less. Finally, the byproduct gases are removed from the plasma reaction chamber.

  10. Cell proliferation on modified DLC thin films prepared by plasma enhanced chemical vapor deposition.

    PubMed

    Stoica, Adrian; Manakhov, Anton; Polčák, Josef; Ondračka, Pavel; Buršíková, Vilma; Zajíčková, Renata; Medalová, Jiřina; Zajíčková, Lenka

    2015-06-12

    Recently, diamondlike carbon (DLC) thin films have gained interest for biological applications, such as hip and dental prostheses or heart valves and coronary stents, thanks to their high strength and stability. However, the biocompatibility of the DLC is still questionable due to its low wettability and possible mechanical failure (delamination). In this work, DLC:N:O and DLC: SiOx thin films were comparatively investigated with respect to cell proliferation. Thin DLC films with an addition of N, O, and Si were prepared by plasma enhanced CVD from mixtures of methane, hydrogen, and hexamethyldisiloxane. The films were optically characterized by infrared spectroscopy and ellipsometry in UV-visible spectrum. The thickness and the optical properties were obtained from the ellipsometric measurements. Atomic composition of the films was determined by Rutherford backscattering spectroscopy combined with elastic recoil detection analysis and by x-ray photoelectron spectroscopy. The mechanical properties of the films were studied by depth sensing indentation technique. The number of cells that proliferate on the surface of the prepared DLC films and on control culture dishes were compared and correlated with the properties of as-deposited and aged films. The authors found that the level of cell proliferation on the coated dishes was high, comparable to the untreated (control) samples. The prepared DLC films were stable and no decrease of the biocompatibility was observed for the samples aged at ambient conditions.

  11. Silicon nanocrystals prepared by plasma enhanced chemical vapor deposition: Importance of parasitic oxidation for third generation photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Hartel, A. M.; Gutsch, S.; Hiller, D.; Kübel, C.; Zakharov, N.; Werner, P.; Zacharias, M.

    2012-11-01

    We report on an in-situ oxidation effect during annealing of SiO2/SiO1.0N0.23 multilayers prepared by plasma enhanced chemical vapour deposition (PECVD). This in-situ oxidation leads to an undesired growth of the tunneling oxide and also affects the silicon nanocrystal (SiNC) size control, i.e., a NC shrinkage. The origin of this oxidation is identified to be a "quasi-wet" oxidation by O-H groups incorporated in the PECVD-SiO2 barrier layers. By varying the thickness of the PECVD-SiO2 layer underneath a single SiO1.0N0.23 layer, the extent of NC oxidation is tuned. The shrinkage of SiNCs is proven by a blueshift of the photoluminescence peak position as well as by transmission electron microscopy.

  12. Sticking non-stick: Surface and Structure control of Diamond-like Carbon in Plasma Enhanced Chemical Vapour Deposition

    NASA Astrophysics Data System (ADS)

    Jones, B. J.; Nelson, N.

    2016-10-01

    This short review article explores the practical use of diamond-like carbon (DLC) produced by plasma enhanced chemical vapour deposition (PECVD). Using as an example issues relating to the DLC coating of a hand-held surgical device, we draw on previous works using atomic force microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, tensiometry and electron paramagnetic resonance. Utilising data from these techniques, we examine the surface structure, substrate-film interface and thin film microstructure, such as sp2/sp3 ratio (graphitic/diamond-like bonding ratio) and sp2 clustering. We explore the variations in parameters describing these characteristics, and relate these to the final device properties such as friction, wear resistance, and diffusion barrier integrity. The material and device characteristics are linked to the initial plasma and substrate conditions.

  13. The SiNx films process research by plasma-enhanced chemical vapor deposition in crystalline silicon solar cells

    NASA Astrophysics Data System (ADS)

    Chen, Bitao; Zhang, Yingke; Ouyang, Qiuping; Chen, Fei; Zhan, Xinghua; Gao, Wei

    2017-07-01

    SiNx thin film has been widely used in crystalline silicon solar cell production because of the good anti-reflection and passivation effect. We can effectively optimize the cells performance by plasma-enhanced chemical vapor deposition (PECVD) method to change deposition conditions such as temperature, gas flow ratio, etc. In this paper, we deposit a new layer of SiNx thin film on the basis of double-layers process. By changing the process parameters, the compactness of thin films is improved effectively. The NH3 passivation technology is augmented in a creative way, which improves the minority carrier lifetime. In sight of this, a significant increase is generated in the photoelectric performance of crystalline silicon solar cell.

  14. Effects of plasma-enhanced chemical vapor deposition (PECVD) on the carrier lifetime of Al2O3 passivation stack

    NASA Astrophysics Data System (ADS)

    Cho, Kuk-Hyun; Cho, Young Joon; Chang, Hyo Sik; Kim, Kyung-Joong; Song, Hee Eun

    2015-09-01

    We investigated the effect on the minority carrier lifetime of atomic layer deposition (ALD) Al2O3 passivation by a plasma-enhanced chemical vapor deposition (PECVD) SiON layer in Si/Al2O3/SiON-passivated structure. The lifetime variation of the Al2O3/SiON stack layer was found to depend on both the plasma power and the deposition temperature during the PECVD SiON process and to show better thermal stability than the Al2O3/SiNx:H stack under the same deposition conditions. The lifetime after a high-temperature firing process was improved dramatically at the PECVD deposition temperature of 200 °C. Our results provide a significant clue to reason for the improvement of the passivation performance for passivated emitter and rear contact (PERC) silicon solar cells.

  15. Effects of the growth conditions on the roughness of amorphous hydrogenated carbon films deposited by plasma enhanced chemical vapor deposition

    SciTech Connect

    Capote, G.; Prioli, R.; Freire, F. L. Jr.

    2006-11-15

    The surface roughness and scaling behavior of a-C:H films deposited by plasma enhanced chemical vapor deposition from CH{sub 4}-Ar mixtures were studied using atomic force microscopy. Raman spectroscopy gives some insights about the film microstructure. The film surface roughness is shown to decrease with the increase of deposition negative self-bias, while the presence of Ar ions enhances this effect. An analysis of the film surface and scaling behavior suggests that there is a transition of the mechanism of the film growth from a random deposition with surface diffusion process to a thermal spike based process that occurs upon the increase of the negative self-bias voltage and the argon bombardment.

  16. Remote plasma enhanced chemical vapor deposition of GaP with in situ generation of phosphine precursors

    NASA Technical Reports Server (NTRS)

    Choi, S. W.; Lucovsky, G.; Bachmann, K. J.

    1992-01-01

    Thin homoepitaxial films of gallium phosphide (GaP) have been grown by remote plasma enhanced chemical vapor deposition utilizing in situ-generated phosphine precursors. The GaP forming reaction is kinetically controlled with an activation energy of 0.65 eV. The increase of the growth rate with increasing radio frequency (RF) power between 20 and 100 W is due to the combined effects of increasingly complete excitation and the spatial extension of the glow discharge toward the substrate; however, the saturation of the growth rate at even higher RF power indicates the saturation of the generation rate of phosphine precursors at this condition. Slight interdiffusion of P into Si and Si into GaP is indicated from GaP/Si heterostructures grown under similar conditions as the GaP homojunctions.

  17. Remote plasma enhanced chemical vapor deposition of GaP with in situ generation of phosphine precursors

    NASA Technical Reports Server (NTRS)

    Choi, S. W.; Lucovsky, G.; Bachmann, Klaus J.

    1993-01-01

    Thin homoepitaxial films of gallium phosphide (GaP) were grown by remote plasma enhanced chemical vapor deposition utilizing in situ generated phosphine precursors. The GaP forming reaction is kinetically controlled with an activation energy of 0.65 eV. The increase of the growth rate with increasing radio frequency (rf) power between 20 and 100 W is due to the combined effects of increasingly complete excitation and the spatial extension of the glow discharge toward the substrate, however, the saturation of the growth rate at even higher rf power indicates the saturation of the generation rate of phosphine precursors at this condition. Slight interdiffusion of P into Si and Si into GaP is indicated from GaP/Si heterostructures grown under similar conditions as the GaP homojunctions.

  18. Highly efficient shrinkage of inverted-pyramid silicon nanopores by plasma-enhanced chemical vapor deposition technology.

    PubMed

    Wang, Yifan; Deng, Tao; Chen, Qi; Liang, Feng; Liu, Zewen

    2016-06-24

    Solid-state nanopore-based analysis systems are currently one of the most attractive and promising platforms in sensing fields. This work presents a highly efficient method to shrink inverted-pyramid silicon nanopores using plasma-enhanced chemical vapor deposition (PECVD) technology by the deposition of SiN x onto the surface of the nanopore. The contraction of the inverted-pyramid silicon nanopores when subjected to the PECVD process has been modeled and carefully analyzed, and the modeling data are in good agreement with the experimental results within a specific PECVD shrinkage period (∼0-600 s). Silicon nanopores within a 50-400 nm size range contract to sub-10 nm dimensions. Additionally, the inner structure of the nanopores after the PECVD process has been analyzed by focused ion beam cutting process. The results show an inner structure morphology change from inverted-pyramid to hourglass, which may enhance the spatial resolution of sensing devices.

  19. Experimental study of fractal clusters formation from nanoparticles synthesized by atmospheric pressure plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Mishin, Maxim V.; Protopopova, Vera S.; Alexandrov, Sergey E.

    2014-11-01

    This paper presents the experimental results from the fractal structures formation from nanoparticles of silicone dioxide deposited on the silicon substrate surface. Nanoparticles are synthesized by atmospheric pressure plasma-enhanced chemical vapor deposition with the use of capacitively coupled radio frequency (13.56 MHz) discharge sustained in helium atmosphere. Tetraethoxysilane is chosen as the test precursor. Correlation between the morphology of obtained deposits and the process parameters is found. The capability of nanoparticles movement along the deposit surface in local near-surface electric field is demonstrated. The empirical model that satisfactorily explained the mechanism of fractal clusters formation from nanoparticles on the substrate surface is developed. The model indicates that the dynamics of deposit morphology variations is determined by two competing processes: electrical charge transfer by nanoparticles to the deposit surface and electrical charge running off over the surface under conditions of changeable conductivity of the deposit surface.

  20. The growth characteristics of microcrystalline Si thin film deposited by atmospheric pressure plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Kwon, Jung-Dae

    2013-11-01

    Microcrystalline silicon thin film was grown by atmospheric pressure plasma-enhanced chemical vapor deposition (AP-PECVD) technique with a cylindrical rotary electrode supplied with 150 MHz very-high-frequency power. The crystalline volume fraction could be controlled by changing the flow rate ratio of silane and hydrogen gas during AP-PECVD. We could also control it by regulating the substrate scanning speed. At low substrate scanning speed, the silicon film had a low crystalline volume faction and layer-by-layer structure with alternating layers of amorphous and microcrystalline Si. On the other hand, at high substrate scanning speed, silicon crystals of sizes 25 nm grew homogeneously throughout the whole film.

  1. Method of plasma enhanced chemical vapor deposition of diamond using methanol-based solutions

    NASA Technical Reports Server (NTRS)

    Tzeng, Yonhua (Inventor)

    2009-01-01

    Briefly described, methods of forming diamond are described. A representative method, among others, includes: providing a substrate in a reaction chamber in a non-magnetic-field microwave plasma system; introducing, in the absence of a gas stream, a liquid precursor substantially free of water and containing methanol and at least one carbon and oxygen containing compound having a carbon to oxygen ratio greater than one, into an inlet of the reaction chamber; vaporizing the liquid precursor; and subjecting the vaporized precursor, in the absence of a carrier gas and in the absence in a reactive gas, to a plasma under conditions effective to disassociate the vaporized precursor and promote diamond growth on the substrate in a pressure range from about 70 to 130 Torr.

  2. Ti-doped hydrogenated diamond like carbon coating deposited by hybrid physical vapor deposition and plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Lee, Na Rae; Sle Jun, Yee; Moon, Kyoung Il; Sunyong Lee, Caroline

    2017-03-01

    Diamond-like carbon films containing titanium and hydrogen (Ti-doped DLC:H) were synthesized using a hybrid technique based on physical vapor deposition (PVD) and plasma enhanced chemical vapor deposition (PECVD). The film was deposited under a mixture of argon (Ar) and acetylene gas (C2H2). The amount of Ti in the Ti-doped DLC:H film was controlled by varying the DC power of the Ti sputtering target ranging from 0 to 240 W. The composition, microstructure, mechanical and chemical properties of Ti-doped DLC:H films with varying Ti concentrations, were investigated using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), nano indentation, a ball-on-disk tribometer, a four-point probe system and dynamic anodic testing. As a result, the optimum composition of Ti in Ti-doped DLC:H film using our hybrid method was found to be a Ti content of 18 at. %, having superior electrical conductivity and high corrosion resistance, suitable for bipolar plates. Its hardness value was measured to be 25.6 GPa with a low friction factor.

  3. Modifying friction between ultra-high molecular weight polyethylene (UHMWPE) yarns with plasma enhanced chemical vapour deposition (PCVD)

    NASA Astrophysics Data System (ADS)

    Chu, Yanyan; Chen, Xiaogang; Tian, Lipeng

    2017-06-01

    Ultra-high molecular weight polyethylene (UHMWPE) yarns are widely used in military applications for protection owing to its high modulus and high strength; however, the friction between UHMWPE yarns is too small, which is a weakness for ballistic applications. The purpose of current research is to increase the friction between UHMWPE yarns by plasma enhanced chemical vapour deposition (PCVD). The changes of morphology and chemical structure were characterised by SEM and FTIR individually. The coefficients of friction between yarns were tested by means of Capstan method. Results from tests showed that the yarn-yarn coefficient of static friction (CSF) has been improved from 0.12 to 0.23 and that of kinetic friction (CSF) increased from 0.11 to 0.19, as the samples exposure from 21 s to 4 min. The more inter-yarn friction can be attributed to more and more particles and more polar groups deposited on the surfaces of yarns, including carboxyl, carbonyl, hydroxyl and amine groups and compounds containing silicon. The tensile strength and modulus of yarns, which are essential to ballistic performance, keep stable and are not affected by the treatments, indicating that PCVD treatment is an effective way to improve the inter-yarn friction without mechanical property degradation.

  4. Determination of photocatalytic activity in amorphous and crystalline titanium oxide films prepared using plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Wu, Cheng-Yang; Chiang, Bo-Sheng; Chang, Springfield; Liu, Day-Shan

    2011-01-01

    Hydro-oxygenated amorphous titanium oxide (a-TiO x:OH) films were prepared by plasma-enhanced chemical vapor deposition (PECVD) using precursors of titanium tetraisopropoxide (TTIP) and oxygen. The influences of chemical states and crystal quality on the photocatalytic activity were systematically investigated in the as-deposited and post-annealed films. The degree of the photocatalytic activity was deeply correlated with the porosity related to the hydroxyl (OH) groups in the as-deposited amorphous film. The crystallized anatase structures was observed from the 200 °C-deposited a-TiO x:OH film after a post-annealing treatment at 400 °C. The photocatalytic activity related to the film with anatase structure was markedly superior to that of an amorphous film with porous structures. The larger the crystal size of the anatase structure, the higher the photocatalytic activity obtained. At elevated annealed temperatures, the inferior anatase structure due to the crystalline transformation led to a low photocatalytic activity. It was concluded that the photocatalytic activity of an amorphous TiO x film prepared using PECVD was determined by the porosity originating from the functional OH groups in the film, whereas the crystalline quality of anatase phase in the annealed poly-TiO x film was crucial to the photocatalytic activity.

  5. Deposition kinetics and characterization of stable ionomers from hexamethyldisiloxane and methacrylic acid by plasma enhanced chemical vapor deposition

    SciTech Connect

    Urstöger, Georg; Resel, Roland; Coclite, Anna Maria; Koller, Georg

    2016-04-07

    A novel ionomer of hexamethyldisiloxane and methacrylic acid was synthesized by plasma enhanced chemical vapor deposition (PECVD). The PECVD process, being solventless, allows mixing of monomers with very different solubilities, and for polymers formed at high deposition rates and with high structural stability (due to the high number of cross-links and covalent bonding to the substrate) to be obtained. A kinetic study over a large set of parameters was run with the aim of determining the optimal conditions for high stability and proton conductivity of the polymer layer. Copolymers with good stability over 6 months' time in air and water were obtained, as demonstrated by ellipsometry, X-Ray reflectivity, and FT-IR spectroscopy. Stable coatings showed also proton conductivity as high as 1.1 ± 0.1 mS cm{sup −1}. Chemical analysis showed that due to the high molecular weight of the chosen precursors, it was possible to keep the plasma energy-input-per-mass low. This allowed limited precursor fragmentation and the functional groups of both monomers to be retained during the plasma polymerization.

  6. Analysis of Oxidation State of Multilayered Catalyst Thin Films for Carbon Nanotube Growth Using Plasma-Enhanced Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Okita, Atsushi; Ozeki, Atsushi; Suda, Yoshiyuki; Nakamura, Junji; Oda, Akinori; Bhattacharyya, Krishnendu; Sugawara, Hirotake; Sakai, Yosuke

    2006-10-01

    We synthesized vertically aligned carbon nanotubes (CNTs) using multilayered catalyst thin films (Fe/Al2O3 and Al2O3/Fe/Al2O3) by RF (13.56 MHz) CH4/H2/Ar plasma-enhanced chemical vapor deposition. Pretreatment of the catalyst is crucial for CNT growth. In this paper, we analyzed the effect of catalyst reduction on CNT growth. Catalyst thin films on substrates were reduced by H2 plasma pretreatment at 550 °C to form nanometer-sized catalyst particles. The multilayered thin films were analyzed; the chemical composition and oxidation state by X-ray photoelectron spectroscopy (XPS) and the surface morphology by scanning electron microscopy (SEM). The Fe 2p peak of the XPS spectra showed that FexOy in the as-deposited catalyst was effectively reduced to Fe by a pretreatment of duration 4 min. Using this catalyst, we obtained CNTs with an average diameter of 10.7 nm and an average length of 5.3 μm. However, pretreatment longer than 4 min resulted in shorter CNTs and the Fe peak was shifted from Fe to Fe3O4. These transitions (Fe2O3→Fe3O4→Fe→Fe3O4) can be explained by the enthalpy of the oxides. This result indicates the presence of an optimum ratio between Fe and FexOy to maximize the CNT lengths.

  7. Plasma-enhanced chemical vapor deposition of low- loss as-grown germanosilicate layers for optical waveguides

    NASA Astrophysics Data System (ADS)

    Ay, Feridun; Agan, Sedat; Aydinli, Atilla

    2004-08-01

    We report on systematic growth and characterization of low-loss germanosilicate layers for use in optical waveguides. Plasma enhanced chemical vapor deposition (PECVD) technique was used to grow the films using silane, germane and nitrous oxide as precursor gases. Chemical composition was monitored by Fourier transform infrared (FTIR) spectroscopy. N-H bond concentration of the films decreased from 0.43x1022 cm-3 down to below 0.06x1022 cm-3, by a factor of seven as the GeH4 flow rate increased from 0 to 70 sccm. A simultaneous decrease of O-H related bonds was also observed by a factor of 10 in the same germane flow range. The measured TE rate increased from 5 to 50 sccm, respectively. In contrast, the propagation loss values for TE polarization at λ=632.8 nm were found to increase from are 0.20 +/- 0.02 to 6.46 +/- 0.04 dB/cm as the germane flow rate increased from 5 to 50 sccm, respectively. In contrast, the propagation loss values for TE polarization at λ=1550 nm were found to decrease from 0.32 +/- 0.03 down to 0.14 +/- 0.06 dB/cm for the same samples leading to the lowest values reported so far in the literature, eliminating the need for high temperature annealing as is usually done for these materials to be used in waveguide devices.

  8. Direct fabrication of 3D graphene on nanoporous anodic alumina by plasma-enhanced chemical vapor deposition

    PubMed Central

    Zhan, Hualin; Garrett, David J.; Apollo, Nicholas V.; Ganesan, Kumaravelu; Lau, Desmond; Prawer, Steven; Cervenka, Jiri

    2016-01-01

    High surface area electrode materials are of interest for a wide range of potential applications such as super-capacitors and electrochemical cells. This paper describes a fabrication method of three-dimensional (3D) graphene conformally coated on nanoporous insulating substrate with uniform nanopore size. 3D graphene films were formed by controlled graphitization of diamond-like amorphous carbon precursor films, deposited by plasma-enhanced chemical vapour deposition (PECVD). Plasma-assisted graphitization was found to produce better quality graphene than a simple thermal graphitization process. The resulting 3D graphene/amorphous carbon/alumina structure has a very high surface area, good electrical conductivity and exhibits excellent chemically stability, providing a good material platform for electrochemical applications. Consequently very large electrochemical capacitance values, as high as 2.1 mF for a sample of 10 mm3, were achieved. The electrochemical capacitance of the material exhibits a dependence on bias voltage, a phenomenon observed by other groups when studying graphene quantum capacitance. The plasma-assisted graphitization, which dominates the graphitization process, is analyzed and discussed in detail. PMID:26805546

  9. Direct fabrication of 3D graphene on nanoporous anodic alumina by plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Zhan, Hualin; Garrett, David J.; Apollo, Nicholas V.; Ganesan, Kumaravelu; Lau, Desmond; Prawer, Steven; Cervenka, Jiri

    2016-01-01

    High surface area electrode materials are of interest for a wide range of potential applications such as super-capacitors and electrochemical cells. This paper describes a fabrication method of three-dimensional (3D) graphene conformally coated on nanoporous insulating substrate with uniform nanopore size. 3D graphene films were formed by controlled graphitization of diamond-like amorphous carbon precursor films, deposited by plasma-enhanced chemical vapour deposition (PECVD). Plasma-assisted graphitization was found to produce better quality graphene than a simple thermal graphitization process. The resulting 3D graphene/amorphous carbon/alumina structure has a very high surface area, good electrical conductivity and exhibits excellent chemically stability, providing a good material platform for electrochemical applications. Consequently very large electrochemical capacitance values, as high as 2.1 mF for a sample of 10 mm3, were achieved. The electrochemical capacitance of the material exhibits a dependence on bias voltage, a phenomenon observed by other groups when studying graphene quantum capacitance. The plasma-assisted graphitization, which dominates the graphitization process, is analyzed and discussed in detail.

  10. Highly uniform wafer-scale synthesis of α-MoO3 by plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Kim, Hyeong-U.; Son, Juhyun; Kulkarni, Atul; Ahn, Chisung; Kim, Ki Seok; Shin, Dongjoo; Yeom, Geun Yong; Kim, Taesung

    2017-04-01

    Molybdenum oxide (MoO3) has gained immense attention because of its high electron mobility, wide band gap, and excellent optical and catalytic properties. However, the synthesis of uniform and large-area MoO3 is challenging. Here, we report the synthesis of wafer-scale α-MoO3 by plasma oxidation of Mo deposited on Si/SiO2. Mo was oxidized by O2 plasma in a plasma enhanced chemical vapor deposition (PECVD) system at 150 °C. It was found that the synthesized α-MoO3 had a highly uniform crystalline structure. For the as-synthesized α-MoO3 sensor, we observed a current change when the relative humidity was increased from 11% to 95%. The sensor was exposed to different humidity levels with fast recovery time of about 8 s. Hence this feasibility study shows that MoO3 synthesized at low temperature can be utilized for gas sensing applications by adopting flexible device technology.

  11. Influence of krypton atoms on the structure of hydrogenated amorphous carbon deposited by plasma enhanced chemical vapor deposition

    SciTech Connect

    Oliveira, M. H. Jr.; Viana, G. A.; Marques, F. C.; Lima, M. M. Jr. de; Cros, A.; Cantarero, A.

    2010-12-15

    Hydrogenated amorphous carbon (a-C:H) films were prepared by plasma enhanced chemical vapor deposition using methane (CH{sub 4}) plus krypton (Kr) mixed atmosphere. The depositions were performed as function of the bias voltage and krypton partial pressure. The goal of this work was to study the influence of krypton gas on the physical properties of a-C:H films deposited on the cathode electrode. Krypton concentration up to 1.6 at. %, determined by Rutherford Back-Scattering, was obtained at high Kr partial pressure and bias of -120 V. The structure of the films was analyzed by means of optical transmission spectroscopy, multi-wavelength Raman scattering and Fourier Transform Infrared spectroscopy. It was verified that the structure of the films remains unchanged up to a concentration of Kr of about 1.0 at. %. A slight graphitization of the films occurs for higher concentration. The observed variation in the film structure, optical band gap, stress, and hydrogen concentration were associated mainly with the subplantation process of hydrocarbons radicals, rather than the krypton ion energy.

  12. Large-area SiC membrane produced by plasma enhanced chemical vapor deposition at relatively high temperature

    SciTech Connect

    Liu, Yu; Xie, Changqing

    2015-09-15

    Advances in the growth of silicon carbide (SiC) thin films with outstanding thermal and mechanical properties have received considerable attention. However, the fabrication of large-area free-standing SiC membrane still remains a challenge. Here, the authors report a plasma enhanced chemical vapor deposition process at a relatively high temperature to improve the free-standing SiC membrane area. A systematic study on the microstructural, mechanical, and optical properties of hydrogenated polycrystalline silicon carbide (poly-SiC{sub x}:H) thin films deposited at 600 °C with different annealing temperatures has been performed. In the as-deposited state, SiC{sub x}:H thin films show a polycrystalline structure. The crystallinity degree can be further improved with the increase of the postdeposition annealing temperature. The resulting process produced free-standing 2-μm-thick SiC membranes up to 70 mm in diameter with root mean square roughness of 3.384 nm and optical transparency of about 70% at 632.8 nm wavelength. The large-area SiC membranes made out of poly-SiC{sub x}:H thin films deposited at a relatively high temperature can be beneficial for a wide variety of applications, such as x-ray diffractive optical elements, optical and mechanical filtering, lithography mask, lightweight space telescopes, etc.

  13. Highly uniform wafer-scale synthesis of α-MoO3 by plasma enhanced chemical vapor deposition.

    PubMed

    Kim, Hyeong-U; Son, Juhyun; Kulkarni, Atul; Ahn, Chisung; Kim, Ki Seok; Shin, Dongjoo; Yeom, Geun Yong; Kim, Taesung

    2017-04-28

    Molybdenum oxide (MoO3) has gained immense attention because of its high electron mobility, wide band gap, and excellent optical and catalytic properties. However, the synthesis of uniform and large-area MoO3 is challenging. Here, we report the synthesis of wafer-scale α-MoO3 by plasma oxidation of Mo deposited on Si/SiO2. Mo was oxidized by O2 plasma in a plasma enhanced chemical vapor deposition (PECVD) system at 150 °C. It was found that the synthesized α-MoO3 had a highly uniform crystalline structure. For the as-synthesized α-MoO3 sensor, we observed a current change when the relative humidity was increased from 11% to 95%. The sensor was exposed to different humidity levels with fast recovery time of about 8 s. Hence this feasibility study shows that MoO3 synthesized at low temperature can be utilized for gas sensing applications by adopting flexible device technology.

  14. A new perspective on structural and morphological properties of carbon nanotubes synthesized by Plasma Enhanced Chemical Vapor Deposition technique

    NASA Astrophysics Data System (ADS)

    Salar Elahi, A.; Agah, K. Mikaili; Ghoranneviss, M.

    CNTs were produced on a silicon wafer by Plasma Enhanced Chemical Vapor Deposition (PECVD) using acetylene as a carbon source, cobalt as a catalyst and ammonia as a reactive gas. The DC-sputtering system was used to prepare cobalt thin films on Si substrates. A series of experiments was carried out to investigate the effects of reaction temperature and deposition time on the synthesis of the nanotubes. The deposition time was selected as 15 and 25 min for all growth temperatures. Energy Dispersive X-ray (EDX) measurements were used to investigate the elemental composition of the Co nanocatalyst deposited on Si substrates. Atomic Force Microscopy (AFM) was used to characterize the surface topography of the Co nanocatalyst deposited on Si substrates. The as-grown CNTs were characterized under Field Emission Scanning Electron Microscopy (FESEM) to study the morphological properties of CNTs. Also, the grown CNTs have been investigated by High Resolution Transmission Electron Microscopy (HRTEM) and Raman spectroscopy. The results demonstrated that increasing the temperature leads to increasing the diameter of CNTs.

  15. Effects of Pretreatment on the Electronic Properties of Plasma Enhanced Chemical Vapor Deposition Hetero-Epitaxial Graphene Devices

    NASA Astrophysics Data System (ADS)

    Zhang, Lian-Chang; Shi, Zhi-Wen; Yang, Rong; Huang, Jian

    2014-09-01

    Quasi-monolayer graphene is successfully grown by the plasma enhanced chemical vapor deposition heteroepitaxial method we reported previously. To measure its electrical properties, the prepared graphene is fabricated into Hall ball shaped devices by the routine micro-fabrication method. However, impurity molecules adsorbed onto the graphene surface will impose considerable doping effects on the one-atom-thick film material. Our experiment demonstrates that pretreatment of the device by heat radiation baking and electrical annealing can dramatically influence the doping state of the graphene and consequently modify the electrical properties. While graphene in the as-fabricated device is highly p-doped, as confirmed by the position of the Dirac point at far more than +60 V, baking treatment at temperatures around 180°C can significantly lower the doping level and reduce the conductivity. The following electrical annealing is much more efficient to desorb the extrinsic molecules, as confirmed by the in situ measurement, and as a result, further modify the doping state and electrical properties of the graphene, causing a considerable drop of the conductivity and a shifting of Dirac point from beyond +60 V to 0 V.

  16. Deposition of zinc oxide photoelectrode using plasma enhanced chemical vapor deposition for dye-sensitized solar cells.

    PubMed

    Lee, Su Young; Kim, Sang Ho

    2014-12-01

    We investigated the characteristics of zinc oxide (ZnO) photoelectrodes grown by plasma enhanced chemical vapor deposition. ZnO has many advantages, such as high binding energy, breakdown strength, cohesion, hardness, and electron mobility. On the F-doped SnO2 (FTO) electrode, we deposited ZnO as a function of thickness, and we examined the thickness effect on the I-V, fill factor, open-circuit voltage, short-circuit current density, and especially the power conversion efficiency of the built in dye-sensitized solar cell. To study the thickness effect on the conduction and recombination of electrons in the ZnO electrode, we analyzed the alignment of grains, crystallinity, impedance, and cyclic I-V properties. The thickness of ZnO changed the electron diffusion length and recombination time. As a result, the maximum power conversion efficiency of 2.63% was obtained with a moderately thick (8.06 μm) ZnO.

  17. Osteoconductive Potential of Barrier NanoSiO2 PLGA Membranes Functionalized by Plasma Enhanced Chemical Vapour Deposition

    PubMed Central

    Terriza, Antonia; Vilches-Pérez, Jose I.; de la Orden, Emilio; Yubero, Francisco; Gonzalez-Caballero, Juan L.; González-Elipe, Agustin R.; Vilches, José; Salido, Mercedes

    2014-01-01

    The possibility of tailoring membrane surfaces with osteoconductive potential, in particular in biodegradable devices, to create modified biomaterials that stimulate osteoblast response should make them more suitable for clinical use, hopefully enhancing bone regeneration. Bioactive inorganic materials, such as silica, have been suggested to improve the bioactivity of synthetic biopolymers. An in vitro study on HOB human osteoblasts was performed to assess biocompatibility and bioactivity of SiO2 functionalized poly(lactide-co-glycolide) (PLGA) membranes, prior to clinical use. A 15 nm SiO2 layer was deposited by plasma enhanced chemical vapour deposition (PECVD), onto a resorbable PLGA membrane. Samples were characterized by X-ray photoelectron spectroscopy, atomic force microscopy, scanning electron microscopy, and infrared spectroscopy (FT-IR). HOB cells were seeded on sterilized test surfaces where cell morphology, spreading, actin cytoskeletal organization, and focal adhesion expression were assessed. As proved by the FT-IR analysis of samples, the deposition by PECVD of the SiO2 onto the PLGA membrane did not alter the composition and other characteristics of the organic membrane. A temporal and spatial reorganization of cytoskeleton and focal adhesions and morphological changes in response to SiO2 nanolayer were identified in our model. The novedous SiO2 deposition method is compatible with the standard sterilization protocols and reveals as a valuable tool to increase bioactivity of resorbable PLGA membranes. PMID:24883304

  18. Optimal design of antireflection coating and experimental verification by plasma enhanced chemical vapor deposition in small displays

    SciTech Connect

    Yang, S. M.; Hsieh, Y. C.; Jeng, C. A.

    2009-03-15

    Conventional antireflection coating by thin films of quarter-wavelength thickness is limited by material selections and these films' refractive indices. The optimal design by non-quarter-wavelength thickness is presented in this study. A multilayer thin-film model is developed by the admittance loci to show that the two-layer thin film of SiN{sub x}/SiO{sub y} at 124/87 nm and three layer of SiN{sub x}/SiN{sub y}/SiO{sub z} at 58/84/83 nm can achieve average transmittances of 94.4% and 94.9%, respectively, on polymer, glass, and silicon substrates. The optimal design is validated by plasma enhanced chemical vapor deposition of N{sub 2}O/SiH{sub 4} and NH{sub 3}/SiH{sub 4} to achieve the desired optical constants. Application of the antireflection coating to a 4 in. liquid crystal display demonstrates that the transmittance is over 94%, the mean luminance can be increased by 25%, and the total reflection angle increased from 41 deg. to 58 deg.

  19. Preparation of hydrophobic metal-organic frameworks via plasma enhanced chemical vapor deposition of perfluoroalkanes for the removal of ammonia.

    PubMed

    DeCoste, Jared B; Peterson, Gregory W

    2013-10-10

    Plasma enhanced chemical vapor deposition (PECVD) of perfluoroalkanes has long been studied for tuning the wetting properties of surfaces. For high surface area microporous materials, such as metal-organic frameworks (MOFs), unique challenges present themselves for PECVD treatments. Herein the protocol for development of a MOF that was previously unstable to humid conditions is presented. The protocol describes the synthesis of Cu-BTC (also known as HKUST-1), the treatment of Cu-BTC with PECVD of perfluoroalkanes, the aging of materials under humid conditions, and the subsequent ammonia microbreakthrough experiments on milligram quantities of microporous materials. Cu-BTC has an extremely high surface area (~1,800 m(2)/g) when compared to most materials or surfaces that have been previously treated by PECVD methods. Parameters such as chamber pressure and treatment time are extremely important to ensure the perfluoroalkane plasma penetrates to and reacts with the inner MOF surfaces. Furthermore, the protocol for ammonia microbreakthrough experiments set forth here can be utilized for a variety of test gases and microporous materials.

  20. Preparation of Hydrophobic Metal-Organic Frameworks via Plasma Enhanced Chemical Vapor Deposition of Perfluoroalkanes for the Removal of Ammonia

    PubMed Central

    DeCoste, Jared B.; Peterson, Gregory W.

    2013-01-01

    Plasma enhanced chemical vapor deposition (PECVD) of perfluoroalkanes has long been studied for tuning the wetting properties of surfaces. For high surface area microporous materials, such as metal-organic frameworks (MOFs), unique challenges present themselves for PECVD treatments. Herein the protocol for development of a MOF that was previously unstable to humid conditions is presented. The protocol describes the synthesis of Cu-BTC (also known as HKUST-1), the treatment of Cu-BTC with PECVD of perfluoroalkanes, the aging of materials under humid conditions, and the subsequent ammonia microbreakthrough experiments on milligram quantities of microporous materials. Cu-BTC has an extremely high surface area (~1,800 m2/g) when compared to most materials or surfaces that have been previously treated by PECVD methods. Parameters such as chamber pressure and treatment time are extremely important to ensure the perfluoroalkane plasma penetrates to and reacts with the inner MOF surfaces. Furthermore, the protocol for ammonia microbreakthrough experiments set forth here can be utilized for a variety of test gases and microporous materials. PMID:24145623

  1. Synthesis of large scale graphene oxide using plasma enhanced chemical vapor deposition method and its application in humidity sensing

    SciTech Connect

    Liu, Yang; Chen, Yuming

    2016-03-14

    Large scale graphene oxide (GO) is directly synthesized on copper (Cu) foil by plasma enhanced chemical vapor deposition method under 500 °C and even lower temperature. Compared to the modified Hummer's method, the obtained GO sheet in this article is large, and it is scalable according to the Cu foil size. The oxygen-contained groups in the GO are introduced through the residual gas of methane (99.9% purity). To prevent the Cu surface from the bombardment of the ions in the plasma, we use low intensity discharge. Our experiment reveals that growth temperature has important influence on the carbon to oxygen ratio (C/O ratio) in the GO; and it also affects the amount of π-π* bonds between carbon atoms. Preliminary experiments on a 6 mm × 12 mm GO based humidity sensor prove that the synthesized GO reacts well to the humidity change. Our GO synthesis method may provide another channel for obtaining large scale GO in gas sensing or other applications.

  2. Plasma enhanced chemical vapour deposition of silica onto Ti: Analysis of surface chemistry, morphology and functional hydroxyl groups

    PubMed Central

    Szili, Endre J.; Kumar, Sunil; Smart, Roger St. C.; Lowe, Rachel; Saiz, Eduardo; Voelcker, Nicolas H.

    2009-01-01

    Previously, we have developed and characterised a procedure for the deposition of thin silica films by a plasma enhanced chemical vapour deposition (PECVD) procedure using tetraethoxysilane (TEOS) as the main precursor. We have used the silica coatings for improving the corrosion resistance of metals and for enhancing the bioactivity of biomedical metallic implants. Recently, we have been fine-tuning the PECVD method for producing high quality and reproducible PECVD-silica (PECVD-Si) coatings on metals, primarily for biomaterial applications. In order to understand the interaction of the PECVD-Si coatings with biological species (such as proteins and cells), it is important to first analyse the properties of the silica films deposited using the optimised parameters. Therefore, this current investigation was carried out to analyse the characteristic features of PECVD-Si deposited on Ti substrates (PECVD-Si-Ti). We determined that the PECVD-Si coatings on Ti were conformal to the substrate surface, strongly adhered to the underlying substrate and were resistant to delamination. The PECVD-Si surface was composed of stoichiometric SiO2, showed a low carbon content (below 10 at.%) and was very hydrophilic (contact angle <10°). Finally, we also showed that the PECVD-Si coatings contain functional hydroxyl groups. PMID:19809536

  3. Plasma enhanced chemical vapour deposition of silica onto Ti: Analysis of surface chemistry, morphology and functional hydroxyl groups.

    PubMed

    Szili, Endre J; Kumar, Sunil; Smart, Roger St C; Lowe, Rachel; Saiz, Eduardo; Voelcker, Nicolas H

    2008-07-15

    Previously, we have developed and characterised a procedure for the deposition of thin silica films by a plasma enhanced chemical vapour deposition (PECVD) procedure using tetraethoxysilane (TEOS) as the main precursor. We have used the silica coatings for improving the corrosion resistance of metals and for enhancing the bioactivity of biomedical metallic implants. Recently, we have been fine-tuning the PECVD method for producing high quality and reproducible PECVD-silica (PECVD-Si) coatings on metals, primarily for biomaterial applications. In order to understand the interaction of the PECVD-Si coatings with biological species (such as proteins and cells), it is important to first analyse the properties of the silica films deposited using the optimised parameters. Therefore, this current investigation was carried out to analyse the characteristic features of PECVD-Si deposited on Ti substrates (PECVD-Si-Ti). We determined that the PECVD-Si coatings on Ti were conformal to the substrate surface, strongly adhered to the underlying substrate and were resistant to delamination. The PECVD-Si surface was composed of stoichiometric SiO(2), showed a low carbon content (below 10 at.%) and was very hydrophilic (contact angle <10°). Finally, we also showed that the PECVD-Si coatings contain functional hydroxyl groups.

  4. Film Characteristics of Low-Temperature Plasma-Enhanced Chemical Vapor Deposition Silicon Dioxide Using Tetraisocyanatesilane and Oxygen

    NASA Astrophysics Data System (ADS)

    Idris, Irman; Sugiura, Osamu

    1998-12-01

    Silicon dioxide films were deposited in a parallel-plate electrode RF plasma-enhanced chemical vapor deposition (PECVD) system using hydrogen-free tetraisocyanatesilane (TICS) and oxygen. The deposition parameters were varied systematically, and the films were characterized by measuring infrared spectra, density, etch rate, refractive index, and current-voltage (I V) and capacitance-voltage (C V) characteristics, as well as by examining their annealing behavior. At 300°C and a TICS partial pressure ratio of 20%, a water-free and hydroxyl-group-free SiO2 film was obtained. The film density, BHF etch rate, refractive index, resistivity, and dielectric constant were 2.3 g/cm3, 330 nm/min, 1.46, 7×1015 Ω·cm, and 3.6, respectively. The film quality degraded and, simultaneously, the film absorbed moisture from the atmosphere with decreasing deposition temperature; however, the quality can be improved by reducing TICS partial pressure. SiO2 films could be deposited even at 15°C, and had a resistivity of about 1013Ω·cm. Infrared measurements showed that SiO2 films deposited from TICS/O2 contained less absorbed water than those deposited from hydrogen-containing source materials at the same deposition temperature.

  5. Anatomy of μc-Si thin films by plasma enhanced chemical vapor deposition: An investigation by spectroscopic ellipsometry

    NASA Astrophysics Data System (ADS)

    Losurdo, M.; Rizzoli, R.; Summonte, C.; Cicala, G.; Capezzuto, P.; Bruno, G.

    2000-09-01

    A detailed analysis of the anatomy of microcrystalline (μc-Si) films deposited by plasma enhanced chemical vapor deposition from both SiF4-H2 and SiH4-H2 mixtures is performed by spectroscopic ellipsometry (SE). Specifically, the μc-Si film anatomy consists of an interface layer at the substrate/μc-Si bulk layer, a bulk μc-Si layer, and a surface porous layer. All these layers have their own microstructures, which need to be highlighted, since it is this overall anatomy which determines the optical properties of μc-Si films. The ability of SE to discriminate the complex microstructure of μc-Si thin films is emphasized also by the comparison with the x-ray diffraction data which cannot provide unambiguous information regarding the distribution of the crystalline and the amorphous phases along the μc-Si film thickness. Through the description of the μc-Si film anatomy, information on the effect of the growth precursors (SiF4 or SiH4) and of the substrate (c-Si or Corning glass) on the growth dynamics can be obtained. The key role of the F-atoms density and, therefore, of the etching-to-deposition competition on the growth mechanism and film microstructure is highlighted.

  6. Influence of krypton atoms on the structure of hydrogenated amorphous carbon deposited by plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Oliveira, M. H.; Viana, G. A.; de Lima, M. M.; Cros, A.; Cantarero, A.; Marques, F. C.

    2010-12-01

    Hydrogenated amorphous carbon (a-C:H) films were prepared by plasma enhanced chemical vapor deposition using methane (CH4) plus krypton (Kr) mixed atmosphere. The depositions were performed as function of the bias voltage and krypton partial pressure. The goal of this work was to study the influence of krypton gas on the physical properties of a-C:H films deposited on the cathode electrode. Krypton concentration up to 1.6 at. %, determined by Rutherford Back-Scattering, was obtained at high Kr partial pressure and bias of -120 V. The structure of the films was analyzed by means of optical transmission spectroscopy, multi-wavelength Raman scattering and Fourier Transform Infrared spectroscopy. It was verified that the structure of the films remains unchanged up to a concentration of Kr of about 1.0 at. %. A slight graphitization of the films occurs for higher concentration. The observed variation in the film structure, optical band gap, stress, and hydrogen concentration were associated mainly with the subplantation process of hydrocarbons radicals, rather than the krypton ion energy.

  7. Microwave-assisted Chemical Transformations

    EPA Science Inventory

    In recent years, there has been a considerable interest in developing sustainable chemistries utilizing green chemistry principles. Since the first published report in 1986 by Gedye and Giguere on microwave assisted synthesis in household microwave ovens, the use of microwaves as...

  8. Microwave-assisted Chemical Transformations

    EPA Science Inventory

    In recent years, there has been a considerable interest in developing sustainable chemistries utilizing green chemistry principles. Since the first published report in 1986 by Gedye and Giguere on microwave assisted synthesis in household microwave ovens, the use of microwaves as...

  9. Compositional study of silicon oxynitride thin films deposited using electron cyclotron resonance plasma-enhanced chemical vapor deposition technique

    SciTech Connect

    Baumann, H.; Sah, R.E.

    2005-05-01

    We have used backscattering spectrometry and {sup 15}N({sup 1}H,{alpha},{gamma}){sup 12}C nuclear reaction analysis techniques to study in detail the variation in the composition of silicon oxynitride films with deposition parameters. The films were deposited using 2.45 GHz electron cyclotron resonance plasma-enhanced chemical vapor deposition (PECVD) technique from mixtures of precursors argon, nitrous oxide, and silane at deposition temperature 90 deg. C. The deposition pressure and nitrous oxide-to-silane gas flow rates ratio have been found to have a pronounced influence on the composition of the films. When the deposition pressure was varied for a given nitrous oxide-to-silane gas flow ratio, the amount of silicon and nitrogen increased with the deposition pressure, while the amount of oxygen decreased. For a given deposition pressure, the amount of incorporated nitrogen and hydrogen decreased while that of oxygen increased with increasing nitrous oxide-to-silane gas flow rates ratio. For nitrous oxide-to-silane gas flow ratio of 5, we obtained films which contained neither chemically bonded nor nonbonded nitrogen atoms as revealed by the results of infrared spectroscopy, backscattering spectrometry, and nuclear reaction analysis. Our results demonstrate the nitrogen-free nearly stoichiometric silicon dioxide films can be prepared from a mixture of precursors argon, nitrous oxide, and silane at low substrate temperature using high-density PECVD technique. This avoids the use of a hazardous and an often forbidden pair of silane and oxygen gases in a plasma reactor.

  10. Characteristics of ultra low-k nanoporous and fluorinated silica based films prepared by plasma enhanced chemical vapor deposition

    SciTech Connect

    Abbasi-Firouzjah, M.; Shokri, B.

    2013-12-07

    Low dielectric constant (low-k) silica based films were deposited on p-type silicon and polycarbonate substrates by radio frequency (RF) plasma enhanced chemical vapor deposition method at low temperature. A mixture of tetraethoxysilane vapor, oxygen, and tetrafluoromethane (CF{sub 4}) was used for the deposition of the films in forms of two structures called as SiO{sub x}C{sub y} and SiO{sub x}C{sub y}F{sub z}. Properties of the films were controlled by amount of porosity and fluorine content in the film matrix. The influence of RF power and CF{sub 4} flow on the elemental composition, deposition rate, surface roughness, leakage current, refractive index, and dielectric constant of the films were characterized. Moreover, optical emission spectroscopy was applied to monitor the plasma process at the different parameters. Electrical characteristics of SiO{sub x}C{sub y} and SiO{sub x}C{sub y}F{sub z} films with metal-oxide-semiconductor structure were investigated using current-voltage analysis to measure the leakage current and breakdown field, as well as capacitance-voltage analysis to obtain the film's dielectric constant. The results revealed that SiO{sub x}C{sub y} films, which are deposited at lower RF power produce more leakage current, meanwhile the dielectric constant and refractive index of these films decreased mainly due to the more porosity in the film structure. By adding CF{sub 4} in the deposition process, fluorine, the most electronegative and the least polarized atom, doped into the silica film and led to decrease in the refractive index and the dielectric constant. In addition, no breakdown field was observed in the electrical characteristics of SiO{sub x}C{sub y}F{sub z} films and the leakage current of these films reduced by increment of the CF{sub 4} flow.

  11. Chemical vapor infiltration using microwave energy

    DOEpatents

    Devlin, David J.; Currier, Robert P.; Laia, Jr., Joseph R.; Barbero, Robert S.

    1993-01-01

    A method for producing reinforced ceramic composite articles by means of chemical vapor infiltration and deposition in which an inverted temperature gradient is utilized. Microwave energy is the source of heat for the process.

  12. Reduced chemical warfare agent sorption in polyurethane-painted surfaces via plasma-enhanced chemical vapor deposition of perfluoroalkanes.

    PubMed

    Gordon, Wesley O; Peterson, Gregory W; Durke, Erin M

    2015-04-01

    Perfluoralkalation via plasma chemical vapor deposition has been used to improve hydrophobicity of surfaces. We have investigated this technique to improve the resistance of commercial polyurethane coatings to chemicals, such as chemical warfare agents. The reported results indicate the surface treatment minimizes the spread of agent droplets and the sorption of agent into the coating. The improvement in resistance is likely due to reduction of the coating's surface free energy via fluorine incorporation, but may also have contributing effects from surface morphology changes. The data indicates that plasma-based surface modifications may have utility in improving chemical resistance of commercial coatings.

  13. Characteristic Study of Boron Doped Carbon Nanowalls Films Deposited by Microwave Plasma Enhanced Chemical Vapor Deposition.

    PubMed

    Lu, Chunyuan; Dong, Qi; Tulugan, Kelimu; Park, Yeong Min; More, Mahendra A; Kim, Jaeho; Kim, Tae Gyu

    2016-02-01

    In this research, catalyst-free vertically aligned boron doped carbon nanowalls films were fabricated on silicon (100) substrates by MPECVD using feeding gases CH4, H2 and B2H6 (diluted with H2 to 5% vol) as precursors. The substrates were pre-seeded with nanodiamond colloid. The fabricated CNWs films were characterized by Scanning Electron Microscopy (SEM) and Raman Spectroscopy. The data obtained from SEM confirms that the CNWs films have different density and wall thickness. From Raman spectrum, a G peak around 1588 cm(-1) and a D band peak at 1362 cm(-1) were observed, which indicates a successful fabrication of CNWs films. The EDX spectrum of boron doped CNWs film shows the existence of boron and carbon. Furthermore, field emission properties of boron doped carbon nanowalls films were measured and field enhancement factor was calculated using Fowler-Nordheim plot. The result indicates that boron doped CNWs films could be potential electron emitting materials.

  14. Patterning and Characterization of Carbon Nanotubes Grown in a Microwave Plasma Enhanced Chemical Vapor Deposition Chamber

    DTIC Science & Technology

    2009-03-01

    require lots of power to operate , suffer from burn-in and have a short life span. OLED displays are the newcomers to the market boasting low power...layer is created to ensure no shorting can happen between the CNTs and the gate. 2.2.4.4 Field Emission Triode Amplifier Utilizing Aligned Carbon Nan... operate in a vacuum and the use of its hollow structure as a composite for fuel cells. 2.4 Applications of Carbon Nanotubes 2.4.1 Mechanical Applications

  15. EFFICIENT CHEMICAL SYNTHESIS USING MICROWAVES

    EPA Science Inventory

    Synthetic organic transformations performed under non-traditional conditions are becoming popular primarily to circumvent the growing environmental concerns. A solvent-free approach that involves microwave (MW) exposure of neat reactants catalyzed by the surfaces of less-expensiv...

  16. EFFICIENT CHEMICAL SYNTHESIS USING MICROWAVES

    EPA Science Inventory

    Synthetic organic transformations performed under non-traditional conditions are becoming popular primarily to circumvent the growing environmental concerns. A solvent-free approach that involves microwave (MW) exposure of neat reactants catalyzed by the surfaces of less-expensiv...

  17. Modeling and experimental study on the growth of silicon germanium film by plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Zhao, Lai

    Hydrogenated microcrystalline silicon germanium µc-SiGe:H deposited by plasma enhanced chemical vapor deposition (PECVD) is of great interest to photovoltaic (PV) applications due to its low process temperature and good uniformity over large area. The nature of high optical absorption and low optical bandgap makes it promising as the bottom cell absorbing layer for tandem junction solar cells. However, the addition of germane (GeH4) gas changes deposited film properties and makes it rather complicated for the established silane (SiH4) based discharge process with hydrogen (H2) dilution. Despite existing experimental studies for SiH 4/GeH4/H2 3-gas mixture discharge and comprehensive numerical simulations for SiH4/H2 or SiH4/Ar plasma, to the author's best knowledge, a numerical model for both SiH 4 and GeH4 in a high pressure regime is yet to be developed. The plasma discharge, the film growth and their effects on film properties and the solar device performance need deep understanding. In this dissertation, the growth of the µc-SiGe:H film by radio frequency (RF) PECVD is studied through modeling simulation as well as experiments. The first numerical model for the glow discharge of SiH4/GeH 4/H2 3-gas mixture in a high pressure regime is developed based on one dimensional fluid model. Transports of electrons, molecules, radicals and ions in the RF excitation are described by diffusion equations that are coupled with the Poisson's equation. The deposition is integrated as the boundary conditions for discharge equations through the sticking coefficient model. Neutral ionizations, radical dissociations and chemical reactions in the gas phase and surface kinetics such as the diffusive motion, chemical reactions and the hydrogen etching are included with interaction rate constants. Solved with an explicit central-difference discretization scheme, the model simulates mathematical features that reflect the plasma physics such as the plasma sheath and gas species

  18. Plasma enhanced chemical vapor deposition of metalboride interfacial layers as diffusion barriers for nanostructured diamond growth on cobalt containing alloys CoCrMo and WC-Co

    NASA Astrophysics Data System (ADS)

    Johnston, Jamin M.

    This work is a compilation of theory, finite element modeling and experimental research related to the use of microwave plasma enhanced chemical vapor deposition (MPECVD) of diborane to create metal-boride surface coatings on CoCrMo and WC-Co, including the subsequent growth of nanostructured diamond (NSD). Motivation for this research stems from the need for wear resistant coatings on industrial materials, which require improved wear resistance and product lifetime to remain competitive and satisfy growing demand. Nanostructured diamond coatings are a promising solution to material wear but cannot be directly applied to cobalt containing substrates due to graphite nucleation. Unfortunately, conventional pre-treatment methods, such as acid etching, render the substrate too brittle. Thus, the use of boron in a MPECVD process is explored to create robust interlayers which inhibit carbon-cobalt interaction. Furthermore, modeling of the MPECVD process, through the COMSOL MultiphysicsRTM platform, is performed to provide insight into plasma-surface interactions using the simulation of a real-world apparatus. Experimental investigation of MPECVD boriding and NSD deposition was conducted at surface temperatures from 700 to 1100 °C. Several well-adhered metal-boride surface layers were formed: consisting of CoB, CrB, WCoB, CoB and/or W2CoB2. Many of the interlayers were shown to be effective diffusion barriers against elemental cobalt for improving nucleation and adhesion of NSD coatings; diamond on W2CoB2 was well adhered. However, predominantly WCoB and CoB phase interlayers suffered from diamond film delamination. Metal-boride and NSD surfaces were evaluated using glancing-angle x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), cross-sectional scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), micro-Raman spectroscopy, nanoindentation, scratch testing and epoxy pull testing. COMSOL MultiphysicsRTM was used to construct a

  19. GREENER CHEMICAL SYNTHESIS USING MICROWAVES

    EPA Science Inventory

    A solvent-free approach that involves microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of recyclable mineral supports such as alumina, silica, clay, or "doped" surfaces is presented which is applicable to a wide range of cleavage, condensation, cyc...

  20. GREENER CHEMICAL SYNTHESIS USING MICROWAVES

    EPA Science Inventory

    A solvent-free approach that involves microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of recyclable mineral supports such as alumina, silica, clay, or "doped" surfaces is presented which is applicable to a wide range of cleavage, condensation, cyc...

  1. Study of barrier properties and chemical resistance of recycled PET coated with amorphous carbon through a plasma enhanced chemical vapour deposition (PECVD) process.

    PubMed

    Cruz, S A; Zanin, M; Nerin, C; De Moraes, M A B

    2006-01-01

    Many studies have been carried out in order to make bottle-to-bottle recycling feasible. The problem is that residual contaminants in recycled plastic intended for food packaging could be a risk to public health. One option is to use a layer of virgin material, named functional barrier, which prevents the contaminants migration process. This paper shows the feasibility of using polyethylene terephthalate (PET) recycled for food packaging employing a functional barrier made from hydrogen amorphous carbon film deposited by Plasma Enhanced Chemical Vapour Deposition (PECVD) process. PET samples were deliberately contaminated with a series of surrogates using a FDA protocol. After that, PET samples were coated with approximately 600 and 1200 Angstrons thickness of amorphous carbon film. Then, the migration tests using as food simulants: water, 10% ethanol, 3% acetic acid, and isooctane were applied to the sample in order to check the chemical resistance of the new coated material. After the tests, the liquid extracts were analysed using a solid-phase microextraction device (SPME) coupled to GC-MS.

  2. Microwave-enhanced chemical processes

    DOEpatents

    Varma, Ravi

    1990-01-01

    A process for disposal of toxic wastes including chlorinated hydrocarbons, comprising, establishing a bed of non-metallic particulates having a high dielectric loss factor. Effecting intimate contact of the particulates and the toxic wastes at a temperature in excess of about 400.degree. C. in the presence of microwave radiation for a time sufficient to break the hydrocarbon chlorine bonds and provide detoxification values in excess of 80 and further detoxifying the bed followed by additional disposal of toxic wastes.

  3. Proposal of New Precursors for Plasma-Enhanced Chemical Vapor Deposition of SiOCH Low-k Films with Plasma Damage Resistance

    NASA Astrophysics Data System (ADS)

    Yoshi Ohashi,; Nobuo Tajima,; Yonghua Xu,; Takeshi Kada,; Shuji Nagano,; Hideharu Shimizu,; Satoshi Hasaka,

    2010-05-01

    We propose new precursors for bulk low-k films with plasma damage resistance. Our newly designed precursors contain long-chain hydrocarbon groups such as i-butyl and n-propyl groups. Using these precursors, we successfully produced films containing Si-CH2-Si groups by plasma-enhanced chemical vapor deposition (PECVD). The plasma damage resistance of these films under NH3 plasma treatment was studied. It was found that the increase in the k-value (Δ k) is smaller in films with more Si-CH2-Si groups.

  4. Proposal of New Precursors for Plasma-Enhanced Chemical Vapor Deposition of SiOCH Low-k Films with Plasma Damage Resistance

    NASA Astrophysics Data System (ADS)

    Ohashi, Yoshi; Tajima, Nobuo; Xu, Yonghua; Kada, Takeshi; Nagano, Shuji; Shimizu, Hideharu; Hasaka, Satoshi

    2010-05-01

    We propose new precursors for bulk low-k films with plasma damage resistance. Our newly designed precursors contain long-chain hydrocarbon groups such as i-butyl and n-propyl groups. Using these precursors, we successfully produced films containing Si-CH2-Si groups by plasma-enhanced chemical vapor deposition (PECVD). The plasma damage resistance of these films under NH3 plasma treatment was studied. It was found that the increase in the k-value (Δk) is smaller in films with more Si-CH2-Si groups.

  5. High-durability catalytic electrode composed of Pt nanoparticle-supported carbon nanowalls synthesized by radical-injection plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Imai, Shun; Kondo, Hiroki; Cho, Hyungjun; Kano, Hiroyuki; Ishikawa, Kenji; Sekine, Makoto; Hiramatsu, Mineo; Ito, Masafumi; Hori, Masaru

    2017-10-01

    For polymer electrolyte fuel cell applications, carbon nanowalls (CNWs) were synthesized by radical-injection plasma-enhanced chemical vapor deposition, and a high density of Pt nanoparticles (>1012 cm‑2) was supported on the CNWs using a supercritical fluid deposition system. The high potential cycle tests were applied and the electrochemical surface area of the Pt nanoparticle-supported CNWs did not change significantly, even after 20 000 high potential cycles. According to transmission electron microscopy observations, the mean diameter of Pt changed slightly after the cycle tests, while the crystallinity of the CNWs evaluated using Raman spectroscopy showed almost no change.

  6. Development of open air silicon deposition technology by silane-free atmospheric pressure plasma enhanced chemical transport under local ambient gas control

    NASA Astrophysics Data System (ADS)

    Naito, Teruki; Konno, Nobuaki; Yoshida, Yukihisa

    2016-07-01

    Open air silicon deposition was performed by combining silane-free atmospheric pressure plasma-enhanced chemical transport and a newly developed local ambient gas control technology. The effect of air contamination on silicon deposition was investigated using a vacuum chamber, and the allowable air contamination level was confirmed to be 3 ppm. The capability of the local ambient gas control head was investigated numerically and experimentally. A safe and clean process environment with air contamination less than 1 ppm was achieved. Combining these technologies, a microcrystalline silicon film was deposited in open air, the properties of which were comparable to those of silicon films deposited in a vacuum chamber.

  7. Hydrogen-Free Plasma-Enhanced Chemical Vapor Deposition of Silicon Dioxide Using Tetra-isocyanate-silane (Si(NCO) 4)

    NASA Astrophysics Data System (ADS)

    Idris, Irman; Sugiura, Osamu

    1995-06-01

    Deposition of silicon dioxide by plasma-enhanced chemical vapor deposition (PECVD) technique using tetra-isocyanate-silane (Si(NCO)4 : TICS) and oxygen for interlayer dielectric film application is proposed. Film properties strongly depend on the gas composition. The film which was deposited under an oxygen-rich condition was water-free after deposition. The film density, refractive index, resistivity, and dielectric constant were 2.3 g/cm3, 1.46, 5×1014 Ω·cm, and 3.6, respectively. The etch rate by buffered HF was 330 nm/min.

  8. Effects of pulse bias duty cycle on fullerenelike nanostructure and mechanical properties of hydrogenated carbon films prepared by plasma enhanced chemical vapor deposition method

    NASA Astrophysics Data System (ADS)

    Ji, Li; Li, Hongxuan; Zhao, Fei; Quan, Weilong; Chen, Jianmin; Zhou, Huidi

    2009-05-01

    Fullerenelike hydrogenated carbon films were produced by pulse bias-assisted rf inductively coupled plasma enhanced chemical vapor deposition (ICPECVD). The effects of pulse duty cycle on the microstructure and mechanical properties of the resultant films were investigated by means of high resolution transmission electron microscopy (HRTEM), Raman spectroscopy, nanoindentation, and stress measurement. The low pulse duty cycle was found the key in the formation of fullerenelike structure in hydrogenated carbon films, and thus increased the hardness, elasticity, and internal stress of the films. The role of pulse duty cycle in evolution of fullerenelike structure was also discussed in terms of ion bombardment, hydrogen removal, and "annealing" effects.

  9. Effects of the Physical Characteristics of Cerium Oxide on Plasma-Enhanced Tetraethylorthosiliate Removal Rate of Chemical Mechanical Polishing for Shallow Trench Isolation

    NASA Astrophysics Data System (ADS)

    Kim, Sang-Kyun; Paik, Ungyu; Oh, Seong-Geun; Park, Yong-Kook; Katoh, Takeo; Park, Jea-Gun

    2003-03-01

    Ceria powders were synthesized by two different methods, solid-state displacement reaction and wet chemical precipitation, and the influence of the physical characteristics of cerium oxide on the removal rate of plasma-enhanced tetraethylorthosilicate (PETEOS) and chemical vapor deposition (CVD) nitride films in chemical mechanical planarization (CMP) was investigated. The fundamental physicochemical property and electrokinetic behavior of ceria particles in aqueous suspending media were investigated to identify the correlation between the colloidal property of ceria and the CMP performance. The surface potentials of two different ceria particles are found to have different isoelectric point (pHiep) values and differences in physical properties of ceria particles such as porosity and density were found to be the key parameters in CMP of PETEOS films. Ceria powders synthesized by the solid-state displacement reaction method yielded a higher removal rate of PETEOS and higher selectivity than powders synthesized by the wet chemical precipitation method.

  10. Microwave-enhanced chemical processes

    DOEpatents

    Varma, R.

    1990-06-19

    A process is disclosed for the disposal of toxic wastes including chlorinated hydrocarbons, comprising, establishing a bed of non-metallic particulates having a high dielectric loss factor. Intimate contact of the particulates and the toxic wastes at a temperature in excess of about 400 C in the presence of microwave radiation for a time sufficient breaks the hydrocarbon chlorine bonds. Detoxification values in excess of 80 are provided and further detoxification of the bed is followed by additional disposal of toxic wastes. 1 figure.

  11. CHEMICAL SYNTHESES IN AQUEOUS MEDIA USING MICROWAVES

    EPA Science Inventory

    The development of efficient, selective and eco-friendly synthetic methods has remained a major focus of our research group. Microwave (MW) irradiation as alternative energy source in conjunction with water as reaction media has proven to be a successful 'greener' chemical appro...

  12. Microwave Technology--Applications in Chemical Synthesis

    EPA Science Inventory

    Microwave heating, being specific and instantaneous, is unique and has found a place for expeditious chemical syntheses. Specifically, the solvent-free reactions are convenient to perform and have advantages over the conventional heating protocols as summarized in the previous se...

  13. ‘GREENER’ CHEMICAL SYNTHESES USING MICROWAVES

    EPA Science Inventory

    The diverse nature of chemical entities requires various green strategic pathways in our quest towards attaining sustainability. A solvent-free approach that involves microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of less-expensive and recyclable ...

  14. ‘GREENER’ CHEMICAL SYNTHESES USING MICROWAVES

    EPA Science Inventory

    The diverse nature of chemical entities requires various green strategic pathways in our quest towards attaining sustainability. A solvent-free approach that involves microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of less-expensive and recyclable ...

  15. Microwave Technology--Applications in Chemical Synthesis

    EPA Science Inventory

    Microwave heating, being specific and instantaneous, is unique and has found a place for expeditious chemical syntheses. Specifically, the solvent-free reactions are convenient to perform and have advantages over the conventional heating protocols as summarized in the previous se...

  16. CHEMICAL SYNTHESES IN AQUEOUS MEDIA USING MICROWAVES

    EPA Science Inventory

    The development of efficient, selective and eco-friendly synthetic methods has remained a major focus of our research group. Microwave (MW) irradiation as alternative energy source in conjunction with water as reaction media has proven to be a successful 'greener' chemical appro...

  17. Physical/chemical properties of tin oxide thin film transistors prepared using plasma-enhanced atomic layer deposition

    SciTech Connect

    Lee, Byung Kook; Jung, Eunae; Kim, Seok Hwan; Moon, Dae Chul; Lee, Sun Sook; Park, Bo Keun; Hwang, Jin Ha; Chung, Taek-Mo; Kim, Chang Gyoun; An, Ki-Seok

    2012-10-15

    Thin film transistors (TFTs) with tin oxide films as the channel layer were fabricated by means of plasma enhanced atomic layer deposition (PE-ALD). The as-deposited tin oxide films show n-type conductivity and a nano-crystalline structure of SnO{sub 2}. Notwithstanding the relatively low deposition temperatures of 70, 100, and 130 °C, the bottom gate tin oxide TFTs show an on/off drain current ratio of 10{sup 6} while the device mobility values were increased from 2.31 cm{sup 2}/V s to 6.24 cm{sup 2}/V s upon increasing the deposition temperature of the tin oxide films.

  18. Resolving the nanostructure of plasma-enhanced chemical vapor deposited nanocrystalline SiO{sub x} layers for application in solar cells

    SciTech Connect

    Klingsporn, M.; Costina, I.; Kirner, S.; Stannowski, B.; Villringer, C.; Abou-Ras, D.; Lehmann, M.

    2016-06-14

    Nanocrystalline silicon suboxides (nc-SiO{sub x}) have attracted attention during the past years for the use in thin-film silicon solar cells. We investigated the relationships between the nanostructure as well as the chemical, electrical, and optical properties of phosphorous, doped, nc-SiO{sub 0.8}:H fabricated by plasma-enhanced chemical vapor deposition. The nanostructure was varied through the sample series by changing the deposition pressure from 533 to 1067 Pa. The samples were then characterized by X-ray photoelectron spectroscopy, spectroscopic ellipsometry, Raman spectroscopy, aberration-corrected high-resolution transmission electron microscopy, selected-area electron diffraction, and a specialized plasmon imaging method. We found that the material changed with increasing pressure from predominantly amorphous silicon monoxide to silicon dioxide containing nanocrystalline silicon. The nanostructure changed from amorphous silicon filaments to nanocrystalline silicon filaments, which were found to cause anisotropic electron transport.

  19. Plasma enhanced chemical vapor deposition of wear resistant gradual a-Si1-x:Cx:H coatings on nickel-titanium for biomedical applications

    NASA Astrophysics Data System (ADS)

    Niermann, Benedikt; Böke, Marc; Schauer, Janine-Christina; Winter, Jörg

    2010-03-01

    Plasma enhanced chemical vapor deposition has been used to deposit thin films with gradual transitions from silicon to carbon on Cu, Ni, stainless steel, and NiTi. Thus show low stress, elasticity, and wear resistance with excellent adhesion on all metals under investigation. Already at low Si concentrations of 10 at. % the intrinsic stress is considerably reduced compared to pure diamondlike carbon (DLC) films. The deposition process is controlled by optical emission spectroscopy. This technique has been applied to monitor the growth precursors and to correlate them with the film composition. The compositions of the films were determined by Rutherford backscattering spectroscopy and XPS measurements. Due to the elastic properties of the gradual transition and the excellent biocompatibility of DLC, the described film systems present a useful coating for biomedical applications.

  20. Amorphous silicon waveguides and light modulators for integrated photonics realized by low-temperature plasma-enhanced chemical-vapor deposition.

    PubMed

    Cocorullo, G; Corte, F G; Rendina, I; Minarini, C; Rubino, A; Terzini, E

    1996-12-15

    A new amorphous silicon waveguide is realized by use of amorphous silicon carbon as cladding material. The structure is characterized both experimentally and theoretically, and its application for optical interconnections in photonic integrated circuits on silicon motherboards is proposed. The fabrication process is based on low-temperature (220 degrees C) plasma-enhanced chemical-vapor deposition and is compatible with standard microelectronic processes. Propagation losses of 1.8 dB/cm have been measured at the fiber-optic wavelength of 1.3 microm. A strong thermo-optic coefficient has been measured in this material at this wavelength and exploited for the realization of a light-intensity modulator based on a Fabry-Perot interferometer that is tunable by temperature.

  1. Characterization of TiO x film prepared by plasma enhanced chemical vapor deposition using a multi-jet hollow cathode plasma source

    NASA Astrophysics Data System (ADS)

    Nakamura, Masatoshi; Korzec, Dariusz; Aoki, Toru; Engemann, Jurgen; Hatanaka, Yoshinori

    2001-05-01

    The high rate deposition of TiO x film at low temperature was achieved by plasma enhanced chemical vapor deposition (PECVD) using titanium tetraisopropoxide (TTIP) as a source material. The multi-jet hollow cathode plasma source was used to generate the high-density plasma, which was showered toward the substrate. The emission spectra suggest that oxygen radicals play an important role for dissociation of the source material and for yielding the precursors. The high deposition rate up to 50 nm/min was achieved by this process. The as-deposited films are completely amorphous. They consist of structures with complex bondings including both tetrahedral and octahedral components. Though they have such complex bondings, the hydrophilicity of the PECVD film is excellent comparing to that of the annealed crystalline anatase structure. It seems that the PECVD using the multi-jet plasma source is promising for fabrication of hydrophilic TiO x films in low-temperature process.

  2. Tensile test of a silicon microstructure fully coated with submicrometer-thick diamond like carbon film using plasma enhanced chemical vapor deposition method

    NASA Astrophysics Data System (ADS)

    Zhang, Wenlei; Uesugi, Akio; Hirai, Yoshikazu; Tsuchiya, Toshiyuki; Tabata, Osamu

    2017-06-01

    This paper reports the tensile properties of single-crystal silicon (SCS) microstructures fully coated with sub-micrometer thick diamond like carbon (DLC) film using plasma enhanced chemical vapor deposition (PECVD). To minimize the deformations or damages caused by non-uniform coating of DLC, which has high compression residual stress, released SCS specimens with the dimensions of 120 µm long, 4 µm wide, and 5 µm thick were coated from the top and bottom side simultaneously. The thickness of DLC coating is around 150 nm and three different bias voltages were used for deposition. The tensile strength improved from 13.4 to 53.5% with the increasing of negative bias voltage. In addition, the deviation in strength also reduced significantly compared to bare SCS sample.

  3. Al2O3 thin films by plasma-enhanced chemical vapour deposition using trimethyl-amine alane (TMAA) as the Al precursor

    NASA Astrophysics Data System (ADS)

    Chryssou, C. E.; Pitt, C. W.

    We report the low temperature (200-300 °C) deposition of uniform, amorphous Al2O3 thin films by plasma-enhanced chemical vapour deposition (PECVD) using trimethyl-amine alane (TMAA) as the Al precursor. The thin films were deposited on both Si and quartz silica (SiO2) substrates. Deposition rates were typically 60 Åmin-1 keeping the TMAA temperature constant at 45 °C. The deposited Al2O3 thin films were stoichiometric alumina with low carbon contamination (0.7-1.3 At%). The refractive index ranged from 1.54 to 1.62 depending on the deposition conditions. The deposition rate was studied as a function of both the RF power and the substrate temperature. The structure and the surface of the deposited Al2O3 thin films were studied using X-ray diffraction, atomic force microscopy (AFM) and scanning electron microscopy (SEM).

  4. Impact of the etching gas on vertically oriented single wall and few walled carbon nanotubes by plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Gohier, A.; Minea, T. M.; Djouadi, M. A.; Granier, A.

    2007-03-01

    Vertically oriented single wall nanotubes (SWNTs) and few walled nanotubes (FWNTs) have been grown by electronic cyclotron resonance plasma enhanced chemical vapor deposition (PECVD) on silica flat substrates. The impact of the plasma parameters on SWNT and FWNT growth has been investigated using two different etching gas mixtures, namely, C2H2/NH3 and C2H2/H2 with various ratios and applied bias voltages. Kinetic studies are also proposed in order to describe the FWNT growth mechanism by plasma techniques. A key role played by the reactive gas (NH3 and H2) is observed in the PECVD process, contrary to multiwalled nanotube growth. It is demonstrated that the balance between FWNT growth versus FWNT etching can be widely modulated by varying the gas mixture and bias voltage. It is shown that the use of hydrogen for hydrocarbon gas dilution restricts the destruction of SWNT and FWNT by the plasma species (ions and radicals).

  5. Methane as an effective hydrogen source for single-layer graphene synthesis on Cu foil by plasma enhanced chemical vapor deposition.

    PubMed

    Kim, Yong Seung; Lee, Jae Hong; Kim, Young Duck; Jerng, Sahng-Kyoon; Joo, Kisu; Kim, Eunho; Jung, Jongwan; Yoon, Euijoon; Park, Yun Daniel; Seo, Sunae; Chun, Seung-Hyun

    2013-02-07

    A single-layer graphene is synthesized on Cu foil in the absence of H(2) flow by plasma enhanced chemical vapor deposition (PECVD). In lieu of an explicit H(2) flow, hydrogen species are produced during the methane decomposition process into their active species (CH(x<4)), assisted with the plasma. Notably, the early stage of growth depends strongly on the plasma power. The resulting grain size (the nucleation density) has a maximum (minimum) at 50 W and saturates when the plasma power is higher than 120 W because hydrogen partial pressures are effectively tuned by a simple control of the plasma power. Raman spectroscopy and transport measurements show that decomposed methane alone can provide a sufficient amount of hydrogen species for high-quality graphene synthesis by PECVD.

  6. Device Quality SiO2 Deposited by Distributed Electron Cyclotron Resonance Plasma Enhanced Chemical Vapor Deposition without Substrate Heating

    NASA Astrophysics Data System (ADS)

    Jiang, Nan; Hugon, Marie-Christine; Agius, Bernard; Kretz, Thierry; Plais, François; Pribat, Didier; Carriere, Thierry; Puech, Michel

    1992-10-01

    The deposition of high electrical quality SiO2 films on Si wafers has been achieved without substrate heating, (T<˜ 100°C), using distributed electron cyclotron resonance (DECR) microwave plasmas. We have studied the effects of the reactant gas mixture composition (O2/SiH4) on the dielectric behavior of DECR SiO2. The electrical performances of both Si-SiO2 interfaces and SiO2 films in metal-oxide-semiconductor (MOS) structures were assessed by several characterization methods including critical field (Ec) evaluation, fixed charge densities (Qox) and interface traps densities (Dit) determinations. We report typical values of Ec around 6 MV\\cdotcm-1, and Qox and Dit densities around 2× 1010 cm-2 and 3× 1010 cm-2\\cdoteV-1 respectively. Thin film SOI-MOSFETs have also been fabricated to prove the DECR oxide quality.

  7. Effects of boron addition on a-Si(90)Ge(10):H films obtained by low frequency plasma enhanced chemical vapour deposition.

    PubMed

    Pérez, Arllene M; Renero, Francisco J; Zúñiga, Carlos; Torres, Alfonso; Santiago, César

    2005-06-29

    Optical, structural and electric properties of (a-(Si(90)Ge(10))(1-y)B(y):H) thin film alloys, deposited by low frequency plasma enhanced chemical vapour deposition, are presented. The chemical bonding structure has been studied by IR spectroscopy, while the composition was investigated by Raman spectroscopy. A discussion about boron doping effects, in the composition and bonding of samples, is presented. Transport of carriers has been studied by measurement of the conductivity dependence on temperature, which increases from 10(-3) to 10(1) Ω(-1) cm(-1) when the boron content varies from 0 to 50%. Similarly, the activation energy is between 0.62 and 0.19 eV when the doping increases from 0 to 83%. The optical properties have been determined from the film's optical transmission, using Swanepoel's method. It is shown that the optical gap varies from 1.3 to 0.99 eV.

  8. The Surface Interface Characteristics of Vertically Aligned Carbon Nanotube and Graphitic Carbon Fiber Arrays Grown by Thermal and Plasma Enhanced Chemical Vapor Deposition

    NASA Technical Reports Server (NTRS)

    Delzeit, Lance; Nguyen, Cattien; Li, Jun; Han, Jie; Meyyappan, M.

    2002-01-01

    The development of nano-arrays for sensors and devices requires the growth of arrays with the proper characteristics. One such application is the growth of vertically aligned carbon nanotubes (CNTs) and graphitic carbon fibers (GCFs) for the chemical attachment of probe molecules. The effectiveness of such an array is dependent not only upon the effectiveness of the probe and the interface between that probe and the array, but also the array and the underlaying substrate. If that array is a growth of vertically aligned CNTs or GCFs then the attachment of that array to the surface is of the utmost importance. This attachment provides the mechanical stability and durability of the array, as well as, the electrical properties of that array. If the detection is to be acquired through an electrical measurement, then the appropriate resistance between the array and the surface need to be fabricated into the device. I will present data on CNTs and GCFs grown from both thermal and plasma enhanced chemical vapor deposition. The focus will be on the characteristics of the metal film from which the CNTs and GCFs are grown and the changes that occur due to changes within the growth process.

  9. In situ spectroscopic ellipsometry growth studies on the Al-doped ZnO films deposited by remote plasma-enhanced metalorganic chemical vapor deposition

    SciTech Connect

    Volintiru, I.; Creatore, M.; Sanden, M. C. M. van de

    2008-02-01

    In situ spectroscopic ellipsometry (SE) was applied to study the pyramidlike and pillarlike growth of Al doped ZnO (AZO) films deposited by means of remote plasma-enhanced metalorganic chemical vapor deposition for transparent conductive oxide applications. Real time SE studies in the visible region allowed discerning between the two growth modes by addressing the time evolution of the bulk and surface roughness layer thickness. While the pillarlike mode is characterized by a constant growth rate, a slower rate in the initial stage (up to 150-200 nm film thickness), compared to the bulk, is observed for the growth of pyramidlike AZO films. The two modes differ also in terms of surface roughness development: a saturation behavior is observed for film thickness above 150-200 nm in the case of the pyramidlike films, while a slow linear increase with film thickness characterizes the pillarlike mode. By extending the SE analysis of the AZO films to the near infrared region, valuable information about the in grain properties could be extracted: excellent in grain mobility values, i.e., larger than 100 and 50 cm{sup 2}/V s, are determined for the pyramidlike and pillarlike AZO layers, respectively. The comparison between the outcome of the in situ real time SE studies and the ex situ electrical and chemical characterization highlights the limitations in the electron transport occurring in both types of films and allows one to address routes toward further improvement in AZO conductivity.

  10. Simultaneous synthesis of nanodiamonds and graphene via plasma enhanced chemical vapor deposition (MW PE-CVD) on copper.

    PubMed

    Gottlieb, Steven; Wöhrl, Nicolas; Schulz, Stephan; Buck, Volker

    2016-01-01

    The simultaneous growth of both nanodiamonds and graphene on copper samples is described for the first time. A PE-CVD process is used to synthesize graphene layers and nanodiamond clusters from a hydrogen/methane gas mixture as it is typically done successfully in thermal CVD processes for graphene synthesis. However, the standard thermal CVD process is not without problems since the deposition of graphene is affected by the evaporation of a notable amount of copper caused by the slow temperature increase typical for thermal CVD resulting in a long process time. In sharp contrast, the synthesis of graphene by PE-CVD can circumvent this problem by substantially shortening the process time at holding out the prospect of a lower substrate temperature. The reduced thermal load and the possibility to industrially scale-up the PE-CVD process makes it a very attractive alternative to the thermal CVD process with respect to the graphene production in the future. Nanodiamonds are synthesized in PE-CVD reactors for a long time because these processes offer a high degree of control over the film's nanostructure and simultaneously providing a significant high deposition rate. To model the co-deposition process, the three relevant macroscopic parameters (pressure, gas mixture and microwave power) are correlated with three relevant process properties (plasma ball size, substrate temperature and C2/Hα-ratio) and the influence on the quality of the deposited carbon allotropes is investigated. For the evaluation of the graphene as well as the nanodiamond quality, Raman spectroscopy used whereas the plasma properties are measured by optical methods. It is found that the diamond nucleation can be influenced by the C2/Hα-ratio in the plasma, while the graphene quality remains mostly unchanged by this parameter. Moreover it is derived from the experimental data that the direct plasma contact with the copper surface is beneficial for the nucleation of the diamond while the growth and

  11. Thermal expansion coefficient and thermomechanical properties of SiN(x) thin films prepared by plasma-enhanced chemical vapor deposition.

    PubMed

    Tien, Chuen-Lin; Lin, Tsai-Wei

    2012-10-20

    We present a new method based on fast Fourier transform (FFT) for evaluating the thermal expansion coefficient and thermomechanical properties of thin films. The silicon nitride thin films deposited on Corning glass and Si wafers were prepared by plasma-enhanced chemical vapor deposition in this study. The anisotropic residual stress and thermomechanical properties of silicon nitride thin films were studied. Residual stresses in thin films were measured by a modified Michelson interferometer associated with the FFT method under different heating temperatures. We found that the average residual-stress value increases when the temperature increases from room temperature to 100°C. Increased substrate temperature causes the residual stress in SiN(x) film deposited on Si wafers to be more compressive, but the residual stress in SiN(x) film on Corning glass becomes more tensile. The residual-stress versus substrate-temperature relation is a linear correlation after heating. A double substrate technique is used to determine the thermal expansion coefficients of the thin films. The experimental results show that the thermal expansion coefficient of the silicon nitride thin films is 3.27×10(-6)°C(-1). The biaxial modulus is 1125 GPa for SiN(x) film.

  12. Polyethylene Oxide Films Polymerized by Radio Frequency Plasma-Enhanced Chemical Vapour Phase Deposition and Its Adsorption Behaviour of Platelet-Rich Plasma

    NASA Astrophysics Data System (ADS)

    Hu, Wen-Juan; Xie, Fen-Yan; Chen, Qiang; Weng, Jing

    2008-10-01

    We present polyethylene oxide (PEO) functional films polymerized by rf plasma-enhanced vapour chemical deposition (rf-PECVD) on p-Si (100) surface with precursor ethylene glycol dimethyl ether (EGDME) and diluted Ar in pulsed plasma mode. The influences of discharge parameters on the film properties and compounds are investigated. The film structure is analysed by Fourier transform infrared (FTIR) spectroscopy. The water contact angle measurement and atomic force microscope (AFM) are employed to examine the surface polarity and to detect surface morphology, respectively. It is concluded that the smaller duty cycle in pulsed plasma mode contributes to the rich C-O-C (EO) group on the surfaces. As an application, the adsorption behaviour of platelet-rich plasma on plasma polymerization films performed in-vitro is explored. The shapes of attached cells are studied in detail by an optic invert microscope, which clarifies that high-density C-O-C groups on surfaces are responsible for non-fouling adsorption behaviour of the PEO films.

  13. Impact of Hydrocarbon Control in Ultraviolet-Assisted Restoration Process for Extremely Porous Plasma Enhanced Chemical Vapor Deposition SiOCH Films with k = 2.0

    NASA Astrophysics Data System (ADS)

    Kimura, Yosuke; Ishikawa, Dai; Nakano, Akinori; Kobayashi, Akiko; Matsushita, Kiyohiro; de Roest, David; Kobayashi, Nobuyoshi

    2012-05-01

    We investigated the effects of UV-assisted restoration on porous plasma-enhanced chemical vapor deposition (PECVD) SiOCH films with k = 2.0 and 2.3 having high porosities. By applying the UV-assisted restoration to O2-plasma-damaged films with k = 2.0 and 2.3, the recovery of the k-value was observed on the k = 2.3 film in proportion to -OH group reduction. However, the k = 2.0 film did not show recovery in spite of -OH group reduction. We found that hydrocarbon content in the k = 2.0 film was significantly increased by the UV-assisted restoration compared with the k = 2.3 film. According to these findings, we optimized the UV-assisted restoration to achieve improved controllability of the hydrocarbon uptake in the k = 2.0 film and confirmed the recovery of the k-value for O2-plasma-damaged film. Thus, adjusting the hydrocarbon uptake was crucial for restoring extremely porous SiOCH film.

  14. Structure, mechanical, and frictional properties of hydrogenated fullerene-like amorphous carbon film prepared by direct current plasma enhanced chemical vapor deposition

    SciTech Connect

    Wang, Yongfu; Gao, Kaixiong; Zhang, Junyan

    2016-07-28

    In this study, fullerene like carbon (FL-C) is introduced in hydrogenated amorphous carbon (a-C:H) film by employing a direct current plasma enhanced chemical vapor deposition. The film has a low friction and wear, such as 0.011 and 2.3 × 10{sup −9}mm{sup 3}/N m in the N{sub 2}, and 0.014 and 8.4 × 10{sup −8}mm{sup 3}/N m in the humid air, and high hardness and elasticity (25.8 GPa and 83.1%), to make further engineering applications in practice. It has several nanometers ordered domains consisting of less frequently cross-linked graphitic sheet stacks. We provide new evidences for understanding the reported Raman fit model involving four vibrational frequencies from five, six, and seven C-atom rings of FL-C structures, and discuss the structure evolution before or after friction according to the change in the 1200 cm{sup −1} Raman band intensity caused by five- and seven-carbon rings. Friction inevitably facilitates the transformation of carbon into FL-C nanostructures, namely, the ultra low friction comes from both such structures within the carbon film and the sliding induced at friction interface.

  15. Effect of plasma parameters on characteristics of silicon nitride film deposited by single and dual frequency plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Sahu, B. B.; Yin, Yongyi; Han, Jeon G.

    2016-03-01

    This work investigates the deposition of hydrogenated amorphous silicon nitride films using various low-temperature plasmas. Utilizing radio-frequency (RF, 13.56 MHz) and ultra-high frequency (UHF, 320 MHz) powers, different plasma enhanced chemical vapor deposition processes are conducted in the mixture of reactive N2/NH3/SiH4 gases. The processes are extensively characterized using different plasma diagnostic tools to study their plasma and radical generation capabilities. A typical transition of the electron energy distribution function from single- to bi-Maxwellian type is achieved by combining RF and ultra-high powers. Data analysis revealed that the RF/UHF dual frequency power enhances the plasma surface heating and produces hot electron population with relatively low electron temperature and high plasma density. Using various film analysis methods, we have investigated the role of plasma parameters on the compositional, structural, and optical properties of the deposited films to optimize the process conditions. The presented results show that the dual frequency power is effective for enhancing dissociation and ionization of neutrals, which in turn helps in enabling high deposition rate and improving film properties.

  16. Characteristics of silicon nitride deposited by VHF (162 MHz)-plasma enhanced chemical vapor deposition using a multi-tile push-pull plasma source

    NASA Astrophysics Data System (ADS)

    Kim, Ki Seok; Sirse, Nishant; Kim, Ki Hyun; Rogers Ellingboe, Albert; Kim, Kyong Nam; Yeom, Geun Young

    2016-10-01

    To prevent moisture and oxygen permeation into flexible organic electronic devices formed on substrates, the deposition of an inorganic diffusion barrier material such as SiN x is important for thin film encapsulation. In this study, by a very high frequency (162 MHz) plasma-enhanced chemical vapor deposition (VHF-PECVD) using a multi-tile push-pull plasma source, SiN x layers were deposited with a gas mixture of NH3/SiH4 with/without N2 and the characteristics of the plasma and the deposited SiN x film as the thin film barrier were investigated. Compared to a lower frequency (60 MHz) plasma, the VHF (162 MHz) multi-tile push-pull plasma showed a lower electron temperature, a higher vibrational temperature, and higher N2 dissociation for an N2 plasma. When a SiN x layer was deposited with a mixture of NH3/SiH4 with N2 at a low temperature of 100 °C, a stoichiometric amorphous Si3N4 layer with very low Si-H bonding could be deposited. The 300 nm thick SiN x film exhibited a low water vapor transmission rate of 1.18  ×  10-4 g (m2 · d)-1, in addition to an optical transmittance of higher than 90%.

  17. Structural evolution and photoluminescence of annealed Si-rich nitride with Si quantum dots prepared by plasma enhanced chemical vapor deposition

    SciTech Connect

    Zeng, Xiangbin Liao, Wugang; Wen, Guozhi; Wen, Xixing; Zheng, Wenjun

    2014-04-21

    Silicon-rich nitride films were deposited by plasma enhanced chemical vapor deposition. Silicon quantum dots (Si QDs) were formed by post-thermal annealing processing verified using the High-Resolution Transmission Electron Microscope. The 1100 °C thermal annealing leads to the nucleation of silicon atoms, the growth of Si QDs, and the rearrangement of Si 2p and N 1s elements. The structural evolution of silicon-rich nitride thin film with post annealing promotes the formation of Si QDs and Si{sub 3}N{sub 4} matrix. We also investigated the effect of the NH{sub 3}-to-SiH{sub 4} ratio R on the photoluminescence (PL) of SiN{sub x} with Si QDs. We found that the broad blue luminescence originates from both quantum confined effect and radiative defects. The intensity of the PL was changed by adjusting the NH{sub 3} flow rate. The increase of R could limit the transformation of Si QDs from amorphous to crystalline status, meanwhile lead to the alteration of distribution of defect states. These can help to understand the annealing-dependent characteristics, the PL mechanisms of silicon-rich nitride and to optimize the fabrication process of Si QDs embedded in nitride.

  18. Effect of plasma parameters on characteristics of silicon nitride film deposited by single and dual frequency plasma enhanced chemical vapor deposition

    SciTech Connect

    Sahu, B. B. E-mail: hanjg@skku.edu; Yin, Yongyi; Han, Jeon G. E-mail: hanjg@skku.edu

    2016-03-15

    This work investigates the deposition of hydrogenated amorphous silicon nitride films using various low-temperature plasmas. Utilizing radio-frequency (RF, 13.56 MHz) and ultra-high frequency (UHF, 320 MHz) powers, different plasma enhanced chemical vapor deposition processes are conducted in the mixture of reactive N{sub 2}/NH{sub 3}/SiH{sub 4} gases. The processes are extensively characterized using different plasma diagnostic tools to study their plasma and radical generation capabilities. A typical transition of the electron energy distribution function from single- to bi-Maxwellian type is achieved by combining RF and ultra-high powers. Data analysis revealed that the RF/UHF dual frequency power enhances the plasma surface heating and produces hot electron population with relatively low electron temperature and high plasma density. Using various film analysis methods, we have investigated the role of plasma parameters on the compositional, structural, and optical properties of the deposited films to optimize the process conditions. The presented results show that the dual frequency power is effective for enhancing dissociation and ionization of neutrals, which in turn helps in enabling high deposition rate and improving film properties.

  19. Structural and electrical properties and current-voltage characteristics of nitrogen-doped diamond-like carbon films on Si substrates by plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Tsuchiya, Masato; Murakami, Kazuki; Magara, Kohei; Nakamura, Kazuki; Ohashi, Haruka; Tokuda, Kengo; Takami, Takahiro; Ogasawara, Haruka; Enta, Yoshiharu; Suzuki, Yushi; Ando, Satoshi; Nakazawa, Hideki

    2016-06-01

    We have deposited nitrogen-doped diamond-like carbon (N-DLC) films by plasma-enhanced chemical vapor deposition using CH4, N2, and Ar, and investigated the effects of N doping on the structure and the electrical, mechanical, and optical properties of the N-DLC films. We fabricated undoped DLC/p-type Si and N-DLC/p-type Si heterojunctions and examined the current-voltage characteristics of the heterojunctions. When the N2 flow ratio was increased from 0 to 3.64%, the resistivity markedly decreased from the order of 105 Ω·cm to that of 10-2 Ω·cm and the internal stress also decreased. The resistivity gradually increased with increasing N2 flow ratio from 3.64 to 13.6%, and then it decreased at a N2 flow ratio of 13.6%. These behaviors can be explained in terms of the clustering of sp2 carbons and the formation of sp3C-N, sp2C=N, sp1C≡N, and C-H n bonds. The rectification ratio of the heterojunction using the N-DLC film prepared at 3.64% was 35.8 at ±0.5 V.

  20. Single liquid source plasma-enhanced metalorganic chemical vapor deposition of high-quality YBa2Cu3O(7-x) thin films

    NASA Technical Reports Server (NTRS)

    Zhang, Jiming; Gardiner, Robin A.; Kirlin, Peter S.; Boerstler, Robert W.; Steinbeck, John

    1992-01-01

    High quality YBa2Cu3O(7-x) films were grown in-situ on LaAlO3 (100) by a novel single liquid source plasma-enhanced metalorganic chemical vapor deposition process. The metalorganic complexes M(thd) (sub n), (thd = 2,2,6,6-tetramethyl-3,5-heptanedionate; M = Y, Ba, Cu) were dissolved in an organic solution and injected into a vaporizer immediately upstream of the reactor inlet. The single liquid source technique dramatically simplifies current CVD processing and can significantly improve the process reproducibility. X-ray diffraction measurements indicated that single phase, highly c-axis oriented YBa2Cu3O(7-x) was formed in-situ at substrate temperature 680 C. The as-deposited films exhibited a mirror-like surface, had transition temperature T(sub cO) approximately equal to 89 K, Delta T(sub c) less than 1 K, and Jc (77 K) = 10(exp 6) A/sq cm.

  1. High performance mechanisms of near-infrared photodetectors with microcrystalline SiGe films deposited using laser-assisted plasma enhanced chemical vapor deposition system.

    PubMed

    Lee, Ching-Ting; Tsai, Min-Yen

    2013-03-11

    The SiH(4) and GeH(4) reactant gases used for depositing microcrystalline SiGe films could be simultaneously decomposed when acted cooperatively on the plasma and the assistant CO(2) laser in the laser-assisted plasma enhanced chemical vapor deposition system. The carrier mobility of the 80 W laser-assisted SiGe films was significantly increased to 66.8 cm(2)/V-s compared with 2.22 cm(2)/V-s of the non-laser-assisted SiGe films. The performances of the resulting p-Si/i-SiGe/n-Si near-infrared photodetectors were improved due to the high quality and high carrier mobility of the laser-assisted SiGe films. The maximum photoresponsivity and the maximum quantum efficiency of the photodetectors with 80 W laser-assisted SiGe films were respectively improved to 0.47 A/W and 68.5% in comparison with 0.31 A/W and 46.5% of the photodetectors with non-laser-assisted SiGe films.

  2. Single liquid source plasma-enhanced metalorganic chemical vapor deposition of high-quality YBa2Cu3O(7-x) thin films

    NASA Technical Reports Server (NTRS)

    Zhang, Jiming; Gardiner, Robin A.; Kirlin, Peter S.; Boerstler, Robert W.; Steinbeck, John

    1992-01-01

    High quality YBa2Cu3O(7-x) films were grown in-situ on LaAlO3 (100) by a novel single liquid source plasma-enhanced metalorganic chemical vapor deposition process. The metalorganic complexes M(thd) (sub n), (thd = 2,2,6,6-tetramethyl-3,5-heptanedionate; M = Y, Ba, Cu) were dissolved in an organic solution and injected into a vaporizer immediately upstream of the reactor inlet. The single liquid source technique dramatically simplifies current CVD processing and can significantly improve the process reproducibility. X-ray diffraction measurements indicated that single phase, highly c-axis oriented YBa2Cu3O(7-x) was formed in-situ at substrate temperature 680 C. The as-deposited films exhibited a mirror-like surface, had transition temperature T(sub cO) approximately equal to 89 K, Delta T(sub c) less than 1 K, and Jc (77 K) = 10(exp 6) A/sq cm.

  3. Effect of ion bombardment on the synthesis of vertically aligned single-walled carbon nanotubes by plasma-enhanced chemical vapor deposition.

    PubMed

    Luo, Zhiqiang; Lim, Sanhua; You, Yumeng; Miao, Jianmin; Gong, Hao; Zhang, Jixuan; Wang, Shanzhong; Lin, Jianyi; Shen, Zexiang

    2008-06-25

    The synthesis of vertically aligned single-walled carbon nanotubes (VA-SWNTs) by plasma-enhanced chemical vapor deposition (PECVD) was achieved at 500-600 °C, using ethylene as the carbon source and 1 nm Fe film as the catalyst. For growth of high-quality VA-SWNTs in a plasma sheath, it is crucial to alleviate the undesirable ion bombardment etching effects by the optimization of plasma input power and gas pressure. The resistibility of synthesized VA-SWNTs against ion bombardment etching was found to be closely related to the growth temperature. At relatively low temperature (500 °C), the VA-SWNTs were very susceptible to ion bombardments, which could induce structural defects, and even resulted in a structural transition to few-walled nanotubes. For capacitively coupled radio frequency (rf) PECVD operating at moderate gas pressure (0.3-10 Torr), the ion bombardment etching effect is mainly dependent on the ion flux, which is related to the plasma input power and gas pressure.

  4. Effects of thermal annealing on the structural, mechanical, and tribological properties of hard fluorinated carbon films deposited by plasma enhanced chemical vapor deposition

    SciTech Connect

    Maia da Costa, M.E.H.; Baumvol, I.J.R.; Radke, C.; Jacobsohn, L.G.; Zamora, R.R.M.; Freire, F.L. Jr.

    2004-11-01

    Hard amorphous fluorinated carbon films (a-C:F) deposited by plasma enhanced chemical vapor deposition were annealed in vacuum for 30 min in the temperature range of 200-600 deg. C. The structural and compositional modifications were followed by several analytical techniques: Rutherford backscattering spectrometry (RBS), elastic recoil detection analysis (ERDA), x-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Nanoidentation measurements and lateral force microscopy experiments were carried out in order to provide the film hardness and the friction coefficient, respectively. The internal stress and contact angle were also measured. RBS, ERDA, and XPS results indicate that both fluorine and hydrogen losses occur for annealing temperatures higher than 300 deg. C. Raman spectroscopy shows a progressive graphitization upon annealing, while the surface became slightly more hydrophobic as revealed by the increase of the contact angle. Following the surface wettability reduction, a decrease of the friction coefficient was observed. These results highlight the influence of the capillary condensation on the nanoscale friction. The film hardness and the internal stress are constant up to 300 deg. C and decrease for higher annealing temperatures, showing a direct correlation with the atomic density of the films. Since the thickness variation is negligible, the mass loss upon thermal treatment results in amorphous structures with a lower degree of cross-linking, explaining the deterioration of the mechanical properties of the a-C:F films.

  5. Crystalline silicon surface passivation with amorphous SiC{sub x}:H films deposited by plasma-enhanced chemical-vapor deposition

    SciTech Connect

    Martin, I.; Vetter, M.; Garin, M.; Orpella, A.; Voz, C.; Puigdollers, J.; Alcubilla, R.

    2005-12-01

    Surface-passivating properties of hydrogenated amorphous silicon carbide films (a-SiC{sub x}:H) deposited by plasma-enhanced chemical-vapor deposition on both p- and n-type crystalline silicon (c-Si) have been extensively studied by our research group in previous publications. We characterized surface recombination by measuring the dependence of the effective lifetime ({tau}{sub eff}) on excess carrier density ({delta}n) through quasi-steady-state photoconductance technique. Additionally, we fitted the measured {tau}{sub eff}({delta}n) curves applying an insulator/semiconductor model which allows us to determine the surface recombination parameters. In this paper, this model is analyzed in detail focusing on the accuracy in the determination of the fitting parameters and revealing uncertainties not detected up to now. Taking advantage of this analysis, the dependence of surface passivation on film deposition conditions is revised including intrinsic a-SiC{sub x}:H films on both p- and n-type c-Si and phosphorus-doped a-SiC{sub x}:H films on p-type c-Si. As a consequence, a broad view of this passivation scheme is obtained.

  6. Structure, mechanical, and frictional properties of hydrogenated fullerene-like amorphous carbon film prepared by direct current plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Wang, Yongfu; Gao, Kaixiong; Zhang, Junyan

    2016-07-01

    In this study, fullerene like carbon (FL-C) is introduced in hydrogenated amorphous carbon (a-C:H) film by employing a direct current plasma enhanced chemical vapor deposition. The film has a low friction and wear, such as 0.011 and 2.3 × 10-9mm3/N m in the N2, and 0.014 and 8.4 × 10-8mm3/N m in the humid air, and high hardness and elasticity (25.8 GPa and 83.1%), to make further engineering applications in practice. It has several nanometers ordered domains consisting of less frequently cross-linked graphitic sheet stacks. We provide new evidences for understanding the reported Raman fit model involving four vibrational frequencies from five, six, and seven C-atom rings of FL-C structures, and discuss the structure evolution before or after friction according to the change in the 1200 cm-1 Raman band intensity caused by five- and seven-carbon rings. Friction inevitably facilitates the transformation of carbon into FL-C nanostructures, namely, the ultra low friction comes from both such structures within the carbon film and the sliding induced at friction interface.

  7. Tribological properties and thermal stability of hydrogenated, silicon/nitrogen-coincorporated diamond-like carbon films prepared by plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Nakazawa, Hideki; Okuno, Saori; Magara, Kohei; Nakamura, Kazuki; Miura, Soushi; Enta, Yoshiharu

    2016-12-01

    We have deposited hydrogenated, silicon/nitrogen-incorporated diamond-like carbon (Si-N-DLC) films by plasma-enhanced chemical vapor deposition using hexamethyldisilazane [((CH3)3Si)2NH; HMDS] as the Si and N source, and compared the tribological performance and thermal stability of the Si-N-DLC films with those of hydrogenated, Si-incorporated DLC (Si-DLC) films prepared using dimethylsilane [SiH2(CH3)2] as the Si source. The deposited films were annealed at 723-873 K in air atmosphere. The friction coefficients of hydrogenated DLC films after annealing significantly increased at the initial stages of friction tests. On the other hand, the friction coefficients of the Si-N-DLC films deposited at an HMDS flow ratio [HMDS/(HMDS+CH4)] of 2.27% remained low after the annealing even at 873 K. We found that the wear rate of the Si-N-DLC film deposited at 2.27% and -1000 V remained almost unchanged after the annealing at 873 K, whereas that of the Si-DLC film with a similar Si fraction deposited at -1000 V significantly increased after the annealing at 773 K.

  8. Si nanowires grown by Al-catalyzed plasma-enhanced chemical vapor deposition: synthesis conditions, electrical properties and application to lithium battery anodes

    NASA Astrophysics Data System (ADS)

    Toan, Le Duc; Moyen, Eric; Zamfir, Mihai Robert; Joe, Jemee; Kim, Young Woo; Pribat, Didier

    2016-01-01

    Silicon nanowires have been synhesized using Al as a catalyst. Silane (SiH4) diluted in H2 carrier gas was employed as Si precursor in a plasma enhanced chemical vapor deposition system operated at various temperatures (450 °C and 550 °C). Those growth temperatures, which are lower than the eutectic temperature in the Al-Si system (577 °C) suggests a vapor-solid-solid growth mechanism. Four point resistance measurements and back-gated current-voltage measurements indicated that silicon nanowires were heavily doped (p type), with a doping concentration of a few 1019 cm-3. We have measured hole mobility values of ˜16 cm2 V-1 s-1 at 450 °C and ˜30 cm2 V-1 s-1 at 550 °C. Transmission electron microscope analyses showed that the silicon nanowires were highly twinned even when they grow epitaxially on (111) Si substrates. We have also evaluated the use of those highly doped Si nanowires for lithium-ion battery anodes. We have observed a good cycling behavior during the first 65 charge-discharge cycles, followed by a slow capacity decay. After 150 cycles at a charge-discharge rate of 0.1 C, the electrode capacity was still 1400 mAh g-1. The ageing mechanism seems to be related to the delamination of the SiNWs from the stainless steel substrate on which they were grown.

  9. Effects of precursor concentration on the optical and electrical properties of SnXSY thin films prepared by plasma-enhanced chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Sanchez-Juarez, A.; Ortíz, A.

    2002-09-01

    We have carried out the electrical and optical characterization of thin films of compounds based on Sn-S bonds (SnS2, Sn2S3), prepared by plasma-enhanced chemical vapour deposition (PECVD), as a function of the relative concentration of the precursor vapours, SnCl4 and H2S, keeping all other deposition parameters constant. In all studied cases, the deposited films were formed by polycrystalline materials. The optical bandgap values of deposited materials were calculated from optical transmittance and reflectance measurements. The SnS2 compound produced under certain deposition conditions has a forbidden bandgap around 2.2 eV. This compound shows n-type electrical conductivity, whose dark value at room temperature is 2 × 10-2 (Ω cm)-1. Also, it shows the typical semiconductor dependence of its electrical conductivity on the temperature with an activation energy of about 0.15 eV. However, thin films of a mixture of SnS2 and Sn2S3 compounds were deposited with higher values of the relative concentration of source vapours than those used to obtain the SnS2 compound. The optical bandgap shows a decreasing trend as the relative concentration increases. A similar trend is observed for dark electrical conductivity. These results create the opportunity to use SnX SY compounds in thin films for building heterojunction solar cells prepared completely by PECVD.

  10. Effect of oxygen plasma on field emission characteristics of single-wall carbon nanotubes grown by plasma enhanced chemical vapour deposition system

    SciTech Connect

    Kumar, Avshish; Parveen, Shama; Husain, Samina; Ali, Javid; Zulfequar, Mohammad; Harsh; Husain, Mushahid

    2014-02-28

    Field emission properties of single wall carbon nanotubes (SWCNTs) grown on iron catalyst film by plasma enhanced chemical vapour deposition system were studied in diode configuration. The results were analysed in the framework of Fowler-Nordheim theory. The grown SWCNTs were found to be excellent field emitters, having emission current density higher than 20 mA/cm{sup 2} at a turn-on field of 1.3 V/μm. The as grown SWCNTs were further treated with Oxygen (O{sub 2}) plasma for 5 min and again field emission characteristics were measured. The O{sub 2} plasma treated SWCNTs have shown dramatic improvement in their field emission properties with emission current density of 111 mA/cm{sup 2} at a much lower turn on field of 0.8 V/μm. The as grown as well as plasma treated SWCNTs were also characterized by various techniques, such as scanning electron microscopy, high resolution transmission electron microscopy, Raman spectroscopy, and Fourier transform infrared spectroscopy before and after O{sub 2} plasma treatment and the findings are being reported in this paper.

  11. Evolution of the electrical and structural properties during the growth of Al doped ZnO films by remote plasma-enhanced metalorganic chemical vapor deposition

    SciTech Connect

    Volintiru, I.; Creatore, M.; Kniknie, B. J.; Spee, C. I. M. A.; Sanden, M. C. M. van de

    2007-08-15

    Al-doped zinc oxide (AZO) films were deposited by means of remote plasma-enhanced metalorganic chemical vapor deposition from oxygen/diethylzinc/trimethylaluminum mixtures. The electrical, structural (crystallinity and morphology), and chemical properties of the deposited films were investigated using Hall, four point probe, x-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), electron recoil detection (ERD), Rutherford backscattering (RBS), and time of flight secondary ion mass spectrometry (TOF-SIMS), respectively. We found that the working pressure plays an important role in controlling the sheet resistance R{sub s} and roughness development during film growth. At 1.5 mbar the AZO films are highly conductive (R{sub s}<6 {omega}/{open_square} for a film thickness above 1200 nm) and very rough (>4% of the film thickness), however, they are characterized by a large sheet resistance gradient with increasing film thickness. By decreasing the pressure from 1.5 to 0.38 mbar, the gradient is significantly reduced and the films become smoother, but the sheet resistance increases (R{sub s}{approx_equal}100 {omega}/{open_square} for a film thickness of 1000 nm). The sheet resistance gradient and the surface roughness development correlate with the grain size evolution, as determined from the AFM and SEM analyses, indicating the transition from pyramid-like at 1.5 mbar to pillar-like growth mode at 0.38 mbar. The change in plasma chemistry/growth precursors caused by the variation in pressure leads to different concentration and activation efficiency of Al dopant in the zinc oxide films. On the basis of the experimental evidence, a valid route for further improving the conductivity of the AZO film is found, i.e., increasing the grain size at the initial stage of film growth.

  12. Atmospheric-pressure plasma-enhanced chemical vapor deposition of a-SiCN:H films: Role of precursors on the film growth and properties

    SciTech Connect

    Guruvenket, Srinivasan; Andrie, Steven; Simon, Mark; Johnson, Kyle W.; Sailer, Robert A.

    2012-09-14

    Atmospheric pressure plasma enhanced chemical vapor deposition (AP-PECVD) using Surfx AtomflowTM 250D APPJ was utilized to synthesize amorphous silicon carbonitride coatings using tetramethyldisilizane (TMDZ) and hexamethyldisilizane (HMDZ) as the single source precursors. The effect of precursor chemistry and the substrate temperature (Ts) on the properties of a-SiCN:H films were evaluated, while nitrogen was used as the reactive gas. Surface morphology of the films was evaluated using atomic force microscopy (AFM); chemical properties were determined using Fourier transform infrared spectroscopy (FTIR); thickness and optical properties were determined using spectroscopic ellipsometry and mechanical properties were determined using nano-indentation. In general films deposited at substrate temperature (Ts) <200 °C contained organic moieties, while the films deposited at Ts >200 oC depicted strong Si-N and Si-CN absorption. Refractive indices (n) of the thin films showed values between 1.5 -2.0 depending on the deposition parameters. Mechanical properties of the films determined using nano-indentation revealed that these films have hardness between 0.5 GPa to 15 GPa depending on the Ts. AFM evaluation of the films showed high roughness (Ra) values of 2-3 nm for the films grown at low Ts (< 250 °C), while the films grown at Ts ≥ 300 °C exhibited atomically smooth surface with Ra of ~ 0.5 nm. Furthermore, based on the gas phase (plasma) chemistry, precursor chemistry and the other experimental observations, a possible growth model that prevails in the AP-PECVD of a-SiCN:H thin films is proposed.

  13. Hydrogenation of defects in edge-defined film-fed grown aluminum-enhanced plasma enhanced chemical vapor deposited silicon nitride multicrystalline silicon

    NASA Astrophysics Data System (ADS)

    Jeong, Ji-Weon; Rosenblum, Mark D.; Kalejs, Juris P.; Rohatgi, Ajeet

    2000-05-01

    Gettering of impurities and hydrogen passivation of defects in edge-defined film-fed grown (EFG) multicrystalline silicon were studied by low-cost manufacturable technologies such as emitter diffusion by a spin-on phosphorus dopant source, back surface field formation by screen-printed aluminum, and a post-deposition anneal of plasma enhanced chemical vapor deposited (PECVD) silicon nitride antireflection coating. These processes were carried out in a high-throughput lamp-heated conveyor belt furnace. PECVD silicon nitride-induced hydrogenation of defects in EFG silicon was studied in conjunction with screen-printed aluminum back surface field formation to investigate the synergistic effect of aluminum gettering and silicon nitride hydrogenation of bulk defects. It was found that post-deposition anneal of PECVD silicon nitride at temperatures ranging from 450 to 850 °C, without the coformation of aluminum back surface field on the back, does not provide appreciable passivation or hydrogenation of bulk defects in EFG material. However, simultaneous anneal of PECVD silicon nitride and formation of aluminum back surface field at 850 °C significantly enhanced the hydrogenation ability of the PECVD silicon nitride film. PECVD silicon nitride deposition and a subsequent anneal, after the aluminum back surface field formation, was found to be less effective in passivating bulk defects. It is proposed that aluminum-enhanced hydrogenation from a PECVD silicon nitride film is the result of vacancy generation at the aluminum-silicon interface due to the alloying process. The affinity of hydrogen to react with vacancies provides a chemical potential gradient that increases the flux of atomic hydrogen from the silicon nitride film into the bulk silicon. In addition, vacancies can dissociate hydrogen molecules, increasing the atomic hydrogen content of the bulk silicon. This enhances defect passivation and improves the minority carrier lifetime.

  14. Atmospheric-pressure plasma-enhanced chemical vapor deposition of a-SiCN:H films: Role of precursors on the film growth and properties

    DOE PAGES

    Guruvenket, Srinivasan; Andrie, Steven; Simon, Mark; ...

    2012-09-14

    Atmospheric pressure plasma enhanced chemical vapor deposition (AP-PECVD) using Surfx AtomflowTM 250D APPJ was utilized to synthesize amorphous silicon carbonitride coatings using tetramethyldisilizane (TMDZ) and hexamethyldisilizane (HMDZ) as the single source precursors. The effect of precursor chemistry and the substrate temperature (Ts) on the properties of a-SiCN:H films were evaluated, while nitrogen was used as the reactive gas. Surface morphology of the films was evaluated using atomic force microscopy (AFM); chemical properties were determined using Fourier transform infrared spectroscopy (FTIR); thickness and optical properties were determined using spectroscopic ellipsometry and mechanical properties were determined using nano-indentation. In general films depositedmore » at substrate temperature (Ts) <200 °C contained organic moieties, while the films deposited at Ts >200 oC depicted strong Si-N and Si-CN absorption. Refractive indices (n) of the thin films showed values between 1.5 -2.0 depending on the deposition parameters. Mechanical properties of the films determined using nano-indentation revealed that these films have hardness between 0.5 GPa to 15 GPa depending on the Ts. AFM evaluation of the films showed high roughness (Ra) values of 2-3 nm for the films grown at low Ts (< 250 °C), while the films grown at Ts ≥ 300 °C exhibited atomically smooth surface with Ra of ~ 0.5 nm. Furthermore, based on the gas phase (plasma) chemistry, precursor chemistry and the other experimental observations, a possible growth model that prevails in the AP-PECVD of a-SiCN:H thin films is proposed.« less

  15. High-temperature degradation in plasma-enhanced chemical vapor deposition Al{sub 2}O{sub 3} surface passivation layers on crystalline silicon

    SciTech Connect

    Kühnhold, Saskia; Saint-Cast, Pierre; Kafle, Bishal; Hofmann, Marc; Colonna, Francesco; Zacharias, Margit

    2014-08-07

    In this publication, the activation and degradation of the passivation quality of plasma-enhanced chemical vapor deposited aluminum oxide (Al{sub 2}O{sub 3}) layers with different thicknesses (10 nm, 20 nm, and 110 nm) on crystalline silicon (c-Si) during long and high temperature treatments are investigated. As indicated by Fourier Transform Infrared Spectroscopy, the concentration of tetrahedral and octahedral sites within the Al{sub 2}O{sub 3} layer changes during temperature treatments and correlates with the amount of negative fixed charges at the Si/Al{sub 2}O{sub 3} interface, which was detected by Corona Oxide Characterization of Semiconductors. Furthermore, during a temperature treatment at 820 °C for 30 min, the initial amorphous Al{sub 2}O{sub 3} layer crystallize into the γ-Al{sub 2}O{sub 3} structure and was enhanced by additional oxygen as was proven by x-ray diffraction measurements and underlined by Density Functional Theory simulations. The crystallization correlates with the increase of the optical density up to 20% while the final Al{sub 2}O{sub 3} layer thickness decreases at the same time up to 26%. All observations described above were detected to be Al{sub 2}O{sub 3} layer thickness dependent. These observations reveal novel aspects to explain the temperature induced passivation and degradation mechanisms of Al{sub 2}O{sub 3} layers at a molecular level like the origin of the negative fixe charges at the Si/SiO{sub x}/Al{sub 2}O{sub 3} interface or the phenomena of blistering. Moreover, the crystal phase of Al{sub 2}O{sub 3} does not deliver good surface passivation due to a high concentration of octahedral sites leading to a lower concentration of negative fixed charges at the interface.

  16. Synthesis and Characterization of High c-axis ZnO Thin Film by Plasma Enhanced Chemical Vapor Deposition System and its UV Photodetector Application.

    PubMed

    Chao, Chung-Hua; Wei, Da-Hua

    2015-10-03

    In this study, zinc oxide (ZnO) thin films with high c-axis (0002) preferential orientation have been successfully and effectively synthesized onto silicon (Si) substrates via different synthesized temperatures by using plasma enhanced chemical vapor deposition (PECVD) system. The effects of different synthesized temperatures on the crystal structure, surface morphologies and optical properties have been investigated. The X-ray diffraction (XRD) patterns indicated that the intensity of (0002) diffraction peak became stronger with increasing synthesized temperature until 400 (o)C. The diffraction intensity of (0002) peak gradually became weaker accompanying with appearance of (10-10) diffraction peak as the synthesized temperature up to excess of 400 (o)C. The RT photoluminescence (PL) spectra exhibited a strong near-band-edge (NBE) emission observed at around 375 nm and a negligible deep-level (DL) emission located at around 575 nm under high c-axis ZnO thin films. Field emission scanning electron microscopy (FE-SEM) images revealed the homogeneous surface and with small grain size distribution. The ZnO thin films have also been synthesized onto glass substrates under the same parameters for measuring the transmittance. For the purpose of ultraviolet (UV) photodetector application, the interdigitated platinum (Pt) thin film (thickness ~100 nm) fabricated via conventional optical lithography process and radio frequency (RF) magnetron sputtering. In order to reach Ohmic contact, the device was annealed in argon circumstances at 450 (o)C by rapid thermal annealing (RTA) system for 10 min. After the systematic measurements, the current-voltage (I-V) curve of photo and dark current and time-dependent photocurrent response results exhibited a good responsivity and reliability, indicating that the high c-axis ZnO thin film is a suitable sensing layer for UV photodetector application.

  17. High-temperature degradation in plasma-enhanced chemical vapor deposition Al2O3 surface passivation layers on crystalline silicon

    NASA Astrophysics Data System (ADS)

    Kühnhold, Saskia; Saint-Cast, Pierre; Kafle, Bishal; Hofmann, Marc; Colonna, Francesco; Zacharias, Margit

    2014-08-01

    In this publication, the activation and degradation of the passivation quality of plasma-enhanced chemical vapor deposited aluminum oxide (Al2O3) layers with different thicknesses (10 nm, 20 nm, and 110 nm) on crystalline silicon (c-Si) during long and high temperature treatments are investigated. As indicated by Fourier Transform Infrared Spectroscopy, the concentration of tetrahedral and octahedral sites within the Al2O3 layer changes during temperature treatments and correlates with the amount of negative fixed charges at the Si/Al2O3 interface, which was detected by Corona Oxide Characterization of Semiconductors. Furthermore, during a temperature treatment at 820 °C for 30 min, the initial amorphous Al2O3 layer crystallize into the γ-Al2O3 structure and was enhanced by additional oxygen as was proven by x-ray diffraction measurements and underlined by Density Functional Theory simulations. The crystallization correlates with the increase of the optical density up to 20% while the final Al2O3 layer thickness decreases at the same time up to 26%. All observations described above were detected to be Al2O3 layer thickness dependent. These observations reveal novel aspects to explain the temperature induced passivation and degradation mechanisms of Al2O3 layers at a molecular level like the origin of the negative fixe charges at the Si/SiOx/Al2O3 interface or the phenomena of blistering. Moreover, the crystal phase of Al2O3 does not deliver good surface passivation due to a high concentration of octahedral sites leading to a lower concentration of negative fixed charges at the interface.

  18. Gas diffusion ultrabarriers on polymer substrates using Al{sub 2}O{sub 3} atomic layer deposition and SiN plasma-enhanced chemical vapor deposition

    SciTech Connect

    Carcia, P. F.; McLean, R. S.; Groner, M. D.; Dameron, A. A.; George, S. M.

    2009-07-15

    Thin films grown by Al{sub 2}O{sub 3} atomic layer deposition (ALD) and SiN plasma-enhanced chemical vapor deposition (PECVD) have been tested as gas diffusion barriers either individually or as bilayers on polymer substrates. Single films of Al{sub 2}O{sub 3} ALD with thicknesses of >=10 nm had a water vapor transmission rate (WVTR) of <=5x10{sup -5} g/m{sup 2} day at 38 deg. C/85% relative humidity (RH), as measured by the Ca test. This WVTR value was limited by H{sub 2}O permeability through the epoxy seal, as determined by the Ca test for the glass lid control. In comparison, SiN PECVD films with a thickness of 100 nm had a WVTR of approx7x10{sup -3} g/m{sup 2} day at 38 deg. C/85% RH. Significant improvements resulted when the SiN PECVD film was coated with an Al{sub 2}O{sub 3} ALD film. An Al{sub 2}O{sub 3} ALD film with a thickness of only 5 nm on a SiN PECVD film with a thickness of 100 nm reduced the WVTR from approx7x10{sup -3} to <=5x10{sup -5} g/m{sup 2} day at 38 deg. C/85% RH. The reduction in the permeability for Al{sub 2}O{sub 3} ALD on the SiN PECVD films was attributed to either Al{sub 2}O{sub 3} ALD sealing defects in the SiN PECVD film or improved nucleation of Al{sub 2}O{sub 3} ALD on SiN.

  19. In situ B-doped Si epitaxial films grown at 450‡ C by remote plasma-enhanced chemical vapor deposition: Physical and electrical characterization

    NASA Astrophysics Data System (ADS)

    Irby, J.; Kinosky, D.; Hsu, T.; Qian, R.; Mahajan, A.; Thomas, S.; Anthony, B.; Banerjee, S.; Tasch, A.; Magee, C.

    1992-05-01

    In situ boron doping of Si epitaxial films grown at 450‡ C by remote plasma-enhanced chemical vapor deposition (RPCVD) has been studied using secondary ion mass spectroscopy (SIMS), Hall effect measurements, defect etching in conjunction with Nomarski microscopy, cross-sectional transmission electron microscopy (XTEM), and current-voltage measurements. Boron incorporation is shown to be controllable and electrically active from 7 × 1017 to over 1020 cm-3, with no dependence on process parameters (temperature, rf power, and substrate bias) in the ranges studied, other than the B2H6/SiH4 gas-phase ratio. No change in deposition rate upon introduction of B2H6 dopant gas is seen, contrary to what has been observed in several higher-temperature CVD processes. No defects such as stacking faults are seen under Nomarski microscopy, but a visible haze covers some areas of in situ B-doped wafers. This haze appears to consist of amorphous cone-shaped structures with their apexes at the substrate-epilayer interface. The origin of the conical defects is believed to be related to some phenomenon at the initiation of growth. In order to evaluate the electrical quality of in situ B-doped epilayers, P +/N mesa diodes have been fabricated using both homoepitaxial and heteroepitaxial (GexSi1-x) p-type epitaxial films. The electrical junction in these diodes coincides with the (epi-substrate)—interface in the grown films. To avoid interdiffusion or annealing effects during diode fabrication, all processing temperatures were kept at or below 450‡ C. Ideality factors are 1.2-1.3 for all diodes, indicating diffusion-limited transport rather than recombination in the depletion region.

  20. Vibrational spectroscopy study of Ar+-ion irradiated Si-rich oxide films grown by plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Mariotto, G.; Das, G.; Quaranta, A.; Della Mea, G.; Corni, F.; Tonini, R.

    2005-06-01

    SiOx thin films with different stoichiometry degree were obtained by plasma-enhanced chemical vapor deposition on crystalline silicon substrates from SiH4 and N2O gas mixtures. Two twin sets of samples were irradiated by 380 keV Ar+ ions at a fluence of 5×1016ions/cm2 at room temperature and at 500 °C, respectively, and then annealed in vacuum at different temperatures, between 500 and 1100 °C. A set of unirradiated samples has been annealed in the same conditions in order to discriminate the contribution of ion irradiation and of thermal treatments to the changes of the film microstructure. The structural modification of the oxide network and the growth of Si nanoclusters have been studied by vibrational spectroscopy techniques. Fourier transform infrared absorption spectra evidenced that ion irradiation induces a hydrogen loss of about 50%, and that postirradiation thermal treatments lead to the recovery of the irradiation defects and to the out diffusion of the residual hydrogen. After heating at 800 °C, irradiated and unirradiated samples exhibit substantially the same structure from the point of view of infrared-absorption spectra. In the meanwhile, the Si-O-Si stretching peak blue shifts, but never reaches the wavenumber value of pure silica owing to the presence of nitrogen into the network. Raman spectra of as-irradiated films reveal the presence of an amorphous silicon phase within the damaged layer of the oxide matrix. Raman spectra of irradiated samples undergoing thermal treatments at high temperature indicate a rearrangement of the film microstructure with the progressive clustering of the amorphous silicon phase. However, no clear spectroscopic evidence is gained about the crystallization of silicon nanoclusters, even after annealing at the highest temperature. In fact, the Raman scattering from silicon nanocrystals is partially hidden by the Raman peak of the c-Si substrate.

  1. Impact of In doping on GeTe phase-change materials thin films obtained by means of an innovative plasma enhanced metalorganic chemical vapor deposition process

    NASA Astrophysics Data System (ADS)

    Szkutnik, P. D.; Aoukar, M.; Todorova, V.; Angélidès, L.; Pelissier, B.; Jourde, D.; Michallon, P.; Vallée, C.; Noé, P.

    2017-03-01

    We investigated the deposition and the phase-change properties of In-doped GeTe thin films obtained by plasma enhanced metalorganic chemical vapor deposition and doped with indium using a solid delivery system. The sublimated indium precursor flow rate was calculated as a function of sublimation and deposition parameters. Indium related optical emission recorded by means of optical emission spectroscopy during deposition plasma allowed proposing the dissociation mechanisms of the [In(CH3)2N(CH3)2]2 solid precursor. In particular, using an Ar + H2 + NH3 deposition plasma, sublimated indium molecules are completely dissociated and do not induce by-product contamination by addition of nitrogen or carbon in the films. X-ray photoelectron spectroscopy evidences the formation of In-Te bonds in amorphous as-deposited In-doped GeTe films. The formation of an InTe phase after 400 °C annealing is also evidenced by means of X-ray diffraction analysis. The crystallization temperature Tx, deduced from monitoring of optical reflectivity of In-doped GeTe films with doping up to 11 at. % slightly varies as a function of the In dopant level with a decrease of Tx down to a minimum value for an In doping level of about 6-8 at. %. In this In doping range, the structure of crystallized In-GeTe films changes and is dominated by the presence of a crystalline In2Te3 phase. Finally, the Kissinger activation energy for crystallization Ea is showing to monotonically decrease as the indium content in the GeTe film is increased indicating a promising effect of In doping on crystallization speed in memory devices while keeping a good thermal stability for data retention.

  2. Synthesis and Characterization of High c-axis ZnO Thin Film by Plasma Enhanced Chemical Vapor Deposition System and its UV Photodetector Application

    PubMed Central

    Chao, Chung-Hua; Wei, Da-Hua

    2015-01-01

    In this study, zinc oxide (ZnO) thin films with high c-axis (0002) preferential orientation have been successfully and effectively synthesized onto silicon (Si) substrates via different synthesized temperatures by using plasma enhanced chemical vapor deposition (PECVD) system. The effects of different synthesized temperatures on the crystal structure, surface morphologies and optical properties have been investigated. The X-ray diffraction (XRD) patterns indicated that the intensity of (0002) diffraction peak became stronger with increasing synthesized temperature until 400 oC. The diffraction intensity of (0002) peak gradually became weaker accompanying with appearance of (10-10) diffraction peak as the synthesized temperature up to excess of 400 oC. The RT photoluminescence (PL) spectra exhibited a strong near-band-edge (NBE) emission observed at around 375 nm and a negligible deep-level (DL) emission located at around 575 nm under high c-axis ZnO thin films. Field emission scanning electron microscopy (FE-SEM) images revealed the homogeneous surface and with small grain size distribution. The ZnO thin films have also been synthesized onto glass substrates under the same parameters for measuring the transmittance. For the purpose of ultraviolet (UV) photodetector application, the interdigitated platinum (Pt) thin film (thickness ~100 nm) fabricated via conventional optical lithography process and radio frequency (RF) magnetron sputtering. In order to reach Ohmic contact, the device was annealed in argon circumstances at 450 oC by rapid thermal annealing (RTA) system for 10 min. After the systematic measurements, the current-voltage (I-V) curve of photo and dark current and time-dependent photocurrent response results exhibited a good responsivity and reliability, indicating that the high c-axis ZnO thin film is a suitable sensing layer for UV photodetector application. PMID:26484561

  3. SOLVENT FREE CHEMICAL TRANSFORMATION USING MICROWAVE IRRADIATION

    EPA Science Inventory

    Microwave-expedited solvent-free synthetic processes will be described that involve the exposure of neat reactants to microwave (MW) irradiation in the presence of supported reagents or catalysts on mineral oxides. Recent developments will be presented on the synthetic utility o...

  4. 'GREENER' CHEMICAL SYNTHESIS USING MICROWAVE IRRADIATION

    EPA Science Inventory

    A solvent-free approach that involves microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of recyclable mineral supports such as alumina, silica, clay, or 'doped' surfaces is presented which is applicable to a wide range of cleavage, condensation, cycl...

  5. Microwave Detection of Chemical Agents: A Review

    DTIC Science & Technology

    1986-06-01

    Health (NIOSH).8’l1 This instrument was designed to detect acetonitrile, acetaldehyde , acetone, carbonyl sulfide, ethanol, ethylene oxide, isopropyl...by Computer-Controlled Microwave Rota- tional Spectrometry. Applied Spectroscopy 32, 425 (1978). 20. Jones, G.E., and Beers , E.T. Determination of

  6. GREENER CHEMICAL SYNTHESES USING MICROWAVE IRRADIATION

    EPA Science Inventory

    Greener solvent-free protocols involve microwave (MW) exposure of neat reactants catalyzed by the surfaces of recyclable mineral supports such as alumina, silica and clay which are applicable to a wide range of cleavage, condensation, cyclization, oxidation and reduction reaction...

  7. GREENER CHEMICAL SYNTHESES USING MICROWAVE IRRADIATION

    EPA Science Inventory

    Greener solvent-free protocols involve microwave (MW) exposure of neat reactants catalyzed by the surfaces of recyclable mineral supports such as alumina, silica and clay which are applicable to a wide range of cleavage, condensation, cyclization, oxidation and reduction reaction...

  8. 'GREENER' CHEMICAL SYNTHESIS USING MICROWAVE IRRADIATION

    EPA Science Inventory

    A solvent-free approach that involves microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of recyclable mineral supports such as alumina, silica, clay, or 'doped' surfaces is presented which is applicable to a wide range of cleavage, condensation, cycl...

  9. Metal-boride phase formation on tungsten carbide (WC-Co) during microwave plasma chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Johnston, Jamin M.; Catledge, Shane A.

    2016-02-01

    Strengthening of cemented tungsten carbide by boriding is used to improve the wear resistance and lifetime of carbide tools; however, many conventional boriding techniques render the bulk carbide too brittle for extreme conditions, such as hard rock drilling. This research explored the variation in metal-boride phase formation during the microwave plasma enhanced chemical vapor deposition process at surface temperatures from 700 to 1100 °C. We showed several well-adhered metal-boride surface layers consisting of WCoB, CoB and/or W2CoB2 with average hardness from 23 to 27 GPa and average elastic modulus of 600-730 GPa. The metal-boride interlayer was shown to be an effective diffusion barrier against elemental cobalt; migration of elemental cobalt to the surface of the interlayer was significantly reduced. A combination of glancing angle X-ray diffraction, electron dispersive spectroscopy, nanoindentation and scratch testing was used to evaluate the surface composition and material properties. An evaluation of the material properties shows that plasma enhanced chemical vapor deposited borides formed at substrate temperatures of 800 °C, 850 °C, 900 °C and 1000 °C strengthen the material by increasing the hardness and elastic modulus of cemented tungsten carbide. Additionally, these boride surface layers may offer potential for adhesion of ultra-hard carbon coatings.

  10. Use of Optical Microscopy to Examine Crystallite Nucleation and Growth in Thermally Annealed Plasma Enhanced Chemical Vapor Deposition and Hot Wire Chemical Vapor Deposition a-Si:H Films

    SciTech Connect

    Mahan, A. H.; Dabney, M. S.; Reedy, Jr R. C.; Molina, D.; Ginley, D. S.

    2012-05-15

    We report a simple method to investigate crystallite nucleation and growth in stepwise, thermally annealed plasma enhanced chemical vapor deposition and hot wire chemical vapor deposition a-Si:H films. By confining film thicknesses to the range 500-4000 {angstrom}, optical microscopy in the reflection mode can be used to readily detect crystallites in the thermally annealed a-Si:H lattice. Measurements of the crystallite density versus annealing time for identically prepared films of different thickness show that the crystallite nucleation rate is smaller for thinner films, suggesting that crystallite nucleation is homogeneous, in agreement with previous results. A comparison of film nucleation rates with those obtained by other methods on identically prepared films shows excellent agreement, thus establishing the validity of the current technique. The potential effect of impurity (oxygen) incorporation during the stepwise annealing in air is shown not to affect crystallite nucleation and growth, in that SIMS oxygen profiles for stepwise versus continuous annealing show not only similar impurity profiles but also similar bulk impurity densities.

  11. ADVANCES IN GREEN CHEMISTRY: CHEMICAL SYNTHESES USING MICROWAVE IRRADIATION, ISBN 81-901238-5-8

    EPA Science Inventory

    16. Abstract Advances in Green Chemistry: Chemical Syntheses Using Microwave Irradiation
    Microwave-accelerated chemical syntheses in solvents as well as under solvent-free conditions have witnessed an explosive growth. The technique has found widespread application predomi...

  12. ADVANCES IN GREEN CHEMISTRY: CHEMICAL SYNTHESES USING MICROWAVE IRRADIATION, ISBN 81-901238-5-8

    EPA Science Inventory

    16. Abstract Advances in Green Chemistry: Chemical Syntheses Using Microwave Irradiation
    Microwave-accelerated chemical syntheses in solvents as well as under solvent-free conditions have witnessed an explosive growth. The technique has found widespread application predomi...

  13. EFFICIENT AND GREENER CHEMICAL SYNTHESES USING MICROWAVE IRRADIATION

    EPA Science Inventory

    The diverse nature of chemical entities requires various ‘green’ strategic pathways in our quest towards attaining sustainability. A solvent-free approach involving microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of less-expensive and rec...

  14. EFFICIENT AND GREENER CHEMICAL SYNTHESES USING MICROWAVE IRRADIATION

    EPA Science Inventory

    The diverse nature of chemical entities requires various ‘green’ strategic pathways in our quest towards attaining sustainability. A solvent-free approach involving microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of less-expensive and rec...

  15. Plasma enhanced chemical vapor deposition of wear resistant gradual a-Si{sub 1-x}:C{sub x}:H coatings on nickel-titanium for biomedical applications

    SciTech Connect

    Niermann, Benedikt; Boeke, Marc; Schauer, Janine-Christina; Winter, Joerg

    2010-03-15

    Plasma enhanced chemical vapor deposition has been used to deposit thin films with gradual transitions from silicon to carbon on Cu, Ni, stainless steel, and NiTi. Thus show low stress, elasticity, and wear resistance with excellent adhesion on all metals under investigation. Already at low Si concentrations of 10 at. % the intrinsic stress is considerably reduced compared to pure diamondlike carbon (DLC) films. The deposition process is controlled by optical emission spectroscopy. This technique has been applied to monitor the growth precursors and to correlate them with the film composition. The compositions of the films were determined by Rutherford backscattering spectroscopy and XPS measurements. Due to the elastic properties of the gradual transition and the excellent biocompatibility of DLC, the described film systems present a useful coating for biomedical applications.

  16. Excitation mechanism and thermal emission quenching of Tb ions in silicon rich silicon oxide thin films grown by plasma-enhanced chemical vapour deposition—Do we need silicon nanoclusters?

    SciTech Connect

    Podhorodecki, A. Golacki, L. W.; Zatryb, G.; Misiewicz, J.; Wang, J.; Jadwisienczak, W.; Fedus, K.

    2014-04-14

    In this work, we will discuss the excitation and emission properties of Tb ions in a Silicon Rich Silicon Oxide (SRSO) matrix obtained at different technological conditions. By means of electron cyclotron resonance plasma-enhanced chemical vapour deposition, undoped and doped SRSO films have been obtained with different Si content (33, 35, 39, 50 at. %) and were annealed at different temperatures (600, 900, 1100 °C). The samples were characterized optically and structurally using photoluminescence (PL), PL excitation, time resolved PL, absorption, cathodoluminescence, temperature dependent PL, Rutherford backscattering spectrometry, Fourier transform infrared spectroscopy and positron annihilation lifetime spectroscopy. Based on the obtained results, we discuss how the matrix modifications influence excitation and emission properties of Tb ions.

  17. Impacts of light illumination on monocrystalline silicon surfaces passivated by atomic layer deposited Al2O3 capped with plasma-enhanced chemical vapor deposited SiN x

    NASA Astrophysics Data System (ADS)

    Lin, Fen; Toh, Mei Gi; Thway, Maung; Li, Xinhang; Nandakumar, Naomi; Gay, Xavier; Dielissen, Bas; Raj, Samuel; Aberle, Armin G.

    2017-08-01

    In this work, we investigate the impact of light illumination on crystalline silicon surfaces passivated with inline atomic layer deposited aluminum oxide capped with plasma-enhanced chemical vapor deposited silicon nitride. It is found that, for dedicated n-type lifetime samples under illumination, there is no light induced degradation (LID) but enhanced passivation. The lifetime increase happened with a much faster speed compared to the lifetime decay during dark storage, resulting in the overall lifetime enhancement for actual field application scenarios (sunshine during the day and darkness during the night). In addition, it was found that the lifetime enhancement is spectrally dependent and mainly associated with the visible part of the solar spectrum. Hence, it has negligible impact for such interfaces applied on the rear of the solar cells, for example p-type aluminum local back surface field (Al-LBSF) cells.

  18. Chemical vapor deposition coating of fibers using microwave application

    NASA Technical Reports Server (NTRS)

    Barmatz, Martin B. (Inventor); Hoover, Gordon (Inventor); Jackson, Henry W. (Inventor)

    2000-01-01

    Chemical vapor deposition coating is carried out in a cylindrical cavity. The fibers are heated by a microwave source that is uses a TM0N0 mode, where O is an integer, and produces a field that depends substantially only on radius. The fibers are observed to determine their heating, and their position can be adjusted. Once the fibers are uniformly heated, a CVD reagent is added to process the fibers.

  19. Microwave detection of chemical agents: a review. Special publication, January 1982-July 1984

    SciTech Connect

    Christensen, S.D.

    1986-06-01

    This report represents an overview of microwave-detection techniques and an analysis of their possible application to chemical agent point and remote sensing. Microwave rotational spectroscopy and millimeter-wavelength radar are also discussed.

  20. Microwave-assisted specific chemical digestion for rapid protein identification.

    PubMed

    Hua, Lin; Low, Teck Yew; Sze, Siu Kwan

    2006-01-01

    We have developed a rapid microwave-assisted protein digestion technique based on classic acid hydrolysis reaction with 2% formic acid solution. In this mild chemical environment, proteins are hydrolyzed to peptides, which can be directly analyzed by MALDI-MS or ESI-MS without prior sample purification. Dilute formic acid cleaves proteins specifically at the C-terminal of aspartyl (Asp) residues within 10 min of exposure to microwave irradiation. By adjusting the irradiation time, we found that the extent of protein fragmentation can be controlled, as shown by the single fragmentation of myoglobin at the C-terminal of any of the Asp residues. The efficacy and simplicity of this technique for protein identification are demonstrated by the peptide mass maps of in-gel digested myoglobin and BSA, as well as proteins isolated from Escherichia coli K12 cells.

  1. Sub-micro a-C:H patterning of silicon surfaces assisted by atmospheric-pressure plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Boileau, Alexis; Gries, Thomas; Noël, Cédric; Perito Cardoso, Rodrigo; Belmonte, Thierry

    2016-11-01

    Micro and nano-patterning of surfaces is an increasingly popular challenge in the field of the miniaturization of devices assembled via top-down approaches. This study demonstrates the possibility of depositing sub-micrometric localized coatings—spots, lines or even more complex shapes—made of amorphous hydrogenated carbon (a-C:H) thanks to a moving XY stage. Deposition was performed on silicon substrates using chemical vapor deposition assisted by an argon atmospheric-pressure plasma jet. Acetylene was injected into the post-discharge region as a precursor by means of a glass capillary with a sub-micrometric diameter. A parametric study was carried out to study the influence of the geometric configurations (capillary diameter and capillary-plasma distance) on the deposited coating. Thus, the patterns formed were investigated by scanning electron microscopy and atomic force microscopy. Furthermore, the chemical composition of large coated areas was investigated by Fourier transform infrared spectroscopy according to the chosen atmospheric environment. The observed chemical bonds show that reactions of the gaseous precursor in the discharge region and both chemical and morphological stability of the patterns after treatment are strongly dependent on the surrounding gas. Various sub-micrometric a-C:H shapes were successfully deposited under controlled atmospheric conditions using argon as inerting gas. Overall, this new process of micro-scale additive manufacturing by atmospheric plasma offers unusually high-resolution at low cost.

  2. Material design of plasma-enhanced chemical vapour deposition SiCH films for low-k cap layers in the further scaling of ultra-large-scale integrated devices-Cu interconnects

    NASA Astrophysics Data System (ADS)

    Shimizu, Hideharu; Nagano, Shuji; Uedono, Akira; Tajima, Nobuo; Momose, Takeshi; Shimogaki, Yukihiro

    2013-10-01

    Cap layers for Cu interconnects in ultra-large-scale integrated devices (ULSIs), with a low dielectric constant (k-value) and strong barrier properties against Cu and moisture diffusion, are required for the future further scaling of ULSIs. There is a trade-off, however, between reducing the k-value and maintaining strong barrier properties. Using quantum mechanical simulations and other theoretical computations, we have designed ideal dielectrics: SiCH films with Si-C2H4-Si networks. Such films were estimated to have low porosity and low k; thus they are the key to realizing a cap layer with a low k and strong barrier properties against diffusion. For fabricating these ideal SiCH films, we designed four novel precursors: isobutyl trimethylsilane, diisobutyl dimethylsilane, 1, 1-divinylsilacyclopentane and 5-silaspiro [4,4] noname, based on quantum chemical calculations, because such fabrication is difficult by controlling only the process conditions in plasma-enhanced chemical vapor deposition (PECVD) using conventional precursors. We demonstrated that SiCH films prepared using these newly designed precursors had large amounts of Si-C2H4-Si networks and strong barrier properties. The pore structure of these films was then analyzed by positron annihilation spectroscopy, revealing that these SiCH films actually had low porosity, as we designed. These results validate our material and precursor design concepts for developing a PECVD process capable of fabricating a low-k cap layer.

  3. Material design of plasma-enhanced chemical vapour deposition SiCH films for low-k cap layers in the further scaling of ultra-large-scale integrated devices-Cu interconnects.

    PubMed

    Shimizu, Hideharu; Nagano, Shuji; Uedono, Akira; Tajima, Nobuo; Momose, Takeshi; Shimogaki, Yukihiro

    2013-10-01

    Cap layers for Cu interconnects in ultra-large-scale integrated devices (ULSIs), with a low dielectric constant (k-value) and strong barrier properties against Cu and moisture diffusion, are required for the future further scaling of ULSIs. There is a trade-off, however, between reducing the k-value and maintaining strong barrier properties. Using quantum mechanical simulations and other theoretical computations, we have designed ideal dielectrics: SiCH films with Si-C2H4-Si networks. Such films were estimated to have low porosity and low k; thus they are the key to realizing a cap layer with a low k and strong barrier properties against diffusion. For fabricating these ideal SiCH films, we designed four novel precursors: isobutyl trimethylsilane, diisobutyl dimethylsilane, 1, 1-divinylsilacyclopentane and 5-silaspiro [4,4] noname, based on quantum chemical calculations, because such fabrication is difficult by controlling only the process conditions in plasma-enhanced chemical vapor deposition (PECVD) using conventional precursors. We demonstrated that SiCH films prepared using these newly designed precursors had large amounts of Si-C2H4-Si networks and strong barrier properties. The pore structure of these films was then analyzed by positron annihilation spectroscopy, revealing that these SiCH films actually had low porosity, as we designed. These results validate our material and precursor design concepts for developing a PECVD process capable of fabricating a low-k cap layer.

  4. Control of carbon content in amorphous GeTe films deposited by plasma enhanced chemical vapor deposition (PE-MOCVD) for phase-change random access memory applications

    NASA Astrophysics Data System (ADS)

    Aoukar, M.; Szkutnik, P. D.; Jourde, D.; Pelissier, B.; Michallon, P.; Noé, P.; Vallée, C.

    2015-07-01

    Amorphous and smooth GeTe thin films are deposited on 200 mm silicon substrates by plasma enhanced—metal organic chemical vapor deposition (PE-MOCVD) using the commercial organometallic precursors TDMAGe and DIPTe as Ge and Te precursors, respectively. X-ray photoelectron spectroscopy (XPS) measurements show a stoichiometric composition of the deposited GeTe films but with high carbon contamination. Using information collected by Optical Emission Spectroscopy (OES) and XPS, the origin of carbon contamination is determined and the dissociation mechanisms of Ge and Te precursors in H2 + Ar plasma are proposed. As a result, carbon level is properly controlled by varying operating parameters such as plasma radio frequency power, pressure and H2 rate. Finally, GeTe films with carbon level as low as 5 at. % are obtained.

  5. Organo-Chlorinated Thin Films Deposited by Atmospheric Pressure Plasma-Enhanced Chemical Vapor Deposition for Adhesion Enhancement between Rubber and Zinc-Plated Steel Monofilaments.

    PubMed

    Vandenabeele, Cédric; Bulou, Simon; Maurau, Rémy; Siffer, Frederic; Belmonte, Thierry; Choquet, Patrick

    2015-07-08

    A continuous-flow plasma process working at atmospheric pressure is developed to enhance the adhesion between a rubber compound and a zinc-plated steel monofilament, with the long-term objective to find a potential alternative to the electrolytic brass plating process, which is currently used in tire industry. For this purpose, a highly efficient tubular dielectric barrier discharge reactor is built to allow the continuous treatment of "endless" cylindrical substrates. The best treatment conditions found regarding adhesion are Ar/O2 plasma pretreatment, followed by the deposition from dichloromethane of a 75 nm-thick organo-chlorinated plasma polymerized thin film. Ar/O2 pretreatment allows the removal of organic residues, coming from drawing lubricants, and induces external growth of zinc oxide. The plasma layer has to be preferably deposited at low power to conserve sufficient hydrocarbon moieties. Surface analyses reveal the complex chemical mechanism behind the establishment of strong adhesion levels, more than five times higher after the plasma treatment. During the vulcanization step, superficial ZnO reacts with the chlorinated species of the thin film and is converted into porous and granular bump-shaped ZnwOxHyClz nanostructures. Together, rubber additives diffuse through the plasma layer and lead to the formation of zinc sulfide on the substrate surface. Hence, two distinct interfaces, rubber/thin film and thin film/substrate, are established. On the basis of these observations, hypotheses explaining the high bonding strength results are formulated.

  6. Fundamental studies of defect generation in amorphous silicon alloys grown by remote plasma-enhanced chemical-vapor deposition. Final subcontract report, 1 July 1989--31 December 1992

    SciTech Connect

    Lucovsky, G.

    1993-08-01

    This report describes research to reduce the intrinsic bonding defects in amorphous and microcrystalline Si alloys by controlling the bonding chemistry and the microstructure via the deposition process reactions. The specific approach was to use remote plasma-enhanced, chemical-vapor deposition (PECVD) and reactive magnetron sputtering to limit the multiplicity of deposition inaction pathways, and thereby gain increased control over the thin-film chemistry and microstrucre. The research included (1) the deposition of amorphous and microcrystalline Si alloy materials by the PECVD process and by reactive magnetron sputtering, and (2) the evaluation of the material properties of these films for potential applications in PV devices. The focus of the research was on pining a fundamental understanding of the relationships between deposition reaction pathways, the bonding of dopant and alloy atoms, and the electrical provides of importance for PV applications. This involved studying the factors that contribute to defect generation and to defect removal and/or neutralization. In addition to the experimental studies, the research also included theoretical and modeling studies aimed at understanding the relationships between local atomic arrangements of Si and alloy atoms, and the electrical, optical, vibrational, and defect properties.

  7. Effect of Si and C concentration on the microstructure, and the mechanical, tribological and electrochemical properties of nanocomposite TiC/a-SiC:H/a-C:H coatings prepared by plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Li, Duanjie; Hassani, Salim; Poulin, Suzie; Szpunar, Jerzy A.; Martinu, Ludvik; Klemberg-Sapieha, Jolanta E.

    2012-02-01

    The nanocomposite TiC/a-SiC:H/a-C:H (presented as Ti-Si-C) coatings attract considerable interest due to their possible applications such as wear protective coatings, diffusion barriers, and materials for solar cells and electrical contacts. In order to explore new film properties and open new opportunities, in the present work, we prepare a series of C-rich Ti-Si-C coatings with different Si and C concentrations using plasma enhanced chemical vapor deposition, and we systematically investigate the effect of elemental composition on the microstructure, and on the mechanical, tribological and electrochemical properties. XRD and XPS analyses demonstrate that the Ti-Si-C coatings mainly consist of nanocrystalline (nc-) TiC embedded in amorphous (a-) SiC:H and a-C:H matrices. Ti-Si-C coatings with a high Si concentration possess enhanced mechanical properties (high hardness), while those with additional C exhibit superior tribological behaviors. The increase of Si and/or C concentrations leads to a grain size refinement of the TiC nanocrystals and to an expansion of the amorphous phase. This in turn substantially enhances their corrosion resistance. Ti-Si-C coatings with the highest Si or C contents exhibit the best corrosion performance among the tested samples by improving the corrosion resistance of the SS410 substrate by a factor of ˜400.

  8. Investigations on the Role of N2:(N2 + CH4) Ratio on the Growth of Hydrophobic Nanostructured Hydrogenated Carbon Nitride Thin Films by Plasma Enhanced Chemical Vapor Deposition at Low Temperature

    PubMed Central

    Khanis, Noor Hamizah; Ritikos, Richard; Ahmad Kamal, Shafarina Azlinda; Abdul Rahman, Saadah

    2017-01-01

    Nanostructured hydrogenated carbon nitride (CNx:H) thin films were synthesized on a crystal silicon substrate at low deposition temperature by radio-frequency plasma-enhanced chemical vapor deposition (PECVD). Methane and nitrogen were the precursor gases used in this deposition process. The effects of N2 to the total gas flow rate ratio on the formation of CNx:H nanostructures were investigated. Field-emission scanning electron microscopy (FESEM), Auger electron spectroscopy (AES), Raman scattering, and Fourier transform of infrared spectroscopies (FTIR) were used to characterize the films. The atomic nitrogen to carbon ratio and sp2 bonds in the film structure showed a strong influence on its growth rate, and its overall structure is strongly influenced by even small changes in the N2:(N2 + CH4) ratio. The formation of fibrous CNx:H nanorod structures occurs at ratios of 0.7 and 0.75, which also shows improved surface hydrophobic characteristic. Analysis showed that significant presence of isonitrile bonds in a more ordered film structure were important criteria contributing to the formation of vertically-aligned nanorods. The hydrophobicity of the CNx:H surface improved with the enhancement in the vertical alignment and uniformity in the distribution of the fibrous nanorod structures. PMID:28772460

  9. Chemical oxygen demand using closed microwave digestion system.

    PubMed

    Dharmadhikari, Dattatray M; Vanerkar, Atul P; Barhate, Nivedita M

    2005-08-15

    A new approach to determine the chemical oxygen demand (COD) using a closed microwave digestion (CMD) system to replace the conventional, time-consuming open reflux (OR) method is proposed. The procedure uses a laboratory-grade closed microwave digestion system (one magnetron) for the digestion of small volume of samples (3.0 mL) in a completely closed (90 mL) Teflon vessel, digesting 10 samples at a time in the range of COD values of 5-1000 mg L(-1). The digestion time required is 15 min as compared to the 2 h required for the conventional OR method. Chloride ion interference can be removed up to 6000 mg of Cl- ions L(-1) as compared to the 2000 mg of Cl- ions L(-1) removed by conventional OR method. The present work reveals that the filtration of effluent samples by membrane filter or homogenization is not essential to obtain reproducible results. The proposed method is cost-effective; saves time, energy, and reagents with providing precise results for both the pure organic compounds and wastewater samples; and is ecofriendly.

  10. Role of hydrogen on the deposition and properties of fluorinated silicon-nitride films prepared by inductively coupled plasma enhanced chemical vapor deposition using SiF{sub 4}/N{sub 2}/H{sub 2} mixtures

    SciTech Connect

    Fandino, J.; Santana, G.; Rodriguez-Fernandez, L.; Cheang-Wong, J.C.; Ortiz, A.; Alonso, J.C.

    2005-03-01

    Fluorinated silicon-nitride films have been prepared at low temperature (250 deg. C) by remote plasma enhanced chemical vapor deposition using mixtures of SiF{sub 4}, N{sub 2}, Ar, and various H{sub 2} flow rates. The deposited films were characterized by means of single wavelength ellipsometry, infrared transmission, resonant nuclear reactions, Rutherford backscattering analysis, and current-voltage measurements. It was found that films deposited without hydrogen grow with the highest deposition rate, however, they result with the highest fluorine content ({approx}27 at. %) and excess of silicon (Si/N ratio{approx_equal}1.75). These films also have the lowest refractive index and the highest etch rate, and exhibit very poor dielectric properties. As a consequence of the high fluorine content, these films hydrolize rapidly upon exposure to the ambient moisture, forming Si-H and N-H bonds, however, they do not oxidize completely. The addition of hydrogen to the deposition process reduces the deposition rate but improves systematically the stability and insulating properties of the films by reducing the amount of both silicon and fluorine incorporated during growth. All the fluorinated silicon-nitride films deposited at hydrogen flow rates higher than 3.5 sccm resulted free of Si-H bonds. In spite of the fact that films obtained at the highest hydrogen flow rate used in this work are still silicon rich (Si/N ratio{approx_equal}1.0) and contain a considerable amount of fluorine ({approx}16 at. %), they are chemically stable and show acceptable dielectric properties.

  11. Plasma-Enhanced Chemical Vapor Deposition (PE-CVD) yields better Hydrolytical Stability of Biocompatible SiOx Thin Films on Implant Alumina Ceramics compared to Rapid Thermal Evaporation Physical Vapor Deposition (PVD).

    PubMed

    Böke, Frederik; Giner, Ignacio; Keller, Adrian; Grundmeier, Guido; Fischer, Horst

    2016-07-20

    Densely sintered aluminum oxide (α-Al2O3) is chemically and biologically inert. To improve the interaction with biomolecules and cells, its surface has to be modified prior to use in biomedical applications. In this study, we compared two deposition techniques for adhesion promoting SiOx films to facilitate the coupling of stable organosilane monolayers on monolithic α-alumina; physical vapor deposition (PVD) by thermal evaporation and plasma enhanced chemical vapor deposition (PE-CVD). We also investigated the influence of etching on the formation of silanol surface groups using hydrogen peroxide and sulfuric acid solutions. The film characteristics, that is, surface morphology and surface chemistry, as well as the film stability and its adhesion properties under accelerated aging conditions were characterized by means of X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), inductively coupled plasma-optical emission spectroscopy (ICP-OES), and tensile strength tests. Differences in surface functionalization were investigated via two model organosilanes as well as the cell-cytotoxicity and viability on murine fibroblasts and human mesenchymal stromal cells (hMSC). We found that both SiOx interfaces did not affect the cell viability of both cell types. No significant differences between both films with regard to their interfacial tensile strength were detected, although failure mode analyses revealed a higher interfacial stability of the PE-CVD films compared to the PVD films. Twenty-eight day exposure to simulated body fluid (SBF) at 37 °C revealed a partial delamination of the thermally deposited PVD films whereas the PE-CVD films stayed largely intact. SiOx layers deposited by both PVD and PE-CVD may thus serve as viable adhesion-promoters for subsequent organosilane coupling agent binding to α-alumina. However, PE-CVD appears to be favorable for long-term direct film exposure to aqueous

  12. Experimental and theoretical rationalization of the growth mechanism of silicon quantum dots in non-stoichiometric SiN x : role of chlorine in plasma enhanced chemical vapour deposition.

    PubMed

    Mon-Pérez, E; Salazar, J; Ramos, E; Salazar, J Santoyo; Suárez, A López; Dutt, A; Santana, G; Monroy, B Marel

    2016-11-11

    Silicon quantum dots (Si-QDs) embedded in an insulator matrix are important from a technological and application point of view. Thus, being able to synthesize them in situ during the matrix growth process is technologically advantageous. The use of SiH2Cl2 as the silicon precursor in the plasma enhanced chemical vapour deposition (PECVD) process allows us to obtain Si-QDs without post-thermal annealing. Foremost in this work, is a theoretical rationalization of the mechanism responsible for Si-QD generation in a film including an analysis of the energy released by the extraction of HCl and the insertion of silylene species into the terminal surface bonds. From the results obtained using density functional theory (DFT), we propose an explanation of the mechanism responsible for the formation of Si-QDs in non-stoichiometric SiN x starting from chlorinated precursors in a PECVD system. Micrograph images obtained through transmission electron microscopy confirmed the presence of Si-QDs, even in nitrogen-rich (N-rich) samples. The film stoichiometry was controlled by varying the growth parameters, in particular the NH3/SiH2Cl2 ratio and hydrogen dilution. Experimental and theoretical results together show that using a PECVD system, along with chlorinated precursors it is possible to obtain Si-QDs at a low substrate temperature without annealing treatment. The optical property studies carried out in the present work highlight the prospects of these thin films for down shifting and as an antireflection coating in silicon solar cells.

  13. Experimental and theoretical rationalization of the growth mechanism of silicon quantum dots in non-stoichiometric SiN x : role of chlorine in plasma enhanced chemical vapour deposition

    NASA Astrophysics Data System (ADS)

    Mon-Pérez, E.; Salazar, J.; Ramos, E.; Santoyo Salazar, J.; López Suárez, A.; Dutt, A.; Santana, G.; Marel Monroy, B.

    2016-11-01

    Silicon quantum dots (Si-QDs) embedded in an insulator matrix are important from a technological and application point of view. Thus, being able to synthesize them in situ during the matrix growth process is technologically advantageous. The use of SiH2Cl2 as the silicon precursor in the plasma enhanced chemical vapour deposition (PECVD) process allows us to obtain Si-QDs without post-thermal annealing. Foremost in this work, is a theoretical rationalization of the mechanism responsible for Si-QD generation in a film including an analysis of the energy released by the extraction of HCl and the insertion of silylene species into the terminal surface bonds. From the results obtained using density functional theory (DFT), we propose an explanation of the mechanism responsible for the formation of Si-QDs in non-stoichiometric SiN x starting from chlorinated precursors in a PECVD system. Micrograph images obtained through transmission electron microscopy confirmed the presence of Si-QDs, even in nitrogen-rich (N-rich) samples. The film stoichiometry was controlled by varying the growth parameters, in particular the NH3/SiH2Cl2 ratio and hydrogen dilution. Experimental and theoretical results together show that using a PECVD system, along with chlorinated precursors it is possible to obtain Si-QDs at a low substrate temperature without annealing treatment. The optical property studies carried out in the present work highlight the prospects of these thin films for down shifting and as an antireflection coating in silicon solar cells.

  14. Microwave spectroscopy of chemical warfare agents: prospects for remote sensing

    NASA Astrophysics Data System (ADS)

    Samuels, Alan C.; Jensen, James O.; Suenram, Richard D.; Hight Walker, Angela R.; Woolard, Dwight L.

    1999-07-01

    The high level of interest in the sensor development community in millimeter wave technology development demonstrates the potential for several multipurpose applications of millimeter wave sensors. The potential for remote sensing of hazardous chemical materials based on their millimeter wave rotational signatures is yet another possible applications, offering certain distinct advantages over FTIR remote sensing. The high specificity of the rotational spectra to the molecular structures affords the capability of detecting chemical warfare (CW) agents and degradation products in complex mixtures including water vapor and smoke, an important consideration in military applications. Furthermore, the rotational modes are not complicated by electronic or vibrational transitions, reducing the potential for false alarms. We have conducted microwave spectroscopic measurements on two CW nerve agents (sarin and soman) and one blister agent (H-mustard). The assignment of the observed band furnishes us with an extremely accurate tool for predicting the rotational spectrum of these agents at any arbitrary frequency. By factoring in the effects of pressure (Lorentzian broadening and intensity reduction), we present the predicted spectral signatures of the CW agents in the 80 - 300 GHz region. This frequency regime is important for atmospheric monitoring as it exploits the wide bandwidth capability of millimeter wave sensors as well as the atmospheric windows that occur in this region.

  15. Ellipsometric investigation of nitrogen doped diamond thin films grown in microwave CH4/H2/N2 plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Ficek, Mateusz; Sankaran, Kamatchi J.; Ryl, Jacek; Bogdanowicz, Robert; Lin, I.-Nan; Haenen, Ken; Darowicki, Kazimierz

    2016-06-01

    The influence of N2 concentration (1%-8%) in CH4/H2/N2 plasma on structure and optical properties of nitrogen doped diamond (NDD) films was investigated. Thickness, roughness, and optical properties of the NDD films in the VIS-NIR range were investigated on the silicon substrates using spectroscopic ellipsometry. The samples exhibited relatively high refractive index (2.6 ± 0.25 at 550 nm) and extinction coefficient (0.05 ± 0.02 at 550 nm) with a transmittance of 60%. The optical investigation was supported by the molecular and atomic data delivered by Raman studies, bright field transmission electron microscopy imaging, and X-ray photoelectron spectroscopy diagnostics. Those results revealed that while the films grown in CH4/H2 plasma contained micron-sized diamond grains, the films grown using CH4/H2/(4%)N2 plasma exhibited ultranano-sized diamond grains along with n-diamond and i-carbon clusters, which were surrounded by amorphous carbon grain boundaries.

  16. Ellipsometric investigation of nitrogen doped diamond thin films grown in microwave CH{sub 4}/H{sub 2}/N{sub 2} plasma enhanced chemical vapor deposition

    SciTech Connect

    Ficek, Mateusz; Sankaran, Kamatchi J.; Haenen, Ken; Ryl, Jacek; Darowicki, Kazimierz; Lin, I-Nan

    2016-06-13

    The influence of N{sub 2} concentration (1%–8%) in CH{sub 4}/H{sub 2}/N{sub 2} plasma on structure and optical properties of nitrogen doped diamond (NDD) films was investigated. Thickness, roughness, and optical properties of the NDD films in the VIS–NIR range were investigated on the silicon substrates using spectroscopic ellipsometry. The samples exhibited relatively high refractive index (2.6 ± 0.25 at 550 nm) and extinction coefficient (0.05 ± 0.02 at 550 nm) with a transmittance of 60%. The optical investigation was supported by the molecular and atomic data delivered by Raman studies, bright field transmission electron microscopy imaging, and X-ray photoelectron spectroscopy diagnostics. Those results revealed that while the films grown in CH{sub 4}/H{sub 2} plasma contained micron-sized diamond grains, the films grown using CH{sub 4}/H{sub 2}/(4%)N{sub 2} plasma exhibited ultranano-sized diamond grains along with n-diamond and i-carbon clusters, which were surrounded by amorphous carbon grain boundaries.

  17. Physico-chemical characteristics of microwave-dried wheat distillers grain with solubles.

    PubMed

    Mosqueda, Maria Rosario P; Tabil, Lope G; Meda, Venkatesh

    2013-01-01

    Laboratory-prepared samples of wheat distillers grain with solubles with varying condensed distillers solubles (CDS) content were dried under varying microwave power, and microwave convection settings using a domestic microwave oven to examine their effect on the chemical, structural, color, flow, compression, thermal, and frictional properties of the product, which is dried distillers grain with solubles (DDGS). As CDS level increased, protein and ash content increased, while fat and fiber content decreased in wheat-based DDGS. Fat content was also markedly effected by the microwave oven drying conditions. While CDS level, microwave power or microwave convection setting, and/or their interactions significantly effected a number of physical properties; results indicated that CDS level had a stronger influence compared to the other factors. DDGS samples with high CDS levels were significantly denser, finer but more differentiated in size, less flowable, and less dispersible. These also produced denser and stronger pellets.

  18. SOLVENT-FREE CHEMICAL TRANSFORMATIONS USING MICROWAVE IRRADIATION

    EPA Science Inventory

    Microwave-expedited solvent-free synthetic processes will be described that involve the exposure of neat reactants to microwave (MW) irradiation in the presence of supported reagents or catalysts on mineral oxides. Recent developments will be presented on the synthetic utility o...

  19. [Effect of microwave on migration in the model environment of chemicals from materials that come into contact with foodstuffs].

    PubMed

    Aĭdinov, G V; Istomin, A V; Simileĭskaia, B S; Klimenko, O V; Berezina, T A; Efimushkina, L I

    2011-01-01

    Under the influence of microwaves is migration of chemical and metals used in manufacture for these furnaces. This confirms the need for research to develop modes of training materials used in the manufacture of utensils used in microwave ovens.

  20. A chemical/microwave technique for the measurement of bulk minority carrier lifetime in silicon wafers

    NASA Technical Reports Server (NTRS)

    Luke, Keung L.; Cheng, Li-Jen

    1988-01-01

    A chemical/microwave technique for the measurement of bulk minority carrier lifetime in silicon wafers is described. This method consists of a wet chemical treatment (surface cleaning, oxidation in solution, and measurement in HF solution) to passivate the silicon surfaces, a laser diode array for carrier excitation, and a microwave bridge measuring system which is more sensitive than the microwave systems used previously for lifetime measurement. Representative experimental data are presented to demonstrate this technique. The result reveals that this method is useful for the determination of bulk lifetime of commercial silicon wafers.

  1. Surface roughness of polyvinyl siloxane impression materials following chemical disinfection, autoclave and microwave sterilization.

    PubMed

    Al Kheraif, Abdulaziz Abdullah

    2013-05-01

    Autoclave sterilization and microwave sterilization has been suggested as the effective methods for the disinfection of elastomeric impressions, but subjecting elastomeric impressions to extreme temperature may have adverse effects on critical properties of the elastomers. To evaluate the effect of chemical disinfection as well as autoclave and microwave sterilization on the surface roughness of elastomeric impression materials. The surface roughness of five commercially available polyvinyl siloxane impression materials (Coltene President, Affinis Perfect impression, Aquasil, 3M ESPE Express and GC Exafast) were evaluated after subjecting them to chemical disinfection, autoclaving and microwave sterilization using a Talysurf Intra 50 instrument. Twenty specimens from each material were fabricated and divided into four equal groups, three experimental and one control (n=25). The differences in the mean surface roughness between the treatment groups were recorded and statistically analyzed. No statistically significant increase in the surface roughness was observed when the specimens were subjected to chemical disinfection and autoclave sterilization, increase in roughness and discoloration was observed in all the materials when specimens were subjected to microwave sterilization. Chemical disinfection did not have a significant effect but, since it is less effective, autoclave sterilization can be considered effective and autoclaving did not show any specimen discoloration as in microwave sterilization. Microwave sterilization may be considered when impressions are used to make diagnostic casts. A significant increase in surface roughness may produce rougher casts, resulting in rougher tissue surfaces for denture and cast restorations. Autoclave sterilization of vinyl polysiloxane elastomeric impressions for 5 minutes at 134°C at 20 psi may be considered an effective method over chemical disinfection and microwave sterilization, because chemical disinfection does

  2. Diamond growth on Fe-Cr-Al alloy by H{sub 2}-plasma enhanced graphite etching

    SciTech Connect

    Li, Y. S.; Hirose, A.

    2007-04-01

    Without intermediate layer and surface pretreatment, adherent diamond films with high initial nucleation density have been deposited on Fe-15Cr-5Al (wt. %) alloy substrate. The deposition was performed using microwave hydrogen plasma enhanced graphite etching in a wide temperature range from 370 to 740 degree sign C. The high nucleation density and growth rate of diamond are primarily attributed to the unique precursors used (hydrogen plasma etched graphite) and the chemical nature of the substrate. The improvement in diamond adhesion to steel alloys is ascribed to the important role played by Al, mitigation of the catalytic function of iron by suppressing the preferential formation of loose graphite intermediate phase on steel surface.

  3. 'GREENER' SOLVENT-FREE CHEMICAL SYNTHESIS USING MICROWAVE IRRADIATION

    EPA Science Inventory

    Solvent-free approach that involves microwave (MW) irradiation of neat reactants (undiluted) catalyzed by the surfaces of less-expensive and recyclable mineral supports such as alumina, silica, clay, or 'doped' surfaces is presented which is applicable to a wide range of cleavage...

  4. ‘GREENER’ CHEMICAL SYNTHESES USING MICROWAVE IRRADIATION (PRAGUE)

    EPA Science Inventory

    'Greener' solvent-free protocols involve microwave (MW) exposure of neat reactants catalyzed by the surfaces of recyclable mineral supports such as alumina, silica and clay which are applicable to a wide range of cleavage, condensation, cyclization, oxidation and reduction reacti...

  5. ‘GREENER’ CHEMICAL SYNTHESES USING MICROWAVE IRRADIATION (PRAGUE)

    EPA Science Inventory

    'Greener' solvent-free protocols involve microwave (MW) exposure of neat reactants catalyzed by the surfaces of recyclable mineral supports such as alumina, silica and clay which are applicable to a wide range of cleavage, condensation, cyclization, oxidation and reduction reacti...

  6. Determination of volatile chemicals released from microwave-heat-susceptor food packaging.

    PubMed

    McNeal, T P; Hollifield, H C

    1993-01-01

    Microwave heat susceptors that convert electromagnetic energy to heat attain high temperatures that make it possible to cook some foods to golden crispness in a microwave oven. Susceptors are typically packaged with foods intended for microwave use, e.g., waffles, pizzas, and french fries. The high temperatures > 302 degrees F used to cook some foods release trace levels of volatile chemicals from metalized polyester film, adhesive, and paper packaging materials; these volatile chemicals may be absorbed by the food. We simulated microwave susceptor cooking conditions and developed protocols by using headspace concentration capillary gas chromatography and mass spectrometry to identify volatile chemicals released from heated susceptors. We purchased a limited, cross-sectional sample of local retail microwave food products packaged with susceptors and used our protocol to analyze 10 different susceptor products. Although more than 140 unique chromatographic peaks were tabulated, only 44 volatile chemicals were identified, including 1,1,1-trichloroethane, benzene, and 2-(2-butoxyethoxy)ethanol, which were derived primarily from the paper and adhesive susceptor components. No one susceptor contained all the identified substances. The standard additions technique was the preferred method for quantitation. Trichloroethane and 2-(2-butoxyethoxy)ethanol were present in several products at 75-122 micrograms/in.2 of susceptor surface area. Benzene was found in 3 susceptors at < or = 0.22 microgram/in.2 levels. Examination indicates that adhesives used in more recent susceptor products were reformulated to remove even this trace level of benzene.

  7. A review of catalytic microwave pyrolysis of lignocellulosic biomass for value-added fuel and chemicals.

    PubMed

    Morgan, Hervan Marion; Bu, Quan; Liang, Jianghui; Liu, Yujing; Mao, Hanping; Shi, Aiping; Lei, Hanwu; Ruan, Roger

    2017-04-01

    Lignocellulosic biomass is an abundant renewable resource and can be efficiently converted into bio-energy by a bio-refinery. From the various techniques available for biomass thermo-chemical conversion; microwave assisted pyrolysis (MAP) seems to be the very promising. The principles of microwave technology were reviewed and the parameters for the efficient production of bio-oil using microwave technology were summarized. Microwave technology by itself cannot efficiently produce high quality bio-oil products, catalysts are used to improve the reaction conditions and selectivity for valued products during MAP. The catalysts used to optimize MAP are revised in the development of this article. The origins for bio-oils that are phenol rich or hydrocarbon rich are reviewed and their experimental results were summarized. The kinetics of MAP is discussed briefly in the development of the article. Future prospects and scientific development of MAP are also considered in the development of this article.

  8. A Comparative Study Between Microwave Irradiation and Sodium Hypochlorite Chemical Disinfection: A Prosthodontic View

    PubMed Central

    Goel, Kashish; Gupta, Rupesh; Solanki, Jitender

    2014-01-01

    Background: Prosthodontic procedures involving dental impressions, stone casts, record bases and prostheses may cause transmission of microorganisms between the patient, the dentist, auxiliary staff and laboratory personnel. In recent times, microwave radiation has gained wider acceptance in the field of applied science and has been used to reduce concentrations of bacteria and fungi, to dry dental casts,and to sterilize preparation media. Objective: This in-vitro study was conducted to compare microwave irradiation and 0.07% sodium hypochlorite chemical disinfection. The study also evaluated the effect of microwave irradiation and 0.07% sodium hypochlorite chemical disinfection on the dimensional stability of Kalstone casts. Materials and Methods: Forty impressions were made and divided into two groups of 20 each. Each group was contaminated with Staphylococcus aureus and Pseudomonas aeruginosa respectively. Each impression was divided into three parts and marked A, B, C. Impressions were then poured in kalastone. Part A of 20 kalastone casts were microwave disinfected, and Part B were chemically disinfected (0.07% NaOCl) while Part C were not disinfected and used as control. Results: On comparing the significant difference was seen in the microbial load between microwave and chemical disinfection (Z=56.480; p<0.001). Conclusion: On the basis of observations made for the antimicrobial assessment the microwave irradiated Kala stone casts proved to be a better disinfection method when compared with 0.07% sodium hypochlorite chemically disinfected incorporated cast. No significant difference was seen in the dimensional stability of Kala stone discs. PMID:24959515

  9. Organo- and nano-catalyst in greener reaction medium: Microwave-assisted expedient synthesis of fine chemicals

    EPA Science Inventory

    The use of emerging microwave (MW) -assisted chemistry techniques is dramatically reducing chemical waste and reaction times in several organic syntheses and chemical transformations. A brief account of our experiences in developing MW-assisted organic transformations, which invo...

  10. Chemical activation by mechanochemical mixing, microwave, and ultrasonic irradiation

    EPA Science Inventory

    The use of emerging MW-assisted chemistry techniques in conjunction with benign reaction media is dramatically reducing chemical waste ad reaction times in several organic syntheses and chemical transformations. This editorial comments on the recent developments in mechanochemica...

  11. Chemical activation by mechanochemical mixing, microwave, and ultrasonic irradiation

    EPA Science Inventory

    The use of emerging MW-assisted chemistry techniques in conjunction with benign reaction media is dramatically reducing chemical waste ad reaction times in several organic syntheses and chemical transformations. This editorial comments on the recent developments in mechanochemica...

  12. Microwave assisted conversion of microcrystalline cellulose into value added chemicals using dilute acid catalyst.

    PubMed

    Ching, Teck Wei; Haritos, Victoria; Tanksale, Akshat

    2017-02-10

    One of the grand challenges of this century is to transition fuels and chemicals production derived from fossil feedstocks to renewable feedstocks such as cellulosic biomass. Here we describe fast microwave conversion of microcrystalline cellulose (MCC) in water, with dilute acid catalyst to produce valuable platform chemicals. Single 10min microwave assisted treatment was able to convert >60% of MCC, with >50mol% yield of desirable products such as glucose, HMF, furfural and levulinic acid. Recycling of residual MCC with make-up fresh MCC resulted in an overall conversion of >93% after 5 cycles while maintaining >60% conversion in each cycle. Addition of isopropanol (70%v/v) as a co-solvent increased the yields of HMF and levulinic acid. This work shows for the first time proof of concept for complete conversion of recalcitrant microcrystalline cellulose in mild conditions of low temperature, dilute acid and short residence time using energy efficient microwave technology.

  13. Simulated experiment for elimination of air contaminated with odorous chemical agents by microwave plasma burner

    SciTech Connect

    Hong, Yong Cheol; Shin, Dong Hun; Uhm, Han Sup

    2007-10-15

    An experimental study on elimination of odorous chemical agent was carried out by making use of a microwave plasma burner, which consists of a microwave plasma torch and a reaction chamber with a fuel injector. Injection of hydrocarbon fuels into a high-temperature microwave torch plasma generates a plasma flame. The plasma flame can eliminate the odorous chemical agent diluted in air or purify the interior air of a large volume in isolated spaces. The specially designed reaction chamber eliminated H{sub 2}S and NH{sub 3} diluted in airflow rate of 5000 lpm (liters per minute), showing {beta} values of 46.52 and 39.69 J/l, respectively.

  14. Microwave assisted total synthesis of a benzothiophene-based new chemical entity (NCE)

    EPA Science Inventory

    Pharmaceutical scientists are required to generate diverse arrays of complex targets in short span of time, which can now be achieved by microwave-assisted organic synthesis. New chemical entities (NCE) can be built in a fraction of the time using this technique. However, there a...

  15. Sustainable synthesis of chemical entities by microwave heating with nano-catalysis in water

    EPA Science Inventory

    •Sustainable synthesis of chemical entities by microwave heating with nano-catalysis in water •CRADA’s with the private companies, CEM corporation and VeruTEK Technologies •Green Chemistry principles are accommodated via multi-faceted approach. Learning from nature- using na...

  16. MICROWAVE-INDUCED RAPID CHEMICAL FUNCTIONALIZATION OF SINGLE-WALLED CARBON NANOTUBES (R830901)

    EPA Science Inventory


    Abstract

    The microwave-induced chemical functionalization of single-walled carbon nanotubes (SWNTs) is reported. The major advantage of this high-energy procedure is that it reduced the reaction time to the order of minutes and the number of steps in the reac...

  17. Effect of anatomical characteristics and chemical components on microwave-assisted liquefaction of bamboo wastes

    Treesearch

    JiuLong Xie; XingYan Huang; JinQiu Qi; Chung Hse; Todd Shupe

    2014-01-01

    The epidermis layer waste (ELW) and the inner layer waste (ILW) were removed from Phyllostachys pubescens bamboo, and the anatomical characteristics and chemical components of these wastes were comparatively investigated. Both the ELW and the ILW were subjected to a microwave-assisted liquefaction process to evaluate the relationship between bamboo...

  18. Sustainable synthesis of chemical entities by microwave heating with nano-catalysis in water

    EPA Science Inventory

    •Sustainable synthesis of chemical entities by microwave heating with nano-catalysis in water •CRADA’s with the private companies, CEM corporation and VeruTEK Technologies •Green Chemistry principles are accommodated via multi-faceted approach. Learning from nature- using na...

  19. MICROWAVE-INDUCED RAPID CHEMICAL FUNCTIONALIZATION OF SINGLE-WALLED CARBON NANOTUBES (R830901)

    EPA Science Inventory


    Abstract

    The microwave-induced chemical functionalization of single-walled carbon nanotubes (SWNTs) is reported. The major advantage of this high-energy procedure is that it reduced the reaction time to the order of minutes and the number of steps in the reac...

  20. Microwave assisted total synthesis of a benzothiophene-based new chemical entity (NCE)

    EPA Science Inventory

    Pharmaceutical scientists are required to generate diverse arrays of complex targets in short span of time, which can now be achieved by microwave-assisted organic synthesis. New chemical entities (NCE) can be built in a fraction of the time using this technique. However, there a...

  1. Microwave-assisted chemical process for treatment of hazardous waste: Annual report

    SciTech Connect

    Varma, R.; Nandi, S.P.; Cleaveland, D.C.

    1987-10-01

    Microwave energy provides rapid in situ uniform heating and can be used to initiate chemical processes at moderate temperatures. We investigate the technical feasibility of microwave-assisted chemical processes for detoxification of liquid hazardous waste. Trichloroethylene, a major constituent of waste streams, was selected for this detoxification study. Experiments were performed to investigate the oxidative degradation of trichloroethylene over active carbons (with and without catalysts) in air streams with microwave in situ heating, and to examine the feasibility of regenerating the used carbons. This study established that trichloroethylene in a vapor stream can be adsorbed at room temperature on active carbon beds that are loaded with Cu and Cr catalysts. When the bed is heated by a microwave radiation to moderate temperatures (<400/sup 0/C) while a moist air stream is passed through it, the trichloroethylene is readily converted into less-noxious products such as HCl, CO, CO/sub 2/ and C/sub 2/H/sub 2/Cl/sub 2/. Conversion higher than 80% was observed. Furthermore, the used carbon bed can be conveniently regenerated by microwave heating while a moist-N/sub 2/ or moist-air stream is passed through the bed. 4 refs., 5 figs., 10 tabs.

  2. Hierarchy of Electronic Properties of Chemically Derived and Pristine Graphene Probed by Microwave Imaging

    SciTech Connect

    Kundhikanjana, W.

    2010-06-02

    Local electrical imaging using microwave impedance microscope is performed on graphene in different modalities, yielding a rich hierarchy of the local conductivity. The low-conductivity graphite oxide and its derivatives show significant electronic inhomogeneity. For the conductive chemical graphene, the residual defects lead to a systematic reduction of the microwave signals. In contrast, the signals on pristine graphene agree well with a lumped-element circuit model. The local impedance information can also be used to verify the electrical contact between overlapped graphene pieces.

  3. Plasma enhanced atomic layer deposition of silicon nitride using neopentasilane

    SciTech Connect

    Weeks, Stephen Nowling, Greg; Fuchigami, Nobi; Bowes, Michael; Littau, Karl

    2016-01-15

    Progress in transistor scaling has increased the demands on the material properties of silicon nitride (SiN{sub x}) thin films used in device fabrication and at the same time placed stringent restrictions on the deposition conditions employed. Recently, low temperature plasma enhanced atomic layer deposition has emerged as a viable technique for depositing these films with a thermal budget compatible with semiconductor processing at sub-32 nm technology nodes. For these depositions, it is desirable to use precursors that are free from carbon and halogens that can incorporate into the film. Beyond this, it is necessary to develop processing schemes that minimize the wet etch rate of the film as it will be subjected to wet chemical processing in subsequent fabrication steps. In this work, the authors introduce low temperature deposition of SiN{sub x} using neopentasilane [NPS, (SiH{sub 3}){sub 4}Si] in a plasma enhanced atomic layer deposition process with a direct N{sub 2} plasma. The growth with NPS is compared to a more common precursor, trisilylamine [TSA, (SiH{sub 3}){sub 3 }N] at identical process conditions. The wet etch rates of the films deposited with NPS are characterized at different plasma conditions and the impact of ion energy is discussed.

  4. Rapid, facile microwave-assisted synthesis of xanthan gum grafted polyaniline for chemical sensor.

    PubMed

    Pandey, Sadanand; Ramontja, James

    2016-08-01

    Grafting method, through microwave radiation procedure is extremely productive in terms of time consumption, cost effectiveness and environmental friendliness. In this study, conductive and thermally stable composite (mwXG-g-PANi) was synthesized by grafting of aniline (ANi) on to xanthan gum (XG) using catalytic weight of initiator, ammonium peroxydisulfate in the process of microwave irradiation in an aqueous medium. The synthesis of mwXG-g-PANi were confirm by FTIR, XRD, TGA, and SEM. The influence of altering the microwave power, exposure time of microwave, concentration of monomer and the amount of initiator of graft polymerization were studied over the grafting parameters, for example, grafting percentage (%G) and grafting efficiency (%E). The maximum %G and %E achieved was 172 and 74.13 respectively. The outcome demonstrates that the microwave irradiation strategy can increase the reaction rate by 72 times over the conventional method. Electrical conductivity of XG and mwXG-g-PANi composite film was performed. The fabricated grafted sample film were then examined for the chemical sensor. The mwXG-g-PANi, effectively integrated and handled, are NH3 sensitive and exhibit a rapid sensing in presence of NH3 vapor. Chemiresistive NH3 sensors with superior room temperature sensing performance were produced with sensor response of 905 at 1ppb and 90% recovery within few second.

  5. Isolation and characterization of cellulose nanofibers from bamboo using microwave liquefaction combined with chemical treatment and ultrasonication

    Treesearch

    Jiulong Xie; Chung Hse; Cornelis F. De Hoop; Tingxing Hu; Jinqiu Qi; Todd F. Shupe

    2016-01-01

    Cellulose nanofibers were successfully isolated from bamboo using microwave liquefaction combinedwith chemical treatment and ultrasonic nanofibrillation processes. The microwave liquefaction couldeliminate almost all the lignin in bamboo, resulting in high cellulose content residues within 7 min, andthe cellulose enriched residues could be readily purified by...

  6. Microwave-irradiation-assisted hybrid chemical approach for titanium dioxide nanoparticle synthesis: microbial and cytotoxicological evaluation.

    PubMed

    Ranjan, Shivendu; Dasgupta, Nandita; Rajendran, Bhavapriya; Avadhani, Ganesh S; Ramalingam, Chidambaram; Kumar, Ashutosh

    2016-06-01

    Titanium dioxide nanoparticles (TNPs) are widely used in the pharmaceutical and cosmetics industries. It is used for protection against UV exposure due to its light-scattering properties and high refractive index. Though TNPs are increasingly used, the synthesis of TNPs is tedious and time consuming; therefore, in the present study, microwave-assisted hybrid chemical approach was used for TNP synthesis. In the present study, we demonstrated that TNPs can be synthesized only in 2.5 h; however, the commonly used chemical approach using muffle furnace takes 5 h. The activity of TNP depends on the synthetic protocol; therefore, the present study also determined the effect of microwave-assisted hybrid chemical approach synthetic protocol on microbial and cytotoxicity. The results showed that TNP has the best antibacterial activity in decreasing order from Escherichia coli, Bacillus subtilis, and Staphylococcus aureus. The IC50 values of TNP for HCT116 and A549 were found to be 6.43 and 6.04 ppm, respectively. Cell death was also confirmed from trypan blue exclusion assay and membrane integrity loss was observed. Therefore, the study determines that the microwave-assisted hybrid chemical approach is time-saving; hence, this technique can be upgraded from lab scale to industrial scale via pilot plant scale. Moreover, it is necessary to find the mechanism of action at the molecular level to establish the reason for greater bacterial and cytotoxicological toxicity. Graphical abstract A graphical representation of TNP synthesis.

  7. Toroidal plasma enhanced CVD of diamond films

    SciTech Connect

    Zvanya, John Cullen, Christopher Morris, Thomas Krchnavek, Robert R.; Holber, William Basnett, Andrew Basnett, Robert; Hettinger, Jeffrey

    2014-09-01

    An inductively coupled toroidal plasma source is used as an alternative to microwave plasmas for chemical vapor deposition of diamond films. The source, operating at a frequency of 400 kHz, synthesizes diamond films from a mixture of argon, methane, and hydrogen. The toroidal design has been adapted to create a highly efficient environment for diamond film deposition: high gas temperature and a short distance from the sample to the plasma core. Using a toroidal plasma geometry operating in the medium frequency band allows for efficient (≈90%) coupling of AC line power to the plasma and a scalable path to high-power and large-area operation. In test runs, the source generates a high flux of atomic hydrogen over a large area, which is favorable for diamond film growth. Using a deposition temperature of 900–1050 °C and a source to sample distance of 0.1–2.0 cm, diamond films are deposited onto silicon substrates. The results showed that the deposition rate of the diamond films could be controlled using the sample temperature and source to sample spacing. The results also show the films exhibit good-quality polycrystalline diamond as verified by Raman spectroscopy, x-ray diffraction, and scanning electron microscopy. The scanning electron microscopy and x-ray diffraction results show that the samples exhibit diamond (111) and diamond (022) crystallites. The Raman results show that the sp{sup 3} peak has a narrow spectral width (FWHM 12 ± 0.5 cm{sup −1}) and that negligible amounts of the sp{sup 2} band are present, indicating good-quality diamond films.

  8. Microwave processing and diagnosis of chemically reacting materials in a single-mode cavity applicator

    NASA Astrophysics Data System (ADS)

    Jow, Jinder; Hawley, Martin C.; Finzel, Mark; Asmussen, Jes, Jr.; Lin, Haw-Hwa

    1987-12-01

    Online microwave processing and dielectric diagnosis of chemically reacting materials (epoxy/amine) have been successfully performed using a TM012-mode cylindrical cavity at a frequency of 2.45 GHz in conjunction with fluoroptic temperature measurement. Complex permittivity measurements by this single-frequency technique are repeatable and consistent with those obtained by conventional swept-frequency methods. The accuracy of complex permittivity measurements for both methods is within + or - 5 percent for permittivity and + or - 15 percent for loss. Both techniques are based on material-cavity perturbation theory. Perturbation equations for cylindrical shapes of the cavity and loaded material were derived to account for volume variation of the sample due to thermal expansion. Complex permittivity of epoxy/amine as a function of the extent of cure and temperature was determined in order to monitor the chemical reaction progress during microwave processing.

  9. Renewable platform chemicals from directional microwave-assisted liquefaction coupling stepwise extraction of waste biomass

    Treesearch

    Junfeng Feng; Chungyun Hse; Zhongzhi Yang; Kui Wang; Jianchun Jiang; Junming Xu

    2017-01-01

    Directional microwave-assisted liquefaction and stepwise extraction are introduced for producing platform chemicals: aromatics and monosaccharides. When sulfuric acid was used as a catalyst, a 45% monosaccharides yield and a 29% aromatics yield were obtained from bamboo with 0.3 g catalyst per 18 g methanol and 2 g bamboo at 160 °C with 10 min. Approximately 78–86 wt%...

  10. Microwave spectra of some sulfur and nitrogen compounds. [for chemical analysis

    NASA Technical Reports Server (NTRS)

    White, W. F.

    1974-01-01

    A computer-controlled microwave spectrometer was used to catalog reference spectra for chemical analysis. The apparatus, software, and experimental procedures are described. Tables of absorption frequencies, peak absorption coefficients, and integrated intensities are included for 13 sulfur compounds, 14 nitrogen compounds, and 1 compound containing both sulfur and nitrogen. The frequency range covered was 26,500 to 40,000 MHz for most compounds and 18,000 to 40,000 MHz for some.

  11. Effect of chemical and microwave disinfection on the surface microhardness of acrylic resin denture teeth.

    PubMed

    Vasconcelos, Ligia Regina; Consani, Rafael Leonardo Xediek; Mesquita, Marcelo Ferraz; Sinhoreti, Mário Alexandre Coelho

    2013-06-01

    The purpose of this study was to evaluate the effect of simulated disinfections (2% glutaraldehyde, 1% sodium hypochlorite, and microwave energy) on the surface hardness of Trilux, Biocler, Biotone, New Ace, and Magister commercial artificial teeth. Specimens (n = 10) were made with the teeth included individually in circular blocks of acrylic resin, leaving the labial surface exposed. Cycles of simulated chemical disinfection were accomplished with the specimens immersed in the solutions at room temperature for 10 minutes, followed by tap water washing for 30 seconds and storage in distilled water at room temperature for 7 days until the next disinfection. Simulated disinfection by microwave energy was carried out in a domestic oven with 1300 W at a potency of 50% for 3 minutes with the specimens individually immersed in 150 ml of distilled water. Control (no disinfection) and the experimental groups (first and third disinfection cycles) were submitted to Knoop hardness measurements with indentations at the center of the labial tooth surface. Data were submitted to repeated measure two-way ANOVA and Tukey's test (α = 0.05). Biocler, Magister, and Trilux showed lower surface microhardness when submitted to microwave. Lower microhardness for Biotone was promoted by hypochlorite, while no significant difference was shown for New Ace. The third disinfection cycle significantly decreased the tooth surface hardness only for microwave. Different disinfection methods promoted different effects on the microhardness of different types of artificial teeth. Surface microhardness of the teeth was less affected by the simulated chemical disinfections when compared to microwaved specimens. © 2013 by the American College of Prosthodontists.

  12. High-Throughput Microwave Spectroscopy for Chemical Kinetics and Trace Detection

    NASA Astrophysics Data System (ADS)

    Pate, Brooks

    2009-05-01

    Recent developments in high-speed digital electronics have made it possible to develop a new generation of broadband microwave spectrometers for molecular spectroscopy. These spectrometers acquire a broadband microwave spectrum (up to 12 GHz bandwidth in the current designs) in a single data acquisition event. Chirped pulse excitation is employed to efficiently polarize a molecular gas sample over the 12 GHz bandwidth using a pulse duration of about 1 microsecond. Following sample polarization, the free induction decay signal from the molecular rotational spectrum is directly digitized using a high-speed digital oscilloscope. The frequency domain spectrum is obtained by Fourier transform following coherent, time-domain signal averaging. The spectrometer design provides new capabilities for high-throughput chemical analysis. Applications to chemical identification of molecules of astrochemical interest will be presented. The broadband technique is well-suited to laser experiments where isomerization kinetics of highly excited molecules can be measured on the picosecond time scale through line shape analysis. Microwave-laser experiments for chemical reaction dynamics in pulsed jet samples and room-temperature gases will be presented.

  13. A comparison of the efficacy of mechanical, chemical, and microwave radiation methods in disinfecting complete dentures.

    PubMed

    Mojarad, Niloofar; Khalili, Zahra; Aalaei, Shima

    2017-01-01

    Poor denture hygiene can be a potential source of pathogens. The aim of this study was to compare the efficacy of microwave radiation with that of chemical and mechanical techniques in disinfecting complete dentures contaminated with Staphylococcus aureus and Pseudomonas aeruginosa. Seventy-two sterilized mandibular dentures were separately contaminated with S. aureus (n = 32) and P. aeruginosa (n = 32) and then incubated at 37°C for 48 h. The contaminated dentures were disinfected as follows: chemical disinfection with Corega tablets; chemical disinfection with 2% glutaraldehyde; mechanical disinfection by brushing the denture; and physical disinfection by 650-W microwaves irradiation for 3 min with six samples in each subgroup. Six dentures served as negative control group, and six contaminated dentures with no disinfection served as the positive control group. 10(-3)-10(-6) dilutions were cultured in the nutrient agar, and the colonies were counted after incubation at 37°C for 48 h. To evaluate the lasting time of disinfection, the containers with nutrient agar and dentures were stored for 7 days at 37°C to evaluate turbidity. Data were analyzed using Kruskal-Wallis and Mann-Whitney U-test (α = 0.05). There was no evidence of bacterial growth in 48 h and turbidity after 7 days of incubation of dentures disinfected by microwaves, glutaraldehyde, and Corega tablets, which was statistically significant compared to the positive controls (P < 0.001). In mechanically disinfected dentures (brushing), bacterial growth was detected after 48 h which was statistically significant compared to the positive controls (P < 0.001) and turbidity was seen in all the nutrient agar plates. Microwave iradiation, 2% glutaraldehyde, and Corega tablets disinfected complete dentures contaminated with S. aureus and P. aeruginosa which lasted for a long and a short terms.

  14. A comparison of the efficacy of mechanical, chemical, and microwave radiation methods in disinfecting complete dentures

    PubMed Central

    Mojarad, Niloofar; Khalili, Zahra; Aalaei, Shima

    2017-01-01

    Background: Poor denture hygiene can be a potential source of pathogens. The aim of this study was to compare the efficacy of microwave radiation with that of chemical and mechanical techniques in disinfecting complete dentures contaminated with Staphylococcus aureus and Pseudomonas aeruginosa. Materials and Methods: Seventy-two sterilized mandibular dentures were separately contaminated with S. aureus (n = 32) and P. aeruginosa (n = 32) and then incubated at 37°C for 48 h. The contaminated dentures were disinfected as follows: chemical disinfection with Corega tablets; chemical disinfection with 2% glutaraldehyde; mechanical disinfection by brushing the denture; and physical disinfection by 650-W microwaves irradiation for 3 min with six samples in each subgroup. Six dentures served as negative control group, and six contaminated dentures with no disinfection served as the positive control group. 10-3–10-6 dilutions were cultured in the nutrient agar, and the colonies were counted after incubation at 37°C for 48 h. To evaluate the lasting time of disinfection, the containers with nutrient agar and dentures were stored for 7 days at 37°C to evaluate turbidity. Data were analyzed using Kruskal–Wallis and Mann–Whitney U-test (α = 0.05). Results: There was no evidence of bacterial growth in 48 h and turbidity after 7 days of incubation of dentures disinfected by microwaves, glutaraldehyde, and Corega tablets, which was statistically significant compared to the positive controls (P < 0.001). In mechanically disinfected dentures (brushing), bacterial growth was detected after 48 h which was statistically significant compared to the positive controls (P < 0.001) and turbidity was seen in all the nutrient agar plates. Conclusion: Microwave iradiation, 2% glutaraldehyde, and Corega tablets disinfected complete dentures contaminated with S. aureus and P. aeruginosa which lasted for a long and a short terms. PMID:28584537

  15. Killing and preserving nematodes in soil samples with chemicals and microwave energy.

    PubMed

    Barker, K R; Gooding, G V; Elder, A S; Eplee, R E

    1972-04-01

    Three basic procedures for treating nematode-bearing soil samples for international shipment or from areas under quarantine were tested for their killing effect and recovery of nematodes by sugar flotation for diagnostic and advisory purposes. These were: fumigation with methyl bromide followed by storage at -15 C; microwave treatment (2450 MHz, 630 w, 2-5 min) followed by addition of FAA + picric acid or 5% Formalin; and adding chemical preservatives (FAA + picric acid, 5% Formalin, NAN, and 2-phenoxyethanol) directly to the soil. Larvae of Heterodera glycines in eggs within cysts were stimulated to hatch by 2-rain exposure to microwaves, and an exposure of 5 rain was required to kill them. Soil type and moisture significantly affected microwave effectiveness. Direct saturation of soil samples with preservative chemical solutions (FAA + picric acid or 5% Formalin) was most effective, and often increased the number of nematodes recovered. The high concentration (2%) of NaN a required for soil sterilization is too hazardous for routine work. NaN, therefore, is not recommended for this purpose.

  16. Potential use of microwave treatment on fresh-cut carrots: physical, chemical and microbiological aspects.

    PubMed

    Martínez-Hernández, Ginés Benito; Amodio, Maria Luisa; Colelli, Giancarlo

    2016-04-01

    The effect of microwave treatments (900 and 750 W for 45 and 60 s) on the microbial, physicochemical and sensory properties of fresh-cut carrot slices and the contents of several bioactive compounds was studied. Carrot samples were stored for 7 days at 5 °C. The microwaving of fresh-cut carrots reduced the initial respiration rate (8.6 CO2 mL kg(-1) h(-1)) by 55-74% compared with untreated samples, although the rates then increased during storage. The initial pH (6.7), titratable acidity (0.036%), soluble solid content (8.2 °Brix) and shelf-life of the samples did not differ greatly from those of the untreated samples. Microwaving prevented the incipient whitening and surface dryness during storage. In general, no significant changes in phenylalanine ammonia lyase activity (5.5 µmol t-cinnamic acid kg(-1) h(-1)), total phenolics (TP, 81.3 mg chlorogenic acid equivalent kg(-1) fresh weight (FW)) or total antioxidant capacity (TAC, 74.2 µmol Trolox equivalent kg(-1) FW) were observed on the processing day or over storage. However, the mildest treatment (750 W for 45 s) caused TP and TAC enhancements of 118 and 394% respectively after 7 days of shelf-life. Microwave treatments reduced the initial microbial loads of the samples by up to 1.8 log units, although their microbial growth was greater than that of the untreated samples throughout storage. Mild microwave treatments such as 750 W/45 s and 750 W/60 s are a good sustainable alternative to the use of NaOCl; however, combining them with other sanitizing techniques is needed to control microbial growth throughout the shelf-life of fresh-cut carrot slices. © 2015 Society of Chemical Industry.

  17. Diamond synthesis at atmospheric pressure by microwave capillary plasma chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Hemawan, Kadek W.; Gou, Huiyang; Hemley, Russell J.

    2015-11-01

    Polycrystalline diamond has been synthesized on silicon substrates at atmospheric pressure, using a microwave capillary plasma chemical vapor deposition technique. The CH4/Ar plasma was generated inside of quartz capillary tubes using 2.45 GHz microwave excitation without adding H2 into the deposition gas chemistry. Electronically excited species of CN, C2, Ar, N2, CH, Hβ, and Hα were observed in the emission spectra. Raman measurements of deposited material indicate the formation of well-crystallized diamond, as evidenced by the sharp T2g phonon at 1333 cm-1 peak relative to the Raman features of graphitic carbon. Field emission scanning electron microscopy images reveal that, depending on the growth conditions, the carbon microstructures of grown films exhibit "coral" and "cauliflower-like" morphologies or well-facetted diamond crystals with grain sizes ranging from 100 nm to 10 μm.

  18. Diamond synthesis at atmospheric pressure by microwave capillary plasma chemical vapor deposition

    DOE PAGES

    Gou, Huiyang; Hemley, Russell J.; Hemawan, Kadek W.

    2015-11-02

    Polycrystalline diamond has been successfully synthesized on silicon substrates at atmospheric pressure using a microwave capillary plasma chemical vapor deposition technique. The CH4/Ar plasma was generated inside of quartz capillary tubes using 2.45 GHz microwave excitation without adding H2 into the deposition gas chemistry. Electronically excited species of CN, C2, Ar, N2, CH, Hβ and Hα were observed in emission spectra. Raman measurements of deposited material indicate the formation of well-crystallized diamond, as evidenced by the sharp T2g phonon at 1333 cm-1 peak relative to the Raman features of graphitic carbon. Furthermore, field emission scanning electron microscopy (SEM) images revealmore » that, depending on the on growth conditions, the carbon microstructures of grown films exhibit “coral” and “cauliflower-like” morphologies or well-facetted diamond crystals with grain sizes ranging from 100 nm to 10 μm.« less

  19. Fourier transform microwave spectroscopy of chemical-warfare agents and their synthetic precursors

    NASA Astrophysics Data System (ADS)

    Hight Walker, Angela R.; Suenram, Richard D.; Samuels, Alan C.; Jensen, James O.; Woolard, Dwight L.; Wiebach, W.

    1999-01-01

    Fourier-transform microwave (FTMW) spectroscopy is an established is an established technique for observing the rotational spectra of molecules and complexes in molecular beams. Scientists at the National Institute of Standards and Technology (NIST) are adapting this measurement technology for applications in analytical chemistry. Presently, FTMW spectroscopy is being used to investigate chemical-warfare agents and their synthetic precursors. A FTMW spectroscopy facility has been established at a surety laboratory at the Edgewood Research, Development, and Engineering Center, where the capabilities exist for handling these deadly warfare agents. Here, the rotational spectra of Sarin, Soman and DF have been observed and assigned. Also, microwave spectroscopic studies of less toxic precursors such as pinacolyl alcohol, isopropyl alcohol, and thiodiglycol have been carried out at NIST. Tests will be undertaken to assess the potential of using FTMW spectroscopy for detecting trace amounts of chemical-warfare agents and precursors in air. A database of rotational transition frequencies is being compiled for use in conjunction with a FTMW spectrometer to unambiguously detect and monitor chemical weapons. The sensitivity and resolution of FTMW spectroscopy of FTMW spectroscopy suggest that the technique may offer real-time, unequivocal identification of chemical-warfare agents at trace vapor concentrations in air.

  20. Isolation and characterization of cellulose nanofibers from bamboo using microwave liquefaction combined with chemical treatment and ultrasonication.

    PubMed

    Xie, Jiulong; Hse, Chung-Yun; De Hoop, Cornelis F; Hu, Tingxing; Qi, Jinqiu; Shupe, Todd F

    2016-10-20

    Cellulose nanofibers were successfully isolated from bamboo using microwave liquefaction combined with chemical treatment and ultrasonic nanofibrillation processes. The microwave liquefaction could eliminate almost all the lignin in bamboo, resulting in high cellulose content residues within 7min, and the cellulose enriched residues could be readily purified by subsequent chemical treatments with lower chemical charging and quickly. The results of wet chemistry analyses, SEM images, and FTIR and X-ray spectra indicated the combination of microwave liquefaction and chemical treatment was significantly efficient in removing non-cellulosic compounds. Ultrasonication was used to separate the nanofibrils from the purified residues to extract nanofibers. The TEM images confirmed the presence of elementary fibrils, nano-sized fibril bundles, and aggregated fibril bundles. As evidenced by the TGA analysis, cellulose nanofibers isolated by this novel technique had high thermal stability indicating that the isolated nanofibers could possibly be applied as reinforcing elements in biomaterials. Copyright © 2016 Elsevier Ltd. All rights reserved.

  1. Novel microwave assisted chemical synthesis of Nd₂Fe₁₄B hard magnetic nanoparticles.

    PubMed

    Swaminathan, Viswanathan; Deheri, Pratap Kumar; Bhame, Shekhar Dnyaneswar; Ramanujan, Raju Vijayaraghavan

    2013-04-07

    The high coercivity and excellent energy product of Nd2Fe14B hard magnets have led to a large number of high value added industrial applications. Chemical synthesis of Nd2Fe14B nanoparticles is challenging due to the large reduction potential of Nd(3+) and the high tendency for Nd2Fe14B oxidation. We report the novel synthesis of Nd2Fe14B nanoparticles by a microwave assisted combustion process. The process consisted of Nd-Fe-B mixed oxide preparation by microwave assisted combustion, followed by the reduction of the mixed oxide by CaH2. This combustion process is fast, energy efficient and offers facile elemental substitution. The coercivity of the resulting powders was ∼8.0 kOe and the saturation magnetization was ∼40 emu g(-1). After removal of CaO by washing, saturation magnetization increased and an energy product of 3.57 MGOe was obtained. A range of magnetic properties was obtained by varying the microwave power, reduction temperature and Nd to Fe ratio. A transition from soft to exchange coupled to hard magnetic properties was obtained by varying the composition of NdxFe1-xB8 (x varies from 7% to 40%). This synthesis procedure offers an inexpensive and facile platform to produce exchange coupled hard magnets.

  2. Evaluation and comparison of high-level microwave oven disinfection with chemical disinfection of dental gypsum casts.

    PubMed

    Meghashri, K; Kumar, Prasanna; Prasad, D Krishna; Hegde, Rakshit

    2014-06-01

    The aim of this study was to evaluate and compare microwave disinfection with chemical disinfection of dental gypsum casts. A total of 120 casts were prepared from a silicone mold using Type III dental stone. Of the 120 casts, 60 casts were contaminated with 1 ml suspension of Staphylococcus aureus and 60 casts were contaminated with 1 ml suspension of Pseudomonas aeruginosa. Then, the casts were disinfected with microwave irradiation and chemical disinfection using the microwave oven and 0.5% sodium hypochlorite. Bacteriologic procedures were performed; the cfu/ml for each cast was calculated as a weighted mean. The results were analyzed using Kruskal-Wallis test and Mann-Whitney test. The untreated casts showed Brain heart infusion broth counts of 106 log cfu/ml compared to irradiated and chemically disinfected casts, in which 105 log reduction of cfu/ml was seen. These results satisfied the requirements of current infection control guidelines for the dental laboratory. The results obtained for chemical disinfection were in equivalence with microwave disinfection. Within the limitation of this in vitro study, it was found that microwave disinfection of casts for 5 min at 900 W gives high-level disinfection that complies with the current infection control guidelines for the dental laboratory and microwave disinfection method is an effective and validated method as chemical disinfection. How to cite the article: Meghashri K, Kumar P, Prasad DK, Hegde R. Evaluation and comparison of high-level microwave oven disinfection with chemical disinfection of dental gypsum casts. J Int Oral Health 2014;6(3):56-60 .

  3. Evaluation and Comparison of High-Level Microwave Oven Disinfection with Chemical Disinfection of Dental Gypsum Casts

    PubMed Central

    Meghashri, K; Kumar, Prasanna; Prasad, D Krishna; Hegde, Rakshit

    2014-01-01

    Background: The aim of this study was to evaluate and compare microwave disinfection with chemical disinfection of dental gypsum casts. Materials and Methods: A total of 120 casts were prepared from a silicone mold using Type III dental stone. Of the 120 casts, 60 casts were contaminated with 1 ml suspension of Staphylococcus aureus and 60 casts were contaminated with 1 ml suspension of Pseudomonas aeruginosa. Then, the casts were disinfected with microwave irradiation and chemical disinfection using the microwave oven and 0.5% sodium hypochlorite. Bacteriologic procedures were performed; the cfu/ml for each cast was calculated as a weighted mean. The results were analyzed using Kruskal-Wallis test and Mann-Whitney test. Results: The untreated casts showed Brain heart infusion broth counts of 106 log cfu/ml compared to irradiated and chemically disinfected casts, in which 105 log reduction of cfu/ml was seen. These results satisfied the requirements of current infection control guidelines for the dental laboratory. The results obtained for chemical disinfection were in equivalence with microwave disinfection. Conclusions: Within the limitation of this in vitro study, it was found that microwave disinfection of casts for 5 min at 900 W gives high-level disinfection that complies with the current infection control guidelines for the dental laboratory and microwave disinfection method is an effective and validated method as chemical disinfection. How to cite the article: Meghashri K, Kumar P, Prasad DK, Hegde R. Evaluation and comparison of high-level microwave oven disinfection with chemical disinfection of dental gypsum casts. J Int Oral Health 2014;6(3):56-60 . PMID:25083033

  4. Growth mechanism of carbon nanotubes grown by microwave plasma-assisted chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Muneyoshi, T.; Okai, M.; Yaguchi, T.; Sasaki, S.

    2001-10-01

    To investigate the most suitable deposition conditions and growth mechanism, we grew carbon nanotubes (CNTs) by microwave plasma-assisted chemical vapor deposition under various conditions. The experimental parameters we varied were (a) the mixture ratio of methane in hydrogen, (b) the total gas pressure, and (c) the bias electric current. We found that the bias electric current was the most influential parameter in determining the shape of CNTs. We believe that the growth process of CNTs can be explained by using the solid solubility curves of metal-carbon phase diagrams. Selective growth and low-temperature growth of CNTs can also be understood from these phase diagrams.

  5. SiC nanofibers grown by high power microwave plasma chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Honda, Shin-ichi; Baek, Yang-Gyu; Ikuno, Takashi; Kohara, Hidekazu; Katayama, Mitsuhiro; Oura, Kenjiro; Hirao, Takashi

    2003-05-01

    Silicon carbide (SiC) nanofibers have been synthesized on Si substrates covered by Ni thin films using high power microwave chemical vapor deposition (CVD). Characterization using transmission electron microscopy (TEM) combined with electron energy-dispersive X-ray spectroscopy (EDX) revealed that the resultant fibrous nanostructures were assigned to β-SiC with high crystallinity. The formation of SiC nanofibers can be explained by the vapor liquid solid (VLS) mechanism in which precipitation of SiC occurs from the supersaturated Ni nanoparticle containing Si and C.

  6. Recovery of phosphate from the supernatant of activated sludge pretreated by microwave irradiation through chemical precipitation.

    PubMed

    Xiao, Dean; Huang, Haiming; Jiang, Yang; Ding, Li

    2015-05-14

    This paper presents a technology of releasing phosphate from activated sludge by using a combined process of microwave irradiation and anaerobic stirring, followed by phosphate recovery from the resulting supernatant via chemical precipitation without addition of chemicals, except for a pH regulator. A series of experiments was conducted to examine the effects of microwave irradiation time, sludge solution pH, sludge concentration, and anaerobic stirring time on the release of phosphate. The results revealed that all of these parameters had a significant effect on the release of phosphate via the proposed combined process, and the combination of 180 s of microwave irradiation and 1 h of anaerobic stirring was found to give optimal phosphate release. When the sludge solution was acidized before pretreatment, the phosphate concentration of the supernatant increased rapidly. A 25 g/L sludge concentration was found to be optimal for the release of phosphate, beyond this concentration, there was no increase in the phosphate release. Under the optimal conditions of phosphate release (irradiation time, 180 s; solution pH, 2; sludge concentration, 25 g/L; anaerobic stirring time, 1 h), the total orthophosphate (PT) concentration in the supernatant reached 396 mg/L, accompanied by high concentrations of metal cations such as Ca, Mg, K, Al, and Fe. When the pH of the supernatant was adjusted to 9-10, the recovery efficiency of phosphate reached approximately 95 %. The analysis results indicated that the main components of the collected precipitates were amorphous calcium phosphate and struvite, which can be used as alternate phosphate minerals.

  7. Amorphous indium-gallium-zinc-oxide thin-film transistors using organic-inorganic hybrid films deposited by low-temperature plasma-enhanced chemical vapor deposition for all dielectric layers

    NASA Astrophysics Data System (ADS)

    Hsu, Chao-Jui; Chang, Ching-Hsiang; Chang, Kuei-Ming; Wu, Chung-Chih

    2017-01-01

    We investigated the deposition of high-performance organic-inorganic hybrid dielectric films by low-temperature (close to room temperature) inductively coupled plasma chemical vapor deposition (ICP-CVD) with hexamethyldisiloxane (HMDSO)/O2 precursor gas. The hybrid films exhibited low leakage currents and high breakdown fields, suitable for thin-film transistor (TFT) applications. They were successfully integrated into the gate insulator, the etch-stop layer, and the passivation layer for bottom-gate staggered amorphous In-Ga-Zn-O (a-IGZO) TFTs having the etch-stop configuration. With the double-active-layer configuration having a buffer a-IGZO back-channel layer grown in oxygen-rich atmosphere for better immunity against plasma damage, the etch-stop-type bottom-gate staggered a-IGZO TFTs with good TFT characteristics were successfully demonstrated. The TFTs showed good field-effect mobility (μFE), threshold voltage (V th), subthreshold swing (SS), and on/off ratio (I on/off) of 7.5 cm2 V-1 s-1, 2.38 V, 0.38 V/decade, and 2.2 × 108, respectively, manifesting their usefulness for a-IGZO TFTs.

  8. Plasma-enhanced CVD silicon nitride antireflection coatings for solar cells

    NASA Technical Reports Server (NTRS)

    Johnson, C. C.; Wydeven, T.; Donohoe, K.

    1983-01-01

    Multilayer plasma-enhanced chemical vapor deposition (PECVD) silicon nitride antireflection coatings were deposited on space quality silicon solar cells. Preliminary experiments indicated that multilayer coatings decreased the total reflectance of polished silicon from 35 percent to less than 3 percent over the spectral range 0.4-1.0 micron. The solar cell energy conversion efficiency was increased from an average of 8.84 percent to an average of 12.63 percent.

  9. Microwave plasma chemical synthesis of nanocrystalline carbon film structures and study their properties

    NASA Astrophysics Data System (ADS)

    Bushuev, N.; Yafarov, R.; Timoshenkov, V.; Orlov, S.; Starykh, D.

    2015-08-01

    The self-organization effect of diamond nanocrystals in polymer-graphite and carbon films is detected. The carbon materials deposition was carried from ethanol vapors out at low pressure using a highly non-equilibrium microwave plasma. Deposition processes of carbon film structures (diamond, graphite, graphene) is defined. Deposition processes of nanocrystalline structures containing diamond and graphite phases in different volume ratios is identified. The solid film was obtained under different conditions of microwave plasma chemical synthesis. We investigated the electrical properties of the nanocrystalline carbon films and identified it's from various factors. Influence of diamond-graphite film deposition mode in non-equilibrium microwave plasma at low pressure on emission characteristics was established. This effect is justified using the cluster model of the structure of amorphous carbon. It was shown that the reduction of bound hydrogen in carbon structures leads to a decrease in the threshold electric field of emission from 20-30 V/m to 5 V/m. Reducing the operating voltage field emission can improve mechanical stability of the synthesized film diamond-graphite emitters. Current density emission at least 20 A/cm2 was obtained. Nanocrystalline carbon film materials can be used to create a variety of functional elements in micro- and nanoelectronics and photonics such as cold electron source for emission in vacuum devices, photonic devices, cathodoluminescent flat display, highly efficient white light sources. The obtained graphene carbon net structure (with a net size about 6 μm) may be used for the manufacture of large-area transparent electrode for solar cells and cathodoluminescent light sources

  10. Synthesis of graphene by cobalt-catalyzed decomposition of methane in plasma-enhanced CVD: Optimization of experimental parameters with Taguchi method

    NASA Astrophysics Data System (ADS)

    Mehedi, H.-A.; Baudrillart, B.; Alloyeau, D.; Mouhoub, O.; Ricolleau, C.; Pham, V. D.; Chacon, C.; Gicquel, A.; Lagoute, J.; Farhat, S.

    2016-08-01

    This article describes the significant roles of process parameters in the deposition of graphene films via cobalt-catalyzed decomposition of methane diluted in hydrogen using plasma-enhanced chemical vapor deposition (PECVD). The influence of growth temperature (700-850 °C), molar concentration of methane (2%-20%), growth time (30-90 s), and microwave power (300-400 W) on graphene thickness and defect density is investigated using Taguchi method which enables reaching the optimal parameter settings by performing reduced number of experiments. Growth temperature is found to be the most influential parameter in minimizing the number of graphene layers, whereas microwave power has the second largest effect on crystalline quality and minor role on thickness of graphene films. The structural properties of PECVD graphene obtained with optimized synthesis conditions are investigated with Raman spectroscopy and corroborated with atomic-scale characterization performed by high-resolution transmission electron microscopy and scanning tunneling microscopy, which reveals formation of continuous film consisting of 2-7 high quality graphene layers.

  11. Synthesis of graphene by cobalt-catalyzed decomposition of methane in plasma-enhanced CVD: Optimization of experimental parameters with Taguchi method

    SciTech Connect

    Mehedi, H.-A.; Baudrillart, B.; Gicquel, A.; Farhat, S.; Alloyeau, D.; Mouhoub, O.; Ricolleau, C.; Pham, V. D.; Chacon, C.; Lagoute, J.

    2016-08-14

    This article describes the significant roles of process parameters in the deposition of graphene films via cobalt-catalyzed decomposition of methane diluted in hydrogen using plasma-enhanced chemical vapor deposition (PECVD). The influence of growth temperature (700–850 °C), molar concentration of methane (2%–20%), growth time (30–90 s), and microwave power (300–400 W) on graphene thickness and defect density is investigated using Taguchi method which enables reaching the optimal parameter settings by performing reduced number of experiments. Growth temperature is found to be the most influential parameter in minimizing the number of graphene layers, whereas microwave power has the second largest effect on crystalline quality and minor role on thickness of graphene films. The structural properties of PECVD graphene obtained with optimized synthesis conditions are investigated with Raman spectroscopy and corroborated with atomic-scale characterization performed by high-resolution transmission electron microscopy and scanning tunneling microscopy, which reveals formation of continuous film consisting of 2–7 high quality graphene layers.

  12. Renewable platform chemicals from directional microwave-assisted liquefaction coupling stepwise extraction of waste biomass.

    PubMed

    Feng, Junfeng; Hse, Chungyun; Yang, Zhongzhi; Wang, Kui; Jiang, Jianchun; Xu, Junming

    2017-11-01

    Directional microwave-assisted liquefaction and stepwise extraction are introduced for producing platform chemicals: aromatics and monosaccharides. When sulfuric acid was used as a catalyst, a 45% monosaccharides yield and a 29% aromatics yield were obtained from bamboo with 0.3g catalyst per 18g methanol and 2g bamboo at 160°C with 10min. Approximately 78-86wt% of the six biomass materials were converted into liquid products. After the stepwise extraction and precipitation process, the yields of monosaccharide derivatives and three phenolic compound fractions were 39-45% and 28-32%, respectively. Monosaccharides from holocellulose collected with a high purity of methyl glycosides were higher than 90%. Aromatic derivatives with different weight-molecular distributions were separated into three fractions with more than 80% phenolics. As their similar chemical properties within each fraction, platform chemicals have great commercial potential for producing high-quality chemicals and biofuels using mild upgrading conditions. Copyright © 2017. Published by Elsevier Ltd.

  13. Microwave plasma-assisted chemical vapor deposition of porous carbon film as supercapacitive electrodes

    NASA Astrophysics Data System (ADS)

    Wu, Ai-Min; Feng, Chen-Chen; Huang, Hao; Paredes Camacho, Ramon Alberto; Gao, Song; Lei, Ming-Kai; Cao, Guo-Zhong

    2017-07-01

    Highly porous carbon film (PCF) coated on nickel foam was prepared successfully by microwave plasma-assisted chemical vapor deposition (MPCVD) with C2H2 as carbon source and Ar as discharge gas. The PCF is uniform and dense with 3D-crosslinked nanoscale network structure possessing high degree of graphitization. When used as the electrode material in an electrochemical supercapacitor, the PCF samples verify their advantageous electrical conductivity, ion contact and electrochemical stability. The test results show that the sample prepared under 1000 W microwave power has good electrochemical performance. It displays the specific capacitance of 62.75 F/g at the current density of 2.0 A/g and retains 95% of its capacitance after 10,000 cycles at the current density of 2.0 A/g. Besides, its near-rectangular shape of the cyclic voltammograms (CV) curves exhibits typical character of an electric double-layer capacitor, which owns an enhanced ionic diffusion that can fit the requirements for energy storage applications.

  14. Diamond synthesis at atmospheric pressure by microwave capillary plasma chemical vapor deposition

    SciTech Connect

    Hemawan, Kadek W.; Gou, Huiyang; Hemley, Russell J.

    2015-11-02

    Polycrystalline diamond has been synthesized on silicon substrates at atmospheric pressure, using a microwave capillary plasma chemical vapor deposition technique. The CH{sub 4}/Ar plasma was generated inside of quartz capillary tubes using 2.45 GHz microwave excitation without adding H{sub 2} into the deposition gas chemistry. Electronically excited species of CN, C{sub 2}, Ar, N{sub 2}, CH, H{sub β}, and H{sub α} were observed in the emission spectra. Raman measurements of deposited material indicate the formation of well-crystallized diamond, as evidenced by the sharp T{sub 2g} phonon at 1333 cm{sup −1} peak relative to the Raman features of graphitic carbon. Field emission scanning electron microscopy images reveal that, depending on the growth conditions, the carbon microstructures of grown films exhibit “coral” and “cauliflower-like” morphologies or well-facetted diamond crystals with grain sizes ranging from 100 nm to 10 μm.

  15. Diamond synthesis at atmospheric pressure by microwave capillary plasma chemical vapor deposition

    SciTech Connect

    Gou, Huiyang; Hemley, Russell J.; Hemawan, Kadek W.

    2015-11-02

    Polycrystalline diamond has been successfully synthesized on silicon substrates at atmospheric pressure using a microwave capillary plasma chemical vapor deposition technique. The CH4/Ar plasma was generated inside of quartz capillary tubes using 2.45 GHz microwave excitation without adding H2 into the deposition gas chemistry. Electronically excited species of CN, C2, Ar, N2, CH, Hβ and Hα were observed in emission spectra. Raman measurements of deposited material indicate the formation of well-crystallized diamond, as evidenced by the sharp T2g phonon at 1333 cm-1 peak relative to the Raman features of graphitic carbon. Furthermore, field emission scanning electron microscopy (SEM) images reveal that, depending on the on growth conditions, the carbon microstructures of grown films exhibit “coral” and “cauliflower-like” morphologies or well-facetted diamond crystals with grain sizes ranging from 100 nm to 10 μm.

  16. Analysis of hydrogen plasma in a microwave plasma chemical vapor deposition reactor

    NASA Astrophysics Data System (ADS)

    Shivkumar, G.; Tholeti, S. S.; Alrefae, M. A.; Fisher, T. S.; Alexeenko, A. A.

    2016-03-01

    The aim of this work is to build a numerical model of hydrogen plasma inside a microwave plasma chemical vapor deposition system. This model will help in understanding and optimizing the conditions for the growth of carbon nanostructures. A 2D axisymmetric model of the system is implemented using the finite element high frequency Maxwell solver and the heat transfer solver in COMSOL Multiphysics. The system is modeled to study variation in parameters with reactor geometry, microwave power, and gas pressure. The results are compared with experimental measurements from the Q-branch of the H2 Fulcher band of hydrogen using an optical emission spectroscopy technique. The parameter γ in Füner's model is calibrated to match experimental observations at a power of 500 W and 30 Torr. Good agreement is found between the modeling and experimental results for a wide range of powers and pressures. The gas temperature exhibits a weak dependence on power and a strong dependence on gas pressure. The inclusion of a vertical dielectric pillar that concentrates the plasma increases the maximum electron temperature by 70%, the maximum gas temperature by 50%, and the maximum electron number density by 70% when compared to conditions without the pillar at 500 W and 30 Torr. Experimental observations also indicate intensified plasma with the inclusion of a pillar.

  17. Analysis of hydrogen plasma in a microwave plasma chemical vapor deposition reactor

    SciTech Connect

    Shivkumar, G.; Tholeti, S. S.; Alexeenko, A. A.; Alrefae, M. A.; Fisher, T. S.

    2016-03-21

    The aim of this work is to build a numerical model of hydrogen plasma inside a microwave plasma chemical vapor deposition system. This model will help in understanding and optimizing the conditions for the growth of carbon nanostructures. A 2D axisymmetric model of the system is implemented using the finite element high frequency Maxwell solver and the heat transfer solver in COMSOL Multiphysics. The system is modeled to study variation in parameters with reactor geometry, microwave power, and gas pressure. The results are compared with experimental measurements from the Q-branch of the H{sub 2} Fulcher band of hydrogen using an optical emission spectroscopy technique. The parameter γ in Füner's model is calibrated to match experimental observations at a power of 500 W and 30 Torr. Good agreement is found between the modeling and experimental results for a wide range of powers and pressures. The gas temperature exhibits a weak dependence on power and a strong dependence on gas pressure. The inclusion of a vertical dielectric pillar that concentrates the plasma increases the maximum electron temperature by 70%, the maximum gas temperature by 50%, and the maximum electron number density by 70% when compared to conditions without the pillar at 500 W and 30 Torr. Experimental observations also indicate intensified plasma with the inclusion of a pillar.

  18. Carbon nanofiber growth in plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Denysenko, I.; Ostrikov, K.; Cvelbar, U.; Mozetic, M.; Azarenkov, N. A.

    2008-10-01

    A theoretical model to describe the plasma-assisted growth of carbon nanofibers (CNFs) is proposed. Using the model, the plasma-related effects on the nanofiber growth parameters, such as the growth rate due to surface and bulk diffusion, the effective carbon flux to the catalyst surface, the characteristic residence time and diffusion length of carbon atoms on the catalyst surface, and the surface coverages, have been studied. The dependence of these parameters on the catalyst surface temperature and ion and etching gas fluxes to the catalyst surface is quantified. The optimum conditions under which a low-temperature plasma environment can benefit the CNF growth are formulated. These results are in good agreement with the available experimental data on CNF growth and can be used for optimizing synthesis of related nanoassemblies in low-temperature plasma-assisted nanofabrication.

  19. Synthesis and characterization of nanoparticles of CZTSe by microwave-assited chemical synthesis

    NASA Astrophysics Data System (ADS)

    Reyes Vallejo, O.; Sánchez, Mónica; Pal, Mou; Espinal, R.; Llorca, Jordi; Sebastian, P. J.

    2016-12-01

    In this study we present the synthesis of Cu2ZnSnSe4 (CZTSe) nanoparticles by microwave-assisted chemical synthesis employing organic solvents. The effect of reaction time, reactant concentration, solvent and additives (inorganic material) was studied on the structural and optical properties of the nanomaterials. The powder samples were analyzed by x-ray diffraction, Raman spectroscopy, x-ray energy dispersive spectroscopy and x-ray photoelectron spectroscopy. The results show that the synthesis performed with triethanolamine and deionized water is better than others solvents, producing nanocrystals of quaternary phase (CZTSe) with stoichiometric relations similar to the reported research in the literature, which falls in the range of Cu/(Zn+Sn): 0.8-1.0, Zn/Sn: 1.0-1.20. The nanoparticles of CZTSe synthesized in this study present desirable properties in order to use them in solar cell and photoelectrochemical cell applications.

  20. Low-temperature synthesis of graphene on nickel foil by microwave plasma chemical vapor deposition

    SciTech Connect

    Kim, Y.; Song, W.; Lee, S. Y.; Jeon, C.; Jung, W.; Kim, M.; Park, C.-Y.

    2011-06-27

    Microwave plasma chemical vapor deposition (MPCVD) was employed to synthesize high quality centimeter scale graphene film at low temperatures. Monolayer graphene was obtained by varying the gas mixing ratio of hydrogen and methane to 80:1. Using advantages of MPCVD, the synthesis temperature was decreased from 750 deg. C down to 450 deg. C. Optical microscopy and Raman mapping images exhibited that a large area monolayer graphene was synthesized regardless of the temperatures. Since the overall transparency of 89% and low sheet resistances ranging from 590 to 1855 {Omega}/sq of graphene films were achieved at considerably low synthesis temperatures, MPCVD can be adopted in manufacturing future large-area electronic devices based on graphene film.

  1. High growth rate homoepitaxial diamond film deposition at high temperatures by microwave plasma-assisted chemical vapor deposition

    NASA Technical Reports Server (NTRS)

    Vohra, Yogesh K. (Inventor); McCauley, Thomas S. (Inventor)

    1997-01-01

    The deposition of high quality diamond films at high linear growth rates and substrate temperatures for microwave-plasma chemical vapor deposition is disclosed. The linear growth rate achieved for this process is generally greater than 50 .mu.m/hr for high quality films, as compared to rates of less than 5 .mu.m/hr generally reported for MPCVD processes.

  2. Dynamical and chemical contributions to variability in microwave limb sounder Arctic stratoshperic column ozone

    NASA Technical Reports Server (NTRS)

    Manney, G.; Froidevaux, L.; Sabutis, J. L.; Santee, M. L.; Livesey, N. J.; Waters, J. W.

    2002-01-01

    Analyses of column ozone above 100 hPa (Col100) derived from Upper Atmosphere Research Satellite Microwave Limb Sounder (MLS) data in February/March 1992-1998 show that about half of the interannual variability in Col100 in the Arctic polar vortex in late winter results from interannual variability in chemical loss. A majority of the remainder results from interannual variability in day-to-day dynamical motions including adiabatic warming/cooling and poleward advection of underlying upper tropospheric subtropical air on short timescales, rather than from variations in descent rates and large-scale transport over the winters. The morphology of Col100 from MLS remains very similar to that in the dynamical models even in the years with most chemical ozone loss. The amount and character of day-to-day variability in dynamical models closely follows that in MLS Col100. Although the morphology of and day-to-day variability in Arctic column ozone are controlled by dynamical processes, chemical ozone loss was a major factor in producing both the low values of and the large interannual variability in Arctic column ozone observed during the 1990s.

  3. Hierarchy of Electronic Properties of Chemically Derived and Pristine Graphene Probed by Microwave Imaging

    NASA Astrophysics Data System (ADS)

    Kundhikanjana, Worasom; Lai, Keji; Wang, Hailiang; Dai, Hongjie; Kelly, Michael; Shen, Zhi-Xun

    2010-03-01

    AFM-compatible near-field microwave impedance microscope (MIM), capable of measuring local complex dielectric constant with 100 nm resolution, is used to study graphene in different modalities, with a hierarchy of electrical properties. The low-conductivity graphite oxide and its derivatives show significant electronic inhomogeneity. In the low DC resistance chemically exfoliated graphene sheets, the residual defects lead to appreciable electronics inhomogeneity. In contrast, the signals from pristine graphene are homogenous over the whole pieces. MIM provides an effective way to conduct a statistical study on many graphene pieces without requiring any contact electrode. When plotted as a function of the sheet areas, the signals from the pristine graphene agree well with a lumped-element circuit model, as expected for good conductors, while the signals from the chemical graphene systematically fall below the expected curve. The local impedance can also be used to verify the electrical contact between overlapped graphene pieces -- critical information but difficult to obtain by other methods.

  4. Cytotoxicity of Boron-Doped Nanocrystalline Diamond Films Prepared by Microwave Plasma Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Liu, Dan; Gou, Li; Ran, Junguo; Zhu, Hong; Zhang, Xiang

    2015-07-01

    Boron-doped nanocrystalline diamond (NCD) exhibits extraordinary mechanical properties and chemical stability, making it highly suitable for biomedical applications. For implant materials, the impact of boron-doped NCD films on the character of cell growth (i.e., adhesion, proliferation) is very important. Boron-doped NCD films with resistivity of 10-2 Ω·cm were grown on Si substrates by the microwave plasma chemical vapor deposition (MPCVD) process with H2 bubbled B2O3. The crystal structure, diamond character, surface morphology, and surface roughness of the boron-doped NCD films were analyzed using different characterization methods, such as X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The contact potential difference and possible boron distribution within the film were studied with a scanning kelvin force microscope (SKFM). The cytotoxicity of films was studied by in vitro tests, including fluorescence microscopy, SEM and MTT assay. Results indicated that the surface roughness value of NCD films was 56.6 nm and boron was probably accumulated at the boundaries between diamond agglomerates. MG-63 cells adhered well and exhibited a significant growth on the surface of films, suggesting that the boron-doped NCD films were non-toxic to cells. supported by the Open Foundation of State Key Laboratory of Electronic Thin Films and Integrated Devices (University of Electronic Science and Technology of China) (No. KFJJ201313)

  5. Role of the conducting layer substrate on TiO2 nucleation when using microwave activated chemical bath deposition

    NASA Astrophysics Data System (ADS)

    Zumeta, I.; Espinosa, R.; Ayllón, J. A.; Vigil, E.

    2002-12-01

    Nanostructured TiO2 is used in novel dye sensitized solar cells. Because of their interaction with light, thin TiO2 films are also used as coatings for self-cleaning glasses and tiles. Microwave activated chemical bath deposition represents a simple and cost-effective way to obtain nanostructured TiO2 films. It is important to study, in this technique, the role of the conducting layer used as the substrate. The influence of microwave-substrate interactions on TiO2 deposition is analysed using different substrate positions, employing substrates with different conductivities, and also using different microwave radiation powers for film deposition. We prove that a common domestic microwave oven with a large cavity and inhomogeneous radiation field can be used with equally satisfactory results. The transmittance spectra of the obtained films were studied and used to analyse film thickness and to obtain gap energy values. The results, regarding different indium-tin oxide resistivities and different substrate positions in the oven cavity, show that the interaction of the microwave field with the conducting layer is determinant in layer deposition. It has also been found that film thickness increases with the power of the applied radiation while the gap energies of the TiO2 films decrease approaching the 3.2 eV value reported for bulk anatase. This indicates that these films are not crystalline and it agrees with x-ray spectra that do not reveal any peak.

  6. Effect of ultrasonic and microwave disintegration on physico-chemical and biodegradation characteristics of waste-activated sludge.

    PubMed

    Doğruel, Serdar; Özgen, Aslı Sedem

    2017-04-01

    The purpose of this study was to investigate the effect of ultrasonic and microwave disintegration on physico-chemical and biodegradability properties of waste-activated sludge (WAS) from a municipal wastewater treatment plant. Another aim was to carry out particle size distribution (PSD) analysis as an integral component of sludge characterization to highlight the transformation mechanisms involved in pretreatment processes and better understand the biodegradation patterns of sonicated and irradiated WAS liquids examined by means of respirometric measurements. Various combinations of sonication and microwave irradiation parameters were applied to optimize operating conditions. The optimum ultrasonic density was determined as 1.5 W/mL, and energy dosages lower than 30,000 kJ/kg TS resulted in a fairly linear increase in the soluble chemical oxygen demand (SCOD) release. An irradiation time of 10 min and a temperature of 175°C were selected as the optimum microwave pretreatment conditions for sludge liquefaction. The most apparent impact of ultrasonication on the PSD of COD was the shifting of the peak at the particulate fraction (>1600 nm) toward the lowest size range (<2 nm). Microwave heating at the selected experimental conditions and ultrasonic pretreatment at 30,000 kJ/kg TS exhibited comparable size distribution and biodegradation characteristics to those of domestic sewage.

  7. Synthesis of SiV-diamond particulates via the microwave plasma chemical deposition of ultrananocrystalline diamond on soda-lime glass fibers

    NASA Astrophysics Data System (ADS)

    Kunuku, Srinivasu; Chen, Yen-Chun; Yeh, Chien-Jui; Chang, Wen-Hao; Manoharan, Divinah; Leou, Keh-Chyang; Lin, I.-Nan

    2016-10-01

    We report the synthesis of silicon-vacancy (SiV) incorporated spherical shaped ultrananocrystalline diamond (SiV-UNCD) particulates (size ∼1 μm) with bright luminescence at 738 nm. For this purpose, different granular structured polycrystalline diamond films and particulates were synthesized by using three different kinds of growth plasma conditions on the three types of substrate materials in the microwave plasma enhanced CVD process. The grain size dependent photoluminescence properties of nitrogen vacancy (NV) and SiV color centers have been investigated for different granular structured diamond samples. The luminescence of NV center and the associated phonon sidebands, which are usually observed in microcrystalline diamond and nanocrystalline diamond films, were effectively suppressed in UNCD films and UNCD particulates. Micron sized SiV-UNCD particulates with bright SiV emission has been attained by transfer of SiV-UNCD clusters on soda-lime glass fibers to inverted pyramidal cavities fabricated on Si substrates by the simple crushing of UNCD/soda-lime glass fibers in deionized water and ultrasonication. Such a plasma enhanced CVD process for synthesizing SiV-UNCD particulates with suppressed NV emission is simple and robust to attain the bright SiV-UNCD particulates to employ in practical applications.

  8. Physical and Chemical Properties of Bio-Oils From Microwave Pyrolysis of Corn Stover

    NASA Astrophysics Data System (ADS)

    Yu, Fei; Deng, Shaobo; Chen, Paul; Liu, Yuhuan; Wan, Yiqin; Olson, Andrew; Kittelson, David; Ruan, Roger

    This study was aimed to understand the physical and chemical properties of pyrolytic bio-oils produced from microwave pyrolysis of corn stover regarding their potential use as gas turbine and home heating fuels. The ash content, solids content, pH, heating value, minerals, elemental ratio, moisture content, and viscosity of the bio-oils were determined. The water content was approx 15.2 wt%, solids content 0.22 wt%, alkali metal content 12 parts per million, dynamic viscosity 185 mPa·s at 40°C, and gross high heating value 17.5 MJ/kg for a typical bio-oil produced. Our aging tests showed that the viscosity and water content increased and phase separation occurred during the storage at different temperatures. Adding methanol and/or ethanol to the bio-oils reduced the viscosity and slowed down the increase in viscosity and water content during the storage. Blending of methanol or ethanol with the bio-oils may be a simple and cost-effective approach to making the pyrolytic bio-oils into a stable gas turbine or home heating fuels.

  9. Physical and chemical properties of bio-oils from microwave pyrolysis of corn stover.

    PubMed

    Yu, Fei; Deng, Shaobo; Chen, Paul; Liu, Yuhuan; Wan, Yiqin; Olson, Andrew; Kittelson, David; Ruan, Roger

    2007-04-01

    This study was aimed to understand the physical and chemical properties of pyrolytic bio-oils produced from microwave pyrolysis of corn stover regarding their potential use as gas turbine and home heating fuels. The ash content, solids content, pH, heating value, minerals, elemental ratio, moisture content, and viscosity of the bio-oils were determined. The water content was approx 15.2 wt%, solids content 0.22 wt%, alkali metal content 12 parts per million, dynamic viscosity 185 mPa.s at 40 degrees C, and gross high heating value 17.5 MJ/kg for a typical bio-oil produced. Our aging tests showed that the viscosity and water content increased and phase separation occurred during the storage at different temperatures. Adding methanol and/or ethanol to the bio-oils reduced the viscosity and slowed down the increase in viscosity and water content during the storage. Blending of methanol or ethanol with the bio-oils may be a simple and cost-effective approach to making the pyrolytic bio-oils into a stable gas turbine or home heating fuels.

  10. Differing morphologies of textured diamond films with electrical properties made with microwave plasma chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Lai, Wen Chi; Wu, Yu-Shiang; Chang, Hou-Cheng; Lee, Yuan-Haun

    2010-12-01

    This study investigates the orientation of textured diamond films produced through microwave plasma chemical vapor deposition (MPCVD) at 1200 W, 110 Torr, CH 4/H 2 = 1/20, with depositions times of 0.5-4.0 h. After a growth period of 2.0-4.0 h, this particular morphology revealed a rectangular structure stacked regularly on the diamond film. The orientation on {1 1 1}-textured diamond films grew a preferred orientation of {1 1 0} on the surface, as measured by XRD. The formation of the diamond epitaxial film formed textured octahedrons in ball shaped (or cauliflower-like) diamonds in the early stages (0.5 h), and the surface of the diamond film extended to pile the rectangular structure at 4.0 h. The width of the tier was approximately 200 nm at the 3.0 h point of deposition, according to TEM images. The results revealed that the textured diamond films showed two different morphological structures (typical ball shaped and rectangular diamonds), at different stages of the deposition period. The I- V characteristics of the oriented diamond films after 4.0 h of deposition time showed good conformity with the ohmic contact.

  11. Aura Microwave Limb Sounder Animation Illustrating the Interaction Between Temperatures and Chemicals Involved in Ozone Destruction, 2004-2005 Arctic Winter

    NASA Image and Video Library

    2005-06-02

    This still from an animation created from data from the Microwave Limb Sounder instrument on NASA Aura spacecraft depicts the complex interaction of chemicals involved in the destruction of ozone during the 2005 Arctic winter.

  12. Microwave-assisted chemical reduction routes for direct synthesis of (fct) L1 phase of Fe-Pt.

    PubMed

    Acharya, Smita; Singh, Kamal

    2011-01-01

    Microwave-assisted chemical reduction route has been explored for the direct synthesis of fct L1(0) - phase of Fe-Pt nanoparticles in the present work. Effects of microwave power and irradiation time on the growth process are systematically studied. Using this facile and high yield technique we could tune particle size from 7 to 17 nm. Prepared Fe-Pt NPs exhibited ordered face centered tetragonal (fct) L1(0) phase without any post-synthesis treatment. The particle size and magnetic properties of the prepared Fe-Pt were found to be very sensitive to the microwave irradiation power, while influence of exposure time was insignificant. The hysteresis measurements were performed at 300 K to study magnetic properties of the synthesized Fe-Pt as a function of crystallite size. Coercivity and saturation magnetization were observed to be decreasing with diminishing particle size. The microwave-assisted route is found to be a simple technique for direct synthesis of metal alloys and may prove to be a potential tool of high density data storage materials such as Fe-Pt.

  13. Trivalent manganese as an environmentally friendly oxidizing reagent for microwave- and ultrasound-assisted chemical oxygen demand determination.

    PubMed

    Domini, Claudia E; Vidal, Lorena; Canals, Antonio

    2009-06-01

    In the present work manganese(III) has been used as oxidant and microwave radiation and ultrasound energy have been assessed to speed up and to improve the efficiency of digestion step for the determination of chemical oxygen demand (COD). Microwave (MW) and ultrasound-assisted COD determination methods have been optimized by means of experimental design and the optimum conditions are: 40psi pressure, 855W power and 1min irradiation time; and 90% of maximum nominal power (180W), 0.9s (s(-1)) cycles and 1min irradiation time for microwaves and ultrasound, respectively. Chloride ion interference is removed as hydrochloric acid gas from acidified sample solutions at 150 degrees C in a closed reaction tube and captured by bismuth-based adsorbent suspended above the heated solution. Under optimum conditions, the evaluated assisted digestion methods have been successfully applied, with the exception of pyridine, to several pure organic compounds and two reference materials. COD recoveries obtained with MW and ultrasound-assisted digestion for five real wastewater samples were ranged between 86-97% and 68-91%, respectively, of the values obtained with the classical method (open reflux) used as reference, with relative standard deviation lower than 4% in most cases. Thus, the Mn(III) microwave-assisted digestion method seems to be an interesting and promising alternative to conventional COD digestion methods since it is faster and more environmentally friendly than the ones used for the same purpose.

  14. Morphological stability of the atomically clean surface of silicon (100) crystals after microwave plasma-chemical processing

    SciTech Connect

    Yafarov, R. K. Shanygin, V. Ya.

    2016-01-15

    The morphological stability of atomically clean silicon (100) surface after low-energy microwave plasma-chemical etching in various plasma-forming media is studied. It is found that relaxation changes in the surface density and atomic bump heights after plasma processing in inert and chemically active media are multidirectional in character. After processing in a freon-14 medium, the free energy is minimized due to a decrease in the surface density of microbumps and an increase in their height. After argon-plasma processing, an insignificant increase in the bump density with a simultaneous decrease in bump heights is observed. The physicochemical processes causing these changes are considered.

  15. The Molecular Structure of Phenetole Studied by Microwave Spectroscopy and Quantum Chemical Calculations

    NASA Astrophysics Data System (ADS)

    Ferres, Lynn; Stahl, Wolfgang; Nguyen, Ha Vinh Lam

    2016-06-01

    A pulsed molecular beam Fourier transform microwave spectrometer operating in the frequency range 2 - 26.5 GHz was used to measure the spectrum of phenetole (ethyl phenyl ether or ethoxybenzene, C6H5OC2H5). The conformational landscape is completely determined by the orientations of the phenyl ring and the ethyl group. A two-dimensional potential energy surface was calculated at the MP2/6-311++G(d,p) level of theory. Two conformers were found: The trans conformer has a Cs symmetry, and the gauche conformer has the ethyl group tilted out of the phenyl plane by about 70°. Totally 186 rotational transitions were assigned to the more stable planar trans conformer, and fitted using a semi-rigid rotor model to measurement accuracy of 2 kHz. Highly accurate rotational and centrifugal distortion constants were determined. Several method and basis set combinations were applied to check for convergence and to compare with the experimentally deduced molecular parameters. The inertial defect of the observed conformer Δc = (Ic - Ia - Ib) = -6.718 uÅ2 confirms that the heavy atom skeleton is planar with two pairs of hydrogen atoms out of plane. All lines in the spectrum could be assigned to the trans conformer, which confirms that the gauche conformer cannot be observed under our measurement conditions. In agreement with the rather high torsional barrier of the methyl group (V3 = 1168 wn) calculated by quantum chemical methods, all assigned lines appeared sharp and no signs of splittings were observed for the methyl internal rotation.

  16. Synthesis and characterization of nano ZnO rods via microwave assisted chemical precipitation method

    SciTech Connect

    Uma Sangari, N.; Chitra Devi, S.

    2013-01-15

    A microwave assisted chemical precipitation method has been employed for the synthesis of nano zinc oxide rods by reacting zinc nitrate and potassium hydroxide. The amount of potassium hydroxide was adjusted for three different pHs to achieve ZnO nano rods with varying aspect ratio. The mechanism of growth of nano rods is explained briefly. The average crystallite size of the as synthesized samples was analyzed by means of powder XRD pattern and estimated to vary from 25.6 nm to 43.1 nm. The existence of rods was confirmed using scanning electron microscopy (SEM). The samples were also analyzed using FT-IR. The optical properties of the samples were also studied by means of UV-visible spectra and Room Temperature Photo Luminescence studies. The band gap of the samples was determined from the DRS spectrum. A strong near band emission peaks due to surface defects are observed in the PL spectrum. - Graphical abstract: At the solution pH of 11 and 9, tetrapod-like and flower-like ZnO nano rods were formed along with separated rods respectively due to the formation of activated nuclei of different sizes. Highlights: Black-Right-Pointing-Pointer Increase in alkalinity of the precursor solution results in longer rods. Black-Right-Pointing-Pointer Beyond a saturation limit, the excess of added OH{sup -} ions inhibited the growth of rods. Black-Right-Pointing-Pointer Keeping all parameters the same, the alkalinity can only modify the aspect ratio of the rods and not their morphology.

  17. Microwave-assisted chemical insertion: a rapid technique for screening cathodes for Mg-ion batteries

    SciTech Connect

    Kaveevivitchai, Watchareeya; Huq, Ashfia; Manthiram, Arumugam

    2016-12-19

    We report an ultrafast microwave-assisted solvothermal method for chemical insertion of Mg2+ ions into host materials using magnesium acetate [Mg(CH3COO)2] as a metal-ion source and diethylene glycol (DEG) as a reducing agent. For instance, up to 3 Mg ions per formula unit of a microporous host framework Mo2.5+yVO9+z could be inserted in as little as 30 min at 170–195 °C in air. This process is superior to the traditional method which involves the use of organometallic reagents, such as di-n-butylmagnesium [(C4H9)2Mg] and magnesium bis(2,6-di-tert-butylphenoxide) [Mg-(O-2,6-But2C6H3)2], and requires an inert atmosphere with extremely long reaction times. Considering the lack of robust electrolytes for Mg-ion batteries, this facile approach can be readily used as a rapid screening technique to identify potential Mg-ion electrode hosts without the necessity of fabricating electrodes and assembling electrochemical cells. Due to the mild reaction conditions, the overall structure and morphology of the Mg-ion inserted products are maintained and the compounds can be used successfully as a cathode in Mg-ion batteries. The combined synchrotron X-ray and neutron diffraction Rietveld analysis reveals the structure of the Mg-inserted compounds and gives an insight into the interactions between the Mg ions and the open-tunnel host framework.

  18. Remote operation of microwave systems for solids content analysis and chemical dissolution in highly radioactive environments

    SciTech Connect

    Sturcken, E.F.; Floyd, T.S.; Manchester, D.P.

    1986-10-01

    Microwave systems provide quick and easy determination of solids content of samples in high-level radioactive cells. In addition, dissolution of samples is much faster when employing microwave techniques. These are great advantages because work in cells,using master-slave manipulators through leaded glass walls, is normally slower by an order of magnitude than direct contact methods. This paper describes the modifiction of a moisture/solids analyzer microwave system and a drying/digestion microwave system for remote operation in radiation environments. The moisture/solids analyzer has operated satisfactorily for over a year in a gamma radiation field of 1000 roentgens per hour and the drying/digestion system is ready for installation in a cell.

  19. Sintering Behavior of Metal Powders Involving Microwave-Enhanced Chemical Reaction

    NASA Astrophysics Data System (ADS)

    Takayama, Sadatsugu; Saito, Yasushi; Sato, Motoyasu; Nagasaka, Takuya; Muroga, Takeo; Ninomiya, Yoshihiko

    2006-03-01

    Copper powder compacts were sintered by microwave radiation in air. In this procedure, the samples were sintered by microwave in air without using any special atmosphere, only by protecting them in a container filled with ceramic powder. The enhancement of the deoxidation reaction by the microwave was observed. The samples were analyzed by using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analysis. The samples were deoxidized on the surface and were well sintered to the edge from the inside throughout the entire cross section. The tensile strength of the copper samples sintered by the microwave in air was higher than that found in conventional sintering in N2 gas. No other differences were noticed between the samples sintered by the microwave under the air-rich conditions and in the conventional furnace in H2+N2 gas. The microwave-sintered copper samples were of good quality; for example, the tensile strength measured throughout the cross section was the same as that for the samples sintered in H2+N2 gas by the conventional method.

  20. A new type of power energy for accelerating chemical reactions: the nature of a microwave-driving force for accelerating chemical reactions.

    PubMed

    Zhou, Jicheng; Xu, Wentao; You, Zhimin; Wang, Zhe; Luo, Yushang; Gao, Lingfei; Yin, Cheng; Peng, Renjie; Lan, Lixin

    2016-04-27

    The use of microwave (MW) irradiation to increase the rate of chemical reactions has attracted much attention recently in nearly all fields of chemistry due to substantial enhancements in reaction rates. However, the intrinsic nature of the effects of MW irradiation on chemical reactions remains unclear. Herein, the highly effective conversion of NO and decomposition of H2S via MW catalysis were investigated. The temperature was decreased by several hundred degrees centigrade. Moreover, the apparent activation energy (Ea') decreased substantially under MW irradiation. Importantly, for the first time, a model of the interactions between microwave electromagnetic waves and molecules is proposed to elucidate the intrinsic reason for the reduction in the Ea' under MW irradiation, and a formula for the quantitative estimation of the decrease in the Ea' was determined. MW irradiation energy was partially transformed to reduce the Ea', and MW irradiation is a new type of power energy for speeding up chemical reactions. The effect of MW irradiation on chemical reactions was determined. Our findings challenge both the classical view of MW irradiation as only a heating method and the controversial MW non-thermal effect and open a promising avenue for the development of novel MW catalytic reaction technology.

  1. A new type of power energy for accelerating chemical reactions: the nature of a microwave-driving force for accelerating chemical reactions

    NASA Astrophysics Data System (ADS)

    Zhou, Jicheng; Xu, Wentao; You, Zhimin; Wang, Zhe; Luo, Yushang; Gao, Lingfei; Yin, Cheng; Peng, Renjie; Lan, Lixin

    2016-04-01

    The use of microwave (MW) irradiation to increase the rate of chemical reactions has attracted much attention recently in nearly all fields of chemistry due to substantial enhancements in reaction rates. However, the intrinsic nature of the effects of MW irradiation on chemical reactions remains unclear. Herein, the highly effective conversion of NO and decomposition of H2S via MW catalysis were investigated. The temperature was decreased by several hundred degrees centigrade. Moreover, the apparent activation energy (Ea’) decreased substantially under MW irradiation. Importantly, for the first time, a model of the interactions between microwave electromagnetic waves and molecules is proposed to elucidate the intrinsic reason for the reduction in the Ea’ under MW irradiation, and a formula for the quantitative estimation of the decrease in the Ea’ was determined. MW irradiation energy was partially transformed to reduce the Ea’, and MW irradiation is a new type of power energy for speeding up chemical reactions. The effect of MW irradiation on chemical reactions was determined. Our findings challenge both the classical view of MW irradiation as only a heating method and the controversial MW non-thermal effect and open a promising avenue for the development of novel MW catalytic reaction technology.

  2. A new type of power energy for accelerating chemical reactions: the nature of a microwave-driving force for accelerating chemical reactions

    PubMed Central

    Zhou, Jicheng; Xu, Wentao; You, Zhimin; Wang, Zhe; Luo, Yushang; Gao, Lingfei; Yin, Cheng; Peng, Renjie; Lan, Lixin

    2016-01-01

    The use of microwave (MW) irradiation to increase the rate of chemical reactions has attracted much attention recently in nearly all fields of chemistry due to substantial enhancements in reaction rates. However, the intrinsic nature of the effects of MW irradiation on chemical reactions remains unclear. Herein, the highly effective conversion of NO and decomposition of H2S via MW catalysis were investigated. The temperature was decreased by several hundred degrees centigrade. Moreover, the apparent activation energy (Ea’) decreased substantially under MW irradiation. Importantly, for the first time, a model of the interactions between microwave electromagnetic waves and molecules is proposed to elucidate the intrinsic reason for the reduction in the Ea’ under MW irradiation, and a formula for the quantitative estimation of the decrease in the Ea’ was determined. MW irradiation energy was partially transformed to reduce the Ea’, and MW irradiation is a new type of power energy for speeding up chemical reactions. The effect of MW irradiation on chemical reactions was determined. Our findings challenge both the classical view of MW irradiation as only a heating method and the controversial MW non-thermal effect and open a promising avenue for the development of novel MW catalytic reaction technology. PMID:27118640

  3. Rheological, Chemical and Physical Characteristics of Golden Berry (Physalis peruviana L.) after Convective and Microwave Drying.

    PubMed

    Nawirska-Olszańska, Agnieszka; Stępień, Bogdan; Biesiada, Anita; Kolniak-Ostek, Joanna; Oziembłowski, Maciej

    2017-07-29

    Studies on methods for fixing foods (with a slight loss of bioactive compounds) and obtaining attractive products are important with respect to current technology. The drying process allows for a product with highly bioactive properties. Drying of Physalis fruit was carried out in a conventional manner, and in a microwave under reduced pressure at 120 W and 480 W. After drying, the fruits were subjected to strength and rheological tests. Water activity, content of carotenoids and polyphenols and antioxidant activity as well as colour were also examined. The study showed that Physalis is a difficult material for drying. The best results were obtained using microwave drying at a power of 480 W. Physalis fruit microwave-dried by this method is characterized by higher resistance to compression than the fruit dried by convection. Dried fruit obtained in this way was characterized by higher contents of bioactive compounds, better antioxidant properties, and at the same time the lowest water activity.

  4. Rheological, Chemical and Physical Characteristics of Golden Berry (Physalis peruviana L.) after Convective and Microwave Drying

    PubMed Central

    Nawirska-Olszańska, Agnieszka; Stępień, Bogdan; Biesiada, Anita; Kolniak-Ostek, Joanna; Oziembłowski, Maciej

    2017-01-01

    Studies on methods for fixing foods (with a slight loss of bioactive compounds) and obtaining attractive products are important with respect to current technology. The drying process allows for a product with highly bioactive properties. Drying of Physalis fruit was carried out in a conventional manner, and in a microwave under reduced pressure at 120 W and 480 W. After drying, the fruits were subjected to strength and rheological tests. Water activity, content of carotenoids and polyphenols and antioxidant activity as well as colour were also examined. The study showed that Physalis is a difficult material for drying. The best results were obtained using microwave drying at a power of 480 W. Physalis fruit microwave-dried by this method is characterized by higher resistance to compression than the fruit dried by convection. Dried fruit obtained in this way was characterized by higher contents of bioactive compounds, better antioxidant properties, and at the same time the lowest water activity. PMID:28758918

  5. Diamond thin films grown by microwave plasma assisted chemical vapor deposition

    SciTech Connect

    Leksono, M.

    1991-09-05

    Undoped and boron doped diamond thin films have been successfully grown by microwave plasma chemical vapor deposition from CH{sub 4}, H{sub 2}, and B{sub 2}H{sub 6}. The films were characterized using x- ray diffraction techniques, Raman and infrared spectroscopies, scanning electron microscopy, secondary ion mass spectrometry, and various electrical measurements. The deposition rates of the diamond films were found to increase with the CH{sub 4} concentration, substrate temperature, and/or pressure, and at 1.0% methane, 900{degrees}C, and 35 Torr, the value was measured to be 0.87 {mu}m/hour. The deposition rate for boron doped diamond films, decreases as the diborane concentration increases. The morphologies of the undoped diamond films are strongly related to the deposition parameters. As the temperature increases from 840 to 925 C, the film morphology changes from cubo-octahedron to cubic structures, while as the CH{sub 4} concentration increases from 0.5 to 1.0%, the morphology changes from triangular (111) faces with a weak preferred orientation to square (100) faces. At 2.0% Ch{sub 4} or higher the films become microcrystalline with cauliflower structures. Scanning electron microscopy analyses also demonstrate that selective deposition of undoped diamond films has been successfully achieved using a lift-off process with a resolution of at least 2 {mu}m. The x-ray diffraction and Raman spectra demonstrate that high quality diamond films have been achieved. The concentration of the nondiamond phases in the films grown at 1.0% CH{sub 4} can be estimated from the Raman spectra to be at less than 0.2% and increases with the CH{sub 4} concentration. The Raman spectra of the boron doped diamond films also indicate that the presence of boron tends to suppress the nondiamond phases in the films. Infrared spectra of the undoped diamond films show very weak CH stretch peaks which suggest that the hydrogen concentration is very low.

  6. Combustion Dynamics of Plasma-Enhanced Premixed and Nonpremixed Flames

    DTIC Science & Technology

    2010-12-01

    flame. The anchor of the nonpremixed flame can be seen at the base of the plasma plume. Both the size and luminosity of the plume increase as a...K higher than that in nonpremixed flames for the same fuel flow rates. For premixed flames, the visible flame luminosity and plasma volume increase...vol. 34, no. 6, pp. 2545–2551, Dec. 2006. [10] W. Kim, M. Godfrey Mungal, and M. A. Cappelli, “The role of in situ reforming in plasma enhanced ultra

  7. "GREENER" CHEMICAL SYNTHETIC PROCESSES USING ENZYMATIC, MECHANOCHEMICAL MIXING, OR MICROWAVE AND ULTRASOUND IRRADIATION

    EPA Science Inventory

    Several newer strategies, such as solvent-free (dry media), solid-supported with and without microwave (MW) irradiation, and mechanochemical mixing (grinding); and the use of room temperature ionic liquids, supercritical carbon dioxide, and water as reaction media that can be com...

  8. 'GREENER' CHEMICAL SYNTHESES USING MICROWAVES UNDER SOLVENT-FREE CONDITIONS OR AQUEOUS MEDIA

    EPA Science Inventory

    A solvent-free approach that involves microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of recyclable mineral supports such as alumina, silica, clay, or 'doped' surfaces is presented which is applicable to a wide range of cleavage, condensation, cycl...

  9. 'GREENER' CHEMICAL SYNTHESES USING MICROWAVES UNDER SOLVENT-FREE CONDITIONS OR AQUEOUS MEDIA

    EPA Science Inventory

    A solvent-free approach that involves microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of recyclable mineral supports such as alumina, silica, clay, or 'doped' surfaces is presented which is applicable to a wide range of cleavage, condensation, cycl...

  10. ‘Greener’ Chemical Syntheses Using Mechanochemical Mixing or Microwave and Ultrasound Irradiation

    EPA Science Inventory

    Various emerging ‘greener’ strategic pathways researched primarily in the author’s own laboratory are summarized. They include solvent-free mechanochemical methods and microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of less-expensive and recyclabl...

  11. ‘Greener’ Chemical Syntheses Using Mechanochemical Mixing or Microwave and Ultrasound Irradiation

    EPA Science Inventory

    Various emerging ‘greener’ strategic pathways researched primarily in the author’s own laboratory are summarized. They include solvent-free mechanochemical methods and microwave (MW) exposure of neat reactants (undiluted) catalyzed by the surfaces of less-expensive and recyclabl...

  12. "GREENER" CHEMICAL SYNTHETIC PROCESSES USING ENZYMATIC, MECHANOCHEMICAL MIXING, OR MICROWAVE AND ULTRASOUND IRRADIATION

    EPA Science Inventory

    Several newer strategies, such as solvent-free (dry media), solid-supported with and without microwave (MW) irradiation, and mechanochemical mixing (grinding); and the use of room temperature ionic liquids, supercritical carbon dioxide, and water as reaction media that can be com...

  13. Extraction and separation of nickel and cobalt from saprolite laterite ore by microwave-assisted hydrothermal leaching and chemical deposition

    NASA Astrophysics Data System (ADS)

    Zhao, Yan; Gao, Jian-ming; Yue, Yi; Peng, Ben; Que, Zai-qing; Guo, Min; Zhang, Mei

    2013-07-01

    Extraction and separation of nickel and cobalt from saprolite laterite ore were studied by using a method of microwave-assisted hydrothermal leaching and chemical deposition. The effects of leaching temperature and time on the extraction efficiencies of Ni2+ and Co2+ were investigated in detail under microwave conditions. It is shown that the extraction efficiencies of Ni2+ and Co2+ from the ore pre-roasted at 300°C for 5 h were 89.19% and 61.89% when the leaching temperature and time were about 70°C and 60 min, respectively. For the separation process of Ni and Co, the separation of main chemical components was performed by adjusting the pH values of sulfuric leaching solutions using a NaOH solution based on the different pH values of precipitation for metal hydroxides. The final separation efficiencies of Ni and Co were 77.29% and 65.87%, respectively. Furthermore, the separation efficiencies of Fe of 95.36% and Mg of 92.2% were also achieved at the same time.

  14. Fabrication and morphology control of BaWO{sub 4} thin films by microwave assisted chemical bath deposition

    SciTech Connect

    Wang Rui; Liu Chen; Zeng Jia; Li KunWei; Wang Hao

    2009-04-15

    Highly crystallized barium tungstate (BaWO{sub 4}) thin films with dumbbell-like, kernel-like, bowknot-like and cauliflower-like microstructure were synthesized from an aqueous solution containing barium nitrate, ethylenediamine tetraacetate acid disodium and sodium tungstate, via mild microwave assisted chemical bath deposition process. The resulting BaWO{sub 4} films with different morphologies were characterized by X-ray diffraction spectrum, scanning electron microscope, Raman and photoluminescence spectra. The results indicate that the morphologies of final products significantly depend on the reaction conditions including the reaction time, the initial concentration of precursor reagent and the physicochemical characteristics of the substrates. Furthermore, the oriented aggregation mechanism is proposed as a possible formation mechanism of the films with specific morphologies. - Graphical abstract: Highly crystallized BaWO{sub 4} thin films with controllable morphologies have been synthesized via mild microwave assisted chemical bath deposition. The oriented aggregation mechanism has been proposed as the possible formation mechanism of specific films.

  15. Comparative Evaluation of Dimensional Accuracy of Elastomeric Impression Materials when Treated with Autoclave, Microwave, and Chemical Disinfection

    PubMed Central

    Kamble, Suresh S; Khandeparker, Rakshit Vijay; Somasundaram, P; Raghav, Shweta; Babaji, Rashmi P; Varghese, T Joju

    2015-01-01

    Background: Impression materials during impression procedure often get infected with various infectious diseases. Hence, disinfection of impression materials with various disinfectants is advised to protect the dental team. Disinfection can alter the dimensional accuracy of impression materials. The present study was aimed to evaluate the dimensional accuracy of elastomeric impression materials when treated with different disinfectants; autoclave, chemical, and microwave method. Materials and Methods: The impression materials used for the study were, dentsply aquasil (addition silicone polyvinylsiloxane syringe and putty), zetaplus (condensation silicone putty and light body), and impregum penta soft (polyether). All impressions were made according to manufacturer’s instructions. Dimensional changes were measured before and after different disinfection procedures. Result: Dentsply aquasil showed smallest dimensional change (−0.0046%) and impregum penta soft highest linear dimensional changes (−0.026%). All the tested elastomeric impression materials showed some degree of dimensional changes. Conclusion: The present study showed that all the disinfection procedures produce minor dimensional changes of impression material. However, it was within American Dental Association specification. Hence, steam autoclaving and microwave method can be used as an alternative method to chemical sterilization as an effective method. PMID:26435611

  16. Comparative Evaluation of Dimensional Accuracy of Elastomeric Impression Materials when Treated with Autoclave, Microwave, and Chemical Disinfection.

    PubMed

    Kamble, Suresh S; Khandeparker, Rakshit Vijay; Somasundaram, P; Raghav, Shweta; Babaji, Rashmi P; Varghese, T Joju

    2015-09-01

    Impression materials during impression procedure often get infected with various infectious diseases. Hence, disinfection of impression materials with various disinfectants is advised to protect the dental team. Disinfection can alter the dimensional accuracy of impression materials. The present study was aimed to evaluate the dimensional accuracy of elastomeric impression materials when treated with different disinfectants; autoclave, chemical, and microwave method. The impression materials used for the study were, dentsply aquasil (addition silicone polyvinylsiloxane syringe and putty), zetaplus (condensation silicone putty and light body), and impregum penta soft (polyether). All impressions were made according to manufacturer's instructions. Dimensional changes were measured before and after different disinfection procedures. Dentsply aquasil showed smallest dimensional change (-0.0046%) and impregum penta soft highest linear dimensional changes (-0.026%). All the tested elastomeric impression materials showed some degree of dimensional changes. The present study showed that all the disinfection procedures produce minor dimensional changes of impression material. However, it was within American Dental Association specification. Hence, steam autoclaving and microwave method can be used as an alternative method to chemical sterilization as an effective method.

  17. Substrate temperature effect on the growth of carbon nanowalls synthesized via microwave PECVD

    SciTech Connect

    Kim, Sung Yun; Choi, Won Seok; Lee, Jae-Hyeoung; Hong, Byungyou

    2014-10-15

    Highlights: • Well grown carbon nanowalls (CNWs) were obtained by using a microwave plasma enhanced chemical vapor deposition (PECVD) with methane and hydrogen gases on Si substrates. • CNWs were grown at the growth temperature of 850 °C showed the highest contact angle. • Raman analysis showed higher I{sub D}/I{sub G} value that the CNWs were grown at more than 850 °C growth temperature. - Abstract: A carbon nanowall (CNW) is a carbon-based nanomaterial that is constructed with vertical-structure graphenes. Thus, it effectively increases the reaction surface of electrodes. In this study, the substrate temperature effect on the growth of CNWs was investigated via microwave plasma enhanced chemical vapor deposition (PECVD) with methane (CH{sub 4}) and hydrogen (H{sub 2}) gases on silicon substrates. To find the growth mechanism of a CNW, its growth temperature was changed from 700 °C to 950 °C. The vertical and surface conditions of the grown CNWs according to the growth temperature were characterized via field emission scanning electron microscopy (FE-SEM). The energy-dispersive spectroscopy (EDS) measurements showed that the CNWs were composed solely of carbon.

  18. Automated microwave double resonance spectroscopy: A tool to identify and characterize chemical compounds.

    PubMed

    Martin-Drumel, Marie-Aline; McCarthy, Michael C; Patterson, David; McGuire, Brett A; Crabtree, Kyle N

    2016-03-28

    Owing to its unparalleled structural specificity, rotational spectroscopy is a powerful technique to unambiguously identify and characterize volatile, polar molecules. We present here a new experimental approach, automated microwave double resonance (AMDOR) spectroscopy, to rapidly determine the rotational constants of these compounds without a priori knowledge of elemental composition or molecular structure. This task is achieved by rapidly acquiring the classical (frequency vs. intensity) broadband spectrum of a molecule using chirped-pulse Fourier transform microwave (FTMW) spectroscopy and subsequently analyzing it in near real-time using complementary cavity FTMW detection and double resonance. AMDOR measurements provide a unique "barcode" for each compound from which rotational constants can be extracted. To illustrate the power of this approach, AMDOR spectra of three aroma compounds - trans-cinnamaldehyde, α-, and β-ionone - have been recorded and analyzed. The prospects to extend this approach to mixture characterization and purity assessment are described.

  19. Automated microwave double resonance spectroscopy: A tool to identify and characterize chemical compounds

    NASA Astrophysics Data System (ADS)

    Martin-Drumel, Marie-Aline; McCarthy, Michael C.; Patterson, David; McGuire, Brett A.; Crabtree, Kyle N.

    2016-03-01

    Owing to its unparalleled structural specificity, rotational spectroscopy is a powerful technique to unambiguously identify and characterize volatile, polar molecules. We present here a new experimental approach, automated microwave double resonance (AMDOR) spectroscopy, to rapidly determine the rotational constants of these compounds without a priori knowledge of elemental composition or molecular structure. This task is achieved by rapidly acquiring the classical (frequency vs. intensity) broadband spectrum of a molecule using chirped-pulse Fourier transform microwave (FTMW) spectroscopy and subsequently analyzing it in near real-time using complementary cavity FTMW detection and double resonance. AMDOR measurements provide a unique "barcode" for each compound from which rotational constants can be extracted. To illustrate the power of this approach, AMDOR spectra of three aroma compounds — trans-cinnamaldehyde, α-, and β-ionone — have been recorded and analyzed. The prospects to extend this approach to mixture characterization and purity assessment are described.

  20. Automated Microwave Double Resonance Spectroscopy: a Tool to Identify and Characterize Chemical Compounds

    NASA Astrophysics Data System (ADS)

    Martin-Drumel, Marie-Aline; McCarthy, Michael C.; Patterson, David; McGuire, Brett A.; Crabtree, Kyle N.

    2016-06-01

    Owing to its unparalleled structural specificity, rotational spectroscopy is a powerful technique to unambiguously identify and characterize volatile, polar molecules. We present here a new experimental approach, automated microwave double resonance (AMDOR) spectroscopy, to rapidly determine the rotational constants of these compounds without any a priori knowledge of elemental composition or molecular structure. This task is achieved by rapidly acquiring the classical (frequency vs. intensity) broadband spectrum of a molecule using chirped-pulse Fourier transform microwave (FTMW) spectroscopy, and subsequently analyzing it in near-real time using complementary cavity FTMW detection and double resonance. AMDOR measurements provide a unique ``barcode'' for each compound from which rotational constants can be extracted. To illustrate the power of this approach, AMDOR spectra of three aroma compounds --- trans-cinnamaldehyde, α- and β-ionone --- have been recorded and analyzed. The prospects to extend this approach to mixture characterization and purity assessment are described.

  1. Automated Microwave Double Resonance Spectroscopy: a Tool to Identify and Characterize Chemical Compounds

    NASA Astrophysics Data System (ADS)

    Martin-Drumel, Marie-Aline; McCarthy, Michael C.; Patterson, David; McGuire, Brett A.; Crabtree, Kyle N.

    2017-06-01

    Owing to its unparalleled structural specificity, rotational spectroscopy is a powerful technique to unambiguously identify and characterize polar molecules. We present here an experimental approach, automated microwave double resonance (AMDOR) spectroscopy, that allows to rapidly determine the rotational constants of such compounds without any a priori knowledge of elemental composition or molecular structure. This task is achieved by acquiring the classical (frequency vs. intensity) broadband spectrum of a molecule using chirped-pulse Fourier transform microwave (FTMW) spectroscopy, and subsequently analyzing it in near-real time using complementary cavity FTMW detection and double resonance. AMDOR measurements provide a unique ``barcode'' for each compound from which rotational constants can be extracted. Results obtained on the characterization of individual compounds and mixtures will be described.

  2. Radio-frequency oxygen-plasma-enhanced pulsed laser deposition of IGZO films

    NASA Astrophysics Data System (ADS)

    Chou, Chia-Man; Lai, Chih-Chang; Chang, Chih-Wei; Wen, Kai-Shin; Hsiao, Vincent K. S.

    2017-07-01

    We demonstrate the crystalline structures, optical transmittance, surface and cross-sectional morphologies, chemical compositions, and electrical properties of indium gallium zinc oxide (IGZO)-based thin films deposited on glass and silicon substrates through pulsed laser deposition (PLD) incorporated with radio-frequency (r.f.)-generated oxygen plasma. The plasma-enhanced pulsed laser deposition (PEPLD)-based IGZO thin films exhibited a c-axis-aligned crystalline (CAAC) structure, which was attributed to the increase in Zn-O under high oxygen vapor pressure (150 mTorr). High oxygen vapor pressure (150 mTorr) and low r.f. power (10 W) are the optimal deposition conditions for fabricating IGZO thin films with improved electrical properties.

  3. Plasma-Enhanced Pulsed Laser Deposition of Wide Bandgap Nitrides for Space Power Applications

    NASA Technical Reports Server (NTRS)

    Triplett, G. E., Jr.; Durbin, S. M.

    2004-01-01

    The need for a reliable, inexpensive technology for small-scale space power applications where photovoltaic or chemical battery approaches are not feasible has prompted renewed interest in radioisotope-based energy conversion devices. Although a number of devices have been developed using a variety of semiconductors, the single most limiting factor remains the overall lifetime of the radioisotope battery. Recent advances in growth techniques for ultra-wide bandgap III-nitride semiconductors provide the means to explore a new group of materials with the promise of significant radiation resistance. Additional benefits resulting from the use of ultra-wide bandgap materials include a reduction in leakage current and higher operating voltage without a loss of energy transfer efficiency. This paper describes the development of a novel plasma-enhanced pulsed laser deposition system for the growth of cubic boron nitride semiconducting thin films, which will be used to construct pn junction devices for alphavoltaic applications.

  4. Effects of catalyst film thickness on plasma-enhanced carbon nanotube growth

    SciTech Connect

    Hofmann, S.; Cantoro, M.; Kleinsorge, B.; Casiraghi, C.; Parvez, A.; Robertson, J.; Ducati, C.

    2005-08-01

    A systematic study is presented of the influence of catalyst film thickness on carbon nanostructures grown by plasma-enhanced chemical-vapor deposition from acetylene and ammonia mixtures. We show that reducing the Fe/Co catalyst film thickness below 3 nm causes a transition from larger diameter (>40 nm), bamboolike carbon nanofibers to small diameter ({approx}5 nm) multiwalled nanotubes with two to five walls. This is accompanied by a more than 50 times faster growth rate and a faster catalyst poisoning. Thin Ni catalyst films only trigger such a growth transition when pretreated with an ammonia plasma. We observe a limited correlation between this growth transition and the coarsening of the catalyst film before deposition. For a growth temperature of {<=}550 deg. C, all catalysts showed mainly a tip growth regime and a similar activity on untreated silicon, oxidized silicon, and silicon nitride support.

  5. Moisture barrier properties of thin organic-inorganic multilayers prepared by plasma-enhanced ALD and CVD in one reactor

    NASA Astrophysics Data System (ADS)

    Bülow, Tim; Gargouri, Hassan; Siebert, Mirko; Rudolph, Rolf; Johannes, Hans-Hermann; Kowalsky, Wolfgang

    2014-05-01

    A widely used application of the atomic layer deposition (ALD) and chemical vapour deposition (CVD) methods is the preparation of permeation barrier layers against water vapour. Especially in the field of organic electronics, these films are highly demanded as such devices are very sensitive to moisture and oxygen. In this work, multilayers of aluminium oxide (AlO x ) and plasma polymer (PP) were coated on polyethylene naphthalate substrates by plasma-enhanced ALD and plasma-enhanced CVD at 80℃ in the same reactor, respectively. As precursor, trimethylaluminium was used together with oxygen radicals in order to prepare AlO x , and benzene served as precursor to deposit the PP. This hybrid structure allows the decoupling of defects between the single AlO x layers and extends the permeation path for water molecules towards the entire barrier film. Furthermore, the combination of two plasma techniques in a single reactor system enables short process times without vacuum breaks. Single aluminium oxide films by plasma-enhanced ALD were compared to thermally grown layers and showed a significantly better barrier performance. The water vapour transmission rate (WVTR) was determined by means of electrical calcium tests. For a multilayer with 3.5 dyads of 25-nm AlO x and 125-nm PP, a WVTR of 1.2 × 10 -3 g m -2 d -1 at 60℃ and 90% relative humidity could be observed.

  6. Plasma Enhanced Growth of Carbon Nanotubes For Ultrasensitive Biosensors

    NASA Technical Reports Server (NTRS)

    Cassell, Alan M.; Li, J.; Ye, Q.; Koehne, J.; Chen, H.; Meyyappan, M.

    2004-01-01

    The multitude of considerations facing nanostructure growth and integration lends itself to combinatorial optimization approaches. Rapid optimization becomes even more important with wafer-scale growth and integration processes. Here we discuss methodology for developing plasma enhanced CVD growth techniques for achieving individual, vertically aligned carbon nanostructures that show excellent properties as ultrasensitive electrodes for nucleic acid detection. We utilize high throughput strategies for optimizing the upstream and downstream processing and integration of carbon nanotube electrodes as functional elements in various device types. An overview of ultrasensitive carbon nanotube based sensor arrays for electrochemical biosensing applications and the high throughput methodology utilized to combine novel electrode technology with conventional MEMS processing will be presented.

  7. Plasma Enhanced Growth of Carbon Nanotubes For Ultrasensitive Biosensors

    NASA Technical Reports Server (NTRS)

    Cassell, Alan M.; Meyyappan, M.

    2004-01-01

    The multitude of considerations facing nanostructure growth and integration lends itself to combinatorial optimization approaches. Rapid optimization becomes even more important with wafer-scale growth and integration processes. Here we discuss methodology for developing plasma enhanced CVD growth techniques for achieving individual, vertically aligned carbon nanostructures that show excellent properties as ultrasensitive electrodes for nucleic acid detection. We utilize high throughput strategies for optimizing the upstream and downstream processing and integration of carbon nanotube electrodes as functional elements in various device types. An overview of ultrasensitive carbon nanotube based sensor arrays for electrochemical bio-sensing applications and the high throughput methodology utilized to combine novel electrode technology with conventional MEMS processing will be presented.

  8. Plasma Enhanced Growth of Carbon Nanotubes For Ultrasensitive Biosensors

    NASA Technical Reports Server (NTRS)

    Cassell, Alan M.; Li, J.; Ye, Q.; Koehne, J.; Chen, H.; Meyyappan, M.

    2004-01-01

    The multitude of considerations facing nanostructure growth and integration lends itself to combinatorial optimization approaches. Rapid optimization becomes even more important with wafer-scale growth and integration processes. Here we discuss methodology for developing plasma enhanced CVD growth techniques for achieving individual, vertically aligned carbon nanostructures that show excellent properties as ultrasensitive electrodes for nucleic acid detection. We utilize high throughput strategies for optimizing the upstream and downstream processing and integration of carbon nanotube electrodes as functional elements in various device types. An overview of ultrasensitive carbon nanotube based sensor arrays for electrochemical biosensing applications and the high throughput methodology utilized to combine novel electrode technology with conventional MEMS processing will be presented.

  9. Plasma Enhanced Growth of Carbon Nanotubes For Ultrasensitive Biosensors

    NASA Technical Reports Server (NTRS)

    Cassell, Alan M.; Meyyappan, M.

    2004-01-01

    The multitude of considerations facing nanostructure growth and integration lends itself to combinatorial optimization approaches. Rapid optimization becomes even more important with wafer-scale growth and integration processes. Here we discuss methodology for developing plasma enhanced CVD growth techniques for achieving individual, vertically aligned carbon nanostructures that show excellent properties as ultrasensitive electrodes for nucleic acid detection. We utilize high throughput strategies for optimizing the upstream and downstream processing and integration of carbon nanotube electrodes as functional elements in various device types. An overview of ultrasensitive carbon nanotube based sensor arrays for electrochemical bio-sensing applications and the high throughput methodology utilized to combine novel electrode technology with conventional MEMS processing will be presented.

  10. Influence of microwave vacuum drying on glass transition temperature, gelatinization temperature, physical and chemical qualities of lotus seeds.

    PubMed

    Zhao, Yingting; Jiang, Yajun; Zheng, Baodong; Zhuang, Weijing; Zheng, Yafeng; Tian, Yuting

    2017-08-01

    This study investigated the effects of microwave power density on effective moisture diffusion coefficient (Deff), glass transition temperature (Tg), gelatinization temperature (TP), physical and chemical qualities of lotus seeds during microwave vacuum drying. Deff increased by 42% and 127% at 15W/g and 20W/g, respectively, when compared with 10W/g. TP was negatively correlated with the relaxation times of T21 and T22, while Tg was negatively correlated with the relative areas A22. The rates of change of color were observed to be divided roughly into two periods, consisting of a rapid change caused by enzymatic browning and a slow change caused by non-enzymatic browning. An equation is provided to illustrate the relationship of k1 and k2 of Peleg's model depending on power density during rehydration kinetics. The samples at 20W/g exhibited the higher content of amino acid (540.19mg/100gd.b.) while lower starch (17.53g/100gd.b.). Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Antibacterial properties and chemical characterization of the essential oils from summer savory extracted by microwave-assisted hydrodistillation

    PubMed Central

    Rezvanpanah, Shila; Rezaei, Karamatollah; Golmakani, Mohammad-Taghi; Razavi, Seyyed Hadi

    2011-01-01

    Antibacterial properties and chemical characterization of the essential oils from summer savory (Satureja hortensis) extracted by microwave-assisted hydrodistillation (MAHD) were compared with those of the essential oils extracted using the traditional hydrodistillation (HD) method. While MAHD at 660 W required half as much time as HD needed, similar antibacterial efficacies were found from the essential oils obtained by the two extraction methods on two food pathogens (Staphylococcus aureus, a gram positive bacterium, and Escherchia coli, a gram negative bacterium). Also, as it was the case with the essential oils extracted by HD, that of MAHD indicated greater influence on S. aureus than on E. coli. The compositions of the extracted essential oils were also studied using GC-MS analysis. The same components with negligible differences in their quantities were found in the extracted essential oils using the two methods outlined above. Overall, to reduce the extraction time, MAHD can be applied at higher microwave levels without any compromise in the antibacterial properties of the essential oils extracted. PMID:24031778

  12. Conformational analysis of tert-butyl acetate using a combination of microwave spectroscopy and quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Zhao, Yueyue; Mouhib, Halima; Li, Guohua; Kleiner, Isabelle; Stahl, Wolfgang

    2016-04-01

    tert-Butyl acetate was investigated using a combination of quantum chemical calculations and molecular beam Fourier transform microwave spectroscopy. The microwave spectrum was recorded in the frequency range from 8.00 to 15.75 GHz. Due to its rather rigid frame, the molecule possesses only two conformers: one of Cs symmetry and one of C1 symmetry that appears as a pair of enantiomers. The Cs conformer is the most abundant in the supersonic jet and according to ab initio calculations at the MP2/6-311++G(d, p) level of theory it is 46 kJ/mol lower in energy than the C1 conformer. Here, we report on the structure and dynamics of the most abundant conformer of tert-butyl acetate, for which a set of rotational and centrifugal distortion constants, as well as the barrier to internal rotation of the acetyl methyl group were determined with high accuracy. Splittings due to the internal rotation of the methyl group of up to 1.3 GHz were observed in the spectrum. Using the programs XIAM and BELGI-Cs, we were able to determine a barrier height of about 113 cm-1 and subsequently compare the molecular parameters obtained from these two codes.

  13. Microwave plasma assisted chemical vapor deposition of ultra-nanocrystalline diamond films

    NASA Astrophysics Data System (ADS)

    Huang, Wen-Shin

    Microwave plasma assisted ultra-nanocrystalline diamond film deposition was investigated using hydrogen deficient, carbon containing argon plasma chemistries with MSU-developed microwave plasma reactors. Ultra-nanocrystalline diamond film deposition on mechanically scratched silicon wafers was experimentally explored over the following input variables: (1) pressure: 60--240Torr, (2) total gas flow rate: 101--642 sccm, (3) input microwave power 732--1518W, (4) substrate temperature: 500°C--770°C, (5) deposition time: 2--48 hours, and (6) N2 impurities 5--2500 ppm. H2 concentrations were less than 9%, while CH 4 concentration was 0.17--1.85%. It was desired to grow films uniformly over 3″ diameter substrates and to minimize the grain size. Large, uniform, intense, and greenish-white discharges were sustained in contact with three inch silicon substrates over a 60--240 Torr pressure regime. At a given operating pressure, film uniformity was controlled by adjusting substrate holder geometry, substrate position, input microwave power, gas chemistries, and total gas flow rates. Film ultra-nanocrystallinity and smoothness required high purity deposition conditions. Uniform ultra-nanocrystalline films were synthesized in low leak-rate system with crystal sizes ranging from 3--30 nm. Films with 11--50 nm RMS roughness and respective thickness values of 1--23 mum were synthesized over 3″ wafers under a wide range of different deposition conditions. Film RMS roughness 7 nm was synthesized with thickness of 430 nm. Film uniformities of almost 100% were achieved over three inch silicon wafers. UV Raman and XRD characterization results indicated the presence of diamond in the synthesized films. Optical Emission Spectroscopy measurements showed that the discharge gas temperature was in excess of 2000 K. The synthesized films are uniformly smooth and the as grown ultra-nanocrystalline diamond can be used for a high frequency SAW device substrate material. IR measurements

  14. Growth of 4″ diameter polycrystalline diamond wafers with high thermal conductivity by 915 MHz microwave plasma chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    A, F. POPOVICH; V, G. RALCHENKO; V, K. BALLA; A, K. MALLIK; A, A. KHOMICH; A, P. BOLSHAKOV; D, N. SOVYK; E, E. ASHKINAZI; V, Yu YUROV

    2017-03-01

    Polycrystalline diamond (PCD) films 100 mm in diameter are grown by 915 MHz microwave plasma chemical vapor deposition (MPCVD) at different process parameters, and their thermal conductivity (TC) is evaluated by a laser flash technique (LFT) in the temperature range of 230-380 K. The phase purity and quality of the films are assessed by micro-Raman spectroscopy based on the diamond Raman peak width and the amorphous carbon (a-C) presence in the spectra. Decreasing and increasing dependencies for TC with temperature are found for high and low quality samples, respectively. TC, as high as 1950 ± 230 W m-1 K-1 at room temperature, is measured for the most perfect material. A linear correlation between the TC at room temperature and the fraction of the diamond component in the Raman spectrum for the films is established.

  15. Physi-chemical and sorption properties of biochars prepared from peanut shell using thermal pyrolysis and microwave irradiation.

    PubMed

    Chu, Gang; Zhao, Jing; Chen, Fangyuan; Dong, Xudong; Zhou, Dandan; Liang, Ni; Wu, Min; Pan, Bo; Steinberg, Christian E W

    2017-08-01

    Microwave irradiation (MW) is an effective technique in heating and pyrolysis. This study compared the properties of peanut shell-biochars produced using MW and muffle furnace (FN). At the same pyrolysis temperature, MW biochars preserved more biomass (as indicated by their higher yields and higher abundance of functional groups) and possessed larger surface areas due to the high abundance of micropores. MW biochars generally exhibited higher adsorption of carbamazepine (CBZ) and bisphenol A (BPA) than FN biochars. However, their surface area-normalized sorption was lower, suggesting that the inner pores may not be fully available to CBZ and BPA sorption. We observed significant free radical signals in both types of biochars. Although CBZ and BPA did not degrade in the biochar sorption systems, the potential role of stronger free radical signals in MW biochars for organic contaminant control may not be overlooked in studies with other chemicals. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Numerical analysis of a mixture of Ar/NH3 microwave plasma chemical vapor deposition reactor

    NASA Astrophysics Data System (ADS)

    Li, Zhi; Zhao, Zhen; Li, Xuehui

    2012-06-01

    A two-dimensional fluid model has been used to investigate the properties of plasma in Ar/NH3 microwave electron cyclotron resonance discharge at low pressure. The electromagnetic field model solved by the three-dimensional Simpson method is coupled to a fluid plasma model. The finite difference method was employed to discrete the governing equations. 40 species (neutrals, radicals, ions, and electrons) are consisted in the model. In total, 75 electron-neutral, 43 electron-ion, 167 neutral-neutral, 129 ion-neutral, 28 ion-ion, and 90 3-body reactions are used in the model. According to the simulation, the distribution of the densities of the considered plasma species has been showed and the mechanisms of their variations have been discussed. It is found that the main neutrals (Ar*, Ar**, NH3*, NH, H2, NH2, H, and N2) are present at high densities in Ar/NH3 microwave electron cyclotron resonance discharge when the mixing ratio of Ar/NH3 is 1:1 at 20 Pa. The density of NH is more than that of NH2 atom. And NH3+ are the most important ammonia ions. But the uniformity of the space distribution of NH3+ is lower than the other ammonia ions.

  17. CHEMICAL TRANSFORMATIONS USING NON-TRADITIONAL APPROACHES: MICROWAVE-ASSISTED GREENER SYNTHESES IN AQUEOUS MEDIA OR UNDER SOLVENT-FREE CONDITIONS

    EPA Science Inventory

    Microwave (MW) irradiation in conjunction with water as reaction media has proven to be a 'greener' chemical approach for expeditious N-alkylation reactions of amines and hydrazines wherein the reactions under mildly basic conditions afford tertiary amines and double N<...

  18. [Study on the microwave extraction and chemical constituents of the essential oil from Amomum tsao-ko in Jinping, Yunnan province].

    PubMed

    Yang, Lijuan; Zhang, Zheng; Li, Junfeng; Kong, Weiling; Lin, Jun

    2004-11-01

    Essential oil from Amomum tsao-ko collected in Jinping, Yunnan province was obtained by microwave extraction, common solvent extraction and vapor distillation, respectively. Chemical constituents were analyzed by GC-MS and their relative contents were determined by area-normalized method.

  19. Microwave-Assisted Extraction, Chemical Structures, and Chain Conformation of Polysaccharides from a Novel Cordyceps Sinensis Fungus UM01.

    PubMed

    Cheong, Kit-Leong; Wang, Lan-Ying; Wu, Ding-Tao; Hu, De-Jun; Zhao, Jing; Li, Shao-Ping

    2016-09-01

    Cordyceps sinensis is a well-known tonic food with broad medicinal properties. The aim of the present study was to investigate the optimization of microwave-assisted extraction (MAE) and characterize chemical structures and chain conformation of polysaccharides from a novel C. sinensis fungus UM01. Ion-exchange and gel filtration chromatography were used to purify the polysaccharides. The chemical structure of purified polysaccharide was determined through gas chromatography-mass spectrometry. Moreover, high performance size exclusion chromatography combined with refractive index detector and multiangle laser light scattering were conducted to analyze the molecular weight (Mw ) and chain conformation of purified polysaccharide. Based on the orthogonal design L9 , optimal MAE conditions could be obtained through 1300 W of microwave power, with a 5-min irradiation time at a solid to water ratio of 1:60, generating the highest extraction yield of 6.20%. Subsequently, the polysaccharide UM01-S1 was purified. The UM01-S1 is a glucan-type polysaccharide with a (1→4)-β-d-glucosyl backbone and branching points located at O-3 of Glcp with a terminal-d-Glcp. The Mw , radius of gyration (Rg ) and hydrodynamic radius (Rh ) of UM01-S1 were determined as 5.442 × 10(6)  Da, 21.8 and 20.2 nm, respectively. Using the polymer solution theory, the exponent (ν) value of the power law function was calculated as 0.38, and the shape factor (ρ = Rg /Rh ) was 1.079, indicating that UM01-S1 has a sphere-like conformation with a branched structure in an aqueous solution. These results provide fundamental information for the future application of polysaccharides from cultured C. sinensis in health and functional food area. © 2016 Institute of Food Technologists®

  20. MMS observations of strong plasma enhancements at the dawn terminator

    NASA Astrophysics Data System (ADS)

    Avanov, L. A.; Mackler, D. A.; Buzulukova, N.; Gershman, D. J.; Dorelli, J.; Giles, B. L.; Pollock, C.; Barrie, A.; Chandler, M. O.; Coffey, V. N.

    2016-12-01

    On March 7, 2016, the MMS constellation traveled from the nightside to the dayside of the inner magnetosphere. At the dawn terminator ( 6 am MLT) the four MMS spacecraft detected several significant plasma enhancements accompanied by strong plasma acceleration. The strongest event was captured by MMS in burst mode (30 ms for electron and 150 ms for ions). The number density abruptly increased from typical magnetospheric background values, 1 cm-3, up to 50-60 cm-3. The solar wind parameters corresponding to these enhancements are quite stable without any sharp changes. Specifically, the plasma dynamic pressure is steady close to nominal at 2.5-3 nPa and the IMF BZ component is stable and slightly negative -2 to -3 nT indicating that the more obvious solar wind drivers are absent for such an extreme event. The estimated distance from the nominal magnetopause to the spacecraft was 3 RE (from the Shue model), and the data does not show characteristics of multiple magnetopause crossings. Looking more broadly however, it appears that these events occurred during the recovery phase of quite strong magnetic storm as confirmed by the DST profile on March7, 2016. For this presentation, we combine the MMS observations with results of global MHD simulations to understand which one of several possible scenarios might explain MMS observations: either set of the Flux Transfer Events (FTE) resulting from the dayside reconnection or earthward-propagating dipolarization fronts caused by the tail reconnection.

  1. Determining the microwave coupling and operational efficiencies of a microwave plasma assisted chemical vapor deposition reactor under high pressure diamond synthesis operating conditions

    SciTech Connect

    Nad, Shreya; Gu, Yajun; Asmussen, Jes

    2015-07-15

    The microwave coupling efficiency of the 2.45 GHz, microwave plasma assisted diamond synthesis process is investigated by experimentally measuring the performance of a specific single mode excited, internally tuned microwave plasma reactor. Plasma reactor coupling efficiencies (η) > 90% are achieved over the entire 100–260 Torr pressure range and 1.5–2.4 kW input power diamond synthesis regime. When operating at a specific experimental operating condition, small additional internal tuning adjustments can be made to achieve η > 98%. When the plasma reactor has low empty cavity losses, i.e., the empty cavity quality factor is >1500, then overall microwave discharge coupling efficiencies (η{sub coup}) of >94% can be achieved. A large, safe, and efficient experimental operating regime is identified. Both substrate hot spots and the formation of microwave plasmoids are eliminated when operating within this regime. This investigation suggests that both the reactor design and the reactor process operation must be considered when attempting to lower diamond synthesis electrical energy costs while still enabling a very versatile and flexible operation performance.

  2. Growth and characterization of large, high quality single crystal diamond substrates via microwave plasma assisted chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Nad, Shreya

    Single crystal diamond (SCD) substrates can be utilized in a wide range of applications. Important issues in the chemical vapor deposition (CVD) of such substrates include: shrinking of the SCD substrate area, stress and cracking, high defect density and hence low electronic quality and low optical quality due to high nitrogen impurities. The primary objective of this thesis is to begin to address these issues and to find possible solutions for enhancing the substrate dimensions and simultaneously improving the quality of the grown substrates. The deposition of SCD substrates is carried out in a microwave cavity plasma reactor via the microwave plasma assisted chemical vapor deposition technique. The operation of the reactor was first optimized to determine the safe and efficient operating regime. By adjusting the matching of the reactor cavity with the help of four internal tuning length variables, the system was further matched to operate at a maximum overall microwave coupling efficiency of ˜ 98%. Even with adjustments in the substrate holder position, the reactor remains well matched with a coupling efficiency of ˜ 95% indicating good experimental performance over a wide range of operating conditions. SCD substrates were synthesized at a high pressure of 240 Torr and with a high absorbed power density of 500 W/cm3. To counter the issue of shrinking substrate size during growth, the effect of different substrate holder designs was studied. An increase in the substrate dimensions (1.23 -- 2.5 times) after growth was achieved when the sides of the seeds were shielded from the intense microwave electromagnetic fields in a pocket holder design. Using such pocket holders, high growth rates of 16 -- 32 mum/hr were obtained for growth times of 8 -- 72 hours. The polycrystalline diamond rim deposition was minimized/eliminated from these growth runs, hence successfully enlarging the substrate size. Several synthesized CVD SCD substrates were laser cut and separated

  3. High-resolution characterization of the diffusion of light chemical elements in metallic components by scanning microwave microscopy

    NASA Astrophysics Data System (ADS)

    Optasanu, Virgil; Bourillot, Eric; Vitry, Pauline; Plassard, Cédric; Beaurenaut, Laure; Jacquinot, Pierre; Herbst, Frédéric; Berger, Pascal; Lesniewska, Eric; Montessin, Tony

    2014-11-01

    An original sub-surface, high spatial resolution tomographic technique based on scanning microwave microscopy (SMM) is used to visualize in-depth materials with different chemical compositions. A significant phase difference in SMM between aluminum and chromium buried patterns has been observed. Moreover this technique was used to characterize a solid solution of a light chemical element (oxygen) in a metal lattice (zirconium). The large solubility of the oxygen in zirconium leads to modifications of the properties of the solid solution that can be measured by the phase shift signal in the SMM technique. The signal obtained in cross-section of an oxidized Zr sample shows the excellent agreement between phase shift profiles measured at different depths. Such a profile can reveal the length of diffusion of the oxygen in zirconium under the surface. The comparison with the oxygen concentration measured by nuclear reaction analysis shows excellent agreement in terms of length of diffusion and spatial distribution of the oxygen. A rapid calibration shows a linear dependence between the phase shift and the oxygen concentration. The SMM method opens up new possibilities for indirect measurements of the oxygen concentration dissolved in the metal lattice.

  4. Studies on the Conformational Landscape of Tert-Butyl Acetate Using Microwave Spectroscopy and Quantum Chemical Calculations

    NASA Astrophysics Data System (ADS)

    Zhao, YueYue; Mouhib, Halima; Li, Guohua; Stahl, Wolfgang; Kleiner, Isabelle

    2014-06-01

    The tert-Butyl acetate molecule was studied using a combination of quantum chemical calculations and molecular beam Fourier transform microwave spectroscopy in the 9 to 14 GHz range. Due to its rather rigid frame, the molecule possesses only two different conformers: one of Cs and one of C1 symmetry. According to ab initio calculations, the Cs conformer is 46 kJ/mol lower in energy and is the one observed in the supersonic jet. We report on the structure and dynamics of the most abundant conformer of tert-butyl acetate, with accurate rotational and centrifugal distortion constants. Additionally, the barrier to internal rotation of the acetyl methyl group was determined. Splittings due to the internal rotation of the methyl group of up to 1.3 GHz were observed in the spectrum. Using the programs XIAM and BELGI-Cs, we determine the barrier height to be about 113 cm-1 and compare the molecular parameters obtained from these two codes. Additionally, the experimental rotational constants were used to validate numerous quantum chemical calculations. This study is part of a larger project which aims at determining the lowest energy conformers of organic esters and ketones which are of interest for flavor or perfume synthetic applications Project partly supported by the PHC PROCOPE 25059YB.

  5. Flexural strength of acrylic resin repairs processed by different methods: water bath, microwave energy and chemical polymerization

    PubMed Central

    ARIOLI FILHO, João Neudenir; BUTIGNON, Luís Eduardo; PEREIRA, Rodrigo de Paula; LUCAS, Matheus Guilherme; MOLLO JUNIOR, Francisco de Assis

    2011-01-01

    Denture fractures are common in daily practice, causing inconvenience to the patient and to the dentists. Denture repairs should have adequate strength, dimensional stability and color match, and should be easily and quickly performed as well as relatively inexpensive. Objective The aim of this study was to evaluate the flexural strength of acrylic resin repairs processed by different methods: warm water-bath, microwave energy, and chemical polymerization. Material and methods Sixty rectangular specimens (31x10x2.5 mm) were made with warm water-bath acrylic resin (Lucitone 550) and grouped (15 specimens per group) according to the resin type used to make repair procedure: 1) specimens of warm water-bath resin (Lucitone 550) without repair (control group); 2) specimens of warm water-bath resin repaired with warm water-bath; 3) specimens of warm water-bath resin repaired with microwave resin (Acron MC); 4) specimens of warm water-bath resin repaired with autopolymerized acrylic resin (Simplex). Flexural strength was measured with the three-point bending in a universal testing machine (MTS 810 Material Test System) with load cell of 100 kgf under constant speed of 5 mm/min. Data were analyzed statistically by Kruskal-Wallis test (p<0.05). Results The control group showed the best result (156.04±1.82 MPa). Significant differences were found among repaired specimens and the results were decreasing as follows: group 3 (43.02±2.25 MPa), group 2 (36.21±1.20 MPa) and group 4 (6.74±0.85 MPa). Conclusion All repaired specimens demonstrated lower flexural strength than the control group. Repairs with autopolymerized acrylic resin showed the lowest flexural strength. PMID:21625742

  6. Probing the plasma chemistry in a microwave reactor used for diamond chemical vapor deposition by cavity ring down spectroscopy

    SciTech Connect

    Ma Jie; Richley, James C.; Ashfold, Michael N. R.; Mankelevich, Yuri A.

    2008-11-15

    Absolute column densities of C{sub 2}(a) and CH radicals and H(n=2) atoms have been measured in a diamond growing microwave reactor operating with hydrocarbon/Ar/H{sub 2} gas mixtures as functions of height (z) above the substrate surface and process conditions. The monitored species are each localized in the hot plasma region, where T{sub gas}{approx}3000 K, and their respective column densities are each reproduced, quantitatively, by two-dimensional (r,z) modeling of the plasma chemistry. The H(n=2) distribution is seen to peak nearer the substrate, reflecting its sensitivity both to thermal chemistry (which drives the formation of ground state H atoms) and the distributions of electron density (n{sub e}) and temperature (T{sub e}). All three column densities are found to be sensitively dependent on the C/H ratio in the process gas mixture but insensitive to the particular choice of hydrocarbon (CH{sub 4} and C{sub 2}H{sub 2}). The excellent agreement between measured and predicted column densities for all three probed species, under all process conditions investigated, encourages confidence in the predicted number densities of other of the more abundant radical species adjacent to the growing diamond surface which, in turn, reinforces the view that CH{sub 3} radicals are the dominant growth species in microwave activated hydrocarbon/Ar/H{sub 2} gas mixtures used in the chemical vapor deposition of microcrystalline and single crystal diamond samples.

  7. Structure determination of myrtenal by microwave spectroscopy and quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Chrayteh, Mhamad; Dréan, Pascal; Huet, Thérèse R.

    2017-06-01

    The rotational spectrum of myrtenal has been investigated using a Fourier transform microwave spectrometer coupled to a supersonic expansion in the 2-20 GHz frequency range. Of the two possible conformers expected in the gas phase, only the s-trans conformer which was calculated 12kJmol-1 lower in energy than the s-cis conformer was observed. The spectra of the ten 13C and 18O isotopic species of s-trans-myrtenal were observed in natural abundance. The ground state rotational constants are A = 1666.269706 (55)MHz, B = 962.344291 (40)MHz and C = 836.903508 (43)MHz . A partial rs structure was calculated using Kraitchman's equations. A r0 structure was also derived using additional data from a B3LYP/6-311++G(d,p) calculation. The structural parameters of the sbnd Cdbnd Csbnd Cdbnd O pattern of myrtenal (r0(Cdbnd C) = 1.341(16) Å, r0(Csbnd C) = 1.479(98) Å, r0(Cdbnd O) = 1.220(13) Å, ∠(OCC) = 124.4(13)° and ∠ (CCC) = 119.3 (11) °) are very close to those in trans-acrolein and in trans-trans-cinnamaldehyde.

  8. Microwave Plasma-Activated Chemical Vapor Deposition of Nitrogen-Doped Diamond. II: CH4/N2/H2 Plasmas.

    PubMed

    Truscott, Benjamin S; Kelly, Mark W; Potter, Katie J; Ashfold, Michael N R; Mankelevich, Yuri A

    2016-11-03

    We report a combined experimental and modeling study of microwave-activated dilute CH4/N2/H2 plasmas, as used for chemical vapor deposition (CVD) of diamond, under very similar conditions to previous studies of CH4/H2, CH4/H2/Ar, and N2/H2 gas mixtures. Using cavity ring-down spectroscopy, absolute column densities of CH(X, v = 0), CN(X, v = 0), and NH(X, v = 0) radicals in the hot plasma have been determined as functions of height, z, source gas mixing ratio, total gas pressure, p, and input power, P. Optical emission spectroscopy has been used to investigate, with respect to the same variables, the relative number densities of electronically excited species, namely, H atoms, CH, C2, CN, and NH radicals and triplet N2 molecules. The measurements have been reproduced and rationalized from first-principles by 2-D (r, z) coupled kinetic and transport modeling, and comparison between experiment and simulation has afforded a detailed understanding of C/N/H plasma-chemical reactivity and variations with process conditions and with location within the reactor. The experimentally validated simulations have been extended to much lower N2 input fractions and higher microwave powers than were probed experimentally, providing predictions for the gas-phase chemistry adjacent to the diamond surface and its variation across a wide range of conditions employed in practical diamond-growing CVD processes. The strongly bound N2 molecule is very resistant to dissociation at the input MW powers and pressures prevailing in typical diamond CVD reactors, but its chemical reactivity is boosted through energy pooling in its lowest-lying (metastable) triplet state and subsequent reactions with H atoms. For a CH4 input mole fraction of 4%, with N2 present at 1-6000 ppm, at pressure p = 150 Torr, and with applied microwave power P = 1.5 kW, the near-substrate gas-phase N atom concentration, [N]ns, scales linearly with the N2 input mole fraction and exceeds the concentrations [NH]ns, [NH2]ns

  9. Microwave Plasma-Activated Chemical Vapor Deposition of Nitrogen-Doped Diamond. II: CH4/N2/H2 Plasmas

    PubMed Central

    2016-01-01

    We report a combined experimental and modeling study of microwave-activated dilute CH4/N2/H2 plasmas, as used for chemical vapor deposition (CVD) of diamond, under very similar conditions to previous studies of CH4/H2, CH4/H2/Ar, and N2/H2 gas mixtures. Using cavity ring-down spectroscopy, absolute column densities of CH(X, v = 0), CN(X, v = 0), and NH(X, v = 0) radicals in the hot plasma have been determined as functions of height, z, source gas mixing ratio, total gas pressure, p, and input power, P. Optical emission spectroscopy has been used to investigate, with respect to the same variables, the relative number densities of electronically excited species, namely, H atoms, CH, C2, CN, and NH radicals and triplet N2 molecules. The measurements have been reproduced and rationalized from first-principles by 2-D (r, z) coupled kinetic and transport modeling, and comparison between experiment and simulation has afforded a detailed understanding of C/N/H plasma-chemical reactivity and variations with process conditions and with location within the reactor. The experimentally validated simulations have been extended to much lower N2 input fractions and higher microwave powers than were probed experimentally, providing predictions for the gas-phase chemistry adjacent to the diamond surface and its variation across a wide range of conditions employed in practical diamond-growing CVD processes. The strongly bound N2 molecule is very resistant to dissociation at the input MW powers and pressures prevailing in typical diamond CVD reactors, but its chemical reactivity is boosted through energy pooling in its lowest-lying (metastable) triplet state and subsequent reactions with H atoms. For a CH4 input mole fraction of 4%, with N2 present at 1–6000 ppm, at pressure p = 150 Torr, and with applied microwave power P = 1.5 kW, the near-substrate gas-phase N atom concentration, [N]ns, scales linearly with the N2 input mole fraction and exceeds the concentrations [NH]ns, [NH2]ns

  10. Plasma-enhanced synthesis of bactericidal quaternary ammonium thin layers on stainless steel and cellulose surfaces.

    PubMed

    Jampala, Soujanya N; Sarmadi, M; Somers, E B; Wong, A C L; Denes, F S

    2008-08-19

    We have investigated bottom-up chemical synthesis of quaternary ammonium (QA) groups exhibiting antibacterial properties on stainless steel (SS) and filter paper surfaces via nonequilibrium, low-pressure plasma-enhanced functionalization. Ethylenediamine (ED) plasma under suitable conditions generated films rich in secondary and tertiary amines. These functional structures were covalently attached to the SS surface by treating SS with O 2 and hexamethyldisiloxane plasma prior to ED plasma treatment. QA structures were formed by reaction of the plasma-deposited amines with hexyl bromide and subsequently with methyl iodide. Structural compositions were examined by electron spectroscopy for chemical analysis and Fourier transform infrared spectroscopy, and surface topography was investigated with atomic force microscopy and water contact angle measurements. Modified SS surfaces exhibited greater than a 99.9% decrease in Staphylococcus aureus counts and 98% in the case of Klebsiella pneumoniae. The porous filter paper surfaces with immobilized QA groups inactivated 98.7% and 96.8% of S. aureus and K. pneumoniae, respectively. This technique will open up a novel way for the synthesis of stable and very efficient bactericidal surfaces with potential applications in development of advanced medical devices and implants with antimicrobial surfaces.

  11. Occupational Lung Disease Risk and Exposure to Butter-Flavoring Chemicals After Implementation of Controls at a Microwave Popcorn Plant

    PubMed Central

    Kanwal, Richard; Kullman, Greg; Fedan, Kathleen B.; Kreiss, Kathleen

    2011-01-01

    Objectives After an outbreak of severe lung disease among workers exposed to butter-flavoring chemicals at a microwave popcorn plant, we determined whether or not lung disease risk declined after implementation of exposure controls. Methods National Institute for Occupational Safety and Health staff performed eight serial cross-sectional medical and industrial hygiene surveys at the plant from November 2000 through August 2003. Medical surveys included standardized questionnaires and spirometry testing. Industrial hygiene surveys measured levels of production-related air contaminants, including butter-flavoring chemicals such as diacetyl. All diacetyl concentrations above detectable limits were corrected for the effects of absolute humidity and days to sample extraction. Results Ventilation and isolation of the production process resulted in one to three orders of magnitude reductions in diacetyl air concentrations in different areas of the plant. Workers with past high exposures had stable chest symptoms over time; nasal, eye, and skin irritation symptoms declined. New workers had lower symptom prevalences and higher lung function than workers with past high exposures, and they did not worsen over time. In workers who had at least three spirometry tests, those with past high exposures were more likely to experience rapid declines in lung function than new workers. Conclusions Implemented controls lowered exposures to butter-flavoring chemicals and decreased lung disease risk for much of the plant workforce. Some workers with continuing potential for intermittent, short-term peak and measurable time-weighted exposures remain at risk and should use respiratory protection and have regularly scheduled spirometry to detect rapid lung function declines that may be work-related. Close follow-up of such workers is likely to yield additional information on risks due to peak and time-weighted exposure levels. PMID:21800743

  12. Occupational lung disease risk and exposure to butter-flavoring chemicals after implementation of controls at a microwave popcorn plant.

    PubMed

    Kanwal, Richard; Kullman, Greg; Fedan, Kathleen B; Kreiss, Kathleen

    2011-01-01

    After an outbreak of severe lung disease among workers exposed to butter-flavoring chemicals at a microwave popcorn plant, we determined whether or not lung disease risk declined after implementation of exposure controls. National Institute for Occupational Safety and Health staff performed eight serial cross-sectional medical and industrial hygiene surveys at the plant from November 2000 through August 2003. Medical surveys included standardized questionnaires and spirometry testing. Industrial hygiene surveys measured levels of production-related air contaminants, including butter-flavoring chemicals such as diacetyl. All diacetyl concentrations above detectable limits were corrected for the effects of absolute humidity and days to sample extraction. Ventilation and isolation of the production process resulted in one to three orders of magnitude reductions in diacetyl air concentrations in different areas of the plant. Workers with past high exposures had stable chest symptoms over time; nasal, eye, and skin irritation symptoms declined. New workers had lower symptom prevalences and higher lung function than workers with past high exposures, and they did not worsen over time. In workers who had at least three spirometry tests, those with past high exposures were more likely to experience rapid declines in lung function than new workers. Implemented controls lowered exposures to butter-flavoring chemicals and decreased lung disease risk for much of the plant workforce. Some workers with continuing potential for intermittent, short-term peak and measurable time-weighted exposures remain at risk and should use respiratory protection and have regularly scheduled spirometry to detect rapid lung function declines that may be work-related. Close follow-up of such workers is likely to yield additional information on risks due to peak and time-weighted exposure levels.

  13. MICROWAVE ACCELERATED SOLVENT-FREE CHEMICAL REACTIONS, PUBLISHED IN AMPERE NEWSLETTER, ISSUE 29, JUNE 2001

    EPA Science Inventory

    The worldwide annual usage of volatile organic solvents is generally of the order of ~4 billion pounds. In the environmentally conscieous era, the focus in to design chemical processes and products that eliminate or minimize the waste generation and the ideal approach may compris...

  14. MICROWAVE ACCELERATED SOLVENT-FREE CHEMICAL REACTIONS, PUBLISHED IN AMPERE NEWSLETTER, ISSUE 29, JUNE 2001

    EPA Science Inventory

    The worldwide annual usage of volatile organic solvents is generally of the order of ~4 billion pounds. In the environmentally conscieous era, the focus in to design chemical processes and products that eliminate or minimize the waste generation and the ideal approach may compris...

  15. Chemical detoxification of trichloroethylene and 1,1,1-trichloroethane in a microwave discharge plasma reactor at atmospheric pressure

    SciTech Connect

    Krause, T.R.; Helt, J.E.

    1991-01-01

    This report focuses on the application of plasma technology to hazardous waste treatment. Microwave sustained plasmas are used to thermal degrade trichloroethylene and trichloroethane at atmospheric pressure. (JL)

  16. Chemical detoxification of trichloroethylene and 1,1,1-trichloroethane in a microwave discharge plasma reactor at atmospheric pressure

    SciTech Connect

    Krause, T.R.; Helt, J.E.

    1991-12-31

    This report focuses on the application of plasma technology to hazardous waste treatment. Microwave sustained plasmas are used to thermal degrade trichloroethylene and trichloroethane at atmospheric pressure. (JL)

  17. Microwave enhanced alcoholysis of non-edible (algal, jatropha and pongamia) oils using chemically activated egg shell derived CaO as heterogeneous catalyst.

    PubMed

    Joshi, Girdhar; Rawat, Devendra S; Sharma, Amit Kumar; Pandey, Jitendra K

    2016-11-01

    Microwave enhanced fast and efficient alcoholysis (methanolysis and ethanolysis) of non-edible oils (algal, jatropha and pongamia) is achieved using chemically activated waste egg shell derived CaO (i.e. CaO(cesp)) as heterogeneous catalyst. CaO(cesp) was extracted from waste chicken egg shell and further activated chemically by supporting transition metal oxide. The maximum conversion was achieved using 3wt% catalysts under 700W microwave irradiation and 10:1 alcohol/oil ratio in 6min. Alcoholysis using ZnO activated CaO(cesp) catalyst has shown higher reaction yields in comparison to other modified catalysts. Methanolysis has shown better biodiesel conversion in comparison to ethanolysis. The catalyst has shown longer lifetime and sustained activity after being used for four cycles. Due to more saturated fatty acid content; algal biodiesel has shown improved fuel properties in comparison to other biodiesels. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Enhanced field emission characteristics of boron doped diamond films grown by microwave plasma assisted chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Koinkar, Pankaj M.; Patil, Sandip S.; Kim, Tae-Gyu; Yonekura, Daisuke; More, Mahendra A.; Joag, Dilip S.; Murakami, Ri-ichi

    2011-01-01

    Boron doped diamond films were synthesized on silicon substrates by microwave plasma chemical vapor deposition (MPCVD) technique. The effect of B 2O 3 concentration varied from 1000 to 5000 ppm on the field emission characteristics was examined. The surface morphology and quality of films were characterized by scanning electron microscope (SEM) and Raman spectroscopy. The surface morphology obtained by SEM showed variation from facetted microcrystal covered with nanometric grains to cauliflower of nanocrystalline diamond (NCD) particles with increasing B 2O 3 concentration. The Raman spectra confirm the formation of NCD films. The field emission properties of NCD films were observed to improve upon increasing boron concentration. The values of the onset field and threshold field are observed to be as low as 0.36 and 0.08 V/μm, respectively. The field emission current stability investigated at the preset value of ˜1 μA is observed to be good, in each case. The enhanced field emission properties are attributed to the better electrical conductivity coupled with the nanometric features of the diamond films.

  19. Chemical vapour deposition enhanced by atmospheric microwave plasmas: a large-scale industrial process or the next nanomanufacturing tool?

    NASA Astrophysics Data System (ADS)

    Belmonte, T.; Gries, T.; Cardoso, R. P.; Arnoult, G.; Kosior, F.; Henrion, G.

    2011-04-01

    This paper describes several specific aspects of atmospheric plasma deposition carried out with a microwave resonant cavity. Deposition over a wide substrate is first studied. We show that high deposition rates (several hundreds of μm h-1) are due to localization of fluxes on the substrate by convection when slightly turbulent flows are used. Next, we describe possible routes to localize deposition over a nanometre-sized area. Scaling down atmospheric plasma deposition is possible and two strategies to reach nanometre scales are described. Finally, we study self-organization of SiO2 nanodots deposited by chemical vapour deposition at atmospheric pressure enhanced by an Ar-O2 micro-afterglow operating at high temperature (>1200 K). When the film being deposited is thin enough (~500 nm) nanodots are obtained and they can be assembled into threads to create patterned surfaces. When the coating becomes thicker (~1 µm), and for relatively high content in HMDSO, SiO2 walls forming hexagonal cells are obtained.

  20. Generation and application of LET calibration curve for neutron dosimetry using CR-39 detector and microwave induced chemical etching.

    PubMed

    Tripathy, S P; Sahoo, G S; Paul, S; Kumar, P; Sharma, S D; Santra, S; Pal, A; Kundu, A; Bandyopadhyay, T; Avasthi, D K

    2017-06-01

    Microwave induced chemical etching (MICE) has been established as a faster and improved technique compared to other contemporary etching techniques for the development of tracks in a CR-39 detector. However, the methodology could not be applied for LET (linear energy transfer) spectrometry due to lack of a calibration curve using this method. For this purpose, a new LET calibration curve in the range of 12 keV/μm-799 keV/μm was generated considering different ions such as H, Li, C, O, and F on CR-39 having different LETs in water. An empirical relation was established from the obtained calibration curve for determining the value of LET (in water) from the value of V, the ratio of track etch rate to bulk etch rate. For application of this calibration curve in neutron dosimetry, CR-39 detectors were irradiated to neutrons generated from 120 and 142 MeV (16)O+(27)Al systems followed by a similar MICE procedure. The absorbed dose (DLET) and the dose equivalent (HLET) were obtained from the LET spectra and were found to be 13% and 10% higher for 142 MeV (16)O+(27)Al system than those for 120 MeV (16)O+(27)Al system, respectively. The outcome of the study demonstrates the possibility of using the MICE technique for neutron dose estimation by CR-39 via LET spectrometry.

  1. Generation and application of LET calibration curve for neutron dosimetry using CR-39 detector and microwave induced chemical etching

    NASA Astrophysics Data System (ADS)

    Tripathy, S. P.; Sahoo, G. S.; Paul, S.; Kumar, P.; Sharma, S. D.; Santra, S.; Pal, A.; Kundu, A.; Bandyopadhyay, T.; Avasthi, D. K.

    2017-06-01

    Microwave induced chemical etching (MICE) has been established as a faster and improved technique compared to other contemporary etching techniques for the development of tracks in a CR-39 detector. However, the methodology could not be applied for LET (linear energy transfer) spectrometry due to lack of a calibration curve using this method. For this purpose, a new LET calibration curve in the range of 12 keV/μm-799 keV/μm was generated considering different ions such as H, Li, C, O, and F on CR-39 having different LETs in water. An empirical relation was established from the obtained calibration curve for determining the value of LET (in water) from the value of V, the ratio of track etch rate to bulk etch rate. For application of this calibration curve in neutron dosimetry, CR-39 detectors were irradiated to neutrons generated from 120 and 142 MeV 16O+27Al systems followed by a similar MICE procedure. The absorbed dose (DLET) and the dose equivalent (HLET) were obtained from the LET spectra and were found to be 13% and 10% higher for 142 MeV 16O+27Al system than those for 120 MeV 16O+27Al system, respectively. The outcome of the study demonstrates the possibility of using the MICE technique for neutron dose estimation by CR-39 via LET spectrometry.

  2. Mass densification and defect restoration in chemical vapor deposition silicon dioxide film using Ar plasma excited by microwave

    SciTech Connect

    Kawase, Kazumasa Motoya, Tsukasa; Uehara, Yasushi; Teramoto, Akinobu; Suwa, Tomoyuki; Ohmi, Tadahiro

    2014-09-01

    Silicon dioxide (SiO{sub 2}) films formed by chemical vapor deposition (CVD) have been treated with Ar plasma excited by microwave. The changes of the mass densities, carrier trap densities, and thicknesses of the CVD-SiO{sub 2} films with the Ar plasma treatments were investigated. The mass density depth profiles were estimated with X-Ray Reflectivity (XRR) analysis using synchrotron radiation. The densities of carrier trap centers due to defects of Si-O bond network were estimated with X-ray Photoelectron Spectroscopy (XPS) time-dependent measurement. The changes of the thicknesses due to the oxidation of Si substrates were estimated with the XRR and XPS. The mass densities of the CVD-SiO{sub 2} films are increased by the Ar plasma treatments. The carrier trap densities of the films are decreased by the treatments. The thicknesses of the films are not changed by the treatments. It has been clarified that the mass densification and defect restoration in the CVD-SiO{sub 2} films are caused by the Ar plasma treatments without the oxidation of the Si substrates.

  3. Non-Covalent Interactions and Internal Dynamics in Pyridine-Ammonia a Combined Quantum-Chemical and Microwave Spectroscopy Study

    NASA Astrophysics Data System (ADS)

    Spada, Lorenzo; Tasinato, Nicola; Vazart, Fanny; Barone, Vincenzo; Caminati, Walther; Puzzarini, Cristina

    2017-06-01

    The 1:1 complex of ammonia with pyridine has been characterized by using state-of-the-art quantum-chemical computations combined with pulsed-jet Fourier-Transform microwave spectroscopy. The computed potential energy landscape pointed out the formation of a stable σ-type complex, which has been confirmed experimentally: the analysis of the rotational spectrum showed the presence of only one 1:1 pyridine - ammonia adduct. Each rotational transition is split into several components due to the internal rotation of NH_3 around its C_3 axis and to the hyperfine structure of both ^{14}N quadrupolar nuclei, thus providing the unequivocal proof that the two molecules form a σ-type complex involving both a N-H\\cdotsN and a C-H\\cdotsN hydrogen bond. The dissociation energy (BSSE and ZPE corrected) has been estimated to be 11.5 kJ\\cdotmol^{-1}. This work represents the first application of an accurate, yet efficient computational scheme, designed for the investigation of small biomolecules, to a molecular cluster.

  4. Microwave, high-resolution infrared, and quantum chemical investigations of CHBrF2: ground and v4 = 1 states.

    PubMed

    Cazzoli, Gabriele; Cludi, Lino; Puzzarini, Cristina; Stoppa, Paolo; Pietropolli Charmet, Andrea; Tasinato, Nicola; Baldacci, Agostino; Baldan, Alessandro; Giorgianni, Santi; Wugt Larsen, René; Stopkowicz, Stella; Gauss, Jürgen

    2011-02-03

    A combined microwave, infrared, and computational investigation of CHBrF(2) is reported. For the vibrational ground state, measurements in the millimeter- and sub-millimeter-wave regions for CH(79)BrF(2) and CH(81)BrF(2) provided rotational and centrifugal-distortion constants up to the sextic terms as well as the hyperfine parameters (quadrupole-coupling and spin-rotation interaction constants) of the bromine nucleus. The determination of the latter was made possible by recording of spectra at sub-Doppler resolution, achieved by means of the Lamb-dip technique, and supporting the spectra analysis by high-level quantum chemical calculations at the coupled-cluster level. In this context, the importance of relativistic effects, which are of the order of 6.5% and included in the present work using second-order direct perturbation theory, needs to be emphasized for accurate predictions of the bromine quadrupole-coupling constants. The infrared measurements focused on the ν(4) fundamental band of CH(79)BrF(2). Fourier transform investigations using a synchrotron radiation source provided the necessary resolution for the observation and analysis of the rotational structure. The spectroscopic parameters of the v(4) = 1 state were found to be close to those of the vibrational ground state, indicating that the ν(4) band is essentially unaffected by perturbations.

  5. Influence of deposition rate on the structural properties of plasma-enhanced CVD epitaxial silicon

    NASA Astrophysics Data System (ADS)

    Chen, Wanghua; Cariou, Romain; Hamon, Gwenaëlle; Léal, Ronan; Maurice, Jean-Luc; Cabarrocas, Pere Roca I.

    2017-03-01

    Solar cells based on epitaxial silicon layers as the absorber attract increasing attention because of the potential cost reduction. In this work, we studied the influence of the deposition rate on the structural properties of epitaxial silicon layers produced by plasma-enhanced chemical vapor deposition (epi-PECVD) using silane as a precursor and hydrogen as a carrier gas. We found that the crystalline quality of epi-PECVD layers depends on their thickness and deposition rate. Moreover, increasing the deposition rate may lead to epitaxy breakdown. In that case, we observe the formation of embedded amorphous silicon cones in the epi-PECVD layer. To explain this phenomenon, we develop a model based on the coupling of hydrogen and built-in strain. By optimizing the deposition conditions to avoid epitaxy breakdown, including substrate temperatures and plasma potential, we have been able to synthesize epi-PECVD layers up to a deposition rate of 8.3 Å/s. In such case, we found that the incorporation of hydrogen in the hydrogenated crystalline silicon can reach 4 at. % at a substrate temperature of 350 °C.

  6. Effects of ROS and RNS in non-equilibrium plasma enhanced oxidizing and nitriding

    NASA Astrophysics Data System (ADS)

    Datsyuk, Vitaly; Izmailov, Igor; Naumov, Vadym; Khomich, Vladimir; Tsiolko, Vyacheslav

    2016-09-01

    Plasma enhanced oxidizing and nitriding processes are of great interest for physics and applications. However, despite all advances in plasma technology, mechanisms of non-equilibrium plasma chemistry are not quite clear, particularly concerning reactive oxygen and nitrogen species (ROS/RNS) in metastable states. We tried to study this matter more detail. Experiments were done in a low temperature magnetron with a non-self-sustained glow discharge in oxygen/nitrogen/argon mixtures, employing electrical and optical diagnostics. Measurements showed that plasma processing is accompanied by the formation of electronically excited particles ROS/RNS. Computer modeling by using 0D-kinetic and 1D-fluid models including ionization, excitation, dissociation-recombination, vibrational relaxation, collisional quenching and radiation revealed the most probable mechanisms of plasma-chemical transformations. Effects of metastables of singlet oxygen O2*(a,b)and nitrogen N2*(A)as well as small but important radicals O*(1 D), N*(2 D) were also examined. Our study confirms the role of ROS/RNS in plasma kinetics and indicates the way toward more efficient oxygen and nitrogen plasma processing.

  7. Influence of deposition rate on the structural properties of plasma-enhanced CVD epitaxial silicon

    PubMed Central

    Chen, Wanghua; Cariou, Romain; Hamon, Gwenaëlle; Léal, Ronan; Maurice, Jean-Luc; Cabarrocas, Pere Roca i

    2017-01-01

    Solar cells based on epitaxial silicon layers as the absorber attract increasing attention because of the potential cost reduction. In this work, we studied the influence of the deposition rate on the structural properties of epitaxial silicon layers produced by plasma-enhanced chemical vapor deposition (epi-PECVD) using silane as a precursor and hydrogen as a carrier gas. We found that the crystalline quality of epi-PECVD layers depends on their thickness and deposition rate. Moreover, increasing the deposition rate may lead to epitaxy breakdown. In that case, we observe the formation of embedded amorphous silicon cones in the epi-PECVD layer. To explain this phenomenon, we develop a model based on the coupling of hydrogen and built-in strain. By optimizing the deposition conditions to avoid epitaxy breakdown, including substrate temperatures and plasma potential, we have been able to synthesize epi-PECVD layers up to a deposition rate of 8.3 Å/s. In such case, we found that the incorporation of hydrogen in the hydrogenated crystalline silicon can reach 4 at. % at a substrate temperature of 350 °C. PMID:28262840

  8. Facile plasma-enhanced deposition of ultrathin crosslinked amino acid films for conformal biometallization.

    PubMed

    Anderson, Kyle D; Slocik, Joseph M; McConney, Michael E; Enlow, Jesse O; Jakubiak, Rachel; Bunning, Timothy J; Naik, Rajesh R; Tsukruk, Vladimir V

    2009-03-01

    A novel method for the facile fabrication of conformal, ultrathin, and uniform synthetic amino acid coatings on a variety of practical surfaces by plasma-enhanced chemical vapor deposition is introduced. Tyrosine, which is utilized as an agent to reduce gold nanoparticles from solution, is sublimed into the plasma field and directly deposited on a variety of substrates to form a homogeneous, conformal, and robust polyamino acid coating in a one-step, solvent-free process. This approach is applicable to many practical surfaces and allows surface-induced biometallization while avoiding multiple wet-chemistry treatments that can damage many soft materials. Moreover, by placing a mask over the substrate during deposition, the tyrosine coating can be micropatterned. Upon its exposure to a solution of gold chloride, a network of gold nanoparticles forms on the surface, replicating the initial micropattern. This method of templated biometallization is adaptable to a variety of practical inorganic and organic substrates, such as silicon, glass, nitrocellulose, polystyrene, polydimethylsiloxane, polytetrafluoroethylene, polyethylene, and woven silk fibers. No special pretreatment is necessary, and the technique results in a rapid, conformal amino acid coating that can be utilized for further biometallization.

  9. Plasma-enhanced atomic layer deposition for plasmonic TiN

    NASA Astrophysics Data System (ADS)

    Otto, Lauren M.; Hammack, Aaron T.; Aloni, Shaul; Ogletree, D. Frank; Olynick, Deirdre L.; Dhuey, Scott; Stadler, Bethanie J. H.; Schwartzberg, Adam M.

    2016-09-01

    This work presents the low temperature plasma-enhanced atomic layer deposition (PE-ALD) of TiN, a promising plasmonic synthetic metal. The plasmonics community has immediate needs for alternatives to traditional plasmonic materials (e.g. Ag and Au), which lack chemical, thermal, and mechanical stability. Plasmonic alloys and synthetic metals have significantly improved stability, but their growth can require high-temperatures (>400 °C), and it is difficult to control the thickness and directionality of the resulting film, especially on technologically important substrates. Such issues prevent the application of alternative plasmonic materials for both fundamental studies and large-scale industrial applications. Alternatively, PE-ALD allows for conformal deposition on a variety of substrates with consistent material properties. This conformal coating will allow the creation of exotic three-dimensional structures, and low-temperature deposition techniques will provide unrestricted usage across a variety of platforms. The characterization of this new plasmonic material was performed with in-situ spectroscopic ellipsometry as well as Auger electron spectroscopy for analysis of TiN film sensitivity to oxide cross-contamination. Plasmonic TiN films were fabricated, and a chlorine plasma etch was found to pattern two dimensional gratings as a test structure. Optical measurements of 900 nm period gratings showed reasonable agreement with theoretical modeling of the fabricated structures, indicating that ellipsometry models of the TiN were indeed accurate.

  10. Plasma-enhanced synthesis of surfaces that kill bacteria on contact

    NASA Astrophysics Data System (ADS)

    Jampala, Soujanya Naga

    High incidences of microbial contamination and infections are a major concern in all existing and evolving technologies of medicine and biology. The propensity towards infections is directly related to bacterial colonization and biofilms on surfaces. This dissertation presents the development of surfaces that can kill bacteria on contact by using cold plasma technology. Quaternary ammonium (QA) groups are known to exhibit antibacterial characteristics in water-based environments. To overcome the limitations of residual toxicity, alternative strategies involving covalent attachment of QA groups to metallic and cellulosic surfaces have been developed. Low pressure, non-equilibrium plasma-enhanced functionalization and subsequent ex situ chemical reactions were designed for step-by-step "bottom-up" chemical synthesis of QA groups covalently anchored to surfaces. The plasma processes under selected discharge parameters generated structure- and functionality-controlled crosslinked networks of macromolecular layers with high concentrations of reactive amine groups. Subsequent derivatization of the plasma-deposited films with alkyl halides yielded surface-bound QA groups rendering surfaces with high bactericidal efficacy against Gram-positive Staphylococcus aureus and Gram-negative Klebsiella pneumoniae. Stainless steel and cotton surfaces sequentially treated with ethylene diamine plasma, n-hexyl bromide and methyl iodide exhibited at least 99.9% and 98% kill of S. aureus and K. pneumoniae respectively. The influence of chemical architecture of QA groups with different alkyl substituents on the efficacy of bactericidal surfaces was quantified. Results from this work will permit the development of novel plasma-aided technologies for the synthesis of antibacterial surfaces with potential biomedical applications. The cold plasma approach can be used on any solid material surfaces including polymers, metals, ceramics and semiconductors.

  11. Orthogonal array optimization of microwave-assisted derivatization for determination of trace amphetamine and methamphetamine using negative chemical ionization gas chromatography-mass spectrometry.

    PubMed

    Chung, Li-Wen; Lin, Keh-Liang; Yang, Thomas Ching-Cherng; Lee, Maw-Rong

    2009-05-01

    An orthogonal array design (OAD) was applied to optimize microwave-assisted derivatization (MAD) for analysis of trace amphetamine (AM) and methamphetamine (MA) by negative chemical ionization gas chromatography-mass spectrometry (NCI GC-MS). The 2,3,4,5,6-pentafluorobenzoyl chloride (PFBC) was used as a derivatization reagent. Experimental factors including solvent, microwave power, and irradiation time at four-levels were studied in 16 trials by OAD(16) (4(4)). The significance of these factors was investigated using analysis of variance (ANOVA) and percent contribution (PC). Solvent is statistically demonstrated a chief factor; microwave power and irradiation time are secondary factors. Under the optimum condition, calibration curve of AM is linear over a range from 0.01 to 100 ng mL(-1) with correlation coefficient 0.9988, and MA from 0.1 to 1000 ng mL(-1) with correlation coefficient 0.9951. The limit of detection (LOD) is 1.20 pg mL(-1) for AM and 13.04 pg mL(-1) for MA. An applicability of the method was tested by analyzing urine samples from amphetamine-type stimulants (ATS)-abusing suspects. Consequently, the OAD method not only optimizes the MAD condition for determination of trace AM and MA, but identifies the effects of factor solvent, microwave power and irradiation time on the MAD performance.

  12. Plasma enhanced atomic layer deposition of SiN{sub x}:H and SiO{sub 2}

    SciTech Connect

    King, Sean W.

    2011-07-15

    As the nanoelectronics industry looks to transition to both three dimensional transistor and interconnect technologies at the <22 nm node, highly conformal dielectric coatings with precise thickness control are increasingly being demanded. Plasma enhanced chemical vapor deposition (PECVD) currently fills this role for most applications requiring low temperature processing but does not always meet step coverage and thickness precision requirements. The authors present results for a hybrid technique, plasma enhanced atomic layer deposition (PEALD), which utilizes typical PECVD process gases and tooling while delivering improved topography coverage and thickness control. Specifically, the authors show that alternating SiH{sub 4} gas/N{sub 2} plasma exposures applied in an atomic layer deposition sequence can be used to deposit SiN{sub x}:H films in a self-limiting fashion with improved conformality and superior performance as a moisture barrier. PEALD of SiO{sub 2} using alternating SiH{sub 4} and CO{sub 2} plasma exposures is further demonstrated.

  13. Understanding the structure and dynamic of odorants in the gas phase using a combination of microwave spectroscopy and quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Mouhib, Halima

    2014-07-01

    This tutorial is an introduction for PhD students and researchers who intend to start their future work in the field of microwave spectroscopy to investigate structural and dynamical aspects of isolated molecular systems in the gas phase. Although the presented case studies are related to odorants, i.e., volatile molecules that possess a noticeable scent, the background and applications of the method can be transferred to any other resembling molecular system. In the early days, microwave spectroscopy was mainly related to the structure determination of very small systems such as OCS or ammonia, where the bond lengths could be determined with high accuracy by measuring the different isotopic species of the molecules. Nowadays, the method is far more advanced and is also used to tackle various fundamental molecular problems in different fields such as physical chemistry and molecular physics. Interesting questions that can be investigated concern, e.g., the molecular structure, i.e., the different conformations, not only of the isolated molecule but also of van der Waals complexes with water, noble gases or other molecules. The dynamical and intra- or intermolecular effects can be straightforwardly observed without the influence of the environment as in the condensed phase. This evolution was only achieved by using quantum chemical methods as a complementary tool to elude the necessity of isotopologues for structure determination, which cannot be realized for large systems (>5 atoms). The combination of microwave spectroscopy and quantum chemical calculations is the method of choice when it comes to sampling the conformational space of molecules. This is particularly the case when small energy differences make it difficult to determine the conformers of the lowest energy using computational methods alone. Although quantum chemical calculations are important for the validation of microwave spectra, the focus of the tutorial is set on the experimental part of the

  14. Exploring the plasma chemistry in microwave chemical vapor deposition of diamond from C/H/O gas mixtures.

    PubMed

    Kelly, Mark W; Richley, James C; Western, Colin M; Ashfold, Michael N R; Mankelevich, Yuri A

    2012-09-27

    Microwave (MW)-activated CH(4)/CO(2)/H(2) gas mixtures operating under conditions relevant to diamond chemical vapor deposition (i.e., X(C/Σ) = X(elem)(C)/(X(elem)(C) + X(elem)(O)) ≈ 0.5, H(2) mole fraction = 0.3, pressure, p = 150 Torr, and input power, P = 1 kW) have been explored in detail by a combination of spatially resolved absorption measurements (of CH, C(2)(a), and OH radicals and H(n = 2) atoms) within the hot plasma region and companion 2-dimensional modeling of the plasma. CO and H(2) are identified as the dominant species in the plasma core. The lower thermal conductivity of such a mixture (cf. the H(2)-rich plasmas used in most diamond chemical vapor deposition) accounts for the finding that CH(4)/CO(2)/H(2) plasmas can yield similar maximal gas temperatures and diamond growth rates at lower input powers than traditional CH(4)/H(2) plasmas. The plasma chemistry and composition is seen to switch upon changing from oxygen-rich (X(C/Σ) < 0.5) to carbon-rich (X(C/Σ) > 0.5) source gas mixtures and, by comparing CH(4)/CO(2)/H(2) (X(C/Σ) = 0.5) and CO/H(2) plasmas, to be sensitive to the choice of source gas (by virtue of the different prevailing gas activation mechanisms), in contrast to C/H process gas mixtures. CH(3) radicals are identified as the most abundant C(1)H(x) [x = 0-3] species near the growing diamond surface within the process window for successful diamond growth (X(C/Σ) ≈ 0.5-0.54) identified by Bachmann et al. (Diamond Relat. Mater.1991, 1, 1). This, and the findings of similar maximal gas temperatures (T(gas) ~2800-3000 K) and H atom mole fractions (X(H)~5-10%) to those found in MW-activated C/H plasmas, points to the prevalence of similar CH(3) radical based diamond growth mechanisms in both C/H and C/H/O plasmas.

  15. Environmentally friendly chemical recycling of poly(bisphenol-A carbonate) through phase transfer-catalysed alkaline hydrolysis under microwave irradiation.

    PubMed

    Tsintzou, Georgia P; Antonakou, Eleni V; Achilias, Dimitris S

    2012-11-30

    The various and widespread uses of polycarbonate (PC) polymers require a meaningful and environmentally friendly disposal method. In this study, depolymerisation of polycarbonate with water in a microwave reactor is suggested as a recycling method. Hydrolysis was investigated in an alkaline (NaOH) solution using a phase-transfer catalyst. All of the experiments were carried out in a sealed microwave reactor, in which the reaction pressure, temperature and microwave power were continuously controlled and recorded. In the hydrolysis products, bisphenol-A monomer was obtained and identified by FTIR measurements. PC degradation higher than 80% can be obtained at 160°C after a microwave irradiation time of either 40 min or 10 min using either a 5 or 10% (w/v) NaOH solution, respectively. GPC, TGA and DSC measurements of the PC residues revealed that surface erosion is the degradation mechanism. First-order reaction kinetics were estimated by implementing a simple kinetic model. Finally, greater than 85% degradation was achieved when waste CDs were treated with the same method. The results confirm the importance of the microwave power technique as a promising recycling method for PC-based waste plastics, resulting in monomer recovery in addition to substantial energy savings.

  16. Plasma enhanced C1 chemistry for green technology

    NASA Astrophysics Data System (ADS)

    Nozaki, Tomohiro

    2013-09-01

    Plasma catalysis is one of the innovative next generation green technologies that meet the needs for energy and materials conservation as well as environmental protection. Non-thermal plasma uniquely generates reactive species independently of reaction temperature, and these species are used to initiate chemical reactions at unexpectedly lower temperatures than normal thermochemical reactions. Non-thermal plasma thus broadens the operation window of existing chemical conversion processes, and ultimately allows modification of the process parameters to minimize energy and material consumption. We have been specifically focusing on dielectric barrier discharge (DBD) as one of the viable non-thermal plasma sources for practical fuel reforming. In the presentation, room temperature one-step conversion of methane to methanol and hydrogen using a miniaturized DBD reactor (microplasma reactor) is highlighted. The practical impact of plasma technology on existing C1-chemistry is introduced, and then unique characteristics of plasma fuel reforming such as non-equilibrium product distribution is discussed.

  17. Microwave heating effects on the chemical composition and the antioxidant capacity of tataouine virgin olive oils from Tunisia.

    PubMed

    Oueslati, Imen; Taamalli, Wael; Haddada, Faouzia M; Zarrouk, Mokhtar

    2010-10-01

    Four Tunisian virgin olive oils (VOOs), derived from varieties (Chemlali Tataouine, Zarrazi Douirat, Fakhari Douirat, and Dhokar Douirat) grown in the harsh pedoclimatic conditions of the region of Tataouine, were evaluated for their responses to microwave heating. Aside from fatty acid composition, all other evaluated parameters were affected by microwave heating, and their variations depend on the genetic factor. Chemlali Tataouine VOO exhibited the slowest biophenol degradation rate and the least diminution in oxidative stability and consequently, its total fraction and both lipidic and methanolic fractions remained unchanged with an exceptional antioxidant potential. In the remaining studied VOOs, the biophenol contents, the oxidative stability, and the antioxidant potential underwent gradual decreases; nevertheless, their levels at the longer treatment time are close to some fresh VOOs. These results should be taken into consideration when Tataouine VOOs are recommended for microwave heating.

  18. Microwave Ovens

    MedlinePlus

    ... Standards Industry Guidance Other Resources Description Microwave ovens heat food using microwaves, a form of electromagnetic radiation ... vibration results in friction between molecules, which produces heat that cooks the food. Risks/Benefits Microwaves are ...

  19. [EVALUATION OF CHANGES OF GEOMETRICAL PARAMETERS OF ALGINATE DENTAL IMPRESSIONS DUE TO THE INFLUENCE OF CHEMICAL AND MICROWAVE DISINFECTION METHOD USING 3D TECHNOLOGIES].

    PubMed

    Nespraydko, V P; Shevchuk, V A; Michaylov, A A; Lyseyko, N V

    2015-01-01

    This clinical and laboratory study evaluated the effect of two methods of disinfection in different modes at the volume changes of alginate dental impressions and plaster models poured from them, as compared to the same parameters of plastic master models (PMM), using three-dimensional non-contact laser scanner and software. Immersion chemical disinfection for 15 min, microwave disinfection at 354 W for 10 minutes and combined disinfection with the power of 319 W for 4 minutes did not significantly affect the volumetric dimensional accuracy of the alginate impressions (P > 0.05).

  20. Graphene Synthesis by Plasma-Enhanced CVD Growth with Ethanol

    SciTech Connect

    Campo, Teresa; Cotto, María; Márquez, Francisco; Elizalde, Eduardo; Morant, Carmen

    2016-03-01

    A modified route to synthesize graphene flakes is proposed using the Chemical Vapor Deposition (CVD) technique, by using copper substrates as supports. The carbon source used was ethanol, the synthesis temperature was 950°C and the pressure was controlled along the whole process. In this CVD synthesis process the incorporation of the carbon source was produced at low pressure and 950°C inducing the appearance of a plasma blue flash inside the quartz tube. Apparently, the presence of this plasma blue flash is required for obtaining graphene flakes. The synthesized graphene was characterized by different techniques, showing the presence of non-oxidized graphene with high purity.

  1. Graphene Synthesis by Plasma-Enhanced CVD Growth with Ethanol

    DOE PAGES

    Campo, Teresa; Cotto, María; Márquez, Francisco; ...

    2016-03-01

    A modified route to synthesize graphene flakes is proposed using the Chemical Vapor Deposition (CVD) technique, by using copper substrates as supports. The carbon source used was ethanol, the synthesis temperature was 950°C and the pressure was controlled along the whole process. In this CVD synthesis process the incorporation of the carbon source was produced at low pressure and 950°C inducing the appearance of a plasma blue flash inside the quartz tube. Apparently, the presence of this plasma blue flash is required for obtaining graphene flakes. The synthesized graphene was characterized by different techniques, showing the presence of non-oxidized graphenemore » with high purity.« less

  2. Plasma-enhanced atomic layer deposition: a gas-phase route to hydrophilic, glueable polytetrafluoroethylene.

    PubMed

    Roy, Amit K; Dendooven, Jolien; Deduytsche, Davy; Devloo-Casier, Kilian; Ragaert, Kim; Cardon, Ludwig; Detavernier, Christophe

    2015-02-28

    This communication reports an approach based on plasma-enhanced atomic layer deposition of aluminium oxide for the functionalization of polytetrafluoroethylene (PTFE or "Teflon") surfaces. Alternating exposure of PTFE to oxygen plasma and trimethylaluminium causes a permanent hydrophilic effect, and a more than 10-fold improvement of the "glueability" of PTFE to aluminium.

  3. ORGANIC SYNTHESES USING MICROWAVES AND SUPPORTED REAGENTS

    EPA Science Inventory

    Microwave-accelerated chemical syntheses under solvent-free conditions have witnessed an explosive growth. The technique has found widespread application predominantly exploiting the inexpensive unmodified household microwave (MW) ovens although the use of dedicated MW equipment...

  4. ORGANIC SYNTHESES USING MICROWAVES AND SUPPORTED REAGENTS

    EPA Science Inventory

    Microwave-accelerated chemical syntheses under solvent-free conditions have witnessed an explosive growth. The technique has found widespread application predominantly exploiting the inexpensive unmodified household microwave (MW) ovens although the use of dedicated MW equipment...

  5. Interface Electronic State Characterization of Plasma Enhanced Atomic Layer Deposited Dielectrics on GaN

    NASA Astrophysics Data System (ADS)

    Yang, Jialing

    In this dissertation, the interface chemistry and electronic structure of plasma-enhanced atomic layer deposited (PEALD) dielectrics on GaN are investigated with x-ray and ultraviolet photoemission spectroscopy (XPS and UPS). Three interrelated issues are discussed in this study: (1) PEALD dielectric growth process optimization, (2) interface electronic structure of comparative PEALD dielectrics on GaN, and (3) interface electronic structure of PEALD dielectrics on Ga- and N-face GaN. The first study involved an in-depth case study of PEALD Al2O3 growth using dimethylaluminum isopropoxide, with a special focus on oxygen plasma effects. Saturated and self-limiting growth of Al2O3 films were obtained with an enhanced growth rate within the PEALD temperature window (25--220 °C). The properties of Al2O3 deposited at various temperatures were characterized to better understand the relation between the growth parameters and film properties. In the second study, the interface electronic structures of PEALD dielectrics on Ga-face GaN films were measured. Five promising dielectrics (Al2O3, HfO2, SiO2, La2O 3, and ZnO) with a range of band gap energies were chosen. Prior to dielectric growth, a combined wet chemical and in-situ H 2/N2 plasma clean process was employed to remove the carbon contamination and prepare the surface for dielectric deposition. The surface band bending and band offsets were measured by XPS and UPS for dielectrics on GaN. The trends of the experimental band offsets on GaN were related to the dielectric band gap energies. In addition, the experimental band offsets were near the calculated values based on the charge neutrality level model. The third study focused on the effect of the polarization bound charge of the Ga- and N-face GaN on interface electronic structures. A surface pretreatment process consisting of a NH4OH wet chemical and an in-situ NH3 plasma treatment was applied to remove carbon contamination, retain monolayer oxygen coverage, and

  6. Preparation of highly photocatalytic active CdS/TiO{sub 2} nanocomposites by combining chemical bath deposition and microwave-assisted hydrothermal synthesis

    SciTech Connect

    Li, Li; Wang, Lili; Hu, Tianyu; Zhang, Wenzhi; Zhang, Xiuli; Chen, Xi

    2014-10-15

    CdS/TiO{sub 2} nanocomposites were prepared from Cd and Ti (1:1 M ratio) using cetyltrimethylammonium bromide by a two-step chemical bath deposition (CBD) and microwave-assisted hydrothermal synthesis (MAHS) method. A series of nanocomposites with different morphologies and activities were prepared by varying the reaction time in the MAHS (2, 4, and 6 h). The crystal structure, morphology, and surface physicochemical properties of the nanocomposites were characterized by X-ray diffraction, UV–visible diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and N{sub 2} adsorption–desorption measurements. The results show that the CdS/TiO{sub 2} nanocomposites were composed of anatase TiO{sub 2} and hexagonal CdS phases with strong absorption in the visible region. The surface morphologies changed slightly with increasing microwave irradiation time, while the Brunauer–Emmett–Teller surface area increased remarkably. The photocatalytic degradation of methyl orange (MO) was investigated under UV light and simulated sunlight irradiation. The photocatalytic activity of the CdS/TiO{sub 2} (6 h) composites prepared by the MAHS method was higher than those of CdS, P25, and other CdS/TiO{sub 2} nanocomposites. The CdS/TiO{sub 2} (6 h) nanocomposites significantly affected the UV and microwave-assisted photocatalytic degradation of different dyes. To elucidate the photocatalytic reaction mechanism for the CdS/TiO{sub 2} nanocomposites, controlled experiments were performed by adding different radical scavengers. - Graphical abstract: CdS/TiO{sub 2} nanocomposites were prepared using CTAB by CBD combined with MAHS method. In addition, with increasing microwave irradiation time, the morphology of CdS/TiO{sub 2} changed from popcorn-like to wedge-like structure. - Highlights: • The CdS/TiO{sub 2} was prepared by CBD combined with MAHS two-step method under CTAB. • The morphologies of as-samples were different with the time of

  7. Chemical characterization of PAN based carbon fibers produced by microwave assisted plasma (MAP) technology and effect of plasma treatment on carbon fiber surface and interphase with polymer matrix

    NASA Astrophysics Data System (ADS)

    Luo, Xiaoyu

    The first objective of this research was to chemically characterize the surface of conventional carbon fiber and carbon fiber produced by microwave assisted plasma (MAP) manufacturing process. The chemical composition and functional groups on the surface of the fibers were determined by X-ray photoelectron spectroscopy (XPS). The untreated unsized MAP carbon fibers were compared to untreated unsized conventional carbon fibers and showed a significant amount of oxygen. Comparison between treated unsized MAP carbon fiber and treated unsized conventional carbon fiber reveal a 100% enhancement of oxygen elemental concentration. Two plasma systems, remote applicator and atmospheric plasma were used to treat untreated unsized conventional carbon fiber. XPS results indicated that both systems have changed the chemical composition of carbon fiber surface. Oxygen-containing functional groups were found on carbon fiber surface after plasma treatment. Auger electron spectroscopy combining with chemical deritivazation was used to investigate the effect of morphological structure of carbon fiber surface on the placement of carboxyl groups. It was found that carboxyl groups were located preferentially in the valleys. A model of surface morphological structure of carbon fibers treated with plasma was proposed. Chemical bonding formed in the interphase between plasma treated carbon fiber and urethane was investigated using FTIR imaging. Directed evidence of formation of hydrogen bonding between carbon fiber and urethane was observed.

  8. Microwave-Accelerated Rapid, Chemical Oxidant-Free, Material-Independent Surface Chemistry of Poly(dopamine).

    PubMed

    Lee, Mihyun; Lee, Si-Hwa; Oh, Il-Kwon; Lee, Haeshin

    2017-01-01

    A simple strategy for the rapid preparation of multifunctional polydopamine (pDA) coatings is demonstrated. Microwave irradiation of the coating solution enables the formation of a ≈18 nm thick, genuine pDA coating in 15 min, which is ≈18 times faster than conventional coating. The acceleration effect results from the radical generation and temperature increase, which facilitate thermally accelerated radical polymerization of dopamine.

  9. Rapid adsorption of toxic Pb(II) ions from aqueous solution using multiwall carbon nanotubes synthesized by microwave chemical vapor deposition technique.

    PubMed

    Mubarak, Nabisab Mujawar; Sahu, Jaya Narayan; Abdullah, Ezzat Chan; Jayakumar, Natesan Subramanian

    2016-07-01

    Multiwall carbon nanotubes (MWCNTs) were synthesized using a tubular microwave chemical vapor deposition technique, using acetylene and hydrogen as the precursor gases and ferrocene as catalyst. The novel MWCNT samples were tested for their performance in terms of Pb(II) binding. The synthesized MWCNT samples were characterized using Fourier Transform Infrared (FT-IR), Brunauer, Emmett and Teller (BET), Field Emission Scanning Electron Microscopy (FESEM) analysis, and the adsorption of Pb(II) was studied as a function of pH, initial Pb(II) concentration, MWCNT dosage, agitation speed, and adsorption time, and process parameters were optimized. The adsorption data followed both Freundlich and Langmuir isotherms. On the basis of the Langmuir model, Qmax was calculated to be 104.2mg/g for the microwave-synthesized MWCNTs. In order to investigate the dynamic behavior of MWCNTs as an adsorbent, the kinetic data were modeled using pseudo first-order and pseudo second-order equations. Different thermodynamic parameters, viz., ∆H(0), ∆S(0) and ∆G(0) were evaluated and it was found that the adsorption was feasible, spontaneous and endothermic in nature. The statistical analysis revealed that the optimum conditions for the highest removal (99.9%) of Pb(II) are at pH5, MWCNT dosage 0.1g, agitation speed 160r/min and time of 22.5min with the initial concentration of 10mg/L. Our results proved that microwave-synthesized MWCNTs can be used as an effective Pb(II) adsorbent due to their high adsorption capacity as well as the short adsorption time needed to achieve equilibrium.

  10. Plasma-Enhanced Chemical Vapor Deposition of SiOx Films Using Electron Beam Generated Plasmas

    DTIC Science & Technology

    2009-09-28

    the films was large (> 130 nm/min), which implied a high porosity for all cases except for low TEOS flow (≤ 2 sccm) at the higher (300 °C) temperature...special relation to the substrate or e-beam. A total flow of 100 sccm was used in all cases . For the gas flows mentioned above, the individual flows...beam generated plasmas. In this case , molecular hydrogen, formed primarily by recombination of atomic hydrogen on system walls, will not be

  11. Glutamate biosensor based on carbon nanowalls grown using plasma enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Tomatsu, Masakazu; Hiramatsu, Mineo; Kondo, Hiroki; Hori, Masaru

    2015-09-01

    Carbon nanowalls (CNWs) are composed of few-layer graphene standing almost vertically on the substrate. Due to the large surface area of vertical nanographene network, CNWs draw attention as platform for electrochemical sensing, biosensing and energy conversion applications. In this work, CNWs were grown on nickel substrate using inductively coupled plasma with methane/Ar mixture. After the CNW growth, the surface of CNWs was oxidized using Ar atmospheric pressure plasma to obtain super-hydrophilic surface. For the biosensing application, the surface of CNWs was decorated with platinum (Pt) nanoparticles by the reduction of hydrogen hexachloroplatinate (IV) solution. The resultant Pt particle size was estimated to be 3-4 nm. From the XPS analysis, pure Pt existed without being oxidized on the CNW surface. Electrochemical surface area of the Pt catalyst was evaluated by cyclic voltammetry. Pt-decorated CNWs will be used as an electrode for electrochemical glutamate biosensing. L-glutamate is one of the most important in the mammalian central nervous system, playing a vital role in many physiological processes. Nanoplatform based on vertical nanographene offers great promise for providing a new class of nanostructured electrodes for electrochemical sensing.

  12. Patterning of Biomolecules on Plasma-Enhanced Chemical Vapor Deposited Generated Surfaces

    DTIC Science & Technology

    2006-01-01

    carboxylate surface of the quantum dot via EDC and subsequent coupling with cysteamine ligands. This was confirmed by IR spectroscopy (Supplemental...Material). Upon incubation of the cysteamine conjugated quantum dots with the thiol surface, coupling of quantum dots was observed by a...to NH2-SAM/pp-benzene by EDC (excitation ~ 400 nm). (B) Fluorescence image of quantum dots conjugated with cysteamine and coupled to SH-SAM/pp

  13. Plasma-Enhanced Chemical Vapor Deposition as a Method for the Deposition of Peptide Nanotubes

    DTIC Science & Technology

    2013-09-17

    45432, United States Distribution A: Approved for public release; distribution is unlimited. 2    Introduction: The unique ability of dipeptides ...Using physical vapor deposition (PVD) well-ordered assemblies of peptide nanotubes (PNTs) composed of dipeptide subunits are obtained on various...the PECVD deposition chamber with sublimation capability in the laboratory of Dr. Rajesh Naik (AFRL/RXAS) and conditions were modified for dipeptide

  14. Growth of carbon nanofibers in plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Denysenko, Igor; Ostrikov, Kostya; Tam, Eugene

    2008-10-01

    A theoretical model describing the plasma-assisted growth of carbon nanofibers with metal catalyst particles on top is proposed. Using the model, the plasma-related effects on the nanofiber growth parameters such us the surface diffusion growth rate, the effective carbon flux to the catalyst surface, the characteristic residence time and diffusion length of carbon on the catalyst surface, and the surface coverages, have been studied. It has been found how these parameters depend on the catalyst surface temperature and ion and etching gas fluxes to the catalyst surface. The optimum conditions under which a low-temperature plasma environment can benefit the carbon nanofiber growth are formulated. It has been also found how the plasma environment affects the temperature distribution over the length of the carbon nanofibers. Conditions when the temperature of the catalyst nanoparticles is higher than the temperature of the substrate holder are determined. The results here are in a good agreement with the available experimental data on the carbon nanofiber growth and can be used for optimizing synthesis of nanoassemblies in low-temperature plasma-assisted nanofabrication.

  15. Plasma enhanced chemical vapor deposition of ZrO2 thin films

    SciTech Connect

    Saravanan, Kolandaivelu

    1993-12-09

    Amorphous ZrO2 thin films were deposited in an inductively coupled PECVD system using a Zr β-diketonate, Zr(C11H19O2)4, as the precursor. The deposits were air annealed at 900C for 5 min to get pure, single phase, oriented, polycrystalline α-ZrO2. Feasibility of using 2 different types of reactors was investigated. The inductively heated horizontal reactor depositions at 600C had a lower deposition rate and the films were non-uniform in thickness with a columnar structure. The resistively heated vertical reactor depositions at 350C had a higher deposition rate and the films were more uniform in thickness with a fine grained microstructure. The statistical design was demonstrated as an effective technique to analyze the effect of process conditions on the rate of deposition and relative (h00) orientation. The factorial design was used to quantify the two responses in terms of the process variables and their mutual interactions. The statistical design for rate of deposition was found to correlate with the trends observed in classical design.

  16. Development of a Ge/GaAs HMT Technology Based on Plasma Enhanced Chemical Vapor Deposition

    DTIC Science & Technology

    1992-01-21

    channel and p-channel structures. Experiments have verified that the Si interlayer is in place and is not completely consumed by oxidation during...layer con- finement in the Ge portion of a Ge/Si-SiO,2 heterostructure/MIS device. The Ge MIS device utilizes an ultra-thin, crystalline Si interlayer ...layer, then the difference in these capacitances can be used to estimate 12 Si interlayer electrical behaviorI on p-type Ge ISMC-Si-0589-1-Ge 127.1

  17. Plasma-Enhanced Chemical Vapor Deposition of Beta-Tungsten, a Metastable Phase,

    DTIC Science & Technology

    the resistivity drops below 11 micron omega cm. Concomitant with this resistivity change is a phase change to alpha-W, the equilibrium, body - centered - cubic form. Additional keywords: reprint; and Army research.

  18. Microwave-assisted chemical pre-treatment of waste sorghum leaves: Process optimization and development of an intelligent model for determination of volatile compound fractions.

    PubMed

    Rorke, Daneal C S; Suinyuy, Terence N; Gueguim Kana, E B

    2017-01-01

    This study reports the profiling of volatile compounds generated during microwave-assisted chemical pre-treatment of sorghum leaves. Compounds including acetic acid (0-186.26ng/g SL), furfural (0-240.80ng/g SL), 5-hydroxymethylfurfural (HMF) (0-19.20ng/g SL) and phenol (0-7.76ng/g SL) were detected. The reducing sugar production was optimized. An intelligent model based on Artificial Neural Networks (ANNs) was developed and validated to predict a profile of 21 volatile compounds under novel pre-treatment conditions. This model gave R(2)-values of up to 0.93. Knowledge extraction revealed furfural and phenol exhibited high sensitivity to acid- and alkali concentration and S:L ratio, while phenol showed high sensitivity to microwave duration and intensity. Furthermore, furfural production was majorly dependent on acid concentration and fit a dosage-response relationship model with a 2.5% HCl threshold. Significant non-linearities were observed between pre-treatment conditions and the profile of various compounds. This tool reduces analytical costs through virtual analytical instrumentation, improving process economics.

  19. Comparative chemical composition of the essential oils obtained by microwave-assisted hydrodistillation and hydrodistillation from Agrimonia pilosa LEDEB. Collected in three different regions of China.

    PubMed

    Wang, Hongwu; Liu, Yanqing; Wei, Shoulian; Yan, Zijun; Jin, Xing

    2012-03-01

    Conventional hydrodistillation (HD) and microwave-assisted hydrodistillation (MAHD) were performed to obtain the volatile oils of Agrimonia pilosa Ledeb. harvested in three different regions of China, which were subsequently characterized by GC-FID and GC/MS analyses. Compared with HD, MAHD was advantageous in terms of energy savings and extraction time (60 vs. 240 min for MAHD and HD, resp.). The chemical composition varied among the different oils obtained, and the variations in the contents of the main constituents of the oils were irregular. Hence, these variations affected both the quantity and composition of the oils. The oil yields (0.15-0.21%) were affected by the method of extraction and the region of harvest, with the maximum amount of oil obtained by MAHD for the plants collected in Hubei (HB) and the minimum yield obtained by HD for the plants from Zhejing (ZJ). Hexadecanoic acid constituted the major compound of the essential oils, with the highest content found in the oil obtained by HD for plants from HB (41.18%) and the lowest one found in the oil obtained by MAHD from plants from ZJ (11.83%). Microwave irradiation did not adversely affect the composition of the essential oils. The findings show that MAHD is a modern, green, and fast technology. Copyright © 2012 Verlag Helvetica Chimica Acta AG, Zürich.

  20. Microwave-Assisted Olefin Metathesis

    NASA Astrophysics Data System (ADS)

    Nicks, François; Borguet, Yannick; Sauvage, Xavier; Bicchielli, Dario; Delfosse, Sébastien; Delaude, Lionel; Demonceau, Albert

    Since the first reports on the use of microwave irradiation to accelerate organic chemical transformations, a plethora of papers have been published in this field. In most examples, microwave heating has been shown to dramatically reduce reaction times, increase product yields, and enhance product purity by reducing unwanted side reactions compared to conventional heating methods. The present contribution aims at illustrating the advantages of this technology in olefin metathesis and, when data are available, at comparing microwave-heated and conventionally heated experiments

  1. Low-temperature ({<=}200 Degree-Sign C) plasma enhanced atomic layer deposition of dense titanium nitride thin films

    SciTech Connect

    Samal, Nigamananda; Du Hui; Luberoff, Russell; Chetry, Krishna; Bubber, Randhir; Hayes, Alan; Devasahayam, Adrian

    2013-01-15

    Titanium nitride (TiN) has been widely used in the semiconductor industry for its diffusion barrier and seed layer properties. However, it has seen limited adoption in other industries in which low temperature (<200 Degree-Sign C) deposition is a requirement. Examples of applications which require low temperature deposition are seed layers for magnetic materials in the data storage (DS) industry and seed and diffusion barrier layers for through-silicon-vias (TSV) in the MEMS industry. This paper describes a low temperature TiN process with appropriate electrical, chemical, and structural properties based on plasma enhanced atomic layer deposition method that is suitable for the DS and MEMS industries. It uses tetrakis-(dimethylamino)-titanium as an organometallic precursor and hydrogen (H{sub 2}) as co-reactant. This process was developed in a Veeco NEXUS Trade-Mark-Sign chemical vapor deposition tool. The tool uses a substrate rf-biased configuration with a grounded gas shower head. In this paper, the complimentary and self-limiting character of this process is demonstrated. The effects of key processing parameters including temperature, pulse time, and plasma power are investigated in terms of growth rate, stress, crystal morphology, chemical, electrical, and optical properties. Stoichiometric thin films with growth rates of 0.4-0.5 A/cycle were achieved. Low electrical resistivity (<300 {mu}{Omega} cm), high mass density (>4 g/cm{sup 3}), low stress (<250 MPa), and >85% step coverage for aspect ratio of 10:1 were realized. Wet chemical etch data show robust chemical stability of the film. The properties of the film have been optimized to satisfy industrial viability as a Ruthenium (Ru) preseed liner in potential data storage and TSV applications.

  2. Plasma-enhanced synthesis of bioactive polymeric coatings from monoterpene alcohols: a combined experimental and theoretical study.

    PubMed

    Bazaka, Kateryna; Jacob, Mohan V; Truong, Vi Khanh; Wang, Feng; Pushpamali, Wickrama Arachchilage Anoja; Wang, James Y; Ellis, Amanda V; Berndt, Christopher C; Crawford, Russell J; Ivanova, Elena P

    2010-08-09

    This paper describes the synthesis and characterization of a novel organic polymer coating for the prevention of the growth of Pseudomonas aeruginosa on the solid surface of three-dimensional objects. Substrata were encapsulated with polyterpenol thin films prepared from terpinen-4-ol using radio frequency plasma enhanced chemical vapor deposition. Terpinen-4-ol is a constituent of tea tree oil with known antibacterial properties. The influence of deposition power on the chemical structure, surface composition, and ultimately the antibacterial inhibitory activity of the resulting polyterpenol thin films was studied using X-ray photoelectron spectroscopy (XPS), water contact angle measurement, atomic force microscopy (AFM), and 3-D interactive visualization and statistical approximation of the topographic profiles. The experimental results were consistent with those predicted by molecular simulations. The extent of bacterial attachment and extracellular polymeric substances (EPS) production was analyzed using scanning electron microscopy (SEM) and confocal scanning laser microscopy (CSLM). Polyterpenol films deposited at lower power were particularly effective against P. aeruginosa due to the preservation of original terpinen-4-ol molecules in the film structure. The proposed antimicrobial and antifouling coating can be potentially integrated into medical and other clinically relevant devices to prevent bacterial growth and to minimize bacteria-associated adverse host responses.

  3. Microwave Plasma Chemical Vapor Deposition of Nano-Structured Sn/C Composite Thin-Film Anodes for Li-ion Batteries

    SciTech Connect

    Stevenson, Cynthia; Marcinek, M.; Hardwick, L.J.; Richardson, T.J.; Song, X.; Kostecki, R.

    2008-02-01

    In this paper we report results of a novel synthesis method of thin-film composite Sn/C anodes for lithium batteries. Thin layers of graphitic carbon decorated with uniformly distributed Sn nanoparticles were synthesized from a solid organic precursor Sn(IV) tert-butoxide by a one step microwave plasma chemical vapor deposition (MPCVD). The thin-film Sn/C electrodes were electrochemically tested in lithium half cells and produced a reversible capacity of 440 and 297 mAhg{sup -1} at C/25 and 5C discharge rates, respectively. A long term cycling of the Sn/C nanocomposite anodes showed 40% capacity loss after 500 cycles at 1C rate.

  4. Effects of solvent-free microwave extraction on the chemical composition of essential oil of Calamintha nepeta (L.) Savi compared with the conventional production method.

    PubMed

    Riela, Serena; Bruno, Maurizio; Formisano, Carmen; Rigano, Daniela; Rosselli, Sergio; Saladino, Maria Luisa; Senatore, Felice

    2008-04-01

    The essential oil of Calamintha nepeta has been obtained by solvent-free microwave extraction (SFME) and by classical hydrodistillation (HD). A comparative qualitative-quantitative study on the composition of the oils was carried out. A total of 38 compounds, constituting 97.6% of the oil, were identified in the oil obtained by SFME, whereas 46 compounds, representing 95.4% of the oil, were characterized in the HD oil. SFME-distilled oil is richer in lightly oxygenated monoterpenes (LOM) than HD oil. It also has a higher amount of sesquiterpenes and a lower quantity of hydrocarbon monoterpenes. HD oil seems to be affected by chemical changes more than SFME oil.

  5. Deposition and Characterization of Nanocrystalline Diamond Films on Mirror-Polished Si Substrate by Biased Enhanced Microwave Plasma Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Soga, T.; Sharda, T.; Jimbo, T.; Umeno, M.

    Hard and smooth nanocrystalline diamond (NCD) thin films were deposited on polished silicon substrates by biased enhanced growth in microwave plasma chemical vapor deposition. The films deposited with varying the methane concentration and biasing voltage were characterized by Raman spectroscopy, nano-indenter, x-ray diffraction and atomic force microscopy. Stress in the films increases with decreasing methane concentration in the gas-phase and with increasing biasing. The adhesion between NCD film and Si substrate is very strong sustaining the compressive stress as high as high as 85 GPa. It was hypothesized that hydrogen content of the films and graphitic content of the films are responsible in generating stress. The hardness is well correlated with the Raman peak intensity ratio of NCD peak to G peak.

  6. A systematic study of the relationship among the morphological, structural and photoelectrochemical properties of ZnO nanorods grown using the microwave chemical bath deposition method

    NASA Astrophysics Data System (ADS)

    Oh, Sungjin; Ryu, Hyukhyun; Lee, Won-Jae

    2017-08-01

    In this study, zinc oxide (ZnO) nanostructures were grown on a ZnO seed layer/fluorine-doped tin oxide (FTO) substrate for different growth durations ranging from 5 to 40 min using the microwave chemical bath deposition method. We studied the effect of growth duration on the morphological, structural, optical and photoelectrochemical properties of the ZnO nanostructures. From this study, we found that the photoelectrochemical properties of the ZnO nanostructures were largely affected by their morphological and structural properties. As a result, we obtained the highest photocurrent density of 0.46 mA/cm2 (at 1.5 V vs. SCE) from the sample grown for 30 min.

  7. Optimization of biodiesel production process from soybean oil using the sodium potassium tartrate doped zirconia catalyst under Microwave Chemical Reactor.

    PubMed

    Li, Yihuai; Ye, Bin; Shen, Jiaowen; Tian, Zhen; Wang, Lijun; Zhu, Luping; Ma, Teng; Yang, Dongya; Qiu, Fengxian

    2013-06-01

    A solid base catalyst was prepared by the sodium potassium tartrate doped zirconia and microwave assisted transesterification of soybean oil was carried out for the production of biodiesel. It was found that the catalyst of 2.0(n(Na)/n(Zr)) and calcined at 600°C showed the optimum activity. The base strength of the catalysts was tested by the Hammett indicator method, and the results showed that the fatty acid methyl ester (FAME) yield was related to their total basicity. The catalyst was also characterized by FTIR, TGA, XRD and TEM. The experimental results showed that a 2.0:1 volume ratio of methanol to oil, 65°C reaction temperature, 30 min reaction time and 10 wt.% catalyst amount gave the highest the yield of biodiesel. Compared to conventional method, the reaction time of the way of microwave assisted transesterification was shorter. The catalyst had longer lifetime and maintained sustained activity after being used for four cycles.

  8. Numerical analysis of a mixture of Ar/NH{sub 3} microwave plasma chemical vapor deposition reactor

    SciTech Connect

    Li Zhi; Zhao Zhen; Li Xuehui

    2012-06-01

    A two-dimensional fluid model has been used to investigate the properties of plasma in Ar/NH{sub 3} microwave electron cyclotron resonance discharge at low pressure. The electromagnetic field model solved by the three-dimensional Simpson method is coupled to a fluid plasma model. The finite difference method was employed to discrete the governing equations. 40 species (neutrals, radicals, ions, and electrons) are consisted in the model. In total, 75 electron-neutral, 43 electron-ion, 167 neutral-neutral, 129 ion-neutral, 28 ion-ion, and 90 3-body reactions are used in the model. According to the simulation, the distribution of the densities of the considered plasma species has been showed and the mechanisms of their variations have been discussed. It is found that the main neutrals (Ar*, Ar**, NH{sub 3}{sup *}, NH, H{sub 2}, NH{sub 2}, H, and N{sub 2}) are present at high densities in Ar/NH{sub 3} microwave electron cyclotron resonance discharge when the mixing ratio of Ar/NH{sub 3} is 1:1 at 20 Pa. The density of NH is more than that of NH{sub 2} atom. And NH{sub 3}{sup +} are the most important ammonia ions. But the uniformity of the space distribution of NH{sub 3}{sup +} is lower than the other ammonia ions.

  9. Plasma enhanced atomic layer batch processing of aluminum doped titanium dioxide

    SciTech Connect

    Lehnert, Wolfgang; Ruhl, Guenther; Gschwandtner, Alexander

    2012-01-15

    Among many promising high-k dielectrics, TiO{sub 2} is an interesting candidate because of its relatively high k value of over 40 and its easy integration into existing semiconductor manufacturing schemes. The most critical issues of TiO{sub 2} are its low electrical stability and its high leakage current density. However, doping TiO{sub 2} with Al has shown to yield significant improvement of layer quality on Ru electrodes [S. K. Kim et al., Adv. Mater. 20, 1429 (2008)]. In this work we investigated if atomic layer deposition (ALD) of Al doped TiO{sub 2} is feasible in a batch system. Electrical characterizations were done using common electrode materials like TiN, TaN, or W. Additionally, the effect of plasma enhanced processing in this reactor was studied. For this investigation a production batch ALD furnace has been retrofitted with a plasma source which can be used for post deposition anneals with oxygen radicals as well as for directly plasma enhanced ALD. After evaluation of several Ti precursors a deposition process for AlTiO{sub x} with excellent film thickness and composition uniformity was developed. The effects of post deposition anneals, Al{sub 2}O{sub 3} interlayers between electrode and TiO{sub 2}, Al doping concentration, plasma enhanced deposition and electrode material type on leakage current density are shown. An optimized AlTiO{sub x} deposition process on TaN electrodes yields to leakage current density of 5 x 10{sup -7} A/cm{sup 2} at 2 V and k values of about 35. Thus, it could be demonstrated that a plasma enhanced batch ALD process for Al doped TiO{sub 2} is feasible with acceptable leakage current density on a standard electrode material.

  10. Plasma-Enhanced Deposition of Silicon Nitride from SiH4-N2 Mixture

    NASA Astrophysics Data System (ADS)

    Katoh, Kazuhisa; Yasui, Masaru; Watanabe, Hideo

    1983-05-01

    Excellent silicon nitride films which can be used as the gate insulator of an a-Si FET are fabricated by RF glow-discharge of SiH4-N2-H2 gas mixtures. Resistivity of larger than 1× 1016 Ω\\cdotcm and breakdown strength of 6× 106 V/cm are realized. The optimum deposition conditions are evaluated and briefly discussed in connection with mechanisms of the plasma-enhanced deposition.

  11. A preliminary study on numerical simulation of microwave heating process for chemical reaction and discussion of hotspot and thermal runaway phenomenon

    NASA Astrophysics Data System (ADS)

    Zhao, Xiang; Huang, Kama; Yan, Liping; Yao, Yuan

    2009-04-01

    The nonlinear process of microwave heating chemical reaction is studied by means of numerical simulation. Especially, the variation of temperature in terms of space and time, as well as the hotspot and thermal runaway phenomena are discussed. Suppose the heated object is a cylinder and the incident electromagnetic (EM) wave is plane wave, the problem turns out to be a coupling calculation of 2D multi-physical fields. The integral equation of EM field is solved using the method of moment (MoM) and the thermal conduction equation is solved using a semi-analysis method. Moreover, a method to determine the equivalent complex permittivity of reactant under the heating is presented in order to perform the calculation. The numerical results for water and a dummy chemical reaction ( A) show that the hotspot is a ubiquitous phenomenon in microwave heating process. When the radius of the heated object is small, the highest temperature occurs somewhere inside the object due to the concentration of the EM wave. While the radius increases to a certain degree, the highest temperature occurs somewhere close to the surface due to the skin effect, and the whole high temperature area shows crescent-shaped. That is in accordance with basic physical principles. If the radius is kept the same in the heating process, the hotspot position of water does not change, while that of reaction A with several radius values varies. For either water or A, the thermal runaway phenomenon in which small difference of radius results in large difference of highest temperature, occurs easily when the radius is small. On the contrary, it is not evident when the radius is large. Moreover, it is notable that the highest temperature in water shows oscillating decreasing trend with the increase of radius, but in reaction A almost decreases monotonously. Further study should be performed to determine if this difference is only an occasional occurrence.

  12. GREENER SYNTHETIC TRANSFORMATIONS USING MICROWAVES

    EPA Science Inventory

    Microwave irradiation has been used for a variety of organic transformations wherein chemical reactions are expedited because of selective adsorption of microwave (MW) energy by polar molecules, non-polar molecules being inert to the MW dielectric loss. The MW application under s...

  13. GREENER SYNTHETIC TRANSFORMATIONS USING MICROWAVES

    EPA Science Inventory

    Microwave irradiation has been used for a variety of organic transformations wherein chemical reactions are expedited because of selective adsorption of microwave (MW) energy by polar molecules, non-polar molecules being inert to the MW dielectric loss. The MW application under s...

  14. Recording Spatially Resolved Plasma Parameters in Microwave-Driven Plasmas

    NASA Astrophysics Data System (ADS)

    Gerhard, Franz; Florian, Schamberger; Igor, Krstev; Stefan, Umrath

    2013-01-01

    In an almost cubical reactor 90 l in volume which is intended to deposit organic polymers by plasma-enhanced chemical vapor deposition (PECVD), microwave power is coupled into the volume via a quartz window which extends to approximately 1/10 of the sidewall area. Since the plasma is excited locally, plasma parameters like electron temperature and plasma density are expected to exhibit a spatial variation. The compilation of these plasma quantities has been accomplished with a bendable single Langmuir probe. To isolate the tungsten wire against its grounded housing tube, it was coated with polyparylene. After having compared this construction with our Langmuir probe, which has been now in use for more than a decade, we have taken data of more than half the volume of the reactor with argon and have found a definitive radial inhomogenity for all plasma parameters. To investigate whether this conduct can be determined applying optical emission spectroscopy, we improved our spectrometer which had been used for endpoint detection purposes and plasma diagnostics in chlorine-containing ambients where we could detect also a spatial dependence. This behavior is discussed in terms of Lieberman's global model.

  15. Buckyball microwave plasmas: Fragmentation and diamond-film growth

    SciTech Connect

    Gruen, D.M.; Liu, Shengzhong; Krauss, A.R.; Pan, Xianzheng

    1993-08-01

    Microwave discharges (2.45 GHz) have been generated in C{sub 60}-containing Ar produced by flowing Ar over fullerene-containing soot. Optical spectroscopy shows that the spectrum is dominated by the d{sup 3}{Pi}g-a{sup 3}{Pi}u Swan bands of C{sub 2} and particularly the {Delta}v = {minus}2, {minus}1, 0, +1, and +2 sequences. These results give direct evidence that C{sub 2} is one of the products of C{sub 60} fragmentation brought about, at least in part, by collisionally induced dissociation (CID). C{sub 60} has been used as a precursor in a plasma-enhanced chemical vapor deposition (PECVD) experiment to grow diamond-thin films. The films, grown in an Ar/H{sub 2} gas mixture (0.14% carbon content, 100 Torr, 20 sccm Ar, 4 sccm H{sub 2}, 1500 W, 850{degree}C substrate temperature), were characterized with SEM, XRD, and Raman spectroscopy. Growth rate was found to be {approx} 0.6 {mu}/hr. Assuming a linear dependence on carbon concentration, a growth rate at least six times higher than commonly observed using methane as a precursor, would be predicted at a carbon content of 1% based on C{sub 60}. Energetic and mechanistic arguments are advanced to rationalize this result based on C{sub 2} as the growth species.

  16. Characterization of amorphous SIC:H thin films grown by RF plasma enhanced CVD on annealing temperature

    NASA Astrophysics Data System (ADS)

    Park, M. G.; Choi, W. S.; Boo, J.-H.; Kim, Y. T.; Yoon, D. H.; Hong, B.

    2002-06-01

    n this work, we investigated the dependence of optical and electrical properties of hydrogenated amorphous silicon carbide (a-SiCa:H) films on annealing temperature (T_a) and radio frquency (RF) power. The substrate temperature (T_s was 250 °C, the RF power was varied from 30 W to 400 W, and the range of T_s, was from 400 °C to 600 °C. The a-SiC:H films were deposited by using PECVD (plasma enhanced chemical vapor deposition) system on Coming glass and p-type Si (100) wafer with a SiH4+CH4 gas tnudiue. The experimental results have shown that the optical band gap energy (E_g) of the aSiC:H thin films changed little with the annealing temperature while Eg increased with the RF power. The Raman spectnrn of the thin films annealed at high temperatures showed that graphitization of carbon clusters and rnicrocrystalline silicon occurs. The current voltage characteristics have shown good electrical properties in relation to the annealed films.

  17. Large-scale synthesis of uniform hexagonal boron nitride films by plasma-enhanced atomic layer deposition

    PubMed Central

    Park, Hamin; Kim, Tae Keun; Cho, Sung Woo; Jang, Hong Seok; Lee, Sang Ick; Choi, Sung-Yool

    2017-01-01

    Hexagonal boron nitride (h-BN) has been previously manufactured using mechanical exfoliation and chemical vapor deposition methods, which make the large-scale synthesis of uniform h-BN very challenging. In this study, we produced highly uniform and scalable h-BN films by plasma-enhanced atomic layer deposition, which were characterized by various techniques including atomic force microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray diffraction. The film composition studied by X-ray photoelectron spectroscopy and Auger electron spectroscopy corresponded to a B:N stoichiometric ratio close to 1:1, and the band-gap value (5.65 eV) obtained by electron energy loss spectroscopy was consistent with the dielectric properties. The h-BN-containing capacitors were characterized by highly uniform properties, a reasonable dielectric constant (3), and low leakage current density, while graphene on h-BN substrates exhibited enhanced electrical performance such as the high carrier mobility and neutral Dirac voltage, which resulted from the low density of charged impurities on the h-BN surface. PMID:28054603

  18. Large-scale synthesis of uniform hexagonal boron nitride films by plasma-enhanced atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Park, Hamin; Kim, Tae Keun; Cho, Sung Woo; Jang, Hong Seok; Lee, Sang Ick; Choi, Sung-Yool

    2017-01-01

    Hexagonal boron nitride (h-BN) has been previously manufactured using mechanical exfoliation and chemical vapor deposition methods, which make the large-scale synthesis of uniform h-BN very challenging. In this study, we produced highly uniform and scalable h-BN films by plasma-enhanced atomic layer deposition, which were characterized by various techniques including atomic force microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray diffraction. The film composition studied by X-ray photoelectron spectroscopy and Auger electron spectroscopy corresponded to a B:N stoichiometric ratio close to 1:1, and the band-gap value (5.65 eV) obtained by electron energy loss spectroscopy was consistent with the dielectric properties. The h-BN-containing capacitors were characterized by highly uniform properties, a reasonable dielectric constant (3), and low leakage current density, while graphene on h-BN substrates exhibited enhanced electrical performance such as the high carrier mobility and neutral Dirac voltage, which resulted from the low density of charged impurities on the h-BN surface.

  19. Chemically coupled microwave and ultrasonic pre-hydrolysis of pulp and paper mill waste-activated sludge: effect on sludge solubilisation and anaerobic digestion.

    PubMed

    Tyagi, Vinay Kumar; Lo, Shang-Lien; Rajpal, Ankur

    2014-05-01

    The effects of alkali-enhanced microwave (MW; 50-175 °C) and ultrasonic (US) (0.75 W/mL, 15-60 min) pretreatments, on solubilisation and subsequent anaerobic digestion efficiency of pulp and paper mill waste-activated sludge, were investigated. Improvements in total chemical oxygen demand and volatile suspended solids (VSS) solubilisation were limited to 33 and 39 % in MW pretreatment only (175 °C). It reached 78 and 66 % in combined MW-alkali pretreatment (pH 12 + 175 °C), respectively. Similarly, chemical oxygen demand and VSS solubilisation were 58 and 37 % in US pretreatment alone (60 min) and it improved by 66 and 49 % after US-alkali pretreatment (pH 12 + 60 min), respectively. The biogas yield for US 60 min-alkali (pH 12)-pretreated sludge was significantly improved by 47 and 20 % over the control and US 60 reactors, respectively. The biogas generation for MW (150 °C)-alkali (pH 12)-pretreated sludge was only 6.3 % higher than control; however, it was 8.3 % lower than the MW (150 °C) reactor, which was due to the inhibition of anaerobic activity under harsh thermal-alkali treatment condition.

  20. Trace determination of Hg together with As, Sb, Se by miniaturized optical emission spectrometry integrated with chemical vapor generation and capacitively coupled argon microwave miniplasma discharge

    NASA Astrophysics Data System (ADS)

    Matusiewicz, Henryk; Ślachciński, Mariusz

    2017-07-01

    A miniaturized optical emission spectrometer (OES) with capacitively coupled argon microwave microplasma (μCMP) as and excitation source and chemical vapor generation (CVG) for sample introduction was constructed for the determination of trace Hg, As, Sb and Se. The applied method enabled simultaneous determination of hydride-forming elements (As, Sb, Se) and volatile Hg. Mercury cold vapor and the hydride volatile species of As, Sb and Se were generated when standard or sample solutions were separated from the liquid phase for transport to the capacitively coupled microwave microplasma and detection of their atomic emission. A univariate approach and the simplex optimization procedure were used to achieve optimized conditions and derive analytical figures of merit. The experimental concentration detection limits (LODs) for simultaneous determination, calculated as the concentration giving a signal equal to three times of the standard deviation of the blank (LOD, 3σblank criterion, peak height) were 3.0, 1.4, 1.5 and 3.8 ng mL- 1 for Hg, As, Sb and Se, respectively. The method was validated by the analysis of three Certified Reference Materials (NIST 2711, NRCC DOLT-2, NIST 1643e) of different matrix composition and by the standard addition technique. The method offers relatively good precision (RSD ranged from 5% to 8%) for microsampling (200 μL) analysis. The measured of contents of elements in certified reference materials were in good agreement with the certified values (Hg 1.99-6.25 μg g- 1, As 16.6-105 μg g- 1, Sb 19.4-56.88 μg g- 1, Se 1.52-11.68 μg g- 1), according to the Student t-test, for a confidence level of 95%.

  1. Improved film quality of plasma enhanced atomic layer deposition SiO{sub 2} using plasma treatment cycle

    SciTech Connect

    Kim, Haiwon; Chung, Ilsub; Kim, Seokyun; Shin, Seungwoo; Jung, Wooduck; Hwang, Ryong; Jeong, Choonsik; Hwang, Hanna

    2015-01-15

    Chemical, physical, and electrical characteristics of high quality silicon dioxide (SiO{sub 2}) films grown using low temperature plasma enhanced atomic layer deposition (PE-ALD) have been investigated as a buffer layer for three dimensional vertical NAND flash memory devices. The comparative angle resolved x-ray photoelectron spectroscopy studies show the plasma treatment cycle causes to shift the core level binding energy (chemical shifts) in the SiO{sub 2} film. The wet etch rates with respect to plasma treatment cycle times were varied due to curing of the SiO{sub 2} network defects by Ar{sup +} ions and oxygen radicals. It is assumed that the angle between the bonds linking SiO{sub 4} tetrahedra is a critical point understanding the variation in wet etch rate of SiO{sub 2}. The features of wet etch rate of low temperature high quality SiO{sub 2} demonstrated lower than high temperature low-pressure chemical vapor deposition (LP-CVD) SiO{sub 2} values. In addition, the better step-coverage compared to that of the LP-CVD SiO{sub 2} film was achieved from the deep trench structure having the 20:1 aspect ratio. PE-ALD SiO{sub 2} with plasma treatment cycle showed excellent I–V properties with higher breakdown voltage compared to LP-CVD SiO{sub 2} and similar to the thermal SiO{sub 2} carrier transport plot.

  2. Comparative Study of Solid-Phase Crystallization of Amorphous Silicon Deposited by Hot-Wire CVD, Plasma-Enhanced CVD, and Electron-Beam Evaporation

    SciTech Connect

    Stradins, P.; Kunz, O.; Young, D. L.; Yan, Y.; Jones, K. M.; Xu, Y.; Reedy, R. C.; Branz, H. M.; Aberle, A. G.; Wang, Q.

    2007-01-01

    Solid-phase crystallization (SPC) rates are compared in amorphous silicon films prepared by three different methods: hot-wire chemical vapor deposition (HWCVD), plasma-enhanced chemical vapor deposition (PECVD), and electron-beam physical vapor deposition (e-beam). Random SPC proceeds approximately 5 and 13 times slower in PECVD and e-beam films, respectively, as compared to HWCVD films. Doping accelerates random SPC in e-beam films but has little effect on the SPC rate of HWCVD films. In contrast, the crystalline growth front in solid-phase epitaxy experiments propagates at similar speed in HWCVD, PECVD, and e-beam amorphous Si films. This strongly suggests that the observed large differences in random SPC rates originate from different nucleation rates in these materials while the grain growth rates are relatively similar. The larger grain sizes observed for films that exhibit slower random SPC support this suggestion.

  3. Optimization of preparation of activated carbon from cotton stalk by microwave assisted phosphoric acid-chemical activation.

    PubMed

    Deng, Hui; Zhang, Genlin; Xu, Xiaolin; Tao, Guanghui; Dai, Jiulei

    2010-10-15

    The preparation of activated carbon (AC) from cotton stalk was investigated in this paper. Orthogonal array experimental design method was used to optimize the preparation of AC using microwave assisted phosphoric acid. Optimized parameters were radiation power of 400 W, radiation time of 8 min, concentration of phosphoric acid of 50% by volume and impregnation time of 20 h, respectively. The surface characteristics of the AC prepared under optimized condition were examined by pore structure analysis, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). Pore structure analysis shows that mecropores constitute more of the porosity of the prepared AC. Compared to cotton stalk, different functionalities and morphology on the carbon surfaces were formed in the prepared process. The adsorption capacity of the AC was also investigated by removing methylene blue (MB) in aqueous solution. The equilibrium data of the adsorption was well fitted to the Langmuir isotherm. The maximum adsorption capacity of MB on the prepared AC is 245.70 mg/g. The adsorption process follows the pseudo-second-order kinetic model.

  4. Probing Chemical Dynamics with High Resolution Spectroscopy: Chirped-Pulse Fourier-Transform Microwave Spectroscopy Coupled with a Hyperthermal Source

    NASA Astrophysics Data System (ADS)

    Kidwell, Nathanael M.; Vara, Vanesa Vaquero; Mehta-Hurt, Deepali N.; Korn, Joseph A.; Dian, Brian C.; Zwier, Timothy S.

    2013-06-01

    Chirped-pulse Fourier-transform microwave (CP-FTMW) spectroscopy has proven to be a well-suited technique for the rapid study and spectral identification of molecular species due to its ultra-broadband capability and excellent specificity to molecular structure from high-resolution rotational transitions. This talk will describe initial results from combining CP-FTMW detection with a hyperthermal nozzle source. This source has the advantage of producing traditionally high thermal product densities in a pulsed supersonic expansion with a short contact time compared to conventional pyrolysis. Used in tandem, CP-FTMW spectroscopy and the hyperthermal nozzle in a supersonic expansion is a powerful method that can produce and detect changes in conformation and isomer populations, and characterize important intermediates on the reaction surface of a precursor. In particular, we show its utility to provide insight into the unimolecular decomposition pathways of model lignin compounds and alternative biofuels. Preliminary results will be discussed including spectroscopic evidence for formation of cyclopentadienone in the pyrolysis of a lignin derivative guaiacol (o-methoxyphenol).

  5. Nitrogen plasma instabilities and the growth of silicon nitride by electron cyclotron resonance microwave plasma chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Pool, F. S.

    1997-03-01

    Nitrogen plasma instabilities have been identified through fluctuations in the ion current density and substrate floating potential. The behavior of the plasma instabilities was found to be confined to the pressure regime 0.9 mTorrmicrowave plasma deposited silicon nitride films for pressures above the underdense to overdense transition at 1.0 mTorr.

  6. Synthesis via a Microwave-Assisted Wet Chemical Method and Characterization of Bi2Te3 with Various Morphologies

    NASA Astrophysics Data System (ADS)

    Chen, Song; Cai, Kefeng; Shen, Shirley

    2016-03-01

    Bi2Te3 with various morphologies, such as microrods, nanoplates, and nanoflowers, has been successfully fabricated by a microwave-assisted method in ethylene glycol solution without any surfactant. The structures and morphologies of the obtained products have been characterized by powder x-ray diffraction and field-emission scanning electron microscopy. Based on time-dependent experiments, a possible formation mechanism of the Bi2Te3 has been proposed. The concentration of KOH in the solution controls the rate of the disproportionation reaction of Te and plays an important role in the formation of the various morphologies of Bi2Te3. The electrical properties of bulk Bi2Te3 materials obtained by cold pressing and then vacuum heat treatment of the Bi2Te3 nanostructures with various morphologies have also been investigated. The highest power factor among the studied samples, ˜17.3 μW cm-1 K-2, was achieved using Bi2Te3 nanoflowers.

  7. Role of plasma enhanced atomic layer deposition reactor wall conditions on radical and ion substrate fluxes

    SciTech Connect

    Sowa, Mark J.

    2014-01-15

    Chamber wall conditions, such as wall temperature and film deposits, have long been known to influence plasma source performance on thin film processing equipment. Plasma physical characteristics depend on conductive/insulating properties of chamber walls. Radical fluxes depend on plasma characteristics as well as wall recombination rates, which can be wall material and temperature dependent. Variations in substrate delivery of plasma generated species (radicals, ions, etc.) impact the resulting etch or deposition process resulting in process drift. Plasma enhanced atomic layer deposition is known to depend strongly on substrate radical flux, but film properties can be influenced by other plasma generated phenomena, such as ion bombardment. In this paper, the chamber wall conditions on a plasma enhanced atomic layer deposition process are investigated. The downstream oxygen radical and ion fluxes from an inductively coupled plasma source are indirectly monitored in temperature controlled (25–190 °C) stainless steel and quartz reactors over a range of oxygen flow rates. Etch rates of a photoresist coated quartz crystal microbalance are used to study the oxygen radical flux dependence on reactor characteristics. Plasma density estimates from Langmuir probe ion saturation current measurements are used to study the ion flux dependence on reactor characteristics. Reactor temperature was not found to impact radical and ion fluxes substantially. Radical and ion fluxes were higher for quartz walls compared to stainless steel walls over all oxygen flow rates considered. The radical flux to ion flux ratio is likely to be a critical parameter for the deposition of consistent film properties. Reactor wall material, gas flow rate/pressure, and distance from the plasma source all impact the radical to ion flux ratio. These results indicate maintaining chamber wall conditions will be important for delivering consistent results from plasma enhanced atomic layer deposition

  8. The Structure and Molecular Parameters of Camphene Determined by Fourier Transform Microwave Spectroscopy and Quantum Chemical Calculations

    NASA Astrophysics Data System (ADS)

    Neeman, Elias M.; Dréan, Pascal; Huet, T. R.

    2016-06-01

    The emission of volatile organic compounds, from plants has strong revelance for plant physiology, plant ecology and atmospheric chemistry. Camphene (C10H16) is a bicyclic monoterpene which is emitted in the atmosphere by biogenic sources. The structure of the unique stable conformer was optimized using density functional theory and ab initio calculations. The rotational spectrum of camphene was recorded in a supersonic jet expansion with a Fourier transform microwave spectrometer over the range 2-20 GHz. Signals from the parent species and from the ten 13C isotopomers were observed in natural abundance. The rotational and centrifugal distortion parameters were fitted to a Watson's Hamiltonian in the A-reduction. A magnetic hyperfine structure associated with the pairs of hydrogen nuclei in the methylene groups was observed and modeled.The rotational constants coupled to the equilibrium structure calculations were used to determine the r_0 and the r_m(1) gas-phase geometries of the carbon skeleton. The present work provides the first spectroscopic characterization of camphene in the gas phase and these results are also relevant for ozonolysis kinetics study through Criegee intermediates. R. Baraldi, F. Rapparini, O. Facini, D. Spano and P. Duce, Journal of Mediterranean Ecology, Vol.6, No.1, (2005). A. Bracho-Nunez, N. M. Knothe, S. Welter, M. Staudt, W. R. Costa, M. A. R. Liberato, M. T. F. Piedade, and J. Kesselmeier Biogeosciences, 10, 5855-5873, (2013). Minna Kivimäenpää, Narantsetseg Magsarjav, Rajendra Ghimire, Juha-Matti Markkanen, Juha Heijari, Martti Vuorinen and Jarmo K. Holopainen, Atmospheric Environment, 60, 477-485, (2012). R.C. de M. Oliveira and G. F. Bauerfeldt, J. Phys. Chem. A, 119 2802-2812 (2015)

  9. Microwave detector

    DOEpatents

    Meldner, Heiner W.; Cusson, Ronald Y.; Johnson, Ray M.

    1986-01-01

    A microwave detector (10) is provided for measuring the envelope shape of a microwave pulse comprised of high-frequency oscillations. A biased ferrite (26, 28) produces a magnetization field flux that links a B-dot loop (16, 20). The magnetic field of the microwave pulse participates in the formation of the magnetization field flux. High-frequency insensitive means (18, 22) are provided for measuring electric voltage or current induced in the B-dot loop. The recorded output of the detector is proportional to the time derivative of the square of the envelope shape of the microwave pulse.

  10. Microwave detector

    DOEpatents

    Meldner, H.W.; Cusson, R.Y.; Johnson, R.M.

    1985-02-08

    A microwave detector is provided for measuring the envelope shape of a microwave pulse comprised of high-frequency oscillations. A biased ferrite produces a magnetization field flux that links a B-dot loop. The magnetic field of the microwave pulse participates in the formation of the magnetization field flux. High-frequency insensitive means are provided for measuring electric voltage or current induced in the B-dot loop. The recorded output of the detector is proportional to the time derivative of the square of the envelope shape of the microwave pulse.

  11. Microwave spectrum, molecular structure, dipole moment, and quantum chemical calculations of s-trans-(E)-2-methyl-2-propenal oxime

    NASA Astrophysics Data System (ADS)

    Kuze, Nobuhiko; Ohashi, Osamu; Sakaizumi, Takeshi

    2017-07-01

    The spectroscopic constants of s-trans-(E)-2-methyl-2-propenal oxime (methacryl- aldehyde oxime) of normal, H2Cdbnd C(CH3)sbnd CHdbnd NOH, and its deuterated species, H2Cdbnd C(CH3)sbnd CHdbnd NOD, were determined by observing their microwave spectra in the frequency range of 8 to 40 GHz in the ground vibrational state. The rotational constants were A = 8321.38(82), B = 2076.09(1), and C = 1678.60(1) MHz for normal species and A = 8283.7(16), B = 1998.63(2), and C = 1626.21(2) MHz for deuterated species, respectively. The inertial defects (ΔI = Ic - Ia - Ib) of normal and deuterated species were determined to be -3.09(2) and -3.10(3) uÅ2, respectively. The dipole moments were determined as μa = 0.53(2), μb = 0.27(2), and μtotal = 0.60(5) D. The 14N nuclear quadrupole coupling constants were determined as χaa = 3.62(12), χbb = -5.1(14), and χcc = 1.48(26) MHz. The comparison of the observed spectroscopic parameters with the calculated ones led to the conclusion that the assigned spectrum was due to s-trans-(E) form. The rs coordinates of the hydrogen atom in a hydroxyl group were determined and the OH bond was found to be at the trans position with respect to the Cdbnd N double bond. The structural parameters of r(C2sbnd C3), r(C2sbnd C6), ∠ C2C3N and ∠ C6C2C3, for s-trans-syn form were adjusted to the four observed rotational constants (B and C). The observed rotational constants for s-trans-(E) form were in good agreement with those calculated using the MP2/6-31 G (d, p) level of theory.

  12. Effect of Ag on structural, optical and luminescence properties of ZnS nanoparticles synthesized by microwave-assisted chemical route

    NASA Astrophysics Data System (ADS)

    Patel, Kamakshi; Deshpande, M. P.; Chaki, S. H.

    2017-05-01

    Silver (Ag)-doped (0, 5, 10 and 15%) ZnS nanoparticles are synthesized by microwave-assisted chemical route using polyvinylpyrrolidone (PVP). We study the compositional, structural, optical and luminescence properties by energy-dispersive analysis of X-rays (EDAX), transmission electron microscopy (TEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), UV-Vis spectroscopy and photoluminescence (PL) spectroscopy, respectively. Synthesized Ag-doped ZnS nanoparticles do not possess any impurity as seen from EDAX spectra. TEM images show particles to be in spherical shape with agglomeration, and corresponding selected area electron diffraction (SAED) pattern showed that they are polycrystalline in nature. Allowed LO and TO modes corresponding to cubic phase for all the samples are observed in Raman spectra. FTIR spectroscopy is used to study the interaction between PVP and as-synthesized nanoparticles. Blue shift can be seen in pure and Ag-doped ZnS nanoparticles compared to bulk ZnS as seen from absorption spectra. Green emission is observed in PL spectra due to Ag doping without showing any quenching behavior.

  13. Growth, microstructure, and field-emission properties of synthesized diamond film on adamantane-coated silicon substrate by microwave plasma chemical vapor deposition

    SciTech Connect

    Tiwari, Rajanish N.; Chang Li

    2010-05-15

    Diamond nucleation on unscratched Si surface is great importance for its growth, and detailed understanding of this process is therefore desired for many applications. The pretreatment of the substrate surface may influence the initial growth period. In this study, diamond films have been synthesized on adamantane-coated crystalline silicon {l_brace}100{r_brace} substrate by microwave plasma chemical vapor deposition from a gaseous mixture of methane and hydrogen gases without the application of a bias voltage to the substrates. Prior to adamantane coating, the Si substrates were not pretreated such as abraded/scratched. The substrate temperature was {approx}530 deg. C during diamond deposition. The deposited films are characterized by scanning electron microscopy, Raman spectrometry, x-ray diffraction, and x-ray photoelectron spectroscopy. These measurements provide definitive evidence for high-crystalline quality diamond film, which is synthesized on a SiC rather than clean Si substrate. Characterization through atomic force microscope allows establishing fine quality criteria of the film according to the grain size of nanodiamond along with SiC. The diamond films exhibit a low-threshold (55 V/{mu}m) and high current-density (1.6 mA/cm{sup 2}) field-emission (FE) display. The possible mechanism of formation of diamond films and their FE properties have been demonstrated.

  14. Growth of graphene on Cu foils by microwave plasma chemical vapor deposition: The effect of in-situ hydrogen plasma post-treatment

    NASA Astrophysics Data System (ADS)

    Fang, Liping; Yuan, Wen; Wang, Bing; Xiong, Ying

    2016-10-01

    Microwave plasma chemical vapor deposition (MPCVD) is a promising method for the large-scale production of high-quality graphene. The aim of this work is to investigate the effect of in-situ hydrogen plasma post-treatment on the MPCVD-grown graphene films. By simply varying the duration time of in-situ hydrogen plasma, surface morphology, number of layers and defect density of as-grown graphene films can be manipulated. The role of hydrogen plasma can be proposed from our observations, promoting to further grow graphene films in the early stage and consequently acting as an etching agent to thin graphene films in the later stage. On the basis of above mechanism, monolayer graphene films with low defect density and smooth surface can be grown by adjusting the times of the growing step and the plasma post-treatment step. This additional in-situ hydrogen plasma post-treatment may be significant for growing well-defined graphene films with controllable defects and number of layers.

  15. Automated radioanalytical system incorporating microwave-assisted sample preparation, chemical separation, and online radiometric detection for the monitoring of total 99Tc in nuclear waste processing streams.

    PubMed

    Egorov, Oleg B; O'Hara, Matthew J; Grate, Jay W

    2012-04-03

    An automated fluidic instrument is described that rapidly determines the total (99)Tc content of aged nuclear waste samples, where the matrix is chemically and radiologically complex and the existing speciation of the (99)Tc is variable. The monitor links microwave-assisted sample preparation with an automated anion exchange column separation and detection using a flow-through solid scintillator detector. The sample preparation steps acidify the sample, decompose organics, and convert all Tc species to the pertechnetate anion. The column-based anion exchange procedure separates the pertechnetate from the complex sample matrix, so that radiometric detection can provide accurate measurement of (99)Tc. We developed a preprogrammed spike addition procedure to automatically determine matrix-matched calibration. The overall measurement efficiency that is determined simultaneously provides a self-diagnostic parameter for the radiochemical separation and overall instrument function. Continuous, automated operation was demonstrated over the course of 54 h, which resulted in the analysis of 215 samples plus 54 hly spike-addition samples, with consistent overall measurement efficiency for the operation of the monitor. A sample can be processed and measured automatically in just 12.5 min with a detection limit of 23.5 Bq/mL of (99)Tc in low activity waste (0.495 mL sample volume), with better than 10% RSD precision at concentrations above the quantification limit. This rapid automated analysis method was developed to support nuclear waste processing operations planned for the Hanford nuclear site.

  16. Technical and Engineering Feasibility Study of the Vitrification of Plutonium-Bearing Sludges at the Krasnoyarsk Mining and Chemical Combine by Means of Microwave Heating

    SciTech Connect

    Revenko, Y.A.; Kudinov, K.G.; Tretyakov, A.A.; Vassilyev, A.V.; Borisov, G.B.; Nazarov, A.V.; Aloy, A.S.; Shvedov, A.A.; Gusakov, B.V.; Jardine, L.J.

    2000-03-03

    This engineering feasibility study compared three possible technical options and their economic viability of processing plutonium-bearing sludges containing 0.6 MT of weapons-grade Pu accumulated at the Mining and Chemical Combine (MCC) at Krasnoyarsk. In Option 1, the baseline, the sludges are processed by extraction and purification of plutonium for storage using existing technologies, and the non-soluble radioactive residues generated in these processes undergo subsequent solidification by cementation. Options 2 and 3 involve the direct immobilization of plutonium-bearing sludges into a solid matrix (without any Pu extraction) using a microwave solidification process in a metal crucible to produce a glass, which is boron-silicate in Option 2 and phosphate glass in Option 3. In all three options, the solid radioactive waste end products will be placed in storage for eventual geologic disposal. Immobilization of residual plutonium into glass-like matrices provides both safer storage over the lifetime of the radionuclides and greater security against unauthorized access to stored materials than does the extraction and concentration of PuO{sub 2}, supporting our efforts toward non-proliferation of fissile materials. Although immobilization in boron-silicate glass appears now to be marginally preferable compared to the phosphate glass option, a number of technical issues remain to be assessed by further study to determine the preferable immobilization option.

  17. Synthesis of highly transparent ultrananocrystalline diamond films from a low-pressure, low-temperature focused microwave plasma jet.

    PubMed

    Liao, Wen-Hsiang; Wei, Da-Hua; Lin, Chii-Ruey

    2012-01-19

    This paper describes a new low-temperature process underlying the synthesis of highly transparent ultrananocrystalline diamond [UNCD] films by low-pressure and unheated microwave plasma jet-enhanced chemical vapor deposition with Ar-1%CH4-10%H2 gas chemistry. The unique low-pressure/low-temperature [LPLT] plasma jet-enhanced growth even with added H2 and unheated substrates yields UNCD films similar to those prepared by plasma-enhanced growth without addition of H2 and heating procedure. This is due to the focused plasma jet which effectively compensated for the sluggish kinetics associated with LPLT growth. The effects of pressure on UNCD film synthesis from the microwave plasma jet were systematically investigated. The results indicated that the substrate temperature, grain size, surface roughness, and sp3 carbon content in the films decreased with decreasing pressure. The reason is due to the great reduction of Hα emission to lower the etching of sp2 carbon phase, resulting from the increase of mean free path with decreasing pressure. We have demonstrated that the transition from nanocrystalline (80 nm) to ultrananocrystalline (3 to 5 nm) diamond films grown via microwave Ar-1%CH4-10%H2 plasma jets could be controlled by changing the pressure from 100 to 30 Torr. The 250-nm-thick UNCD film was synthesized on glass substrates (glass transition temperature [Tg] 557°C) using the unique LPLT (30 Torr/460°C) microwave plasma jet, which produced UNCD films with a high sp3 carbon content (95.65%) and offered high optical transmittance (approximately 86% at 700 nm).

  18. Microwave Plasma-Activated Chemical Vapor Deposition of Nitrogen-Doped Diamond. I. N2/H2 and NH3/H2 Plasmas.

    PubMed

    Truscott, Benjamin S; Kelly, Mark W; Potter, Katie J; Johnson, Mack; Ashfold, Michael N R; Mankelevich, Yuri A

    2015-12-31

    We report a combined experimental/modeling study of microwave activated dilute N2/H2 and NH3/H2 plasmas as a precursor to diagnosis of the CH4/N2/H2 plasmas used for the chemical vapor deposition (CVD) of N-doped diamond. Absolute column densities of H(n = 2) atoms and NH(X(3)Σ(-), v = 0) radicals have been determined by cavity ring down spectroscopy, as a function of height (z) above a molybdenum substrate and of the plasma process conditions, i.e., total gas pressure p, input power P, and the nitrogen/hydrogen atom ratio in the source gas. Optical emission spectroscopy has been used to investigate variations in the relative number densities of H(n = 3) atoms, NH(A(3)Π) radicals, and N2(C(3)Πu) molecules as functions of the same process conditions. These experimental data are complemented by 2-D (r, z) coupled kinetic and transport modeling for the same process conditions, which consider variations in both the overall chemistry and plasma parameters, including the electron (Te) and gas (T) temperatures, the electron density (ne), and the plasma power density (Q). Comparisons between experiment and theory allow refinement of prior understanding of N/H plasma-chemical reactivity, and its variation with process conditions and with location within the CVD reactor, and serve to highlight the essential role of metastable N2(A(3)Σ(+)u) molecules (formed by electron impact excitation) and their hitherto underappreciated reactivity with H atoms, in converting N2 process gas into reactive NHx (x = 0-3) radical species.

  19. Making Ends Meet: Microwave-Accelerated Synthesis of Cyclic and Disulfide Rich Proteins Via In Situ Thioesterification and Native Chemical Ligation.

    PubMed

    Gunasekera, Sunithi; Aboye, Teshome L; Madian, Walid A; El-Seedi, Hesham R; Göransson, Ulf

    2013-03-01

    The development of synthetic methodologies for cyclic peptides is driven by the discovery of cyclic peptide drug scaffolds such as the plant-derived cyclotides, sunflower trypsin inhibitor 1 (SFTI-1) and the development of cyclized conotoxins. Currently, the native chemical ligation reaction between an N-terminal cysteine and C-terminal thioester group remains the most robust method to obtain a head-to-tail cyclized peptide. Peptidyl thioesters are effectively generated by Boc SPPS. However, their generation is challenging using Fmoc SPPS because thioester linkers are not stable to repeated piperidine exposure during deprotection. Herein we describe a Fmoc-based protocol for synthesizing cyclic peptides adapted for microwave assisted solid phase peptide synthesis. The protocol relies on the linker Di-Fmoc-3,4-diaminobenzoic acid, and we demonstrate the use of Gly, Ser, Arg and Ile as C-terminal amino acids (using HBTU and HATU as coupling reagents). Following synthesis, an N-acylurea moiety is generated at the C-terminal of the peptide; the resin bound acylurea peptide is then deprotected and cleaved from the resin. The fully deprotected peptide undergoes thiolysis in aqueous buffer, generating the thioester in situ. Ultimately, the head-to-tail cyclized peptide is obtained via native chemical ligation. Two naturally occurring cyclic peptides, the prototypical Möbius cyclotide kalata B1 and SFTI-1 were synthesized efficiently, avoiding potential branching at the diamino linker, using the optimized protocol. In addition, we demonstrate the possibility to use the approach for the synthesis of long and synthetically challenging linear sequences, by the ligation of two truncated fragments of a 50-residue long plant defensin.

  20. Metalorganic precursor decomposition and oxidation mechanisms in plasma-enhanced ZrO2 deposition

    NASA Astrophysics Data System (ADS)

    Cho, Byeong-Ok; Wang, Jianjun; Chang, Jane P.

    2002-10-01

    We investigated the gas phase reaction mechanisms in the ZrO2-deposition plasma using zirconium tert-butoxide (ZTB) as a metalorganic precursor, Ar as a carrier of the ZTB vapor, and O2 as an oxidant using quadrupole mass spectrometry (QMS). Zirconium containing ions including Zr+, ZrO+, ZrO2H+, ZrO3H3+, and ZrO4H5+ were clearly observed in the plasma, and ions of higher zirconium oxidation states become progressively favored at higher O2-to-ZTB carrying Ar flow rate ratio (O2/Ar), increased chamber pressure, and decreased microwave power. The average oxidation state calculated from the partition of ZrOxHy+ varied from 0.5 to 2.1 in the process range covering O2/Ar of 0 to 4, pressure of 5 to 40 mTorr, and power of 150 to 700 W. Based on the QMS analyses, we proposed two main opposing reaction paths responsible for the complex gas phase reactions, i.e., serial dissociations and serial oxidations. The increase in the electron temperature and density resulted in the shift of ZrOxHy+ to lower oxidation states by enhancing the dissociation of Zr-O bond and by depleting oxygen through gas phase reactions. The repartitioning of the ZrOxHy+ species was also contributed by their different Zr-O dissociation energies. To ascertain the effect of various process variables, we monitored the time evolutions of O2+ and ZrOxHy+ intensities as we abruptly change a process variable: the chemical effect (O2/Ar) led to gradual changes in their intensities, whereas physical effects (pressure and power) caused an abrupt step change in accordance with an instant response of the plasma electrons.

  1. Atmospheric pressure microwave assisted heterogeneous catalytic reactions.

    PubMed

    Chemat-Djenni, Zoubida; Hamada, Boudjema; Chemat, Farid

    2007-07-11

    The purpose of the study was to investigate microwave selective heating phenomena and their impact on heterogeneous chemical reactions. We also present a tool which will help microwave chemists to answer to such questions as "My reaction yields 90% after 7 days at reflux; is it possible to obtain the same yield after a few minutes under microwaves?" and to have an approximation of their reactions when conducted under microwaves with different heterogeneous procedures. This model predicting reaction kinetics and yields under microwave heating is based on the Arrhenius equation, in agreement with experimental data and procedures.

  2. Fabrication of metallic single electron transistors featuring plasma enhanced atomic layer deposition of tunnel barriers

    NASA Astrophysics Data System (ADS)

    Karbasian, Golnaz

    The continuing increase of the device density in integrated circuits (ICs) gives rise to the high level of power that is dissipated per unit area and consequently a high temperature in the circuits. Since temperature affects the performance and reliability of the circuits, minimization of the energy consumption in logic devices is now the center of attention. According to the International Technology Roadmaps for Semiconductors (ITRS), single electron transistors (SETs) hold the promise of achieving the lowest power of any known logic device, as low as 1x10-18 J per switching event. Moreover, SETs are the most sensitive electrometers to date, and are capable of detecting a fraction of an electron charge. Despite their low power consumption and high sensitivity for charge detection, room temperature operation of these devices is quite challenging mainly due to lithographical constraints in fabricating structures with the required dimensions of less than 10 nm. Silicon based SETs have been reported to operate at room temperature. However, they all suffer from significant variation in batch-to-batch performance, low fabrication yield, and temperature-dependent tunnel barrier height. In this project, we explored the fabrication of SETs featuring metal-insulator-metal (MIM) tunnel junctions. While Si-based SETs suffer from undesirable effect of dopants that result in irregularities in the device behavior, in metal-based SETs the device components (tunnel barrier, island, and the leads) are well-defined. Therefore, metal SETs are potentially more predictable in behavior, making them easier to incorporate into circuits, and easier to check against theoretical models. Here, the proposed fabrication method takes advantage of unique properties of chemical mechanical polishing (CMP) and plasma enhanced atomic layer deposition (PEALD). Chemical mechanical polishing provides a path for tuning the dimensions of the tunnel junctions, surpassing the limits imposed by electron beam

  3. High speed deposition of SiO2 film by slot-type microwave CVD system

    NASA Astrophysics Data System (ADS)

    Toyoda, Hirotaka; Yamamoto, Masaki; Suzuki, Haruka

    2016-09-01

    High density microwave plasma is attractive because of its ability for high-throughput processing. So far, we have successfully produced large-area surface wave excited plasma (SWP) and have applied it to plasma-enhanced chemical vapor deposition (PE-CVD) of silicon films. However, the SWP requires a dielectric plate for the surface wave propagation, and high density plasma sometimes erodes the dielectric plate to produce oxygen contamination. To avoid such problem, we propose the PE-CVD using the microwave plasma produced inside slots of a waveguide without using the dielectric plate. A 2.45 GHz pulsed microwave (repetition: 20 kHz, duty ratio: 20%, average power: 40 W) is introduced to a rectangular waveguide through an isolator, a tuner, and a vacuum window. A slot of 4 mm in length and 0.2 mm in width is placed at the end of the waveguide, and is connected to a vacuum chamber. Both the waveguide and the chamber are evacuated by a turbomolecular pump. Oxygen and tetraethyl orthosilicate (TEOS) gases are introduced from the waveguide and from the outside of the waveguide, respectively, to deposit SiO2 film on Si substrates at a pressure of 15 Torr and a slot-substrate distance of 1.1 cm. Deposition rate as high as 80 nm/s is observed at a TEOS flow rate of 0.8 sccm. The result suggests that the present PE-CVD system is promising as a new high-speed film deposition technique. Part of this work is supported by JSPS KAKENHI Grant Number 25286079.

  4. Microwave discharge electrodeless lamps (MDELs). Part IX. A novel MDEL photoreactor for the photolytic and chemical oxidation treatment of contaminated wastewaters.

    PubMed

    Horikoshi, Satoshi; Tsuchida, Akihiro; Shinomiya, Tomohiro; Serpone, Nick

    2015-12-01

    This article reports on the fabrication and enhanced performance of a novel microwave discharge electrodeless lamp (MDEL) consisting of a three layered cylindrical structure that was effective in the remediation of wastewater containing the 2,4-D herbicide and the near total sterilization of bacteria-contaminated pond water (E. coli and other microorganisms) through photolysis with the emitted vacuum-UV (185 nm) and UVC (254 nm) light from the MDEL and through chemical oxidation with reactive oxygen species (ROS) produced by the photolysis of dioxygen and air oxygen through one of the photoreactors. The flow rates of the 1.0 L contaminated waters were 0.6 and 1.2 L min(-1). The integrated UV/ROSO2 and UV/ROSair methods used to carry out the degradation of 2,4-D and sterilization processes were more effective than either the UV method alone or the ROSO2 and ROSair methods for short time periods (5 or 8 min). At a lower flow rate, 79% of 2,4-D was degraded by the UV/ROSO2 method and 55% by UV/ROSair after 8 min. At a faster flow rate of 1.2 L min(-1), degradation of 2,4-D in 1.0 L volume of water was 84% and 77% complete by the UV/ROSO2 and the UV/ROSair method, respectively, after 8 min of irradiation. The number of kills of E. coli bacteria was nearly quantitative (98 and 99%) by the UV/ROSO2 and UV/ROSair methods after treating the contaminated water for 5 min. The decrease of total viable microorganisms in pond water was 90% and 80% after 5 min of microwave irradiation at a flow rate of 1.2 L min(-1) by the integrated methods UV/ROSO2 and UV/ROSair, respectively. The rate of flow of oxygen gas through the photoreactor impacted the extent of degradation and the related dynamics of the 2,4-D herbicide.

  5. A microwave and quantum chemical study of (trifluoromethyl)thiolacetic acid, CF3COSH, a compound with an unusual double-minimum potential.

    PubMed

    Møllendal, Harald

    2007-03-15

    The microwave spectra of CF3COSH and one deuterated species, CF3COSD, have been investigated by Stark spectroscopy in the 40-80 GHz spectral range at -78 degrees C and by quantum chemical calculations using the HF, MP2, and B3LYP procedures with the aug-cc-pVTZ basis set. The microwave spectrum of one conformer was assigned. The conformations of the COSH and CF3 groups determine the overall conformation of this rotamer. It was not possible experimentally to find precise values for the associated dihedral angles, but it appears that the COSH group is distorted somewhat from an exact synperiplanar arrangement, while the CF3 group is rotated several degrees from a position where one of the C-F bonds eclipses the C-S bond. This rotamer tunnels through a transition state that has an exact Cs symmetry, where one C-F bond eclipses the C-S bond and the COSH group is synperiplanar. Relative intensity measurements yielded 28(15) cm-1 for the tunneling frequency. Two additional vibrationally excited states were assigned and their frequencies determined to be 94(30) and 184(40) cm-1, respectively. The theoretical calculations predict conflicting conformational properties for the identified rotamer. The B3LYP calculations find an exact synperiplanar arrangement for the COSH group, whereas the MP2 and HF calculations predict that this group is distorted slightly form this conformation. One of the C-F bonds is found to eclipse the C-S bond in the B3LYP calculations, while the MP2 calculations predict a slight deviation and the HF calculations a large deviation from the eclipsed position, as the corresponding F-C-C-S dihedral angle is calculated to be 0.9 degrees (MP2) and 27.6 degrees (HF). All three methods of calculations predict that a second rotamer coexists with the identified form but is several kJ/mol less stable. The spectrum of this form, which has overall Cs symmetry and is predicted to have an antiperiplanar conformation for the COSH group with one of the C-F bonds

  6. Uniformity and passivation research of Al2O3 film on silicon substrate prepared by plasma-enhanced atom layer deposition

    NASA Astrophysics Data System (ADS)

    Jia, Endong; Zhou, Chunlan; Wang, Wenjing

    2015-03-01

    Plasma-enhanced atom layer deposition (PEALD) can deposit denser films than those prepared by thermal ALD. But the improvement on thickness uniformity and the decrease of defect density of the films deposited by PEALD need further research. A PEALD process from trimethyl-aluminum (TMA) and oxygen plasma was investigated to study the influence of the conditions with different plasma powers and deposition temperatures on uniformity and growth rate. The thickness and refractive index of films were measured by ellipsometry, and the passivation effect of alumina on n-type silicon before and after annealing was measured by microwave photoconductivity decay method. Also, the effects of deposition temperature and annealing temperature on effective minority carrier lifetime were investigated. Capacitance-voltage and conductance-voltage measurements were used to investigate the interface defect density of state ( D it) of Al2O3/Si. Finally, Al diffusion P+ emitter on n-type silicon was passivated by PEALD Al2O3 films. The conclusion is that the condition of lower substrate temperature accelerates the growth of films and that the condition of lower plasma power controls the films' uniformity. The annealing temperature is higher for samples prepared at lower substrate temperature in order to get the better surface passivation effects. Heavier doping concentration of Al increased passivation quality after annealing by the effective minority carrier lifetime up to 100 μs.

  7. Three isomers detected for the whisky lactone: 5-butyl-4-methyl tetrahydrofuran-2-one by Fourier transform microwave spectroscopy and quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Kawashima, Yoshiyuki; Katsuragi, Ryusuke; Hirota, Eizi

    2017-05-01

    The ground-state rotational spectra of the whisky lactone (WL) : 5-butyl-4-methyl tetrahydrofuran-2-one were observed and analyzed by molecular beam Fourier transform microwave spectroscopy combined with quantum chemical calculations. We have detected three stereo-isomers: the trans-TTT form with a methyl CH3 group attached to C(4) in an equatorial position (eq) and a butyl C4H9 group to C(5) in an eq position, for which 110 b-type and 113 a-type transitions were assigned, the cis-TTT form with a CH3 to C(4) in an axial position (ax) and a C4H9 to C(5) in eq, for which 96 a-type, 101 b-type, and 45 c-type transitions were observed, and the cis-GTT form with a CH3 to C(4) in ax and a C4H9 to C(5) in eq, for which 158 a-type, 52 b-type, and 17 c-type transitions were observed, where TTT and GTT denote the conformations about the C(6)sbnd C(5), C(7)sbnd C(6), and C(8)sbnd C(7) bonds, with T and G designating trans and gauche, respectively. The rotational constants thus derived agree with the predictions made by quantum chemical calculations, MP2/6-311++G(d, p) within 1.2%. The trans-TTT form was calculated to be the most stable. The splittings due to internal rotation of the terminal methyl in the butyl group were observed for all the three stereo-isomers and were analyzed by the XIAM program to determine the threefold potential barrier V3 to be 966.4 (25), 978.8 (11), and 1098.7 (48) in cm-1 for the trans-TTT (eq, eq), the cis-TTT (ax, eq), and the cis-GTT (ax, eq) forms, respectively, to be compared with quantum chemically calculated values: 1055, 1055, and 1053 in cm-1.

  8. Microwave Supported Treatment of Sewage Sludge

    NASA Astrophysics Data System (ADS)

    Janíček, František; Perný, Milan; Šály, Vladimír; Giemza, Markus; Hofmann, Peter

    2016-07-01

    This work is focused on microwave treatment of sewage sludge. The aim of our experiments was to investigate the impact of microwave radiation upon different sewage sludge parameters such as concentration of nitrates and nitrites, phosphates, COD (Chemical Oxygen Demand), SVI (Sludge Volume Index) and the microscopic structure of sludge. The experiments with microwave irradiation of sewage sludge indicate that moderate microwave power causes visible effects on the chemical, physical and biological properties of the sludge. The calculation of profitability and energy efficiency is also presented.

  9. Growing aluminum nitride films by Plasma-Enhanced Atomic Layer Deposition at low temperatures

    NASA Astrophysics Data System (ADS)

    Tarala, V. A.; Altakhov, A. S.; Martens, V. Ya; Lisitsyn, S. V.

    2015-11-01

    Aluminum nitride films have been grown by Plasma-Enhanced Atomic Layer Deposition method. It was found that at temperatures of 250 °C and 280 °C increase of the plasma exposure step duration over 6 s, as well as increase of reactor purge step duration over 1 s does not affect the growth rate, however, it affects the microstructure of the films. It was found that crystalline aluminum nitride films deposit with plasma exposure duration over 10 s and the reactor purging over 10 s. When the temperature drops the increase of reactor purge step duration and plasma exposure step duration over 20 s is required for crystalline AlN film growth.

  10. Silicon dioxide mask by plasma enhanced atomic layer deposition in focused ion beam lithography

    NASA Astrophysics Data System (ADS)

    Liu, Zhengjun; Shah, Ali; Alasaarela, Tapani; Chekurov, Nikolai; Savin, Hele; Tittonen, Ilkka

    2017-02-01

    In this work, focused ion beam (FIB) lithography was developed for plasma enhanced atomic layer deposited (PEALD) silicon dioxide SiO2 hard mask. The PEALD process greatly decreases the deposition temperature of the SiO2 hard mask. FIB Ga+ ion implantation on the deposited SiO2 layer increases the wet etch resistivity of the irradiated region. A programmed exposure in FIB followed by development in a wet etchant enables the precisely defined nanoscale patterning. The combination of FIB exposure parameters and the development time provides greater freedom for optimization. The developed process provides high pattern dimension accuracy over the tested range of 90-210 nm. Utilizing the SiO2 mask developed in this work, silicon nanopillars with 40 nm diameter were successfully fabricated with cryogenic deep reactive ion etching and the aspect ratio reached 16:1. The fabricated mask is suitable for sub-100 nm high aspect ratio silicon structure fabrication.

  11. Low temperature plasma-enhanced ALD enables cost-effective spacer defined double patterning (SDDP)

    NASA Astrophysics Data System (ADS)

    Beynet, Julien; Wong, Patrick; Miller, Andy; Locorotondo, Sabrina; Vangoidsenhoven, Diziana; Yoon, Tae-Ho; Demand, Marc; Park, Hyung-Sang; Vandeweyer, Tom; Sprey, Hessel; Yoo, Yong-Min; Maenhoudt, Mireille

    2009-12-01

    The inherent advantages of the Plasma-Enhanced Atomic Layer Deposition (PEALD) technology--excellent conformality and within wafer uniformity, no loading effect--overcome the limitations in this domain of the standard PECVD technique for spacer deposition. The low temperature process capability of PEALD silicon oxide enables direct spacer deposition on photoresist, thus suppressing the need of a patterned template hardmask to design the spacers. By decreasing the number of deposition and patterning steps, this so-called Direct Spacer Defined Double Patterning (DSDDP) integration reduces cost and complexity of the conventional SDDP approach. A successful integration is reported for 32 nm half-pitch polysilicon lines. The performances are promising, especially from the lines, which result from the PEALD spacers: Critical Dimension Uniformity (CDU) of 1.3 nm and Line Width Roughness (LWR) of 2.0 nm.

  12. Silicon dioxide mask by plasma enhanced atomic layer deposition in focused ion beam lithography.

    PubMed

    Liu, Zhengjun; Shah, Ali; Alasaarela, Tapani; Chekurov, Nikolai; Savin, Hele; Tittonen, Ilkka

    2017-02-24

    In this work, focused ion beam (FIB) lithography was developed for plasma enhanced atomic layer deposited (PEALD) silicon dioxide SiO2 hard mask. The PEALD process greatly decreases the deposition temperature of the SiO2 hard mask. FIB Ga(+) ion implantation on the deposited SiO2 layer increases the wet etch resistivity of the irradiated region. A programmed exposure in FIB followed by development in a wet etchant enables the precisely defined nanoscale patterning. The combination of FIB exposure parameters and the development time provides greater freedom for optimization. The developed process provides high pattern dimension accuracy over the tested range of 90-210 nm. Utilizing the SiO2 mask developed in this work, silicon nanopillars with 40 nm diameter were successfully fabricated with cryogenic deep reactive ion etching and the aspect ratio reached 16:1. The fabricated mask is suitable for sub-100 nm high aspect ratio silicon structure fabrication.

  13. Plasma-enhanced atomic layer deposition of titanium oxynitrides films: A comparative spectroscopic and electrical study

    SciTech Connect

    Sowińska, Małgorzata Henkel, Karsten; Schmeißer, Dieter; Kärkkänen, Irina; Schneidewind, Jessica; Naumann, Franziska; Gruska, Bernd; Gargouri, Hassan

    2016-01-15

    The process parameters' impact of the plasma-enhanced atomic layer deposition (PE-ALD) method on the oxygen to nitrogen (O/N) ratio in titanium oxynitride (TiO{sub x}N{sub y}) films was studied. Titanium(IV)isopropoxide in combination with NH{sub 3} plasma and tetrakis(dimethylamino)titanium by applying N{sub 2} plasma processes were investigated. Samples were characterized by the in situ spectroscopic ellipsometry, x-ray photoelectron spectroscopy, and electrical characterization (current–voltage: I-V and capacitance–voltage: C-V) methods. The O/N ratio in the TiO{sub x}N{sub y} films is found to be very sensitive for their electric properties such as conductivity, dielectric breakdown, and permittivity. Our results indicate that these PE-ALD film properties can be tuned, via the O/N ratio, by the selection of the process parameters and precursor/coreactant combination.

  14. Comparison of ammonia plasma and AlN passivation by plasma-enhanced atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Mattila, P.; Bosund, M.; Huhtio, T.; Lipsanen, H.; Sopanen, M.

    2012-03-01

    Surface passivation of GaAs by ammonia plasma and AlN fabricated by plasma-enhanced atomic layer deposition are compared. It is shown that the deposition temperature can be reduced to 150 °C and effective passivation is still achieved. Samples passivated by AlN fabricated at 150 °C show four times higher photoluminescence intensity and longer time-resolved photoluminescence lifetime than ammonia plasma passivated samples. The passivation effect is shown to last for months. The dependence of charge carrier lifetime and integrated photoluminescence intensity on AlN layer thickness is studied using an exponential model to describe the tunneling probability from the near-surface quantum well to the GaAs surface.

  15. Understanding the inductively coupled argon plasma-enhanced quantum well intermixing

    NASA Astrophysics Data System (ADS)

    Mei, Ting; Djie, H. S.; Arokiaraj, J.; Sookdhis, C.

    2004-08-01

    Recently, we have been developing an inductively coupled argon plasma-enhanced QWI technology for tuning the bandgap of InGaAs/InP QW laser structure. The application of ICP energy plays a strong role to the interdiffusion of point defects instead of the ion bombardment mechanism, resulting in high degree of intermixing. The effects of the plasma-induced defects, the factors that affect the QWI process and the general correlations of the plasma exposure effect to bandgap shift have been well understood with the analytical model. The theoretical results appear to be in good agreement with the experimental data of the intermixed samples. The model serves as a good simulation tool to explain the intermixing mechanism and further to optimize the intermixing process for the fabrication of the photonic integrated circuits.

  16. Growing oriented AlN films on sapphire substrates by plasma-enhanced atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Tarala, V. A.; Altakhov, A. S.; Ambartsumov, M. G.; Martens, V. Ya.

    2017-01-01

    The possibility of growing oriented AlN films on Al2O3 substrates at temperatures below 300°C by plasma-enhanced atomic layer deposition was examined. The samples were subjected to X-ray phase analysis and ellipsometry. It was demonstrated that the refraction index of films deposited with plasma exposures longer than 20 s was 2.03 ± 0.03. The (0002) and (0004) reflections at 2Θ angles of 35.7° and 75.9° were present in the X-ray diffraction patterns of these samples. These reflections are typical of the hexagonal AlN polytype. The full width at half maximum of the rocking curve of reflection (0002) in the best sample was 162 ± 11 arcsec.

  17. Titanium dioxide thin films deposited by plasma enhanced atomic layer deposition for OLED passivation.

    PubMed

    Kim, Woong-Sun; Ko, Myoung-Gyun; Kim, Tae-Sub; Park, Sang-Kyun; Moon, Yeon-Keon; Lee, Su-Hwan; Park, Jae-Gun; Park, Jong-Wan

    2008-09-01

    Plasma enhanced atomic layer deposition (PEALD) of titanium dioxide thin films was conducted using Tetrakis dimethylamino titanium (TDMATi) and an oxygen plasma on a polyethersulfon (PES) substrate at a deposition temperature of 90 degrees C. The effects of the induced plasma power on passivation properties were investigated according to film thickness. The growth rate of the titanium dioxide film was 0.8 A/cycle, and the water vapor transmission rate (WTVR) for a 80 nm titanium dioxide film was 0.023 g/m2 day. The passivation performance of the titanium dioxide film was investigated using an organic light-emitting diode (OLED). The coated OLED lifetime was 90 h, 15 times longer than that of an uncoated sample.

  18. Rotational Spectroscopy and Quantum Chemical Calculations of a Fruit Ester: the Microwave Spectrum of n-BUTYL Acetate

    NASA Astrophysics Data System (ADS)

    Attig, T.; Sutikdja, L. W.; Kannengiesser, R.; Stahl, W.; Kleiner, I.

    2013-06-01

    In the course of our studies on a number of aliphatic ester molecules and natural substances, the rotational spectrum of n-butyl acetate (CH_{3}-COO-C_4H_9) has been recorded for the first time in the 10-13.5 GHz frequency range, using the MB-FTMW spectrometer in Aachen, with an instrumental uncertainty of a few kHz for unblended lines. Three conformers were observed. The main conformer with C_{1} symmetry has a strong spectrum. The other two conformers have C_{s} and C_{1} symmetries. Their intensities are considerably weaker. The quantum chemical calculations of specific conformers were carried out at the MP2/6-311++G(d,p) level, and for the main conformer different levels of theory were calculated. To analyze the internal rotation of the acetyl methyl groups the codes XIAM (based on the Combined Axis Method) and BELGI (based on the Rho-Axis-Method) were used to model the large amplitude motion. The molecular structures of the three conformers were determined and the values of the experimental rotational constants were compared with those obtained by ab initio methods. For all conformers torsional barriers of approximately 100 cm^{-1} were found. This study is part of a larger project which aims at determining the lowest energy conformers and their structures of organic esters and ketones which are of interest for flavour or perfume synthetic applications. Project partly supported by the PHC PROCOPE 25059YB

  19. Mechanism of Microwave-Assisted Pyrolysis of Glucose to Furfural Revealed by Isotopic Tracer and Quantum Chemical Calculations.

    PubMed

    Bao, Liwei; Shi, Lei; Luo, Hu; Kong, Lingzhao; Li, Shenggang; Wei, Wei; Sun, Yuhan

    2017-08-10

    Glucose labeled with (13) C or (18) O was used to investigate the mechanism of its conversion into furfural by microwaveassisted pyrolysis. The isotopic content and location in furfural were determined from GC-MS and (13) C NMR spectroscopic measurements and data analysis. The results suggest that the carbon skeleton in furfural is mainly derived from C1 to C5 of glucose, whereas the C of the aldehyde group and the O of the furan ring in furfural primarily originate from C1 and O5 of glucose, respectively. For the first time, the source of O in the furan ring of furfural was elucidated directly by experiment, providing results that are consistent with predictions from recent quantum chemical calculations. Moreover, further theoretical calculations indicate substantially lower energy barriers than previous predictions by considering the potential catalytic effect of formic acid, which is one of the pyrolysis products. The catalytic role of formic acid is further confirmed by experimental evidence. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Properties of N-rich Silicon Nitride Film Deposited by Plasma-Enhanced Atomic Layer Deposition

    NASA Astrophysics Data System (ADS)

    Jhang, Pei-Ci; Lu, Chi-Pin; Shieh, Jung-Yu; Yang, Ling-Wu; Yang, Tahone; Chen, Kuang-Chao; Lu, Chih-Yuan

    2017-07-01

    An N-rich silicon nitride film, with a lower refractive index (RI) than the stoichiometric silicon nitride (RI = 2.01), was deposited by alternating the exposure of dichlorosilane (DCS, SiH2Cl2) and that of ammonia (NH3) in a plasma-enhanced atomic layer deposition (PEALD) process. In this process, the plasma ammonia was easily decomposed to reactive radicals by RF power activating so that the N-rich silicon nitride was easily formed by excited ammonia radicals. The growth kinetics of N-rich silicon nitride were examined at various deposition temperatures ranging from 400 °C to 630 °C; the activation energy (Ea) decreased as the deposition temperature decreased below 550 °C. N-rich silicon nitride film with a wide range of values of refractive index (RI) (RI = 1.86-2.00) was obtained by regulating the deposition temperature. At the optimal deposition temperature, the effects of RF power, NH3 flow rate and NH3 flow time were on the characteristics of the N-rich silicon nitride film were evaluated. The results thus reveal that the properties of the N-rich silicon nitride film that was formed by under plasma-enhanced atomic layer deposition (PEALD) are dominated by deposition temperature. In charge trap flash (CTF) study, an N-rich silicon nitride film was applied to MAONOS device as a charge-trapping layer. The films exhibit excellent electron trapping ability and favor a fresh cell data retention performance as the deposition temperature decreased.

  1. The role of in situ reforming in plasma enhanced ultra lean premixed methane/air flames

    SciTech Connect

    Kim, Wookyung; Godfrey Mungal, M.; Cappelli, Mark A.

    2010-02-15

    This paper describes a mechanism for the stabilization of ultra lean premixed methane/air flames by pulsed nonequilibrium plasma enhancement. It is shown that the pulsed discharge plasma produces a cool ({proportional_to}500-600 K) stream of relatively stable intermediate species including hydrogen (H{sub 2}) and carbon monoxide (CO), which play a central role in enhancing flame stability. This stream is readily visualized by ultraviolet emission from electronically excited hydroxyl (OH) radicals. The rotational and vibrational temperature of this ''preflame'' are determined from its emission spectrum. Qualitative imaging of the overall flame structure is obtained by planar laser-induced fluorescence measurements of OH. Preflame nitric oxide (NO) concentrations are determined by gas sampling chromatography. A simple numerical model of this plasma enhanced premixed flame is proposed that includes the generation of the preflame through plasma activation, and predicts the formation of a dual flame structure that arises when the preflame serves to pilot the combustion of the surrounding non-activated premixed flow. The calculation represents the plasma through its ability to produce an initial radical yield, which serves as a boundary condition for conventional flame simulations. The simulations also capture the presence of the preflame and the dual flame structure, and predict preflame levels of NO comparable to those measured. A subsequent pseudo-sensitivity analysis of the preflame shows that flame stability is most sensitive to the concentrations of H{sub 2} and CO in the preflame. As a consequence of the role of H{sub 2} and CO in enhancing the flame stability, the blowout limit extensions of methane/air and hydrogen/air mixtures in the absence/presence of a discharge are investigated experimentally. For methane/air mixtures, the blowout limit of the current burner is extended by {proportional_to}10% in the presence of a discharge while comparable studies carried

  2. Microwave detector

    SciTech Connect

    Meldner, H.W.; Cusson, R.Y.; Johnson, R.M.

    1986-12-02

    A detector is described for measuring the envelope shape of a microwave pulse comprised of high-frequency oscillations, the detector comprising: a B-dot loop linking the magnetic field of the microwave pulse; a biased ferrite, that produces a magnetization field flux that links the B-dot loop. The ferrite is positioned within the B-dot loop so that the magnetic field of the microwave pulse interacts with the ferrite and thereby participates in the formation of the magnetization field flux; and high-frequency insensitive means for measuring electric voltage or current induced in the B-dot loop.

  3. Gas-Phase Molecular Structure of Nopinone and its Water Complexes Studied by Microwave Fourier Transform Spectroscopy and Quantum Chemical Calculations

    NASA Astrophysics Data System (ADS)

    Neeman, Elias M.; Aviles Moreno, Juan-Ramon; Huet, T. R.

    2016-06-01

    Several monoterpenes and terpenoids are biogenic volatile organic compounds which are emitted in the atmosphere, where they react with OH, O_3 and NO_x etc. to give rise to several oxidation and degradation products. Their decomposition products are a major source of secondray organic aerosol (SOA). Spectroscopic information on these atmospheric species is still very scarce. The rotational spectrum of nopinone (C_9H14O) one of the major oxidation products of β-pinene, and of its water complexes were recorded in a supersonic jet expansion with a Fourier transform microwave spectrometer over the range 2-20 GHz. The structure of the unique stable conformer of the nopinone was optimized using density functional theory and ab initio calculations. Signals from the parent species and from the 13C and 18O isotopomers were observed in natural abundance. A magnetic hyperfine structure associated with the pairs of hydrogen nuclei in the methylene groups was observed and modeled. The structures of several conformers of the nopinone-water complexes with up to three molecules of water were optimized using density functional theory and ab initio calculations. The energetically most stable of calculated conformers were observed and anlyzed. The rotational and centrifugal distortion parameters were fitted to a Watson's Hamiltonian in the A-reduction. The present work provides the first spectroscopic characterization of nopinone and its water complexes in the gas phase. A. Calogirou, B.R. Larsen, and D. Kotzias, Atmospheric Environment, 33, 1423-1439, (1999) P. Paasonen et al., Nat. Geosci., 6, 438-442 (2013) D. Zhang and R. Zhang The Journal of Chemical Physics, 122, 114308, (2005) R. Winterhalter et al. Journal of Atmospheric Chemistry, 35, 165-197, (2000)

  4. New instrumentation for the comprehension of chemical reactions under microwave and classical heating with the aid of a wide frequency band dielectric spectroscopy

    NASA Astrophysics Data System (ADS)

    Chevalier, S.; Meyer, O.; Weil, R.; Fourrierlamer, A.; Petit, A.; Loupy, A.; Maurel, F.

    2001-09-01

    An instrumentation system for measuring wide frequency band complex permittivity of a sample submitted to a microwave irradiation has been optimized in order to allow macroscopic temperature measurements. The reaction of saponification of aromatic esters is studied using this instrumentation. We take interest in the behavior of the ionic conductivity phenomenon occurring in the reactive medium during microwave heating, and we compare it with the results obtained under classical heating. We show that the activation energy associated with ionic conductivity is lower when the reaction is performed under microwaves than when it is performed under classical heating. We thus deduce that microwaves act on the reaction advancement as a catalyst, and thus makes the reaction easier.

  5. Microwave generator

    DOEpatents

    Kwan, T.J.T.; Snell, C.M.

    1987-03-31

    A microwave generator is provided for generating microwaves substantially from virtual cathode oscillation. Electrons are emitted from a cathode and accelerated to an anode which is spaced apart from the cathode. The anode has an annular slit there through effective to form the virtual cathode. The anode is at least one range thickness relative to electrons reflecting from the virtual cathode. A magnet is provided to produce an optimum magnetic field having the field strength effective to form an annular beam from the emitted electrons in substantial alignment with the annular anode slit. The magnetic field, however, does permit the reflected electrons to axially diverge from the annular beam. The reflected electrons are absorbed by the anode in returning to the real cathode, such that substantially no reflexing electrons occur. The resulting microwaves are produced with a single dominant mode and are substantially monochromatic relative to conventional virtual cathode microwave generators. 6 figs.

  6. SOLVENT-FREE CHEMICAL TRANSFORMATIONS USING MICROWAVE IRRADIATION. 32ND ACS CENTRAL REGIONAL MEETING, MAY 16-19, 2000, ABSTRACTS & PROGRAM, NORTHERN KENTUCKY CONVENTION CENTER, COVINGTON, KY. AMERICAN CHEMICAL SOCIETY, 1999, P. 121.

    EPA Science Inventory

    Microwave-expedited solvent-free synthetic processes will be described that involve the exposure of neat reactants to microwave (MW) irradiation in the presence of supported reagents or catalysts on minineral oxides. Recent developments will be presented on the synthetic utility...

  7. Microwave furnace having microwave compatible dilatometer

    DOEpatents

    Kimrey, Jr., Harold D.; Janney, Mark A.; Ferber, Mattison K.

    1992-01-01

    An apparatus for measuring and monitoring a change in the dimension of a sample being heated by microwave energy is described. The apparatus comprises a microwave heating device for heating a sample by microwave energy, a microwave compatible dilatometer for measuring and monitoring a change in the dimension of the sample being heated by microwave energy without leaking microwaves out of the microwave heating device, and a temperature determination device for measuring and monitoring the temperature of the sample being heated by microwave energy.

  8. Microwave furnace having microwave compatible dilatometer

    DOEpatents

    Kimrey, H.D. Jr.; Janney, M.A.; Ferber, M.K.

    1992-03-24

    An apparatus for measuring and monitoring a change in the dimension of a sample being heated by microwave energy is described. The apparatus comprises a microwave heating device for heating a sample by microwave energy, a microwave compatible dilatometer for measuring and monitoring a change in the dimension of the sample being heated by microwave energy without leaking microwaves out of the microwave heating device, and a temperature determination device for measuring and monitoring the temperature of the sample being heated by microwave energy. 2 figs.

  9. Preparation and characterization of activated carbon from cotton stalk by microwave assisted chemical activation--application in methylene blue adsorption from aqueous solution.

    PubMed

    Deng, Hui; Yang, Le; Tao, Guanghui; Dai, Jiulei

    2009-07-30

    The activated carbon prepared from cotton stalk with ZnCl(2) as activation was investigated under microwave radiation. Effects on the yield and adsorption capacities of activated carbon were evaluated then, such as, microwave power, microwave radiation time and the impregnation ratio of ZnCl(2). It indicated that the optimum conditions were as follows: microwave power of 560 W, microwave radiation time of 9 min and the impregnation ratio of ZnCl(2) was 1.6g/g. Iodine number, amount of methylene blue adsorption and the yield of activated carbon prepared under optimum conditions were 972.92 mg/g, 193.50mg/g and 37.92%, respectively. Laboratory prepared activated carbons were characterized by pH(ZPC), SEM, FT-IR, S(BET) and pore structural parameters. Then they were used as adsorbent for the removal of methylene blue from aqueous solutions under varying conditions of initial concentration, carbon dosage and pH. It indicated that Langmuir isotherm was fitter than Freundlich isotherm and Temkin isotherm.

  10. Inhibition of Crystal Growth during Plasma Enhanced Atomic Layer Deposition by Applying BIAS

    PubMed Central

    Ratzsch, Stephan; Kley, Ernst-Bernhard; Tünnermann, Andreas; Szeghalmi, Adriana

    2015-01-01

    In this study, the influence of direct current (DC) biasing on the growth of titanium dioxide (TiO2) layers and their nucleation behavior has been investigated. Titania films were prepared by plasma enhanced atomic layer deposition (PEALD) using Ti(OiPr)4 as metal organic precursor. Oxygen plasma, provided by remote inductively coupled plasma, was used as an oxygen source. The TiO2 films were deposited with and without DC biasing. A strong dependence of the applied voltage on the formation of crystallites in the TiO2 layer is shown. These crystallites form spherical hillocks on the surface which causes high surface roughness. By applying a higher voltage than the plasma potential no hillock appears on the surface. Based on these results, it seems likely, that ions are responsible for the nucleation and hillock growth. Hence, the hillock formation can be controlled by controlling the ion energy and ion flux. The growth per cycle remains unchanged, whereas the refractive index slightly decreases in the absence of energetic oxygen ions. PMID:28793679

  11. Superconducting niobium titanium nitride thin films deposited by plasma-enhanced atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Yemane, Y. T.; Sowa, M. J.; Zhang, J.; Ju, L.; Deguns, E. W.; Strandwitz, N. C.; Prinz, F. B.; Provine, J.

    2017-09-01

    NbTiN has a variety of superconducting applications, ranging from RF cavities to single-photon detectors. Here, we systematically investigated the plasma-enhanced atomic layer deposition (PEALD) of Nb x Ti{}1-x{{N}} with the organometallic precursors (t-butylimido) tris(diethyamido) niobium(V) and tetrakis (dimethylamido) titanium in conjunction with a remote H2/N2 plasma. Deposited film properties have been studied as a function of the ratio of Nb to Ti precursor pulses within each ALD supercycle. PEALD NbTiN films were characterized with spectroscopic ellipsometry (thickness, optical properties), four point probe (resistivity), x-ray photoelectron spectroscopy (composition), x-ray reflectivity (density and thickness), x-ray diffraction (crystallinity), and superconductivity measurements. The PEALD process has shown distinct advantages over deposition of superconducting films via thermal ALD or sputtering, for example a lower processing temperature and more efficient control of film composition. This control of film composition enabled the tuning of electrical and superconducting properties, such as varying the superconducting critical temperature T C between 6.9 and 13.2 K.

  12. ZnO nanorod growth by plasma-enhanced vapor phase transport with different growth durations

    SciTech Connect

    Kim, Chang-Yong; Oh, Hee-bong; Ryu, Hyukhyun; Yun, Jondo; Lee, Won-Jae

    2014-09-01

    In this study, the structural properties of ZnO nanostructures grown by plasma-enhanced vapor phase transport (PEVPT) were investigated. Plasma-treated oxygen gas was used as the oxygen source for the ZnO growth. The structural properties of ZnO nanostructures grown for different durations were measured by scanning electron microscopy, x-ray diffraction, and transmission electron microscopy. The authors comprehensively analyzed the growth of the ZnO nanostructures with different growth durations both with and without the use of plasma-treated oxygen gas. It was found that PEVPT has a significant influence on the growth of the ZnO nanorods. PEVPT with plasma-treated oxygen gas facilitated the generation of nucleation sites, and the resulting ZnO nanorod structures were more vertical than those prepared by conventional VPT without plasma-treated oxygen gas. As a result, the ZnO nanostructures grown using PEVPT showed improved structural properties compared to those prepared by the conventional VPT method.

  13. Use of plasma enhanced ALD to construct efficient interference filters for astronomy in the FUV

    NASA Astrophysics Data System (ADS)

    Scowen, Paul A.; Nemanich, Robert; Eller, Brianna; Yu, Hongbin; Mooney, Tom; Beasley, Matt

    2016-07-01

    Over the past few years the advent of atomic layer deposition (ALD) technology has opened new capabilities to the field of coatings deposition for use in optical elements. At the same time, there have been major advances in both optical designs and detector technologies that can provide orders of magnitude improvement in throughput in the far ultraviolet (FUV) and near ultraviolet (NUV) passbands. Recent review work has shown that a veritable revolution is about to happen in astronomical diagnostic work for targets ranging from protostellar and protoplanetary systems, to the intergalactic medium that feeds gas supplies for galactic star formation, and supernovae and hot gas from star forming regions that determine galaxy formation feedback. These diagnostics are rooted in access to a forest of emission and absorption lines in the ultraviolet (UV)[1], and all that prevents this advance is the lack of throughput in such systems, even in space-based conditions. We outline an approach to use a range of materials to implement stable optical layers suitable for protective overcoats with high UV reflectivity and unprecedented uniformity, and use that capability to leverage innovative ultraviolet/optical filter construction to enable astronomical science. These materials will be deposited in a multilayer format over a metal base to produce a stable construct. Specifically, we will employ the use of PEALD (plasma-enhanced atomic layer deposition) methods for the deposition and construction of reflective layers that can be used to construct unprecedented filter designs for use in the ultraviolet.

  14. Scalability of plasma enhanced atomic layer deposited ruthenium films for interconnect applications

    SciTech Connect

    Swerts, J.; Armini, S.; Carbonell, L.; Delabie, A.; Franquet, A.; Mertens, S.; Popovici, M.; Schaekers, M.; Witters, T.; Toekei, Z.; Beyer, G.; Van Elshocht, S.; Gravey, V.; Cockburn, A.; Shah, K.; Aubuchon, J.

    2012-01-15

    Ru thin films were deposited by plasma enhanced atomic layer deposition using MethylCyclopentadienylPyrrolylRuthenium (MeCpPy)Ru and N{sub 2}/NH{sub 3} plasma. The growth characteristics have been studied on titanium nitride or tantalum nitride substrates of various thicknesses. On SiO{sub 2}, a large incubation period has been observed, which can be resolved by the use of a metal nitride layer of {approx} 0.8 nm. The growth characteristics of Ru layers deposited on ultra-thin metal nitride layers are similar to those on thick metal nitride substrates despite the fact that the metal nitride layers are not fully closed. Scaled Ru/metal nitride stacks were deposited in narrow lines down to 25 nm width. Thinning of the metal nitride does not impact the conformality of the Ru layer in the narrow lines. For the thinnest lines the Ru deposited on the side wall showed a more granular structure when compared to the bottom of the trench, which is attributed to the plasma directionality during the deposition process.

  15. Plasma-Enhanced Atomic Layer Deposition of Silicon Nitride Using a Novel Silylamine Precursor.

    PubMed

    Park, Jae-Min; Jang, Se Jin; Yusup, Luchana L; Lee, Won-Jun; Lee, Sang-Ick

    2016-08-17

    We report the plasma-enhanced atomic layer deposition (PEALD) of silicon nitride thin film using a silylamine compound as the silicon precursor. A series of silylamine compounds were designed by replacing SiH3 groups in trisilylamine by dimethylaminomethylsilyl or trimethylsilyl groups to obtain sufficient thermal stability. The silylamine compounds were synthesized through redistribution, amino-substitution, lithiation, and silylation reactions. Among them, bis(dimethylaminomethylsilyl)trimethylsilyl amine (C9H29N3Si3, DTDN2-H2) was selected as the silicon precursor because of the lowest bond dissociation energy and sufficient vapor pressures. The energies for adsorption and reaction of DTDN2-H2 with the silicon nitride surface were also calculated by density functional theory. PEALD silicon nitride thin films were prepared using DTDN2-H2 and N2 plasma. The PEALD process window was between 250 and 400 °C with a growth rate of 0.36 Å/cycle. The best film quality was obtained at 400 °C with a RF power of 100 W. The PEALD film prepared showed good bottom and sidewall coverages of ∼80% and ∼73%, respectively, on a trench-patterned wafer with an aspect ratio of 5.5.

  16. Current transport mechanisms in plasma-enhanced atomic layer deposited AlN thin films

    SciTech Connect

    Altuntas, Halit E-mail: biyikli@unam.bilkent.edu.tr; Ozgit-Akgun, Cagla; Donmez, Inci; Biyikli, Necmi E-mail: biyikli@unam.bilkent.edu.tr

    2015-04-21

    Here, we report on the current transport mechanisms in AlN thin films deposited at a low temperature (i.e., 200 °C) on p-type Si substrates by plasma-enhanced atomic layer deposition. Structural characterization of the deposited AlN was carried out using grazing-incidence X-ray diffraction, revealing polycrystalline films with a wurtzite (hexagonal) structure. Al/AlN/ p-Si metal-insulator-semiconductor (MIS) capacitor structures were fabricated and investigated under negative bias by performing current-voltage measurements. As a function of the applied electric field, different types of current transport mechanisms were observed; i.e., ohmic conduction (15.2–21.5 MV/m), Schottky emission (23.6–39.5 MV/m), Frenkel-Poole emission (63.8–211.8 MV/m), trap-assisted tunneling (226–280 MV/m), and Fowler-Nordheim tunneling (290–447 MV/m). Electrical properties of the insulating AlN layer and the fabricated Al/AlN/p-Si MIS capacitor structure such as dielectric constant, flat-band voltage, effective charge density, and threshold voltage were also determined from the capacitance-voltage measurements.

  17. Nanocrystalline diamond thin films on titanium-6 aluminum-4 vanadium alloy temporomandibular joint prosthesis simulants by microwave plasma chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Fries, Marc Douglas

    A course of research has been performed to assess the suitability of nanocrystal-line diamond (NCD) films on Ti-6Al-4V alloy as wear-resistant coatings in biomedical implant use. A series of temporomandibular (TMJ) joint condyle simulants were polished and acid-passivated as per ASTM F86 standard for surface preparation of implants. A 3-mum-thick coating of NCD film was deposited by microwave plasma chemical vapor deposition (MPCVD) over the hemispherical articulation surfaces of the simulants. Plasma chemistry conditions were measured and monitored by optical emission spectroscopy (OES), using hydrogen as a relative standard. The films consist of diamond grains around 20 nm in diameter embedded in an amorphous carbon matrix, free of any detectable film stress gradient. Hardness averages 65 GPa and modulus measures 600 GPa at a depth of 250 nm into the film surface. A diffuse film/substrate boundary produces a minimal film adhesion toughness (GammaC) of 158 J/m2. The mean RMS roughness is 14.6 +/- 4.2 nm, with an average peak roughness of 82.6 +/- 65.9 nm. Examination of the surface morphology reveals a porous, dendritic surface. Wear testing resulted in two failed condylar coatings out of three tests. No macroscopic delamination was found on any sample, but micron-scale film pieces broke away, exposing the substrate. Electrochemical corrosion testing shows a seven-fold reduction in corrosion rate with the application of an NCD coating as opposed to polished, passivated Ti-6Al-4V, producing a corrosion rate comparable to wrought Co-Cr-Mo. In vivo biocompatibility testing indicates that implanted NCD films did not elicit an immune response in the rabbit model, and osteointegration was apparent for both compact and trabecular bone on both NCD film and bare Ti-6Al-4V. Overall, NCD thin film material is reasonably smooth, biocompatible, and very well adhered. Wear testing indicates that this material is unacceptable for use in demanding TMJ applications without

  18. Molecular structure and internal rotation of CF₃ group of methyl trifluoroacetate: gas electron diffraction, microwave spectroscopy, and quantum chemical calculation studies.

    PubMed

    Kuze, Nobuhiko; Ishikawa, Atsushi; Kono, Maho; Kobayashi, Takayuki; Fuchisawa, Noriyuki; Tsuji, Takemasa; Takeuchi, Hiroshi

    2015-03-05

    The molecular structure of methyl trifluoroacetate (CF3COOCH3) has been determined by gas electron diffraction (GED), microwave spectroscopy (MW), and quantum chemical calculations (QC). QC study provides the optimized geometries and force constants of the molecule. They were used to estimate the structural model for GED study and to calculate the vibrational corrections for GED and MW data. In addition, potential energy curves for the internal rotations of CF3 and CH3 groups have been calculated for anti (dihedral angle of α(CCOC) is 180°) and syn (α(CCOC) = 0°) conformers of methyl trifluoroacetate. Both the GED and MW data revealed the existence of the anti conformer. Molecular constants determined by MW are A0 = 3613.4(3) MHz, B0 = 1521.146(8) MHz, C0 = 1332.264(9) MHz, ΔJ = 0.09(2) kHz, and ΔJK = 0.23(6) kHz. The GED data were well-reproduced by the analysis in which a large-amplitude motion of the CF3 group was taken into account. The barrier of the internal rotation of the CF3 group was determined to be V3 = 2.3(4) kJ mol(-1), where V3 is the potential coefficient of the assumed potential function, V(ϕ) = (V3/2)(1 - cos 3ϕ), and ϕ is a rotational angle for the CF3 group. The values of geometrical parameters (re structure) of the anti conformer of CF3COOCH3 are r((O═)C-O) = 1.326(6) Å, r(O-CH3) = 1.421(4) Å, r(C-H(in-plane)) = 1.083(14) Å, r(C-H(out-of-plane)) = 1.087(14) Å, r(C═O) = 1.190(7) Å, r(C-C) = 1.533(4) Å, r(C-F(in-plane)) = 1.319(4) Å, r(C-F(out-of-plane)) = 1.320(6) Å, ∠COC = 116.3(5)°, ∠OCH(in-plane) = 105.2° (fixed), ∠OCH(out-of-plane) = 110.0° (fixed), ∠O═CC = 123.7° (fixed), ∠O-CC = 111.2(5)°, ∠OCO = 125.2(5)°, ∠CCF = 110.1(3)°, and OCCF (out-of-plane dihedral angles) = ± 121.5(1)°. Numbers in parentheses are three times the standard deviations of the data fit.

  19. Active microwaves

    NASA Technical Reports Server (NTRS)

    Evans, D.; Vidal-Madjar, D.

    1994-01-01

    Research on the use of active microwaves in remote sensing, presented during plenary and poster sessions, is summarized. The main highlights are: calibration techniques are well understood; innovative modeling approaches have been developed which increase active microwave applications (segmentation prior to model inversion, use of ERS-1 scatterometer, simulations); polarization angle and frequency diversity improves characterization of ice sheets, vegetation, and determination of soil moisture (X band sensor study); SAR (Synthetic Aperture Radar) interferometry potential is emerging; use of multiple sensors/extended spectral signatures is important (increase emphasis).

  20. PECVD of nanostructured SiO2 in a modulated microwave plasma jet at atmospheric pressure

    NASA Astrophysics Data System (ADS)

    Hnilica, J.; Schäfer, J.; Foest, R.; Zajíčková, L.; Kudrle, V.

    2013-08-01

    Atmospheric pressure plasma enhanced chemical vapour deposition (AP-PECVD) of thin films by means of a microwave plasma jet operating with mixtures of argon and tetrakis(trimethylsilyloxy)silane (TTMS) is reported for the first time. In contrast to other siloxy-alkanes that are commonly used for PECVD, the molecule of TTMS (C12H36O4Si5) exhibits a complex and symmetric molecular structure which is presumably essential for a large scale nanostructuring of the films. Deposited films have been characterized by means of electron microscopy (SEM), x-ray spectroscopy (EDX), and infra-red spectroscopy (FTIR). The applied methods demonstrate the prevalent inorganic SiO2-like character of the films and their highly fractalized nanostructure over a wide range of dimension 100-104 nm. Contact angle measurements show the superhydrophobicity of the films, while the dispersive component of the surface energy can be varied in a controlled way by low-frequency amplitude modulation of the excitation power of the MW discharge. The modulation regimes of the jet have been investigated by means of time-resolved optical emission spectroscopy in order to describe the oscillations of plasma parameters e.g. rotational temperature from OH and relative emission of silicon atoms to substantiate the reproducibility of the deposition conditions and to correlate the plasma properties with the resulting film properties.