Lithography-Free Fabrication of Reconfigurable Substrate Topography For Contact Guidance

PubMed Central

Pholpabu, Pitirat; Kustra, Stephen; Wu, Haosheng; Balasubramanian, Aditya; Bettinger, Christopher J.

2014-01-01

Mammalian cells detect and respond to topographical cues presented in natural and synthetic biomaterials both in vivo and in vitro. Micro- and nano-structures influence the adhesion, morphology, proliferation, migration, and differentiation of many phenotypes. Although the mechanisms that underpin cell-topography interactions remain elusive, synthetic substrates with well-defined micro- and nano-structures are important tools to elucidate the origin of these responses. Substrates with reconfigurable topography are desirable because programmable cues can be harmonized with dynamic cellular responses. Here we present a lithography-free fabrication technique that can reversibly present topographical cues using an actuation mechanism that minimizes the confounding effects of applied stimuli. This method utilizes strain-induced buckling instabilities in bi-layer substrate materials with rigid uniform silicon oxide membranes that are thermally deposited on elastomeric substrates. The resulting surfaces are capable of reversible of substrates between three distinct states: flat substrates (A = 1.53 ± 0.55 nm, Rms = 0.317 ± 0.048 nm); parallel wavy grating arrays (A|| = 483.6 ± 7.8 nm and λ|| = 4.78 ± 0.16 μm); perpendicular wavy grating arrays (A⊥ = 429.3 ± 5.8 nm; λ⊥ = 4.95 ± 0.36 μm). The cytoskeleton dynamics of 3T3 fibroblasts in response to these surfaces was measured using optical microscopy. Fibroblasts cultured on dynamic substrates that are switched from flat to topographic features (FLAT-WAVY) exhibit a robust and rapid change in gross morphology as measured by a reduction in circularity from 0.30 ± 0.13 to 0.15 ± 0.08 after 5 min. Conversely, dynamic substrate sequences of FLAT-WAVY-FLAT do not significantly alter the gross steady-state morphology. Taken together, substrates that present topographic structures reversibly can elucidate dynamic aspects of cell-topography interactions. PMID:25468368

Use of Glass Reinforced Concrete (GRC) as a substrate for photovoltaic modules

NASA Technical Reports Server (NTRS)

Eirls, J. L.

1980-01-01

A substrate for flat plate photovoltaic solar panel arrays using a glass fiber reinforced concrete (GRC) material was developed. The installed cost of this GRC panel is 30% less than the cost goal of the Near Term Low-Cost Flat Plate Photovoltaic Solar Array Program. The 4 ft by 8 ft panel is fabricated from readily available inexpensive materials, weighs a nominal 190 lbs., has exceptionally good strength and durability properties (rigid and resists weathering), is amenable to mass production and is easily installed on simple mountings. Solar cells are encapsulated in ethylene/vinyl acetate with Tedlar backing and Korad cover film. The laminates are attached to the GRC substrate with acrylic transfer tape and edge sealed with silicone RTV adhesive.

Hybrid solar cell based on a-Si/polymer flat heterojunction on flexible substrates

NASA Astrophysics Data System (ADS)

Olivares Vargas, A. J.; Mansurova, S.; Cosme, I.; Kosarev, A.; Ospina Ocampo, C. A.; Martinez Mateo, H. E.

2017-08-01

In this work, we present the results of investigation of thin film hybrid organic-inorganic photovoltaic structures based on flat heterojunction hydrogenated silicon (a-Si:H) and poly(3,4 ethylene dioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) fabricated on polyethylene naphthalate (PEN). Different thicknesses of transparent AL doped Zn:O (AZO) electrodes have been tested on PEN substrate and studied by atomic force microscopy (AFM). The AZO films on PEN substrate were statistically processed to obtain surface morphological characteristics, such as root mean square roughness RQ, skewness SK and kurtosis KU. Performance characteristics of fabricated photovoltaic structures have been measured and analyzed for different thicknesses of the transparent electrodes under standard illumination (AM 1.5 I0= 100mW/cm2). Structures on flexible substrates show reproducible performance characteristic as their glass substrate counterpart with values of JSC= 6 mA/cm2, VOC= 0.535 V, FF= 43 % and PCE= 1.41%.

Development of Plastic Substrate Technology for Active Matrix Liquid Crystal Displays Final Report CRADA No. TC-761-93

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carey, P.; Kamath, H.

Raychem Corporation (RYC) and the Lawrence Livermore National Laboratory (LLNL) conducted a development program with the goal to make rugged, low-cost., high-resolution flat panel displays based on RYC's proprietary Nematic Curvilinear Aligned Phase (NCAP) liquid crystal and LLNL's patented processes for the formation and doping of polycrystalline silicon on low-temperature, flexible, plastic substrates.

Fabrication of Robust, Flat, Thinned, UV-Imaging CCDs

NASA Technical Reports Server (NTRS)

Grunthaner, Paula; Elliott, Stythe; Jones, Todd; Nikzad, Shouleh

2004-01-01

An improved process that includes a high-temperature bonding subprocess has been developed to enable the fabrication of robust, flat, silicon-based charge-coupled devices (CCDs) for imaging in ultraviolet (UV) light and/or for detecting low-energy charged particles. The CCDs in question are devices on which CCD circuitry has already been formed and have been thinned for backsurface illumination. These CCDs may be delta doped, and aspects of this type of CCD have been described in several prior articles in NASA Tech Briefs. Unlike prior low-temperature bonding subprocesses based on the use of epoxies or waxes, the high-temperature bonding subprocess is compatible with the deltadoping process as well as with other CCD-fabrication processes. The present improved process and its bonding, thinning, and delta-doping subprocesses, are characterized as postfabrication processes because they are undertaken after the fabrication of CCD circuitry on the front side of a full-thickness silicon substrate. In a typical case, it is necessary to reduce the thickness of the CCD to between 10 and 20 m in order to take advantage of back-side illumination and in order to perform delta doping and/or other back-side treatment to enhance the quantum efficiency. In the prior approach to the fabrication of back-side-illuminated CCDs, the thinning subprocess turned each CCD into a free-standing membrane that was fragile and tended to become wrinkled. In the present improved process, prior to thinning and delta doping, a CCD is bonded on its front side to a silicon substrate that has been prefabricated to include cutouts to accommodate subsequent electrical connections to bonding pads on the CCD circuitry. The substrate provides structural support to increase ruggedness and maintain flatness. At the beginning of this process, the back side of a CCD as fabricated on a full-thickness substrate is polished. Silicon nitride is deposited on the back side, opposite the bonding pads on the front side, in order to define a relatively thick frame. The portion of the CCD not covered by the frame is the portion to be thinned by etching.

Microfabricated instrument for tissue biopsy and analysis

DOEpatents

Krulevitch, Peter A.; Lee, Abraham P.; Northrup, M. Allen; Benett, William J.

1999-01-01

A microfabricated biopsy/histology instrument which has several advantages over the conventional procedures, including minimal specimen handling, smooth cutting edges with atomic sharpness capable of slicing very thin specimens (approximately 2 .mu.m or greater), micro-liter volumes of chemicals for treating the specimens, low cost, disposable, fabrication process which renders sterile parts, and ease of use. The cutter is a "cheese-grater" style design comprising a block or substrate of silicon and which uses anisotropic etching of the silicon to form extremely sharp and precise cutting edges. As a specimen is cut, it passes through the silicon cutter and lies flat on a piece of glass which is bonded to the cutter. Microchannels are etched into the glass or silicon substrates for delivering small volumes of chemicals for treating the specimen. After treatment, the specimens can be examined through the glass substrate. For automation purposes, microvalves and micropumps may be incorporated. Also, specimens in parallel may be cut and treated with identical or varied chemicals. The instrument is disposable due to its low cost and thus could replace current expensive microtome and histology equipment.

Method of fabrication of display pixels driven by silicon thin film transistors

DOEpatents

Carey, Paul G.; Smith, Patrick M.

1999-01-01

Display pixels driven by silicon thin film transistors are fabricated on plastic substrates for use in active matrix displays, such as flat panel displays. The process for forming the pixels involves a prior method for forming individual silicon thin film transistors on low-temperature plastic substrates. Low-temperature substrates are generally considered as being incapable of withstanding sustained processing temperatures greater than about 200.degree. C. The pixel formation process results in a complete pixel and active matrix pixel array. A pixel (or picture element) in an active matrix display consists of a silicon thin film transistor (TFT) and a large electrode, which may control a liquid crystal light valve, an emissive material (such as a light emitting diode or LED), or some other light emitting or attenuating material. The pixels can be connected in arrays wherein rows of pixels contain common gate electrodes and columns of pixels contain common drain electrodes. The source electrode of each pixel TFT is connected to its pixel electrode, and is electrically isolated from every other circuit element in the pixel array.

Soft X-ray multilayers produced by sputtering and molecular beam epitaxy (MBE) - Substrate and interfacial roughness

NASA Astrophysics Data System (ADS)

Kearney, Patrick A.; Slaughter, J. M.; Powers, K. D.; Falco, Charles M.

1988-01-01

Roughness measurements were made on uncoated silicon wafers and float glass using a WYKO TOPO-3D phase shifting interferometry, and the results are reported. The wafers are found to be slightly smoother than the flat glass. The effects of different cleaning methods and of the deposition of silicon 'buffer layers' on substrate roughness are examined. An acid cleaning method is described which gives more consistent results than detergent cleaning. Healing of the roughness due to sputtered silicon buffer layers was not observed on the length scale probed by the WYKO. Sputtered multilayers are characterized using both the WYKO interferometer and low-angle X-ray diffraction in order to yield information about the roughness of the top surface and of the multilayer interfaces. Preliminary results on film growth using molecular beam epitaxy are also presented.

Conceptual design study of concentrator enhanced solar arrays for space applications. 2kW Si and GaAs systems at 1 AU

NASA Technical Reports Server (NTRS)

1980-01-01

The effect of concentration level on the specific power for a deployable, thin, gallium arsenide cell array in geosynchronous orbit for 10 years in conjunction with a two dimensional flat plate trough concentrator (V trough) and also with a multiple flat plate concentrator was investigated as well as the effects for a conventional silicon cell array on a rigid substrate. For application to a thin GaAs array at 1 AU for 10 years, the V trough produces a 19% benefit in specific power and a dramatic reduction in array area, while the multiple flat plate collector design is not only of no benefit, but is a considerable detriment. The benefit it achieves by reducing array area is duplicated by the 2D design. For the silicon array on a rigid substrate, improvement in performance due to a concentrator with ordinary mirror coating is quite small: 9% increase in specific power, and 13% reduction in array area. When the concentrator mirrors are coated with an improved cold mirror coating, somewhat more significant results are obtained: 31% specific power improvement; and 27% area reduction. In both cases, a 10 year exposure reduces BOL output by 23%.

Novel silicon microchannels device for use in red blood cell deformability studies

NASA Astrophysics Data System (ADS)

Zheng, Xiao-Lin; Liao, Yan-Jian; Zhang, Wen-Xian

2001-10-01

Currently, a number of techniques are used to access cell deformability. We study a novel silicon microchannels device for use in red blood cell deformability. The channels are produced in silicon substrate using microengineering technology. The microgrooves formed in the surface of a single-crystal silicon substrate. They were converted to channels by tightly covering them with an optical flat glass plate. An array of flow channels (number 950 in parallel) have typical dimensions of 5 micrometers width X 5.5 Xm depth, and 30 micrometers length. There the RBC's are forced to pass through channels. Thus, the microchannels are used to simulate human blood capillaries. It provides a specific measurement of individual cell in terms of both flow velocity profile and an index of cell volume while the cell flow through the channels. It dominates the complex cellular flow behavior, such as, the viscosity of whole blood is a nonlinear function of shear rate, index of filtration, etc.

Stability of Polymer Ultrathin Films (<7 nm) Made by a Top-Down Approach.

PubMed

Bal, Jayanta Kumar; Beuvier, Thomas; Unni, Aparna Beena; Chavez Panduro, Elvia Anabela; Vignaud, Guillaume; Delorme, Nicolas; Chebil, Mohamed Souheib; Grohens, Yves; Gibaud, Alain

2015-08-25

In polymer physics, the dewetting of spin-coated polystyrene ultrathin films on silicon remains mysterious. By adopting a simple top-down method based on good solvent rinsing, we are able to prepare flat polystyrene films with a controlled thickness ranging from 1.3 to 7.0 nm. Their stability was scrutinized after a classical annealing procedure above the glass transition temperature. Films were found to be stable on oxide-free silicon irrespective of film thickness, while they were unstable (<2.9 nm) and metastable (>2.9 nm) on 2 nm oxide-covered silicon substrates. The Lifshitz-van der Waals intermolecular theory that predicts the domains of stability as a function of the film thickness and of the substrate nature is now fully reconciled with our experimental observations. We surmise that this reconciliation is due to the good solvent rinsing procedure that removes the residual stress and/or the density variation of the polystyrene films inhibiting thermodynamically the dewetting on oxide-free silicon.

Unidirectional endotaxial cobalt di-silicide nanowires on Si(110) substrates

NASA Astrophysics Data System (ADS)

Mahato, J. C.; Das, Debolina; Banu, Nasrin; Satpati, Biswarup; Dev, B. N.

2017-10-01

Self-organized growth of well-ordered endotaxial silicide nanowires (NWs) on clean Si(110) surfaces has been investigated by in situ scanning tunneling microscopy (STM) and transmission electron microscopy (TEM). Co deposition on clean Si(110) reconstructed surfaces at ∼600 °C produces unidirectional CoSi2 NWs by reaction of cobalt with the hot silicon substrate. STM investigations reveal four major types of distinct NWs, all growing along the [-110] in-plane direction except one type growing along the in-plane [-113] direction. There are also some nanodots. The cross-sectional TEM measurements show that the unidirectional NWs are of two types—flat-top and ridged. The NWs grow not only on the substrate but also into the substrate. CoSi2 in flat top NWs are in the same crystallographic orientation as the substrate Si and the buried interfaces between CoSi2 and Si are A-type. In the ridged NWs CoSi2 and Si are in different crystallographic orientations and the interfaces are B-type. The ridged NWs are in general wider and grow deeper into the substrate.

Unidirectional endotaxial cobalt di-silicide nanowires on Si(110) substrates.

PubMed

Mahato, J C; Das, Debolina; Banu, Nasrin; Satpati, Biswarup; Dev, B N

2017-10-20

Self-organized growth of well-ordered endotaxial silicide nanowires (NWs) on clean Si(110) surfaces has been investigated by in situ scanning tunneling microscopy (STM) and transmission electron microscopy (TEM). Co deposition on clean Si(110) reconstructed surfaces at ∼600 °C produces unidirectional CoSi 2 NWs by reaction of cobalt with the hot silicon substrate. STM investigations reveal four major types of distinct NWs, all growing along the [-110] in-plane direction except one type growing along the in-plane [-113] direction. There are also some nanodots. The cross-sectional TEM measurements show that the unidirectional NWs are of two types-flat-top and ridged. The NWs grow not only on the substrate but also into the substrate. CoSi 2 in flat top NWs are in the same crystallographic orientation as the substrate Si and the buried interfaces between CoSi 2 and Si are A-type. In the ridged NWs CoSi 2 and Si are in different crystallographic orientations and the interfaces are B-type. The ridged NWs are in general wider and grow deeper into the substrate.

Hydrostatic and Flow Measurements on Wrinkled Membrane Walls

NASA Astrophysics Data System (ADS)

Ozsun, Ozgur; Ekinci, Kamil

2013-03-01

In this study, we investigate structural properties of wrinkled silicon nitride (SiN) membranes, under both hydrostatic perturbations and flow conditions, through surface profile measurements. Rectangular SiN membranes with linear dimensions of 15 mm × 1 . 5 mm × 1 μ m are fabricated on a 500 - μ m-thick silicon substrate using standard lithography techniques. These thin, initially flat, tension-dominated membranes are wrinkled by bending the silicon substrate. The wrinkled membranes are subsequently incorporated as walls into rectangular micro-channels, which allow both hydrostatic and flow measurements. The structural response of the wrinkles to hydrostatic pressure provides a measure of the various energy scales in the problem. Flow experiments show that the elastic properties and the structural undulations on a compliant membrane completely dominate the flow, possibly providing drag reduction. These measurements pave the way for building and using compliant walls for drag reduction in micro-channels.

Large-Area Direct Hetero-Epitaxial Growth of 1550-nm InGaAsP Multi-Quantum-Well Structures on Patterned Exact-Oriented (001) Silicon Substrates by Metal Organic Chemical Vapor Deposition

NASA Astrophysics Data System (ADS)

Megalini, Ludovico; Cabinian, Brian C.; Zhao, Hongwei; Oakley, Douglas C.; Bowers, John E.; Klamkin, Jonathan

2018-02-01

We employ a simple two-step growth technique to grow large-area 1550-nm laser structures by direct hetero-epitaxy of III-V compounds on patterned exact-oriented (001) silicon (Si) substrates by metal organic chemical vapor deposition. Densely-packed, highly uniform, flat and millimeter-long indium phosphide (InP) nanowires were grown from Si v-grooves separated by silicon dioxide (SiO2) stripes with various widths and pitches. Following removal of the SiO2 patterns, the InP nanowires were coalesced and, subsequently, 1550-nm laser structures were grown in a single overgrowth without performing any polishing for planarization. X-ray diffraction, photoluminescence, atomic force microscopy and transmission electron microscopy analyses were used to characterize the epitaxial material. PIN diodes were fabricated and diode-rectifying behavior was observed.

Peel-and-Stick: Fabricating Thin Film Solar Cell on Universal Substrates

PubMed Central

Lee, Chi Hwan; Kim, Dong Rip; Cho, In Sun; William, Nemeth; Wang, Qi; Zheng, Xiaolin

2012-01-01

Fabrication of thin-film solar cells (TFSCs) on substrates other than Si and glass has been challenging because these nonconventional substrates are not suitable for the current TFSC fabrication processes due to poor surface flatness and low tolerance to high temperature and chemical processing. Here, we report a new peel-and-stick process that circumvents these fabrication challenges by peeling off the fully fabricated TFSCs from the original Si wafer and attaching TFSCs to virtually any substrates regardless of materials, flatness and rigidness. With the peel-and-stick process, we integrated hydrogenated amorphous silicon (a-Si:H) TFSCs on paper, plastics, cell phone and building windows while maintaining the original 7.5% efficiency. The new peel-and-stick process enables further reduction of the cost and weight for TFSCs and endows TFSCs with flexibility and attachability for broader application areas. We believe that the peel-and-stick process can be applied to thin film electronics as well. PMID:23277871

Peel-and-Stick: Fabricating Thin Film Solar Cell on Universal Substrates

NASA Astrophysics Data System (ADS)

Lee, Chi Hwan; Kim, Dong Rip; Cho, In Sun; William, Nemeth; Wang, Qi; Zheng, Xiaolin

2012-12-01

Fabrication of thin-film solar cells (TFSCs) on substrates other than Si and glass has been challenging because these nonconventional substrates are not suitable for the current TFSC fabrication processes due to poor surface flatness and low tolerance to high temperature and chemical processing. Here, we report a new peel-and-stick process that circumvents these fabrication challenges by peeling off the fully fabricated TFSCs from the original Si wafer and attaching TFSCs to virtually any substrates regardless of materials, flatness and rigidness. With the peel-and-stick process, we integrated hydrogenated amorphous silicon (a-Si:H) TFSCs on paper, plastics, cell phone and building windows while maintaining the original 7.5% efficiency. The new peel-and-stick process enables further reduction of the cost and weight for TFSCs and endows TFSCs with flexibility and attachability for broader application areas. We believe that the peel-and-stick process can be applied to thin film electronics as well.

Combining light-harvesting with detachability in high-efficiency thin-film silicon solar cells.

PubMed

Ram, Sanjay K; Desta, Derese; Rizzoli, Rita; Bellettato, Michele; Lyckegaard, Folmer; Jensen, Pia B; Jeppesen, Bjarke R; Chevallier, Jacques; Summonte, Caterina; Larsen, Arne Nylandsted; Balling, Peter

2017-06-01

Efforts to realize thin-film solar cells on unconventional substrates face several obstacles in achieving good energy-conversion efficiency and integrating light-management into the solar cell design. In this report a technique to circumvent these obstacles is presented: transferability and an efficient light-harvesting scheme are combined for thin-film silicon solar cells by the incorporation of a NaCl layer. Amorphous silicon solar cells in p-i-n configuration are fabricated on reusable glass substrates coated with an interlayer of NaCl. Subsequently, the solar cells are detached from the substrate by dissolution of the sacrificial NaCl layer in water and then transferred onto a plastic sheet, with a resultant post-transfer efficiency of 9%. The light-trapping effect of the surface nanotextures originating from the NaCl layer on the overlying solar cell is studied theoretically and experimentally. The enhanced light absorption in the solar cells on NaCl-coated substrates leads to significant improvement in the photocurrent and energy-conversion efficiency in solar cells with both 350 and 100 nm thick absorber layers, compared to flat-substrate solar cells. Efficient transferable thin-film solar cells hold a vast potential for widespread deployment of off-grid photovoltaics and cost reduction.

Fabrication of silicon-on-diamond substrate with an ultrathin SiO2 bonding layer

NASA Astrophysics Data System (ADS)

Nagata, Masahiro; Shirahama, Ryouya; Duangchan, Sethavut; Baba, Akiyoshi

2018-06-01

We proposed and demonstrated a sputter etching method to prepare both a flat surface (root-mean-square surface roughness of approximately 0.2–0.3 nm) and an ultrathin SiO2 bonding layer at an accuracy of approximately 5 nm in thickness to fabricate a silicon-on-diamond substrate (SOD). We also investigated a plasma activation method on a SiO2 surface using various gases. We found that O2 plasma activation is more suitable for the bonding between SiO2 and Si than N2 or Ar plasma activation. We speculate that the concentration of hydroxyl groups on the SiO2 surface was increased by O2 plasma activation. We fabricated the SOD substrate with an ultrathin (15 nm in thickness) SiO2 bonding layer using the sputter etching and O2 plasma activation methods.

Self-organized broadband light trapping in thin film amorphous silicon solar cells.

PubMed

Martella, C; Chiappe, D; Delli Veneri, P; Mercaldo, L V; Usatii, I; Buatier de Mongeot, F

2013-06-07

Nanostructured glass substrates endowed with high aspect ratio one-dimensional corrugations are prepared by defocused ion beam erosion through a self-organized gold (Au) stencil mask. The shielding action of the stencil mask is amplified by co-deposition of gold atoms during ion bombardment. The resulting glass nanostructures enable broadband anti-reflection functionality and at the same time ensure a high efficiency for diffuse light scattering (Haze). It is demonstrated that the patterned glass substrates exhibit a better photon harvesting than the flat glass substrate in p-i-n type thin film a-Si:H solar cells.

Dynamic Roughness Ratio-Based Framework for Modeling Mixed Mode of Droplet Evaporation.

PubMed

Gunjan, Madhu Ranjan; Raj, Rishi

2017-07-18

The spatiotemporal evolution of an evaporating sessile droplet and its effect on lifetime is crucial to various disciplines of science and technology. Although experimental investigations suggest three distinct modes through which a droplet evaporates, namely, the constant contact radius (CCR), the constant contact angle (CCA), and the mixed, only the CCR and the CCA modes have been modeled reasonably. Here we use experiments with water droplets on flat and micropillared silicon substrates to characterize the mixed mode. We visualize that a perfect CCA mode after the initial CCR mode is an idealization on a flat silicon substrate, and the receding contact line undergoes intermittent but recurring pinning (CCR mode) as it encounters fresh contaminants on the surface. The resulting increase in roughness lowers the contact angle of the droplet during these intermittent CCR modes until the next depinning event, followed by the CCA mode of evaporation. The airborne contaminants in our experiments are mostly loosely adhered to the surface and travel along with the receding contact line. The resulting gradual increase in the apparent roughness and hence the extent of CCR mode over CCA mode forces appreciable decrease in the contact angle observed during the mixed mode of evaporation. Unlike loosely adhered airborne contaminants on flat samples, micropillars act as fixed roughness features. The apparent roughness fluctuates about the mean value as the contact line recedes between pillars. Evaporation on these surfaces exhibits stick-jump motion with a short-duration mixed mode toward the end when the droplet size becomes comparable to the pillar spacing. We incorporate this dynamic roughness into a classical evaporation model to accurately predict the droplet evolution throughout the three modes, for both flat and micropillared silicon surfaces. We believe that this framework can also be extended to model the evaporation of nanofluids and the coffee-ring effect, among others.

Fabrication Methods for Adaptive Deformable Mirrors

NASA Technical Reports Server (NTRS)

Toda, Risaku; White, Victor E.; Manohara, Harish; Patterson, Keith D.; Yamamoto, Namiko; Gdoutos, Eleftherios; Steeves, John B.; Daraio, Chiara; Pellegrino, Sergio

2013-01-01

Previously, it was difficult to fabricate deformable mirrors made by piezoelectric actuators. This is because numerous actuators need to be precisely assembled to control the surface shape of the mirror. Two approaches have been developed. Both approaches begin by depositing a stack of piezoelectric films and electrodes over a silicon wafer substrate. In the first approach, the silicon wafer is removed initially by plasmabased reactive ion etching (RIE), and non-plasma dry etching with xenon difluoride (XeF2). In the second approach, the actuator film stack is immersed in a liquid such as deionized water. The adhesion between the actuator film stack and the substrate is relatively weak. Simply by seeping liquid between the film and the substrate, the actuator film stack is gently released from the substrate. The deformable mirror contains multiple piezoelectric membrane layers as well as multiple electrode layers (some are patterned and some are unpatterned). At the piezolectric layer, polyvinylidene fluoride (PVDF), or its co-polymer, poly(vinylidene fluoride trifluoroethylene P(VDF-TrFE) is used. The surface of the mirror is coated with a reflective coating. The actuator film stack is fabricated on silicon, or silicon on insulator (SOI) substrate, by repeatedly spin-coating the PVDF or P(VDFTrFE) solution and patterned metal (electrode) deposition. In the first approach, the actuator film stack is prepared on SOI substrate. Then, the thick silicon (typically 500-micron thick and called handle silicon) of the SOI wafer is etched by a deep reactive ion etching process tool (SF6-based plasma etching). This deep RIE stops at the middle SiO2 layer. The middle SiO2 layer is etched by either HF-based wet etching or dry plasma etch. The thin silicon layer (generally called a device layer) of SOI is removed by XeF2 dry etch. This XeF2 etch is very gentle and extremely selective, so the released mirror membrane is not damaged. It is possible to replace SOI with silicon substrate, but this will require tighter DRIE process control as well as generally longer and less efficient XeF2 etch. In the second approach, the actuator film stack is first constructed on a silicon wafer. It helps to use a polyimide intermediate layer such as Kapton because the adhesion between the polyimide and silicon is generally weak. A mirror mount ring is attached by using adhesive. Then, the assembly is partially submerged in liquid water. The water tends to seep between the actuator film stack and silicon substrate. As a result, the actuator membrane can be gently released from the silicon substrate. The actuator membrane is very flat because it is fixed to the mirror mount prior to the release. Deformable mirrors require extremely good surface optical quality. In the technology described here, the deformable mirror is fabricated on pristine substrates such as prime-grade silicon wafers. The deformable mirror is released by selectively removing the substrate. Therefore, the released deformable mirror surface replicates the optical quality of the underlying pristine substrate.

Structure disorder degree of polysilicon thin films grown by different processing: Constant C from Raman spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Quan, E-mail: wangq@mail.ujs.edu.cn; State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000; Zhang, Yanmin

2013-11-14

Flat, low-stress, boron-doped polysilicon thin films were prepared on single crystalline silicon substrates by low pressure chemical vapor deposition. It was found that the polysilicon films with different deposition processing have different microstructure properties. The confinement effect, tensile stresses, defects, and the Fano effect all have a great influence on the line shape of Raman scattering peak. But the effect results are different. The microstructure and the surface layer are two important mechanisms dominating the internal stress in three types of polysilicon thin films. For low-stress polysilicon thin film, the tensile stresses are mainly due to the change of microstructuremore » after thermal annealing. But the tensile stresses in flat polysilicon thin film are induced by the silicon carbide layer at surface. After the thin film doped with boron atoms, the phenomenon of the tensile stresses increasing can be explained by the change of microstructure and the increase in the content of silicon carbide. We also investigated the disorder degree states for three polysilicon thin films by analyzing a constant C. It was found that the disorder degree of low-stress polysilicon thin film larger than that of flat and boron-doped polysilicon thin films due to the phase transformation after annealing. After the flat polysilicon thin film doped with boron atoms, there is no obvious change in the disorder degree and the disorder degree in some regions even decreases.« less

Protecting the properties of monolayer MoS 2 on silicon based substrates with an atomically thin buffer

DOE PAGES

Man, Michael K. L.; Deckoff-Jones, Skylar; Winchester, Andrew; ...

2016-02-12

Semiconducting 2D materials, like transition metal dichalcogenides (TMDs), have gained much attention for their potential in opto-electronic devices, valleytronic schemes, and semi-conducting to metallic phase engineering. However, like graphene and other atomically thin materials, they lose key properties when placed on a substrate like silicon, including quenching of photoluminescence, distorted crystalline structure, and rough surface morphology. The ability to protect these properties of monolayer TMDs, such as molybdenum disulfide (MoS 2), on standard Si-based substrates, will enable their use in opto-electronic devices and scientific investigations. Here we show that an atomically thin buffer layer of hexagonal-boron nitride (hBN) protects themore » range of key opto-electronic, structural, and morphological properties of monolayer MoS 2 on Si-based substrates. The hBN buffer restores sharp diffraction patterns, improves monolayer flatness by nearly two-orders of magnitude, and causes over an order of magnitude enhancement in photoluminescence, compared to bare Si and SiO 2 substrates. Lastly, our demonstration provides a way of integrating MoS 2 and other 2D monolayers onto standard Si-substrates, thus furthering their technological applications and scientific investigations.« less

Template-assisted electrodeposition of Ni and Ni/Au nanowires on planar and curved substrates

NASA Astrophysics Data System (ADS)

Guiliani, Jason; Cadena, John; Monton, Carlos

2018-02-01

We present a variant of the template-assisted electrodeposition method that enables the synthesis of large arrays of nanowires (NWs) on flat and curved substrates. This method uses ultra-thin (50 nm-10 μm) anodic aluminum oxide membranes as a template. We have developed a procedure that uses a two-polymer protective layer to transfer these templates onto almost any surface. We have applied this technique to the fabrication of large arrays of Ni and segmented composition Ni/Au NWs on silicon wafers, Cu tapes, and thin (0.2 mm) Cu wires. In all cases, a complete coverage with NWs is achieved. The magnetic properties of these samples show an accentuated in-plane anisotropy which is affected by the form of the substrate (flat or curve) and the length of the NWs. Unlike current lithography techniques, the fabrication method proposed here allows the integration of complex nanostructures into devices, which can be fabricated on unconventional surfaces.

Highly Anisotropic Adhesive Film Made from Upside-Down, Flat, and Uniform Vertically Aligned CNTs.

PubMed

Hong, Sanghyun; Lundstrom, Troy; Ghosh, Ranajay; Abdi, Hamed; Hao, Ji; Jeoung, Sun Kyoung; Su, Paul; Suhr, Jonghwan; Vaziri, Ashkan; Jalili, Nader; Jung, Yung Joon

2016-12-14

We have created a multifunctional dry adhesive film with transferred vertically aligned carbon nanotubes (VA-CNTs). This unique VA-CNT film was fabricated by a multistep transfer process, converting the flat and uniform bottom of VA-CNTs grown on atomically flat silicon wafer substrates into the top surface of an adhesive layer. Unlike as-grown VA-CNTs, which have a nonuniform surface, randomly entangled CNT arrays, and a weak interface between the CNTs and substrates, this transferred VA-CNT film shows an extremely high coefficient of static friction (COF) of up to 60 and a shear adhesion force 30 times higher (12 N/cm 2 ) than that of the as-grown VA-CNTs under a very small preloading of 0.2 N/cm 2 . Moreover, a near-zero normal adhesion force was observed with 20 mN/cm 2 preloading and a maximum 100-μm displacement in a piezo scanner, demonstrating ideal properties for an artificial gecko foot. Using this unique structural feature and anisotropic adhesion properties, we also demonstrate effective removal and assembly of nanoparticles into organized micrometer-scale circular and line patterns by a single brushing of this flat and uniform VA-CNT film.

Effect of substrates on the molecular orientation of silicon phthalocyanine dichloride thin films

NASA Astrophysics Data System (ADS)

Deng, Juzhi; Baba, Yuji; Sekiguchi, Tetsuhiro; Hirao, Norie; Honda, Mitsunori

2007-05-01

Molecular orientations of silicon phthalocyanine dichloride (SiPcCl2) thin films deposited on three different substrates have been measured by near-edge x-ray absorption fine structure (NEXAFS) spectroscopy using linearly polarized synchrotron radiation. The substrates investigated were highly oriented pyrolitic graphite (HOPG), polycrystalline gold and indium tin oxide (ITO). For thin films of about five monolayers, the polarization dependences of the Si K-edge NEXAFS spectra showed that the molecular planes of SiPcCl2 on three substrates were nearly parallel to the surface. Quantitative analyses of the polarization dependences revealed that the tilted angle on HOPG was only 2°, which is interpreted by the perfect flatness of the HOPG surface. On the other hand, the tilted angle on ITO was 26°. Atomic force microscopy (AFM) observation of the ITO surface showed that the periodicity of the horizontal roughness is of the order of a few nanometres, which is larger than the molecular size of SiPcCl2. It is concluded that the morphology of the top surface layer of the substrate affects the molecular orientation of SiPcCl2 molecules not only for mono-layered adsorbates but also for multi-layered thin films.

A study to improve the mechanical properties of silicon carbide ribbon fibers

NASA Technical Reports Server (NTRS)

Debolt, H. E.; Robey, R. J.

1976-01-01

Preliminary deposition studies of SiC ribbon on a carbon ribbon substrate showed that the dominant strength limiting flaws were at the substrate surface. Procedures for making the carbon ribbon substrate from polyimide film were improved, providing lengths up to 450 meters (1,500 ft.) of flat carbon ribbon substrate 1,900 microns (75 mils) wide by 25 microns (1 mil) thick. The flaws on the carbon ribbon were smaller and less frequent than on carbon ribbon used earlier. SiC ribbon made using the improved substrate, including a layer of pyrolytic graphite to reduce further the severity of substrate surface flaws, showed strength levels up to the 2,068 MPa (300 Ksi) target of the program, with average strength levels over 1,700 MPa (250 Ksi) with coefficient of variation as low as 10% for some runs.

Sub-10 nm Silicon Nanopillar Fabrication Using Fast and Brushless Thermal Assembly of PS-b-PDMS Diblock Copolymer.

PubMed

Garnier, Jérôme; Arias-Zapata, Javier; Marconot, Olivier; Arnaud, Sandrine; Böhme, Sophie; Girardot, Cécile; Buttard, Denis; Zelsmann, Marc

2016-04-20

A new approach to obtaining spherical nanodomains using polystyrene-block-polydimethylsiloxane (PS-b-PDMS) is proposed. To reduce drastically the process time, we blended a copolymer with cylindrical morphology with a PS homopolymer. Adding PS homopolymer into a low-molar-mass cylindrical morphology PS-b-PDMS system drives it toward a spherical morphology. Besides, by controlling the as-spun state, spherical PDMS nanodomains could be kept and thermally arranged. This PS-homopolymer addition allows not only an efficient, purely thermal arrangement process of spheres but also the ability to work directly on nontreated silicon substrates. Indeed, as shown by STEM measurements, no PS brush surface treatment was necessary in our study to avoid a PDMS wetting layer at the interface with the Si substrate. Our approach was compared to a sphere-forming diblock copolymer, which needs a longer thermal annealing. Furthermore, GISAXS measurements provided complete information on PDMS sphere features. Excellent long-range order spherical microdomains were therefore produced on flat surfaces and inside graphoepitaxy trenches with a period of 21 nm, as were in-plane spheres with a diameter of 8 nm with a 15 min thermal annealing. Finally, direct plasma-etching transfer into the silicon substrate was demonstrated, and 20 nm high silicon nanopillars were obtained, which are very promising results for various nanopatterning applications.

Electrochemical growth of controlled tip shapes of ZnO nanorod arrays on silicon substrate and enhanced photoluminescence emission from nanopyramid arrays compared with flat-head nanorods

NASA Astrophysics Data System (ADS)

Alimanesh, Mahmoud; Hassan, Z.; Zainal, Norzaini

2017-10-01

Zinc oxide (ZnO) nanorod arrays (NRAs) with different morphologies such as; perfect hexagon flat-head, pyramidal, compact pencil, nail-shaped, and high-compact ZnO nanorod thin films, were successfully grown on silicon substrates. These NRAs were formed on substrates using a simple low-temperature electrochemical method without adding any catalyst or template via the precursors of zinc nitrate hexahydrate [Zn(NO3)2·6H2O] and hexamethylenetetramine [HMT; C6H12N4] with an equal molar concentration of 0.025 mol/l. The morphologies of the ZnO nanorods (NRs) could be controlled and transformed successfully in to other morphologies by changing the growth conditions, such as; growth temperature and applied current density. Detailed structural investigations reveal that the synthesized various NRs are single crystalline with wurtzite hexagonal phase and preferentially grow along the c-axis direction. The room temperature photoluminescence spectra show that each spectrum consists of an ultraviolet (UV) band and a relative broad visible light emission and infrared emission peak. The enhanced light emission intensity at UV peak (∼375 nm) is observed significantly from ZnO nanopyramid (NP) arrays because of the conical shape of NP. The photoluminescence intensity of the UV peak from the NPs is found to be 1.5-17 times larger than those from the other various NRs.

Investigation of test methods, material properties, and processes for solar cell encapsulants. Encapsulation task of the low-cost silicon solar array project

NASA Technical Reports Server (NTRS)

1977-01-01

During this quarter, flat-plate solar collector systems were considered and six basic construction elements were identified: outer coatings, superstrates, pottants, substrates, undercoats, and adhesives. Materials surveys were then initiated to discover either generic classes or/and specific products to function as each construction element. Cost data included in the surveys permit ready evaluation of each material. Silicones, fluorocarbons, glass, and acrylic polymers have the highest inherent weatherability of materials studied to date. Only acrylics, however, combine low costs, environmental resistance, and potential processability. This class will receive particular emphasis.

Self-organized, effective medium black silicon antireflection structures for silicon optics in the mid-infrared

NASA Astrophysics Data System (ADS)

Steglich, Martin; Käsebier, Thomas; Kley, Ernst-Bernhard; Tünnermann, Andreas

2016-09-01

Thanks to its high quality and low cost, silicon is the material of choice for optical devices operating in the mid-infrared (MIR; 2 μm to 6 μm wavelength). Unfortunately in this spectral region, the refractive index is comparably high (about 3.5) and leads to severe reflection losses of about 30% per interface. In this work, we demonstrate that self-organized, statistical Black Silicon structures, fabricated by Inductively Coupled Plasma Reactive Ion Etching (ICP-RIE), can be used to effectively suppress interface reflection. More importantly, it is shown that antireflection can be achieved in an image-preserving, non-scattering way. This enables Black Silicon antireflection structures (ARS) for imaging applications in the MIR. It is demonstrated that specular transmittances of 97% can be easily achieved on both flat and curved substrates, e.g. lenses. Moreover, by a combined optical and morphological analysis of a multitude of different Black Silicon ARS, an effective medium criterion for the examined structures is derived that can also be used as a design rule for maximizing sample transmittance in a desired wavelength range. In addition, we show that the mechanical durability of the structures can be greatly enhanced by coating with hard dielectric materials like diamond-like carbon (DLC), hence enabling practical applications. Finally, the distinct advantages of statistical Black Silicon ARS over conventional AR layer stacks are discussed: simple applicability to topological substrates, absence of thermal stress and cost-effectiveness.

Micromachined Tunable Fabry-Perot Filters for Infrared Astronomy

NASA Technical Reports Server (NTRS)

Barclay, Richard; Bier, Alexander; Chen, Tina; DiCamillo, Barbara; Deming, Drake; Greenhouse, Matthew; Henry, Ross; Hewagama, Tilak; Jacobson, Mindy; Loughlin, James;

Identifying suitable substrates for high-quality graphene-based heterostructures

NASA Astrophysics Data System (ADS)

Banszerus, L.; Janssen, H.; Otto, M.; Epping, A.; Taniguchi, T.; Watanabe, K.; Beschoten, B.; Neumaier, D.; Stampfer, C.

2017-06-01

We report on a scanning confocal Raman spectroscopy study investigating the strain-uniformity and the overall strain and doping of high-quality chemical vapour deposited (CVD) graphene-based heterostuctures on a large number of different substrate materials, including hexagonal boron nitride (hBN), transition metal dichalcogenides, silicon, different oxides and nitrides, as well as polymers. By applying a hBN-assisted, contamination free, dry transfer process for CVD graphene, high-quality heterostructures with low doping densities and low strain variations are assembled. The Raman spectra of these pristine heterostructures are sensitive to substrate-induced doping and strain variations and are thus used to probe the suitability of the substrate material for potential high-quality graphene devices. We find that the flatness of the substrate material is a key figure for gaining, or preserving high-quality graphene.

Application of Self-Assembled Monolayers to the Electroless Metallization of High Aspect Ratio Vias for Microelectronics

NASA Astrophysics Data System (ADS)

Bernasconi, R.; Molazemhosseini, A.; Cervati, M.; Armini, S.; Magagnin, L.

2016-10-01

All-wet electroless metallization of through-silicon vias (TSVs) with a width of 5 μm and a 1:10 aspect ratio was carried out. Immersion in a n-(2-aminoethyl) 3-aminopropyl-trimethoxysilane (AEAPTMS) self-assembled monolayer (SAM) was used to enhance the adhesion between the metal film and substrate. Contact angle variation and atomic force microscopy were used to verify the formation of a SAM layer. A PdCl2 solution was later used to activate the silanized substrates, exploiting the affinity of the -NH3 functional group of AEAPTMS to palladium. A nickel-phosphorus-boron electroless bath was employed to deposit the first barrier layer onto silicon. The NiPB growth rate was evaluated on flat silicon wafers, while the structure of the coating obtained was investigated via glow discharge optical emission spectroscopy. Cross-sectional scanning electron microscope observations were carried out on metallized TSVs to characterize the NiPB seed, the Cu seed layer deposited with a second electroless step, and the Cu superfilling obtained with a commercial solution. Complete filling of TSV was achieved.

Characterization of Silicon Moth-Eye Antireflection Coatings for Astronomical Applications in the Infrared

NASA Astrophysics Data System (ADS)

Jeram, Sarik; Ge, Jian; Jiang, Peng; Phillips, Blayne

2016-01-01

Silicon moth-eye antireflective structures have emerged to be an excellent approachfor reducing the amount of light that is lost upon incidence on a given surface of optics made of silicon. This property has been exploited for a wide variety of products ranging from eyeglasses and flat-panel displays to solar panels. These materials typically come in the form of coatings that are applied to an optical substrate such as glass. Moth-eye coatings, made of a periodic array of subwavelength pillars on silicon substrates or other substrates, can produce the desired antireflection (AR) performance for a broad wavelength range and over a wide range of incident angles. In the field of astronomy, every photon striking a detector is significant - and thus, losses from reflectivity at the various optical interfaces before a detector can have significant implications to the science at hand. Moth-eye AR coatings on these optical interfaces may minimize their reflection losses while maximizing light throughput for a multitude of different astronomical instruments. In addition, moth-eye AR coatings, which are patterned directly on silicon surfaces, can significantly enhance the coating durability. At the University of Florida, we tested two moth-eye filters designed for use in the near-infrared regime at 1-8 microns by examining their optical properties, such as transmission, the scattered light, and wavefront quality, and testing the coatings at cryogenic temperatures to characterize their viability for use in both ground- and space-based infrared instruments. This presentation will report our lab evaluation results.

III/V nano ridge structures for optical applications on patterned 300 mm silicon substrate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kunert, B.; Guo, W.; Mols, Y.

We report on an integration approach of III/V nano ridges on patterned silicon (Si) wafers by metal organic vapor phase epitaxy (MOVPE). Trenches of different widths (≤500 nm) were processed in a silicon oxide (SiO{sub 2}) layer on top of a 300 mm (001) Si substrate. The MOVPE growth conditions were chosen in a way to guarantee an efficient defect trapping within narrow trenches and to form a box shaped ridge with increased III/V volume when growing out of the trench. Compressively strained InGaAs/GaAs multi-quantum wells with 19% indium were deposited on top of the fully relaxed GaAs ridges as an activemore » material for optical applications. Transmission electron microcopy investigation shows that very flat quantum well (QW) interfaces were realized. A clear defect trapping inside the trenches is observed whereas the ridge material is free of threading dislocations with only a very low density of planar defects. Pronounced QW photoluminescence (PL) is detected from different ridge sizes at room temperature. The potential of these III/V nano ridges for laser integration on Si substrates is emphasized by the achieved ridge volume which could enable wave guidance and by the high crystal quality in line with the distinct PL.« less

Film growth, adsorption and desorption kinetics of indigo on SiO2

PubMed Central

Scherwitzl, Boris; Resel, Roland; Winkler, Adolf

2015-01-01

Organic dyes have recently been discovered as promising semiconducting materials, attributable to the formation of hydrogen bonds. In this work, the adsorption and desorption behavior, as well as thin film growth was studied in detail for indigo molecules on silicon dioxide with different substrate treatments. The material was evaporated onto the substrate by means of physical vapor deposition under ultra-high vacuum conditions and was subsequently studied by Thermal Desorption Spectroscopy (TDS), Auger Electron Spectroscopy, X-Ray Diffraction, and Atomic Force Microscopy. TDS revealed initially adsorbed molecules to be strongly bonded on a sputter cleaned surface. After further deposition a formation of dimers is suggested, which de-stabilizes the bonding mechanism to the substrate and leads to a weakly bonded adsorbate. The dimers are highly mobile on the surface until they get incorporated into energetically favourable three-dimensional islands in a dewetting process. The stronger bonding of molecules within those islands could be shown by a higher desorption temperature. On a carbon contaminated surface no strongly bonded molecules appeared initially, weakly bonded monomers rather rearrange into islands at a surface coverage that is equivalent to one third of a monolayer of flat-lying molecules. The sticking coefficient was found to be unity on both substrates. The desorption energies from carbon covered silicon dioxide calculated to 1.67 ± 0.05 eV for multilayer desorption from the islands and 0.84 ± 0.05 eV for monolayer des orption. Corresponding values for desorption from a sputter cleaned surface are 1.53 ± 0.05 eV for multilayer and 0.83 ± 0.05 eV for monolayer desorption. PMID:24832297

Film growth, adsorption and desorption kinetics of indigo on SiO{sub 2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scherwitzl, Boris, E-mail: b.scherwitzl@tugraz.at; Resel, Roland; Winkler, Adolf

2014-05-14

Organic dyes have recently been discovered as promising semiconducting materials, attributable to the formation of hydrogen bonds. In this work, the adsorption and desorption behavior, as well as thin film growth was studied in detail for indigo molecules on silicon dioxide with different substrate treatments. The material was evaporated onto the substrate by means of physical vapor deposition under ultra-high vacuum conditions and was subsequently studied by Thermal Desorption Spectroscopy (TDS), Auger Electron Spectroscopy, X-Ray Diffraction, and Atomic Force Microscopy. TDS revealed initially adsorbed molecules to be strongly bonded on a sputter cleaned surface. After further deposition a formation ofmore » dimers is suggested, which de-stabilizes the bonding mechanism to the substrate and leads to a weakly bonded adsorbate. The dimers are highly mobile on the surface until they get incorporated into energetically favourable three-dimensional islands in a dewetting process. The stronger bonding of molecules within those islands could be shown by a higher desorption temperature. On a carbon contaminated surface no strongly bonded molecules appeared initially, weakly bonded monomers rather rearrange into islands at a surface coverage that is equivalent to one third of a monolayer of flat-lying molecules. The sticking coefficient was found to be unity on both substrates. The desorption energies from carbon covered silicon dioxide calculated to 1.67 ± 0.05 eV for multilayer desorption from the islands and 0.84 ± 0.05 eV for monolayer desorption. Corresponding values for desorption from a sputter cleaned surface are 1.53 ± 0.05 eV for multilayer and 0.83 ± 0.05 eV for monolayer desorption.« less

Film growth, adsorption and desorption kinetics of indigo on SiO2.

PubMed

Scherwitzl, Boris; Resel, Roland; Winkler, Adolf

2014-05-14

Organic dyes have recently been discovered as promising semiconducting materials, attributable to the formation of hydrogen bonds. In this work, the adsorption and desorption behavior, as well as thin film growth was studied in detail for indigo molecules on silicon dioxide with different substrate treatments. The material was evaporated onto the substrate by means of physical vapor deposition under ultra-high vacuum conditions and was subsequently studied by Thermal Desorption Spectroscopy (TDS), Auger Electron Spectroscopy, X-Ray Diffraction, and Atomic Force Microscopy. TDS revealed initially adsorbed molecules to be strongly bonded on a sputter cleaned surface. After further deposition a formation of dimers is suggested, which de-stabilizes the bonding mechanism to the substrate and leads to a weakly bonded adsorbate. The dimers are highly mobile on the surface until they get incorporated into energetically favourable three-dimensional islands in a dewetting process. The stronger bonding of molecules within those islands could be shown by a higher desorption temperature. On a carbon contaminated surface no strongly bonded molecules appeared initially, weakly bonded monomers rather rearrange into islands at a surface coverage that is equivalent to one third of a monolayer of flat-lying molecules. The sticking coefficient was found to be unity on both substrates. The desorption energies from carbon covered silicon dioxide calculated to 1.67 ± 0.05 eV for multilayer desorption from the islands and 0.84 ± 0.05 eV for monolayer desorption. Corresponding values for desorption from a sputter cleaned surface are 1.53 ± 0.05 eV for multilayer and 0.83 ± 0.05 eV for monolayer desorption.

Final Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hameed A. Naseem, Husam H. Abu-Safe

2007-02-09

The purpose of this project was to investigate metal-induced crystallization of amorphous silicon at low temperatures using excitation sources such as laser and rapid thermal annealing, as well as, electric field. Deposition of high quality crystalline silicon at low temperatures allows the use of low cost soda-lime glass and polymeric films for economically viable photovoltaic solar cells and low cost large area flat panel displays. In light of current and expected demands on Si supply due to expanding use of consumer electronic products throughout the world and the incessant demand for electric power the need for developing high grade Simore » thin films on low cost substrate becomes even more important. We used hydrogenated and un-hydrogenated amorphous silicon deposited by plasma enhanced chemical vapor deposition and sputtering techniques (both of which are extensively used in electronic and solar cell industries) to fabricate nano-crystalline, poly-crystalline (small as well as large grain), and single-crystalline (epitaxial) films at low temperatures. We demonstrated Si nanowires on flat surfaces that can be used for fabricating nanometer scale transistors. We also demonstrated lateral crystallization using Al with and without an applied electric field. These results are critical for high mobility thin film transistors (TFT) for large area display applications. Large grain silicon (~30-50 µm grain size for < 0.5 µm thick films) was demonstrated on glass substrates at low temperatures. We also demonstrated epitaxial growth of silicon on (100) Si substrates at temperatures as low as 450°C. Thin film Si solar cells are being projected as the material of choice for low cost high efficiency solar cells when properly coupled with excellent light-trapping schemes. Ar ion laser (CW) was shown to produce dendritic nanowire structures at low power whereas at higher powers yielded continuous polycrystalline films. The power density required for films in contact with Al was demonstrated to be at least two orders of magnitude lower that that reported in the literature before. Polysilicon was successfully achieved on polyimide (Kapton©) films. Thin film Si solar cells on lightweight stoable polymer offer great advantage for terrestrial and space power applications. In summary we have demonstrated through this research the viability of producing low cost nano-, poly-, and epitaxial Si material on substrates of choice for applications in economically viable environmentally friendly sustainable solar power systems. This truly enabling technology has widespread applications in multibillion dollar electronic industry and consumer products.« less

Evaluation of steam corrosion and water quenching behavior of zirconium-silicide coated LWR fuel claddings

NASA Astrophysics Data System (ADS)

Yeom, Hwasung; Lockhart, Cody; Mariani, Robert; Xu, Peng; Corradini, Michael; Sridharan, Kumar

2018-02-01

This study investigates steam corrosion of bulk ZrSi2, pure Si, and zirconium-silicide coatings as well as water quenching behavior of ZrSi2 coatings to evaluate its feasibility as a potential accident-tolerant fuel cladding coating material in light water nuclear reactor. The ZrSi2 coating and Zr2Si-ZrSi2 coating were deposited on Zircaloy-4 flats, SiC flats, and cylindrical Zircaloy-4 rodlets using magnetron sputter deposition. Bulk ZrSi2 and pure Si samples showed weight loss after the corrosion test in pure steam at 400 °C and 10.3 MPa for 72 h. Silicon depletion on the ZrSi2 surface during the steam test was related to the surface recession observed in the silicon samples. ZrSi2 coating (∼3.9 μm) pre-oxidized in 700 °C air prevented substrate oxidation but thin porous ZrO2 formed on the coating. The only condition which achieved complete silicon immobilization in the oxide scale in aqueous environments was the formation of ZrSiO4 via ZrSi2 coating oxidation in 1400 °C air. In addition, ZrSi2 coatings were beneficial in enhancing quenching heat transfer - the minimum film boiling temperature increased by 6-8% in the three different environmental conditions tested. During repeated thermal cycles (water quenching from 700 °C to 85 °C for 20 s) performed as a part of quench tests, no spallation and cracking was observed and the coating prevented oxidation of the underlying Zircaloy-4 substrate.

Absolute flatness measurements of silicon mirrors by a three-intersection method by near-infrared interferometry

PubMed Central

2013-01-01

Absolute flatness of three silicon plane mirrors have been measured by a three-intersection method based on the three-flat method using a near-infrared interferometer. The interferometer was constructed using a near-infrared laser diode with a 1,310-nm wavelength light where the silicon plane mirror is transparent. The height differences at the coordinate values between the absolute line profiles by the three-intersection method have been evaluated. The height differences of the three flats were 4.5 nm or less. The three-intersection method using the near-infrared interferometer was useful for measuring the absolute flatness of the silicon plane mirrors. PMID:23758916

Effect of substrate morphology slope distributions on light scattering, nc-Si:H film growth, and solar cell performance.

PubMed

Kim, Do Yun; Santbergen, Rudi; Jäger, Klaus; Sever, Martin; Krč, Janez; Topič, Marko; Hänni, Simon; Zhang, Chao; Heidt, Anna; Meier, Matthias; van Swaaij, René A C M M; Zeman, Miro

2014-12-24

Thin-film silicon solar cells are often deposited on textured ZnO substrates. The solar-cell performance is strongly correlated to the substrate morphology, as this morphology determines light scattering, defective-region formation, and crystalline growth of hydrogenated nanocrystalline silicon (nc-Si:H). Our objective is to gain deeper insight in these correlations using the slope distribution, rms roughness (σ(rms)) and correlation length (lc) of textured substrates. A wide range of surface morphologies was obtained by Ar plasma treatment and wet etching of textured and flat-as-deposited ZnO substrates. The σ(rms), lc and slope distribution were deduced from AFM scans. Especially, the slope distribution of substrates was represented in an efficient way that light scattering and film growth direction can be more directly estimated at the same time. We observed that besides a high σ(rms), a high slope angle is beneficial to obtain high haze and scattering of light at larger angles, resulting in higher short-circuit current density of nc-Si:H solar cells. However, a high slope angle can also promote the creation of defective regions in nc-Si:H films grown on the substrate. It is also found that the crystalline fraction of nc-Si:H solar cells has a stronger correlation with the slope distributions than with σ(rms) of substrates. In this study, we successfully correlate all these observations with the solar-cell performance by using the slope distribution of substrates.

Photochemical grafting of methyl groups on a Si(111) surface using a Grignard reagent.

PubMed

Herrera, Marvin Ustaris; Ichii, Takashi; Murase, Kuniaki; Sugimura, Hiroyuki

2013-12-01

The photochemical grafting of methyl groups onto an n-type Si(111) substrate was successfully achieved using a Grignard reagent. The preparation involved illuminating a hydrogen-terminated Si(111) that was immersed in a CH3MgBr-THF solution. The success was attributed to the ability of the n-type hydrogenated substrate to produce holes on its surface when illuminated. The rate of grafting methyl groups onto the silicon surface was higher when a larger illumination intensity or when a substrate with lower dopant concentration was used. In addition, the methylated layer has an atomically flat structure, has a hydrophobic surface, and has electron affinity that was lower than the bulk Si. Copyright © 2013 Elsevier Inc. All rights reserved.

Porous silicon-VO{sub 2} based hybrids as possible optical temperature sensor: Wavelength-dependent optical switching from visible to near-infrared range

DOE Office of Scientific and Technical Information (OSTI.GOV)

Antunez, E. E.; Salazar-Kuri, U.; Estevez, J. O.

Morphological properties of thermochromic VO{sub 2}—porous silicon based hybrids reveal the growth of well-crystalized nanometer-scale features of VO{sub 2} as compared with typical submicron granular structure obtained in thin films deposited on flat substrates. Structural characterization performed as a function of temperature via grazing incidence X-ray diffraction and micro-Raman demonstrate reversible semiconductor-metal transition of the hybrid, changing from a low-temperature monoclinic VO{sub 2}(M) to a high-temperature tetragonal rutile VO{sub 2}(R) crystalline structure, coupled with a decrease in phase transition temperature. Effective optical response studied in terms of red/blue shift of the reflectance spectra results in a wavelength-dependent optical switching withmore » temperature. As compared to VO{sub 2} film over crystalline silicon substrate, the hybrid structure is found to demonstrate up to 3-fold increase in the change of reflectivity with temperature, an enlarged hysteresis loop and a wider operational window for its potential application as an optical temperature sensor. Such silicon based hybrids represent an exciting class of functional materials to display thermally triggered optical switching culminated by the characteristics of each of the constituent blocks as well as device compatibility with standard integrated circuit technology.« less

Image quality and radiation dose on digital chest imaging: comparison of amorphous silicon and amorphous selenium flat-panel systems.

PubMed

Bacher, Klaus; Smeets, Peter; Vereecken, Ludo; De Hauwere, An; Duyck, Philippe; De Man, Robert; Verstraete, Koenraad; Thierens, Hubert

2006-09-01

The aim of this study was to compare the image quality and radiation dose in chest imaging using an amorphous silicon flat-panel detector system and an amorphous selenium flat-panel detector system. In addition, the low-contrast performance of both systems with standard and low radiation doses was compared. In two groups of 100 patients each, digital chest radiographs were acquired with either an amorphous silicon or an amorphous selenium flat-panel system. The effective dose of the examination was measured using thermoluminescent dosimeters placed in an anthropomorphic Rando phantom. The image quality of the digital chest radiographs was assessed by five experienced radiologists using the European Guidelines on Quality Criteria for Diagnostic Radiographic Images. In addition, a contrast-detail phantom study was set up to assess the low-contrast performance of both systems at different radiation dose levels. Differences between the two groups were tested for significance using the two-tailed Mann-Whitney test. The amorphous silicon flat-panel system allowed an important and significant reduction in effective dose in comparison with the amorphous selenium flat-panel system (p < 0.0001) for both the posteroanterior and lateral views. In addition, clinical image quality analysis showed that the dose reduction was not detrimental to image quality. Compared with the amorphous selenium flat-panel detector system, the amorphous silicon flat-panel detector system performed significantly better in the low-contrast phantom study, with phantom entrance dose values of up to 135 muGy. Chest radiographs can be acquired with a significantly lower patient radiation dose using an amorphous silicon flat-panel system than using an amorphous selenium flat-panel system, thereby producing images that are equal or even superior in quality to those of the amorphous selenium flat-panel detector system.

Enhancement of thermoelectric characteristics in AlGaN/GaN films deposited on inverted pyramidal Si surfaces

NASA Astrophysics Data System (ADS)

Yalamarthy, Ananth Saran; So, Hongyun; Senesky, Debbie G.

2017-07-01

In this letter, we demonstrate an engineering strategy to boost thermoelectric power factor via geometry-induced properties of the pyramid structure. Aluminum gallium nitride (AlGaN)/GaN heterostructured films grown on inverted pyramidal silicon (Si) demonstrate higher power factor as compared to those grown on conventional flat Si substrates. We found that the magnitude of the Seebeck coefficient at room temperature increased from approximately 297 μVK-1 for the flat film to approximately 849 μVK-1 for the film on inverted pyramidal Si. In addition, the "effective" electrical conductivity of the AlGaN/GaN on the inverted pyramidal structure increased compared to the flat structure, generating an enhancement of thermoelectric power factor. The results demonstrate how manipulation of geometry can be used to achieve better thermoelectric characteristics in a manner that could be scaled to a variety of different material platforms.

Junction-based field emission structure for field emission display

DOEpatents

Dinh, Long N.; Balooch, Mehdi; McLean, II, William; Schildbach, Marcus A.

2002-01-01

A junction-based field emission display, wherein the junctions are formed by depositing a semiconducting or dielectric, low work function, negative electron affinity (NEA) silicon-based compound film (SBCF) onto a metal or n-type semiconductor substrate. The SBCF can be doped to become a p-type semiconductor. A small forward bias voltage is applied across the junction so that electron transport is from the substrate into the SBCF region. Upon entering into this NEA region, many electrons are released into the vacuum level above the SBCF surface and accelerated toward a positively biased phosphor screen anode, hence lighting up the phosphor screen for display. To turn off, simply switch off the applied potential across the SBCF/substrate. May be used for field emission flat panel displays.

Study on Buckling of Stiff Thin Films on Soft Substrates as Functional Materials

NASA Astrophysics Data System (ADS)

Ma, Teng

In engineering, buckling is mechanical instability of walls or columns under compression and usually is a problem that engineers try to prevent. In everyday life buckles (wrinkles) on different substrates are ubiquitous -- from human skin to a rotten apple they are a commonly observed phenomenon. It seems that buckles with macroscopic wavelengths are not technologically useful; over the past decade or so, however, thanks to the widespread availability of soft polymers and silicone materials micro-buckles with wavelengths in submicron to micron scale have received increasing attention because it is useful for generating well-ordered periodic microstructures spontaneously without conventional lithographic techniques. This thesis investigates the buckling behavior of thin stiff films on soft polymeric substrates and explores a variety of applications, ranging from optical gratings, optical masks, energy harvest to energy storage. A laser scanning technique is proposed to detect micro-strain induced by thermomechanical loads and a periodic buckling microstructure is employed as a diffraction grating with broad wavelength tunability, which is spontaneously generated from a metallic thin film on polymer substrates. A mechanical strategy is also presented for quantitatively buckling nanoribbons of piezoelectric material on polymer substrates involving the combined use of lithographically patterning surface adhesion sites and transfer printing technique. The precisely engineered buckling configurations provide a route to energy harvesters with extremely high levels of stretchability. This stiff-thin-film/polymer hybrid structure is further employed into electrochemical field to circumvent the electrochemically-driven stress issue in silicon-anode-based lithium ion batteries. It shows that the initial flat silicon-nanoribbon-anode on a polymer substrate tends to buckle to mitigate the lithiation-induced stress so as to avoid the pulverization of silicon anode. Spontaneously generated submicron buckles of film/polymer are also used as an optical mask to produce submicron periodic patterns with large filling ratio in contrast to generating only ˜100 nm edge submicron patterns in conventional near-field soft contact photolithography. This thesis aims to deepen understanding of buckling behavior of thin films on compliant substrates and, in turn, to harness the fundamental properties of such instability for diverse applications.

Optimization of the silicon subcell for III-V on silicon multijunction solar cells: Key differences with conventional silicon technology

NASA Astrophysics Data System (ADS)

García-Tabarés, Elisa; Martín, Diego; García, Iván; Lelièvre, Jean François; Rey-Stolle, Ignacio

2012-10-01

Dual-junction solar cells formed by a GaAsP or GaInP top cell and a silicon (Si) bottom cell seem to be attractive candidates to materialize the long sought-for integration of III-V materials on Si for photovoltaic (PV) applications. Such integration would offer a cost breakthrough for PV technology, unifying the low cost of Si and the efficiency potential of III-V multijunction solar cells. The optimization of the Si solar cells properties in flat-plate PV technology is well-known; nevertheless, it has been proven that the behavior of Si substrates is different when processed in an MOVPE reactor In this study, we analyze several factors influencing the bottom subcell performance, namely, 1) the emitter formation as a result of phosphorus diffusion; 2) the passivation quality provided by the GaP nucleation layer; and 3) the process impact on the bottom subcell PV properties.

It's Harder to Splash on Soft Solids.

PubMed

Howland, Christopher J; Antkowiak, Arnaud; Castrejón-Pita, J Rafael; Howison, Sam D; Oliver, James M; Style, Robert W; Castrejón-Pita, Alfonso A

2016-10-28

Droplets splash when they impact dry, flat substrates above a critical velocity that depends on parameters such as droplet size, viscosity, and air pressure. By imaging ethanol drops impacting silicone gels of different stiffnesses, we show that substrate stiffness also affects the splashing threshold. Splashing is reduced or even eliminated: droplets on the softest substrates need over 70% more kinetic energy to splash than they do on rigid substrates. We show that this is due to energy losses caused by deformations of soft substrates during the first few microseconds of impact. We find that solids with Young's moduli ≲100  kPa reduce splashing, in agreement with simple scaling arguments. Thus, materials like soft gels and elastomers can be used as simple coatings for effective splash prevention. Soft substrates also serve as a useful system for testing splash-formation theories and sheet-ejection mechanisms, as they allow the characteristics of ejection sheets to be controlled independently of the bulk impact dynamics of droplets.

It's Harder to Splash on Soft Solids

NASA Astrophysics Data System (ADS)

Howland, Christopher J.; Antkowiak, Arnaud; Castrejón-Pita, J. Rafael; Howison, Sam D.; Oliver, James M.; Style, Robert W.; Castrejón-Pita, Alfonso A.

2016-10-01

Droplets splash when they impact dry, flat substrates above a critical velocity that depends on parameters such as droplet size, viscosity, and air pressure. By imaging ethanol drops impacting silicone gels of different stiffnesses, we show that substrate stiffness also affects the splashing threshold. Splashing is reduced or even eliminated: droplets on the softest substrates need over 70% more kinetic energy to splash than they do on rigid substrates. We show that this is due to energy losses caused by deformations of soft substrates during the first few microseconds of impact. We find that solids with Young's moduli ≲100 kPa reduce splashing, in agreement with simple scaling arguments. Thus, materials like soft gels and elastomers can be used as simple coatings for effective splash prevention. Soft substrates also serve as a useful system for testing splash-formation theories and sheet-ejection mechanisms, as they allow the characteristics of ejection sheets to be controlled independently of the bulk impact dynamics of droplets.

Low work function, stable thin films

DOEpatents

Dinh, Long N.; McLean, II, William; Balooch, Mehdi; Fehring, Jr., Edward J.; Schildbach, Marcus A.

2000-01-01

Generation of low work function, stable compound thin films by laser ablation. Compound thin films with low work function can be synthesized by simultaneously laser ablating silicon, for example, and thermal evaporating an alkali metal into an oxygen environment. For example, the compound thin film may be composed of Si/Cs/O. The work functions of the thin films can be varied by changing the silicon/alkali metal/oxygen ratio. Low work functions of the compound thin films deposited on silicon substrates were confirmed by ultraviolet photoelectron spectroscopy (UPS). The compound thin films are stable up to 500.degree. C. as measured by x-ray photoelectron spectroscopy (XPS). Tests have established that for certain chemical compositions and annealing temperatures of the compound thin films, negative electron affinity (NEA) was detected. The low work function, stable compound thin films can be utilized in solar cells, field emission flat panel displays, electron guns, and cold cathode electron guns.

The role of the substrate in Graphene/Silicon photodiodes

NASA Astrophysics Data System (ADS)

Luongo, G.; Giubileo, F.; Iemmo, L.; Di Bartolomeo, A.

2018-01-01

The Graphene/Silicon (Gr/Si) junction can function as a Schottky diode with performances strictly related to the quality of the interface. Here, we focus on the substrate geometry and on its effects on Gr/Si junction physics. We fabricate and study the electrical and optical behaviour of two types of devices: one made of a Gr/Si planar junction, the second realized with graphene on an array of Si nanotips. We show that the Gr/Si flat device exhibits a reverse photocurrent higher than the forward current and achieves a photoresponsivity of 2.5 A/W. The high photoresponse is due to the charges photogenerated in Si below a parasitic graphene/SiO2/Si structure, which are injected into the Gr/Si junction region. The other device with graphene on Si-tips displays a reverse current that grows exponentially with the bias. We explain this behaviour by taking into account the tip geometry of the substrate, which magnifies the electric field and shifts the Fermi level of graphene, thus enabling fine-tuning of the Schottky barrier height. The Gr/Si-tip device achieves a higher photoresponsivity, up to 3 A/W, likely due to photocharge internal multiplication.

Silica substrate or portion formed from oxidation of monocrystalline silicon

DOEpatents

Matzke, Carolyn M.; Rieger, Dennis J.; Ellis, Robert V.

2003-07-15

A method is disclosed for forming an inclusion-free silica substrate using a monocrystalline silicon substrate as the starting material and oxidizing the silicon substrate to convert it entirely to silica. The oxidation process is performed from both major surfaces of the silicon substrate using a conventional high-pressure oxidation system. The resulting product is an amorphous silica substrate which is expected to have superior etching characteristics for microfabrication than conventional fused silica substrates. The present invention can also be used to convert only a portion of a monocrystalline silicon substrate to silica by masking the silicon substrate and locally thinning a portion the silicon substrate prior to converting the silicon portion entirely to silica. In this case, the silica formed by oxidizing the thinned portion of the silicon substrate can be used, for example, as a window to provide optical access through the silicon substrate.

Amorphous silicon thin film transistor active-matrix organic light-emitting diode displays fabricated on flexible substrates

NASA Astrophysics Data System (ADS)

Nichols, Jonathan A.

Organic light-emitting diode (OLED) displays are of immense interest because they have several advantages over liquid crystal displays, the current dominant flat panel display technology. OLED displays are emissive and therefore are brighter, have a larger viewing angle, and do not require backlights and filters, allowing thinner, lighter, and more power efficient displays. The goal of this work was to advance the state-of-the-art in active-matrix OLED display technology. First, hydrogenated amorphous silicon (a-Si:H) thin film transistor (TFT) active-matrix OLED pixels and arrays were designed and fabricated on glass substrates. The devices operated at low voltages and demonstrated that lower performance TFTs could be utilized in active-matrix OLED displays, possibly allowing lower cost processing and the use of polymeric substrates. Attempts at designing more control into the display at the pixel level were also made. Bistable (one bit gray scale) active-matrix OLED pixels and arrays were designed and fabricated. Such pixels could be used in novel applications and eventually help reduce the bandwidth requirements in high-resolution and large-area displays. Finally, a-Si:H TFT active-matrix OLED pixels and arrays were fabricated on a polymeric substrate. Displays fabricated on a polymeric substrates would be lightweight; flexible, more rugged, and potentially less expensive to fabricate. Many of the difficulties associated with fabricating active-matrix backplanes on flexible substrates were studied and addressed.

SCIL nanoimprint solutions: high-volume soft NIL for wafer scale sub-10nm resolution

NASA Astrophysics Data System (ADS)

Voorkamp, R.; Verschuuren, M. A.; van Brakel, R.

2016-10-01

Nano-patterning materials and surfaces can add unique functionalities and properties which cannot be obtained in bulk or micro-structured materials. Examples range from hetro-epitaxy of semiconductor nano-wires to guiding cell expression and growth on medical implants. [1] Due to the cost and throughput requirements conventional nano-patterning techniques such as deep UV lithography (cost and flat substrate demands) and electron-beam lithography (cost, throughput) are not an option. Self-assembly techniques are being considered for IC manufacturing, but require nano-sized guiding patterns, which have to be fabricated in any case.[2] Additionally, the self-assembly process is highly sensitive to the environment and layer thickness, which is difficult to control on non-flat surfaces such as PV silicon wafers or III/V substrates. Laser interference lithography can achieve wafer scale periodic patterns, but is limited by the throughput due to intensity of the laser at the pinhole and only regular patterns are possible where the pattern fill fraction cannot be chosen freely due to the interference condition.[3] Nanoimprint lithography (NIL) is a promising technology for the cost effective fabrication of sub-micron and nano-patterns on large areas. The challenges for NIL are related to the technique being a contact method where a stamp which holds the patterns is required to be brought into intimate contact with the surface of the product. In NIL a strong distinction is made between the type of stamp used, either rigid or soft. Rigid stamps are made from patterned silicon, silica or plastic foils and are capable of sub-10nm resolution and wafer scale patterning. All these materials behave similar at the micro- to nm scale and require high pressures (5 - 50 Bar) to enable conformal contact to be made on wafer scales. Real world conditions such as substrate bow and particle contaminants complicate the use of rigid stamps for wafer scale areas, reducing stamp lifetime and yield. Soft stamps, usually based on silicone rubber, behave fundamentally different compared to rigid stamps on the macro-, micro- and nanometer level. The main limitation of traditional silicones is that they are too soft to support sub-micron features against surface tension based stamp deformation and collapse [4] and handling a soft stamp to achieve accurate feature placement on wafer scales to allow overlay alignment with sub-100nm overlay accuracy.

Graphene synthesized on porous silicon for active electrode material of supercapacitors

NASA Astrophysics Data System (ADS)

Su, B. B.; Chen, X. Y.; Halvorsen, E.

2016-11-01

We present graphene synthesized by chemical vapour deposition under atmospheric pressure on both porous nanostructures and flat wafers as electrode scaffolds for supercapacitors. A 3nm thin gold layer was deposited on samples of both porous and flat silicon for exploring the catalytic influence during graphene synthesis. Micro-four-point probe resistivity measurements revealed that the resistivity of porous silicon samples was nearly 53 times smaller than of the flat silicon ones when all the samples were covered by a thin gold layer after the graphene growth. From cyclic voltammetry, the average specific capacitance of porous silicon coated with gold was estimated to 267 μF/cm2 while that without catalyst layer was 145μF/cm2. We demonstrated that porous silicon based on nanorods can play an important role in graphene synthesis and enable silicon as promising electrodes for supercapacitors.

Nanopattern-guided growth of single-crystal silicon on amorphous substrates and high-performance sub-100 nm thin-film transistors for three-dimensional integrated circuits

NASA Astrophysics Data System (ADS)

Gu, Jian

This thesis explores how nanopatterns can be used to control the growth of single-crystal silicon on amorphous substrates at low temperature, with potential applications on flat panel liquid-crystal display and 3-dimensional (3D) integrated circuits. I first present excimer laser annealing of amorphous silicon (a-Si) nanostructures on thermally oxidized silicon wafer for controlled formation of single-crystal silicon islands. Preferential nucleation at pattern center is observed due to substrate enhanced edge heating. Single-grain silicon is obtained in a 50 nm x 100 nm rectangular pattern by super lateral growth (SLG). Narrow lines (such as 20-nm-wide) can serve as artificial heterogeneous nucleation sites during crystallization of large patterns, which could lead to the formation of single-crystal silicon islands in a controlled fashion. In addition to eximer laser annealing, NanoPAtterning and nickel-induced lateral C&barbelow;rystallization (NanoPAC) of a-Si lines is presented. Single-crystal silicon is achieved by NanoPAC. The line width of a-Si affects the grain structure of crystallized silicon lines significantly. Statistics show that single-crystal silicon is formed for all lines with width between 50 nm to 200 nm. Using in situ transmission electron microscopy (TEM), nickel-induced lateral crystallization (Ni-ILC) of a-Si inside a pattern is revealed; lithography-constrained single seeding (LISS) is proposed to explain the single-crystal formation. Intragrain line and two-dimensional defects are also studied. To test the electrical properties of NanoPAC silicon films, sub-100 nm thin-film transistors (TFTs) are fabricated using Patten-controlled crystallization of Ṯhin a-Si channel layer and H&barbelow;igh temperature (850°C) annealing, coined PaTH process. PaTH TFTs show excellent device performance over traditional solid phase crystallized (SPC) TFTs in terms of threshold voltage, threshold voltage roll-off, leakage current, subthreshold swing, on/off current ratio, device-to-device uniformity etc. Two-dimensional device simulations show that PaTH TFTs are comparable to silicon-on-insulator (SOI) devices, making it a promising candidate for the fabrication of future high performance, low-power 3D integrated circuits. Finally, an ultrafast nanolithography technique, laser-assisted direct imprint (LADI) is introduced. LADI shows the ability of patterning nanostructures directly in silicon in nanoseconds with sub-10 nm resolution. The process has potential applications in multiple disciplines, and could be extended to other materials and processes.

Graphene oxide-Ag nanoparticles-pyramidal silicon hybrid system for homogeneous, long-term stable and sensitive SERS activity

NASA Astrophysics Data System (ADS)

Guo, Jia; Xu, Shicai; Liu, Xiaoyun; Li, Zhe; Hu, Litao; Li, Zhen; Chen, Peixi; Ma, Yong; Jiang, Shouzhen; Ning, Tingyin

2017-02-01

In our work, few layers graphene oxide (GO) were directly synthesized on Ag nanoparticles (AgNPs) by spin-coating method to fabricate a GO-AgNPs hybrid structure on a pyramidal silicon (PSi) substrate for surface-enhanced Raman scattering (SERS). The GO-AgNPs-PSi substrate showed excellent Raman enhancement effect, the minimum detected concentration for Rhodamine 6G (R6G) can reach 10-12 M, which is one order of magnitude lower than the AgNPs-PSi substrate and two order of magnitude lower than the GO-AgNPs-flat-Si substrate. The linear fit calibration curve with error bars is presented and the value of R2 of 612 and 773 cm-1 can reach 0.986 and 0.980, respectively. The excellent linear response between the Raman intensity and R6G concentrations prove that the prepared GO-AgNPs-PSi substrates can serve as good SERS substrate for molecule detection. The maximum deviations of SERS intensities from 20 positions of the GO-AgNPs-PSi substrate are less than 8%, revealing the high homogeneity of the SERS substrate. The excellent homogeneity of the enhanced Raman signals can be attributed to well-separated pyramid arrays of PSi, the uniform morphology of AgNPs and multi-functions of GO layer. Besides, the uniform GO film can effectively protect AgNPs from oxidation and endow the hybrid system a good stability and long lifetime. This GO-AgNPs-PSi substrate may provide a new way toward practical applications for the ultrasensitive and label-free SERS detection in areas of medicine, food safety and biotechnology.

Pristine Stratospheric Collections of Cosmic Dust

NASA Technical Reports Server (NTRS)

Messenger, S.; Keller, L. P.; Nakamura-Messenger, K.; Clemett, S. J.

2012-01-01

Since 1981, NASA has routinely collected interplanetary dust particles (IDPs) in the stratosphere by inertial impact onto silicone oil-coated flat plate collectors deployed on the wings of high-altitude aircraft [1]. The highly viscous oil traps and localizes the particles, which can fragment during collection. Particles are removed from the collectors with a micromanipulator and washed of the oil using organic solvents, typically hexane or xylene. While silicone oil is an efficient collection medium, its use is problematic. All IDPs are initially coated with this material (polydimethylsiloxane, n(CH3)2SiO) and traces of oil may remain after cleaning. The solvent rinse itself is also a concern as it likely removes indigenous organics from the particles. To avoid these issues, we used a polyurethane foam substrate for the oil-free stratospheric collection of IDPs.

Single-layer-coated surfaces with linearized reflectance versus angle of incidence: application to passive and active silicon rotation sensors

NASA Astrophysics Data System (ADS)

Azzam, R. M. A.; Howlader, M. M. K.; Georgiou, T. Y.

1995-08-01

A transparent or absorbing substrate can be coated with a transparent thin film to produce a linear reflectance-versus-angle-of-incidence response over a certain range of angles. Linearization at and near normal incidence is a special case that leads to a maximally flat response for p -polarized, s -polarized, or unpolarized light. For midrange and high-range linearization with moderate and high slopes, respectively, the best results are obtained when the incident light is s polarized. Application to a Si substrate that is coated with a SiO2 film leads to novel passive and active reflection rotation sensors. Experimental results and an error analysis of this rotation sensor are presented.

The influence of Atomic Oxygen on the Figure of Merit of Indium Tin Oxide thin Films grown by reactive Dual Ion Beam Sputtering

NASA Astrophysics Data System (ADS)

Geerts, Wilhelmus; Simpson, Nelson; Woodall, Allen; Compton, Maclyn

2014-03-01

Indium Tin Oxide (ITO) is a transparent conducting oxide that is used in flat panel displays and optoelectronics. Highly conductive and transparent ITO films are normally produced by heating the substrate to 300 Celsius during deposition excluding plastics to be used as a substrate material. We investigated whether high quality ITO films can be sputtered at room temperature using atomic instead of molecular oxygen. The films were deposited by dual ion beam sputtering (DIBS). During deposition the substrate was exposed to a molecular or an atomic oxygen flux. Microscope glass slides and silicon wafers were used as substrates. A 29 nm thick SIO2 buffer layer was used. Optical properties were measured with a M2000 Woollam variable angle spectroscopic ellipsometer. Electrical properties were measured by linear four point probe using a Jandel 4pp setup employing silicon carbide electrodes, high input resistance, and Keithley low bias current buffer amplifiers. The figure of merit (FOM), i.e. the ratio of the conductivity and the average optical absorption coefficient (400-800 nm), was calculated from the optical and electric properties and appeared to be 1.2 to 5 times higher for the samples sputtered with atomic oxygen. The largest value obtained for the FOM was 0.08 reciprocal Ohms. The authors would like to thank the Research Corporation for Financial Support.

It's harder to splash on soft solids

NASA Astrophysics Data System (ADS)

Howison, Sam; Howland, Christopher; Antkowiak, Arnaud; Castrejon-Pita, Rafael; Oliver, James; Style, Robert; Castrejon-Pita, Alfonso

2016-11-01

Droplets splash when they impact dry, flat substrates above a critical velocity that depends on parameters such as droplet size, viscosity and air pressure. By imaging ethanol drops impacting silicone gels of different stiffnesses we show that substrate stiffness also affects the splashing thresh- old. Splashing is reduced or even eliminated: droplets on the softest substrates need over 70% more kinetic energy to splash than they do on rigid substrates. We show that this is due to energy losses caused by deformations of soft substrates during the first few microseconds of impact. We find that solids with Young's moduli < 100kPa reduce splashing, in agreement with simple scaling arguments. Thus materials like soft gels and elastomers can be used as simple coatings for effective splash prevention. Soft substrates also serve as a useful system for testing splash-formation theories and sheet-ejection mechanisms, as they allow the characteristics of ejection sheets to be controlled independently of the bulk impact dynamics of droplets. EPSRC (CJH), John Fell Oxford University Press (OUP) Research Fund (AACP and RWS), The Royal Society (AAC-P).

Design and fabrication of non silicon substrate based MEMS energy harvester for arbitrary surface applications

NASA Astrophysics Data System (ADS)

Balpande, Suresh S.; Pande, Rajesh S.

2016-04-01

Internet of Things (IoT) uses MEMS sensor nodes and actuators to sense and control objects through Internet. IOT deploys millions of chemical battery driven sensors at different locations which are not reliable many times because of frequent requirement of charging & battery replacement in case of underground laying, placement at harsh environmental conditions, huge count and difference between demand (24 % per year) and availability (energy density growing rate 8% per year). Energy harvester fabricated on silicon wafers have been widely used in manufacturing MEMS structures. These devices require complex fabrication processes, costly chemicals & clean room. In addition to this silicon wafer based devices are not suitable for curved surfaces like pipes, human bodies, organisms, or other arbitrary surface like clothes, structure surfaces which does not have flat and smooth surface always. Therefore, devices based on rigid silicon wafers are not suitable for these applications. Flexible structures are the key solution for this problems. Energy transduction mechanism generates power from free surrounding vibrations or impact. Sensor nodes application has been purposefully selected due to discrete power requirement at low duty cycle. Such nodes require an average power budget in the range of about 0.1 microwatt to 1 mW over a period of 3-5 seconds. Energy harvester is the best alternate source in contrast with battery for sensor node application. Novel design of Energy Harvester based on cheapest flexible non silicon substrate i.e. cellulose acetate substrate have been modeled, simulated and analyzed on COMSOL multiphysics and fabricated using sol-gel spin coating setup. Single cantilever based harvester generates 60-75 mV peak electric potential at 22Hz frequency and approximately 22 µW power at 1K-Ohm load. Cantilever array can be employed for generating higher voltage by replicating this structure. This work covers design, optimization, fabrication of harvester and schottky diodes based voltage multiplier.

Design and fabrication of non silicon substrate based MEMS energy harvester for arbitrary surface applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balpande, Suresh S., E-mail: balpandes@rknec.edu; Pande, Rajesh S.

Internet of Things (IoT) uses MEMS sensor nodes and actuators to sense and control objects through Internet. IOT deploys millions of chemical battery driven sensors at different locations which are not reliable many times because of frequent requirement of charging & battery replacement in case of underground laying, placement at harsh environmental conditions, huge count and difference between demand (24 % per year) and availability (energy density growing rate 8% per year). Energy harvester fabricated on silicon wafers have been widely used in manufacturing MEMS structures. These devices require complex fabrication processes, costly chemicals & clean room. In addition tomore » this silicon wafer based devices are not suitable for curved surfaces like pipes, human bodies, organisms, or other arbitrary surface like clothes, structure surfaces which does not have flat and smooth surface always. Therefore, devices based on rigid silicon wafers are not suitable for these applications. Flexible structures are the key solution for this problems. Energy transduction mechanism generates power from free surrounding vibrations or impact. Sensor nodes application has been purposefully selected due to discrete power requirement at low duty cycle. Such nodes require an average power budget in the range of about 0.1 microwatt to 1 mW over a period of 3-5 seconds. Energy harvester is the best alternate source in contrast with battery for sensor node application. Novel design of Energy Harvester based on cheapest flexible non silicon substrate i.e. cellulose acetate substrate have been modeled, simulated and analyzed on COMSOL multiphysics and fabricated using sol-gel spin coating setup. Single cantilever based harvester generates 60-75 mV peak electric potential at 22Hz frequency and approximately 22 µW power at 1K-Ohm load. Cantilever array can be employed for generating higher voltage by replicating this structure. This work covers design, optimization, fabrication of harvester and schottky diodes based voltage multiplier.« less

Droplets move over viscoelastic substrates by surfing a ridge

PubMed Central

Karpitschka, S.; Das, S.; van Gorcum, M.; Perrin, H.; Andreotti, B.; Snoeijer, J. H.

2015-01-01

Liquid drops on soft solids generate strong deformations below the contact line, resulting from a balance of capillary and elastic forces. The movement of these drops may cause strong, potentially singular dissipation in the soft solid. Here we show that a drop on a soft substrate moves by surfing a ridge: the initially flat solid surface is deformed into a sharp ridge whose orientation angle depends on the contact line velocity. We measure this angle for water on a silicone gel and develop a theory based on the substrate rheology. We quantitatively recover the dynamic contact angle and provide a mechanism for stick–slip motion when a drop is forced strongly: the contact line depins and slides down the wetting ridge, forming a new one after a transient. We anticipate that our theory will have implications in problems such as self-organization of cell tissues or the design of capillarity-based microrheometers. PMID:26238436

Optical enhancing durable anti-reflective coating

DOEpatents

Maghsoodi, Sina; Varadarajan, Aravamuthan; Movassat, Meisam

2016-07-05

Disclosed herein are polysilsesquioxane based anti-reflective coating (ARC) compositions, methods of preparation, and methods of deposition on a substrate. In embodiments, the polysilsesquioxane of this disclosure is prepared in a two-step process of acid catalyzed hydrolysis of organoalkoxysilane followed by addition of tetralkoxysilane that generates silicone polymers with >40 mol % silanol based on Si-NMR. These high silanol siloxane polymers are stable and have a long shelf-life in the polar organic solvents at room temperature. Also disclosed are low refractive index ARC made from these compositions with and without additives such as porogens, templates, Si--OH condensation catalyst and/or nanofillers. Also disclosed are methods and apparatus for applying coatings to flat substrates including substrate pre-treatment processes, coating processes including flow coating and roll coating, and coating curing processes including skin-curing using hot-air knives. Also disclosed are coating compositions and formulations for highly tunable, durable, highly abrasion-resistant functionalized anti-reflective coatings.

High gain durable anti-reflective coating

DOEpatents

Maghsoodi, Sina; Brophy, Brenor L.; Colson, Thomas E.; Gonsalves, Peter R.; Abrams, Ze'ev R.

2016-07-26

Disclosed herein are polysilsesquioxane-based anti-reflective coating (ARC) compositions, methods of preparation, and methods of deposition on a substrate. In one embodiment, the polysilsesquioxane of this disclosure is prepared in a two-step process of acid catalyzed hydrolysis of organoalkoxysilane followed by addition of tetralkoxysilane that generates silicone polymers with >40 mol % silanol based on Si-NMR. These high silanol siloxane polymers are stable and have a long shelf-life in polar organic solvents at room temperature. Also disclosed are low refractive index ARC made from these compositions with and without additives such as porogens, templates, thermal radical initiator, photo radical initiators, crosslinkers, Si--OH condensation catalyst and nano-fillers. Also disclosed are methods and apparatus for applying coatings to flat substrates including substrate pre-treatment processes, coating processes and coating curing processes including skin-curing using hot-air knives. Also disclosed are coating compositions and formulations for highly tunable, durable, highly abrasion-resistant functionalized anti-reflective coatings.

Tilt Grain Boundary Topology Induced by Substrate Topography.

PubMed

Yu, Henry; Gupta, Nitant; Hu, Zhili; Wang, Kai; Srijanto, Bernadeta R; Xiao, Kai; Geohegan, David B; Yakobson, Boris I

2017-09-26

Synthesis of two-dimensional (2D) crystals is a topic of great current interest, since their chemical makeup, electronic, mechanical, catalytic, and optical properties are so diverse. A universal challenge, however, is the generally random formation of defects caused by various growth factors on flat surfaces. Here we show through theoretical analysis and experimental demonstration that nonplanar, curved-topography substrates permit the intentional and controllable creation of topological defects within 2D materials. We augment a common phase-field method by adding a geometric phase to track the crystal misorientation on a curved surface and to detect the formation of grain boundaries, especially when a growing monocrystal "catches its own tail" on a nontrivial topographical feature. It is specifically illustrated by simulated growth of a trigonal symmetry crystal on a conical-planar substrate, to match the experimental synthesis of WS 2 on silicon template, with satisfactory and in some cases remarkable agreement of theory predictions and experimental evidence.

Shin-Etsu super-high-flat substrate for FPD panel photomask

NASA Astrophysics Data System (ADS)

Ishitsuka, Youkou; Harada, Daijitsu; Watabe, Atsushi; Takeuchi, Masaki

2017-07-01

Recently, high-resolution exposure machine has been developed for production of high-definition (HD) panels, and higher-flat photomask substrates for FPD is being expected for panel makers to produce HD panels. In this presentation, we introduce about Shin-Etsu's advanced technique of producing super-high-flat photomask substrates. Shin-Etsu has developed surface polishing and planarization technology with No.1-quality-IC photomask substrates. Our most advanced IC photomask substrates have gained the highest estimation and appreciation from our customers because of their surface quality (non-defect surface without sub-0.1um size defects) and ultimate flatness (sub-0.1um order having achieved). By scaling up those IC photomask substrate technologies and developing unique large-size processing technologies, we have achieved creating high-flat large substrates, even G10-photomask size as well as regular G6-G8 photomask size. The core technology is that the surface shape of the substrate is completely controlled by the unique method. For example, we can regularly produce a substrate with its flatness of triple 5ums; front side flatness, back side flatness and total thickness variation are all less than 5μm. Furthermore, we are able to supply a substrate with its flatness of triple 3ums for G6-photomask size advanced grade, believed to be needed in near future.

Generation of low work function, stable compound thin films by laser ablation

DOEpatents

Dinh, Long N.; McLean, II, William; Balooch, Mehdi; Fehring, Jr., Edward J.; Schildbach, Marcus A.

2001-01-01

Generation of low work function, stable compound thin films by laser ablation. Compound thin films with low work function can be synthesized by simultaneously laser ablating silicon, for example, and thermal evaporating an alkali metal into an oxygen environment. For example, the compound thin film may be composed of Si/Cs/O. The work functions of the thin films can be varied by changing the silicon/alkali metal/oxygen ratio. Low work functions of the compound thin films deposited on silicon substrates were confirmed by ultraviolet photoelectron spectroscopy (UPS). The compound thin films are stable up to 500.degree. C. as measured by x-ray photoelectron spectroscopy (XPS). Tests have established that for certain chemical compositions and annealing temperatures of the compound thin films, negative electron affinity (NEA) was detected. The low work function, stable compound thin films can be utilized in solar cells, field emission flat panel displays, electron guns, and cold cathode electron guns.

Method of forming crystalline silicon devices on glass

DOEpatents

McCarthy, Anthony M.

1995-01-01

A method for fabricating single-crystal silicon microelectronic components on a silicon substrate and transferring same to a glass substrate. This is achieved by utilizing conventional silicon processing techniques for fabricating components of electronic circuits and devices on bulk silicon, wherein a bulk silicon surface is prepared with epitaxial layers prior to the conventional processing. The silicon substrate is bonded to a glass substrate and the bulk silicon is removed leaving the components intact on the glass substrate surface. Subsequent standard processing completes the device and circuit manufacturing. This invention is useful in applications requiring a transparent or insulating substrate, particularly for display manufacturing. Other applications include sensors, actuators, optoelectronics, radiation hard electronics, and high temperature electronics.

Neurite guidance and three-dimensional confinement via compliant semiconductor scaffolds.

PubMed

Cavallo, Francesca; Huang, Yu; Dent, Erik W; Williams, Justin C; Lagally, Max G

2014-12-23

Neurons are often cultured in vitro on a flat, open, and rigid substrate, a platform that does not reflect well the native microenvironment of the brain. To address this concern, we have developed a culturing platform containing arrays of microchannels, formed in a crystalline-silicon nanomembrane (NM) resting on polydimethylsiloxane; this platform will additionally enable active sensing and stimulation at the local scale, via devices fabricated in the silicon. The mechanical properties of the composite Si/compliant substrate nanomaterial approximate those of neural tissue. The microchannels, created in the NM by strain engineering, demonstrate strong guidance of neurite outgrowth. Using plasma techniques, we developed a means to coat just the inside surface of these channels with an adhesion promoter (poly-d-lysine). For NM channels with openings larger than the cross-sectional area of a single axon, strong physical confinement and guidance of axons through the channels are observed. Imaging of axons that grow in channels with openings that approximate the size of an axon suggests that a tight seal exists between the cell membrane and the inner surface of the channel, mimicking a myelin sheath. Such a tight seal of the cell membrane with the channel surface would make this platform an attractive candidate for future neuronal repair. Results of measurements of impedance and photoluminescence of bare NM channels are comparable to those on a flat NM, demonstrating electrical and optical modalities of our platform and suggesting that this scaffold can be expanded for active sensing and monitoring of neuron cellular processes in conditions in which they exist naturally.

Commercial silicon-on-insulator (SOI) wafers as a versatile substrate for laser desorption/ionization mass spectrometry.

PubMed

Kim, Shin Hye; Kim, Jeongkwon; Moon, Dae Won; Han, Sang Yun

2013-01-01

We report here that a commercial silicon-on-insulator (SOI) wafer offers an opportunity for laser desorption/ionization (LDI) of peptide molecules, which occurs directly from its flat surface without requiring special surface preparation. The LDI-on-SOI exhibits intact ionization of peptides with a good detection limit of lower than 20 fmol, of which the mass range is demonstrated up to insulin with citric acid additives. The LDI process most likely arises from laser-induced surface heating promoted by two-dimensional thermal confinement in the thin Si surface layer of the SOI wafer. As a consequence of the thermal process, the LDI-on-SOI method is also capable of creating post-source decay (PSD) of the resulting peptide LDI ions, which is suitable for peptide sequencing using conventional TOF/TOF mass spectrometry.

Method of forming crystalline silicon devices on glass

DOEpatents

McCarthy, A.M.

1995-03-21

A method is disclosed for fabricating single-crystal silicon microelectronic components on a silicon substrate and transferring same to a glass substrate. This is achieved by utilizing conventional silicon processing techniques for fabricating components of electronic circuits and devices on bulk silicon, wherein a bulk silicon surface is prepared with epitaxial layers prior to the conventional processing. The silicon substrate is bonded to a glass substrate and the bulk silicon is removed leaving the components intact on the glass substrate surface. Subsequent standard processing completes the device and circuit manufacturing. This invention is useful in applications requiring a transparent or insulating substrate, particularly for display manufacturing. Other applications include sensors, actuators, optoelectronics, radiation hard electronics, and high temperature electronics. 7 figures.

Metallic coatings on silicon substrates, and methods of forming metallic coatings on silicon substrates

DOEpatents

Branagan, Daniel J [Idaho Falls, ID; Hyde, Timothy A [Idaho Falls, ID; Fincke, James R [Los Alamos, NM

2008-03-11

The invention includes methods of forming a metallic coating on a substrate which contains silicon. A metallic glass layer is formed over a silicon surface of the substrate. The invention includes methods of protecting a silicon substrate. The substrate is provided within a deposition chamber along with a deposition target. Material from the deposition target is deposited over at least a portion of the silicon substrate to form a protective layer or structure which contains metallic glass. The metallic glass comprises iron and one or more of B, Si, P and C. The invention includes structures which have a substrate containing silicon and a metallic layer over the substrate. The metallic layer contains less than or equal to about 2 weight % carbon and has a hardness of at least 9.2 GPa. The metallic layer can have an amorphous microstructure or can be devitrified to have a nanocrystalline microstructure.

Method for fabricating an ultra-low expansion mask blank having a crystalline silicon layer

DOEpatents

Cardinale, Gregory F.

2002-01-01

A method for fabricating masks for extreme ultraviolet lithography (EUVL) using Ultra-Low Expansion (ULE) substrates and crystalline silicon. ULE substrates are required for the necessary thermal management in EUVL mask blanks, and defect detection and classification have been obtained using crystalline silicon substrate materials. Thus, this method provides the advantages for both the ULE substrate and the crystalline silicon in an Extreme Ultra-Violet (EUV) mask blank. The method is carried out by bonding a crystalline silicon wafer or member to a ULE wafer or substrate and thinning the silicon to produce a 5-10 .mu.m thick crystalline silicon layer on the surface of the ULE substrate. The thinning of the crystalline silicon may be carried out, for example, by chemical mechanical polishing and if necessary or desired, oxidizing the silicon followed by etching to the desired thickness of the silicon.

Fully methylated, atomically flat (111) silicon surface

NASA Astrophysics Data System (ADS)

Fidélis, A.; Ozanam, F.; Chazalviel, J.-N.

2000-01-01

The atomically flat hydrogenated (111) silicon surface has been methylated by anodization in a Grignard reagent and the surface obtained characterized by infrared spectroscopy. 100% substitution of the hydrogen atoms by methyl groups is observed. The resulting surface exhibits preserved ordering and superior chemical stability.

The Imaging Properties of a Silicon Wafer X-Ray Telescope

NASA Technical Reports Server (NTRS)

Joy, M. K.; Kolodziejczak, J. J.; Weisskopf, M. C.; Fair, S.; Ramsey, B. D.

1994-01-01

Silicon wafers have excellent optical properties --- low microroughness and good medium-scale flatness --- which Make them suitable candidates for inexpensive flat-plate grazing-incidence x-ray mirrors. On short spatial scales (less than 3 mm) the surface quality of silicon wafers rivals that expected of the Advanced X-Ray Astrophysics Facility (AXAF) high-resolution optics. On larger spatial scales, however, performance may be degraded by the departure from flatness of the wafer and by distortions induced by the mounting scheme. In order to investigate such effects, we designed and constructed a prototype silicon-wafer x-ray telescope. The device was then tested in both visible light and x rays. The telescope module consists of 94 150-mm-diameter wafers, densely packed into the first stage of a Kirkpatrick-Baez configuration. X-ray tests at three energies (4.5, 6.4, and 8.0 keV) showed an energy-independent line spread function with full width at half maximum (FWHM) of 150 arcseconds, dominated by deviations from large-scale flatness.

Flexible Sensors for Pressure Therapy: Effect of Substrate Curvature and Stiffness on Sensor Performance.

PubMed

Khodasevych, Iryna; Parmar, Suresh; Troynikov, Olga

2017-10-20

Flexible pressure sensors are increasingly being used in medical and non-medical applications, and particularly in innovative health monitoring. Their efficacy in medical applications such as compression therapy depends on the accuracy and repeatability of their output, which in turn depend on factors such as sensor type, shape, pressure range, and conformability of the sensor to the body surface. Numerous researchers have examined the effects of sensor type and shape, but little information is available on the effect of human body parameters such as support surfaces' curvature and the stiffness of soft tissues on pressure sensing performance. We investigated the effects of body parameters on the performance of pressure sensors using a custom-made human-leg-like test setup. Pressure sensing parameters such as accuracy, drift and repeatability were determined in both static (eight hours continuous pressure) and dynamic (10 cycles of pressure application of 30 s duration) testing conditions. The testing was performed with a focus on compression therapy application for venous leg ulcer treatments, and was conducted in a low-pressure range of 20-70 mmHg. Commercially available sensors manufactured by Peratech and Sensitronics were used under various loading conditions to determine the influence of stiffness and curvature. Flat rigid, flat soft silicone and three cylindrical silicone surfaces of radii of curvature of 3.5 cm, 5.5 cm and 6.5 cm were used as substrates under the sensors. The Peratech sensor averaged 94% accuracy for both static and dynamic measurements on all substrates; the Sensitronics sensor averaged 88% accuracy. The Peratech sensor displayed moderate variations and the Sensitronics sensor large variations in output pressure readings depending on the underlying test surface, both of which were reduced markedly by individual pressure calibration for surface type. Sensor choice and need for calibration to surface type are important considerations for their application in healthcare monitoring.

Flexible Sensors for Pressure Therapy: Effect of Substrate Curvature and Stiffness on Sensor Performance

PubMed Central

Khodasevych, Iryna; Parmar, Suresh

2017-01-01

Flexible pressure sensors are increasingly being used in medical and non-medical applications, and particularly in innovative health monitoring. Their efficacy in medical applications such as compression therapy depends on the accuracy and repeatability of their output, which in turn depend on factors such as sensor type, shape, pressure range, and conformability of the sensor to the body surface. Numerous researchers have examined the effects of sensor type and shape, but little information is available on the effect of human body parameters such as support surfaces’ curvature and the stiffness of soft tissues on pressure sensing performance. We investigated the effects of body parameters on the performance of pressure sensors using a custom-made human-leg-like test setup. Pressure sensing parameters such as accuracy, drift and repeatability were determined in both static (eight hours continuous pressure) and dynamic (10 cycles of pressure application of 30 s duration) testing conditions. The testing was performed with a focus on compression therapy application for venous leg ulcer treatments, and was conducted in a low-pressure range of 20–70 mmHg. Commercially available sensors manufactured by Peratech and Sensitronics were used under various loading conditions to determine the influence of stiffness and curvature. Flat rigid, flat soft silicone and three cylindrical silicone surfaces of radii of curvature of 3.5 cm, 5.5 cm and 6.5 cm were used as substrates under the sensors. The Peratech sensor averaged 94% accuracy for both static and dynamic measurements on all substrates; the Sensitronics sensor averaged 88% accuracy. The Peratech sensor displayed moderate variations and the Sensitronics sensor large variations in output pressure readings depending on the underlying test surface, both of which were reduced markedly by individual pressure calibration for surface type. Sensor choice and need for calibration to surface type are important considerations for their application in healthcare monitoring. PMID:29053605

JEUMICO: Czech-Bavarian astronomical X-ray optics project

NASA Astrophysics Data System (ADS)

Hudec, R.; Döhring, T.

2017-07-01

Within the project JEUMICO, an acronym for "Joint European Mirror Competence", the Aschaffenburg University of Applied Sciences and the Czech Technical University in Prague started a collaboration to develop mirrors for X-ray telescopes. Corresponding mirror segments use substrates of flat silicon wafers which are coated with thin iridium films, as this material is promising high reflectivity in the X-ray range of interest. The sputtering parameters are optimized in the context of the expected reflectivity of the coated X-ray mirrors. In near future measurements of the assembled mirror modules optical performances are planned at an X-ray test facility.

Thermal and optical performance of encapsulation systems for flat-plate photovoltaic modules

NASA Technical Reports Server (NTRS)

Minning, C. P.; Coakley, J. F.; Perrygo, C. M.; Garcia, A., III; Cuddihy, E. F.

1981-01-01

The electrical power output from a photovoltaic module is strongly influenced by the thermal and optical characteristics of the module encapsulation system. Described are the methodology and computer model for performing fast and accurate thermal and optical evaluations of different encapsulation systems. The computer model is used to evaluate cell temperature, solar energy transmittance through the encapsulation system, and electric power output for operation in a terrestrial environment. Extensive results are presented for both superstrate-module and substrate-module design schemes which include different types of silicon cell materials, pottants, and antireflection coatings.

Radiation dose reduction in chest radiography using a flat-panel amorphous silicon detector.

PubMed

Hosch, W P; Fink, C; Radeleff, B; kampschulte a, A; Kauffmann, G W; Hansmann, J

2002-10-01

The aim of this study was to evaluate the image quality and the potential for radiation dose reduction with a digital flat-panel amorphous silicon detector radiography system. Using flat-panel technology, radiographs of an anthropomorphic thorax phantom were taken with a range of technical parameters (125kV, 200mA and 5, 4, 3.2, 2, 1, 0.5, and 0.25mAs) which were equivalent to a radiation dose of 332, 263, 209, 127, 58.7, 29, and 14 microGy, respectively. These images were compared to radiographs obtained by a conventional film-screen radiography system at 125kV, 200mA and 5mAs (equivalent to 252 microGy) which served as reference. Three observers evaluated independently the visibility of simulated rounded lesions and anatomical structures, comparing printed films from the flat-panel amorphous silicon detector and conventional x-ray system films. With flat-panel technology, the visibility of rounded lesions and normal anatomical structures at 5, 4, and 3.2mAs was superior compared to the conventional film-screen radiography system. (P< or =0.0001). At 2mAs, improvement was only marginal (P=0.19). At 1.0, 0.5 and 0.25mAs, the visibility of simulated rounded lesions was worse (P< or =0.004). Comparing fine lung parenchymal structures, the flat-panel amorphous silicon detector showed improvement for all exposure levels down to 2mAs and equality at 1mAs. Compared to a conventional x-ray film system, the flat-panel amorphous silicon detector demonstrated improved image quality and the possibility for a reduction of the radiation dose by 50% without loss in image quality.

Thin Film Transistors On Plastic Substrates

DOEpatents

Carey, Paul G.; Smith, Patrick M.; Sigmon, Thomas W.; Aceves, Randy C.

2004-01-20

A process for formation of thin film transistors (TFTs) on plastic substrates replaces standard thin film transistor fabrication techniques, and uses sufficiently lower processing temperatures so that inexpensive plastic substrates may be used in place of standard glass, quartz, and silicon wafer-based substrates. The silicon based thin film transistor produced by the process includes a low temperature substrate incapable of withstanding sustained processing temperatures greater than about 250.degree. C., an insulating layer on the substrate, a layer of silicon on the insulating layer having sections of doped silicon, undoped silicon, and poly-silicon, a gate dielectric layer on the layer of silicon, a layer of gate metal on the dielectric layer, a layer of oxide on sections of the layer of silicon and the layer of gate metal, and metal contacts on sections of the layer of silicon and layer of gate metal defining source, gate, and drain contacts, and interconnects.

Machining of Silicon-Ribbon-Forming Dies

NASA Technical Reports Server (NTRS)

Menna, A. A.

1985-01-01

Carbon extension for dies used in forming silicon ribbon crystals machined precisely with help of special tool. Die extension has edges beveled toward narrow flats at top, with slot precisely oriented and centered between flats and bevels. Cutting tool assembled from standard angle cutter and circular saw or saws. Angle cutters cuts bevels while slot saw cuts slot between them. In alternative version, custom-ground edges or additional circular saws also cut flats simultaneously.

RF performances of inductors integrated on localized p+-type porous silicon regions

PubMed Central

2012-01-01

To study the influence of localized porous silicon regions on radiofrequency performances of passive devices, inductors were integrated on localized porous silicon regions, full porous silicon sheet, bulk silicon and glass substrates. In this work, a novel strong, resistant fluoropolymer mask is introduced to localize the porous silicon on the silicon wafer. Then, the quality factors and resonant frequencies obtained with the different substrates are presented. A first comparison is done between the performances of inductors integrated on same-thickness localized and full porous silicon sheet layers. The effect of the silicon regions in the decrease of performances of localized porous silicon is discussed. Then, the study shows that the localized porous silicon substrate significantly reduces losses in comparison with high-resistivity silicon or highly doped silicon bulks. These results are promising for the integration of both passive and active devices on the same silicon/porous silicon hybrid substrate. PMID:23009746

Toward Intelligent Synthetic Neural Circuits: Directing and Accelerating Neuron Cell Growth by Self-Rolled-Up Silicon Nitride Microtube Array

PubMed Central

2015-01-01

In neural interface platforms, cultures are often carried out on a flat, open, rigid, and opaque substrate, posing challenges to reflecting the native microenvironment of the brain and precise engagement with neurons. Here we present a neuron cell culturing platform that consists of arrays of ordered microtubes (2.7–4.4 μm in diameter), formed by strain-induced self-rolled-up nanomembrane (s-RUM) technology using ultrathin (<40 nm) silicon nitride (SiNx) film on transparent substrates. These microtubes demonstrated robust physical confinement and unprecedented guidance effect toward outgrowth of primary cortical neurons, with a coaxially confined configuration resembling that of myelin sheaths. The dynamic neural growth inside the microtube, evaluated with continuous live-cell imaging, showed a marked increase (20×) of the growth rate inside the microtube compared to regions outside the microtubes. We attribute the dramatic accelerating effect and precise guiding of the microtube array to three-dimensional (3D) adhesion and electrostatic interaction with the SiNx microtubes, respectively. This work has clear implications toward building intelligent synthetic neural circuits by arranging the size, site, and patterns of the microtube array, for potential treatment of neurological disorders. PMID:25329686

Low-temperature silicon thin films for large-area electronics: Device fabrication using soft lithography and laser-crystallization by sequential lateral solidification

NASA Astrophysics Data System (ADS)

Jin, Hyun-Chul

This work demonstrates possible routes for fabricating large-area electronic devices on glass or plastic substrates using low-temperature materials deposition and soft lithographic device patterning. Hydrogenated amorphous silicon (a-Si:H) and polycrystalline silicon (poly-Si) have been extensively studied as the semiconducting material for flat panel displays and solar cells. On glass substrates, we have deposited a-Si:H films at a temperature lower than 125°C, and we have used pulsed excimer laser crystallization in the sequential lateral solidification (SLS) regime to fabricate poly-Si films. We use micromolding in capillaries (MIMIC), a form of soft lithography involving micrometer-scale polymer molding, as a means to fabricate amorphous silicon thin-film transistors (TFTs), and photoconductive sensor arrays on both planar and curved substrates. The use of non-planar substrates has captured considerable attention in the field because it would open up new applications and new designs. Field-effect transistors made by SLS poly-Si show excellent mobility and on/off current ratio; however, the microstructure of the material had never been well documented. We determined the microtexture using electron backscattering diffraction (EBSD): the first crystallites formed in the a-Si layer are random; along the direction of the solidification, a strong <100> in-plane orientation quickly develops due to competitive growth and occlusion. The misorientation angle between neighboring grains is also analyzed. A large fraction of the boundaries within the material are low-angle and coincidence site lattice (CSL) types. We discuss the implications of the findings on the defect generation mechanism and on the electrical properties of the films. We have analyzed the electrical properties of SLS poly-Si films on oxidized Si wafer using the pseudo-MOSFET geometry; the majority carrier mobility is extracted from the transconductance. However, the data are non-ideal due to large contact resistance and current spreading. We discuss the future use of these electrical characterization techniques to analyze the properties of individual grain boundaries in thin film Si bicrystals formed by SLS.

Development of Aspherical Active Gratings at NSRRC

NASA Astrophysics Data System (ADS)

Tseng, Tse-Chuan; Wang, Duan Jen; Perng, Shen-Yaw; Chen, Chien-Te; Lin, Chia-Jui; Kuan, Chien-Kuang; Ho, His-Chou; Wang, Jeremy; Fung, H. S.; Chang, Shuo-Hung

2007-01-01

An active grating based on a novel optical concept with bendable polynomial surface profile to reduce the coma and defocus aberrations had been designed and proved by the prototype testing. Due to the low glass transition temperature of the glue and the difference of thermal expansion coefficient between the 17-4 steel bender and silicon, the prototype distorted from flat polished condition when thermally de-blocked the polishing pitch. To improve the thermal deformation of the active grating in the polishing process, a new invar bender and high curing temperature glue were adapted to glue a silicon substrate on the bender. After some tests and manufacturer polishing, it showed acceptable conditions. In this paper we will present the design and preliminary tests of the invar active grating. Meanwhile, the design and analysis of a new 17-4 PH steel bender to be electro-less nickel plating and mechanical ruling for a new beamline will also be discussed.

Ultralight shape-recovering plate mechanical metamaterials

NASA Astrophysics Data System (ADS)

Davami, Keivan; Zhao, Lin; Lu, Eric; Cortes, John; Lin, Chen; Lilley, Drew E.; Purohit, Prashant K.; Bargatin, Igor

2015-12-01

Unusual mechanical properties of mechanical metamaterials are determined by their carefully designed and tightly controlled geometry at the macro- or nanoscale. We introduce a class of nanoscale mechanical metamaterials created by forming continuous corrugated plates out of ultrathin films. Using a periodic three-dimensional architecture characteristic of mechanical metamaterials, we fabricate free-standing plates up to 2 cm in size out of aluminium oxide films as thin as 25 nm. The plates are formed by atomic layer deposition of ultrathin alumina films on a lithographically patterned silicon wafer, followed by complete removal of the silicon substrate. Unlike unpatterned ultrathin films, which tend to warp or even roll up because of residual stress gradients, our plate metamaterials can be engineered to be extremely flat. They weigh as little as 0.1 g cm-2 and have the ability to `pop-back' to their original shape without damage even after undergoing multiple sharp bends of more than 90°.

High aspect ratio silicon nanowires control fibroblast adhesion and cytoskeleton organization

NASA Astrophysics Data System (ADS)

Andolfi, Laura; Murello, Anna; Cassese, Damiano; Ban, Jelena; Dal Zilio, Simone; Lazzarino, Marco

2017-04-01

Cell-cell and cell-matrix interactions are essential to the survival and proliferation of most cells, and are responsible for triggering a wide range of biochemical pathways. More recently, the biomechanical role of those interactions was highlighted, showing, for instance, that adhesion forces are essential for cytoskeleton organization. Silicon nanowires (Si NWs) with their small size, high aspect ratio and anisotropic mechanical response represent a useful model to investigate the forces involved in the adhesion processes and their role in cellular development. In this work we explored and quantified, by single cell force spectroscopy (SCFS), the interaction of mouse embryonic fibroblasts with a flexible forest of Si NWs. We observed that the cell adhesion forces are comparable to those found on collagen and bare glass coverslip, analogously the membrane tether extraction forces are similar to that on collagen but stronger than that on bare flat glass. Cell survival did not depend significantly on the substrate, although a reduced proliferation after 36 h was observed. On the contrary both cell morphology and cytoskeleton organization revealed striking differences. The cell morphology on Si-NW was characterized by a large number of filopodia and a significant decrease of the cell mobility. The cytoskeleton organization was characterized by the absence of actin fibers, which were instead dominant on collagen and flat glass support. Such findings suggest that the mechanical properties of disordered Si NWs, and in particular their strong asymmetry, play a major role in the adhesion, morphology and cytoskeleton organization processes. Indeed, while adhesion measurements by SCFS provide out-of-plane forces values consistent with those measured on conventional substrates, weaker in-plane forces hinder proper cytoskeleton organization and migration processes.

High aspect ratio silicon nanowires control fibroblast adhesion and cytoskeleton organization.

PubMed

Andolfi, Laura; Murello, Anna; Cassese, Damiano; Ban, Jelena; Dal Zilio, Simone; Lazzarino, Marco

2017-04-18

Cell-cell and cell-matrix interactions are essential to the survival and proliferation of most cells, and are responsible for triggering a wide range of biochemical pathways. More recently, the biomechanical role of those interactions was highlighted, showing, for instance, that adhesion forces are essential for cytoskeleton organization. Silicon nanowires (Si NWs) with their small size, high aspect ratio and anisotropic mechanical response represent a useful model to investigate the forces involved in the adhesion processes and their role in cellular development. In this work we explored and quantified, by single cell force spectroscopy (SCFS), the interaction of mouse embryonic fibroblasts with a flexible forest of Si NWs. We observed that the cell adhesion forces are comparable to those found on collagen and bare glass coverslip, analogously the membrane tether extraction forces are similar to that on collagen but stronger than that on bare flat glass. Cell survival did not depend significantly on the substrate, although a reduced proliferation after 36 h was observed. On the contrary both cell morphology and cytoskeleton organization revealed striking differences. The cell morphology on Si-NW was characterized by a large number of filopodia and a significant decrease of the cell mobility. The cytoskeleton organization was characterized by the absence of actin fibers, which were instead dominant on collagen and flat glass support. Such findings suggest that the mechanical properties of disordered Si NWs, and in particular their strong asymmetry, play a major role in the adhesion, morphology and cytoskeleton organization processes. Indeed, while adhesion measurements by SCFS provide out-of-plane forces values consistent with those measured on conventional substrates, weaker in-plane forces hinder proper cytoskeleton organization and migration processes.

High gain durable anti-reflective coating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maghsoodi, Sina; Brophy, Brenor L.; Colson, Thomas E.

Disclosed herein are polysilsesquioxane-based anti-reflective coating (ARC) compositions, methods of preparation, and methods of deposition on a substrate. In one embodiment, the polysilsesquioxane of this disclosure is prepared in a two-step process of acid catalyzed hydrolysis of organoalkoxysilane followed by addition of tetralkoxysilane that generates silicone polymers with >40 mol % silanol based on Si-NMR. These high silanol siloxane polymers are stable and have a long shelf-life in polar organic solvents at room temperature. Also disclosed are low refractive index ARC made from these compositions with and without additives such as porogens, templates, thermal radical initiator, photo radical initiators, crosslinkers,more » Si--OH condensation catalyst and nano-fillers. Also disclosed are methods and apparatus for applying coatings to flat substrates including substrate pre-treatment processes, coating processes and coating curing processes including skin-curing using hot-air knives. Also disclosed are coating compositions and formulations for highly tunable, durable, highly abrasion-resistant functionalized anti-reflective coatings.« less

Effects of supercritical carbon dioxide on immobile bound polymer chains on solid substrates

NASA Astrophysics Data System (ADS)

Sen, Mani; Asada, Mitsunori; Jiang, Naisheng; Endoh, Maya K.; Akgun, Bulent; Satija, Sushil; Koga, Tadanori

2013-03-01

Adsorbed polymer layers formed on flat solid substrates have recently been the subject of extensive studies because it is postulated to control the dynamics of technologically relevant polymer thin films, for example, in lithography. Such adsorbed layers have been reported to hinder the mobility of polymer chains in thin films even at a large length scale. Consequently, this bound layer remains immobile regardless of processing techniques (i.e. thermal annealing, solvent dissolution, etc). Here, we investigate the use of supercritical carbon dioxide (scCO2) as a novel plasticizer for bound polystyrene layers formed on silicon substrates. In-situ swelling and interdiffusion experiments using neutron reflectivity were performed. As a result, we found the anomalous plasticization effects of scCO2 on the bound polymer layers near the critical point where the anomalous adsorption of CO2 molecules in polymer thin films has been reported previously. Acknowledgement: We acknowledge the financial support from NSF Grant No. CMMI-084626.

[Technology Development for X-Ray Reflection for the Constellation-X Reflection Grating Spectrometer (RGS)

NASA Technical Reports Server (NTRS)

Schattenburg, Mark L.

2003-01-01

This Grant covers MIT support for the technology development of x-ray reflection gratings for the Constellation-X Reflection Grating Spectrometer (RGS). Since the start of the Grant MIT has extended its previously-developed patterning and super-smooth, blazed grating fabrication technology to ten-times smaller grating periods and ten-times larger blaze angles to demonstrate feasibility and performance in the off-plane grating geometry. In the past year we successfully developed several nanoimprint grating replication methods that achieved very high fidelity replication of master silicon gratings. Grating geometry on the nano and macro scales were faithfully replicated, demonstrating the viability of the process for manufacturing the thousands of gratings required for the RGS. We also successfully developed an improved metrology truss for holding test grating substrates during metrology. The flatness goal of grating substrates is under 500 nm. In the past, grating holders would cause non-repeatable distortion of >> 500 nm to the substrates due to friction and gravity sag. The new holder has a repeatability of under 50 nm which is adequate for the proposed RGS grating substrates.

Large area silicon sheet by EFG

NASA Technical Reports Server (NTRS)

Kalejs, J. P.

1982-01-01

Work carried out on the JPL Flat Plate Solar Array Project, for the purpose of developing a method for silicon ribbon production by Edge-defined Film-fed Growth (EEG) for use as low-cost substrate material in terrestrial solar cell manufacture, is described. A multiple ribbon furnace unit that is designed to operate on a continuous basis for periods of at least one week, with melt replenishment and automatic ribbon width control, and to produce silicon sheet at a rate of one square meter per hour, was constructed. Program milestones set for single ribbon furnace operation to demonstrate basic EEG system capabilities with respect to growth speed, thickness and cell performance were achieved for 10 cm wide ribbon: steady-state growth at 4 cm/min and 200 micron thickness over periods of an hour and longer was made routine, and a small area cell efficiency of 13+% demonstrated. Large area cells of average efficiency of 10 to 11%, with peak values of 11 to 12% were also achieved. The integration of these individual performance levels into multiple ribbon furnace operation was not accomplished.

Flat Plate Solar Array Project: Proceedings of the 20th Project Integration Meeting

NASA Technical Reports Server (NTRS)

Mcdonald, R. R.

1982-01-01

Progress made by the Flat-Plate Solar Array Project during the period November 1981 to April 1982 is reported. Project analysis and integration, technology research in silicon material, large-area silicon sheet and environmental isolation, cell and module formation, engineering sciences, and module performance and failure analysis are covered.

Study of surface reaction during selective epitaxy growth of silicon by thermodynamic analysis and density functional theory calculation

NASA Astrophysics Data System (ADS)

Mayangsari, Tirta R.; Yusup, Luchana L.; Park, Jae-Min; Blanquet, Elisabeth; Pons, Michel; Jung, Jongwan; Lee, Won-Jun

2017-06-01

We modeled and simulated the surface reaction of silicon precursor on different surfaces by thermodynamic analysis and density functional theory calculation. We considered SiH2Cl2 and argon as the silicon precursor and the carrier gas without etchant gas. First, the equilibrium composition of both gaseous and solid species was analyzed as a function of process temperature. SiCl4 is the dominant gaseous species at below 750 °C, and SiCl2 and HCl are dominant at higher temperatures, and the yield of silicon decreases with increasing temperature over 700 °C due to the etching of silicon by HCl. The yield of silicon for SiO2 substrate is lower than that for silicon substrate, especially at 1000 °C or higher. Zero deposition yield and the etching of SiO2 substrate at higher temperatures leads to selective growth on silicon substrate. Next, the adsorption and the reaction of silicon precursor was simulated on H-terminated silicon (100) substrate and on OH-terminated β-cristobalite substrate. The adsorption and reaction of a SiH2Cl2 molecule are spontaneous for both Si and SiO2 substrates. However, the energy barrier for reaction is very small (6×10-4 eV) for Si substrate, whereas the energy barrier is high (0.33 eV) for SiO2 substrate. This makes the differences in growth rate, which also supports the experimental results in literature.

Epitaxial growth of silicon for layer transfer

DOEpatents

Teplin, Charles; Branz, Howard M

2015-03-24

Methods of preparing a thin crystalline silicon film for transfer and devices utilizing a transferred crystalline silicon film are disclosed. The methods include preparing a silicon growth substrate which has an interface defining substance associated with an exterior surface. The methods further include depositing an epitaxial layer of silicon on the silicon growth substrate at the surface and separating the epitaxial layer from the substrate substantially along the plane or other surface defined by the interface defining substance. The epitaxial layer may be utilized as a thin film of crystalline silicon in any type of semiconductor device which requires a crystalline silicon layer. In use, the epitaxial transfer layer may be associated with a secondary substrate.

Anti-reflective device having an anti-reflective surface formed of silicon spikes with nano-tips

NASA Technical Reports Server (NTRS)

Bae, Youngsam (Inventor); Manohara, Harish (Inventor); Mobasser, Sohrab (Inventor); Lee, Choonsup (Inventor)

2011-01-01

Described is a device having an anti-reflection surface. The device comprises a silicon substrate with a plurality of silicon spikes formed on the substrate. A first metallic layer is formed on the silicon spikes to form the anti-reflection surface. The device further includes an aperture that extends through the substrate. A second metallic layer is formed on the substrate. The second metallic layer includes a hole that is aligned with the aperture. A spacer is attached with the silicon substrate to provide a gap between an attached sensor apparatus. Therefore, operating as a Micro-sun sensor, light entering the hole passes through the aperture to be sensed by the sensor apparatus. Additionally, light reflected by the sensor apparatus toward the first side of the silicon substrate is absorbed by the first metallic layer and silicon spikes and is thereby prevented from being reflected back toward the sensor apparatus.

Anti- reflective device having an anti-reflection surface formed of silicon spikes with nano-tips

NASA Technical Reports Server (NTRS)

Bae, Youngsman (Inventor); Mooasser, Sohrab (Inventor); Manohara, Harish (Inventor); Lee, Choonsup (Inventor); Bae, Kungsam (Inventor)

2009-01-01

Described is a device having an anti-reflection surface. The device comprises a silicon substrate with a plurality of silicon spikes formed on the substrate. A first metallic layer is formed on the silicon spikes to form the anti-reflection surface. The device further includes an aperture that extends through the substrate. A second metallic layer is formed on the substrate. The second metallic layer includes a hole that is aligned with the aperture. A spacer is attached with the silicon substrate to provide a gap between an attached sensor apparatus. Therefore, operating as a Micro-sun sensor, light entering the hole passes through the aperture to be sensed by the sensor apparatus. Additionally, light reflected by the sensor apparatus toward the first side of the silicon substrate is absorbed by the first metallic layer and silicon spikes and is thereby prevented from being reflected back toward the sensor apparatus.

Ceramic with preferential oxygen reactive layer

NASA Technical Reports Server (NTRS)

Wang, Hongyu (Inventor); Luthra, Krishan Lal (Inventor)

2001-01-01

An article comprises a silicon-containing substrate and an external environmental/thermal barrier coating. The external environmental/thermal barrier coating is permeable to diffusion of an environmental oxidant and the silicon-containing substrate is oxidizable by reaction with oxidant to form at least one gaseous product. The article comprises an intermediate layer/coating between the silicon-containing substrate and the environmental/thermal barrier coating that is oxidizable to a nongaseous product by reaction with the oxidant in preference to reaction of the silicon-containing substrate with the oxidant. A method of forming an article, comprises forming a silicon-based substrate that is oxidizable by reaction with oxidant to at least one gaseous product and applying an intermediate layer/coating onto the substrate, wherein the intermediate layer/coating is oxidizable to a nongaseous product by reaction with the oxidant in preference to reaction of the silicon-containing substrate with the oxidant.

Repair of high performance multilayer coatings

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gaines, D.P.; Ceglio, N.M.; Vernon, S.P.

1991-07-01

Fabrication and environmental damage issues may require that the multilayer x-ray reflection coatings used in soft x-ray projection lithography be replaced or repaired. Two repair strategies were investigated. The first was to overcoat defective multilayers with a new multilayer. The feasibility of this approach was demonstrated by depositing high reflectivity (61% at 130 {Angstrom}) molybdenum silicon (Mo/Si) multilayers onto fused silica figured optics that had already been coated with a Mo/Si multilayer. Because some types of damage mechanisms and fabrication errors are not repairable by this method, a second method of repair was investigated. The multilayer was stripped from themore » optical substrate by etching a release layer which was deposited onto the substrate beneath the multilayer. The release layer consisted of a 1000 {Angstrom} aluminum film deposited by ion beam sputtering or by electron beam evaporation, with a 300 {Angstrom} SiO{sub 2} protective overcoat. The substrates were superpolished zerodur optical flats. The normal incidence x-ray reflectivity of multilayers deposited on these aluminized substrates was degraded, presumably due to the roughness of the aluminum films. Multilayers, and the underlying release layers, have been removed without damaging the substrates.« less

Hierarchical macroscopic fibrillar adhesives: in situ study of buckling and adhesion mechanisms on wavy substrates.

PubMed

Bauer, Christina T; Kroner, Elmar; Fleck, Norman A; Arzt, Eduard

2015-10-23

Nature uses hierarchical fibrillar structures to mediate temporary adhesion to arbitrary substrates. Such structures provide high compliance such that the flat fibril tips can be better positioned with respect to asperities of a wavy rough substrate. We investigated the buckling and adhesion of hierarchically structured adhesives in contact with flat smooth, flat rough and wavy rough substrates. A macroscopic model for the structural adhesive was fabricated by molding polydimethylsiloxane into pillars of diameter in the range of 0.3-4.8 mm, with up to three different hierarchy levels. Both flat-ended and mushroom-shaped hierarchical samples buckled at preloads one quarter that of the single level structures. We explain this behavior by a change in the buckling mode; buckling leads to a loss of contact and diminishes adhesion. Our results indicate that hierarchical structures can have a strong influence on the degree of adhesion on both flat and wavy substrates. Strategies are discussed that achieve highly compliant substrates which adhere to rough substrates.

Chemical vapor deposition of epitaxial silicon

DOEpatents

Berkman, Samuel

1984-01-01

A single chamber continuous chemical vapor deposition (CVD) reactor is described for depositing continuously on flat substrates, for example, epitaxial layers of semiconductor materials. The single chamber reactor is formed into three separate zones by baffles or tubes carrying chemical source material and a carrier gas in one gas stream and hydrogen gas in the other stream without interaction while the wafers are heated to deposition temperature. Diffusion of the two gas streams on heated wafers effects the epitaxial deposition in the intermediate zone and the wafers are cooled in the final zone by coolant gases. A CVD reactor for batch processing is also described embodying the deposition principles of the continuous reactor.

Back contact to film silicon on metal for photovoltaic cells

DOEpatents

Branz, Howard M.; Teplin, Charles; Stradins, Pauls

2013-06-18

A crystal oriented metal back contact for solar cells is disclosed herein. In one embodiment, a photovoltaic device and methods for making the photovoltaic device are disclosed. The photovoltaic device includes a metal substrate with a crystalline orientation and a heteroepitaxial crystal silicon layer having the same crystal orientation of the metal substrate. A heteroepitaxial buffer layer having the crystal orientation of the metal substrate is positioned between the substrate and the crystal silicon layer to reduce diffusion of metal from the metal foil into the crystal silicon layer and provide chemical compatibility with the heteroepitaxial crystal silicon layer. Additionally, the buffer layer includes one or more electrically conductive pathways to electrically couple the crystal silicon layer and the metal substrate.

Surface treatment effect on Si (111) substrate for carbon deposition using DC unbalanced magnetron sputtering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aji, A. S., E-mail: aji.ravazes70@gmail.com; Sahdan, M. F.; Hendra, I. B.

In this work, we studied the effect of HF treatment in silicon (111) substrate surface for depositing thin layer carbon. We performed the deposition of carbon by using DC Unbalanced Magnetron Sputtering with carbon pallet (5% Fe) as target. From SEM characterization results it can be concluded that the carbon layer on HF treated substrate is more uniform than on substrate without treated. Carbon deposition rate is higher as confirmed by AFM results if the silicon substrate is treated by HF solution. EDAX characterization results tell that silicon (111) substrate with HF treatment have more carbon fraction than substrate withoutmore » treatment. These results confirmed that HF treatment on silicon Si (111) substrates could enhance the carbon deposition by using DC sputtering. Afterward, the carbon atomic arrangement on silicon (111) surface is studied by performing thermal annealing process to 900 °C. From Raman spectroscopy results, thin film carbon is not changing until 600 °C thermal budged. But, when temperature increase to 900 °C, thin film carbon is starting to diffuse to silicon (111) substrates.« less

Flat-plate solar array project. Volume 3: Silicon sheet: Wafers and ribbons

NASA Technical Reports Server (NTRS)

Briglio, A.; Dumas, K.; Leipold, M.; Morrison, A.

1986-01-01

The primary objective of the Silicon Sheet Task of the Flat-Plate Solar Array (FSA) Project was the development of one or more low cost technologies for producing silicon sheet suitable for processing into cost-competitive solar cells. Silicon sheet refers to high purity crystalline silicon of size and thickness for fabrication into solar cells. Areas covered in the project were ingot growth and casting, wafering, ribbon growth, and other sheet technologies. The task made and fostered significant improvements in silicon sheet including processing of both ingot and ribbon technologies. An additional important outcome was the vastly improved understanding of the characteristics associated with high quality sheet, and the control of the parameters required for higher efficiency solar cells. Although significant sheet cost reductions were made, the technology advancements required to meet the task cost goals were not achieved.

Alkylation of Silicon(111) surfaces

NASA Astrophysics Data System (ADS)

Rivillon, S.; Chabal, Y. J.

2006-03-01

Methylation of chlorine-terminated silicon (111) (Si-Cl) is investigated by Infra Red Absorption Spectroscopy (IRAS). Starting from an atomically flat H-terminated Si(111), the surface is first chlorinated by a gas phase process, then methylated using a Grignard reagent. Methyl groups completely replace Cl, and are oriented normal to the surface. The surface remains atomically flat with no evidence of etching.

Deposition method for producing silicon carbide high-temperature semiconductors

DOEpatents

Hsu, George C.; Rohatgi, Naresh K.

1987-01-01

An improved deposition method for producing silicon carbide high-temperature semiconductor material comprising placing a semiconductor substrate composed of silicon carbide in a fluidized bed silicon carbide deposition reactor, fluidizing the bed particles by hydrogen gas in a mildly bubbling mode through a gas distributor and heating the substrate at temperatures around 1200.degree.-1500.degree. C. thereby depositing a layer of silicon carbide on the semiconductor substrate.

3.4-Inch Quarter High Definition Flexible Active Matrix Organic Light Emitting Display with Oxide Thin Film Transistor

NASA Astrophysics Data System (ADS)

Hatano, Kaoru; Chida, Akihiro; Okano, Tatsuya; Sugisawa, Nozomu; Inoue, Tatsunori; Seo, Satoshi; Suzuki, Kunihiko; Oikawa, Yoshiaki; Miyake, Hiroyuki; Koyama, Jun; Yamazaki, Shunpei; Eguchi, Shingo; Katayama, Masahiro; Sakakura, Masayuki

2011-03-01

In this paper, we report a 3.4-in. flexible active matrix organic light emitting display (AMOLED) display with remarkably high definition (quarter high definition: QHD) in which oxide thin film transistors (TFTs) are used. We have developed a transfer technology in which a TFT array formed on a glass substrate is separated from the substrate by physical force and then attached to a flexible plastic substrate. Unlike a normal process in which a TFT array is directly fabricated on a thin plastic substrate, our transfer technology permits a high integration of high performance TFTs, such as low-temperature polycrystalline silicon TFTs (LTPS TFTs) and oxide TFTs, on a plastic substrate, because a flat, rigid, and thermally-stable glass substrate can be used in the TFT fabrication process in our transfer technology. As a result, this technology realized an oxide TFT array for an AMOLED on a plastic substrate. Furthermore, in order to achieve a high-definition AMOLED, color filters were incorporated in the TFT array and a white organic light-emitting diode (OLED) was combined. One of the features of this device is that the whole body of the device can be bent freely because a source driver and a gate driver can be integrated on the substrate due to the high mobility of an oxide TFT. This feature means “true” flexibility.

Polyelectrolyte multilayer-assisted fabrication of non-periodic silicon nanocolumn substrates for cellular interface applications

NASA Astrophysics Data System (ADS)

Lee, Seyeong; Kim, Dongyoon; Kim, Seong-Min; Kim, Jeong-Ah; Kim, Taesoo; Kim, Dong-Yu; Yoon, Myung-Han

2015-08-01

Recent advances in nanostructure-based biotechnology have resulted in a growing demand for vertical nanostructure substrates with elaborate control over the nanoscale geometry and a high-throughput preparation. In this work, we report the fabrication of non-periodic vertical silicon nanocolumn substrates via polyelectrolyte multilayer-enabled randomized nanosphere lithography. Owing to layer-by-layer deposited polyelectrolyte adhesives, uniformly-separated polystyrene nanospheres were securely attached on large silicon substrates and utilized as masks for the subsequent metal-assisted silicon etching in solution. Consequently, non-periodic vertical silicon nanocolumn arrays were successfully fabricated on a wafer scale, while each nanocolumn geometric factor, such as the diameter, height, density, and spatial patterning, could be fully controlled in an independent manner. Finally, we demonstrate that our vertical silicon nanocolumn substrates support viable cell culture with minimal cell penetration and unhindered cell motility due to the blunt nanocolumn morphology. These results suggest that vertical silicon nanocolumn substrates may serve as a useful cellular interface platform for performing a statistically meaningful number of cellular experiments in the fields of biomolecular delivery, stem cell research, etc.Recent advances in nanostructure-based biotechnology have resulted in a growing demand for vertical nanostructure substrates with elaborate control over the nanoscale geometry and a high-throughput preparation. In this work, we report the fabrication of non-periodic vertical silicon nanocolumn substrates via polyelectrolyte multilayer-enabled randomized nanosphere lithography. Owing to layer-by-layer deposited polyelectrolyte adhesives, uniformly-separated polystyrene nanospheres were securely attached on large silicon substrates and utilized as masks for the subsequent metal-assisted silicon etching in solution. Consequently, non-periodic vertical silicon nanocolumn arrays were successfully fabricated on a wafer scale, while each nanocolumn geometric factor, such as the diameter, height, density, and spatial patterning, could be fully controlled in an independent manner. Finally, we demonstrate that our vertical silicon nanocolumn substrates support viable cell culture with minimal cell penetration and unhindered cell motility due to the blunt nanocolumn morphology. These results suggest that vertical silicon nanocolumn substrates may serve as a useful cellular interface platform for performing a statistically meaningful number of cellular experiments in the fields of biomolecular delivery, stem cell research, etc. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02384j

Impact of process parameters on the structural and electrical properties of metal/PZT/Al2O3/silicon gate stack for non-volatile memory applications

NASA Astrophysics Data System (ADS)

Singh, Prashant; Jha, Rajesh Kumar; Singh, Rajat Kumar; Singh, B. R.

2018-02-01

In this paper, we present the structural and electrical properties of the Al2O3 buffer layer on non-volatile memory behavior using Metal/PZT/Al2O3/Silicon structures. Metal/PZT/Silicon and Metal/Al2O3/Silicon structures were also fabricated and characterized to obtain capacitance and leakage current parameters. Lead zirconate titanate (PZT::35:65) and Al2O3 films were deposited by sputtering on the silicon substrate. Memory window, PUND, endurance, breakdown voltage, effective charges, flat-band voltage and leakage current density parameters were measured and the effects of process parameters on the structural and electrical characteristics were investigated. X-ray data show dominant (110) tetragonal phase of the PZT film, which crystallizes at 500 °C. The sputtered Al2O3 film annealed at different temperatures show dominant (312) orientation and amorphous nature at 425 °C. Multiple angle laser ellipsometric analysis reveals the temperature dependence of PZT film refractive index and extinction coefficient. Electrical characterization shows the maximum memory window of 3.9 V and breakdown voltage of 25 V for the Metal/Ferroelectric/Silicon (MFeS) structures annealed at 500 °C. With 10 nm Al2O3 layer in the Metal/Ferroelectric/Insulator/Silicon (MFeIS) structure, the memory window and breakdown voltage was improved to 7.21 and 35 V, respectively. Such structures show high endurance with no significant reduction polarization charge for upto 2.2 × 109 iteration cycles.

Application Of Optical Processing For Growth Of Silicon Dioxide

DOEpatents

Sopori, Bhushan L.

1997-06-17

A process for producing a silicon dioxide film on a surface of a silicon substrate. The process comprises illuminating a silicon substrate in a substantially pure oxygen atmosphere with a broad spectrum of visible and infrared light at an optical power density of from about 3 watts/cm.sup.2 to about 6 watts/cm.sup.2 for a time period sufficient to produce a silicon dioxide film on the surface of the silicon substrate. An optimum optical power density is about 4 watts/cm.sup.2 for growth of a 100.ANG.-300.ANG. film at a resultant temperature of about 400.degree. C. Deep level transient spectroscopy analysis detects no measurable impurities introduced into the silicon substrate during silicon oxide production and shows the interface state density at the SiO.sub.2 /Si interface to be very low.

Fabricating amorphous silicon solar cells by varying the temperature _of the substrate during deposition of the amorphous silicon layer

DOEpatents

Carlson, David E.

1982-01-01

An improved process for fabricating amorphous silicon solar cells in which the temperature of the substrate is varied during the deposition of the amorphous silicon layer is described. Solar cells manufactured in accordance with this process are shown to have increased efficiencies and fill factors when compared to solar cells manufactured with a constant substrate temperature during deposition of the amorphous silicon layer.

Long-lasting antifog plasma modification of transparent plastics.

PubMed

Di Mundo, Rosa; d'Agostino, Riccardo; Palumbo, Fabio

2014-10-08

Antifog surfaces are necessary for any application requiring optical efficiency of transparent materials. Surface modification methods aimed toward increasing solid surface energy, even when supposed to be permanent, in fact result in a nondurable effect due to the instability in air of highly hydrophilic surfaces. We propose the strategy of combining a hydrophilic chemistry with a nanotextured topography, to tailor a long-lasting antifog modification on commercial transparent plastics. In particular, we investigated a two-step process consisting of self-masked plasma etching followed by plasma deposition of a silicon-based film. We show that the deposition of the silicon-based coatings on the flat (pristine) substrates allows a continuous variation of wettability from hydrophobic to superhydrophilic, due to a continuous reduction of carbon-containing groups, as assessed by Fourier transform infrared and X-ray photoelectron spectroscopies. By depositing these different coatings on previously nanotextured substrates, the surface wettability behavior is changed consistently, as well as the condensation phenomenon in terms of microdroplets/liquid film appearance. This variation is correlated with advancing and receding water contact angle features of the surfaces. More importantly, in the case of the superhydrophilic coating, though its surface energy decreases with time, when a nanotextured surface underlies it, the wetting behavior is maintained durably superhydrophilic, thus durably antifog.

Efficient dielectric metasurface collimating lenses for mid-infrared quantum cascade lasers.

PubMed

Arbabi, Amir; Briggs, Ryan M; Horie, Yu; Bagheri, Mahmood; Faraon, Andrei

2015-12-28

Light emitted from single-mode semiconductor lasers generally has large divergence angles, and high numerical aperture lenses are required for beam collimation. Visible and near infrared lasers are collimated using aspheric glass or plastic lenses, yet collimation of mid-infrared quantum cascade lasers typically requires more costly aspheric lenses made of germanium, chalcogenide compounds, or other infrared-transparent materials. Here we report mid-infrared dielectric metasurface flat lenses that efficiently collimate the output beam of single-mode quantum cascade lasers. The metasurface lenses are composed of amorphous silicon posts on a flat sapphire substrate and can be fabricated at low cost using a single step conventional UV binary lithography. Mid-infrared radiation from a 4.8 μm distributed-feedback quantum cascade laser is collimated using a polarization insensitive metasurface lens with 0.86 numerical aperture and 79% transmission efficiency. The collimated beam has a half divergence angle of 0.36° and beam quality factor of M2=1.02.

Efficient dielectric metasurface collimating lenses for mid-infrared quantum cascade lasers

DOE PAGES

Arbabi, Amir; Briggs, Ryan M.; Horie, Yu; ...

2015-01-01

Light emitted from single-mode semiconductor lasers generally has large divergence angles, and high numerical aperture lenses are required for beam collimation. Visible and near infrared lasers are collimated using aspheric glass or plastic lenses, yet collimation of mid-infrared quantum cascade lasers typically requires more costly aspheric lenses made of germanium, chalcogenide compounds, or other infrared-transparent materials. We report mid-infrared dielectric metasurface flat lenses that efficiently collimate the output beam of single-mode quantum cascade lasers. The metasurface lenses are composed of amorphous silicon posts on a flat sapphire substrate and can be fabricated at low cost using a single step conventionalmore » UV binary lithography. Mid-infrared radiation from a 4.8 μm distributed-feedback quantum cascade laser is collimated using a polarization insensitive metasurface lens with 0.86 numerical aperture and 79% transmission efficiency. The collimated beam has a half divergence angle of 0.36° and beam quality factor of M² =1.02.« less

Fabrication of Buried Nanochannels From Nanowire Patterns

NASA Technical Reports Server (NTRS)

Choi, Daniel; Yang, Eui-Hyeok

2007-01-01

A method of fabricating channels having widths of tens of nanometers in silicon substrates and burying the channels under overlying layers of dielectric materials has been demonstrated. With further refinement, the method might be useful for fabricating nanochannels for manipulation and analysis of large biomolecules at single-molecule resolution. Unlike in prior methods, burying the channels does not involve bonding of flat wafers to the silicon substrates to cover exposed channels in the substrates. Instead, the formation and burying of the channels are accomplished in a more sophisticated process that is less vulnerable to defects in the substrates and less likely to result in clogging of, or leakage from, the channels. In this method, the first step is to establish the channel pattern by forming an array of sacrificial metal nanowires on an SiO2-on-Si substrate. In particular, the wire pattern is made by use of focused-ion-beam (FIB) lithography and a subsequent metallization/lift-off process. The pattern of metal nanowires is then transferred onto the SiO2 layer by reactive-ion etching, which yields sacrificial SiO2 nanowires covered by metal. After removal of the metal covering the SiO2 nanowires, what remains are SiO2 nanowires on an Si substrate. Plasma-enhanced chemical vapor deposition (PECVD) is used to form a layer of a dielectric material over the Si substrate and over the SiO2 wires on the surface of the substrate. FIB milling is then performed to form trenches at both ends of each SiO2 wire. The trenches serve as openings for the entry of chemicals that etch SiO2 much faster than they etch Si. Provided that the nanowires are not so long that the diffusion of the etching chemicals is blocked, the sacrificial SiO2 nanowires become etched out from between the dielectric material and the Si substrate, leaving buried channels. At the time of reporting the information for this article, channels 3 m long, 20 nm deep, and 80 nm wide (see figure) had been fabricated by this method.

Monolayer Contact Doping of Silicon Surfaces and Nanowires Using Organophosphorus Compounds

PubMed Central

Hazut, Ori; Agarwala, Arunava; Subramani, Thangavel; Waichman, Sharon; Yerushalmi, Roie

2013-01-01

Monolayer Contact Doping (MLCD) is a simple method for doping of surfaces and nanostructures1. MLCD results in the formation of highly controlled, ultra shallow and sharp doping profiles at the nanometer scale. In MLCD process the dopant source is a monolayer containing dopant atoms. In this article a detailed procedure for surface doping of silicon substrate as well as silicon nanowires is demonstrated. Phosphorus dopant source was formed using tetraethyl methylenediphosphonate monolayer on a silicon substrate. This monolayer containing substrate was brought to contact with a pristine intrinsic silicon target substrate and annealed while in contact. Sheet resistance of the target substrate was measured using 4 point probe. Intrinsic silicon nanowires were synthesized by chemical vapor deposition (CVD) process using a vapor-liquid-solid (VLS) mechanism; gold nanoparticles were used as catalyst for nanowire growth. The nanowires were suspended in ethanol by mild sonication. This suspension was used to dropcast the nanowires on silicon substrate with a silicon nitride dielectric top layer. These nanowires were doped with phosphorus in similar manner as used for the intrinsic silicon wafer. Standard photolithography process was used to fabricate metal electrodes for the formation of nanowire based field effect transistor (NW-FET). The electrical properties of a representative nanowire device were measured by a semiconductor device analyzer and a probe station. PMID:24326774

Electroless epitaxial etching for semiconductor applications

DOEpatents

McCarthy, Anthony M.

2002-01-01

A method for fabricating thin-film single-crystal silicon on insulator substrates using electroless etching for achieving efficient etch stopping on epitaxial silicon substrates. Microelectric circuits and devices are prepared on epitaxial silicon wafers in a standard fabrication facility. The wafers are bonded to a holding substrate. The silicon bulk is removed using electroless etching leaving the circuit contained within the epitaxial layer remaining on the holding substrate. A photolithographic operation is then performed to define streets and wire bond pad areas for electrical access to the circuit.

Thermally-isolated silicon-based integrated circuits and related methods

DOEpatents

Wojciechowski, Kenneth; Olsson, Roy H.; Clews, Peggy J.; Bauer, Todd

2017-05-09

Thermally isolated devices may be formed by performing a series of etches on a silicon-based substrate. As a result of the series of etches, silicon material may be removed from underneath a region of an integrated circuit (IC). The removal of the silicon material from underneath the IC forms a gap between remaining substrate and the integrated circuit, though the integrated circuit remains connected to the substrate via a support bar arrangement that suspends the integrated circuit over the substrate. The creation of this gap functions to release the device from the substrate and create a thermally-isolated integrated circuit.

Method for forming metallic silicide films on silicon substrates by ion beam deposition

DOEpatents

Zuhr, Raymond A.; Holland, Orin W.

1990-01-01

Metallic silicide films are formed on silicon substrates by contacting the substrates with a low-energy ion beam of metal ions while moderately heating the substrate. The heating of the substrate provides for the diffusion of silicon atoms through the film as it is being formed to the surface of the film for interaction with the metal ions as they contact the diffused silicon. The metallic silicide films provided by the present invention are contaminant free, of uniform stoichiometry, large grain size, and exhibit low resistivity values which are of particular usefulness for integrated circuit production.

Back-side hydrogenation technique for defect passivation in silicon solar cells

DOEpatents

Sopori, Bhushan L.

1994-01-01

A two-step back-side hydrogenation process includes the steps of first bombarding the back side of the silicon substrate with hydrogen ions with intensities and for a time sufficient to implant enough hydrogen atoms into the silicon substrate to potentially passivate substantially all of the defects and impurities in the silicon substrate, and then illuminating the silicon substrate with electromagnetic radiation to activate the implanted hydrogen, so that it can passivate the defects and impurities in the substrate. The illumination step also annihilates the hydrogen-induced defects. The illumination step is carried out according to a two-stage illumination schedule, the first or low-power stage of which subjects the substrate to electromagnetic radiation that has sufficient intensity to activate the implanted hydrogen, yet not drive the hydrogen from the substrate. The second or high-power illumination stage subjects the substrate to higher intensity electromagnetic radiation, which is sufficient to annihilate the hydrogen-induced defects and sinter/alloy the metal contacts.

Back-side hydrogenation technique for defect passivation in silicon solar cells

DOEpatents

Sopori, B.L.

1994-04-19

A two-step back-side hydrogenation process includes the steps of first bombarding the back side of the silicon substrate with hydrogen ions with intensities and for a time sufficient to implant enough hydrogen atoms into the silicon substrate to potentially passivate substantially all of the defects and impurities in the silicon substrate, and then illuminating the silicon substrate with electromagnetic radiation to activate the implanted hydrogen, so that it can passivate the defects and impurities in the substrate. The illumination step also annihilates the hydrogen-induced defects. The illumination step is carried out according to a two-stage illumination schedule, the first or low-power stage of which subjects the substrate to electromagnetic radiation that has sufficient intensity to activate the implanted hydrogen, yet not drive the hydrogen from the substrate. The second or high-power illumination stage subjects the substrate to higher intensity electromagnetic radiation, which is sufficient to annihilate the hydrogen-induced defects and sinter/alloy the metal contacts. 3 figures.

High quality silicon-based substrates for microwave and millimeter wave passive circuits

NASA Astrophysics Data System (ADS)

Belaroussi, Y.; Rack, M.; Saadi, A. A.; Scheen, G.; Belaroussi, M. T.; Trabelsi, M.; Raskin, J.-P.

2017-09-01

Porous silicon substrate is very promising for next generation wireless communication requiring the avoidance of high-frequency losses originating from the bulk silicon. In this work, new variants of porous silicon (PSi) substrates have been introduced. Through an experimental RF performance, the proposed PSi substrates have been compared with different silicon-based substrates, namely, standard silicon (Std), trap-rich (TR) and high resistivity (HR). All of the mentioned substrates have been fabricated where identical samples of CPW lines have been integrated on. The new PSi substrates have shown successful reduction in the substrate's effective relative permittivity to values as low as 3.7 and great increase in the substrate's effective resistivity to values higher than 7 kΩ cm. As a concept proof, a mm-wave bandpass filter (MBPF) centred at 27 GHz has been integrated on the investigated substrates. Compared with the conventional MBPF implemented on standard silicon-based substrates, the measured S-parameters of the PSi-based MBPF have shown high filtering performance, such as a reduction in insertion loss and an enhancement of the filter selectivity, with the joy of having the same filter performance by varying the temperature. Therefore, the efficiency of the proposed PSi substrates has been well highlighted. From 1994 to 1995, she was assistant of physics at (USTHB), Algiers . From 1998 to 2011, she was a Researcher at characterization laboratory in ionized media and laser division at the Advanced Technologies Development Center. She has integrated the Analog Radio Frequency Integrated Circuits team as Researcher since 2011 until now in Microelectronic and Nanotechnology Division at Advanced Technologies Development Center (CDTA), Algiers. She has been working towards her Ph.D. degree jointly at CDTA and Ecole Nationale Polytechnique, Algiers, since 2012. Her research interest includes fabrication and characterization of microwave passive devices on porous silicon as new substrate, such as characterization of FinFET components.

Mapping the Complex Morphology of Cell Interactions with Nanowire Substrates Using FIB-SEM

PubMed Central

Jensen, Mikkel R. B.; Łopacińska, Joanna; Schmidt, Michael S.; Skolimowski, Maciej; Abeille, Fabien; Qvortrup, Klaus; Mølhave, Kristian

2013-01-01

Using high resolution focused ion beam scanning electron microscopy (FIB-SEM) we study the details of cell-nanostructure interactions using serial block face imaging. 3T3 Fibroblast cellular monolayers are cultured on flat glass as a control surface and on two types of nanostructured scaffold substrates made from silicon black (Nanograss) with low- and high nanowire density. After culturing for 72 hours the cells were fixed, heavy metal stained, embedded in resin, and processed with FIB-SEM block face imaging without removing the substrate. The sample preparation procedure, image acquisition and image post-processing were specifically optimised for cellular monolayers cultured on nanostructured substrates. Cells display a wide range of interactions with the nanostructures depending on the surface morphology, but also greatly varying from one cell to another on the same substrate, illustrating a wide phenotypic variability. Depending on the substrate and cell, we observe that cells could for instance: break the nanowires and engulf them, flatten the nanowires or simply reside on top of them. Given the complexity of interactions, we have categorised our observations and created an overview map. The results demonstrate that detailed nanoscale resolution images are required to begin understanding the wide variety of individual cells’ interactions with a structured substrate. The map will provide a framework for light microscopy studies of such interactions indicating what modes of interactions must be considered. PMID:23326412

Application of optical processing for growth of silicon dioxide

DOEpatents

Sopori, B.L.

1997-06-17

A process for producing a silicon dioxide film on a surface of a silicon substrate is disclosed. The process comprises illuminating a silicon substrate in a substantially pure oxygen atmosphere with a broad spectrum of visible and infrared light at an optical power density of from about 3 watts/cm{sup 2} to about 6 watts/cm{sup 2} for a time period sufficient to produce a silicon dioxide film on the surface of the silicon substrate. An optimum optical power density is about 4 watts/cm{sup 2} for growth of a 100{angstrom}-300{angstrom} film at a resultant temperature of about 400 C. Deep level transient spectroscopy analysis detects no measurable impurities introduced into the silicon substrate during silicon oxide production and shows the interface state density at the SiO{sub 2}/Si interface to be very low. 1 fig.

Recent progress in flexible OLED displays

NASA Astrophysics Data System (ADS)

Hack, Michael G.; Weaver, Michael S.; Mahon, Janice K.; Brown, Julie J.

2001-09-01

Organic light emitting device (OLED) technology has recently been shown to demonstrate excellent performance and cost characteristics for use in numerous flat panel display (FPD) applications. OLED displays emit bright, colorful light with excellent power efficiency, wide viewing angle and video response rates. OLEDs are also demonstrating the requisite environmental robustness for a wide variety of applications. OLED technology is also the first FPD technology with the potential to be highly functional and durable in a flexible format. The use of plastic and other flexible substrate materials offers numerous advantages over commonly used glass substrates, including impact resistance, light weight, thinness and conformability. Currently, OLED displays are being fabricated on rigid substrates, such as glass or silicon wafers. At Universal Display Corporation (UDC), we are developing a new class of flexible OLED displays (FOLEDs). These displays also have extremely low power consumption through the use of electrophosphorescent doped OLEDs. To commercialize FOLED technology, a number of technical issues related to packaging and display processing on flexible substrates need to be addressed. In this paper, we report on our recent results to demonstrate the key technologies that enable the manufacture of power efficient, long-life flexible OLED displays for commercial and military applications.

Preparation of monolayers of [MnIII 6CrIII]3+ single-molecule magnets on HOPG, mica and silicon surfaces and characterization by means of non-contact AFM

NASA Astrophysics Data System (ADS)

Gryzia, Aaron; Predatsch, Hans; Brechling, Armin; Hoeke, Veronika; Krickemeyer, Erich; Derks, Christine; Neumann, Manfred; Glaser, Thorsten; Heinzmann, Ulrich

2011-08-01

We report on the characterization of various salts of [ Mn III 6 Cr III ] 3+ complexes prepared on substrates such as highly oriented pyrolytic graphite (HOPG), mica, SiO2, and Si3N4. [ Mn III 6 Cr III ] 3+ is a single-molecule magnet, i.e., a superparamagnetic molecule, with a blocking temperature around 2 K. The three positive charges of [ Mn III 6 Cr III ] 3+ were electrically neutralized by use of various anions such as tetraphenylborate (BPh4 -), lactate (C3H5O3 -), or perchlorate (ClO4 -). The molecule was prepared on the substrates out of solution using the droplet technique. The main subject of investigation was how the anions and substrates influence the emerging surface topology during and after the preparation. Regarding HOPG and SiO2, flat island-like and hemispheric-shaped structures were created. We observed a strong correlation between the electronic properties of the substrate and the analyzed structures, especially in the case of mica where we observed a gradient in the analyzed structures across the surface.

Planar digital nanoliter dispensing system based on thermocapillary actuation.

PubMed

Darhuber, Anton A; Valentino, Joseph P; Troian, Sandra M

2010-04-21

We provide guidelines for the design and operation of a planar digital nanodispensing system based on thermocapillary actuation. Thin metallic microheaters embedded within a chemically patterned glass substrate are electronically activated to generate and control 2D surface temperature distributions which either arrest or trigger liquid flow and droplet formation on demand. This flow control is a consequence of the variation of a liquid's surface tension with temperature, which is used to draw liquid toward cooler regions of the supporting substrate. A liquid sample consisting of several microliters is placed on a flat rectangular supply cell defined by chemical patterning. Thermocapillary switches are then activated to extract a slender fluid filament from the cell and to divide the filament into an array of droplets whose position and volume are digitally controlled. Experimental results for the power required to extract a filament and to divide it into two or more droplets as a function of geometric and operating parameters are in excellent agreement with hydrodynamic simulations. The capability to dispense ultralow volumes onto a 2D substrate extends the functionality of microfluidic devices based on thermocapillary actuation previously shown effective in routing and mixing nanoliter liquid samples on glass or silicon substrates.

Assembly and evaluation of a pyroelectric detector bonded to vertically aligned multiwalled carbon nanotubes over thin silicon.

PubMed

Theocharous, E; Theocharous, S P; Lehman, J H

2013-11-20

A novel pyroelectric detector consisting of a vertically aligned nanotube array on thin silicon (VANTA/Si) bonded to a 60 μm thick crystal of LiTaO₃ has been fabricated. The performance of the VANTA/Si-coated pyroelectric detector was evaluated using National Physical Laboratory's (NPL's) detector-characterization facilities. The relative spectral responsivity of the detector was found to be spectrally flat in the 0.8-24 μm wavelength range, in agreement with directional-hemispherical reflectance measurements of witness samples of the VANTA. The spatial uniformity of response of the test detector exhibited good uniformity, although the nonuniformity increased with increasing modulation frequency. The nonuniformity may be assigned either to the dimensions of the VANTA or the continuity of the bond between the VANTA/Si coating and the pyroelectric crystal substrate. The test detector exhibited a small superlinear response, which is similar to that of pyroelectric detectors coated with good quality gold-black coatings.

Optimization of imprintable nanostructured a-Si solar cells: FDTD study.

PubMed

Fisker, Christian; Pedersen, Thomas Garm

2013-03-11

We present a finite-difference time-domain (FDTD) study of an amorphous silicon (a-Si) thin film solar cell, with nano scale patterns on the substrate surface. The patterns, based on the geometry of anisotropically etched silicon gratings, are optimized with respect to the period and anti-reflection (AR) coating thickness for maximal absorption in the range of the solar spectrum. The structure is shown to increase the cell efficiency by 10.2% compared to a similar flat solar cell with an optimized AR coating thickness. An increased back reflection can be obtained with a 50 nm zinc oxide layer on the back reflector, which gives an additional efficiency increase, leading to a total of 14.9%. In addition, the patterned cells are shown to be up to 3.8% more efficient than an optimized textured reference cell based on the Asahi U-type glass surface. The effects of variations of the optimized solar cell structure due to the manufacturing process are investigated, and shown to be negligible for variations below ±10%.

Ultra-compact and wide-spectrum-range thermo-optic switch based on silicon coupled photonic crystal microcavities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Xingyu, E-mail: xzhang@utexas.edu, E-mail: swapnajit.chakravarty@omegaoptics.com, E-mail: chenrt@austin.utexas.edu; Chung, Chi-Jui; Pan, Zeyu

2015-11-30

We design, fabricate, and experimentally demonstrate a compact thermo-optic gate switch comprising a 3.78 μm-long coupled L0-type photonic crystal microcavities on a silicon-on-insulator substrate. A nanohole is inserted in the center of each individual L0 photonic crystal microcavity. Coupling between identical microcavities gives rise to bonding and anti-bonding states of the coupled photonic molecules. The coupled photonic crystal microcavities are numerically simulated and experimentally verified with a 6 nm-wide flat-bottom resonance in its transmission spectrum, which enables wider operational spectrum range than microring resonators. An integrated micro-heater is in direct contact with the silicon core to efficiently drive the device. The thermo-opticmore » switch is measured with an optical extinction ratio of 20 dB, an on-off switching power of 18.2 mW, a thermo-optic tuning efficiency of 0.63 nm/mW, a rise time of 14.8 μs, and a fall time of 18.5 μs. The measured on-chip loss on the transmission band is as low as 1 dB.« less

Method for rapid, controllable growth and thickness, of epitaxial silicon films

DOEpatents

Wang, Qi [Littleton, CO; Stradins, Paul [Golden, CO; Teplin, Charles [Boulder, CO; Branz, Howard M [Boulder, CO

2009-10-13

A method of producing epitaxial silicon films on a c-Si wafer substrate using hot wire chemical vapor deposition by controlling the rate of silicon deposition in a temperature range that spans the transition from a monohydride to a hydrogen free silicon surface in a vacuum, to obtain phase-pure epitaxial silicon film of increased thickness is disclosed. The method includes placing a c-Si substrate in a HWCVD reactor chamber. The method also includes supplying a gas containing silicon at a sufficient rate into the reaction chamber to interact with the substrate to deposit a layer containing silicon thereon at a predefined growth rate to obtain phase-pure epitaxial silicon film of increased thickness.

Electrochemical Fabrication of Nanostructures on Porous Silicon for Biochemical Sensing Platforms.

PubMed

Ko, Euna; Hwang, Joonki; Kim, Ji Hye; Lee, Joo Heon; Lee, Sung Hwan; Tran, Van-Khue; Chung, Woo Sung; Park, Chan Ho; Choo, Jaebum; Seong, Gi Hun

2016-01-01

We present a method for the electrochemical patterning of gold nanoparticles (AuNPs) or silver nanoparticles (AgNPs) on porous silicon, and explore their applications in: (1) the quantitative analysis of hydroxylamine as a chemical sensing electrode and (2) as a highly sensitive surface-enhanced Raman spectroscopy (SERS) substrate for Rhodamine 6G. For hydroxylamine detection, AuNPs-porous silicon can enhance the electrochemical oxidation of hydroxylamine. The current changed linearly for concentrations ranging from 100 μM to 1.32 mM (R(2) = 0.995), and the detection limit was determined to be as low as 55 μM. When used as SERS substrates, these materials also showed that nanoparticles decorated on porous silicon substrates have more SERS hot spots than those decorated on crystalline silicon substrates, resulting in a larger SERS signal. Moreover, AgNPs-porous silicon provided five-times higher signal compared to AuNPs-porous silicon. From these results, we expect that nanoparticles decorated on porous silicon substrates can be used in various types of biochemical sensing platforms.

Method of Forming Three-Dimensional Semiconductors Structures

NASA Technical Reports Server (NTRS)

Fathauer, Robert W. (Inventor)

2002-01-01

Silicon and metal are coevaporated onto a silicon substrate in a molecular beam epitaxy system with a larger than stoichiometric amount of silicon so as to epitaxially grow columns of metal silicide embedded in a matrix of single crystal, epitaxially grown silicon. Higher substrate temperatures and lower deposition rates yield larger columns that are farther apart while more silicon produces smaller columns. Column shapes and locations are selected by seeding the substrate with metal silicide starting regions. A variety of 3-dimensional, exemplary electronic devices are disclosed.

Method of bonding silver to glass and mirrors produced according to this method

DOEpatents

Pitts, J.R.; Thomas, T.M.; Czanderna, A.W.

1984-07-31

A method for adhering silver to a glass substrate for producing mirrors includes attaining a silicon enriched substrate surface by reducing the oxygen therein in a vacuum and then vacuum depositing a silver layer onto the silicon enriched surface. The silicon enrichment can be attained by electron beam bombardment, ion beam bombardment, or neutral beam bombardment. It can also be attained by depositing a metal, such as aluminum, on the substrate surface, allowing the metal to oxidize by pulling oxygen from the substrate surface, thereby leaving a silicon enriched surface, and then etching or eroding the metal oxide layer away to expose the silicon enriched surface. Ultraviolet rays can be used to maintain dangling silicon bonds on the enriched surface until covalent bonding with the silver can occur. This disclosure also includes encapsulated mirrors with diffusion layers built therein. One of these mirrors is assembled on a polymer substrate.

Method of bonding silver to glass and mirrors produced according to this method

DOEpatents

Pitts, John R.; Thomas, Terence M.; Czanderna, Alvin W.

1985-01-01

A method for adhering silver to a glass substrate for producing mirrors includes attaining a silicon enriched substrate surface by reducing the oxygen therein in a vacuum and then vacuum depositing a silver layer onto the silicon enriched surface. The silicon enrichment can be attained by electron beam bombardment, ion beam bombardment, or neutral beam bombardment. It can also be attained by depositing a metal, such as aluminum, on the substrate surface, allowing the metal to oxidize by pulling oxygen from the substrate surface, thereby leaving a silicon enriched surface, and then etching or eroding the metal oxide layer away to expose the silicon enriched surface. Ultraviolet rays can be used to maintain dangling silicon bonds on the enriched surface until covalent bonding with the silver can occur. This disclosure also includes encapsulated mirrors with diffusion layers built therein. One of these mirrors is assembled on a polymer substrate.

Investigations of different doping concentration of phosphorus and boron into silicon substrate on the variable temperature Raman characteristics

NASA Astrophysics Data System (ADS)

Li, Xiaoli; Ding, Kai; Liu, Jian; Gao, Junxuan; Zhang, Weifeng

2018-01-01

Different doped silicon substrates have different device applications and have been used to fabricate solar panels and large scale integrated circuits. The thermal transport in silicon substrates are dominated by lattice vibrations, doping type, and doping concentration. In this paper, a variable-temperature Raman spectroscopic system is applied to record the frequency and linewidth changes of the silicon peak at 520 cm-1 in five chips of silicon substrate with different doping concentration of phosphorus and boron at the 83K to 1473K temperature range. The doping has better heat sensitive to temperature on the frequency shift over the low temperature range from 83K to 300K but on FWHM in high temperature range from 300K to 1473K. The results will be helpful for fundamental study and practical applications of silicon substrates.

Effects of patterning induced stress relaxation in strained SOI/SiGe layers and substrate

NASA Astrophysics Data System (ADS)

Hermann, P.; Hecker, M.; Renn, F.; Rölke, M.; Kolanek, K.; Rinderknecht, J.; Eng, L. M.

2011-06-01

Local stress fields in strained silicon structures important for CMOS technology are essentially related to size effects and properties of involved materials. In the present investigation, Raman spectroscopy was utilized to analyze the stress distribution within strained silicon (sSi) and silicon-germanium (SiGe) island structures. As a result of the structuring of initially unpatterned strained films, a size-dependent relaxation of the intrinsic film stresses was obtained in agreement with model calculations. This changed stress state in the features also results in the appearance of opposing stresses in the substrate underneath the islands. Even for strained island structures on top of silicon-on-insulator (SOI) wafers, corresponding stresses in the silicon substrate underneath the oxide were detected. Within structures, the stress relaxation is more pronounced for islands on SOI substrates as compared to those on bulk silicon substrates.

Functionalized ZnO nanowires for microcantilever biosensors with enhanced binding capability.

PubMed

Stassi, Stefano; Chiadò, Alessandro; Cauda, Valentina; Palmara, Gianluca; Canavese, Giancarlo; Laurenti, Marco; Ricciardi, Carlo

2017-04-01

An efficient way to increase the binding capability of microcantilever biosensors is here demonstrated by growing zinc oxide nanowires (ZnO NWs) on their active surface. A comprehensive evaluation of the chemical compatibility of ZnO NWs brought to the definition of an innovative functionalization method able to guarantee the proper immobilization of biomolecules on the nanostructured surface. A noteworthy higher amount of grafted molecules was evidenced with colorimetric assays on ZnO NWs-coated devices, in comparison with functionalized and activated silicon flat samples. ZnO NWs grown on silicon microcantilever arrays and activated with the proposed immobilization strategy enhanced the sensor binding capability (and thus the dynamic range) of nearly 1 order of magnitude, with respect to the commonly employed flat functionalized silicon devices. Graphical Abstract An efficient way to increase the binding capability of microcantilever biosensors is represented by growing zinc oxide nanowires (ZnO NWs) on their active surface. ZnO NWs grown on silicon microcantilever arrays and activated with an innovative immobilization strategy enhanced the sensor binding capability of nearly 1 order of magnitude, with respect to the commonly employed flat functionalized silicon devices.

Fabrication of thermal microphotonic sensors and sensor arrays

DOEpatents

Shaw, Michael J.; Watts, Michael R.; Nielson, Gregory N.

2010-10-26

A thermal microphotonic sensor is fabricated on a silicon substrate by etching an opening and a trench into the substrate, and then filling in the opening and trench with silicon oxide which can be deposited or formed by thermally oxidizing a portion of the silicon substrate surrounding the opening and trench. The silicon oxide forms a support post for an optical resonator which is subsequently formed from a layer of silicon nitride, and also forms a base for an optical waveguide formed from the silicon nitride layer. Part of the silicon substrate can be selectively etched away to elevate the waveguide and resonator. The thermal microphotonic sensor, which is useful to detect infrared radiation via a change in the evanescent coupling of light between the waveguide and resonator, can be formed as a single device or as an array.

Growth evolution of AlN films on silicon (111) substrates by pulsed laser deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Haiyan; Wang, Wenliang; Yang, Weijia

2015-05-14

AlN films with various thicknesses have been grown on Si(111) substrates by pulsed laser deposition (PLD). The surface morphology and structural property of the as-grown AlN films have been investigated carefully to comprehensively explore the epitaxial behavior. The ∼2 nm-thick AlN film initially grown on Si substrate exhibits an atomically flat surface with a root-mean-square surface roughness of 0.23 nm. As the thickness increases, AlN grains gradually grow larger, causing a relatively rough surface. The surface morphology of ∼120 nm-thick AlN film indicates that AlN islands coalesce together and eventually form AlN layers. The decreasing growth rate from 240 to 180 nm/h is amore » direct evidence that the growth mode of AlN films grown on Si substrates by PLD changes from the islands growth to the layer growth. The evolution of AlN films throughout the growth is studied deeply, and its corresponding growth mechanism is hence proposed. These results are instructional for the growth of high-quality nitride films on Si substrates by PLD, and of great interest for the fabrication of AlN-based devices.« less

Improved process for epitaxial deposition of silicon on prediffused substrates

NASA Technical Reports Server (NTRS)

Clarke, M. G.; Halsor, J. L.; Word, J. C.

1968-01-01

Process for fabricating integrated circuits uniformly deposits silicon epitaxially on prediffused substrates without affecting the sublayer diffusion pattern. Two silicon deposits from different sources, and deposited at different temperatures, protect the sublayer pattern from the silicon tetrachloride reaction.

Electrical leakage phenomenon in heteroepitaxial cubic silicon carbide on silicon

NASA Astrophysics Data System (ADS)

Pradeepkumar, Aiswarya; Zielinski, Marcin; Bosi, Matteo; Verzellesi, Giovanni; Gaskill, D. Kurt; Iacopi, Francesca

2018-06-01

Heteroepitaxial 3C-SiC films on silicon substrates are of technological interest as enablers to integrate the excellent electrical, electronic, mechanical, thermal, and epitaxial properties of bulk silicon carbide into well-established silicon technologies. One critical bottleneck of this integration is the establishment of a stable and reliable electronic junction at the heteroepitaxial interface of the n-type SiC with the silicon substrate. We have thus investigated in detail the electrical and transport properties of heteroepitaxial cubic silicon carbide films grown via different methods on low-doped and high-resistivity silicon substrates by using van der Pauw Hall and transfer length measurements as test vehicles. We have found that Si and C intermixing upon or after growth, particularly by the diffusion of carbon into the silicon matrix, creates extensive interstitial carbon traps and hampers the formation of a stable rectifying or insulating junction at the SiC/Si interface. Although a reliable p-n junction may not be realistic in the SiC/Si system, we can achieve, from a point of view of the electrical isolation of in-plane SiC structures, leakage suppression through the substrate by using a high-resistivity silicon substrate coupled with deep recess etching in between the SiC structures.

Gauge Factor and Stretchability of Silicon-on-Polymer Strain Gauges

PubMed Central

Yang, Shixuan; Lu, Nanshu

2013-01-01

Strain gauges are widely applied to measure mechanical deformation of structures and specimens. While metallic foil gauges usually have a gauge factor slightly over 2, single crystalline silicon demonstrates intrinsic gauge factors as high as 200. Although silicon is an intrinsically stiff and brittle material, flexible and even stretchable strain gauges have been achieved by integrating thin silicon strips on soft and deformable polymer substrates. To achieve a fundamental understanding of the large variance in gauge factor and stretchability of reported flexible/stretchable silicon-on-polymer strain gauges, finite element and analytically models are established to reveal the effects of the length of the silicon strip, and the thickness and modulus of the polymer substrate. Analytical results for two limiting cases, i.e., infinitely thick substrate and infinitely long strip, have found good agreement with FEM results. We have discovered that strains in silicon resistor can vary by orders of magnitude with different substrate materials whereas strip length or substrate thickness only affects the strain level mildly. While the average strain in silicon reflects the gauge factor, the maximum strain in silicon governs the stretchability of the system. The tradeoff between gauge factor and stretchability of silicon-on-polymer strain gauges has been proposed and discussed. PMID:23881128

Recent progress in terrestrial photovoltaic collector technology

NASA Technical Reports Server (NTRS)

Ferber, R. R.

1982-01-01

The U.S. Photovoltaic Research and Development Program has the objective to develop the technology necessary to foster widespread grid-competitive electric power generation by the late 1980s. The flat-plate and the concentrator collector activities form the nucleus of the program. The project is concerned with the refining of silicon, silicon sheet production, solar cell processing and fabrication, encapsulation materials development, and collector design and production. The Large-Area Silicon Sheet Task has the objective to develop and demonstrate the feasibility of several methods for producing large area silicon sheet material suitable for fabricating low-cost, high-efficiency solar cells. It is expected that a variety of economic flat-plate and concentrator collectors will become commercially available for grid-connected applications.

Dip-Coating Fabrication of Solar Cells

NASA Technical Reports Server (NTRS)

Koepke, B.; Suave, D.

1982-01-01

Inexpensive silicon solar cells made by simple dip technique. Cooling shoes direct flow of helium on graphite-coated ceramic substrate to solidify film of liquid silicon on graphite surface as substrate is withdrawn from molten silicon. After heaters control cooling of film and substrate to prevent cracking. Gas jets exit at points about 10 mm from substrate surfaces and 6 to 10 mm above melt surface.

Proceedings of the Flat-Plate Solar Array Workshop on the Science of Silicon Material Preparation

NASA Technical Reports Server (NTRS)

1983-01-01

Several areas of silicon material preparation were addressed including silicon production and purity, thermodynamics, kinetics, mechanisms, particle formation and growth, deposition in fluidized bed reactors, and chemical vapor deposition. Twenty-two papers were presented.

Apparatus and method for rapid cooling of large area substrates in vacuum

DOEpatents

Barth, Kurt L.; Enzenroth, Robert A.; Sampath, Walajabad S.

2012-11-06

The present invention is directed to an apparatus and method for rapid cooling of a large substrate in a vacuum environment. A first cooled plate is brought into close proximity with one surface of a flat substrate. The spatial volume between the first cooling plate and the substrate is sealed and brought to a higher pressure than the surrounding vacuum level to increase the cooling efficiency. A second cooled plate is brought into close proximity with the opposite surface of the flat substrate. A second spatial volume between the second cooling plate and the substrate is sealed and the gas pressure is equalized to the gas pressure in the first spatial volume. The equalization of the gas pressure on both sides of the flat substrate eliminates deflection of the substrate and bending stress in the substrate.

Synthesis of Poly-Silicon Thin Films on Glass Substrate Using Laser Initiated Metal Induced Crystallization of Amorphous Silicon for Space Power Application

NASA Technical Reports Server (NTRS)

Abu-Safe, Husam H.; Naseem, Hameed A.; Brown, William D.

2007-01-01

Poly-silicon thin films on glass substrates are synthesized using laser initiated metal induced crystallization of hydrogenated amorphous silicon films. These films can be used to fabricate solar cells on low cost glass and flexible substrates. The process starts by depositing 200 nm amorphous silicon films on the glass substrates. Following this, 200 nm of sputtered aluminum films were deposited on top of the silicon layers. The samples are irradiated with an argon ion cw laser beam for annealing. Laser power densities ranging from 4 to 9 W/cm2 were used in the annealing process. Each area on the sample is irradiated for a different exposure time. Optical microscopy was used to examine any cracks in the films and loss of adhesion to the substrates. X-Ray diffraction patterns from the initial results indicated the crystallization in the films. Scanning electron microscopy shows dendritic growth. The composition analysis of the crystallized films was conducted using Energy Dispersive x-ray Spectroscopy. The results of poly-silicon films synthesis on space qualified flexible substrates such as Kapton are also presented.

Enhanced Raman scattering in porous silicon grating.

PubMed

Wang, Jiajia; Jia, Zhenhong; Lv, Changwu

2018-03-19

The enhancement of Raman signal on monocrystalline silicon gratings with varying groove depths and on porous silicon grating were studied for a highly sensitive surface enhanced Raman scattering (SERS) response. In the experiment conducted, porous silicon gratings were fabricated. Silver nanoparticles (Ag NPs) were then deposited on the porous silicon grating to enhance the Raman signal of the detective objects. Results show that the enhancement of Raman signal on silicon grating improved when groove depth increased. The enhanced performance of Raman signal on porous silicon grating was also further improved. The Rhodamine SERS response based on Ag NPs/ porous silicon grating substrates was enhanced relative to the SERS response on Ag NPs/ porous silicon substrates. Ag NPs / porous silicon grating SERS substrate system achieved a highly sensitive SERS response due to the coupling of various Raman enhancement factors.

Flat-plate solar array project. Volume 2: Silicon material

NASA Technical Reports Server (NTRS)

Lutwack, R.

1986-01-01

The goal of the Silicon Material Task, a part of the Flat Plate Solar Array (FSA) Project, was to develop and demonstate the technology for the low cost production of silicon of suitable purity to be used as the basic material for the manufacture of terrestrial photovoltaic solar cells. Summarized are 11 different processes for the production of silicon that were investigated and developed to varying extent by industrial, university, and Government researchers. The silane production section of the Union Carbide Corp. (UCC) silane process was developed completely in this program. Coupled with Siemens-type chemical vapor deposition reactors, the process was carried through the pilot stage. The overall UCC process involves the conversion of metallurgical-grade silicon to silane followed by decomposition of the silane to purified silicon. The other process developments are described to varying extents. Studies are reported on the effects of impurities in silicon on both silicon-material properties and on solar cell performance. These studies on the effects of impurities yielded extensive information and models for relating specific elemental concentrations to levels of deleterious effects.

Flat-plate solar array project. Volume 2: Silicon material

NASA Astrophysics Data System (ADS)

Lutwack, R.

1986-10-01

The goal of the Silicon Material Task, a part of the Flat Plate Solar Array (FSA) Project, was to develop and demonstate the technology for the low cost production of silicon of suitable purity to be used as the basic material for the manufacture of terrestrial photovoltaic solar cells. Summarized are 11 different processes for the production of silicon that were investigated and developed to varying extent by industrial, university, and Government researchers. The silane production section of the Union Carbide Corp. (UCC) silane process was developed completely in this program. Coupled with Siemens-type chemical vapor deposition reactors, the process was carried through the pilot stage. The overall UCC process involves the conversion of metallurgical-grade silicon to silane followed by decomposition of the silane to purified silicon. The other process developments are described to varying extents. Studies are reported on the effects of impurities in silicon on both silicon-material properties and on solar cell performance. These studies on the effects of impurities yielded extensive information and models for relating specific elemental concentrations to levels of deleterious effects.

Process for Smoothing an Si Substrate after Etching of SiO2

NASA Technical Reports Server (NTRS)

Turner, Tasha; Wu, Chi

2003-01-01

A reactive-ion etching (RIE) process for smoothing a silicon substrate has been devised. The process is especially useful for smoothing those silicon areas that have been exposed by etching a pattern of holes in a layer of silicon dioxide that covers the substrate. Applications in which one could utilize smooth silicon surfaces like those produced by this process include fabrication of optical waveguides, epitaxial deposition of silicon on selected areas of silicon substrates, and preparation of silicon substrates for deposition of adherent metal layers. During etching away of a layer of SiO2 that covers an Si substrate, a polymer becomes deposited on the substrate, and the substrate surface becomes rough (roughness height approximately equal to 50 nm) as a result of over-etching or of deposition of the polymer. While it is possible to smooth a silicon substrate by wet chemical etching, the undesired consequences of wet chemical etching can include compromising the integrity of the SiO2 sidewalls and undercutting of the adjacent areas of the silicon dioxide that are meant to be left intact. The present RIE process results in anisotropic etching that removes the polymer and reduces height of roughness of the silicon substrate to less than 10 nm while leaving the SiO2 sidewalls intact and vertical. Control over substrate versus sidewall etching (in particular, preferential etching of the substrate) is achieved through selection of process parameters, including gas flow, power, and pressure. Such control is not uniformly and repeatably achievable in wet chemical etching. The recipe for the present RIE process is the following: Etch 1 - A mixture of CF4 and O2 gases flowing at rates of 25 to 75 and 75 to 125 standard cubic centimeters per minute (stdcm3/min), respectively; power between 44 and 55 W; and pressure between 45 and 55 mtorr (between 6.0 and 7.3 Pa). The etch rate lies between approximately equal to 3 and approximately equal to 6 nm/minute. Etch 2 - O2 gas flowing at 75 to 125 stdcm3/min, power between 44 and 55 W, and pressure between 50 and 100 mtorr (between 6.7 and 13.3 Pa).

High-Temperature Annealing as a Method for the Silicon Nanoclusters Growth in Stoichiometric Silicon Dioxide

NASA Astrophysics Data System (ADS)

Ivanova, E. V.; Dementev, P. A.; Sitnikova, A. A.; Aleksandrov, O. V.; Zamoryanskaya, M. V.

2018-07-01

A method for the growth of nanocomposite layers in stoichiometric amorphous silicon dioxide is proposed. It is shown that, after annealing at a temperature of 1150°C in nitrogen atmosphere, a layer containing silicon nanoclusters is formed. Silicon nanoclusters have a crystal structure and a size of 3-6 nm. In a film grown on a n-type substrate, a layer of silicon nanoclusters with a thickness of about 10 nm is observed. In the case of a film grown on a p-type substrate, a nanocomposite layer with a thickness of about 100 nm is observed. The difference in the formation of a nanocomposite layer in films on various substrates is associated with the doping of silicon dioxide with impurities from the substrate during the growth of the film. The formation of the nanocomposite layer was confirmed by transmission electron microscopy, XPS and local cathodoluminescence studies.

Selective etching of silicon carbide films

DOEpatents

Gao, Di; Howe, Roger T.; Maboudian, Roya

2006-12-19

A method of etching silicon carbide using a nonmetallic mask layer. The method includes providing a silicon carbide substrate; forming a non-metallic mask layer by applying a layer of material on the substrate; patterning the mask layer to expose underlying areas of the substrate; and etching the underlying areas of the substrate with a plasma at a first rate, while etching the mask layer at a rate lower than the first rate.

Transfer of micro and nano-photonic silicon nanomembrane waveguide devices on flexible substrates.

PubMed

Ghaffari, Afshin; Hosseini, Amir; Xu, Xiaochuan; Kwong, David; Subbaraman, Harish; Chen, Ray T

2010-09-13

This paper demonstrates transfer of optical devices without extra un-patterned silicon onto low-cost, flexible plastic substrates using single-crystal silicon nanomembranes. Employing this transfer technique, stacking two layers of silicon nanomembranes with photonic crystal waveguide in the first layer and multi mode interference couplers in the second layer is shown, respectively. This technique is promising to realize high density integration of multilayer hybrid structures on flexible substrates.

X-ray imaging with amorphous silicon active matrix flat-panel imagers (AMFPIs)

NASA Astrophysics Data System (ADS)

El-Mohri, Youcef; Antonuk, Larry E.; Jee, Kyung-Wook; Maolinbay, Manat; Rong, Xiujiang; Siewerdsen, Jeffrey H.; Verma, Manav; Zhao, Qihua

1997-07-01

Recent advances in thin-film electronics technology have opened the way for the use of flat-panel imagers in a number of medical imaging applications. These novel imagers offer real time digital readout capabilities (˜30 frames per second), radiation hardness (>106cGy), large area (30×40 cm2) and compactness (˜1 cm). Such qualities make them strong candidates for the replacement of conventional x-ray imaging technologies such as film-screen and image intensifier systems. In this report, qualities and potential of amorphous silicon based active matrix flat-panel imagers are outlined for various applications such as radiation therapy, radiography, fluoroscopy and mammography.

Advancements in n-Type Base Crystalline Silicon Solar Cells and Their Emergence in the Photovoltaic Industry

PubMed Central

ur Rehman, Atteq; Lee, Soo Hong

2013-01-01

The p-type crystalline silicon wafers have occupied most of the solar cell market today. However, modules made with n-type crystalline silicon wafers are actually the most efficient modules up to date. This is because the material properties offered by n-type crystalline silicon substrates are suitable for higher efficiencies. Properties such as the absence of boron-oxygen related defects and a greater tolerance to key metal impurities by n-type crystalline silicon substrates are major factors that underline the efficiency of n-type crystalline silicon wafer modules. The bi-facial design of n-type cells with good rear-side electronic and optical properties on an industrial scale can be shaped as well. Furthermore, the development in the industrialization of solar cell designs based on n-type crystalline silicon substrates also highlights its boost in the contributions to the photovoltaic industry. In this paper, a review of various solar cell structures that can be realized on n-type crystalline silicon substrates will be given. Moreover, the current standing of solar cell technology based on n-type substrates and its contribution in photovoltaic industry will also be discussed. PMID:24459433

Advancements in n-type base crystalline silicon solar cells and their emergence in the photovoltaic industry.

PubMed

ur Rehman, Atteq; Lee, Soo Hong

2013-01-01

The p-type crystalline silicon wafers have occupied most of the solar cell market today. However, modules made with n-type crystalline silicon wafers are actually the most efficient modules up to date. This is because the material properties offered by n-type crystalline silicon substrates are suitable for higher efficiencies. Properties such as the absence of boron-oxygen related defects and a greater tolerance to key metal impurities by n-type crystalline silicon substrates are major factors that underline the efficiency of n-type crystalline silicon wafer modules. The bi-facial design of n-type cells with good rear-side electronic and optical properties on an industrial scale can be shaped as well. Furthermore, the development in the industrialization of solar cell designs based on n-type crystalline silicon substrates also highlights its boost in the contributions to the photovoltaic industry. In this paper, a review of various solar cell structures that can be realized on n-type crystalline silicon substrates will be given. Moreover, the current standing of solar cell technology based on n-type substrates and its contribution in photovoltaic industry will also be discussed.

Process for utilizing low-cost graphite substrates for polycrystalline solar cells

NASA Technical Reports Server (NTRS)

Chu, T. L. (Inventor)

1978-01-01

Low cost polycrystalline silicon solar cells supported on substrates were prepared by depositing successive layers of polycrystalline silicon containing appropriate dopants over supporting substrates of a member selected from the group consisting of metallurgical grade polycrystalline silicon, graphite and steel coated with a diffusion barrier of silica, borosilicate, phosphosilicate, or mixtures thereof such that p-n junction devices were formed which effectively convert solar energy to electrical energy. To improve the conversion efficiency of the polycrystalline silicon solar cells, the crystallite size in the silicon was substantially increased by melting and solidifying a base layer of polycrystalline silicon before depositing the layers which form the p-n junction.

Silicon based substrate with calcium aluminosilicate/thermal barrier layer

NASA Technical Reports Server (NTRS)

Eaton, Jr., Harry Edwin (Inventor); Allen, William Patrick (Inventor); Miller, Robert Alden (Inventor); Jacobson, Nathan S. (Inventor); Smialek, James L. (Inventor); Opila, Elizabeth J. (Inventor); Lee, Kang N. (Inventor); Nagaraj, Bangalore A. (Inventor); Wang, Hongyu (Inventor); Meschter, Peter Joel (Inventor)

2001-01-01

A barrier layer for a silicon containing substrate which inhibits the formation of gaseous species of silicon when exposed to a high temperature aqueous environment comprises a calcium alumino silicate.

Silicon based substrate with environmental/thermal barrier layer

NASA Technical Reports Server (NTRS)

Eaton, Jr., Harry Edwin (Inventor); Allen, William Patrick (Inventor); Jacobson, Nathan S. (Inventor); Bansal, Narottam P. (Inventor); Opila, Elizabeth J. (Inventor); Smialek, James L. (Inventor); Lee, Kang N. (Inventor); Spitsberg, Irene T. (Inventor); Wang, Hongyu (Inventor); Meschter, Peter Joel (Inventor)

2002-01-01

A barrier layer for a silicon containing substrate which inhibits the formation of gaseous species of silicon when exposed to a high temperature aqueous environment comprises a barium-strontium alumino silicate.

Silicon based substrate with environmental/ thermal barrier layer

NASA Technical Reports Server (NTRS)

Eaton, Jr., Harry Edwin (Inventor); Allen, William Patrick (Inventor); Jacobson, Nathan S. (Inventor); Bansal, Nanottam P. (Inventor); Opila, Elizabeth J. (Inventor); Smialek, James L. (Inventor); Lee, Kang N. (Inventor); Spitsberg, Irene T. (Inventor); Wang, Hongyu (Inventor); Meschter, Peter Joel (Inventor)

2002-01-01

A barrier layer for a silicon containing substrate which inhibits the formation of gaseous species of silicon when exposed to a high temperature aqueous environment comprises a barium-strontium alumino silicate.

Method for preparing ultraflat, atomically perfect areas on large regions of a crystal surface by heteroepitaxy deposition

DOEpatents

El Gabaly, Farid; Schmid, Andreas K.

2013-03-19

A novel method of forming large atomically flat areas is described in which a crystalline substrate having a stepped surface is exposed to a vapor of another material to deposit a material onto the substrate, which material under appropriate conditions self arranges to form 3D islands across the substrate surface. These islands are atomically flat at their top surface, and conform to the stepped surface of the substrate below at the island-substrate interface. Thereafter, the deposited materials are etched away, in the etch process the atomically flat surface areas of the islands transferred to the underlying substrate. Thereafter the substrate may be cleaned and annealed to remove any remaining unwanted contaminants, and eliminate any residual defects that may have remained in the substrate surface as a result of pre-existing imperfections of the substrate.

PDMS spreading morphological patterns on substrates of different hydrophilicity in air vacuum and water.

PubMed

Zbik, Marek S; Frost, Ray L

2010-04-15

In paper has been to investigate the morphological patterns and kinetics of PDMS spreading on silicon wafer using combination of techniques like ellipsometry, atomic force microscope (AFM), scanning electron microscope (SEM) and optical microscopy. A macroscopic silicone oil drops as well as PDMS water based emulsions were studied after deposition on a flat surface of silicon wafer in air, water and vacuum. Our own measurements using an imaging ellipsometer, which also clearly shows the presence of a precursor film. The diffusion constant of this film, measured with a 60,000 cS PDMS sample spreading on a hydrophilic silicon wafer is D(f)=1.4x10(-11) m(2)/s. Regardless of their size, density and method of deposition, droplets on both types of wafer (hydrophilic and hydrophobic) flatten out over a period of many hours, up to 3 days. During this process neighbouring droplets may coalesce, but there is strong evidence that some of the PDMS from the droplets migrates into a thin, continuous film that covers the surface in between droplets. The thin film appears to be ubiquitous if there has been any deposition of PDMS. However, this statement needs further verification. One question is whether the film forms immediately after forced drying, or whether in some or all cases it only forms by spreading from isolated droplets as they slowly flatten out. 2010 Elsevier Inc. All rights reserved.

Buried oxide layer in silicon

DOEpatents

Sadana, Devendra Kumar; Holland, Orin Wayne

2001-01-01

A process for forming Silicon-On-Insulator is described incorporating the steps of ion implantation of oxygen into a silicon substrate at elevated temperature, ion implanting oxygen at a temperature below 200.degree. C. at a lower dose to form an amorphous silicon layer, and annealing steps to form a mixture of defective single crystal silicon and polycrystalline silicon or polycrystalline silicon alone and then silicon oxide from the amorphous silicon layer to form a continuous silicon oxide layer below the surface of the silicon substrate to provide an isolated superficial layer of silicon. The invention overcomes the problem of buried isolated islands of silicon oxide forming a discontinuous buried oxide layer.

Cascaded Mach-Zehnder wavelength filters in silicon photonics for low loss and flat pass-band WDM (de-)multiplexing.

PubMed

Horst, Folkert; Green, William M J; Assefa, Solomon; Shank, Steven M; Vlasov, Yurii A; Offrein, Bert Jan

2013-05-20

We present 1-to-8 wavelength (de-)multiplexer devices based on a binary tree of cascaded Mach-Zehnder-like lattice filters, and manufactured using a 90 nm CMOS-integrated silicon photonics technology. We demonstrate that these devices combine a flat pass-band over more than 50% of the channel spacing with low insertion loss of less than 1.6 dB, and have a small device size of approximately 500 × 400 µm. This makes this type of filters well suited for application as WDM (de-)multiplexer in silicon photonics transceivers for optical data communication in large scale computer systems.

Silicon based substrate with calcium aluminosilicate environmental/thermal barrier layer

NASA Technical Reports Server (NTRS)

Eaton, Jr., Harry Edwin (Inventor); Allen, William Patrick (Inventor); Miller, Robert Alden (Inventor); Jacobson, Nathan S. (Inventor); Smialek, James L. (Inventor); Opila, Elizabeth J. (Inventor); Lee, Kang N. (Inventor); Nagaraj, Bangalore A. (Inventor); Wang, Hongyu (Inventor); Meschter, Peter Joel (Inventor)

2001-01-01

A barrier layer for a silicon containing substrate which inhibits the formation of gaseous species of silicon when exposed to a high temperature aqueous environment comprises a calcium alumino silicate.

Chemical resistivity of self-assembled monolayer covalently attached to silicon substrate to hydrofluoric acid and ammonium fluoride

NASA Astrophysics Data System (ADS)

Saito, N.; Youda, S.; Hayashi, K.; Sugimura, H.; Takai, O.

2003-06-01

Self-assembled monolayers (SAMs) were prepared on hydrogen-terminated silicon substrates through chemical vapor deposition using 1-hexadecene (HD) as a precursor. The HD-SAMs prepared in an atmosphere under a reduced pressure (≈50 Pa) showed better chemical resistivities to hydrofluoric acid and ammonium fluoride (NH 4F) solutions than that of an organosilane SAM formed on oxide-covered silicon substrates. The surface covered with the HD-SAM was micro-patterned by vacuum ultraviolet photolithography and consequently divided into two areas terminated with HD-SAM or silicon dioxide. This micro-patterned sample was immersed in a 40 vol.% NH 4F aqueous solution. Surface images obtained by an optical microscopy clearly show that the micro-patterns of HD-SAM/silicon dioxide were successfully transferred into the silicon substrate.

Wet-chemical systems and methods for producing black silicon substrates

DOEpatents

Yost, Vernon; Yuan, Hao-Chih; Page, Matthew

2015-05-19

A wet-chemical method of producing a black silicon substrate. The method comprising soaking single crystalline silicon wafers in a predetermined volume of a diluted inorganic compound solution. The substrate is combined with an etchant solution that forms a uniform noble metal nanoparticle induced Black Etch of the silicon wafer, resulting in a nanoparticle that is kinetically stabilized. The method comprising combining with an etchant solution having equal volumes acetonitrile/acetic acid:hydrofluoric acid:hydrogen peroxide.

Feasibility of Actively Cooled Silicon Nitride Airfoil for Turbine Applications Demonstrated

NASA Technical Reports Server (NTRS)

Bhatt, Ramakrishna T.

2001-01-01

Nickel-base superalloys currently limit gas turbine engine performance. Active cooling has extended the temperature range of service of nickel-base superalloys in current gas turbine engines, but the margin for further improvement appears modest. Therefore, significant advancements in materials technology are needed to raise turbine inlet temperatures above 2400 F to increase engine specific thrust and operating efficiency. Because of their low density and high-temperature strength and thermal conductivity, in situ toughened silicon nitride ceramics have received a great deal of attention for cooled structures. However, the high processing costs and low impact resistance of silicon nitride ceramics have proven to be major obstacles for widespread applications. Advanced rapid prototyping technology in combination with conventional gel casting and sintering can reduce high processing costs and may offer an affordable manufacturing approach. Researchers at the NASA Glenn Research Center, in cooperation with a local university and an aerospace company, are developing actively cooled and functionally graded ceramic structures. The objective of this program is to develop cost-effective manufacturing technology and experimental and analytical capabilities for environmentally stable, aerodynamically efficient, foreign-object-damage-resistant, in situ toughened silicon nitride turbine nozzle vanes, and to test these vanes under simulated engine conditions. Starting with computer aided design (CAD) files of an airfoil and a flat plate with internal cooling passages, the permanent and removable mold components for gel casting ceramic slips were made by stereolithography and Sanders machines, respectively. The gel-cast part was dried and sintered to final shape. Several in situ toughened silicon nitride generic airfoils with internal cooling passages have been fabricated. The uncoated and thermal barrier coated airfoils and flat plates were burner rig tested for 30 min without and with air cooling. Without cooling, the surface temperature of the flat plate reached approximately 2350 F. Starting with computer aided design (CAD) files of an airfoil and a flat plate with internal cooling passages, the permanent and removable mold components for gel casting ceramic slips were made by stereolithography and Sanders machines, respectively. The gel-cast part was dried and sintered to final shape. Several in situ toughened silicon nitride generic airfoils with internal cooling passages have been fabricated. The uncoated and thermal barrier coated airfoils and flat plates were burner rig tested for 30 min without and with air cooling. Without cooling, the surface temperature of the flat plate reached approximately 2350 F. With cooling, the surface temperature decreased to approximately 1910 F--a drop of approximately 440 F. This preliminary study demonstrates that a near-net-shape silicon nitride airfoil can be fabricated and that silicon nitride can sustain severe thermal shock and the thermal gradients induced by cooling and, thus, is a viable candidate for cooled components.

Photovoltaic device using single wall carbon nanotubes and method of fabricating the same

DOEpatents

Biris, Alexandru S.; Li, Zhongrui

2012-11-06

A photovoltaic device and methods for forming the same. In one embodiment, the photovoltaic device has a silicon substrate, and a film comprising a plurality of single wall carbon nanotubes disposed on the silicon substrate, wherein the plurality of single wall carbon nanotubes forms a plurality of heterojunctions with the silicon in the substrate.

Surface thiolation of silicon for antifouling application.

PubMed

Zhang, Xiaoning; Gao, Pei; Hollimon, Valerie; Brodus, DaShan; Johnson, Arion; Hu, Hongmei

2018-02-07

Thiol groups grafted silicon surface was prepared as previously described. 1H,1H,2H,2H-perfluorodecanethiol (PFDT) molecules were then immobilized on such a surface through disulfide bonds formation. To investigate the contribution of PFDT coating to antifouling, the adhesion behaviors of Botryococcus braunii (B. braunii) and Escherichia coli (E. coli) were studied through biofouling assays in the laboratory. The representative microscope images suggest reduced B. braunii and E. coli accumulation densities on PFDT integrated silicon substrate. However, the antifouling performance of PFDT integrated silicon substrate decreased over time. By incubating the aged substrate in 10 mM TCEP·HCl solution for 1 h, the fouled PFDT coating could be removed as the disulfide bonds were cleaved, resulting in reduced absorption of algal cells and exposure of non-fouled silicon substrate surface. Our results indicate that the thiol-terminated substrate can be potentially useful for restoring the fouled surface, as well as maximizing the effective usage of the substrate.

Surface modification of silicon wafer by grafting zwitterionic polymers to improve its antifouling property

NASA Astrophysics Data System (ADS)

Sun, Yunlong; Chen, Changlin; Xu, Heng; Lei, Kun; Xu, Guanzhe; Zhao, Li; Lang, Meidong

2017-10-01

Silicon (111) wafer was modified by triethoxyvinylsilane containing double bond as an intermedium, and then P4VP (polymer 4-vinyl pyridine) brush was "grafted" onto the surface of silicon wafer containing reactive double bonds by adopting the "grafting from" way and Si-P4VP substrate (silicon wafer grafted by P4VP) was obtained. Finally, P4VP brush of Si-P4VP substrate was modified by 1,3-propanesulfonate fully to obtain P4VP-psl brush (zwitterionic polypyridinium salt) and the functional Si-P4VP-psl substrate (silicon wafer grafted by zwitterionic polypyridinium salt based on polymer 4-vinyl pyridine) was obtained successfully. The antifouling property of the silicon wafer, the Si-P4VP substrate and the Si-P4VP-psl substrate was investigated by using bovine serum albumin, mononuclear macrophages (RAW 264.7) and Escherichia coli (E. coli) ATTC25922 as model bacterium. The results showed that compared with the blank sample-silicon wafer, the Si-P4VP-psl substrate had excellent anti-adhesion ability against bovine serum albumin, cells and bacterium, due to zwitterionic P4VP-psl brush (polymer 4-vinyl pyridine salt) having special functionality like antifouling ability on biomaterial field.

Ceramic with zircon coating

NASA Technical Reports Server (NTRS)

Wang, Hongyu (Inventor)

2003-01-01

An article comprises a silicon-containing substrate and a zircon coating. The article can comprise a silicon carbide/silicon (SiC/Si) substrate, a zircon (ZrSiO.sub.4) intermediate coating and an external environmental/thermal barrier coating.

Superhydrophobic SERS substrates based on silicon hierarchical nanostructures

NASA Astrophysics Data System (ADS)

Chen, Xuexian; Wen, Jinxiu; Zhou, Jianhua; Zheng, Zebo; An, Di; Wang, Hao; Xie, Weiguang; Zhan, Runze; Xu, Ningsheng; Chen, Jun; She, Juncong; Chen, Huanjun; Deng, Shaozhi

2018-02-01

Silicon nanostructures have been cultivated as promising surface enhanced Raman scattering (SERS) substrates in terms of their low-loss optical resonance modes, facile functionalization, and compatibility with today’s state-of-the-art CMOS techniques. However, unlike their plasmonic counterparts, the electromagnetic field enhancements induced by silicon nanostructures are relatively small, which restrict their SERS sensing limit to around 10-7 M. To tackle this problem, we propose here a strategy for improving the SERS performance of silicon nanostructures by constructing silicon hierarchical nanostructures with a superhydrophobic surface. The hierarchical nanostructures are binary structures consisted of silicon nanowires (NWs) grown on micropyramids (MPs). After being modified with perfluorooctyltriethoxysilane (PFOT), the nanostructure surface shows a stable superhydrophobicity with a high contact angle of ˜160°. The substrate can allow for concentrating diluted analyte solutions into a specific area during the evaporation of the liquid droplet, whereby the analytes are aggregated into a small volume and can be easily detected by the silicon nanostructure SERS substrate. The analyte molecules (methylene blue: MB) enriched from an aqueous solution lower than 10-8 M can be readily detected. Such a detection limit is ˜100-fold lower than the conventional SERS substrates made of silicon nanostructures. Additionally, the detection limit can be further improved by functionalizing gold nanoparticles onto silicon hierarchical nanostructures, whereby the superhydrophobic characteristics and plasmonic field enhancements can be combined synergistically to give a detection limit down to ˜10-11 M. A gold nanoparticle-functionalized superhydrophobic substrate was employed to detect the spiked melamine in liquid milk. The results showed that the detection limit can be as low as 10-5 M, highlighting the potential of the proposed superhydrophobic SERS substrate in practical food safety inspection applications.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wojciechowski, Kenneth; Olsson, Roy; Clews, Peggy J.

Thermally isolated devices may be formed by performing a series of etches on a silicon-based substrate. As a result of the series of etches, silicon material may be removed from underneath a region of an integrated circuit (IC). The removal of the silicon material from underneath the IC forms a gap between remaining substrate and the integrated circuit, though the integrated circuit remains connected to the substrate via a support bar arrangement that suspends the integrated circuit over the substrate. The creation of this gap functions to release the device from the substrate and create a thermally-isolated integrated circuit.

Structural and electrical properties of atomic layer deposited Al-doped ZrO2 films and of the interface with TaN electrode

NASA Astrophysics Data System (ADS)

Spiga, S.; Rao, R.; Lamagna, L.; Wiemer, C.; Congedo, G.; Lamperti, A.; Molle, A.; Fanciulli, M.; Palma, F.; Irrera, F.

2012-07-01

Al-doped ZrO2 (Al-ZrO2) films deposited by atomic layer deposition onto silicon substrates and the interface with the TaN metal gate are investigated. In particular, structural properties of as-grown and annealed films in the 6-26 nm thickness range, as well as leakage and capacitive behavior of metal-oxide-semiconductor stacks are characterized. As-deposited Al-ZrO2 films in the mentioned thickness range are amorphous and crystallize in the ZrO2 cubic phase after thermal treatment at 900 °C. Correspondingly, the dielectric constant (k) value increases from 20 ± 1 to 27 ± 2. The Al-ZrO2 layers exhibit uniform composition through the film thickness and are thermally stable on Si, whereas chemical reactions take place at the TaN/Al-ZrO2 interface. A transient capacitance technique is adopted for monitoring charge trapping and flat band instability at short and long time scales. The role of traps nearby the TaN/Al-ZrO2 interface is discussed and compared with other metal/high-k oxide films. Further, analytical modeling of the flat band voltage shift with a power-law dependence on time allows extracting features of bulk traps close to the silicon/oxide interface, which exhibit energy levels in the 1.4-1.9 eV range above the valence band of the Al-ZrO2.

The Impact of GaN/Substrate Thermal Boundary Resistance on a HEMT Device

DTIC Science & Technology

2011-11-01

stack between the GaN and Substrate layers. The University of Bristol recently reported that this TBR in commercial devices on Silicon Carbide ( SiC ...Circuit RF Radio Frequency PA Power Amplifier SiC Silicon Carbide FEA Finite Element Analysis heff Effective Heat transfer Coefficient (W/m 2 K...substrate material switched from sapphire to silicon , and by another factor of two from silicon to SiC . TABLE 1: SAMPLE RESULTS FROM DOUGLAS ET AL. FOR

Cryogenic High Pressure Sensor Module

NASA Technical Reports Server (NTRS)

Chapman, John J. (Inventor); Shams, Qamar A. (Inventor); Powers, William T. (Inventor)

1999-01-01

A pressure sensor is provided for cryogenic, high pressure applications. A highly doped silicon piezoresistive pressure sensor is bonded to a silicon substrate in an absolute pressure sensing configuration. The absolute pressure sensor is bonded to an aluminum nitride substrate. Aluminum nitride has appropriate coefficient of thermal expansion for use with highly doped silicon at cryogenic temperatures. A group of sensors, either two sensors on two substrates or four sensors on a single substrate are packaged in a pressure vessel.

Cryogenic, Absolute, High Pressure Sensor

NASA Technical Reports Server (NTRS)

Chapman, John J. (Inventor); Shams. Qamar A. (Inventor); Powers, William T. (Inventor)

2001-01-01

A pressure sensor is provided for cryogenic, high pressure applications. A highly doped silicon piezoresistive pressure sensor is bonded to a silicon substrate in an absolute pressure sensing configuration. The absolute pressure sensor is bonded to an aluminum nitride substrate. Aluminum nitride has appropriate coefficient of thermal expansion for use with highly doped silicon at cryogenic temperatures. A group of sensors, either two sensors on two substrates or four sensors on a single substrate are packaged in a pressure vessel.

Compensated amorphous silicon solar cell

DOEpatents

Devaud, Genevieve

1983-01-01

An amorphous silicon solar cell including an electrically conductive substrate, a layer of glow discharge deposited hydrogenated amorphous silicon over said substrate and having regions of differing conductivity with at least one region of intrinsic hydrogenated amorphous silicon. The layer of hydrogenated amorphous silicon has opposed first and second major surfaces where the first major surface contacts the electrically conductive substrate and an electrode for electrically contacting the second major surface. The intrinsic hydrogenated amorphous silicon region is deposited in a glow discharge with an atmosphere which includes not less than about 0.02 atom percent mono-atomic boron. An improved N.I.P. solar cell is disclosed using a BF.sub.3 doped intrinsic layer.

Semiconductor Nanomembrane Tubes: Three-Dimensional Confinement for Controlled Neurite Outgrowth

PubMed Central

Yu, Minrui; Huang, Yu; Ballweg, Jason; Shin, Hyuncheol; Huang, Minghuang; Savage, Donald E.; Lagally, Max G.; Dent, Erik W.; Blick, Robert H.; Williams, Justin C.

2013-01-01

In many neural culture studies, neurite migration on a flat, open surface does not reflect the three-dimensional (3D) microenvironment in vivo. With that in mind, we fabricated arrays of semiconductor tubes using strained silicon (Si) and germanium (Ge) nanomembranes and employed them as a cell culture substrate for primary cortical neurons. Our experiments show that the SiGe substrate and the tube fabrication process are biologically viable for neuron cells. We also observe that neurons are attracted by the tube topography, even in the absence of adhesion factors, and can be guided to pass through the tubes during outgrowth. Coupled with selective seeding of individual neurons close to the tube opening, growth within a tube can be limited to a single axon. Furthermore, the tube feature resembles the natural myelin, both physically and electrically, and it is possible to control the tube diameter to be close to that of an axon, providing a confined 3D contact with the axon membrane and potentially insulating it from the extracellular solution. PMID:21366271

High aspect ratio nano-fabrication of photonic crystal structures on glass wafers using chrome as hard mask.

PubMed

Hossain, Md Nazmul; Justice, John; Lovera, Pierre; McCarthy, Brendan; O'Riordan, Alan; Corbett, Brian

2014-09-05

Wafer-scale nano-fabrication of silicon nitride (Si x N y ) photonic crystal (PhC) structures on glass (quartz) substrates is demonstrated using a thin (30 nm) chromium (Cr) layer as the hard mask for transferring the electron beam lithography (EBL) defined resist patterns. The use of the thin Cr layer not only solves the charging effect during the EBL on the insulating substrate, but also facilitates high aspect ratio PhCs by acting as a hard mask while deep etching into the Si x N y . A very high aspect ratio of 10:1 on a 60 nm wide grating structure has been achieved while preserving the quality of the flat top of the narrow lines. The presented nano-fabrication method provides PhC structures necessary for a high quality optical response. Finally, we fabricated a refractive index based PhC sensor which shows a sensitivity of 185 nm per RIU.

Micromachined silicon electrostatic chuck

DOEpatents

Anderson, R.A.; Seager, C.H.

1996-12-10

An electrostatic chuck is faced with a patterned silicon plate, created by micromachining a silicon wafer, which is attached to a metallic base plate. Direct electrical contact between the chuck face (patterned silicon plate`s surface) and the silicon wafer it is intended to hold is prevented by a pattern of flat-topped silicon dioxide islands that protrude less than 5 micrometers from the otherwise flat surface of the chuck face. The islands may be formed in any shape. Islands may be about 10 micrometers in diameter or width and spaced about 100 micrometers apart. One or more concentric rings formed around the periphery of the area between the chuck face and wafer contain a low-pressure helium thermal-contact gas used to assist heat removal during plasma etching of a silicon wafer held by the chuck. The islands are tall enough and close enough together to prevent silicon-to-silicon electrical contact in the space between the islands, and the islands occupy only a small fraction of the total area of the chuck face, typically 0.5 to 5 percent. The pattern of the islands, together with at least one hole bored through the silicon veneer into the base plate, will provide sufficient gas-flow space to allow the distribution of the helium thermal-contact gas. 6 figs.

RF Sputtering for preparing substantially pure amorphous silicon monohydride

DOEpatents

Jeffrey, Frank R.; Shanks, Howard R.

1982-10-12

A process for controlling the dihydride and monohydride bond densities in hydrogenated amorphous silicon produced by reactive rf sputtering of an amorphous silicon target. There is provided a chamber with an amorphous silicon target and a substrate therein with the substrate and the target positioned such that when rf power is applied to the target the substrate is in contact with the sputtering plasma produced thereby. Hydrogen and argon are fed to the chamber and the pressure is reduced in the chamber to a value sufficient to maintain a sputtering plasma therein, and then rf power is applied to the silicon target to provide a power density in the range of from about 7 watts per square inch to about 22 watts per square inch to sputter an amorphous silicon hydride onto the substrate, the dihydride bond density decreasing with an increase in the rf power density. Substantially pure monohydride films may be produced.

Method of forming buried oxide layers in silicon

DOEpatents

Sadana, Devendra Kumar; Holland, Orin Wayne

2000-01-01

A process for forming Silicon-On-Insulator is described incorporating the steps of ion implantation of oxygen into a silicon substrate at elevated temperature, ion implanting oxygen at a temperature below 200.degree. C. at a lower dose to form an amorphous silicon layer, and annealing steps to form a mixture of defective single crystal silicon and polycrystalline silicon or polycrystalline silicon alone and then silicon oxide from the amorphous silicon layer to form a continuous silicon oxide layer below the surface of the silicon substrate to provide an isolated superficial layer of silicon. The invention overcomes the problem of buried isolated islands of silicon oxide forming a discontinuous buried oxide layer.

Materials Analysis of Transient Plasma-Wall Interactions

DTIC Science & Technology

2014-05-13

such as copper, aluminum, zirconium, titanium, and tungsten) and ceramics (beryllia, aluminum nitride, silicon carbide , etc.). These materials were...formation of silicon carbide . Therefore, a flat Macor disk was polished, and prepared for deuterium exposure by sonicating the sample in both methanol...of silicon constituents whereas the exposed sample clearly shows the addition of carbide and silicon segregation on the surface. 10 AFOSR

Room-temperature bonding of epitaxial layer to carbon-cluster ion-implanted silicon wafers for CMOS image sensors

NASA Astrophysics Data System (ADS)

Koga, Yoshihiro; Kadono, Takeshi; Shigematsu, Satoshi; Hirose, Ryo; Onaka-Masada, Ayumi; Okuyama, Ryousuke; Okuda, Hidehiko; Kurita, Kazunari

2018-06-01

We propose a fabrication process for silicon wafers by combining carbon-cluster ion implantation and room-temperature bonding for advanced CMOS image sensors. These carbon-cluster ions are made of carbon and hydrogen, which can passivate process-induced defects. We demonstrated that this combination process can be used to form an epitaxial layer on a carbon-cluster ion-implanted Czochralski (CZ)-grown silicon substrate with a high dose of 1 × 1016 atoms/cm2. This implantation condition transforms the top-surface region of the CZ-grown silicon substrate into a thin amorphous layer. Thus, an epitaxial layer cannot be grown on this implanted CZ-grown silicon substrate. However, this combination process can be used to form an epitaxial layer on the amorphous layer of this implanted CZ-grown silicon substrate surface. This bonding wafer has strong gettering capability in both the wafer-bonding region and the carbon-cluster ion-implanted projection range. Furthermore, this wafer inhibits oxygen out-diffusion to the epitaxial layer from the CZ-grown silicon substrate after device fabrication. Therefore, we believe that this bonding wafer is effective in decreasing the dark current and white-spot defect density for advanced CMOS image sensors.

Improved Epitaxy and Surface Morphology in YBa2Cu3Oy Thin Films Grown on Double Buffered Si Wafers

NASA Astrophysics Data System (ADS)

Gao, J.; Kang, L.; Wong, H. Y.; Cheung, Y. L.; Yang, J.

Highly epitaxial thin films of YBCO have been obtained on silicon wafers using a Eu2CuO4/YSZ (yttrium-stabilized ZrO2) double buffer. Our results showed that application of such a double buffer can significantly enhance the epitaxy of grown YBCO. It also leads to an excellent surface morphology. The average surface roughness was found less than 5 nm in a large range. The results of X-ray small angle reflection and positron spectroscpy demonstrate a very clear and flat interface between YBCO and buffer layers. The Eu2CuO4/YSZ double buffer could be promising for coating high-TC superconducting films on various reactive substrates.

Silicon ribbon stress/strain workshop

NASA Technical Reports Server (NTRS)

Leipold, M. H.

1985-01-01

Highlights of the Flat Plate Solar Array Project sponsored Silicon Ribbon Stress/Strain Workshop that was held 23 to 24 January 1985 are reported. The presentations and discussions were aimed at acquiring a generic understanding of the sources of stress, deformation, and structural characteristics occurring during the growth of silicon ribbon.

Low temperature deposition of polycrystalline silicon thin films on a flexible polymer substrate by hot wire chemical vapor deposition

NASA Astrophysics Data System (ADS)

Lee, Sang-hoon; Jung, Jae-soo; Lee, Sung-soo; Lee, Sung-bo; Hwang, Nong-moon

2016-11-01

For the applications such as flexible displays and solar cells, the direct deposition of crystalline silicon films on a flexible polymer substrate has been a great issue. Here, we investigated the direct deposition of polycrystalline silicon films on a polyimide film at the substrate temperature of 200 °C. The low temperature deposition of crystalline silicon on a flexible substrate has been successfully made based on two ideas. One is that the Si-Cl-H system has a retrograde solubility of silicon in the gas phase near the substrate temperature. The other is the new concept of non-classical crystallization, where films grow by the building block of nanoparticles formed in the gas phase during hot-wire chemical vapor deposition (HWCVD). The total amount of precipitation of silicon nanoparticles decreased with increasing HCl concentration. By adding HCl, the amount and the size of silicon nanoparticles were reduced remarkably, which is related with the low temperature deposition of silicon films of highly crystalline fraction with a very thin amorphous incubation layer. The dark conductivity of the intrinsic film prepared at the flow rate ratio of RHCl=[HCl]/[SiH4]=3.61 was 1.84×10-6 Scm-1 at room temperature. The Hall mobility of the n-type silicon film prepared at RHCl=3.61 was 5.72 cm2 V-1s-1. These electrical properties of silicon films are high enough and could be used in flexible electric devices.

Surface-micromachined 2D optical scanners with optically flat single-crystalline silicon micromirrors

NASA Astrophysics Data System (ADS)

Su, John G.; Patterson, Pamela R.; Wu, Ming C.

2001-05-01

We have developed a novel wafer-scale single-crystalline silicon micromirror bonding process to fabricate optically flat micromirrors on polysilicon surface-micromachined 2D scanners. The electrostatically actuated 2D scanner has a mirror area of 450 micrometers x 450 micrometers and an optical scan angle of +/- +/-7.5 degree(s). Compared to micromirrors made with a standard polysilicon surface-micromachining process, the radius of curvature of the micromirror has been improved by 1 50 times from 1.8 cm to 265 cm, with surface roughness < 10 nm. Besides, single-crystalline honeycomb micromirrors derived from silicon on insulator (SOI) have been developed to reduce the mass of the bonded mirror.

Visible-blind ultraviolet photodetectors on porous silicon carbide substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Naderi, N.; Hashim, M.R., E-mail: roslan@usm.my

2013-06-01

Highlights: • Highly reliable UV detectors are fabricated on porous silicon carbide substrates. • The optical properties of samples are enhanced by increasing the current density. • The optimized sample exhibits enhanced sensitivity to the incident UV radiation. - Abstract: Highly reliable visible-blind ultraviolet (UV) photodetectors were successfully fabricated on porous silicon carbide (PSC) substrates. High responsivity and high photoconductive gain were observed in a metal–semiconductor–metal ultraviolet photodetector that was fabricated on an optimized PSC substrate. The PSC samples were prepared via the UV-assisted photo-electrochemical etching of an n-type hexagonal silicon carbide (6H-SiC) substrate using different etching current densities. Themore » optical results showed that the current density is an outstanding etching parameter that controls the porosity and uniformity of PSC substrates. A highly porous substrate was synthesized using a suitable etching current density to enhance its light absorption, thereby improving the sensitivity of UV detector with this substrate. The electrical characteristics of fabricated devices on optimized PSC substrates exhibited enhanced sensitivity and responsivity to the incident radiation.« less

Laboratory studies of silicon vapor deposition, phase A. [feasibility of producing thin films for photovoltaic applications

NASA Technical Reports Server (NTRS)

Frost, R. T.; Racette, G. W.; Stockhoff, E. H.

1977-01-01

A system is described capable of carrying out silicon vapor deposition experiments in the low 10 to the minus 10th power torr vacuum range. The system was assembled and tested for use in a program aimed at exploration of vacuum heteroepitaxy of silicon on several substrates of potential interest for photovoltaic applications. An experiment is described in which a silicon layer 2.5 microns thick was deposited on a pyrolytically cleaned tungsten substrate held at a temperature of 400 C. Using a resistance heated silicon source, thicker layers can be deposited in periods of hours by utilizing closer source to substrate distances.

Highly stable, protein resistant thin films on SiC-modified silicon substrates.

PubMed

Qin, Guoting; Zhang, Rui; Makarenko, Boris; Kumar, Amit; Rabalais, Wayne; López Romero, J Manuel; Rico, Rodrigo; Cai, Chengzhi

2010-05-21

Thin films terminated with oligo(ethylene glycol) (OEG) could be photochemically grafted onto ultrathin silicon carbide layers that were generated on silicon substrates via carbonization with acetylene at 820 degrees C. The OEG coating reduced the non-specific adsorption of fibrinogen on the substrates by 99.5% and remained resistant after storage in PBS for 4 weeks at 37 degrees C.

Spalling of a Thin Si Layer by Electrodeposit-Assisted Stripping

NASA Astrophysics Data System (ADS)

Kwon, Youngim; Yang, Changyol; Yoon, Sang-Hwa; Um, Han-Don; Lee, Jung-Ho; Yoo, Bongyoung

2013-11-01

A major goal in solar cell research is to reduce the cost of the final module. Reducing the thickness of the crystalline silicon substrate to several tens of micrometers can reduce material costs. In this work, we describe the electrodeposition of a Ni-P alloy, which induces high stress in the silicon substrate at room temperature. The induced stress enables lift-off of the thin-film silicon substrate. After lift-off of the thin Si film, the mother substrate can be reused, reducing material costs. Moreover, the low-temperature process expected to be improved Si substrate quality.

Forming high efficiency silicon solar cells using density-graded anti-reflection surfaces

DOEpatents

Yuan, Hao-Chih; Branz, Howard M.; Page, Matthew R.

2014-09-09

A method (50) is provided for processing a graded-density AR silicon surface (14) to provide effective surface passivation. The method (50) includes positioning a substrate or wafer (12) with a silicon surface (14) in a reaction or processing chamber (42). The silicon surface (14) has been processed (52) to be an AR surface with a density gradient or region of black silicon. The method (50) continues with heating (54) the chamber (42) to a high temperature for both doping and surface passivation. The method (50) includes forming (58), with a dopant-containing precursor in contact with the silicon surface (14) of the substrate (12), an emitter junction (16) proximate to the silicon surface (14) by doping the substrate (12). The method (50) further includes, while the chamber is maintained at the high or raised temperature, forming (62) a passivation layer (19) on the graded-density silicon anti-reflection surface (14).

Forming high-efficiency silicon solar cells using density-graded anti-reflection surfaces

DOEpatents

Yuan, Hao-Chih; Branz, Howard M.; Page, Matthew R.

2015-07-07

A method (50) is provided for processing a graded-density AR silicon surface (14) to provide effective surface passivation. The method (50) includes positioning a substrate or wafer (12) with a silicon surface (14) in a reaction or processing chamber (42). The silicon surface (14) has been processed (52) to be an AR surface with a density gradient or region of black silicon. The method (50) continues with heating (54) the chamber (42) to a high temperature for both doping and surface passivation. The method (50) includes forming (58), with a dopant-containing precursor in contact with the silicon surface (14) of the substrate (12), an emitter junction (16) proximate to the silicon surface (14) by doping the substrate (12). The method (50) further includes, while the chamber is maintained at the high or raised temperature, forming (62) a passivation layer (19) on the graded-density silicon anti-reflection surface (14).

Buried nanoantenna arrays: versatile antireflection coating.

PubMed

Kabiri, Ali; Girgis, Emad; Capasso, Federico

2013-01-01

Reflection is usually a detrimental phenomenon in many applications such as flat-panel-displays, solar cells, photodetectors, infrared sensors, and lenses. Thus far, to control and suppress the reflection from a substrate, numerous techniques including dielectric interference coatings, surface texturing, adiabatic index matching, and scattering from plasmonic nanoparticles have been investigated. A new technique is demonstrated to manage and suppress reflection from lossless and lossy substrates. It provides a wider flexibility in design versus previous methods. Reflection from a surface can be suppressed over a narrowband, wideband, or multiband frequency range. The antireflection can be dependent or independent of the incident wave polarization. Moreover, antireflection at a very wide incidence angle can be attained. The reflection from a substrate is controlled by a buried nanoantenna array, a structure composed of (1) a subwavelength metallic array and (2) a dielectric cover layer referred to as a superstrate. The material properties and thickness of the superstrate and nanoantennas' geometry and periodicity control the phase and intensity of the wave circulating inside the superstrate cavity. A minimum reflectance of 0.02% is achieved in various experiments in the mid-infrared from a silicon substrate. The design can be integrated in straightforward way in optical devices. The proposed structure is a versatile AR coating to optically impedance matches any substrate to free space in selected any narrow and broadband spectral response across the entire visible and infrared spectrum.

Modeling of the rough spherical nanoparticles manipulation on a substrate based on the AFM nanorobot

NASA Astrophysics Data System (ADS)

Zakeri, M.; Faraji, J.

2014-12-01

In this paper, dynamic behavior of the rough spherical micro/nanoparticles during pulling/pushing on the flat substrate has been investigated and analyzed. For this purpose, at first, two hexagonal roughness models (George and Cooper) were studied and then evaluations for adhesion force were determined for rough particle manipulation on flat substrate. These two models were then changed by using of the Rabinovich theory. Evaluations were determined for contact adhesion force between rough particle and flat substrate; depth of penetration evaluations were determined by the Johnson-Kendall-Roberts contact mechanic theory and the Schwartz method and according to Cooper and George roughness models. Then, the novel contact theory was used to determine a dynamic model for rough micro/nanoparticle manipulation on flat substrate. Finally, simulation of particle dynamic behavior was implemented during pushing of rough spherical gold particles with radii of 50, 150, 400, 600, and 1,000 nm. Results derived from simulations of particles with several rates of roughness on flat substrate indicated that compared to results for flat particles, inherent roughness on particles might reduce the rate of critical force needed for sliding and rolling given particles. Given a fixed radius for roughness value and increased roughness height, evaluations for sliding and rolling critical forces showed greater reduction. Alternately, the rate of critical force was shown to reduce relative to an increased roughness radius. With respect to both models, based on the George roughness model, the predicted rate of adhesion force was greater than that determined in the Cooper roughness model, and as a result, the predicted rate of critical force based on the George roughness model was closer to the critical force value of flat particle.

Growth of carbon nanotubes by Fe-catalyzed chemical vapor processes on silicon-based substrates

NASA Astrophysics Data System (ADS)

Angelucci, Renato; Rizzoli, Rita; Vinciguerra, Vincenzo; Fortuna Bevilacqua, Maria; Guerri, Sergio; Corticelli, Franco; Passini, Mara

2007-03-01

In this paper, a site-selective catalytic chemical vapor deposition synthesis of carbon nanotubes on silicon-based substrates has been developed in order to get horizontally oriented nanotubes for field effect transistors and other electronic devices. Properly micro-fabricated silicon oxide and polysilicon structures have been used as substrates. Iron nanoparticles have been obtained both from a thin Fe film evaporated by e-gun and from iron nitrate solutions accurately dispersed on the substrates. Single-walled nanotubes with diameters as small as 1 nm, bridging polysilicon and silicon dioxide “pillars”, have been grown. The morphology and structure of CNTs have been characterized by SEM, AFM and Raman spectroscopy.

Process for depositing an oxide epitaxially onto a silicon substrate and structures prepared with the process

DOEpatents

McKee, Rodney A.; Walker, Frederick J.

1993-01-01

A process and structure involving a silicon substrate utilizes an ultra high vacuum and molecular beam epitaxy (MBE) methods to grow an epitaxial oxide film upon a surface of the substrate. As the film is grown, the lattice of the compound formed at the silicon interface becomes stabilized, and a base layer comprised of an oxide having a sodium chloride-type lattice structure grows epitaxially upon the compound so as to cover the substrate surface. A perovskite may then be grown epitaxially upon the base layer to render a product which incorporates silicon, with its electronic capabilities, with a perovskite having technologically-significant properties of its own.

Numerical Simulation Of Silicon-Ribbon Growth

NASA Technical Reports Server (NTRS)

Woda, Ben K.; Kuo, Chin-Po; Utku, Senol; Ray, Sujit Kumar

1987-01-01

Mathematical model includes nonlinear effects. In development simulates growth of silicon ribbon from melt. Takes account of entire temperature and stress history of ribbon. Numerical simulations performed with new model helps in search for temperature distribution, pulling speed, and other conditions favoring growth of wide, flat, relatively defect-free silicon ribbons for solar photovoltaic cells at economically attractive, high production rates. Also applicable to materials other than silicon.

Fabrication of polycrystalline solar cells on low-cost substrates

NASA Technical Reports Server (NTRS)

Chu, T. L. (Inventor)

1976-01-01

A new method of producing p-n junction semiconductors for solar cells was described; the principal objective of this investigation is to reduce production costs significantly by depositing polycrystalline silicon on a relatively cheap substrate such as metallurgical-grade silicon, graphite, or steel. The silicon layer contains appropriate dopants, and the substrates are coated with a diffusion barrier of silica, borosilicate, phosphosilicate, or mixtures of these compounds.

Porous Silicon Covered with Silver Nanoparticles as Surface-Enhanced Raman Scattering (SERS) Substrate for Ultra-Low Concentration Detection.

PubMed

Kosović, Marin; Balarin, Maja; Ivanda, Mile; Đerek, Vedran; Marciuš, Marijan; Ristić, Mira; Gamulin, Ozren

2015-12-01

Microporous and macro-mesoporous silicon templates for surface-enhanced Raman scattering (SERS) substrates were produced by anodization of low doped p-type silicon wafers. By immersion plating in AgNO3, the templates were covered with silver metallic film consisting of different silver nanostructures. Scanning electron microscopy (SEM) micrographs of these SERS substrates showed diverse morphology with significant difference in an average size and size distribution of silver nanoparticles. Ultraviolet-visible-near-infrared (UV-Vis-NIR) reflection spectroscopy showed plasmonic absorption at 398 and 469 nm, which is in accordance with the SEM findings. The activity of the SERS substrates was tested using rhodamine 6G (R6G) dye molecules and 514.5 nm laser excitation. Contrary to the microporous silicon template, the SERS substrate prepared from macro-mesoporous silicon template showed significantly broader size distribution of irregular silver nanoparticles as well as localized surface plasmon resonance closer to excitation laser wavelength. Such silver morphology has high SERS sensitivity that enables ultralow concentration detection of R6G dye molecules up to 10(-15) M. To our knowledge, this is the lowest concentration detected of R6G dye molecules on porous silicon-based SERS substrates, which might even indicate possible single molecule detection.

Fabrication of n-type Si nanostructures by direct nanoimprinting with liquid-Si ink

NASA Astrophysics Data System (ADS)

Takagishi, Hideyuki; Masuda, Takashi; Yamazaki, Ken; Shimoda, Tatsuya

2018-01-01

Nanostructures of n-type amorphous silicon (a-Si) and polycrystalline silicon (poly-Si) with a height of 270 nm and line widths of 110-165 nm were fabricated directly onto a substrate through a simple imprinting process that does not require vacuum conditions or photolithography. The n-type Liquid-Si ink was synthesized via photopolymerization of cyclopentasilane (Si5H10) and white phosphorus (P4). By raising the temperature from 160 °C to 200 °C during the nanoimprinting process, well-defined angular patterns were fabricated without any cracking, peeling, or deflections. After the nanoimprinting process, a-Si was produced by heating the nanostructures at 400°C-700 °C, and poly-Si was produced by heating at 800 °C. The dopant P diffuses uniformly in the Si films, and its concentration can be controlled by varying the concentration of P4 in the ink. The specific resistance of the n-type poly-Si pattern was 7.0 × 10-3Ω ṡ cm, which is comparable to the specific resistance of flat n-type poly-Si films.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Astrova, E. V., E-mail: east@mail.ioffe.ru; Rumyantsev, A. M.; Li, G. V.

The anisotropy of lithium intercalation into the silicon anodes of Li-ion batteries is studied on microstructures having the form of a grid with 0.5-μm-thick vertical walls and on silicon wafers of varied orientation. Electrochemical lithiation is performed at room temperature in the galvanostatic mode. The charging curves of the microstructure and flat Si anodes are examined. Secondary-ion mass spectroscopy is used to determine the distribution of intercalated Li atoms across the wafer thickness. The experimental data are analyzed in terms of the two-phase model in which the lithiation process is limited by the propagation velocity of the front between themore » amorphous alloy with a high Li content and the crystalline Si substrate. The relationship between the rates of Li intercalation into different crystallographic planes: (110), (111), and (100), is found to be V{sub 110}: V{sub 111}: V{sub 100} = 3.1: 1.1: 1.0. It is demonstrated that microstructure anodes with (110) walls have the highest cycle life and withstand ~600 cycles when charged and discharged at a rate of 0.36 C.« less

Silicon-on-insulator (SOI) active pixel sensors with the photosite implemented in the substrate

NASA Technical Reports Server (NTRS)

Pain, Bedabrata (Inventor); Zheng, Xinyu (Inventor)

2002-01-01

Active pixel sensors for a high quality imager are fabricated using a silicon-on-insulator (SOI) process by integrating the photodetectors on the SOI substrate and forming pixel readout transistors on the SOI thin-film. The technique can include forming silicon islands on a buried insulator layer disposed on a silicon substrate and selectively etching away the buried insulator layer over a region of the substrate to define a photodetector area. Dopants of a first conductivity type are implanted to form a signal node in the photodetector area and to form simultaneously drain/source regions for a first transistor in at least a first one of the silicon islands. Dopants of a second conductivity type are implanted to form drain/source regions for a second transistor in at least a second one of the silicon islands. Isolation rings around the photodetector also can be formed when dopants of the second conductivity type are implanted. Interconnections among the transistors and the photodetector are provided to allow signals sensed by the photodetector to be read out via the transistors formed on the silicon islands.

Silicon-on-insulator (SOI) active pixel sensors with the photosite implemented in the substrate

NASA Technical Reports Server (NTRS)

Zheng, Xinyu (Inventor); Pain, Bedabrata (Inventor)

2005-01-01

Active pixel sensors for a high quality imager are fabricated using a silicon-on-insulator (SOI) process by integrating the photodetectors on the SOI substrate and forming pixel readout transistors on the SOI thin-film. The technique can include forming silicon islands on a buried insulator layer disposed on a silicon substrate and selectively etching away the buried insulator layer over a region of the substrate to define a photodetector area. Dopants of a first conductivity type are implanted to form a signal node in the photodetector area and to form simultaneously drain/source regions for a first transistor in at least a first one of the silicon islands. Dopants of a second conductivity type are implanted to form drain/source regions for a second transistor in at least a second one of the silicon islands. Isolation rings around the photodetector also can be formed when dopants of the second conductivity type are implanted. Interconnections among the transistors and the photodetector are provided to allow signals sensed by the photodetector to be read out via the transistors formed on the silicon islands.

Increased voltage photovoltaic cell

NASA Technical Reports Server (NTRS)

Ross, B.; Bickler, D. B.; Gallagher, B. D. (Inventor)

1985-01-01

A photovoltaic cell, such as a solar cell, is provided which has a higher output voltage than prior cells. The improved cell includes a substrate of doped silicon, a first layer of silicon disposed on the substrate and having opposite doping, and a second layer of silicon carbide disposed on the first layer. The silicon carbide preferably has the same type of doping as the first layer.

Molybdenum enhanced low-temperature deposition of crystalline silicon nitride

DOEpatents

Lowden, Richard A.

1994-01-01

A process for chemical vapor deposition of crystalline silicon nitride which comprises the steps of: introducing a mixture of a silicon source, a molybdenum source, a nitrogen source, and a hydrogen source into a vessel containing a suitable substrate; and thermally decomposing the mixture to deposit onto the substrate a coating comprising crystalline silicon nitride containing a dispersion of molybdenum silicide.

Micromachined silicon electrostatic chuck

DOEpatents

Anderson, Robert A.; Seager, Carleton H.

1996-01-01

An electrostatic chuck is faced with a patterned silicon plate 11, created y micromachining a silicon wafer, which is attached to a metallic base plate 13. Direct electrical contact between the chuck face 15 (patterned silicon plate's surface) and the silicon wafer 17 it is intended to hold is prevented by a pattern of flat-topped silicon dioxide islands 19 that protrude less than 5 micrometers from the otherwise flat surface of the chuck face 15. The islands 19 may be formed in any shape. Islands may be about 10 micrometers in diameter or width and spaced about 100 micrometers apart. One or more concentric rings formed around the periphery of the area between the chuck face 15 and wafer 17 contain a low-pressure helium thermal-contact gas used to assist heat removal during plasma etching of a silicon wafer held by the chuck. The islands 19 are tall enough and close enough together to prevent silicon-to-silicon electrical contact in the space between the islands, and the islands occupy only a small fraction of the total area of the chuck face 15, typically 0.5 to 5 percent. The pattern of the islands 19, together with at least one hole 12 bored through the silicon veneer into the base plate, will provide sufficient gas-flow space to allow the distribution of the helium thermal-contact gas.

Substrate Topography Induces a Crossover from 2D to 3D Behavior in Fibroblast Migration

PubMed Central

Ghibaudo, Marion; Trichet, Léa; Le Digabel, Jimmy; Richert, Alain; Hersen, Pascal; Ladoux, Benoît

2009-01-01

Abstract In a three-dimensional environment, cells migrate through complex topographical features. Using microstructured substrates, we investigate the role of substrate topography in cell adhesion and migration. To do so, fibroblasts are plated on chemically identical substrates composed of microfabricated pillars. When the dimensions of the pillars (i.e., the diameter, length, and spacing) are varied, migrating cells encounter alternating flat and rough surfaces that depend on the spacing between the pillars. Consequently, we show that substrate topography affects cell shape and migration by modifying cell-to-substrate interactions. Cells on micropillar substrates exhibit more elongated and branched shapes with fewer actin stress fibers compared with cells on flat surfaces. By analyzing the migration paths in various environments, we observe different mechanisms of cell migration, including a persistent type of migration, that depend on the organization of the topographical features. These responses can be attributed to a spatial reorganization of the actin cytoskeleton due to physical constraints and a preferential formation of focal adhesions on the micropillars, with an increased lifetime compared to that observed on flat surfaces. By changing myosin II activity, we show that actomyosin contractility is essential in the cellular response to micron-scale topographic signals. Finally, the analysis of cell movements at the frontier between flat and micropillar substrates shows that cell transmigration through the micropillar substrates depends on the spacing between the pillars. PMID:19580774

Mechanical deformation of carbon nanotube nano-rings on flat substrate

NASA Astrophysics Data System (ADS)

Zheng, Meng; Ke, Changhong

2011-04-01

We present a numerical analysis of the mechanical deformation of carbon nanotube (CNT) nano-rings on flat graphite substrates, which is motivated by our recent experimental findings on the elastic deformation of CNT nano-rings. Our analysis considers a perfectly circular CNT ring formed by bending a straight individual or bundled single-walled nanotube to connect its two ends. The seamless CNT ring is placed vertically on a flat graphite substrate and its respective deformation curvatures under zero external force, compressive, and tensile forces are determined using a continuum model based on nonlinear elastica theory. Our results show that the van der Waals interaction between the CNT ring and the substrate has profound effects on the deformation of the CNT ring, and that the interfacial binding interaction between the CNT ring and the substrate is strongly modulated by the ring deformation. Our results demonstrate that the CNT ring in force-free conditions has a flat ring segment in contact with the substrate if the ring radius R ≥√EI/2Wvdw , in which EI is the flexural rigidity of the nanotube and Wvdw is the per-unit-length van der Waals energy between the flat ring segment and the substrate. Our results reveal that the load-deformation profiles of the CNT ring under tensile loadings exhibit bifurcation behavior, which is ascribed to its van der Waals interaction with the substrate and is dependent on its relaxed conformation on the substrate. Our work suggests that CNT nano-rings are promising for a number of applications, such as ultrasensitive force sensors and stretchable and flexible structural components in nanoscale mechanical and electromechanical systems.

Dislocation-free strained silicon-on-silicon by in-place bonding

NASA Astrophysics Data System (ADS)

Cohen, G. M.; Mooney, P. M.; Paruchuri, V. K.; Hovel, H. J.

2005-06-01

In-place bonding is a technique where silicon-on-insulator (SOI) slabs are bonded by hydrophobic attraction to the underlying silicon substrate when the buried oxide is undercut in dilute HF. The bonding between the exposed surfaces of the SOI slab and the substrate propagates simultaneously with the buried oxide etching. As a result, the slabs maintain their registration and are referred to as "bonded in-place". We report the fabrication of dislocation-free strained silicon slabs from pseudomorphic trilayer Si/SiGe/SOI by in-place bonding. Removal of the buried oxide allows the compressively strained SiGe film to relax elastically and induce tensile strain in the top and bottom silicon films. The slabs remain bonded to the substrate by van der Waals forces when the wafer is dried. Subsequent annealing forms a covalent bond such that when the upper Si and the SiGe layer are removed, the bonded silicon slab remains strained.

Method and apparatus for preparing multiconductor cable with flat conductors

NASA Technical Reports Server (NTRS)

Marcell, G. V. (Inventor)

1969-01-01

A method and apparatus for preparing flat conductor cable having a plurality of ribbon-like conductors disposed upon and adhesively bonded to the surface of a substrate is described. The conductors are brought into contact with the substrate surface, and while maintained in axial tension on said substrate, the combination is seated on a yieldably compressible layer to permit the conductor to become embedded into the surface of the substrate film.

Moving zone Marangoni drying of wet objects using naturally evaporated solvent vapor

DOEpatents

Britten, Jerald A.

1997-01-01

A surface tension gradient driven flow (a Marangoni flow) is used to remove the thin film of water remaining on the surface of an object following rinsing. The process passively introduces by natural evaporation and diffusion of minute amounts of alcohol (or other suitable material) vapor in the immediate vicinity of a continuously refreshed meniscus of deionized water or another aqueous-based, nonsurfactant rinsing agent. Used in conjunction with cleaning, developing or wet etching application, rinsing coupled with Marangoni drying provides a single-step process for 1) cleaning, developing or etching, 2) rinsing, and 3) drying objects such as flat substrates or coatings on flat substrates without necessarily using heat, forced air flow, contact wiping, centrifugation or large amounts of flammable solvents. This process is useful in one-step cleaning and drying of large flat optical substrates, one-step developing/rinsing and drying or etching/rinsing/drying of large flat patterned substrates and flat panel displays during lithographic processing, and room-temperature rinsing/drying of other large parts, sheets or continuous rolls of material.

Moving zone Marangoni drying of wet objects using naturally evaporated solvent vapor

DOEpatents

Britten, J.A.

1997-08-26

A surface tension gradient driven flow (a Marangoni flow) is used to remove the thin film of water remaining on the surface of an object following rinsing. The process passively introduces by natural evaporation and diffusion of minute amounts of alcohol (or other suitable material) vapor in the immediate vicinity of a continuously refreshed meniscus of deionized water or another aqueous-based, nonsurfactant rinsing agent. Used in conjunction with cleaning, developing or wet etching application, rinsing coupled with Marangoni drying provides a single-step process for (1) cleaning, developing or etching, (2) rinsing, and (3) drying objects such as flat substrates or coatings on flat substrates without necessarily using heat, forced air flow, contact wiping, centrifugation or large amounts of flammable solvents. This process is useful in one-step cleaning and drying of large flat optical substrates, one-step developing/rinsing and drying or etching/rinsing/drying of large flat patterned substrates and flat panel displays during lithographic processing, and room-temperature rinsing/drying of other large parts, sheets or continuous rolls of material. 5 figs.

Method of deposition of silicon carbide layers on substrates

DOEpatents

Angelini, P.; DeVore, C.E.; Lackey, W.J.; Blanco, R.E.; Stinton, D.P.

1982-03-19

A method for direct chemical vapor deposition of silicon carbide to substrates, especially nuclear waste particles, is provided by the thermal decomposition of methylsilane at 800 to 1050/sup 0/C when the substrates have been confined within a suitable coating environment.

Evaluation of substrate noise suppression method to mitigate crosstalk among trough-silicon vias

NASA Astrophysics Data System (ADS)

Araga, Yuuki; Kikuchi, Katsuya; Aoyagi, Masahiro

2018-04-01

Substrate noise from a single through-silicon via (TSV) and the noise attenuation by a substrate tap and a guard ring are clarified. A CMOS test vehicle is designed, and 6-µm-diameter TSVs are manufactured on a 20-µm-thick silicon substrate by the via-last method. An on-chip waveform-capturing circuitry is embedded in the test vehicle to capture transient waveforms of substrate noise. The embedded waveform-capturing circuitry demonstrates small and local noise propagation. Experimental results show increased substrate noise level induced by TSVs and the effectiveness of the substrate tap and guard ring for mitigating the crosstalk among TSVs. An analytical model to explain substrate noise propagation is developed to validate experimental results. Results obtained using the substrate model with a multilayer mesh shows good consistency with experimental results, indicating that the model can be used for examination of noise suppression methods.

MEMS Microshutter Array System for James Webb Space Telescope

NASA Technical Reports Server (NTRS)

Li, Mary J.; Adachi, Tomoko; Allen, Christine; Babu, Sachi; Bajikar, Sateesh; Beamesderfer, Michael; Bradley, Ruth; Denis, Kevin; Costen, Nick; Ewin, Audrey;

Molybdenum enhanced low-temperature deposition of crystalline silicon nitride

DOEpatents

Lowden, R.A.

1994-04-05

A process for chemical vapor deposition of crystalline silicon nitride is described which comprises the steps of: introducing a mixture of a silicon source, a molybdenum source, a nitrogen source, and a hydrogen source into a vessel containing a suitable substrate; and thermally decomposing the mixture to deposit onto the substrate a coating comprising crystalline silicon nitride containing a dispersion of molybdenum silicide. 5 figures.

Electron Beam "Writes" Silicon On Sapphire

NASA Technical Reports Server (NTRS)

Heinemann, Klaus

1988-01-01

Method of growing silicon on sapphire substrate uses beam of electrons to aid growth of semiconductor material. Silicon forms as epitaxial film in precisely localized areas in micron-wide lines. Promising fabrication method for fast, densely-packed integrated circuits. Silicon deposited preferentially in contaminated substrate zones and in clean zone irradiated by electron beam. Electron beam, like surface contamination, appears to stimulate decomposition of silane atmosphere.

Ultra-compact, flat-top demultiplexer using anti-reflection contra-directional couplers for CWDM networks on silicon.

PubMed

Shi, Wei; Yun, Han; Lin, Charlie; Greenberg, Mark; Wang, Xu; Wang, Yun; Fard, Sahba Talebi; Flueckiger, Jonas; Jaeger, Nicolas A F; Chrostowski, Lukas

2013-03-25

Wavelength-division-multiplexing (WDM) networks with wide channel grids and bandwidths are promising for low-cost, low-power optical interconnects. Wide-bandwidth, single-band (i.e., no free-spectral range) add-drop filters have been developed on silicon using anti-reflection contra-directional couplers with out-of-phase Bragg gratings. Using such filter components, we demonstrate a 4-channel, coarse-WDM demultiplexer with flat passbands of up to 13 nm and an ultra-compact size of 1.2 × 10(-3) mm(2).

Spectroellipsometric detection of silicon substrate damage caused by radiofrequency sputtering of niobium oxide

NASA Astrophysics Data System (ADS)

Lohner, Tivadar; Serényi, Miklós; Szilágyi, Edit; Zolnai, Zsolt; Czigány, Zsolt; Khánh, Nguyen Quoc; Petrik, Péter; Fried, Miklós

2017-11-01

Substrate surface damage induced by deposition of metal atoms by radiofrequency (rf) sputtering or ion beam sputtering onto single-crystalline silicon (c-Si) surface has been characterized earlier by electrical measurements. The question arises whether it is possible to characterize surface damage using spectroscopic ellipsometry (SE). In our experiments niobium oxide layers were deposited by rf sputtering on c-Si substrates in gas mixture of oxygen and argon. Multiple angle of incidence spectroscopic ellipsometry measurements were performed, a four-layer optical model (surface roughness layer, niobium oxide layer, native silicon oxide layer and ion implantation-amorphized silicon [i-a-Si] layer on a c-Si substrate) was created in order to evaluate the spectra. The evaluations yielded thicknesses of several nm for the i-a-Si layer. Better agreement could be achieved between the measured and the generated spectra by inserting a mixed layer (with components of c-Si and i-a-Si applying the effective medium approximation) between the silicon oxide layer and the c-Si substrate. High depth resolution Rutherford backscattering (RBS) measurements were performed to investigate the interface disorder between the deposited niobium oxide layer and the c-Si substrate. Atomic resolution cross-sectional transmission electron microscopy investigation was applied to visualize the details of the damaged subsurface region of the substrate.

Impact of the silicon substrate resistivity and growth condition on the deep levels in Ni-Au/AlN/Si MIS Capacitors

NASA Astrophysics Data System (ADS)

Wang, Chong; Simoen, Eddy; Zhao, Ming; Li, Wei

2017-10-01

Deep levels formed under different growth conditions of a 200 nm AlN buffer layer on B-doped Czochralski Si(111) substrates with different resistivity were investigated by deep-level transient spectroscopy (DLTS) on metal-insulator-semiconductor capacitors. Growth-temperature-dependent Al diffusion in the Si substrate was derived from the free carrier density obtained by capacitance-voltage measurement on samples grown on p- substrates. The DLTS spectra revealed a high concentration of point and extended defects in the p- and p+ silicon substrates, respectively. This indicated a difference in the electrically active defects in the silicon substrate close to the AlN/Si interface, depending on the B doping concentration.

Formation of multiple levels of porous silicon for buried insulators and conductors in silicon device technologies

DOEpatents

Blewer, Robert S.; Gullinger, Terry R.; Kelly, Michael J.; Tsao, Sylvia S.

1991-01-01

A method of forming a multiple level porous silicon substrate for semiconductor integrated circuits including anodizing non-porous silicon layers of a multi-layer silicon substrate to form multiple levels of porous silicon. At least one porous silicon layer is then oxidized to form an insulating layer and at least one other layer of porous silicon beneath the insulating layer is metallized to form a buried conductive layer. Preferably the insulating layer and conductive layer are separated by an anodization barrier formed of non-porous silicon. By etching through the anodization barrier and subsequently forming a metallized conductive layer, a fully or partially insulated buried conductor may be fabricated under single crystal silicon.

Purified silicon production system

DOEpatents

Wang, Tihu; Ciszek, Theodore F.

2004-03-30

Method and apparatus for producing purified bulk silicon from highly impure metallurgical-grade silicon source material at atmospheric pressure. Method involves: (1) initially reacting iodine and metallurgical-grade silicon to create silicon tetraiodide and impurity iodide byproducts in a cold-wall reactor chamber; (2) isolating silicon tetraiodide from the impurity iodide byproducts and purifying it by distillation in a distillation chamber; and (3) transferring the purified silicon tetraiodide back to the cold-wall reactor chamber, reacting it with additional iodine and metallurgical-grade silicon to produce silicon diiodide and depositing the silicon diiodide onto a substrate within the cold-wall reactor chamber. The two chambers are at atmospheric pressure and the system is open to allow the introduction of additional source material and to remove and replace finished substrates.

Dip coating process: Silicon sheet growth development for the large-area silicon sheet task of the low-cost silicon solar array project

NASA Technical Reports Server (NTRS)

Heaps, J. D.; Maciolek, R. B.; Harrison, W. B.; Wolner, H. A.; Hendrickson, G.; Nelson, L. D.

1976-01-01

To date, an experimental dip-coating facility was constructed. Using this facility, relatively thin (1 mm) mullite and alumina substrates were successfully dip-coated with 2.5 - 3.0 ohm-cm, p-type silicon with areas of approximately 20 sq cm. The thickness and grain size of these coatings are influenced by the temperature of the melt and the rate at which the substrate is pulled from the melt. One mullite substrate had dendrite-like crystallites of the order of 1 mm wide and 1 to 2 cm long. Their axes were aligned along the direction of pulling. A large variety of substrate materials were purchased or developed enabling the program to commence a substrate definition evaluation. Due to the insulating nature of the substrate, the bottom layer of the p-n junction may have to be made via the top surface. The feasibility of accomplishing this was demonstrated using single crystal wafers.

Silicon carbide thyristor

NASA Technical Reports Server (NTRS)

Edmond, John A. (Inventor); Palmour, John W. (Inventor)

1996-01-01

The SiC thyristor has a substrate, an anode, a drift region, a gate, and a cathode. The substrate, the anode, the drift region, the gate, and the cathode are each preferably formed of silicon carbide. The substrate is formed of silicon carbide having one conductivity type and the anode or the cathode, depending on the embodiment, is formed adjacent the substrate and has the same conductivity type as the substrate. A drift region of silicon carbide is formed adjacent the anode or cathode and has an opposite conductivity type as the anode or cathode. A gate is formed adjacent the drift region or the cathode, also depending on the embodiment, and has an opposite conductivity type as the drift region or the cathode. An anode or cathode, again depending on the embodiment, is formed adjacent the gate or drift region and has an opposite conductivity type than the gate.

Bidisperse silica nanoparticles close-packed monolayer on silicon substrate by three step spin method

NASA Astrophysics Data System (ADS)

Khanna, Sakshum; Marathey, Priyanka; Utsav, Chaliawala, Harsh; Mukhopadhyay, Indrajit

2018-05-01

We present the studies on the structural properties of monolayer Bidisperse silica (SiO2) nanoparticles (BDS) on Silicon (Si-100) substrate using spin coating technique. The Bidisperse silica nanoparticle was synthesised by the modified sol-gel process. Nanoparticles on the substrate are generally assembled in non-close/close-packed monolayer (CPM) form. The CPM form is obtained by depositing the colloidal suspension onto the silicon substrate using complex techniques. Here we report an effective method for forming a monolayer of bidisperse silica nanoparticle by three step spin coating technique. The samples were prepared by mixing the monodisperse solutions of different particles size 40 and 100 nm diameters. The bidisperse silica nanoparticles were self-assembled on the silicon substrate forming a close-packed monolayer film. The scanning electron microscope images of bidisperse films provided in-depth film structure of the film. The maximum surface coverage obtained was around 70-80%.

Fabrication of novel plasmonics-active substrates

NASA Astrophysics Data System (ADS)

Dhawan, Anuj; Gerhold, Michael; Du, Yan; Misra, Veena; Vo-Dinh, Tuan

2009-02-01

This paper describes methodologies for fabricating of highly efficient plasmonics-active SERS substrates - having metallic nanowire structures with pointed geometries and sub-5 nm gap between the metallic nanowires enabling concentration of high EM fields in these regions - on a wafer-scale by a reproducible process that is compatible with large-scale development of these substrates. Excitation of surface plasmons in these nanowire structures leads to substantial enhancement in the Raman scattering signal obtained from molecules lying in the vicinity of the nanostructure surface. The methodologies employed included metallic coating of silicon nanowires fabricated by employing deep UV lithography as well as controlled growth of silicon germanium on silicon nanostructures to form diamond-shaped nanowire structures followed by metallic coating. These SERS substrates were employed for detecting chemical and biological molecules of interest. In order to characterize the SERS substrates developed in this work, we obtained SERS signals from molecules such as p-mercaptobenzoic acid (pMBA) and cresyl fast violet (CFV) attached to or adsorbed on the metal-coated SERS substrates. It was observed that both gold-coated triangular shaped nanowire substrates as well as gold-coated diamond shaped nanowire substrates provided very high SERS signals for the nanowires having sub-15 nm gaps and that the SERS signal depends on the closest spacing between the metal-coated silicon and silicon germanium nanowires. SERS substrates developed by the different processes were also employed for detection of biological molecules such as DPA (Dipicolinic Acid), an excellent marker for spores of bacteria such as Anthrax.

Crystalline silicon growth in nickel/a-silicon bilayer

NASA Astrophysics Data System (ADS)

Mohiddon, Md Ahamad; Naidu, K. Lakshun; Dalba, G.; Rocca, F.; Krishna, M. Ghanashyam

2013-02-01

The effect of substrate temperature on amorphous Silicon crystallization, mediated by metal impurity is reported. Bilayers of Ni(200nm)/Si(400nm) are deposited on fused silica substrate by electron beam evaporator at 200 and 500 °C. Raman mapping shows that, 2 to 5 micron size crystalline silicon clusters are distributed over the entire surface of the sample. X-ray diffraction and X-ray absorption spectroscopy studies demonstrate silicon crystallizes over the metal silicide seeds and grow with the annealing temperature.

Solar cell with silicon oxynitride dielectric layer

DOEpatents

Shepherd, Michael; Smith, David D

2015-04-28

Solar cells with silicon oxynitride dielectric layers and methods of forming silicon oxynitride dielectric layers for solar cell fabrication are described. For example, an emitter region of a solar cell includes a portion of a substrate having a back surface opposite a light receiving surface. A silicon oxynitride (SiO.sub.xN.sub.y, 0

Fabrication of heterojunction solar cells by improved tin oxide deposition on insulating layer

DOEpatents

Feng, Tom; Ghosh, Amal K.

1980-01-01

Highly efficient tin oxide-silicon heterojunction solar cells are prepared by heating a silicon substrate, having an insulating layer thereon, to provide a substrate temperature in the range of about 300.degree. C. to about 400.degree. C. and thereafter spraying the so-heated substrate with a solution of tin tetrachloride in a organic ester boiling below about 250.degree. C. Preferably the insulating layer is naturally grown silicon oxide layer.

Methods of repairing a substrate

NASA Technical Reports Server (NTRS)

Riedell, James A. (Inventor); Easler, Timothy E. (Inventor)

2011-01-01

A precursor of a ceramic adhesive suitable for use in a vacuum, thermal, and microgravity environment. The precursor of the ceramic adhesive includes a silicon-based, preceramic polymer and at least one ceramic powder selected from the group consisting of aluminum oxide, aluminum nitride, boron carbide, boron oxide, boron nitride, hafnium boride, hafnium carbide, hafnium oxide, lithium aluminate, molybdenum silicide, niobium carbide, niobium nitride, silicon boride, silicon carbide, silicon oxide, silicon nitride, tin oxide, tantalum boride, tantalum carbide, tantalum oxide, tantalum nitride, titanium boride, titanium carbide, titanium oxide, titanium nitride, yttrium oxide, zirconium boride, zirconium carbide, zirconium oxide, and zirconium silicate. Methods of forming the ceramic adhesive and of repairing a substrate in a vacuum and microgravity environment are also disclosed, as is a substrate repaired with the ceramic adhesive.

Gallium-containing polymer brush film as efficient supported Lewis acid catalyst in a glass microreactor.

PubMed

Munirathinam, Rajesh; Ricciardi, Roberto; Egberink, Richard J M; Huskens, Jurriaan; Holtkamp, Michael; Wormeester, Herbert; Karst, Uwe; Verboom, Willem

2013-01-01

Polystyrene sulfonate polymer brushes, grown on the interior of the microchannels in a microreactor, have been used for the anchoring of gallium as a Lewis acid catalyst. Initially, gallium-containing polymer brushes were grown on a flat silicon oxide surface and were characterized by FTIR, ellipsometry, and X-ray photoelectron spectroscopy (XPS). XPS revealed the presence of one gallium per 2-3 styrene sulfonate groups of the polymer brushes. The catalytic activity of the Lewis acid-functionalized brushes in a microreactor was demonstrated for the dehydration of oximes, using cinnamaldehyde oxime as a model substrate, and for the formation of oxazoles by ring closure of ortho-hydroxy oximes. The catalytic activity of the microreactor could be maintained by periodic reactivation by treatment with GaCl3.

Ultrasmooth Patterned Metals for Plasmonics and Metamaterials

NASA Astrophysics Data System (ADS)

Nagpal, Prashant; Lindquist, Nathan C.; Oh, Sang-Hyun; Norris, David J.

2009-07-01

Surface plasmons are electromagnetic waves that can exist at metal interfaces because of coupling between light and free electrons. Restricted to travel along the interface, these waves can be channeled, concentrated, or otherwise manipulated by surface patterning. However, because surface roughness and other inhomogeneities have so far limited surface-plasmon propagation in real plasmonic devices, simple high-throughput methods are needed to fabricate high-quality patterned metals. We combined template stripping with precisely patterned silicon substrates to obtain ultrasmooth pure metal films with grooves, bumps, pyramids, ridges, and holes. Measured surface-plasmon-propagation lengths on the resulting surfaces approach theoretical values for perfectly flat films. With the use of our method, we demonstrated structures that exhibit Raman scattering enhancements above 107 for sensing applications and multilayer films for optical metamaterials.

Method for deposition of a conductor in integrated circuits

DOEpatents

Creighton, J. Randall; Dominguez, Frank; Johnson, A. Wayne; Omstead, Thomas R.

1997-01-01

A method is described for fabricating integrated semiconductor circuits and, more particularly, for the selective deposition of a conductor onto a substrate employing a chemical vapor deposition process. By way of example, tungsten can be selectively deposited onto a silicon substrate. At the onset of loss of selectivity of deposition of tungsten onto the silicon substrate, the deposition process is interrupted and unwanted tungsten which has deposited on a mask layer with the silicon substrate can be removed employing a halogen etchant. Thereafter, a plurality of deposition/etch back cycles can be carried out to achieve a predetermined thickness of tungsten.

Method of deposition of silicon carbide layers on substrates and product

DOEpatents

Angelini, Peter; DeVore, Charles E.; Lackey, Walter J.; Blanco, Raymond E.; Stinton, David P.

1984-01-01

A method for direct chemical vapor deposition of silicon carbide to substrates, especially nuclear waste particles, is provided by the thermal decomposition of methylsilane at about 800.degree. C. to 1050.degree. C. when the substrates have been confined within a suitable coating environment.

Aligned carbon nanotube-silicon sheets: a novel nano-architecture for flexible lithium ion battery electrodes.

PubMed

Fu, Kun; Yildiz, Ozkan; Bhanushali, Hardik; Wang, Yongxin; Stano, Kelly; Xue, Leigang; Zhang, Xiangwu; Bradford, Philip D

2013-09-25

Aligned carbon nanotube sheets provide an engineered scaffold for the deposition of a silicon active material for lithium ion battery anodes. The sheets are low-density, allowing uniform deposition of silicon thin films while the alignment allows unconstrained volumetric expansion of the silicon, facilitating stable cycling performance. The flat sheet morphology is desirable for battery construction. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Etching process for improving the strength of a laser-machined silicon-based ceramic article

DOEpatents

Copley, Stephen M.; Tao, Hongyi; Todd-Copley, Judith A.

1991-01-01

A process for improving the strength of laser-machined articles formed of a silicon-based ceramic material such as silicon nitride, in which the laser-machined surface is immersed in an etching solution of hydrofluoric acid and nitric acid for a duration sufficient to remove substantially all of a silicon film residue on the surface but insufficient to allow the solution to unduly attack the grain boundaries of the underlying silicon nitride substrate. This effectively removes the silicon film as a source of cracks that otherwise could propagate downwardly into the silicon nitride substrate and significantly reduce its strength.

Etching process for improving the strength of a laser-machined silicon-based ceramic article

DOEpatents

Copley, S.M.; Tao, H.; Todd-Copley, J.A.

1991-06-11

A process is disclosed for improving the strength of laser-machined articles formed of a silicon-based ceramic material such as silicon nitride, in which the laser-machined surface is immersed in an etching solution of hydrofluoric acid and nitric acid for a duration sufficient to remove substantially all of a silicon film residue on the surface but insufficient to allow the solution to unduly attack the grain boundaries of the underlying silicon nitride substrate. This effectively removes the silicon film as a source of cracks that otherwise could propagate downwardly into the silicon nitride substrate and significantly reduce its strength. 1 figure.

Improved toughness of silicon carbide

NASA Technical Reports Server (NTRS)

Palm, J. A.

1976-01-01

Impact energy absorbing layers (EALs) comprised of partially densified silicon carbide were formed in situ on fully sinterable silicon carbide substrates. After final sintering, duplex silicon carbide structures resulted which were comprised of a fully sintered, high density silicon carbide substrate or core, overlayed with an EAL of partially sintered silicon carbide integrally bonded to its core member. Thermal cycling tests proved such structures to be moderately resistant to oxidation and highly resistant to thermal shock stresses. The strength of the developed structures in some cases exceeded but essentially it remained the same as the fully sintered silicon carbide without the EAL. Ballistic impact tests indicated that substantial improvements in the toughness of sintered silicon carbide were achieved by the use of the partially densified silicon carbide EALs.

Dip coating process: Silicon sheet growth development for the large-area silicon sheet task of the low-cost silicon solar array project

NASA Technical Reports Server (NTRS)

Heaps, J. D.; Maciolek, R. B.; Zook, J. D.; Harrison, W. B.; Scott, M. W.; Hendrickson, G.; Wolner, H. A.; Nelson, L. D.; Schuller, T. L.; Peterson, A. A.

1976-01-01

The technical and economic feasibility of producing solar cell quality sheet silicon by dip-coating one surface of carbonized ceramic substrates with a thin layer of large grain polycrystalline silicon was investigated. The dip-coating methods studied were directed toward a minimum cost process with the ultimate objective of producing solar cells with a conversion efficiency of 10% or greater. The technique shows excellent promise for low cost, labor-saving, scale-up potentialities and would provide an end product of sheet silicon with a rigid and strong supportive backing. An experimental dip-coating facility was designed and constructed, several substrates were successfully dip-coated with areas as large as 25 sq cm and thicknesses of 12 micron to 250 micron. There appears to be no serious limitation on the area of a substrate that could be coated. Of the various substrate materials dip-coated, mullite appears to best satisfy the requirement of the program. An inexpensive process was developed for producing mullite in the desired geometry.

Interaction of a single acetophenone molecule with group III-IV elements mediated by Si(001)

NASA Astrophysics Data System (ADS)

Racis, A.; Jurczyszyn, L.; Radny, M. W.

2018-03-01

A theoretical study of an influence of the acetophenone molecule adsorbed on the Si(001) on the local chemical reactivity of silicon surface is presented. The obtained results indicate that the interaction of the molecule with silicon substrate breaks the intra-dimer π bonds in four surface silicon dimers interacting directly with adsorbed molecule. This leads to the formation of two pairs of unpaired dangling bonds at two opposite sides of the molecule. It is demonstrated that these dangling bonds increase considerably the local chemical reactivity of the silicon substrate in the vicinity of the adsorbed molecule. Consequently, it is shown that such molecule bonded with Si(001) can stabilize the position of In and Pb adatoms diffusing on silicon substrate at two sides and initiate the one-dimensional aggregation of the metallic adatoms on the Si(001) substrate anchored at both sides of the adsorbed molecule. This type of aggregation leads to the growth of chain-like atomic structures in opposite directions, pinned to adsorbed molecule and oriented perpendicular to the rows of surface silicon dimers.

Low-Power RIE of SiO2 in CHF3 To Obtain Steep Sidewalls

NASA Technical Reports Server (NTRS)

Turner, Tasha; Wu, Chi

2003-01-01

A reactive-ion etching (RIE) process has been developed to enable the formation of holes with steep sidewalls in a layer of silicon dioxide that covers a silicon substrate. The holes in question are through the thickness of the SiO2 and are used to define silicon substrate areas to be etched or to be built upon through epitaxial deposition of silicon. The sidewalls of these holes are required to be vertical in order to ensure that the sidewalls of the holes to be etched in the substrate or the sidewalls of the epitaxial deposits, respectively, also turn out to be vertical.

Transistors using crystalline silicon devices on glass

DOEpatents

McCarthy, Anthony M.

1995-01-01

A method for fabricating transistors using single-crystal silicon devices on glass. This method overcomes the potential damage that may be caused to the device during high voltage bonding and employs a metal layer which may be incorporated as part of the transistor. This is accomplished such that when the bonding of the silicon wafer or substrate to the glass substrate is performed, the voltage and current pass through areas where transistors will not be fabricated. After removal of the silicon substrate, further metal may be deposited to form electrical contact or add functionality to the devices. By this method both single and gate-all-around devices may be formed.

Purification and deposition of silicon by an iodide disproportionation reaction

DOEpatents

Wang, Tihu; Ciszek, Theodore F.

2002-01-01

Method and apparatus for producing purified bulk silicon from highly impure metallurgical-grade silicon source material at atmospheric pressure. Method involves: (1) initially reacting iodine and metallurgical-grade silicon to create silicon tetraiodide and impurity iodide byproducts in a cold-wall reactor chamber; (2) isolating silicon tetraiodide from the impurity iodide byproducts and purifying it by distillation in a distillation chamber; and (3) transferring the purified silicon tetraiodide back to the cold-wall reactor chamber, reacting it with additional iodine and metallurgical-grade silicon to produce silicon diiodide and depositing the silicon diiodide onto a substrate within the cold-wall reactor chamber. The two chambers are at atmospheric pressure and the system is open to allow the introduction of additional source material and to remove and replace finished substrates.

Composition Comprising Silicon Carbide

NASA Technical Reports Server (NTRS)

Mehregany, Mehran (Inventor); Zorman, Christian A. (Inventor); Fu, Xiao-An (Inventor); Dunning, Jeremy L. (Inventor)

2012-01-01

A method of depositing a ceramic film, particularly a silicon carbide film, on a substrate is disclosed in which the residual stress, residual stress gradient, and resistivity are controlled. Also disclosed are substrates having a deposited film with these controlled properties and devices, particularly MEMS and NEMS devices, having substrates with films having these properties.

Method and apparatus for forming conformal SiN.sub.x films

DOEpatents

Wang, Qi

2007-11-27

A silicon nitride film formation method includes: Heating a substrate to be subjected to film formation to a substrate temperature; heating a wire to a wire temperature; supplying silane, ammonia, and hydrogen gases to the heating member; and forming a silicon nitride film on the substrate.

Silicon heterojunction solar cells with novel fluorinated n-type nanocrystalline silicon oxide emitters on p-type crystalline silicon

NASA Astrophysics Data System (ADS)

Dhar, Sukanta; Mandal, Sourav; Das, Gourab; Mukhopadhyay, Sumita; Pratim Ray, Partha; Banerjee, Chandan; Barua, Asok Kumar

2015-08-01

A novel fluorinated phosphorus doped silicon oxide based nanocrystalline material have been used to prepare heterojunction solar cells on flat p-type crystalline silicon (c-Si) Czochralski (CZ) wafers. The n-type nc-SiO:F:H material were deposited by radio frequency plasma enhanced chemical vapor deposition. Deposited films were characterized in detail by using atomic force microscopy (AFM), high resolution transmission electron microscopy (HRTEM), Raman, fourier transform infrared spectroscopy (FTIR) and optoelectronics properties have been studied using temperature dependent conductivity measurement, Ellipsometry, UV-vis spectrum analysis etc. It is observed that the cell fabricated with fluorinated silicon oxide emitter showing higher initial efficiency (η = 15.64%, Jsc = 32.10 mA/cm2, Voc = 0.630 V, FF = 0.77) for 1 cm2 cell area compare to conventional n-a-Si:H emitter (14.73%) on flat c-Si wafer. These results indicate that n type nc-SiO:F:H material is a promising candidate for heterojunction solar cell on p-type crystalline wafers. The high Jsc value is associated with excellent quantum efficiencies at short wavelengths (<500 nm).

Potential of thin-film solar cell module technology

NASA Technical Reports Server (NTRS)

Shimada, K.; Ferber, R. R.; Costogue, E. N.

1985-01-01

During the past five years, thin-film cell technology has made remarkable progress as a potential alternative to crystalline silicon cell technology. The efficiency of a single-junction thin-film cell, which is the most promising for use in flat-plate modules, is now in the range of 11 percent with 1-sq cm cells consisting of amorphous silicon, CuInSe2 or CdTe materials. Cell efficiencies higher than 18 percent, suitable for 15 percent-efficient flat plate modules, would require a multijunction configuration such as the CdTe/CuInSe2 and tandem amorphous-silicon (a-Si) alloy cells. Assessments are presented of the technology status of thin-film-cell module research and the potential of achieving the higher efficiencies required for large-scale penetration into the photovoltaic (PV) energy market.

MEMS Applications in Aerodynamic Measurement Technology

NASA Technical Reports Server (NTRS)

Reshotko, E.; Mehregany, M.; Bang, C.

1998-01-01

Microelectromechanical systems (MEMS) embodies the integration of sensors, actuators, and electronics on a single substrate using integrated circuit fabrication techniques and compatible bulk and surface micromachining processes. Silicon and its derivatives form the material base for the MEMS technology. MEMS devices, including microsensors and microactuators, are attractive because they can be made small (characteristic dimension about 100 microns), be produced in large numbers with uniform performance, include electronics for high performance and sophisticated functionality, and be inexpensive. For aerodynamic measurements, it is preferred that sensors be small so as to approximate measurement at a point, and in fact, MEMS pressure sensors, wall shear-stress sensors, heat flux sensors and micromachined hot wires are nearing application. For the envisioned application to wind tunnel models, MEMS sensors can be placed on the surface or in very shallow grooves. MEMS devices have often been fabricated on stiff, flat silicon substrates, about 0.5 mm thick, and therefore were not easily mounted on curved surfaces. However, flexible substrates are now available and heat-flux sensor arrays have been wrapped around a curved turbine blade. Electrical leads can also be built into the flexible substrate. Thus MEMS instrumented wind tunnel models do not require deep spanwise grooves for tubes and leads that compromise the strength of conventionally instrumented models. With MEMS, even the electrical leads can potentially be eliminated if telemetry of the signals to an appropriate receiver can be implemented. While semiconductor silicon is well known for its electronic properties, it is also an excellent mechanical material for MEMS applications. However, silicon electronics are limited to operations below about 200 C, and silicon's mechanical properties start to diminish above 400 C. In recent years, silicon carbide (SiC) has emerged as the leading material candidate for applications in high temperature environments and can be used for high-temperature MEMS applications. With SiC, diodes and more complex electronics have been shown to operate to about 600 C, while the mechanical properties of SiC are maintained to much higher temperatures. Even when MEMS devices show benefits in the laboratory, there are many packaging challenges for any aeronautics application. Incorporating MEMS into these applications requires new approaches to packaging that goes beyond traditional integrated circuit (IC) packaging technologies. MEMS must interact mechanically, as well as electrically with their environment, making most traditional chip packaging and mounting techniques inadequate. Wind tunnels operate over wide temperature ranges in an environment that is far from being a 'clean-room.' In flight, aircraft are exposed to natural elements (e.g. rain, sun, ice, insects and dirt) and operational interferences(e.g. cleaning and deicing fluids, and maintenance crews). In propulsion systems applications, MEMS devices will have to operate in environments containing gases with very high temperatures, abrasive particles and combustion products. Hence deployment and packaging that maintains the integrity of the MEMS system is crucial. This paper presents an overview of MEMS fabrication and materials, descriptions of available sensors with more details on those being developed in our laboratories, and a discussion of sensor deployment options for wind tunnel and flight applications.

Silicon on Ceramic Process: Silicon Sheet Growth and Device Development for the Large-area Silicon Sheet and Cell Development Tasks of the Low-cost Solar Array Project

NASA Technical Reports Server (NTRS)

Chapman, P. W.; Zook, J. D.; Heaps, J. D.; Pickering, C.; Grung, B. L.; Koepke, B.; Schuldt, S. B.

1979-01-01

The technical and economic feasibility of producing solar cell quality sheet silicon was investigated. It was hoped this could be done by coating one surface of carbonized ceramic substrates with a thin layer of large-grain polycrystalline silicon from the melt. Work was directed towards the solution of unique cell processing/design problems encountered with the silicon-ceramic (SOC) material due to its intimate contact with the ceramic substrate. Significant progress was demonstrated in the following areas; (1) the continuous coater succeeded in producing small-area coatings exhibiting unidirectional solidification and substatial grain size; (2) dip coater succeeded in producing thick (more than 500 micron) dendritic layers at coating speeds of 0.2-0.3 cm/sec; and (3) a standard for producing total area SOC solar cells using slotted ceramic substrates was developed.

Method for forming silicon on a glass substrate

DOEpatents

McCarthy, Anthony M.

1995-01-01

A method by which single-crystal silicon microelectronics may be fabricated on glass substrates at unconventionally low temperatures. This is achieved by fabricating a thin film of silicon on glass and subsequently forming the doped components by a short wavelength (excimer) laser doping procedure and conventional patterning techniques. This method may include introducing a heavily boron doped etch stop layer on a silicon wafer using an excimer laser, which permits good control of the etch stop layer removal process. This method additionally includes dramatically reducing the remaining surface roughness of the silicon thin films after etching in the fabrication of silicon on insulator wafers by scanning an excimer laser across the surface of the silicon thin film causing surface melting, whereby the surface tension of the melt causes smoothing of the surface during recrystallization. Applications for this method include those requiring a transparent or insulating substrate, such as display manufacturing. Other applications include sensors, actuators, optoelectronics, radiation hard and high temperature electronics.

Method for forming silicon on a glass substrate

DOEpatents

McCarthy, A.M.

1995-03-07

A method by which single-crystal silicon microelectronics may be fabricated on glass substrates at unconventionally low temperatures. This is achieved by fabricating a thin film of silicon on glass and subsequently forming the doped components by a short wavelength (excimer) laser doping procedure and conventional patterning techniques. This method may include introducing a heavily boron doped etch stop layer on a silicon wafer using an excimer laser, which permits good control of the etch stop layer removal process. This method additionally includes dramatically reducing the remaining surface roughness of the silicon thin films after etching in the fabrication of silicon on insulator wafers by scanning an excimer laser across the surface of the silicon thin film causing surface melting, whereby the surface tension of the melt causes smoothing of the surface during recrystallization. Applications for this method include those requiring a transparent or insulating substrate, such as display manufacturing. Other applications include sensors, actuators, optoelectronics, radiation hard and high temperature electronics. 15 figs.

Polycrystalline silicon on tungsten substrates

NASA Technical Reports Server (NTRS)

Bevolo, A. J.; Schmidt, F. A.; Shanks, H. R.; Campisi, G. J.

1979-01-01

Thin films of electron-beam-vaporized silicon were deposited on fine-grained tungsten substrates under a pressure of about 1 x 10 to the -10th torr. Mass spectra from a quadrupole residual-gas analyzer were used to determine the partial pressure of 13 residual gases during each processing step. During separate silicon depositions, the atomically clean substrates were maintained at various temperatures between 400 and 780 C, and deposition rates were between 20 and 630 A min. Surface contamination and interdiffusion were monitored by in situ Auger electron spectrometry before and after cleaning, deposition, and annealing. Auger depth profiling, X-ray analysis, and SEM in the topographic and channeling modes were utilized to characterize the samples with respect to silicon-metal interface, interdiffusion, silicide formation, and grain size of silicon. The onset of silicide formation was found to occur at approximately 625 C. Above this temperature tungsten silicides were formed at a rate faster than the silicon deposition. Fine-grain silicon films were obtained at lower temperatures.

Surface Attachment of Gold Nanoparticles Guided by Block Copolymer Micellar Films and Its Application in Silicon Etching

PubMed Central

Wei, Mingjie; Wang, Yong

2015-01-01

Patterning metallic nanoparticles on substrate surfaces is important in a number of applications. However, it remains challenging to fabricate such patterned nanoparticles with easily controlled structural parameters, including particle sizes and densities, from simple methods. We report on a new route to directly pattern pre-formed gold nanoparticles with different diameters on block copolymer micellar monolayers coated on silicon substrates. Due to the synergetic effect of complexation and electrostatic interactions between the micellar cores and the gold particles, incubating the copolymer-coated silicon in a gold nanoparticles suspension leads to a monolayer of gold particles attached on the coated silicon. The intermediate micellar film was then removed using oxygen plasma treatment, allowing the direct contact of the gold particles with the Si substrate. We further demonstrate that the gold nanoparticles can serve as catalysts for the localized etching of the silicon substrate, resulting in nanoporous Si with a top layer of straight pores. PMID:28793407

RF sputtering for controlling dihydride and monohydride bond densities in amorphous silicon hydride

DOEpatents

Jeffery, F.R.; Shanks, H.R.

1980-08-26

A process is described for controlling the dihydride and monohydride bond densities in hydrogenated amorphous silicone produced by reactive rf sputtering of an amorphous silicon target. There is provided a chamber with an amorphous silicon target and a substrate therein with the substrate and the target positioned such that when rf power is applied to the target the substrate is in contact with the sputtering plasma produced thereby. Hydrogen and argon are fed to the chamber and the pressure is reduced in the chamber to a value sufficient to maintain a sputtering plasma therein, and then rf power is applied to the silicon target to provide a power density in the range of from about 7 watts per square inch to about 22 watts per square inch to sputter an amorphous solicone hydride onto the substrate, the dihydride bond density decreasing with an increase in the rf power density. Substantially pure monohydride films may be produced.

Selectively Plasmon-Enhanced Second-Harmonic Generation from Monolayer Tungsten Diselenide on Flexible Substrates.

PubMed

Wang, Zhuo; Dong, Zhaogang; Zhu, Hai; Jin, Lei; Chiu, Ming-Hui; Li, Lain-Jong; Xu, Qing-Hua; Eda, Goki; Maier, Stefan A; Wee, Andrew T S; Qiu, Cheng-Wei; Yang, Joel K W

2018-02-27

Monolayer two-dimensional transition-metal dichalcogenides (2D TMDCs) exhibit promising characteristics in miniaturized nonlinear optical frequency converters, due to their inversion asymmetry and large second-order nonlinear susceptibility. However, these materials usually have very short light interaction lengths with the pump laser because they are atomically thin, such that second-harmonic generation (SHG) is generally inefficient. In this paper, we fabricate a judiciously structured 150 nm-thick planar surface consisting of monolayer tungsten diselenide and sub-20 nm-wide gold trenches on flexible substrates, reporting ∼7000-fold SHG enhancement without peak broadening or background in the spectra as compared to WSe 2 on as-grown sapphire substrates. Our proof-of-concept experiment yields effective second-order nonlinear susceptibility of 2.1 × 10 4 pm/V. Three orders of magnitude enhancement is maintained with pump wavelength ranging from 800 to 900 nm, breaking the limitation of narrow pump wavelength range for cavity-enhanced SHG. In addition, SHG amplitude can be dynamically controlled via selective excitation of the lateral gap plasmon by rotating the laser polarization. Such a fully open, flat, and ultrathin profile enables a great variety of functional samples with high SHG from one patterned silicon substrate, favoring scalable production of nonlinear converters. The surface accessibility also enables integration with other optical components for information processing in an ultrathin and flexible form.

SOI-silicon as structural layer for NEMS applications

NASA Astrophysics Data System (ADS)

Villarroya, Maria; Figueras, Eduard; Perez-Murano, Francesc; Campabadal, Francesca; Esteve, Jaume; Barniol, Nuria

2003-04-01

The objective of this paper is to present the compatibilization between a standard CMOS on bulk silicon process and the fabrication of nanoelectromechanical systems using Silicon On Insulator (SOI) wafers as substrate. This compatibilization is required as first step to fabricate a very high sensitive mass sensor based on a resonant cantilever with nanometer dimensions using the crystal silicon COI layer as the structural layer. The cantilever is driven electrostatically to its resonance frequency by an electrode placed parallel to the cantilever. A capacitive readout is performed. To achieve very high resolution, very small dimensions of the cantilever (nanometer range) are needed. For this reason, the control and excitation circuitry has to be integrated on the same substrate than the cantilever. Prior to the development of this sensor, it is necessary to develop a substrate able to be used first to integrate a standard CMOS circuit and afterwards to fabricate the nano-resonator. Starting from a SOI wafer and using very simple processes, the SOI silicon layer is removed, except from the areas in which nano-structures will be fabricated; obtaining a silicon substrate with islands with a SOI structure. The CMOS circuitry will be integrated on the bulk silicon region, while the remainder SOI region will be used for the nanoresonator. The silicon oxide of this SOI region is used as insulator; and as sacrificial layer, etched to release the cantilever from the substrate. To assure the cover of the different CMOS layers over the step of the islands, it is essential to avoid very sharp steps.

Method of forming contacts for a back-contact solar cell

DOEpatents

Manning, Jane

2015-10-20

Methods of forming contacts for solar cells are described. In one embodiment, a method includes forming a silicon layer above a substrate, forming and patterning a solid-state p-type dopant source on the silicon layer, forming an n-type dopant source layer over exposed regions of the silicon layer and over a plurality of regions of the solid-state p-type dopant source, and heating the substrate to provide a plurality of n-type doped silicon regions among a plurality of p-type doped silicon regions.

Method of forming contacts for a back-contact solar cell

DOEpatents

Manning, Jane

2014-07-15

Methods of forming contacts for solar cells are described. In one embodiment, a method includes forming a silicon layer above a substrate, forming and patterning a solid-state p-type dopant source on the silicon layer, forming an n-type dopant source layer over exposed regions of the silicon layer and over a plurality of regions of the solid-state p-type dopant source, and heating the substrate to provide a plurality of n-type doped silicon regions among a plurality of p-type doped silicon regions.

Effect of surface morphology on friction of graphene on various substrates

NASA Astrophysics Data System (ADS)

Cho, Dae-Hyun; Wang, Lei; Kim, Jin-Seon; Lee, Gwan-Hyoung; Kim, Eok Su; Lee, Sunhee; Lee, Sang Yoon; Hone, James; Lee, Changgu

2013-03-01

The friction of graphene on various substrates, such as SiO2, h-BN, bulk-like graphene, and mica, was investigated to characterize the adhesion level between graphene and the underlying surface. The friction of graphene on SiO2 decreased with increasing thickness and converged around the penta-layers due to incomplete contact between the two surfaces. However, the friction of graphene on an atomically flat substrate, such as h-BN or bulk-like graphene, was low and comparable to that of bulk-like graphene. In contrast, the friction of graphene folded onto bulk-like graphene was indistinguishable from that of mono-layer graphene on SiO2 despite the ultra-smoothness of bulk-like graphene. The characterization of the graphene's roughness before and after folding showed that the corrugation of graphene induced by SiO2 morphology was preserved even after it was folded onto an atomically flat substrate. In addition, graphene deposited on mica, when folded, preserved the same corrugation level as before the folding event. Our friction measurements revealed that graphene, once exfoliated from the bulk crystal, tends to maintain its corrugation level even after it is folded onto an atomically flat substrate and that ultra-flatness in both graphene and the substrate is required to achieve the intimate contact necessary for strong adhesion.The friction of graphene on various substrates, such as SiO2, h-BN, bulk-like graphene, and mica, was investigated to characterize the adhesion level between graphene and the underlying surface. The friction of graphene on SiO2 decreased with increasing thickness and converged around the penta-layers due to incomplete contact between the two surfaces. However, the friction of graphene on an atomically flat substrate, such as h-BN or bulk-like graphene, was low and comparable to that of bulk-like graphene. In contrast, the friction of graphene folded onto bulk-like graphene was indistinguishable from that of mono-layer graphene on SiO2 despite the ultra-smoothness of bulk-like graphene. The characterization of the graphene's roughness before and after folding showed that the corrugation of graphene induced by SiO2 morphology was preserved even after it was folded onto an atomically flat substrate. In addition, graphene deposited on mica, when folded, preserved the same corrugation level as before the folding event. Our friction measurements revealed that graphene, once exfoliated from the bulk crystal, tends to maintain its corrugation level even after it is folded onto an atomically flat substrate and that ultra-flatness in both graphene and the substrate is required to achieve the intimate contact necessary for strong adhesion. Electronic supplementary information (ESI) available: Sample preparation method, identification of graphene thickness, AFM and FFM measurements. See DOI: 10.1039/c3nr34181j

Tunable Metasurface and Flat Optical Zoom Lens on a Stretchable Substrate.

PubMed

Ee, Ho-Seok; Agarwal, Ritesh

2016-04-13

A mechanically reconfigurable metasurface that can continuously tune the wavefront is demonstrated in the visible frequency range by changing the lattice constant of a complex Au nanorod array fabricated on a stretchable polydimethylsiloxane substrate. It is shown that the anomalous refraction angle of visible light at 632.8 nm interacting with the tunable metasurface can be adjusted from 11.4° to 14.9° by stretching the substrate by ∼30%. An ultrathin flat 1.7× zoom lens whose focal length can continuously be changed from 150 to 250 μm is realized, which also demonstrates the potential of utilizing metasurfaces for reconfigurable flat optics.

Method for deposition of a conductor in integrated circuits

DOEpatents

Creighton, J.R.; Dominguez, F.; Johnson, A.W.; Omstead, T.R.

1997-09-02

A method is described for fabricating integrated semiconductor circuits and, more particularly, for the selective deposition of a conductor onto a substrate employing a chemical vapor deposition process. By way of example, tungsten can be selectively deposited onto a silicon substrate. At the onset of loss of selectivity of deposition of tungsten onto the silicon substrate, the deposition process is interrupted and unwanted tungsten which has deposited on a mask layer with the silicon substrate can be removed employing a halogen etchant. Thereafter, a plurality of deposition/etch back cycles can be carried out to achieve a predetermined thickness of tungsten. 2 figs.

Development of a Novel Transparent Flexible Capacitive Micromachined Ultrasonic Transducer

PubMed Central

Pang, Da-Chen; Chang, Cheng-Min

2017-01-01

This paper presents the world’s first transparent flexible capacitive micromachined ultrasonic transducer (CMUT) that was fabricated through a roll-lamination technique. This polymer-based CMUT has advantages of transparency, flexibility, and non-contacting detection which provide unique functions in display panel applications. Comprising an indium tin oxide-polyethylene terephthalate (ITO-PET) substrate, SU-8 sidewall and vibrating membranes, and silver nanowire transparent electrode, the transducer has visible-light transmittance exceeding 80% and can operate on curved surfaces with a 40 mm radius of curvature. Unlike the traditional silicon-based high temperature process, the CMUT can be fabricated on a flexible substrate at a temperature below 100 °C to reduce residual stress introduced at high temperature. The CMUT on the curved surfaces can detect a flat target and finger at distances up to 50 mm and 40 mm, respectively. The transparent flexible CMUT provides a better human-machine interface than existing touch panels because it can be integrated with a display panel for non-contacting control in a health conscious environment and the flexible feature is critical for curved display and wearable electronics. PMID:28632157

EUVL mask patterning with blanks from commercial suppliers

NASA Astrophysics Data System (ADS)

Yan, Pei-Yang; Zhang, Guojing; Nagpal, Rajesh; Shu, Emily Y.; Li, Chaoyang; Qu, Ping; Chen, Frederick T.

2004-12-01

Extreme Ultraviolet Lithography (EUVL) reflective mask blank development includes low thermal expansion material fabrication, mask substrate finishing, reflective multi-layer (ML) and capping layer deposition, buffer (optional)/absorber stack deposition, EUV specific metrology, and ML defect inspection. In the past, we have obtained blanks deposited with various layer stacks from several vendors. Some of them are not commercial suppliers. As a result, the blank and patterned mask qualities are difficult to maintain and improve. In this paper we will present the evaluation results of the EUVL mask pattering processes with the complete EUVL mask blanks supplied by the commercial blank supplier. The EUVL mask blanks used in this study consist of either quartz or ULE substrates which is a type of low thermal expansion material (LTEM), 40 pairs of molybdenum/silicon (Mo/Si) ML layer, thin ruthenium (Ru) capping layer, tantalum boron nitride (TaBN) absorber, and chrome (Cr) backside coating. No buffer layer is used. Our study includes the EUVL mask blank characterization, patterned EUVL mask characterization, and the final patterned EUVL mask flatness evaluation.

High-Performance Ultrathin Organic-Inorganic Hybrid Silicon Solar Cells via Solution-Processed Interface Modification.

PubMed

Zhang, Jie; Zhang, Yinan; Song, Tao; Shen, Xinlei; Yu, Xuegong; Lee, Shuit-Tong; Sun, Baoquan; Jia, Baohua

2017-07-05

Organic-inorganic hybrid solar cells based on n-type crystalline silicon and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) exhibited promising efficiency along with a low-cost fabrication process. In this work, ultrathin flexible silicon substrates, with a thickness as low as tens of micrometers, were employed to fabricate hybrid solar cells to reduce the use of silicon materials. To improve the light-trapping ability, nanostructures were built on the thin silicon substrates by a metal-assisted chemical etching method (MACE). However, nanostructured silicon resulted in a large amount of surface-defect states, causing detrimental charge recombination. Here, the surface was smoothed by solution-processed chemical treatment to reduce the surface/volume ratio of nanostructured silicon. Surface-charge recombination was dramatically suppressed after surface modification with a chemical, associated with improved minority charge-carrier lifetime. As a result, a power conversion efficiency of 9.1% was achieved in the flexible hybrid silicon solar cells, with a substrate thickness as low as ∼14 μm, indicating that interface engineering was essential to improve the hybrid junction quality and photovoltaic characteristics of the hybrid devices.

Circularly polarized Raman study on diamond structure crystals

NASA Astrophysics Data System (ADS)

Lee, Je-Ho; Kim, Sera; Seong, Maeng-Je

2018-01-01

Circularly polarized Raman and/or photoluminescence (PL) analyses have recently been very important in studying physical properties of many layered materials that were either mechanically exfoliated or grown by chemical-vapor-deposition (CVD) on silicon substrates. Since silicon Raman signal is always accompanied by the circularly polarized Raman and/or PL signal from the layered materials, observation of proper circularly polarized Raman selection rules on silicon substrates would be extremely good indicator that the circularly polarized Raman and/or PL measurements on the layered materials were done properly. We have performed circularly polarized Raman measurements on silicon substrates and compared the results with the Raman intensities calculated by using Raman tensors of the diamond crystal structure. Our experimental results were in excellent agreement with the calculation. Similar circularly polarized Raman analysis done on germanium substrate also showed good agreement.

Passivation coating for flexible substrate mirrors

DOEpatents

Tracy, C. Edwin; Benson, David K.

1990-01-01

A protective diffusion barrier for metalized mirror structures is provided by a layer or coating of silicon nitride which is a very dense, transparent, dielectric material that is impervious to water, alkali, and other impurities and corrosive substances that typically attack the metal layers of mirrors and cause degradation of the mirrors' reflectivity. The silicon nitride layer can be deposited on the substrate before metal deposition thereon to stabilize the metal/substrate interface, and it can be deposited over the metal to encapsulate it and protect the metal from corrosion or other degradation. Mirrors coated with silicon nitride according to this invention can also be used as front surface mirrors. Also, the silver or other reflective metal layer on mirrors comprising thin, lightweight, flexible substrates of metal or polymer sheets coated with glassy layers can be protected with silicon nitride according to this invention.

Flat-plate solar array project: Experimental process system development unit for producing semiconductor-grade silicon using the silane-to-silicon process

NASA Technical Reports Server (NTRS)

1981-01-01

The engineering design, fabrication, assembly, operation, economic analysis, and process support research and development for an Experimental Process System Development Unit for producing semiconductor-grade silicon using the slane-to-silicon process are reported. The design activity was completed. About 95% of purchased equipment was received. The draft of the operations manual was about 50% complete and the design of the free-space system continued. The system using silicon power transfer, melting, and shotting on a psuedocontinuous basis was demonstrated.

Decal transfer microfabrication

DOEpatents

Nuzzo, Ralph G.; Childs, William Robert

2004-10-19

A method of making a microstructure includes forming a pattern in a surface of a silicon-containing elastomer, oxidizing the pattern, contacting the pattern with a substrate; and bonding the oxidized pattern and the substrate such that the pattern and the substrate are irreversibly attached. The silicon-containing elastomer may be removably attached to a transfer pad.

Modification of surface properties of cellulosic substrates by quaternized silicone emulsions.

PubMed

Purohit, Parag S; Somasundaran, P

2014-07-15

The present work describes the effect of quaternization of silicones as well as the relevant treatment parameter pH on the frictional, morphological and relaxation properties of fabric substrates. Due to their unique surface properties, silicone polymers are extensively used to modify surface properties of various materials, although the effects of functionalization of silicones and relevant process conditions on modification of substrates are not well understood. Specifically we show a considerable reduction in fabric friction, roughness and waviness upon treatment with quaternized silicones. The treatment at acidic pH results in better deposition of silicone polymers onto the fabric as confirmed through streaming potential measurements which show charge reversal of the fabric. Interestingly, Raman spectroscopy studies show the band of C-O ring stretching mode at ∼1095 cm(-1) shift towards higher wavenumber indicating lowering of stress in fibers upon appropriate silicone treatment. Thus along with the morphological and frictional properties being altered, silicone treatment can lead to a reduction in fabric strain. It is concluded that the electrostatic interactions play an initial role in modification of the fiber substrate followed by multilayer deposition of polymer. This multi-technique approach to study fiber properties upon treatment by combining macro to molecular level methods has helped in understanding of new functional coating materials. Copyright © 2014 Elsevier Inc. All rights reserved.

Modifying Surface Fluctuations of Polymer Melt Films with Substrate Modification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Yang; He, Qiming; Zhang, Fan

Deposition of a plasma polymerized film on a silicon substrate substantially changes the fluctuations on the surface of a sufficiently thin, melt polystyrene (PS) film atop the substrate. Surface fluctuation relaxation times measured with X-ray photon correlation spectroscopy (XPCS) for ca. 4R g thick melt films of 131 kg/mol linear PS on silicon and on a plasma polymer modified silicon wafer can both be described using a hydrodynamic continuum theory (HCT) that assumes the film is characterized throughout its depth by the bulk viscosity. However, when the film thickness is reduced to ~3R g, confinement effects are evident. The surfacemore » fluctuations are slower than predicted using the HCT, and the confinement effect for the PS on silicon is larger than that for the PS on the plasma polymerized film. This deviation is thus due to a difference in the thicknesses of the strongly adsorbed layers at the substrate which are impacted by the substrate surface energy.« less

Modifying Surface Fluctuations of Polymer Melt Films with Substrate Modification

DOE PAGES

Zhou, Yang; He, Qiming; Zhang, Fan; ...

2017-08-14

Deposition of a plasma polymerized film on a silicon substrate substantially changes the fluctuations on the surface of a sufficiently thin, melt polystyrene (PS) film atop the substrate. Surface fluctuation relaxation times measured with X-ray photon correlation spectroscopy (XPCS) for ca. 4R g thick melt films of 131 kg/mol linear PS on silicon and on a plasma polymer modified silicon wafer can both be described using a hydrodynamic continuum theory (HCT) that assumes the film is characterized throughout its depth by the bulk viscosity. However, when the film thickness is reduced to ~3R g, confinement effects are evident. The surfacemore » fluctuations are slower than predicted using the HCT, and the confinement effect for the PS on silicon is larger than that for the PS on the plasma polymerized film. This deviation is thus due to a difference in the thicknesses of the strongly adsorbed layers at the substrate which are impacted by the substrate surface energy.« less

Diamond Composite Films for Protective Coatings on Metals and Method of Formation

NASA Technical Reports Server (NTRS)

Ong, Tiong P. (Inventor); Shing, Yuh-Han (Inventor)

1997-01-01

Composite films consisting of diamond crystallites and hard amorphous films such as diamond-like carbon, titanium nitride, and titanium oxide are provided as protective coatings for metal substrates against extremely harsh environments. A composite layer having diamond crystallites and a hard amorphous film is affixed to a metal substrate via an interlayer including a bottom metal silicide film and a top silicon carbide film. The interlayer is formed either by depositing metal silicide and silicon carbide directly onto the metal substrate, or by first depositing an amorphous silicon film, then allowing top and bottom portions of the amorphous silicon to react during deposition of the diamond crystallites, to yield the desired interlayer structure.

Silicon nitride films deposited with an electron beam created plasma

NASA Technical Reports Server (NTRS)

Bishop, D. C.; Emery, K. A.; Rocca, J. J.; Thompson, L. R.; Zamani, H.; Collins, G. J.

1984-01-01

The electron beam assisted chemical vapor deposition (EBCVD) of silicon nitride films using NH3, N2, and SiH4 as the reactant gases is reported. The films have been deposited on aluminum, SiO2, and polysilicon film substrates as well as on crystalline silicon substrates. The range of experimental conditions under which silicon nitrides have been deposited includes substrate temperatures from 50 to 400 C, electron beam currents of 2-40 mA, electron beam energies of 1-5 keV, total ambient pressures of 0.1-0.4 Torr, and NH3/SiH4 mass flow ratios of 1-80. The physical, electrical, and chemical properties of the EBCVD films are discussed.

Transistors using crystalline silicon devices on glass

DOEpatents

McCarthy, A.M.

1995-05-09

A method is disclosed for fabricating transistors using single-crystal silicon devices on glass. This method overcomes the potential damage that may be caused to the device during high voltage bonding and employs a metal layer which may be incorporated as part of the transistor. This is accomplished such that when the bonding of the silicon wafer or substrate to the glass substrate is performed, the voltage and current pass through areas where transistors will not be fabricated. After removal of the silicon substrate, further metal may be deposited to form electrical contact or add functionality to the devices. By this method both single and gate-all-around devices may be formed. 13 figs.

Method for fabricating transistors using crystalline silicon devices on glass

DOEpatents

McCarthy, Anthony M.

1997-01-01

A method for fabricating transistors using single-crystal silicon devices on glass. This method overcomes the potential damage that may be caused to the device during high voltage bonding and employs a metal layer which may be incorporated as part of the transistor. This is accomplished such that when the bonding of the silicon wafer or substrate to the glass substrate is performed, the voltage and current pass through areas where transistors will not be fabricated. After removal of the silicon substrate, further metal may be deposited to form electrical contact or add functionality to the devices. By this method both single and gate-all-around devices may be formed.

Method for fabricating transistors using crystalline silicon devices on glass

DOEpatents

McCarthy, A.M.

1997-09-02

A method for fabricating transistors using single-crystal silicon devices on glass. This method overcomes the potential damage that may be caused to the device during high voltage bonding and employs a metal layer which may be incorporated as part of the transistor. This is accomplished such that when the bonding of the silicon wafer or substrate to the glass substrate is performed, the voltage and current pass through areas where transistors will not be fabricated. After removal of the silicon substrate, further metal may be deposited to form electrical contact or add functionality to the devices. By this method both single and gate-all-around devices may be formed. 13 figs.

Rough SERS substrate based on gold coated porous silicon layer prepared on the silicon backside surface

NASA Astrophysics Data System (ADS)

Dridi, H.; Haji, L.; Moadhen, A.

2017-04-01

We report in this paper a novel method to elaborate rough Surface Enhanced Raman Scattering (SERS) substrate. A single layer of porous silicon was formed on the silicon backside surface. Morphological characteristics of the porous silicon layer before and after gold deposition were influenced by the rough character (gold size). The reflectance measurements showed a dependence of the gold nano-grains size on the surface nature, through the Localized Surface Plasmon (LSP) band properties. SERS signal of Rhodamine 6G used as a model analyte, adsorbed on the rough porous silicon layer revealed a marked enhancement of its vibrational modes intensities.

Silicon Nanowire Growth at Chosen Positions and Orientations

NASA Technical Reports Server (NTRS)

Getty, Stephanie A.

2009-01-01

It is now possible to grow silicon nanowires at chosen positions and orientations by a method that involves a combination of standard microfabrication processes. Because their positions and orientations can be chosen with unprecedented precision, the nanowires can be utilized as integral parts of individually electronically addressable devices in dense arrays. Nanowires made from silicon and perhaps other semiconductors hold substantial promise for integration into highly miniaturized sensors, field-effect transistors, optoelectronic devices, and other electronic devices. Like bulk semiconductors, inorganic semiconducting nanowires are characterized by electronic energy bandgaps that render them suitable as means of modulating or controlling electronic signals through electrostatic gating, in response to incident light, or in response to molecules of interest close to their surfaces. There is now potential for fabricating arrays of uniform, individually electronically addressable nanowires tailored to specific applications. The method involves formation of metal catalytic particles at the desired positions on a substrate, followed by heating the substrate in the presence of silane gas. The figure illustrates an example in which a substrate includes a silicon dioxide surface layer that has been etched into an array of pillars and the catalytic (in this case, gold) particles have been placed on the right-facing sides of the pillars. The catalytic thermal decomposition of the silane to silicon and hydrogen causes silicon columns (the desired nanowires) to grow outward from the originally catalyzed spots on the substrate, carrying the catalytic particles at their tips. Thus, the position and orientation of each silicon nanowire is determined by the position of its originally catalyzed spot on the substrate surface, and the orientation of the nanowire is perpendicular to the substrate surface at the originally catalyzed spot.

Flat-plate solar array project. Task 1: Silicon material: Investigation of the hydrochlorination of SiC1sub4

NASA Technical Reports Server (NTRS)

Mui, J. Y. P.

1981-01-01

A two inch-diameter stainless steel reactor was designed to operate at pressure up to 500 psig and at temperature up to 600 C in order to study the hydrochlorination of silicon tetrachloride and metallurgical grade (m.g.) silicon metal to trichlorosilane. The hydrochlorination apparatus is described and operation safety and pollution control are discussed.

High-κ TiO{sub 2} thin film prepared by sol-gel spin-coating method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Arvind; Mondal, Sandip; Rao, K. S. R. Koteswara, E-mail: ksrkrao@physics.iisc.ernet.in

2015-06-24

High-k TiO{sub 2} thin film on p-type silicon substrate was fabricated by a combined sol-gel and spin coating method. Thus deposited titania film had anatase phase with a small grain size of 16 nm and surface roughness of ≅ 0.6 nm. The oxide capacitance (C{sub ox}), flat band capacitance (C{sub FB}), flat band voltage (V{sub FB}), oxide trapped charge (Q{sub ot}), calculated from the high frequency (1 MHz) C-V curve were 0.47 nF, 0.16 nF, − 0.91 V, 4.7x10{sup −12} C, respectively. As compared to the previous reports, a high dielectric constant of 94 at 1 MHz frequency was observedmore » in the devices investigated here and an equivalent oxide thickness (EOT) was 4.1 nm. Dispersion in accumulation capacitance shows a linear relationship with AC frequencies. Leakage current density was found in acceptable limits (2.1e-5 A/cm{sup 2} for −1 V and 5.7e-7 A/cm{sup 2} for +1 V) for CMOS applications.« less

Formation of porous silicon oxide from substrate-bound silicon rich silicon oxide layers by continuous-wave laser irradiation

NASA Astrophysics Data System (ADS)

Wang, Nan; Fricke-Begemann, Th.; Peretzki, P.; Ihlemann, J.; Seibt, M.

2018-03-01

Silicon nanocrystals embedded in silicon oxide that show room temperature photoluminescence (PL) have great potential in silicon light emission applications. Nanocrystalline silicon particle formation by laser irradiation has the unique advantage of spatially controlled heating, which is compatible with modern silicon micro-fabrication technology. In this paper, we employ continuous wave laser irradiation to decompose substrate-bound silicon-rich silicon oxide films into crystalline silicon particles and silicon dioxide. The resulting microstructure is studied using transmission electron microscopy techniques with considerable emphasis on the formation and properties of laser damaged regions which typically quench room temperature PL from the nanoparticles. It is shown that such regions consist of an amorphous matrix with a composition similar to silicon dioxide which contains some nanometric silicon particles in addition to pores. A mechanism referred to as "selective silicon ablation" is proposed which consistently explains the experimental observations. Implications for the damage-free laser decomposition of silicon-rich silicon oxides and also for controlled production of porous silicon dioxide films are discussed.

Galvanic displacement reaction and rapid thermal annealing in size/shape controlling silver nanoparticles on silicon substrate

NASA Astrophysics Data System (ADS)

Ghosh, Tapas; Satpati, Biswarup

2017-05-01

The effect of the thermal annealing on silver nanoparticles deposited on silicon surface has been studied. The silver nanoparticles have been deposited by the galvanic displacement reaction. Rapid thermal annealing (RTA) has been performed on the Si substrate, containing the silver nanoparticles. The scanning transmission electron microscopy (STEM), energy dispersive X-ray (EDX) spectroscopy and scanning electron microscopy (SEM) study show that the galvanic displacement reaction and subsequent rapid thermal annealing could lead to well separated and spherical shaped larger silver nanoparticles on silicon substrate.

Development of refractory armored silicon carbide by infrared transient liquid phase processing

NASA Astrophysics Data System (ADS)

Hinoki, Tatsuya; Snead, Lance L.; Blue, Craig A.

2005-12-01

Tungsten (W) and molybdenum (Mo) were coated on silicon carbide (SiC) for use as a refractory armor using a high power plasma arc lamp at powers up to 23.5 MW/m 2 in an argon flow environment. Both tungsten powder and molybdenum powder melted and formed coating layers on silicon carbide within a few seconds. The effect of substrate pre-treatment (vapor deposition of titanium (Ti) and tungsten, and annealing) and sample heating conditions on microstructure of the coating and coating/substrate interface were investigated. The microstructure was observed by scanning electron microscopy (SEM) and optical microscopy (OM). The mechanical properties of the coated materials were evaluated by four-point flexural tests. A strong tungsten coating was successfully applied to the silicon carbide substrate. Tungsten vapor deposition and pre-heating at 5.2 MW/m 2 made for a refractory layer containing no cracks propagating into the silicon carbide substrate. The tungsten coating was formed without the thick reaction layer. For this study, small tungsten carbide grains were observed adjacent to the interface in all conditions. In addition, relatively large, widely scattered tungsten carbide grains and a eutectic structure of tungsten and silicon were observed through the thickness in the coatings formed at lower powers and longer heating times. The strength of the silicon carbide substrate was somewhat decreased as a result of the processing. Vapor deposition of tungsten prior to powder coating helped prevent this degradation. In contrast, molybdenum coating was more challenging than tungsten coating due to the larger coefficient of thermal expansion (CTE) mismatch as compared to tungsten and silicon carbide. From this work it is concluded that refractory armoring of silicon carbide by Infrared Transient Liquid Phase Processing is possible. The tungsten armored silicon carbide samples proved uniform, strong, and capable of withstanding thermal fatigue testing.

Improving performance of Si/CdS micro-/nanoribbon p-n heterojunction light emitting diodes by trenched structure

NASA Astrophysics Data System (ADS)

Huang, Shiyuan; Wu, Yuanpeng; Ma, Xiangyang; Yang, Zongyin; Liu, Xu; Yang, Qing

2018-05-01

Realizing high performance silicon based light sources has been an unremitting pursuit for researchers. In this letter, we propose a simple structure to enhance electroluminescence emission and reduce the threshold of injected current of silicon/CdS micro-/nanoribbon p-n heterojunction visible light emitting diodes, by fabricating trenched structure on silicon substrate to mount CdS micro-/nanoribbon. A series of experiments and simulation analysis favors the rationality and validity of our mounting design. After mounting the CdS micro-/nanoribbon, the optical field confinement increases, and absorption and losses from high refractive silicon substrate are effectively reduced. Meanwhile the sharp change of silicon substrate near heterojunction also facilitates the balance between electron current and hole current, which substantially conduces to the stable amplification of electroluminescence emission in CdS micro-/nanoribbon.

Thickness determination of large-area films of yttria-stabilized zirconia produced by pulsed laser deposition

NASA Astrophysics Data System (ADS)

Pryds, N.; Toftmann, B.; Bilde-Sørensen, J. B.; Schou, J.; Linderoth, S.

2006-04-01

Films of yttria-stabilized zirconia (YSZ) on a polished silicon substrate of diameter up to 125 mm have been produced in a large-area pulsed laser deposition (PLD) setup under typical PLD conditions. The film thickness over the full film area has been determined by energy-dispersive X-ray spectrometry in a scanning electron microscope (SEM) with use of a method similar to one described by Bishop and Poole. The attenuation of the electron-induced X-rays from the Si wafer by the film was monitored at a number of points along a diameter and the thickness was determined by Monte Carlo simulations of the attenuation for various values of film thickness with the program CASINO. These results have been compared with direct measurements in the SEM of the film thickness on a cross-section on one of the wafers. The results of these measurements demonstrate the ability of this technique to accurately determine the thickness of a large film, i.e. up to diameters of 125 mm, in a relatively short time, without destroying the substrate, without the need of a standard sample and without the need of a flat substrate. We have also demonstrated that by controlling the deposition parameters large-area YSZ films with uniform thickness can be produced.

Al203 thin films on Silicon and Germanium substrates for CMOS and flash memory applications

NASA Astrophysics Data System (ADS)

Gopalan, Sundararaman; Dutta, Shibesh; Ramesh, Sivaramakrishnan; Prathapan, Ragesh; Sreehari G., S.

2017-07-01

As scaling of device dimensions has continued, it has become necessary to replace traditional SiO2 with high dielectric constant materials in the conventional CMOS devices. In addition, use of metal gate electrodes and Germanium substrates may have to be used in order to address leakage and mobility issues. Al2O3 is one of the potential candidates both for CMOS and as a blocking dielectric for Flash memory applications owing to its low leakage. In this study, the effects of sputtering conditions and post-deposition annealing conditions on the electrical and reliability characteristics of MOS capacitors using Al2O3 films on Si and Ge substrates with Aluminium gate electrodes have been presented. It was observed that higher sputtering power resulted in larger flat-band voltage (Vfb) shifts, more hysteresis, higher interface state density (Dit) and a poorer reliability. Wit was also found that while a short duration high temperature annealing improves film characteristics, a long duration anneal even at 800C was found to be detrimental to MOS characteristics. Finally, the electronic conduction mechanism in Al2O3 films was also studied. It was observed that the conduction mechanism varied depending on the annealing condition, thickness of film and electric field.

Flat-plate solar array project: Experimental process system development unit for producing semiconductor-grade silicon using the silane-to-silicon process

NASA Technical Reports Server (NTRS)

1983-01-01

The process technology for the manufacture of semiconductor-grade silicon in a large commercial plant by 1986, at a price less than $14 per kilogram of silicon based on 1975 dollars is discussed. The engineering design, installation, checkout, and operation of an Experimental Process System Development unit was discussed. Quality control of scaling-up the process and an economic analysis of product and production costs are discussed.

Hybrid emitter all back contact solar cell

DOEpatents

Loscutoff, Paul; Rim, Seung

2016-04-12

An all back contact solar cell has a hybrid emitter design. The solar cell has a thin dielectric layer formed on a backside surface of a single crystalline silicon substrate. One emitter of the solar cell is made of doped polycrystalline silicon that is formed on the thin dielectric layer. The other emitter of the solar cell is formed in the single crystalline silicon substrate and is made of doped single crystalline silicon. The solar cell includes contact holes that allow metal contacts to connect to corresponding emitters.

Silicon carbide and other films and method of deposition

NASA Technical Reports Server (NTRS)

Mehregany, Mehran (Inventor); Zorman, Christian A. (Inventor); Fu, Xiao-An (Inventor); Dunning, Jeremy L. (Inventor)

2007-01-01

A method of depositing a ceramic film, particularly a silicon carbide film, on a substrate is disclosed in which the residual stress, residual stress gradient, and resistivity are controlled. Also disclosed are substrates having a deposited film with these controlled properties and devices, particularly MEMS and NEMS devices, having substrates with films having these properties.

Coated silicon comprising material for protection against environmental corrosion

NASA Technical Reports Server (NTRS)

Hazel, Brian Thomas (Inventor)

2009-01-01

In accordance with an embodiment of the invention, an article is disclosed. The article comprises a gas turbine engine component substrate comprising a silicon material; and an environmental barrier coating overlying the substrate, wherein the environmental barrier coating comprises cerium oxide, and the cerium oxide reduces formation of silicate glass on the substrate upon exposure to corrodant sulfates.

Silicon carbide and other films and method of deposition

NASA Technical Reports Server (NTRS)

Mehregany, Mehran (Inventor); Zorman, Christian A. (Inventor); Fu, Xiao-An (Inventor); Dunning, Jeremy (Inventor)

2011-01-01

A method of depositing a ceramic film, particularly a silicon carbide film, on a substrate is disclosed in which the residual stress, residual stress gradient, and resistivity are controlled. Also disclosed are substrates having a deposited film with these controlled properties and devices, particularly MEMS and NEMS devices, having substrates with films having these properties.

Enhanced optical output power of InGaN/GaN light-emitting diodes grown on a silicon (111) substrate with a nanoporous GaN layer.

PubMed

Lee, Kwang Jae; Chun, Jaeyi; Kim, Sang-Jo; Oh, Semi; Ha, Chang-Soo; Park, Jung-Won; Lee, Seung-Jae; Song, Jae-Chul; Baek, Jong Hyeob; Park, Seong-Ju

2016-03-07

We report the growth of InGaN/GaN multiple quantum wells blue light-emitting diodes (LEDs) on a silicon (111) substrate with an embedded nanoporous (NP) GaN layer. The NP GaN layer is fabricated by electrochemical etching of n-type GaN on the silicon substrate. The crystalline quality of crack-free GaN grown on the NP GaN layer is remarkably improved and the residual tensile stress is also decreased. The optical output power is increased by 120% at an injection current of 20 mA compared with that of conventional LEDs without a NP GaN layer. The large enhancement of optical output power is attributed to the reduction of threading dislocation, effective scattering of light in the LED, and the suppression of light propagation into the silicon substrate by the NP GaN layer.

Oxidation resistant high temperature thermal cycling resistant coatings on silicon-based substrates and process for the production thereof

DOEpatents

Sarin, V.K.

1990-08-21

An oxidation resistant, high temperature thermal cycling resistant coated ceramic article for ceramic heat engine applications is disclosed. The substrate is a silicon-based material, i.e. a silicon nitride- or silicon carbide-based monolithic or composite material. The coating is a graded coating of at least two layers: an intermediate AlN or Al[sub x]N[sub y]O[sub z] layer and an aluminum oxide or zirconium oxide outer layer. The composition of the coating changes gradually from that of the substrate to that of the AlN or Al[sub x]N[sub y]O[sub z] layer and further to the composition of the aluminum oxide or zirconium oxide outer layer. Other layers may be deposited over the aluminum oxide layer. A CVD process for depositing the graded coating on the substrate is also disclosed.

Oxidation resistant high temperature thermal cycling resistant coatings on silicon-based substrates and process for the production thereof

DOEpatents

Sarin, Vinod K.

1990-01-01

An oxidation resistant, high temperature thermal cycling resistant coated ceramic article for ceramic heat engine applications. The substrate is a silicon-based material, i.e. a silicon nitride- or silicon carbide-based monolithic or composite material. The coating is a graded coating of at least two layers: an intermediate AlN or Al.sub.x N.sub.y O.sub.z layer and an aluminum oxide or zirconium oxide outer layer. The composition of the coating changes gradually from that of the substrate to that of the AlN or Al.sub.x N.sub.y O.sub.z layer and further to the composition of the aluminum oxide or zirconium oxide outer layer. Other layers may be deposited over the aluminum oxide layer. A CVD process for depositing the graded coating on the substrate is also disclosed.

Improved method of edge coating flat ribbon wire

NASA Technical Reports Server (NTRS)

1966-01-01

Method to coat the edges of flat ribbon wire is devised by using enamel with modified flow properties due to addition of 2 to 4 percent silicon. Conventional coating procedes several edge coatings to minimize oxidation and additional conventional coats are applied after edge coating to build up thickness.

Fabrication of a Silicon Nanowire on a Bulk Substrate by Use of a Plasma Etching and Total Ionizing Dose Effects on a Gate-All-Around Field-Effect Transistor

NASA Technical Reports Server (NTRS)

Moon, Dong-Il; Han, Jin-Woo; Meyyappan, Meyya

2016-01-01

The gate all around transistor is investigated through experiment. The suspended silicon nanowire for the next generation is fabricated on bulk substrate by plasma etching method. The scallop pattern generated by Bosch process is utilized to form a floating silicon nanowire. By combining anisotropic and istropic silicon etch process, the shape of nanowire is accurately controlled. From the suspended nanowire, the gate all around transistor is demonstrated. As the silicon nanowire is fully surrounded by the gate, the device shows excellent electrostatic characteristics.

Study on Silicon Microstructure Processing Technology Based on Porous Silicon

NASA Astrophysics Data System (ADS)

Shang, Yingqi; Zhang, Linchao; Qi, Hong; Wu, Yalin; Zhang, Yan; Chen, Jing

2018-03-01

Aiming at the heterogeneity of micro - sealed cavity in silicon microstructure processing technology, the technique of preparing micro - sealed cavity of porous silicon is proposed. The effects of different solutions, different substrate doping concentrations, different current densities, and different etching times on the rate, porosity, thickness and morphology of the prepared porous silicon were studied. The porous silicon was prepared by different process parameters and the prepared porous silicon was tested and analyzed. For the test results, optimize the process parameters and experiments. The experimental results show that the porous silicon can be controlled by optimizing the parameters of the etching solution and the doping concentration of the substrate, and the preparation of porous silicon with different porosity can be realized by different doping concentration, so as to realize the preparation of silicon micro-sealed cavity, to solve the sensor sensitive micro-sealed cavity structure heterogeneous problem, greatly increasing the application of the sensor.

Crystallization of amorphous silicon thin films deposited by PECVD on nickel-metalized porous silicon.

PubMed

Ben Slama, Sonia; Hajji, Messaoud; Ezzaouia, Hatem

2012-08-17

Porous silicon layers were elaborated by electrochemical etching of heavily doped p-type silicon substrates. Metallization of porous silicon was carried out by immersion of substrates in diluted aqueous solution of nickel. Amorphous silicon thin films were deposited by plasma-enhanced chemical vapor deposition on metalized porous layers. Deposited amorphous thin films were crystallized under vacuum at 750°C. Obtained results from structural, optical, and electrical characterizations show that thermal annealing of amorphous silicon deposited on Ni-metalized porous silicon leads to an enhancement in the crystalline quality and physical properties of the silicon thin films. The improvement in the quality of the film is due to the crystallization of the amorphous film during annealing. This simple and easy method can be used to produce silicon thin films with high quality suitable for thin film solar cell applications.

Crystallization of amorphous silicon thin films deposited by PECVD on nickel-metalized porous silicon

PubMed Central

2012-01-01

Porous silicon layers were elaborated by electrochemical etching of heavily doped p-type silicon substrates. Metallization of porous silicon was carried out by immersion of substrates in diluted aqueous solution of nickel. Amorphous silicon thin films were deposited by plasma-enhanced chemical vapor deposition on metalized porous layers. Deposited amorphous thin films were crystallized under vacuum at 750°C. Obtained results from structural, optical, and electrical characterizations show that thermal annealing of amorphous silicon deposited on Ni-metalized porous silicon leads to an enhancement in the crystalline quality and physical properties of the silicon thin films. The improvement in the quality of the film is due to the crystallization of the amorphous film during annealing. This simple and easy method can be used to produce silicon thin films with high quality suitable for thin film solar cell applications. PMID:22901341

Substrate for thin silicon solar cells

DOEpatents

Ciszek, Theodore F.

1995-01-01

A photovoltaic device for converting solar energy into electrical signals comprises a substrate, a layer of photoconductive semiconductor material grown on said substrate, wherein the substrate comprises an alloy of boron and silicon, the boron being present in a range of from 0.1 to 1.3 atomic percent, the alloy having a lattice constant substantially matched to that of the photoconductive semiconductor material and a resistivity of less than 1.times.10.sup.-3 ohm-cm.

Effect of the substrate on the insulator-metal transition of vanadium dioxide films

NASA Astrophysics Data System (ADS)

Kovács, György J.; Bürger, Danilo; Skorupa, Ilona; Reuther, Helfried; Heller, René; Schmidt, Heidemarie

2011-03-01

Single-phase vanadium dioxide films grown on (0001) sapphire and (001) silicon substrates show a very different insulator-metal electronic transition. A detailed description of the growth mechanisms and the substrate-film interaction is given, and the characteristics of the electronic transition are described by the morphology and grain boundary structure. (Tri-)epitaxy-stabilized columnar growth of VO2 takes place on the sapphire substrate, whereas on silicon the expected Zone II growth is identified. We have found that in the case of the Si substrate the reasons for the broader hysteresis and the lower switching amplitude are the formation of an amorphous insulating VOx (x > 2.6) phase coexisting with VO2 and the high vanadium vacancy concentration of the VO2. These phenomena are the result of the excess oxygen during the growth and the interaction between the silicon substrate and the growing film.

Die singulation method

DOEpatents

Swiler, Thomas P.; Garcia, Ernest J.; Francis, Kathryn M.

2013-06-11

A method is disclosed for singulating die from a semiconductor substrate (e.g. a semiconductor-on-insulator substrate or a bulk silicon substrate) containing an oxide layer (e.g. silicon dioxide or a silicate glass) and one or more semiconductor layers (e.g. monocrystalline or polycrystalline silicon) located above the oxide layer. The method etches trenches through the substrate and through each semiconductor layer about the die being singulated, with the trenches being offset from each other around at least a part of the die so that the oxide layer between the trenches holds the substrate and die together. The trenches can be anisotropically etched using a Deep Reactive Ion Etching (DRIE) process. After the trenches are etched, the oxide layer between the trenches can be etched away with an HF etchant to singulate the die. A release fixture can be located near one side of the substrate to receive the singulated die.

Die singulation method

DOEpatents

Swiler, Thomas P [Albuquerque, NM; Garcia, Ernest J [Albuquerque, NM; Francis, Kathryn M [Rio Rancho, NM

2014-01-07

A method is disclosed for singulating die from a semiconductor substrate (e.g. a semiconductor-on-insulator substrate or a bulk silicon substrate) containing an oxide layer (e.g. silicon dioxide or a silicate glass) and one or more semiconductor layers (e.g. monocrystalline or polycrystalline silicon) located above the oxide layer. The method etches trenches through the substrate and through each semiconductor layer about the die being singulated, with the trenches being offset from each other around at least a part of the die so that the oxide layer between the trenches holds the substrate and die together. The trenches can be anisotropically etched using a Deep Reactive Ion Etching (DRIE) process. After the trenches are etched, the oxide layer between the trenches can be etched away with a HF etchant to singulate the die. A release fixture can be located near one side of the substrate to receive the singulated die.

Gallium-containing polymer brush film as efficient supported Lewis acid catalyst in a glass microreactor

PubMed Central

Munirathinam, Rajesh; Ricciardi, Roberto; Egberink, Richard J M; Huskens, Jurriaan; Holtkamp, Michael; Wormeester, Herbert; Karst, Uwe

2013-01-01

Summary Polystyrene sulfonate polymer brushes, grown on the interior of the microchannels in a microreactor, have been used for the anchoring of gallium as a Lewis acid catalyst. Initially, gallium-containing polymer brushes were grown on a flat silicon oxide surface and were characterized by FTIR, ellipsometry, and X-ray photoelectron spectroscopy (XPS). XPS revealed the presence of one gallium per 2–3 styrene sulfonate groups of the polymer brushes. The catalytic activity of the Lewis acid-functionalized brushes in a microreactor was demonstrated for the dehydration of oximes, using cinnamaldehyde oxime as a model substrate, and for the formation of oxazoles by ring closure of ortho-hydroxy oximes. The catalytic activity of the microreactor could be maintained by periodic reactivation by treatment with GaCl3. PMID:24062830

Silicon microelectronic field-emissive devices for advanced display technology

NASA Astrophysics Data System (ADS)

Morse, J. D.

1993-03-01

Field-emission displays (FED's) offer the potential advantages of high luminous efficiency, low power consumption, and low cost compared to AMLCD or CRT technologies. An LLNL team has developed silicon-point field emitters for vacuum triode structures and has also used thin-film processing techniques to demonstrate planar edge-emitter configurations. LLNL is interested in contributing its experience in this and other FED-related technologies to collaborations for commercial FED development. At LLNL, FED development is supported by computational capabilities in charge transport and surface/interface modeling in order to develop smaller, low-work-function field emitters using a variety of materials and coatings. Thin-film processing, microfabrication, and diagnostic/test labs permit experimental exploration of emitter and resistor structures. High field standoff technology is an area of long-standing expertise that guides development of low-cost spacers for FEDS. Vacuum sealing facilities are available to complete the FED production engineering process. Drivers constitute a significant fraction of the cost of any flat-panel display. LLNL has an advanced packaging group that can provide chip-on-glass technologies and three-dimensional interconnect generation permitting driver placement on either the front or the back of the display substrate.

Progress in the Development of SERS-Active Substrates Based on Metal-Coated Porous Silicon

PubMed Central

Girel, Kseniya V.; Panarin, Andrei; Terekhov, Sergei N.

2018-01-01

The present work gives an overview of the developments in surface-enhanced Raman scattering (SERS) with metal-coated porous silicon used as an active substrate. We focused this review on the research referenced to SERS-active materials based on porous silicon, beginning from the patent application in 2002 and enclosing the studies of this year. Porous silicon and metal deposition technologies are discussed. Since the earliest studies, a number of fundamentally different plasmonic nanostructures including metallic dendrites, quasi-ordered arrays of metallic nanoparticles (NPs), and metallic nanovoids have been grown on porous silicon, defined by the morphology of this host material. SERS-active substrates based on porous silicon have been found to combine a high and well-reproducible signal level, storage stability, cost-effective technology and handy use. They make it possible to identify and study many compounds including biomolecules with a detection limit varying from milli- to femtomolar concentrations. The progress reviewed here demonstrates the great prospects for the extensive use of the metal-coated porous silicon for bioanalysis by SERS-spectroscopy. PMID:29883382

High-speed and on-chip graphene blackbody emitters for optical communications by remote heat transfer.

PubMed

Miyoshi, Yusuke; Fukazawa, Yusuke; Amasaka, Yuya; Reckmann, Robin; Yokoi, Tomoya; Ishida, Kazuki; Kawahara, Kenji; Ago, Hiroki; Maki, Hideyuki

2018-03-29

High-speed light emitters integrated on silicon chips can enable novel architectures for silicon-based optoelectronics, such as on-chip optical interconnects, and silicon photonics. However, conventional light sources based on compound semiconductors face major challenges for their integration with a silicon-based platform because of their difficulty of direct growth on a silicon substrate. Here we report ultra-high-speed (100-ps response time), highly integrated graphene-based on-silicon-chip blackbody emitters in the near-infrared region including telecommunication wavelength. Their emission responses are strongly affected by the graphene contact with the substrate depending on the number of graphene layers. The ultra-high-speed emission can be understood by remote quantum thermal transport via surface polar phonons of the substrates. We demonstrated real-time optical communications, integrated two-dimensional array emitters, capped emitters operable in air, and the direct coupling of optical fibers to the emitters. These emitters can open new routes to on-Si-chip, small footprint, and high-speed emitters for highly integrated optoelectronics and silicon photonics.

Progress in the Development of SERS-Active Substrates Based on Metal-Coated Porous Silicon.

PubMed

Bandarenka, Hanna V; Girel, Kseniya V; Zavatski, Sergey A; Panarin, Andrei; Terekhov, Sergei N

2018-05-21

The present work gives an overview of the developments in surface-enhanced Raman scattering (SERS) with metal-coated porous silicon used as an active substrate. We focused this review on the research referenced to SERS-active materials based on porous silicon, beginning from the patent application in 2002 and enclosing the studies of this year. Porous silicon and metal deposition technologies are discussed. Since the earliest studies, a number of fundamentally different plasmonic nanostructures including metallic dendrites, quasi-ordered arrays of metallic nanoparticles (NPs), and metallic nanovoids have been grown on porous silicon, defined by the morphology of this host material. SERS-active substrates based on porous silicon have been found to combine a high and well-reproducible signal level, storage stability, cost-effective technology and handy use. They make it possible to identify and study many compounds including biomolecules with a detection limit varying from milli- to femtomolar concentrations. The progress reviewed here demonstrates the great prospects for the extensive use of the metal-coated porous silicon for bioanalysis by SERS-spectroscopy.

Prey versus substrate as determinants of habitat choice in a feeding shorebird

NASA Astrophysics Data System (ADS)

Finn, Paul G.; Catterall, Carla P.; Driscoll, Peter V.

2008-11-01

Many shorebirds on their non-breeding grounds feed on macrobenthic fauna which become available at low tide in coastal intertidal flats. The Eastern Curlew Numenius madagascariensis in Moreton Bay Australia, varies greatly in density among different tidal flats. This study asks: how important is the abundance of intertidal prey as a predictor of this variation? We quantified feeding curlews' diet across 12 sites (different tidal flats, each re-visited at least eight times), through 970 focal observations. We also estimated the abundance of total macrobenthic fauna, potential prey taxa and crustacean prey on each tidal flat; measured as the number of individuals and a relative biomass index per unit substrate surface area obtained from substrate core samples. We estimated curlew density at each site using low-tide surveys from every site visit. Curlew density showed a strong positive association with both the density and biomass of fauna and of potential prey ( r values all around 0.70) across the 12 flats. Associations with crustacean density and biomass were also statistically significant (r values both 0.60). However, these variables also showed a strong negative correlation with a measure of substrate resistance (based on the amount of hard material in the substrate core), which was the best predictor of curlew density ( r = -0.82). Curlews were most abundant at sites with the least resistant substrate, and these sites also generally had the highest faunal density and biomass. When the effect of substrate resistance was statistically removed, curlew density was no longer significantly correlated with fauna density and biomass. This suggests that macro-scale habitat choice by Eastern Curlew on their non-breeding grounds is more strongly influenced by prey availability (which is higher when substrate resistance is lower) than by prey density or biomass, although in Moreton Bay a positive correlation across sites meant that these factors were synergistic.

Study of the photovoltaic effect in thin film barium titanate

NASA Technical Reports Server (NTRS)

Grannemann, W. W.; Dharmadhikari, V. S.

1982-01-01

Ferroelectric films of barium titanate were synthesized on silicon and quartz substrates, and the photoelectric effect in the structure consisting of metal deposited ferroelectric barium titanate film silicon was studied. A photovoltage with polarity that depends on the direction of the remanent polarization was observed. The deposition of BaTiO3 on silicon and fused quartz substrates was accomplished by an rf sputtering technique. A series of experiments to study the growth of ferroelectric BaTiO3 films on single crystal silicon and fused quartz substrates were conducted. The ferroelectric character in these films was found on the basis of evidence from the polarization electric field hysteresis loops, capacitance voltage and capacitance temperature techniques and from X-ray diffraction studies.

Method for providing an arbitrary three-dimensional microstructure in silicon using an anisotropic deep etch

DOEpatents

Morales, Alfredo M.; Gonzales, Marcela

2004-06-15

The present invention describes a method for fabricating an embossing tool or an x-ray mask tool, providing microstructures that smoothly vary in height from point-to-point in etched substrates, i.e., structure which can vary in all three dimensions. The process uses a lithographic technique to transfer an image pattern in the surface of a silicon wafer by exposing and developing the resist and then etching the silicon substrate. Importantly, the photoresist is variably exposed so that when developed some of the resist layer remains. The remaining undeveloped resist acts as an etchant barrier to the reactive plasma used to etch the silicon substrate and therefore provides the ability etch structures of variable depths.

Biofunctionalization on alkylated silicon substrate surfaces via "click" chemistry.

PubMed

Qin, Guoting; Santos, Catherine; Zhang, Wen; Li, Yan; Kumar, Amit; Erasquin, Uriel J; Liu, Kai; Muradov, Pavel; Trautner, Barbara Wells; Cai, Chengzhi

2010-11-24

Biofunctionalization of silicon substrates is important to the development of silicon-based biosensors and devices. Compared to conventional organosiloxane films on silicon oxide intermediate layers, organic monolayers directly bound to the nonoxidized silicon substrates via Si-C bonds enhance the sensitivity of detection and the stability against hydrolytic cleavage. Such monolayers presenting a high density of terminal alkynyl groups for bioconjugation via copper-catalyzed azide-alkyne 1,3-dipolar cycloaddition (CuAAC, a "click" reaction) were reported. However, yields of the CuAAC reactions on these monolayer platforms were low. Also, the nonspecific adsorption of proteins on the resultant surfaces remained a major obstacle for many potential biological applications. Herein, we report a new type of "clickable" monolayers grown by selective, photoactivated surface hydrosilylation of α,ω-alkenynes, where the alkynyl terminal is protected with a trimethylgermanyl (TMG) group, on hydrogen-terminated silicon substrates. The TMG groups on the film are readily removed in aqueous solutions in the presence of Cu(I). Significantly, the degermanylation and the subsequent CuAAC reaction with various azides could be combined into a single step in good yields. Thus, oligo(ethylene glycol) (OEG) with an azido tag was attached to the TMG-alkyne surfaces, leading to OEG-terminated surfaces that reduced the nonspecific adsorption of protein (fibrinogen) by >98%. The CuAAC reaction could be performed in microarray format to generate arrays of mannose and biotin with varied densities on the protein-resistant OEG background. We also demonstrated that the monolayer platform could be functionalized with mannose for highly specific capturing of living targets (Escherichia coli expressing fimbriae) onto the silicon substrates.

Quantum cascade lasers grown on silicon.

PubMed

Nguyen-Van, Hoang; Baranov, Alexei N; Loghmari, Zeineb; Cerutti, Laurent; Rodriguez, Jean-Baptiste; Tournet, Julie; Narcy, Gregoire; Boissier, Guilhem; Patriarche, Gilles; Bahriz, Michael; Tournié, Eric; Teissier, Roland

2018-05-08

Technological platforms offering efficient integration of III-V semiconductor lasers with silicon electronics are eagerly awaited by industry. The availability of optoelectronic circuits combining III-V light sources with Si-based photonic and electronic components in a single chip will enable, in particular, the development of ultra-compact spectroscopic systems for mass scale applications. The first circuits of such type were fabricated using heterogeneous integration of semiconductor lasers by bonding the III-V chips onto silicon substrates. Direct epitaxial growth of interband III-V laser diodes on silicon substrates has also been reported, whereas intersubband emitters grown on Si have not yet been demonstrated. We report the first quantum cascade lasers (QCLs) directly grown on a silicon substrate. These InAs/AlSb QCLs grown on Si exhibit high performances, comparable with those of the devices fabricated on their native InAs substrate. The lasers emit near 11 µm, the longest emission wavelength of any laser integrated on Si. Given the wavelength range reachable with InAs/AlSb QCLs, these results open the way to the development of a wide variety of integrated sensors.

Method for enhancing the solubility of dopants in silicon

DOEpatents

Sadigh, Babak; Lenosky, Thomas J.; De La Rubia, Tomas Diaz

2003-09-30

A method for enhancing the equilibrium solid solubility of dopants in silicon, germanium and silicon-germanium alloys. The method involves subjecting silicon-based substrate to biaxial or compression strain. It has been determined that boron solubility was largely enhanced (more than 100%) by a compressive bi-axial strain, based on a size-mismatch theory since the boron atoms are smaller than the silicon atoms. It has been found that the large enhancement or mixing properties of dopants in silicon and germanium substrates is primarily governed by their, and to second order by their size-mismatch with the substrate. Further, it has been determined that the dopant solubility enhancement with strain is most effective when the charge and the size-mismatch of the impurity favor the same type of strain. Thus, the solid solubility of small p-type (e.g., boron) as well as large n-type (e.g., arsenic) dopants can be raised most dramatically by appropriate bi-axial (compressive) strain, and that solubility of a large p-type dopant (e.g, indium) in silicon will be raised due to size-mismatch with silicon, which favors tensile strain, while its negative charge prefers compressive strain, and thus the two effects counteract each other.

Evaporation of liquid droplets on solid substrates. II. Periodic substrates with moving contact lines

NASA Astrophysics Data System (ADS)

Amini, Amirhossein; Homsy, G. M.

2017-04-01

Experiments on evaporating droplets on structured surfaces have shown that the contact line does not move with constant speed, but rather in a steplike "stick-slip" fashion. As a first step in understanding such behavior, we study the evaporation of a two-dimensional volatile liquid droplet on a nonplanar heated solid substrate with a moving contact line and fixed contact angle. The model for the flat case is adapted to include curved substrates, numerical solutions are achieved for various periodic and quasiperiodic substrate profiles, and the dynamics of the contact line and the apparent contact angle are studied. In contrast with our results for a flat substrate, for which the contact line recedes in a nearly constant speed, we observe that the contact line speed and position show significant time variation and that the contact line moves in an approximate steplike fashion on relatively steep substrates. For the simplest case of a periodic substrate, we find that the apparent contact angle is periodic in time. For doubly periodic substrates, we find that the apparent contact angle is periodic and that the problem exhibits a phase-locking behavior. For multimode quasiperiodic substrates, we find the contact line behavior to be temporally complex and not only limited to a stick-slip motion. In all cases, we find that the overall evaporation is increased relative to the flat substrate.

Proceedings of the 24th Project Integration Meeting

NASA Technical Reports Server (NTRS)

Tustin, D.

1984-01-01

Progress made by the Flat-Plate Solar Array Project is described. Reports on silicon sheet growth and characterization, silicon material, process development, high-efficiency cells, environmental isolation, engineering sciences, and reliability physics are presented along with copies of visual presentations made at the 24th Project Integration Meeting.

Fabrication and characterization of physically defined quantum dots on a boron-doped silicon-on-insulator substrate

NASA Astrophysics Data System (ADS)

Mizoguchi, Seiya; Shimatani, Naoki; Kobayashi, Mizuki; Makino, Takaomi; Yamaoka, Yu; Kodera, Tetsuo

2018-04-01

We study hole transport properties in physically defined p-type silicon quantum dots (QDs) on a heavily doped silicon-on-insulator (SOI) substrate. We observe Coulomb diamonds using single QDs and estimate the charging energy as ∼1.6 meV. We obtain the charge stability diagram of double QDs using single QDs as a charge sensor. This is the first demonstration of charge sensing in p-type heavily doped silicon QDs. For future time-resolved measurements, we apply radio-frequency reflectometry using impedance matching of LC circuits to the device. We observe the resonance and estimate the capacitance as ∼0.12 pF from the resonant frequency. This value is smaller than that of the devices with top gates on nondoped SOI substrate. This indicates that high-frequency signals can be applied efficiently to p-type silicon QDs without top gates.

Microelectromechanical pump utilizing porous silicon

DOEpatents

Lantz, Jeffrey W [Albuquerque, NM; Stalford, Harold L [Norman, OK

2011-07-19

A microelectromechanical (MEM) pump is disclosed which includes a porous silicon region sandwiched between an inlet chamber and an outlet chamber. The porous silicon region is formed in a silicon substrate and contains a number of pores extending between the inlet and outlet chambers, with each pore having a cross-section dimension about equal to or smaller than a mean free path of a gas being pumped. A thermal gradient is provided along the length of each pore by a heat source which can be an electrical resistance heater or an integrated circuit (IC). A channel can be formed through the silicon substrate so that inlet and outlet ports can be formed on the same side of the substrate, or so that multiple MEM pumps can be connected in series to form a multi-stage MEM pump. The MEM pump has applications for use in gas-phase MEM chemical analysis systems, and can also be used for passive cooling of ICs.

Silicon nanomembranes as a means to evaluate stress evolution in deposited thin films

Treesearch

Anna M. Clausen; Deborah M. Paskiewicz; Alireza Sadeghirad; Joseph Jakes; Donald E. Savage; Donald S. Stone; Feng Liu; Max G. Lagally

2014-01-01

Thin-film deposition on ultra-thin substrates poses unique challenges because of the potential for a dynamic response to the film stress during deposition. While theoretical studies have investigated film stress related changes in bulk substrates, little has been done to learn how stress might evolve in a film growing on a compliant substrate. We use silicon...

Indium-bump-free antimonide superlattice membrane detectors on silicon substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zamiri, M., E-mail: mzamiri@chtm.unm.edu, E-mail: skrishna@chtm.unm.edu; Klein, B.; Schuler-Sandy, T.

2016-02-29

We present an approach to realize antimonide superlattices on silicon substrates without using conventional Indium-bump hybridization. In this approach, PIN superlattices are grown on top of a 60 nm Al{sub 0.6}Ga{sub 0.4}Sb sacrificial layer on a GaSb host substrate. Following the growth, the individual pixels are transferred using our epitaxial-lift off technique, which consists of a wet-etch to undercut the pixels followed by a dry-stamp process to transfer the pixels to a silicon substrate prepared with a gold layer. Structural and optical characterization of the transferred pixels was done using an optical microscope, scanning electron microscopy, and photoluminescence. The interface betweenmore » the transferred pixels and the new substrate was abrupt, and no significant degradation in the optical quality was observed. An Indium-bump-free membrane detector was then fabricated using this approach. Spectral response measurements provided a 100% cut-off wavelength of 4.3 μm at 77 K. The performance of the membrane detector was compared to a control detector on the as-grown substrate. The membrane detector was limited by surface leakage current. The proposed approach could pave the way for wafer-level integration of photonic detectors on silicon substrates, which could dramatically reduce the cost of these detectors.« less

Flat-top passband filter based on parallel-coupled double microring resonators in silicon

NASA Astrophysics Data System (ADS)

Huang, Qingzhong; Xiao, Xi; Li, Yuntao; Li, Zhiyong; Yu, Yude; Yu, Jinzhong

2009-08-01

Optical filters with box-like response were designed and realized based on parallel-coupled double microrings in silicon-on-insulator. The properties of this design are simulated, considering the impact of the center-to-center distance of two rings, and coupling efficiency. Flat-top passband in the drop channel of the fabricated device was demonstrated with a 1dB bandwidth of 0.82nm, a 1dB/10dB bandwidth ratio of 0.51, an out of band rejection ratio of 14.6dB, as well as a free spectrum range of 13.6nm.

Terrestrial photovoltaic collector technology trends

NASA Technical Reports Server (NTRS)

Shimada, K.; Costogue, E.

1984-01-01

Following the path of space PV collector development in its early stages, terrestrial PV technologies based upon single-crystal silicon have matured rapidly. Currently, terrestrial PV cells with efficiencies approaching space cell efficiencies are being fabricated into modules at a fraction of the space PV module cost. New materials, including CuInSe2 and amorphous silicon, are being developed for lowering the cost, and multijunction materials for achieving higher efficiency. Large grid-interactive, tracking flat-plate power systems and concentrator PV systems totaling about 10 MW, are already in operation. Collector technology development both flat-plate and concentrator, will continue under an extensive government and private industry partnership.

Towards substrate engineering of graphene-silicon Schottky diode photodetectors.

PubMed

Selvi, Hakan; Unsuree, Nawapong; Whittaker, Eric; Halsall, Matthew P; Hill, Ernie W; Thomas, Andrew; Parkinson, Patrick; Echtermeyer, Tim J

2018-02-15

Graphene-silicon Schottky diode photodetectors possess beneficial properties such as high responsivities and detectivities, broad spectral wavelength operation and high operating speeds. Various routes and architectures have been employed in the past to fabricate devices. Devices are commonly based on the removal of the silicon-oxide layer on the surface of silicon by wet-etching before deposition of graphene on top of silicon to form the graphene-silicon Schottky junction. In this work, we systematically investigate the influence of the interfacial oxide layer, the fabrication technique employed and the silicon substrate on the light detection capabilities of graphene-silicon Schottky diode photodetectors. The properties of devices are investigated over a broad wavelength range from near-UV to short-/mid-infrared radiation, radiation intensities covering over five orders of magnitude as well as the suitability of devices for high speed operation. Results show that the interfacial layer, depending on the required application, is in fact beneficial to enhance the photodetection properties of such devices. Further, we demonstrate the influence of the silicon substrate on the spectral response and operating speed. Fabricated devices operate over a broad spectral wavelength range from the near-UV to the short-/mid-infrared (thermal) wavelength regime, exhibit high photovoltage responses approaching 10 6 V W -1 and short rise- and fall-times of tens of nanoseconds.

Solution and interfacial behavior of modified silicone polymers and their interactions with solid substrates

NASA Astrophysics Data System (ADS)

Purohit, Parag

Surface treatment is very important step in many applications such as fabric finishing, coatings, cosmetics and personal care. Silicone polymers are a class of organic/inorganic materials that show unique properties such as weak intermolecular forces and high flexibility enabling even a very high molecular weight chain to achieve optimal orientation on surfaces. Material properties such as softness, repellency, bounciness and friction can therefore be tailored by using appropriately modified silicone polymers. Despite wide applications, the underlying mechanisms of material modification are unknown and tailoring silicones for applications remains mostly empirical. Thus the objective of this research is to understand the solution and interfacial behavior of functionalized silicone polymers, which govern their performance in material modification. Modified silicones are simultaneously hydrophobic and oleophobic in nature and due to this nearly universal non-compatibility, the studies of these polymers present unusual challenges. Due to this incompatible nature, the functionalized silicone polymers were emulsified into O/W emulsions to study their solution and interfacial properties. The colloidal properties such as electrokinetic and droplet distribution of these emulsions are assumed to play an important role in the observed surface and physical properties of solid substrates (in present study, cellulosic substrates) as well the stability of emulsions itself. To understand the effects of modified silicones on cellulosic substrates a variety of techniques such as frictional analysis, scanning electron microscopy and atomic force microscopy that can probe from macro to nano level were used. It is hypothesized that the size distribution and charge of silicone emulsions as well as the physiochemical conditions such as pH, control silicone conformation which in turn affect the modification of the substrate properties. With bimodal droplet distribution of silicone emulsions, the nano-sized droplets can penetrate deeper into the substrate to provide bounciness, whereas macro-sized droplets can coat the top layer leading to friction reduction. It was observed that at pH 5.5 the silicone treatment resulted in charge reversal of fibers as opposed to treatment at pH 9.5. On a macroscopic scale 20% reduction in frictional coefficient of the fabric was observed after treatment with quaternized (cationically modified) silicones as compared to untreated fibers. It was also observed using AFM that the fibrils treated with quaternized silicones are uniform, well stacked and smoother than the untreated fibers. Spectroscopic analysis of treated fibers using Raman spectroscopy indicated a decrease in fiber stress as a function of modification of silicone polymer and the interaction pH. It is concluded that the protonated amine functional silicone (below pH 7) as well as the quaternized silicone interacts with the negatively charged cellulose fibers primarily through electrostatic interactions. It is proposed that this initial surface coating is a uniform thin film which allows further deposition of polymer from the emulsion. It was observed that at high pH the zetapotential of silicone emulsions decreases drastically and the nano emulsions turn turbid. It is proposed that the observed electrophoretic and nephelometric behavior at high pH is due to flocculation of nanosized droplets to micron size, which eventually leads to droplets coalescing and emulsion destabilization. It is also postulated that the nano emulsion possess a critical dilution concentration (CDC), above which dilution leads to rapid coalescence. This critical dilution phase was further confirmed through polarity parameter and excimer formation studies which show significantly different polymer and surfactant microstructures near the CDC. Hence it is concluded that the observed surface properties of the substrate obtained above the CDC are significantly different than those below the CDC. The results reveal the vital role of physiochemical parameters such as pH, droplet size, and concentration on the emulsion stability as well as the observed physical/chemical properties of the substrates.

Substrate for thin silicon solar cells

DOEpatents

Ciszek, T.F.

1995-03-28

A photovoltaic device for converting solar energy into electrical signals comprises a substrate, a layer of photoconductive semiconductor material grown on said substrate, wherein the substrate comprises an alloy of boron and silicon, the boron being present in a range of from 0.1 to 1.3 atomic percent, the alloy having a lattice constant substantially matched to that of the photoconductive semiconductor material and a resistivity of less than 1{times}10{sup {minus}3} ohm-cm. 4 figures.

Measured Propagation Characteristics of Finite Ground Coplanar Waveguide on Silicon with a Thick Polyimide Interface Layer

NASA Technical Reports Server (NTRS)

Ponchak, George E.; Papapolymerou, John; Tentzeris, Emmanouil M.; Williams, W. O. (Technical Monitor)

2002-01-01

Measured propagation characteristics of Finite Ground Coplanar (FGC) waveguide on silicon substrates with resistivities spanning 3 orders of magnitude (0.1 to 15.5 Ohm cm) and a 20 micron thick polyimide interface layer is presented as a function of the FGC geometry. Results show that there is an optimum FGC geometry for minimum loss, and silicon with a resistivity of 0.1 Ohm cm has greater loss than substrates with higher and lower resistivity. Lastly, substrates with a resistivity of 10 Ohm cm or greater have acceptable loss.

Silicon-integrated thin-film structure for electro-optic applications

DOEpatents

McKee, Rodney A.; Walker, Frederick Joseph

2000-01-01

A crystalline thin-film structure suited for use in any of an number of electro-optic applications, such as a phase modulator or a component of an interferometer, includes a semiconductor substrate of silicon and a ferroelectric, optically-clear thin film of the perovskite BaTiO.sub.3 overlying the surface of the silicon substrate. The BaTiO.sub.3 thin film is characterized in that substantially all of the dipole moments associated with the ferroelectric film are arranged substantially parallel to the surface of the substrate to enhance the electro-optic qualities of the film.

Coated article and method of making

NASA Technical Reports Server (NTRS)

Wang, Hongyu (Inventor); Lee, Kang Neung (Inventor)

2003-01-01

An article includes a silicon-containing substrate and a modified mullite coating. The modified mullite coating comprises mullite and a modifier component that reduces cracks in the modified mullite coating. The article can further comprise a thermal barrier coating applied to the modified mullite coating. The modified mullite coating functions as a bond coating between the external environmental/thermal barrier coating and the silicon-containing substrate. In a method of forming an article, a silicon-containing substrate is formed and a modified mullite coating is applied. The modified mullite coating comprises mullite and a modifier component that reduces cracks in the modified mullite coating.

Coated article and method of making

NASA Technical Reports Server (NTRS)

Wang, Hongyu (Inventor); Lee, Kang Neung (Inventor)

2002-01-01

An article includes a silicon-containing substrate and a modified mullite coating. The modified mullite coating comprises mullite and a modifier component that reduces cracks in the modified mullite coating. The article can further comprise a thermal barrier coating applied to the modified mullite coating. The modified mullite coating functions as a bond coating between the external environmental/thermal barrier coating and the silicon-containing substrate. In a method of forming an article, a silicon-containing substrate is formed and a modified mullite coating is applied. The modified mullite coating comprises mullite and a modifier component that reduces cracks in the modified mullite coating.

RF Transmission Lines on Silicon Substrates

NASA Technical Reports Server (NTRS)

Ponchak, George E.

1999-01-01

A review of RF transmission lines on silicon substrates is presented. Through measurements and calculated results, it is shown that attenuation is dominated by conductor loss if silicon substrates with a resistivity greater than 2500 Ohm-cm are used. Si passivation layers affect the transmission line attenuation; however, measured results demonstrate that passivation layers do not necessarily increase attenuation. If standard, low resistivity Si wafers must be used, alternative transmission lines such as thin film microstrip and Co-Planar Waveguide (CPW) on thick polyimide layers must be used. Measured results presented here show that low loss per unit length is achievable with these transmission lines.

Charge-coupled device for low background observations

NASA Technical Reports Server (NTRS)

Loh, Edwin D. (Inventor); Cheng, Edward S. (Inventor)

2002-01-01

A charge-coupled device with a low-emissivity metal layer located between a sensing layer and a substrate provides reduction in ghost images. In a typical charge-coupled device of a silicon sensing layer, a silicon dioxide insulating layer, with a glass substrate and a metal carrier layer, a near-infrared photon, not absorbed in the first pass, enters the glass substrate, reflects from the metal carrier, thereby returning far from the original pixel in its entry path. The placement of a low-emissivity metal layer between the glass substrate and the sensing layer reflects near infrared photons before they reach the substrate so that they may be absorbed in the silicon nearer the pixel of their points of entry so that the reflected ghost image is coincident with the primary image for a sharper, brighter image.

High-alignment-accuracy transfer printing of passive silicon waveguide structures.

PubMed

Ye, Nan; Muliuk, Grigorij; Trindade, Antonio Jose; Bower, Chris; Zhang, Jing; Uvin, Sarah; Van Thourhout, Dries; Roelkens, Gunther

2018-01-22

We demonstrate the transfer printing of passive silicon devices on a silicon-on-insulator target waveguide wafer. Adiabatic taper structures and directional coupler structures were designed for 1310 nm and 1600 nm wavelength coupling tolerant for ± 1 µm misalignment. The release of silicon devices from the silicon substrate was realized by underetching the buried oxide layer while protecting the back-end stack. Devices were successfully picked by a PDMS stamp, by breaking the tethers that kept the silicon coupons in place on the source substrate, and printed with high alignment accuracy on a silicon photonic target wafer. Coupling losses of -1.5 +/- 0.5 dB for the adiabatic taper at 1310 nm wavelength and -0.5 +/- 0.5 dB for the directional coupler at 1600 nm wavelength are obtained.

Comparative study of initial stages of copper immersion deposition on bulk and porous silicon

NASA Astrophysics Data System (ADS)

Bandarenka, Hanna; Prischepa, Sergey L.; Fittipaldi, Rosalba; Vecchione, Antonio; Nenzi, Paolo; Balucani, Marco; Bondarenko, Vitaly

2013-02-01

Initial stages of Cu immersion deposition in the presence of hydrofluoric acid on bulk and porous silicon were studied. Cu was found to deposit both on bulk and porous silicon as a layer of nanoparticles which grew according to the Volmer-Weber mechanism. It was revealed that at the initial stages of immersion deposition, Cu nanoparticles consisted of crystals with a maximum size of 10 nm and inherited the orientation of the original silicon substrate. Deposited Cu nanoparticles were found to be partially oxidized to Cu2O while CuO was not detected for all samples. In contrast to porous silicon, the crystal orientation of the original silicon substrate significantly affected the sizes, density, and oxidation level of Cu nanoparticles deposited on bulk silicon.

Process for Polycrystalline film silicon growth

DOEpatents

Wang, Tihu; Ciszek, Theodore F.

2001-01-01

A process for depositing polycrystalline silicon on substrates, including foreign substrates, occurs in a chamber at about atmospheric pressure, wherein a temperature gradient is formed, and both the atmospheric pressure and the temperature gradient are maintained throughout the process. Formation of a vapor barrier within the chamber that precludes exit of the constituent chemicals, which include silicon, iodine, silicon diiodide, and silicon tetraiodide. The deposition occurs beneath the vapor barrier. One embodiment of the process also includes the use of a blanketing gas that precludes the entrance of oxygen or other impurities. The process is capable of repetition without the need to reset the deposition zone conditions.

Laser desorption ionization and peptide sequencing on laser induced silicon microcolumn arrays

DOEpatents

Vertes, Akos [Reston, VA; Chen, Yong [San Diego, CA

2011-12-27

The present invention provides a method of producing a laser-patterned silicon surface, especially silicon wafers for use in laser desorption ionization (LDI-MS) (including MALDI-MS and SELDI-MS), devices containing the same, and methods of testing samples employing the same. The surface is prepared by subjecting a silicon substrate to multiple laser shots from a high-power picosecond or femtosecond laser while in a processing environment, e.g., underwater, and generates a remarkable homogenous microcolumn array capable of providing an improved substrate for LDI-MS.

Low-cost solar array progress and plans

NASA Astrophysics Data System (ADS)

Callaghan, W. T.

It is pointed out that significant redirection has occurred in the U.S. Department of Energy (DOE) Photovoltaics Program, and thus in the Flat-Plate Solar Array Project (FSA), since the 3rd European Communities Conference. The Silicon Materials Task has now the objective to sponsor theoretical and experimental research on silicon material refinement technology suitable for photovoltaic flat-plate solar arrays. With respect to the hydrochlorination reaction, a process proof of concept was completed through definition of reaction kinetics, catalyst, and reaction characteristics. In connection with the dichlorosilane chemical vapor desposition process, a preliminary design was completed of an experimental process system development unit with a capacity of 100 to 200 MT/yr of Si.Attention is also given to the silicon-sheet formation research area, environmental isolation research, the cell and module formation task, the engineering sciences area, and the module performance and failure analysis area.

Infrared photocurrent management in monolithic perovskite/silicon heterojunction tandem solar cells by using a nanocrystalline silicon oxide interlayer.

PubMed

Mazzarella, Luana; Werth, Matteo; Jäger, Klaus; Jošt, Marko; Korte, Lars; Albrecht, Steve; Schlatmann, Rutger; Stannowski, Bernd

2018-05-14

We performed optical simulations using hydrogenated nanocrystalline silicon oxide (nc-SiO x :H) as n-doped interlayer in monolithic perovskite/c-Si heterojunction tandem solar cells. Depending on the adjustable value of its refractive index (2.0 - 2.7) and thickness, nc-SiO x :H allows to optically manage the infrared light absorption in the c-Si bottom cell minimizing reflection losses. We give guidelines for nc-SiO x :H optimization in tandem devices in combination with a systematic investigation of the effect of the surface morphology (flat or textured) on the photocurrent density. For full-flat and rear textured devices, we found matched photocurrents higher than 19 and 20 mA/cm 2 , respectively, using a 90 nm nc-SiO x :H interlayer with a refractive index of 2.7.

Proceedings of the Flat-Plate Solar Array Project Workshop on Crystal Gowth for High-Efficiency Silicon Solar Cells

NASA Technical Reports Server (NTRS)

Dumas, K. A. (Editor)

1985-01-01

A Workshop on Crystal Growth for High-Efficiency Silicon Solar Cells was held December 3 and 4, 1984, in San Diego, California. The Workshop offered a day and a half of technical presentations and discussions and an afternoon session that involved a panel discussion and general discussion of areas of research that are necessary to the development of materials for high-efficiency solar cells. Topics included the theoretical and experimental aspects of growing high-quality silicon crystals, the effects of growth-process-related defects on photovoltaic devices, and the suitability of various growth technologies as cost-effective processes. Fifteen invited papers were presented, with a discussion period following each presentation. The meeting was organized by the Flat-Plate Solar Array Project of the Jet Propulsion Laboratory. These Proceedings are a record of the presentations and discussions, edited for clarity and continuity.

Behavior of the potential-induced degradation of photovoltaic modules fabricated using flat mono-crystalline silicon cells with different surface orientations

NASA Astrophysics Data System (ADS)

Yamaguchi, Seira; Masuda, Atsushi; Ohdaira, Keisuke

2016-04-01

This paper deals with the dependence of the potential-induced degradation (PID) of flat, p-type mono-crystalline silicon solar cell modules on the surface orientation of solar cells. The investigated modules were fabricated from p-type mono-crystalline silicon cells with a (100) or (111) surface orientation using a module laminator. PID tests were performed by applying a voltage of -1000 V to shorted module interconnector ribbons with respect to an Al plate placed on the cover glass of the modules at 85 °C. A decrease in the parallel resistance of the (100)-oriented cell modules is more significant than that of the (111)-oriented cell modules. Hence, the performance of the (100)-oriented-cell modules drastically deteriorates, compared with that of the (111)-oriented-cell modules. This implies that (111)-oriented cells offer a higher PID resistance.

High-T(sub c) Edge-geometry SNS Weak Links on Silicon-on-sapphire Substrates

NASA Technical Reports Server (NTRS)

Hunt, B.; Foote, M.; Pike, W.; Barner, J.; Vasquez, R.

1994-01-01

High-quality superconductor/normal-metal/superconductor(SNS) edge-geometry weak links have been produced on silicon-on-sapphire (SOS) substrates using a new SrTiO(sub 3)/'seed layer'/cubic-zirconia (YS2) buffer system.

Electron beam recrystallization of amorphous semiconductor materials

NASA Technical Reports Server (NTRS)

Evans, J. C., Jr.

1968-01-01

Nucleation and growth of crystalline films of silicon, germanium, and cadmium sulfide on substrates of plastic and glass were investigated. Amorphous films of germanium, silicon, and cadmium sulfide on amorphous substrates of glass and plastic were converted to the crystalline condition by electron bombardment.

Transparent conducting oxide contacts and textured metal back reflectors for thin film silicon solar cells

NASA Astrophysics Data System (ADS)

Franken, R. H.-J.

2006-09-01

With the growing population and the increasing environmental problems of the 'common' fossil and nuclear energy production, the need for clean and sustainable energy sources is evident. Solar energy conversion, such as in photovoltaic (PV) systems, can play a major role in the urgently needed energy transition in electricity production. At the present time PV module production is dominated by the crystalline wafer technology. Thin film silicon technology is an alternative solar energy technology that operates at lower efficiencies, however, it has several significant advantages, such as the possibility of deposition on cheap (flexible) substrates and the much smaller silicon material consumption. Because of the small thickness of the solar cells, light trapping schemes are needed in order to obtain enough light absorption and current generation. This thesis describes the research on thin film silicon solar cells with the focus on the optimization of the transparent conducting oxide (TCO) layers and textured metal Ag substrate layers for the use as enhanced light scattering back reflectors in n-i-p type of solar cells. First we analyzed ZnO:Al (TCO) layers deposited in an radio frequent (rf) magnetron deposition system equipped with a 7 inch target. We have focused on the improvement of the electrical properties without sacrificing the optical properties by increasing the mobility and decreasing the grain boundary density. Furthermore, we described some of the effects on light trapping of ZnO:Al enhanced back reflectors. The described effects are able to explain the observed experimental data. Furthermore, we present a relation between the surface morphology of the Ag back contact and the current enhancement in microcrystalline (muc-Si:H) solar cells. We show the importance of the lateral feature sizes of the Ag surface on the light scattering and introduce a method to characterize the quality of the back reflector by combining the vertical and lateral feature sizes at this surface. Additionally, we show that we can control the lateral feature sizes and obtain an optimized roughness for light scattering. With this new knowledge we were able to indicate the influence of the surface plasmon absorption of the textured Ag layers on the current enhancement and recognize this effect as one of the limiting factors to the current increase in thin film solar cells. Finally we present the dark and light current voltage (J-V) parameters of muc-Si:H solar cells as a function of the rms roughness of the substrate. We show that increased roughness can result in an increased defect density of the absorbing silicon layer (i layer), which limits the current collection in the solar cell. The presented research gives better understanding of the effect of TCOs and textured interfaces on light trapping and current enhancement in thin film silicon solar cells. The thesis explains some fundamental insights in light scattering and reveals some material and morphology features that are dominantly limiting the current generation in muc-Si:H solar cells deposited on light scattering back reflectors. Furthermore, it presents a method to obtain optimized back scattering contacts at deposition temperatures below 300 oC, which opens the possibility for the use of heat resistant plastic substrates. We improved the muc-Si:H solar cell efficiency with flat back reflectors from 4.5 % and 14.6 mA/cm2 to 8.5 % and 23.4 mA/cm2 with the use of optimized back reflectors.

Influence of design variables on radiation hardness of silicon MINP solar cells

NASA Technical Reports Server (NTRS)

Anderson, W. A.; Solaun, S.; Rao, B. B.; Banerjee, S.

1985-01-01

Metal-insulator-N/P silicon (MINP) solar cells were fabricated using different substrate resistivity values, different N-layer designs, and different I-layer designs. A shallow junction into an 0.3 ohm-cm substrate gave best efficiency whereas a deeper junction into a 1 to 4 ohm-cm substrate gave improved radiation hardness. I-layer design variation did little to influence radiation hardness.

Environmental barrier coating

DOEpatents

Pujari, Vimal K.; Vartabedian, Ara; Collins, William T.; Woolley, David; Bateman, Charles

2012-12-18

The present invention relates generally to a multi-layered article suitable for service in severe environments. The article may be formed of a substrate, such as silicon carbide and/or silicon nitride. The substrate may have a first layer of a mixture of a rare earth silicate and Cordierite. The substrate may also have a second layer of a rare earth silicate or a mixture of a rare earth silicate and cordierite.

Development of Mullite Substrates and Containers

NASA Technical Reports Server (NTRS)

Sibold, J. D.

1979-01-01

The mullite-molten silicon interaction was evaluated through fabrication of a series of bodies made with variations in density, alumina-silica ratio, and glass-crystalline ratio. The materials were tested in a sessile drop technique. None of the variations stood up to extended exposure to molten silicon sufficiently to be recommended as a container material. However, directional solidification experiments suggest that, under proper conditions, contamination of the silicon by mullite containers can be minimized. To improve an already good thermal expansion match between mullite and silicon, compositional variations were studied. Altering of the alumina-silica ratio was determined to give a continuously varying thermal expansion. A standard mullite composition was selected and substrates 40 x 4 x .040 inches were fabricated. Slotted substrates of various configurations and various compositions were also fabricated.

Vertical group III-V nanowires on si, heterostructures, flexible arrays and fabrication

DOEpatents

Wang, Deli; Soci, Cesare; Bao, Xinyu; Wei, Wei; Jing, Yi; Sun, Ke

2015-01-13

Embodiments of the invention provide a method for direct heteroepitaxial growth of vertical III-V semiconductor nanowires on a silicon substrate. The silicon substrate is etched to substantially completely remove native oxide. It is promptly placed in a reaction chamber. The substrate is heated and maintained at a growth temperature. Group III-V precursors are flowed for a growth time. Preferred embodiment vertical Group III-V nanowires on silicon have a core-shell structure, which provides a radial homojunction or heterojunction. A doped nanowire core is surrounded by a shell with complementary doping. Such can provide high optical absorption due to the long optical path in the axial direction of the vertical nanowires, while reducing considerably the distance over which carriers must diffuse before being collected in the radial direction. Alloy composition can also be varied. Radial and axial homojunctions and heterojunctions can be realized. Embodiments provide for flexible Group III-V nanowire structures. An array of Group III-V nanowire structures is embedded in polymer. A fabrication method forms the vertical nanowires on a substrate, e.g., a silicon substrate. Preferably, the nanowires are formed by the preferred methods for fabrication of Group III-V nanowires on silicon. Devices can be formed with core/shell and core/multi-shell nanowires and the devices are released from the substrate upon which the nanowires were formed to create a flexible structure that includes an array of vertical nanowires embedded in polymer.

Investigation of ZnSe-coated silicon substrates for GaAs solar cells

NASA Technical Reports Server (NTRS)

Huber, Daniel A.; Olsen, Larry C.; Dunham, Glen; Addis, F. William

1993-01-01

Studies are being carried out to determine the feasibility of using ZnSe as a buffer layer for GaAs solar cells grown on silicon. This study was motivated by reports in the literature indicating ZnSe films had been grown by metallorganic chemical vapor deposition (MOCVD) onto silicon with EPD values of 2 x 10(exp 5) cm(sup -2), even though the lattice mismatch between silicon and ZnSe is 4.16 percent. These results combined with the fact that ZnSe and GaAs are lattice matched to within 0.24 percent suggest that the prospects for growing high efficiency GaAs solar cells onto ZnSe-coated silicon are very good. Work to date has emphasized development of procedures for MOCVD growth of (100) ZnSe onto (100) silicon wafers, and subsequent growth of GaAs films on ZnSe/Si substrates. In order to grow high quality single crystal GaAs with a (100) orientation, which is desirable for solar cells, one must grow single crystal (100) ZnSe onto silicon substrates. A process for growth of (100) ZnSe was developed involving a two-step growth procedure at 450 C. Single crystal, (100) GaAs films were grown onto the (100) ZnSe/Si substrates at 610 C that are adherent and specular. Minority carrier diffusion lengths for the GaAs films grown on ZnSe/Si substrates were determined from photoresponse properties of Al/GaAs Schottky barriers. Diffusion lengths for n-type GaAs films are currently on the order of 0.3 microns compared to 2.0 microns for films grown simultaneously by homoepitaxy.

Ion irradiation of the native oxide/silicon surface increases the thermal boundary conductance across aluminum/silicon interfaces

NASA Astrophysics Data System (ADS)

Gorham, Caroline S.; Hattar, Khalid; Cheaito, Ramez; Duda, John C.; Gaskins, John T.; Beechem, Thomas E.; Ihlefeld, Jon F.; Biedermann, Laura B.; Piekos, Edward S.; Medlin, Douglas L.; Hopkins, Patrick E.

2014-07-01

The thermal boundary conductance across solid-solid interfaces can be affected by the physical properties of the solid boundary. Atomic composition, disorder, and bonding between materials can result in large deviations in the phonon scattering mechanisms contributing to thermal boundary conductance. Theoretical and computational studies have suggested that the mixing of atoms around an interface can lead to an increase in thermal boundary conductance by creating a region with an average vibrational spectra of the two materials forming the interface. In this paper, we experimentally demonstrate that ion irradiation and subsequent modification of atoms at solid surfaces can increase the thermal boundary conductance across solid interfaces due to a change in the acoustic impedance of the surface. We measure the thermal boundary conductance between thin aluminum films and silicon substrates with native silicon dioxide layers that have been subjected to proton irradiation and post-irradiation surface cleaning procedures. The thermal boundary conductance across the Al/native oxide/Si interfacial region increases with an increase in proton dose. Supported with statistical simulations, we hypothesize that ion beam mixing of the native oxide and silicon substrate within ˜2.2nm of the silicon surface results in the observed increase in thermal boundary conductance. This ion mixing leads to the spatial gradation of the silicon native oxide into the silicon substrate, which alters the acoustic impedance and vibrational characteristics at the interface of the aluminum film and native oxide/silicon substrate. We confirm this assertion with picosecond acoustic analyses. Our results demonstrate that under specific conditions, a "more disordered and defected" interfacial region can have a lower resistance than a more "perfect" interface.

Deposition of hydrogenated silicon clusters for efficient epitaxial growth.

PubMed

Le, Ha-Linh Thi; Jardali, Fatme; Vach, Holger

2018-06-13

Epitaxial silicon thin films grown from the deposition of plasma-born hydrogenated silicon nanoparticles using plasma-enhanced chemical vapor deposition have widely been investigated due to their potential applications in photovoltaic and nanoelectronic device technologies. However, the optimal experimental conditions and the underlying growth mechanisms leading to the high-speed epitaxial growth of thin silicon films from hydrogenated silicon nanoparticles remain far from being understood. In the present work, extensive molecular dynamics simulations were performed to study the epitaxial growth of silicon thin films resulting from the deposition of plasma-born hydrogenated silicon clusters at low substrate temperatures under realistic reactor conditions. There is strong evidence that a temporary phase transition of the substrate area around the cluster impact site to the liquid state is necessary for the epitaxial growth to take place. We predict further that a non-normal incidence angle for the cluster impact significantly facilitates the epitaxial growth of thin crystalline silicon films.

Formation of microchannels from low-temperature plasma-deposited silicon oxynitride

DOEpatents

Matzke, Carolyn M.; Ashby, Carol I. H.; Bridges, Monica M.; Manginell, Ronald P.

2000-01-01

A process for forming one or more fluid microchannels on a substrate is disclosed that is compatible with the formation of integrated circuitry on the substrate. The microchannels can be formed below an upper surface of the substrate, above the upper surface, or both. The microchannels are formed by depositing a covering layer of silicon oxynitride over a mold formed of a sacrificial material such as photoresist which can later be removed. The silicon oxynitride is deposited at a low temperature (.ltoreq.100.degree. C.) and preferably near room temperature using a high-density plasma (e.g. an electron-cyclotron resonance plasma or an inductively-coupled plasma). In some embodiments of the present invention, the microchannels can be completely lined with silicon oxynitride to present a uniform material composition to a fluid therein. The present invention has applications for forming microchannels for use in chromatography and electrophoresis. Additionally, the microchannels can be used for electrokinetic pumping, or for localized or global substrate cooling.

Ablative performance of uncoated silicone-modified and shuttle baseline reinforced carbon composites

NASA Technical Reports Server (NTRS)

Dicus, D. L.; Hopko, R. N.; Brown, R. D.

1976-01-01

The relative ablative performance of uncoated silicone-modified reinforced carbon composite (RCC) and uncoated shuttle baseline RCC substrates was investigated. The test specimens were 13 plies (5.3 to 5.8 millimeters) thick and had a 25-millimeter-diameter test face. Prior to arc tunnel testing, all specimens were subjected to a heat treatment simulating the RCC coating process. During arc tunnel testing, the specimens were exposed to cold wall heating rates of 178 to 529 kilowatts/sq m and stagnation pressures ranging from 0.015 to 0.046 atmosphere at Mach 4.6 in air, with and without preheating in nitrogen. The results show that the ablative performance of uncoated silicone-modified RCC substrates is significantly superior to that of uncoated shuttle baseline RCC substrates over the range of heating conditions used. These results indicate that the silicone-modified RCC substrate would yield a substantially greater safety margin in the event of complete coating loss on the shuttle orbiter.

Profilometry of thin films on rough substrates by Raman spectroscopy

PubMed Central

Ledinský, Martin; Paviet-Salomon, Bertrand; Vetushka, Aliaksei; Geissbühler, Jonas; Tomasi, Andrea; Despeisse, Matthieu; De Wolf , Stefaan; Ballif , Christophe; Fejfar, Antonín

2016-01-01

Thin, light-absorbing films attenuate the Raman signal of underlying substrates. In this article, we exploit this phenomenon to develop a contactless thickness profiling method for thin films deposited on rough substrates. We demonstrate this technique by probing profiles of thin amorphous silicon stripes deposited on rough crystalline silicon surfaces, which is a structure exploited in high-efficiency silicon heterojunction solar cells. Our spatially-resolved Raman measurements enable the thickness mapping of amorphous silicon over the whole active area of test solar cells with very high precision; the thickness detection limit is well below 1 nm and the spatial resolution is down to 500 nm, limited only by the optical resolution. We also discuss the wider applicability of this technique for the characterization of thin layers prepared on Raman/photoluminescence-active substrates, as well as its use for single-layer counting in multilayer 2D materials such as graphene, MoS2 and WS2. PMID:27922033

RF sputtered silicon and hafnium nitrides as applied to 440C steel

NASA Technical Reports Server (NTRS)

Grill, A.; Aron, P. R.

1984-01-01

Silicon nitride and hafnium nitride coatings were deposited on oxidized and unoxidized 440C stainless steel substrates. Sputtering was done in mixtures of argon and nitrogen gases from pressed powder silicon nitride and from hafnium metal targets. The coatings and the interface between the coating and substrate were investigated by X-ray diffractometry, scanning electron microscopy, energy dispersive X-ray analysis and Auger electron spectroscopy. Oxide was found at all interfaces with an interface width of at least 600 A for the oxidized substrates and at least 300 A for the unoxidized substrates. Scratch test results demonstrate that the adhesion of hafnium nitride to both oxidized and unoxidized 440C is superior to that of silicon nitride. Oxidized 440C is found to have increased adhesion, to both nitrides, over that of unoxidized 440C. Coatings of both nitrides deposited at 8 mtorr were found to have increased adhesion to both oxidized and unoxidized 440C over those deposited at 20 mtorr.

Plasmonic and silicon spherical nanoparticle antireflective coatings

NASA Astrophysics Data System (ADS)

Baryshnikova, K. V.; Petrov, M. I.; Babicheva, V. E.; Belov, P. A.

2016-03-01

Over the last decade, plasmonic antireflecting nanostructures have been extensively studied to be utilized in various optical and optoelectronic systems such as lenses, solar cells, photodetectors, and others. The growing interest to all-dielectric photonics as an alternative optical technology along with plasmonics motivates us to compare antireflective properties of plasmonic and all-dielectric nanoparticle coatings based on silver and crystalline silicon respectively. Our simulation results for spherical nanoparticles array on top of amorphous silicon show that both silicon and silver coatings demonstrate strong antireflective properties in the visible spectral range. For the first time, we show that zero reflectance from the structure with silicon coatings originates from the destructive interference of electric- and magnetic-dipole responses of nanoparticle array with the wave reflected from the substrate, and we refer to this reflection suppression as substrate-mediated Kerker effect. We theoretically compare the silicon and silver coating effectiveness for the thin-film photovoltaic applications. Silver nanoparticles can be more efficient, enabling up to 30% increase of the overall absorbance in semiconductor layer. Nevertheless, silicon coatings allow up to 64% absorbance increase in the narrow band spectral range because of the substrate-mediated Kerker effect, and band position can be effectively tuned by varying the nanoparticles sizes.

Plasmonic and silicon spherical nanoparticle antireflective coatings

PubMed Central

Baryshnikova, K. V.; Petrov, M. I.; Babicheva, V. E.; Belov, P. A.

2016-01-01

Over the last decade, plasmonic antireflecting nanostructures have been extensively studied to be utilized in various optical and optoelectronic systems such as lenses, solar cells, photodetectors, and others. The growing interest to all-dielectric photonics as an alternative optical technology along with plasmonics motivates us to compare antireflective properties of plasmonic and all-dielectric nanoparticle coatings based on silver and crystalline silicon respectively. Our simulation results for spherical nanoparticles array on top of amorphous silicon show that both silicon and silver coatings demonstrate strong antireflective properties in the visible spectral range. For the first time, we show that zero reflectance from the structure with silicon coatings originates from the destructive interference of electric- and magnetic-dipole responses of nanoparticle array with the wave reflected from the substrate, and we refer to this reflection suppression as substrate-mediated Kerker effect. We theoretically compare the silicon and silver coating effectiveness for the thin-film photovoltaic applications. Silver nanoparticles can be more efficient, enabling up to 30% increase of the overall absorbance in semiconductor layer. Nevertheless, silicon coatings allow up to 64% absorbance increase in the narrow band spectral range because of the substrate-mediated Kerker effect, and band position can be effectively tuned by varying the nanoparticles sizes. PMID:26926602

Evaluation of the Effect of Silicone Contamination on Various Bond Systems and the Feasibility of Removing the Contamination

NASA Technical Reports Server (NTRS)

Stanley, Stephanie D.

2008-01-01

Silicone is a contaminant that can cause catastrophic failure of a bond system depending on the materials and processes used to fabricate the bond system, Unfortunately, more and more materials are fabricated using silicone. The purpose of this testing was to evaluate which bond systems are sensitive to silicone contamination and whether or not a cleaning process could be utilized to remove the silicone to bring the bond system performance back to baseline. Due to the extensive nature of the testing attempts will be made to generalize the understanding within classes of substrates, bond systems, and surface preparation and cleaning methods. This study was done by contaminating various meta! (steel, inconel, and aluminum), phenolic (carbon cloth phenolic and glass cloth phenolic), and rubber (natural rubber, asbestos-silicone dioxide filled natural butyldiene rubber, silica-filled ethylene propylenediene monomer, and carbon-filled ethylene propylenediene monomer) substrates which were then bonded using various adhesives and coatings (epoxy-based adhesives, paints, ablative compounds, and Chemlok adhesives) to determine the effect silicone contamination has on a given bond system's performance. The test configurations depended on the bond system being evaluated. The study also evaluated the feasibility of removing the silicone contamination by cleaning the contaminated substrate prior to bonding. The cleaning processes also varied depending on bond system.

In situ micro-Raman analysis and X-ray diffraction of nickel silicide thin films on silicon.

PubMed

Bhaskaran, M; Sriram, S; Perova, T S; Ermakov, V; Thorogood, G J; Short, K T; Holland, A S

2009-01-01

This article reports on the in situ analysis of nickel silicide (NiSi) thin films formed by thermal processing of nickel thin films deposited on silicon substrates. The in situ techniques employed for this study include micro-Raman spectroscopy (microRS) and X-ray diffraction (XRD); in both cases the variations for temperatures up to 350 degrees C has been studied. Nickel silicide thin films formed by vacuum annealing of nickel on silicon were used as a reference for these measurements. In situ analysis was carried out on nickel thin films on silicon, while the samples were heated from room temperature to 350 degrees C. Data was gathered at regular temperature intervals and other specific points of interest (such as 250 degrees C, where the reaction between nickel and silicon to form Ni(2)Si is expected). The transformations from the metallic state, through the intermediate reaction states, until the desired metal-silicon reaction product is attained, are discussed. The evolution of nickel silicide from the nickel film can be observed from both the microRS and XRD in situ studies. Variations in the evolution of silicide from metal for different silicon substrates are discussed, and these include (100) n-type, (100) p-type, and (110) p-type silicon substrates.

Rapid Covalent Modification of Silicon Oxide Surfaces through Microwave-Assisted Reactions with Alcohols.

PubMed

Lee, Austin W H; Gates, Byron D

2016-07-26

We demonstrate the method of a rapid covalent modification of silicon oxide surfaces with alcohol-containing compounds with assistance by microwave reactions. Alcohol-containing compounds are prevalent reagents in the laboratory, which are also relatively easy to handle because of their stability against exposure to atmospheric moisture. The condensation of these alcohols with the surfaces of silicon oxides is often hindered by slow reaction kinetics. Microwave radiation effectively accelerates this condensation reaction by heating the substrates and/or solvents. A variety of substrates were modified in this demonstration, such as silicon oxide films of various thicknesses, glass substrates such as microscope slides (soda lime), and quartz. The monolayers prepared through this strategy demonstrated the successful formation of covalent surface modifications of silicon oxides with water contact angles of up to 110° and typical hysteresis values of 2° or less. An evaluation of the hydrolytic stability of these monolayers demonstrated their excellent stability under acidic conditions. The techniques introduced in this article were successfully applied to tune the surface chemistry of silicon oxides to achieve hydrophobic, oleophobic, and/or charged surfaces.

Regenerator seal

DOEpatents

Davis, Leonard C.; Pacala, Theodore; Sippel, George R.

1981-01-01

A method for manufacturing a hot side regenerator cross arm seal assembly having a thermally stablilized wear coating with a substantially flat wear surface thereon to seal between low pressure and high pressure passages to and from the hot inboard side of a rotary regenerator matrix includes the steps of forming a flat cross arm substrate member of high nickel alloy steel; fixedly securing the side edges of the substrate member to a holding fixture with a concave surface thereacross to maintain the substrate member to a slightly bent configuration on the fixture surface between the opposite ends of the substrate member to produce prestress therein; applying coating layers on the substrate member including a wear coating of plasma sprayed nickel oxide/calcium flouride material to define a wear surface of slightly concave form across the restrained substrate member between the free ends thereon; and thereafter subjecting the substrate member and the coating thereon to a heat treatment of 1600.degree. F. for sixteen hours to produce heat stabilizing growth in the coating layers on the substrate member and to produce a thermally induced growth stress in the wear surface that substantially equalizes the prestress in the substrate whereby when the cross arm is removed from the fixture surface following the heat treatment step a wear face is formed on the cross arm assembly that will be substantially flat between the ends.

Monitoring transients in low inductance circuits

DOEpatents

Guilford, Richard P.; Rosborough, John R.

1987-01-01

A pair of flat cable transmission lines are monitored for transient current spikes by using a probe connected to a current transformer by a pickup loop and monitoring the output of the current transformer. The approach utilizes a U-shaped pickup probe wherein the pair of flat cable transmission lines are received between the legs of the U-shaped probe. The U-shaped probe is preferably formed of a flat coil conductor adhered to one side of a flexible substrate. On the other side of the flexible substrate there is a copper foil shield. The copper foil shield is connected to one end of the flat conductor coil and connected to one leg of the pickup loop which passes through the current transformer. The other end of the flat conductor coil is connected to the other leg of the pickup loop.

Mechanically flexible optically transparent silicon fabric with high thermal budget devices from bulk silicon (100)

NASA Astrophysics Data System (ADS)

Hussain, Muhammad M.; Rojas, Jhonathan P.; Torres Sevilla, Galo A.

2013-05-01

Today's information age is driven by silicon based electronics. For nearly four decades semiconductor industry has perfected the fabrication process of continuingly scaled transistor - heart of modern day electronics. In future, silicon industry will be more pervasive, whose application will range from ultra-mobile computation to bio-integrated medical electronics. Emergence of flexible electronics opens up interesting opportunities to expand the horizon of electronics industry. However, silicon - industry's darling material is rigid and brittle. Therefore, we report a generic batch fabrication process to convert nearly any silicon electronics into a flexible one without compromising its (i) performance; (ii) ultra-large-scale-integration complexity to integrate billions of transistors within small areas; (iii) state-of-the-art process compatibility, (iv) advanced materials used in modern semiconductor technology; (v) the most widely used and well-studied low-cost substrate mono-crystalline bulk silicon (100). In our process, we make trenches using anisotropic reactive ion etching (RIE) in the inactive areas (in between the devices) of a silicon substrate (after the devices have been fabricated following the regular CMOS process), followed by a dielectric based spacer formation to protect the sidewall of the trench and then performing an isotropic etch to create caves in silicon. When these caves meet with each other the top portion of the silicon with the devices is ready to be peeled off from the bottom silicon substrate. Release process does not need to use any external support. Released silicon fabric (25 μm thick) is mechanically flexible (5 mm bending radius) and the trenches make it semi-transparent (transparency of 7%).

Some material structural properties of SOI substrates produced by SDB technology

NASA Astrophysics Data System (ADS)

Hui, Li; Guo-Liang, Sun; Juan, Zhan; Qin-Yi, Tong

1987-10-01

SOI substrates have been produced by silicon direct bonding (SDB) technology. Thermal oxides ranging in thickness from native oxide to 1 μm or even more, on either or both wafers have been bonded successfully. The fracture strength of the SOI layer is 130-200 kg/cm 2 which is similar to the value of intrinsic bulk silicon. Dislocations have been shown to be concentrated on the backsides of the substrate and no additional defects have been developed within 80 μm of the Si-SiO 2 bonding area. Mobility and minority carrier lifetime similar to that of the original bulk silicon have been obtained after annealing.

Efficient Surface Enhanced Raman Scattering substrates from femtosecond laser based fabrication

NASA Astrophysics Data System (ADS)

Parmar, Vinod; Kanaujia, Pawan K.; Bommali, Ravi Kumar; Vijaya Prakash, G.

2017-10-01

A fast and simple femtosecond laser based methodology for efficient Surface Enhanced Raman Scattering (SERS) substrate fabrication has been proposed. Both nano scaffold silicon (black silicon) and gold nanoparticles (Au-NP) are fabricated by femtosecond laser based technique for mass production. Nano rough silicon scaffold enables large electromagnetic fields for the localized surface plasmons from decorated metallic nanoparticles. Thus giant enhancement (approximately in the order of 104) of Raman signal arises from the mixed effects of electron-photon-phonon coupling, even at nanomolar concentrations of test organic species (Rhodamine 6G). Proposed process demonstrates the low-cost and label-less application ability from these large-area SERS substrates.

Deposition of device quality, low hydrogen content, hydrogenated amorphous silicon at high deposition rates with increased stability using the hot wire filament technique

DOEpatents

Molenbroek, Edith C.; Mahan, Archie Harvin; Gallagher, Alan C.

2000-09-26

A method or producing hydrogenated amorphous silicon on a substrate, comprising the steps of: positioning the substrate in a deposition chamber at a distance of about 0.5 to 3.0 cm from a heatable filament in the deposition chamber; maintaining a pressure in said deposition chamber in the range of about 10 to 100 millitorr and pressure times substrate-filament spacing in the range of about 10 to 100 millitorr-cm, heating the filament to a temperature in the range of about 1,500 to 2,000.degree. C., and heating the substrate to a surface temperature in the range of about 280 to 475.degree. C.; and flowing silicohydride gas into the deposition chamber with said heated filament, decomposing said silicohydride gas into silicon and hydrogen atomic species and allowing products of gas reactions between said atomic species and the silicohydride gas to migrate to and deposit on said substrate while adjusting and maintaining said pressure times substrate-filament spacing in said deposition chamber at a value in said 10 to 100 millitorr range to produce statistically about 3 to 50 atomic collisions between the silicon and hydrogen atomic species migrating to said substrate and undecomposed molecules of the silane or other silicohydride gas in the deposition chamber.

Atomically flat platinum films grown on synthetic mica

NASA Astrophysics Data System (ADS)

Tanaka, Hiroyuki; Taniguchi, Masateru

2018-04-01

Atomically flat platinum thin films were heteroepitaxially grown on synthetic fluorophlogopite mica [KMg3(AlSi3O10)F2] by van der Waals epitaxy. Platinum films deposited on a fluorophlogopite mica substrate by inductively coupled plasma-assisted sputtering with oxygen introduction on a synthetic mica substrate resulted in the growth of twin single-crystalline epitaxial Pt(111) films.

Vacuum die attach for integrated circuits

DOEpatents

Schmitt, E.H.; Tuckerman, D.B.

1991-09-10

A thin film eutectic bond for attaching an integrated circuit die to a circuit substrate is formed by coating at least one bonding surface on the die and substrate with an alloying metal, assembling the die and substrate under compression loading, and heating the assembly to an alloying temperature in a vacuum. A very thin bond, 10 microns or less, which is substantially void free, is produced. These bonds have high reliability, good heat and electrical conduction, and high temperature tolerance. The bonds are formed in a vacuum chamber, using a positioning and loading fixture to compression load the die, and an IR lamp or other heat source. For bonding a silicon die to a silicon substrate, a gold silicon alloy bond is used. Multiple dies can be bonded simultaneously. No scrubbing is required. 1 figure.

Vacuum die attach for integrated circuits

DOEpatents

Schmitt, Edward H.; Tuckerman, David B.

1991-01-01

A thin film eutectic bond for attaching an integrated circuit die to a circuit substrate is formed by coating at least one bonding surface on the die and substrate with an alloying metal, assembling the die and substrate under compression loading, and heating the assembly to an alloying temperature in a vacuum. A very thin bond, 10 microns or less, which is substantially void free, is produced. These bonds have high reliability, good heat and electrical conduction, and high temperature tolerance. The bonds are formed in a vacuum chamber, using a positioning and loading fixture to compression load the die, and an IR lamp or other heat source. For bonding a silicon die to a silicon substrate, a gold silicon alloy bond is used. Multiple dies can be bonded simultaneously. No scrubbing is required.

Method of making a ceramic with preferential oxygen reactive layer

NASA Technical Reports Server (NTRS)

Wang, Hongyu (Inventor); Luthra, Krishan Lal (Inventor)

2003-01-01

A method of forming an article. The method comprises forming a silicon-based substrate that is oxidizable by reaction with an oxidant to form at least one gaseous product and applying an intermediate layer/coating onto the substrate, wherein the intermediate layer/coating is oxidizable to a nongaseous product by reaction with the oxidant in preference to reaction of the silicon-containing substrate with the oxidant.

Formation of thin-film resistors on silicon substrates

DOEpatents

Schnable, George L.; Wu, Chung P.

1988-11-01

The formation of thin-film resistors by the ion implantation of a metallic conductive layer in the surface of a layer of phosphosilicate glass or borophosphosilicate glass which is deposited on a silicon substrate. The metallic conductive layer materials comprise one of the group consisting of tantalum, ruthenium, rhodium, platinum and chromium silicide. The resistor is formed and annealed prior to deposition of metal, e.g. aluminum, on the substrate.

NT-SiC (new-technology silicon carbide) : Φ 650mm optical space mirror substrate of high-strength reaction-sintered silicon carbide

NASA Astrophysics Data System (ADS)

Suyama, Shoko; Itoh, Yoshiyasu; Tsuno, Katsuhiko; Ohno, Kazuhiko

2005-08-01

Silicon carbide (SiC) is the most advantageous as the material of various telescope mirrors, because of high stiffness, low density, low coefficient of thermal expansion, high thermal conductivity and thermal stability. Newly developed high-strength reaction-sintered silicon carbide (NTSIC), which has two times higher strength than sintered SiC, is one of the most promising candidates for lightweight optical mirror substrate, because of fully dense, lightweight, small sintering shrinkage (+/-1 %), good shape capability and low processing temperature. In this study, 650mm in diameter mirror substrate of NTSIC was developed for space telescope applications. Three developed points describe below. The first point was to realize the lightweight to thin the thickness of green bodies. Ribs down to 3mm thickness can be obtained by strengthen the green body. The second point was to enlarge the mirror size. 650mm in diameter of mirror substrate can be fabricated with enlarging the diameter in order. The final point was to realize the homogeneity of mirror substrate. Some properties, such as density, bending strength, coefficient of thermal expansion, Young's modulus, Poisson's ratio, fracture toughness, were measured by the test pieces cutting from the fabricated mirror substrates.

Silicon accumulation and distribution in petunia and sunflower

USDA-ARS?s Scientific Manuscript database

Silicon (Si) is a beneficial element that has been shown to protect plants during periods of abiotic and biotic stress. Plant-available Si can be supplied through substrate components, substrate amendments, liquid fertilization, or foliar sprays. The objective of this study was to compare Si accum...

Microdynamic Devices Fabricated on Silicon-On-Sapphire Substrates.

DTIC Science & Technology

Silicon-on-sapphire substrates are provided for the fabrication of micromechanical devices, such as micromotors . The high voltage stand-off...a consequence, the electrostatically driven devices, micromotors , can be incorporated in the integrated circuits and yet be powered at elevated voltages to increase their work potential.

Method of forming silicon structures with selectable optical characteristics

NASA Technical Reports Server (NTRS)

Fathauer, Robert W. (Inventor); Schowalter, Leo (Inventor)

1993-01-01

Silicon and metal are coevaporated onto a silicon substrate in a molecular beam epitaxy system with a larger than stoichiometric amount of silicon so as to epitaxially grow particles of metal silicide embedded in a matrix of single crystal epitaxially grown silicon. The particles interact with incident photons by resonant optical absorption at the surface plasmon resonance frequency. Controlling the substrate temperature and deposition rate and time allows the aspect ratio of the particles to be tailored to desired wavelength photons and polarizations. The plasmon energy may decay as excited charge carriers or phonons, either of which can be monitored to indicate the amount of incident radiation at the selected frequency and polarization.

Correlation of 150-mm silicon wafer site flatness with stepper performance for deep submicron applications

NASA Astrophysics Data System (ADS)

Huff, Howard R.; Vigil, Joseph C.; Kuyel, Birol; Chan, David Y.; Nguyen, Long P.

1992-06-01

An experimental study was conducted to correlate wafer site flatness SFQD with stepper performance for half-micron lines and spaces. CD measurements were taken on wafers patterned on both GCA pre-production XLS i-line and SVGL Micrascan-90 DUV steppers as well as focus measurements on the Micrascan-90. Wafer site flatness SFQD less than 0.3 micrometers was observed to be a sufficiently small variable in CD non-uniformities for these initial half-micron stepper applications.

Investigation of sacrificial layer and building block for layered nanofabrication (LNF)

NASA Astrophysics Data System (ADS)

Shih, Ting-Yu

Layered Nanoscale Fabrication (LNF) is a "bottom-up" procedure that uses multiple layers to build 3-dimensional nanoscale structures. Here, in this dissertation, several candidates for sacrificial layers were explored, The thermal stability of gold nanoparticles and simple patterns are also reported. In order to obtain information on layer thickness and film quality; the samples were characterized using atomic force microscopy (AFM) and ellipsometry. Octadecyltrichlorosilane (OTS) was first investigated for use as a sacrificial layer and we studied filth growth by targeted self-replication of silane multilayers with and without the presence of thiolated gold nanoparticles on silicon oxide substrates. The particles adhered to the substrate during layer grafting. The film grew selectively on the substrate, without covering the particles. AFM was used to investigate the growth mechanism and the process of embedding the nanoparticles. OTS multilayer films up to 9 layers were grown in a linear, bilayer-by bilayer mode, free of islands and defects. We also report on studies of monolayer and multilayer formation of Methyl-11-dimethylmonochlorosilyl-undecanoate films. Flat multilayers up to 3-layers thick were grown. AFM was used to measure the height of an observable "edge" of the multilayer film and this provides and independent determination of the MOSUD layer height of 1.5 nm: However, the particles detached from the surface when we attempted to grow multilayer. One strategy of linking the particles to form 2D arrays, thermal activation in ambient air, was investigated. The morphological properties of flaked nanoparticles and structures on silicon oxide substrates before and after heating were characterized by using AFM. For widely separated 5 nm gold nanoparticles height decreased over 50% at 600 °C. Further heating to 630 °C caused most particles to completely disappear, with small amount of particle residue left on the surface. Particles positioned near to other particles first formed a neck-like structure at 570 °C and then deformed into one wide particle with tail-shape residue at 650 °C. Clusters of Au nanoparticles rearranged and became one large collide with particles residues left on the surface at 630 °C.

Method of manufacturing a hybrid emitter all back contact solar cell

DOEpatents

Loscutoff, Paul; Rim, Seung

2017-02-07

A method of manufacturing an all back contact solar cell which has a hybrid emitter design. The solar cell has a thin dielectric layer formed on a backside surface of a single crystalline silicon substrate. One emitter of the solar cell is made of doped polycrystalline silicon that is formed on the thin dielectric layer. A second emitter of the solar cell is formed in the single crystalline silicon substrate and is made of doped single crystalline silicon. The method further includes forming contact holes that allow metal contacts to connect to corresponding emitters.

Method of fabricating germanium and gallium arsenide devices

NASA Technical Reports Server (NTRS)

Jhabvala, Murzban (Inventor)

1990-01-01

A method of semiconductor diode fabrication is disclosed which relies on the epitaxial growth of a precisely doped thickness layer of gallium arsenide or germanium on a semi-insulating or intrinsic substrate, respectively, of gallium arsenide or germanium by either molecular beam epitaxy (MBE) or by metal-organic chemical vapor deposition (MOCVD). The method involves: depositing a layer of doped or undoped silicon dioxide on a germanium or gallium arsenide wafer or substrate, selectively removing the silicon dioxide layer to define one or more surface regions for a device to be fabricated thereon, growing a matched epitaxial layer of doped germanium or gallium arsenide of an appropriate thickness using MBE or MOCVD techniques on both the silicon dioxide layer and the defined one or more regions; and etching the silicon dioxide and the epitaxial material on top of the silicon dioxide to leave a matched epitaxial layer of germanium or gallium arsenide on the germanium or gallium arsenide substrate, respectively, and upon which a field effect device can thereafter be formed.

Deep level transient spectroscopic investigation of phosphorus-doped silicon by self-assembled molecular monolayers.

PubMed

Gao, Xuejiao; Guan, Bin; Mesli, Abdelmadjid; Chen, Kaixiang; Dan, Yaping

2018-01-09

It is known that self-assembled molecular monolayer doping technique has the advantages of forming ultra-shallow junctions and introducing minimal defects in semiconductors. In this paper, we report however the formation of carbon-related defects in the molecular monolayer-doped silicon as detected by deep-level transient spectroscopy and low-temperature Hall measurements. The molecular monolayer doping process is performed by modifying silicon substrate with phosphorus-containing molecules and annealing at high temperature. The subsequent rapid thermal annealing drives phosphorus dopants along with carbon contaminants into the silicon substrate, resulting in a dramatic decrease of sheet resistance for the intrinsic silicon substrate. Low-temperature Hall measurements and secondary ion mass spectrometry indicate that phosphorus is the only electrically active dopant after the molecular monolayer doping. However, during this process, at least 20% of the phosphorus dopants are electrically deactivated. The deep-level transient spectroscopy shows that carbon-related defects are responsible for such deactivation.

Substrate and Passivation Techniques for Flexible Amorphous Silicon-Based X-ray Detectors

PubMed Central

Marrs, Michael A.; Raupp, Gregory B.

2016-01-01

Flexible active matrix display technology has been adapted to create new flexible photo-sensing electronic devices, including flexible X-ray detectors. Monolithic integration of amorphous silicon (a-Si) PIN photodiodes on a flexible substrate poses significant challenges associated with the intrinsic film stress of amorphous silicon. This paper examines how altering device structuring and diode passivation layers can greatly improve the electrical performance and the mechanical reliability of the device, thereby eliminating one of the major weaknesses of a-Si PIN diodes in comparison to alternative photodetector technology, such as organic bulk heterojunction photodiodes and amorphous selenium. A dark current of 0.5 pA/mm2 and photodiode quantum efficiency of 74% are possible with a pixelated diode structure with a silicon nitride/SU-8 bilayer passivation structure on a 20 µm-thick polyimide substrate. PMID:27472329

Substrate and Passivation Techniques for Flexible Amorphous Silicon-Based X-ray Detectors.

PubMed

Marrs, Michael A; Raupp, Gregory B

2016-07-26

Flexible active matrix display technology has been adapted to create new flexible photo-sensing electronic devices, including flexible X-ray detectors. Monolithic integration of amorphous silicon (a-Si) PIN photodiodes on a flexible substrate poses significant challenges associated with the intrinsic film stress of amorphous silicon. This paper examines how altering device structuring and diode passivation layers can greatly improve the electrical performance and the mechanical reliability of the device, thereby eliminating one of the major weaknesses of a-Si PIN diodes in comparison to alternative photodetector technology, such as organic bulk heterojunction photodiodes and amorphous selenium. A dark current of 0.5 pA/mm² and photodiode quantum efficiency of 74% are possible with a pixelated diode structure with a silicon nitride/SU-8 bilayer passivation structure on a 20 µm-thick polyimide substrate.

Shear Stress Sensing with Elastic Microfence Structures

NASA Technical Reports Server (NTRS)

Cisotto, Alexxandra; Palmieri, Frank L.; Saini, Aditya; Lin, Yi; Thurman, Christopher S; Kim, Jinwook; Kim, Taeyang; Connell, John W.; Zhu, Yong; Gopalarathnam, Ashok;

Chiral Asymmetric Structures in Aspartic Acid and Valine Crystals Assessed by Atomic Force Microscopy.

PubMed

Teschke, Omar; Soares, David Mendez

2016-03-29

Structures of crystallized deposits formed by the molecular self-assembly of aspartic acid and valine on silicon substrates were imaged by atomic force microscopy. Images of d- and l-aspartic acid crystal surfaces showing extended molecularly flat sheets or regions separated by single molecule thick steps are presented. Distinct orientation surfaces were imaged, which, combined with the single molecule step size, defines the geometry of the crystal. However, single molecule step growth also reveals the crystal chirality, i.e., growth orientations. The imaged ordered lattice of aspartic acid (asp) and valine (val) mostly revealed periodicities corresponding to bulk terminations, but a previously unreported molecular hexagonal lattice configuration was observed for both l-asp and l-val but not for d-asp or d-val. Atomic force microscopy can then be used to identify the different chiral forms of aspartic acid and valine crystals.

Rectangular Relief Diffraction Gratings for Coherent Lidar Beam Deflection

NASA Technical Reports Server (NTRS)

Cole, H. J.; Dixit, S. N.; Shore, B. W.; Chambers, D. M.; Britten, J. A.; Kavaya, M. J.

1999-01-01

LIDAR systems require a light transmitting system for sending a laser light pulse into space and a receiving system for collecting the retro-scattered light, separating it from the outgoing beam and analyzing the received signal for calculating wind velocities. Currently, a shuttle manifested coherent LIDAR experiment called SPARCLE (SPAce Readiness Coherent Lidar Experiment) includes a silicon wedge (or prism) in its design in order to deflect the outgoing beam 30 degrees relative to the incident direction. The intent of this paper is to present two optical design approaches that may enable the replacement of the optical wedge component (in future, larger aperture, post-SPARCLE missions) with a surface relief transmission diffraction grating. Such a grating could be etched into a lightweight, flat, fused quartz substrate. The potential advantages of a diffractive beam deflector include reduced weight, reduced power requirements for the driving scanning motor, reduced optical sensitivity to thermal gradients, and increased dynamic stability.

Topography- and topology-driven spreading of non-Newtonian power-law liquids on a flat and a spherical substrate

NASA Astrophysics Data System (ADS)

Iwamatsu, Masao

2017-10-01

The spreading of a cap-shaped spherical droplet of non-Newtonian power-law liquids on a flat and a spherical rough and textured substrate is theoretically studied in the capillary-controlled spreading regime. A droplet whose scale is much larger than that of the roughness of substrate is considered. The equilibrium contact angle on a rough substrate is modeled by the Wenzel and the Cassie-Baxter model. Only the viscous energy dissipation within the droplet volume is considered, and that within the texture of substrate by imbibition is neglected. Then, the energy balance approach is adopted to derive the evolution equation of the contact angle. When the equilibrium contact angle vanishes, the relaxation of dynamic contact angle θ of a droplet obeys a power-law decay θ ˜t-α except for the Newtonian and the non-Newtonian shear-thinning liquid of the Wenzel model on a spherical substrate. The spreading exponent α of the non-Newtonian shear-thickening liquid of the Wenzel model on a spherical substrate is larger than others. The relaxation of the Newtonian liquid of the Wenzel model on a spherical substrate is even faster showing the exponential relaxation. The relaxation of the non-Newtonian shear-thinning liquid of Wenzel model on a spherical substrate is fastest and finishes within a finite time. Thus, the topography (roughness) and the topology (flat to spherical) of substrate accelerate the spreading of droplet.

Integrated circuit with dissipative layer for photogenerated carriers

DOEpatents

Myers, D.R.

1988-04-20

The sensitivity of an integrated circuit to single-event upsets is decreased by providing a dissipative layer of silicon nitride between a silicon substrate and the active device. Free carriers generated in the substrate are dissipated by the layer before they can build up charge on the active device. 1 fig.

Dewetting of Epitaxial Silver Film on Silicon by Thermal Annealing

NASA Astrophysics Data System (ADS)

Sanders, Charlotte E.; Kellogg, Gary L.; Shih, C.-K.

2013-03-01

It has been shown that noble metals can grow epitaxially on semiconducting and insulating substrates, despite being a non-wetting system: low temperature deposition followed by room temperature annealing leads to atomically flat film morphology. However, the resulting metastable films are vulnerable to dewetting, which has limited their utility for applications under ambient conditions. The physics of this dewetting is of great interest but little explored. We report on an investigation of the dewetting of epitaxial Ag(111) films on Si(111) and (100). Low energy electron microscopy (LEEM) shows intriguing evolution in film morphology and crystallinity, even at temperatures below 100oC. On the basis of these findings, we can begin to draw compelling inferences about film-substrate interaction and the kinetics of dewetting. Financial support is from NSF, DGE-0549417 and DMR-0906025. This work was performed, in part, at the Center for Integrated Nanotechnologies, User Facility operated for the U.S. DOE Office of Science. Sandia National Lab is managed and operated by Sandia Corp., a subsidiary of Lockheed Martin Corp., for the U.S. DOE's National Nuclear Security Administration under DE-AC04-94AL85000.

Crystallization and growth of Ni-Si alloy thin films on inert and on silicon substrates

NASA Astrophysics Data System (ADS)

Grimberg, I.; Weiss, B. Z.

1995-04-01

The crystallization kinetics and thermal stability of NiSi2±0.2 alloy thin films coevaporated on two different substrates were studied. The substrates were: silicon single crystal [Si(100)] and thermally oxidized silicon single crystal. In situ resistance measurements, transmission electron microscopy, x-ray diffraction, Auger electron spectroscopy, and Rutherford backscattering spectroscopy were used. The postdeposition microstructure consisted of a mixture of amorphous and crystalline phases. The amorphous phase, independent of the composition, crystallizes homogeneously to NiSi2 at temperatures lower than 200 °C. The activation energy, determined in the range of 1.4-2.54 eV, depends on the type of the substrate and on the composition of the alloyed films. The activation energy for the alloys deposited on the inert substrate was found to be lower than for the alloys deposited on silicon single crystal. The lowest activation energy was obtained for nonstoichiometric NiSi2.2, the highest for NiSi2—on both substrates. The crystallization mode depends on the structure of the as-deposited films, especially the density of the existing crystalline nuclei. Substantial differences were observed in the thermal stability of the NiSi2 compound on both substrates. With the alloy films deposited on the Si substrate, only the NiSi2 phase was identified after annealing to temperatures up to 800 °C. In the films deposited on the inert substrate, NiSi and NiSi2 phases were identified when the Ni content in the alloy exceeded 33 at. %. The effects of composition and the type of substrate on the crystallization kinetics and thermal stability are discussed.

Screening method for selecting semiconductor substrates having defects below a predetermined level in an oxide layer

DOEpatents

Warren, William L.; Vanheusden, Karel J. R.; Schwank, James R.; Fleetwood, Daniel M.; Shaneyfelt, Marty R.; Winokur, Peter S.; Devine, Roderick A. B.

1998-01-01

A method for screening or qualifying semiconductor substrates for integrated circuit fabrication. The method comprises the steps of annealing at least one semiconductor substrate at a first temperature in a defect-activating ambient (e.g. hydrogen, forming gas, or ammonia) for sufficient time for activating any defects within on oxide layer of the substrate; measuring a defect-revealing electrical characteristic of at least a portion of the oxide layer for determining a quantity of activated defects therein; and selecting substrates for which the quantity of activated defects is below a predetermined level. The defect-revealing electrical characteristic may be a capacitance-versus-voltage (C-V) characteristic or a current-versus-voltage (I-V) characteristic that is dependent on an electrical charge in the oxide layer generated by the activated defects. Embodiments of the present invention may be applied for screening any type of semiconductor substrate or wafer having an oxide layer formed thereon or therein. This includes silicon-on-insulator substrates formed by a separation by the implantation of oxygen (SIMOX) process or the bond and etch back silicon-on-insulator (BESOI) process, as well as silicon substrates having a thermal oxide layer or a deposited oxide layer.

Ultra-low roughness magneto-rheological finishing for EUV mask substrates

NASA Astrophysics Data System (ADS)

Dumas, Paul; Jenkins, Richard; McFee, Chuck; Kadaksham, Arun J.; Balachandran, Dave K.; Teki, Ranganath

2013-09-01

EUV mask substrates, made of titania-doped fused silica, ideally require sub-Angstrom surface roughness, sub-30 nm flatness, and no bumps/pits larger than 1 nm in height/depth. To achieve the above specifications, substrates must undergo iterative global and local polishing processes. Magnetorheological finishing (MRF) is a local polishing technique which can accurately and deterministically correct substrate figure, but typically results in a higher surface roughness than the current requirements for EUV substrates. We describe a new super-fine MRF® polishing fluid whichis able to meet both flatness and roughness specifications for EUV mask blanks. This eases the burden on the subsequent global polishing process by decreasing the polishing time, and hence the defectivity and extent of figure distortion.

The Growth of Expitaxial GaAs and GaAlAs on Silicon Substrates by OMVPE

DTIC Science & Technology

1988-08-01

structures have been grown on semi-insulating gallium arsenide substrates, and on high-resistivity silicon substrates using a two stage growth technique...fully in Quarter 9. 2. MATERIALS GROWTH 2.1 DOPING OF GALLIUM ARSENIDE FOR FETs As reported in quarter 7, doping levels for GaAs/SI 4ere found to be a...FET structures on both GaAs and Si substrates. A number of FET layers have been grown to the GAT4 specification on semi-insulating gallium arsenide

Analysis of high-speed growth of silicon sheet in inclined-meniscus configuration

NASA Technical Reports Server (NTRS)

Thomas, P. D.; Brown, R. A.

1985-01-01

The study of high speed growth of silicon sheet in inclined-meniscus configurations is discussed. It was concluded that the maximum growth rates in vertical and inclined growth are set by thermal-capillary limits. Also, the melt/crystal interface was determined to be flat. And, vertical growth is qualitatively modelled by one dimensional heat transfer.

Wetting of silicone oil onto a cell-seeded substrate

NASA Astrophysics Data System (ADS)

Lu, Yongjie; Chan, Yau Kei; Chao, Youchuang; Shum, Ho Cheung

2017-11-01

Wetting behavior of solid substrates in three-phase systems containing two immiscible liquids are widely studied. There exist many three-phase systems in biological environments, such as droplet-based microfluidics or tamponade of silicone oil for eye surgery. However, few studies focus on wetting behavior of biological surfaces with cells. Here we investigate wetting of silicone oil onto cell-seeded PMMA sheet immersed in water. Using a simple parallel-plate cell, we show the effect of cell density, viscosity of silicone oil, morphology of silicone oil drops and interfacial tension on the wetting phenomenon. The dynamics of wetting is also observed by squeezing silicone oil drop using two parallel plates. Experimental results are explained based on disjoining pressure which is dependent on the interaction of biological surfaces and liquid used. These findings are useful for explaining emulsification of silicone oil in ophthalmological applications.

Critical technology limits to silicon material and sheet production

NASA Technical Reports Server (NTRS)

Leipold, M. H.

1982-01-01

Earlier studies have indicated that expenditures related to the preparation of high-purity silicon and its conversion to silicon sheet represent from 40 to 52 percent of the cost of the entire panel. The present investigation is concerned with the elements which were selected for study in connection with the Flat-Plate Solar Array (FSA) Project. The first of two technologies which are being developed within the FSA Project involves the conversion of metallurgical-grade silicon through a silane purification process to silicon particles. The second is concerned with the conversion of trichlorosilane to dichlorosilane, and the subsequent production of silicon using modified rod reactors of the Siemens type. With respect to silicon sheet preparation, efforts have been focused both on the preparation of ingots, followed by wafering, and the direct crystallization of molten silicon into a ribbon or film.

Method for high-precision multi-layered thin film deposition for deep and extreme ultraviolet mirrors

DOEpatents

Ruffner, Judith Alison

1999-01-01

A method for coating (flat or non-flat) optical substrates with high-reflectivity multi-layer coatings for use at Deep Ultra-Violet ("DUV") and Extreme Ultra-Violet ("EUV") wavelengths. The method results in a product with minimum feature sizes of less than 0.10-.mu.m for the shortest wavelength (13.4-nm). The present invention employs a computer-based modeling and deposition method to enable lateral and vertical thickness control by scanning the position of the substrate with respect to the sputter target during deposition. The thickness profile of the sputter targets is modeled before deposition and then an appropriate scanning algorithm is implemented to produce any desired, radially-symmetric thickness profile. The present invention offers the ability to predict and achieve a wide range of thickness profiles on flat or figured substrates, i.e., account for 1/R.sup.2 factor in a model, and the ability to predict and accommodate changes in deposition rate as a result of plasma geometry, i.e., over figured substrates.

A continuous silicon-coating facility

NASA Technical Reports Server (NTRS)

Butter, C.; Heaps, J. D.

1979-01-01

Automatic continuous silicon-coating facility is used to process 100 by 10 cm graphite-coated ceramic substrates for silicon solar cells. Process reduces contamination associated with conventional dip-coating processes, improving material service life.

Gray scale x-ray mask

DOEpatents

Morales, Alfredo M [Livermore, CA; Gonzales, Marcela [Seattle, WA

2006-03-07

The present invention describes a method for fabricating an embossing tool or an x-ray mask tool, providing microstructures that smoothly vary in height from point-to-point in etched substrates, i.e., structure which can vary in all three dimensions. The process uses a lithographic technique to transfer an image pattern in the surface of a silicon wafer by exposing and developing the resist and then etching the silicon substrate. Importantly, the photoresist is variably exposed so that when developed some of the resist layer remains. The remaining undeveloped resist acts as an etchant barrier to the reactive plasma used to etch the silicon substrate and therefore provides the ability etch structures of variable depths.

Broadly tunable terahertz difference-frequency generation in quantum cascade lasers on silicon

NASA Astrophysics Data System (ADS)

Jung, Seungyong; Kim, Jae Hyun; Jiang, Yifan; Vijayraghavan, Karun; Belkin, Mikhail A.

2018-01-01

We report broadly tunable terahertz (THz) sources based on intracavity Cherenkov difference-frequency generation in quantum cascade lasers transfer-printed on high-resistivity silicon substrates. Spectral tuning from 1.3 to 4.3 THz was obtained from a 2-mm long laser chip using a modified Littrow external cavity setup. The THz power output and the midinfrared-to-THz conversion efficiency of the devices transferred on silicon are dramatically enhanced, compared with the devices on a native semi-insulating InP substrate. Enhancement is particularly significant at higher THz frequencies, where the tail of the Reststrahlen band results in a strong absorption of THz light in the InP substrate.

Designed porosity materials in nuclear reactor components

DOEpatents

Yacout, A. M.; Pellin, Michael J.; Stan, Marius

2016-09-06

A nuclear fuel pellet with a porous substrate, such as a carbon or tungsten aerogel, on which at least one layer of a fuel containing material is deposited via atomic layer deposition, and wherein the layer deposition is controlled to prevent agglomeration of defects. Further, a method of fabricating a nuclear fuel pellet, wherein the method features the steps of selecting a porous substrate, depositing at least one layer of a fuel containing material, and terminating the deposition when the desired porosity is achieved. Also provided is a nuclear reactor fuel cladding made of a porous substrate, such as silicon carbide aerogel or silicon carbide cloth, upon which layers of silicon carbide are deposited.

Monolithically interconnected silicon-film™ module technology

NASA Astrophysics Data System (ADS)

DelleDonne, E. J.; Ford, D. H.; Hall, R. B.; Ingram, A. E.; Rand, J. A.; Barnett, A. M.

1999-03-01

AstroPower is developing an advanced thin-silicon-based, photovoltaic module product. A low-cost monolithic interconnected device is being integrated into a module that combines the design and process features of advanced light trapped, thin-silicon solar cells. This advanced product incorporates a low-cost substrate, a nominally 50-μm thick grown silicon layer with minority carrier diffusion lengths exceeding the active layer thickness, light trapping due to back-surface reflection, and back-surface passivation. The thin silicon layer enables high solar cell performance and can lead to a module conversion efficiency as high as 19%. These performance design features, combined with low-cost manufacturing using relatively low-cost capital equipment, continuous processing and a low-cost substrate, will lead to high-performance, low-cost photovoltaic panels.

Evanescent Microwave Probes on High-Resistivity Silicon and its Application in Characterization of Semiconductors

NASA Technical Reports Server (NTRS)

Tabib-Azar, M.; Akinwande, D.; Ponchak, George E.; LeClair, S. R.

1999-01-01

In this article we report the design, fabrication, and characterization of very high quality factor 10 GHz microstrip resonators on high-resistivity (high-rho) silicon substrates. Our experiments show that an external quality factor of over 13 000 can be achieved on microstripline resonators on high-rho silicon substrates. Such a high Q factor enables integration of arrays of previously reported evanescent microwave probe (EMP) on silicon cantilever beams. We also demonstrate that electron-hole pair recombination and generation lifetimes of silicon can be conveniently measured by illuminating the resonator using a pulsed light. Alternatively, the EMP was also used to nondestructively monitor excess carrier generation and recombination process in a semiconductor placed near the two-dimensional resonator.

Evaluation of the Effect of Silicone Contamination on Various Bond Systems and the Feasibility of Removing the Contamination

NASA Technical Reports Server (NTRS)

Stanley, Stephanie D.

2008-01-01

Silicone is a contaminant that can cause catastrophic failure of a bond system depending on the materials and processes used to fabricate the bond system. Unfortunately, more and more materials are fabricated using silicone. The purpose of this testing was to evaluate which bond systems are sensitive to silicone contamination and whether or not a cleaning process could be utilized to remove the silicone to bring the bond system performance back to baseline. Due to the extensive nature of the testing, attempts will be made to generalize the understanding within classes of substrates, bond systems, and surface preparation and cleaning methods. This study was done by contaminating various metal (steel, Inconel, and aluminum), phenolic (carbon-cloth phenolic [CCP] and glass-cloth phenolic [GCP]), and rubber (natural rubber, asbestos-silicone dioxide filled natural butyldiene rubber [ASNBR]; silica-filled ethylene propylenediene monomer [SFEPDM], and carbon-filled ethylene propylenediene monomer [CFEPDM]) substrates which were then bonded using various adhesives and coatings (epoxy-based adhesives, paints, ablative compounds, and Chemlok adhesives) to determine the effect silicone contamination has on a given bond system's performance. The test configurations depended on the bond system being evaluated. The study also evaluated the feasibility of removing the silicone contamination by cleaning the contaminated substrate prior to bonding. The cleaning processes also varied depending on bond system.

Silicon on ceramic process. Silicon sheet growth development for the large-area silicon sheet task of the low-cost silicon solar array project

NASA Technical Reports Server (NTRS)

Zook, J. D.; Heaps, J. D.; Maciolek, R. B.; Koepke, B. G.; Butter, C. D.; Schuldt, S. B.

1977-01-01

The technical and economic feasibility of producing solar-cell-quality sheet silicon was investigated. The sheets were made by coating one surface of carbonized ceramic substrates with a thin layer of large-grain polycrystalline silicon from the melt. Significant progress was made in all areas of the program.

Effects of varying oxygen partial pressure on molten silicon-ceramic substrate interactions

NASA Technical Reports Server (NTRS)

Ownby, D. P.; Barsoum, M. W.

1980-01-01

The silicon sessile drop contact angle was measured on hot pressed silicon nitride, silicon nitride coated on hot pressed silicon nitride, silicon carbon coated on graphite, and on Sialon to determine the degree to which silicon wets these substances. The post-sessile drop experiment samples were sectioned and photomicrographs were taken of the silicon-substrate interface to observe the degree of surface dissolution and degradation. Of these materials, silicon did not form a true sessile drop on the SiC on graphite due to infiltration of the silicon through the SiC coating, nor on the Sialon due to the formation of a more-or-less rigid coating on the liquid silicon. The most wetting was obtained on the coated Si3N4 with a value of 42 deg. The oxygen concentrations in a silicon ribbon furnace and in a sessile drop furnace were measured using the protable thoria-yttria solid solution electrolyte oxygen sensor. Oxygen partial pressures of 10 to the minus 7 power atm and 10 to the minus 8 power atm were obtained at the two facilities. These measurements are believed to represent nonequilibrium conditions.

Patterned microstructures formed with MeV Au implantation in Si(1 0 0)

NASA Astrophysics Data System (ADS)

Rout, Bibhudutta; Greco, Richard R.; Zachry, Daniel P.; Dymnikov, Alexander D.; Glass, Gary A.

2006-09-01

Energetic (MeV) Au implantation in Si(1 0 0) (n-type) through masked micropatterns has been used to create layers resistant to KOH wet etching. Microscale patterns were produced in PMMA and SU(8) resist coatings on the silicon substrates using P-beam writing and developed. The silicon substrates were subsequently exposed using 1.5 MeV Au 3+ ions with fluences as high as 1 × 10 16 ions/cm 2 and additional patterns were exposed using copper scanning electron microscope calibration grids as masks on the silicon substrates. When wet etched with KOH microstructures were created in the silicon due to the resistance to KOH etching cause by the Au implantation. The process of combining the fabrication of masked patterns with P-beam writing with broad beam Au implantation through the masks can be a promising, cost-effective process for nanostructure engineering with Si.

AES study on the chemical composition of ferroelectric BaTiO3 thin films RF sputter-deposited on silicon

NASA Technical Reports Server (NTRS)

Dharmadhikari, V. S.; Grannemann, W. W.

1983-01-01

AES depth profiling data are presented for thin films of BaTiO3 deposited on silicon by RF sputtering. By profiling the sputtered BaTiO3/silicon structures, it was possible to study the chemical composition and the interface characteristics of thin films deposited on silicon at different substrate temperatures. All the films showed that external surface layers were present, up to a few tens of angstroms thick, the chemical composition of which differed from that of the main layer. The main layer had stable composition, whereas the intermediate film-substrate interface consisted of reduced TiO(2-x) oxides. The thickness of this intermediate layer was a function of substrate temperature. All the films showed an excess of barium at the interface. These results are important in the context of ferroelectric phenomena observed in BaTiO3 thin films.

Optical substrate materials for synchrotron radiation beamlines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Howells, M.R.; Paquin, R.A.

1997-06-01

The authors consider the materials choices available for making optical substrates for synchrotron radiation beam lines. They find that currently the optical surfaces can only be polished to the required finish in fused silica and other glasses, silicon, CVD silicon carbide, electroless nickel and 17-4 PH stainless steel. Substrates must therefore be made of one of these materials or of a metal that can be coated with electroless nickel. In the context of material choices for mirrors they explore the issues of dimensional stability, polishing, bending, cooling, and manufacturing strategy. They conclude that metals are best from an engineering andmore » cost standpoint while the ceramics are best from a polishing standpoint. They then give discussions of specific materials as follows: silicon carbide, silicon, electroless nickel, Glidcop{trademark}, aluminum, precipitation-hardening stainless steel, mild steel, invar and superinvar. Finally they summarize conclusions and propose ideas for further research.« less

Stoichiometry of Silicon Dioxide Films Obtained by Ion-Beam Sputtering

NASA Astrophysics Data System (ADS)

Telesh, E. V.; Dostanko, A. P.; Gurevich, O. V.

2018-03-01

The composition of SiOx films produced by ion-beam sputtering (IBS) of silicon and quartz targets were studied by infrared spectrometry. Films with thicknesses of 150-390 nm were formed on silicon substrates. It was found that increase in the partial pressure of oxygen in the working gas, increase in the temperature of the substrate, and the presence of a positive potential on the target during reactive IBS of silicon shifted the main absorption band νas into the high-frequency region and increased the composition index from 1.41 to 1.85. During IBS of a quartz target the stoichiometry of the films deteriorates with increase of the energy of the sputtering argon ions. This may be due to increase of the deposition rate. Increase in the current of the thermionic compensator, increase of the substrate temperature, and addition of oxygen led to the formation of SiOx films with improved stoichiometry.

Method to fabricate silicon chromatographic column comprising fluid ports

DOEpatents

Manginell, Ronald P.; Frye-Mason, Gregory C.; Heller, Edwin J.; Adkins, Douglas R.

2004-03-02

A new method for fabricating a silicon chromatographic column comprising through-substrate fluid ports has been developed. This new method enables the fabrication of multi-layer interconnected stacks of silicon chromatographic columns.

Curvature Control of Silicon Microlens for THz Dielectric Antenna

NASA Technical Reports Server (NTRS)

Lee, Choonsup; Chattopadhyay, Goutam; Cooper, Ken; Mehdi, Imran

2012-01-01

We have controlled the curvature of silicon microlens by changing the amount of photoresist in order to microfabricate hemispherical silicon microlens which can improve the directivity and reduce substrate mode losses.

Micromachined cutting blade formed from {211}-oriented silicon

DOEpatents

Fleming, James G.; Sniegowski, Jeffry J.; Montague, Stephen

2003-09-09

A cutting blade is disclosed fabricated of micromachined silicon. The cutting blade utilizes a monocrystalline silicon substrate having a {211} crystalline orientation to form one or more cutting edges that are defined by the intersection of {211} crystalline planes of silicon with {111} crystalline planes of silicon. This results in a cutting blade which has a shallow cutting-edge angle .theta. of 19.5.degree.. The micromachined cutting blade can be formed using an anisotropic wet etching process which substantially terminates etching upon reaching the {111} crystalline planes of silicon. This allows multiple blades to be batch fabricated on a common substrate and separated for packaging and use. The micromachined cutting blade, which can be mounted to a handle in tension and optionally coated for increased wear resistance and biocompatibility, has multiple applications including eye surgery (LASIK procedure).

Micromachined cutting blade formed from {211}-oriented silicon

DOEpatents

Fleming, James G [Albuquerque, NM; Fleming, legal representative, Carol; Sniegowski, Jeffry J [Tijeras, NM; Montague, Stephen [Albuquerque, NM

2011-08-09

A cutting blade is disclosed fabricated of micromachined silicon. The cutting blade utilizes a monocrystalline silicon substrate having a {211} crystalline orientation to form one or more cutting edges that are defined by the intersection of {211} crystalline planes of silicon with {111} crystalline planes of silicon. This results in a cutting blade which has a shallow cutting-edge angle .theta. of 19.5.degree.. The micromachined cutting blade can be formed using an anisotropic wet etching process which substantially terminates etching upon reaching the {111} crystalline planes of silicon. This allows multiple blades to be batch fabricated on a common substrate and separated for packaging and use. The micromachined cutting blade, which can be mounted to a handle in tension and optionally coated for increased wear resistance and biocompatibility, has multiple applications including eye surgery (LASIK procedure).

MBE growth and optical properties of GaN layers on SiC/Si(111) hybrid substrate

NASA Astrophysics Data System (ADS)

Reznik, R. R.; Kotlyar, K. P.; Soshnikov, I. P.; Kukushkin, S. A.; Osipov, A. V.; Nikitina, E. V.; Cirlin, G. E.

2017-11-01

The fundamental possibility of the growth of GaN layers by molecular-beam epitaxy on a silicon substrate with nanoscale buffer layer of silicon carbide without any AlN layers has been demonstrated for the first time. Morphological properties of the resulting system have been studied.

Influence of calcium and silicon supplementation into Pleurotus ostreatus substrates on quality of fresh and canned mushrooms.

PubMed

Thongsook, T; Kongbangkerd, T

2011-08-01

Supplements of gypsum (calcium source), pumice (silicon source) and pumice sulfate (silicon and calcium source) into substrates for oyster mushrooms (Pleurotus ostreatus) were searched for their effects on production as well as qualities of fresh and canned mushrooms. The addition of pumice up to 30% had no effect on total yield, size distribution and cap diameters. The supplementation of gypsum at 10% decreased the total yield; and although gypsum at 5% did not affect total yield, the treatment increased the proportion of large-sized caps. High content (>10%) of pumice sulfate resulted in the lower yield. Calcium and silicon contents in the fruit bodies were not influenced by supplementations. The centrifugal drip loss values and solid content of fresh mushrooms, and the percentage of weight gained and firmness of canned mushrooms, cultivated in substrates supplemented with gypsum, pumice and pumice sulfate were significantly (p≤0.05) higher than those of the control. Scanning electron micrographs revealed the more compacted hyphae of mushroom stalks supplemented with silicon and/or calcium after heat treatment, compared to the control. Supplementation of P. ostreatus substrates with 20% pumice was the most practical treatment because it showed no effect on yield and the most cost-effective.

Porous silicon-copper phthalocyanine heterostructure based photoelectrochemical cell

NASA Astrophysics Data System (ADS)

A. Betty, C.; N, Padma; Arora, Shalav; Survaiya, Parth; Bhattacharya, Debarati; Choudhury, Sipra; Roy, Mainak

2018-01-01

A hybrid solar cell consisting of nanostructured p-type porous silicon (PS) deposited with visible light absorbing dye, Copper Phthalocyanine (CuPc) has been prepared in the photoelectrochemical cell configuration. P-type PS with (100) and (111) orientations which have different porous structures were used for studying the effects of the substrate morphology on the cell efficiency. Heterostructures were prepared by depositing three different thicknesses of CuPc for optimizing the cell efficiency. Structural and surface characterizations were studied using XRD, Raman, SEM and AFM on the PS-CuPc heterostructure. XRD spectrum on both plane silicon and porous silicon indicates the π-π stacking of CuPc with increased disorder for CuPc film on porous silicon. Electrochemical characterizations under sun light type radiation have been carried out to evaluate the photosensitivity of the heterostructure. Between the two different substrates, (100) PS gives better photocurrent, possibly due to the higher surface area and lower series resistance of the structure. Among the (100) PS substrates, (100) PS with 15 nm CuPc film gives Voc more than 1 V resulting in higher efficiency for the cell. The study suggests the scope for optimization of solar cell efficiency using various combinations of the substrate structure and thickness of the sensitizing layer.

Oxygen ion-beam microlithography

DOEpatents

Tsuo, Y.S.

1991-08-20

A method of providing and developing a resist on a substrate for constructing integrated circuit (IC) chips includes the following steps: of depositing a thin film of amorphous silicon or hydrogenated amorphous silicon on the substrate and exposing portions of the amorphous silicon to low-energy oxygen ion beams to oxidize the amorphous silicon at those selected portions. The nonoxidized portions are then removed by etching with RF-excited hydrogen plasma. Components of the IC chip can then be constructed through the removed portions of the resist. The entire process can be performed in an in-line vacuum production system having several vacuum chambers. Nitrogen or carbon ion beams can also be used. 5 figures.

Oxygen ion-beam microlithography

DOEpatents

Tsuo, Y. Simon

1991-01-01

A method of providing and developing a resist on a substrate for constructing integrated circuit (IC) chips includes the following steps: of depositing a thin film of amorphous silicon or hydrogenated amorphous silicon on the substrate and exposing portions of the amorphous silicon to low-energy oxygen ion beams to oxidize the amorphous silicon at those selected portions. The nonoxidized portions are then removed by etching with RF-excited hydrogen plasma. Components of the IC chip can then be constructed through the removed portions of the resist. The entire process can be performed in an in-line vacuum production system having several vacuum chambers. Nitrogen or carbon ion beams can also be used.

Silicon nitride protective coatings for silvered glass mirrors

DOEpatents

Tracy, C. Edwin; Benson, David K.

1988-01-01

A protective diffusion barrier for metalized mirror structures is provided by a layer or coating of silicon nitride which is a very dense, transparent, dielectric material that is impervious to water, alkali, and other impurities and corrosive substances that typically attack the metal layers of mirrors and cause degradation of the mirrors' reflectivity. The silicon nitride layer can be deposited on the substrate before metal deposition to stabilize the metal/substrate interface, and it can be deposited over the metal to encapsulate it and protect the metal from corrosion or other degradation. Mirrors coated with silicon nitride according to this invention can also be used as front surface mirrors.

Silicon nitride protective coatings for silvered glass mirrors

DOEpatents

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

1984-07-20

A protective diffusion barrier for metalized mirror structures is provided by a layer or coating of silicon nitride which is a very dense, transparent, dielectric material that is impervious to water, alkali, and other impurities and corrosive substances that typically attack the metal layers of mirrors and cause degradation of the mirrors' reflectivity. The silicon nitride layer can be deposited on the substrate prior to metal deposition thereon to stabilize the metal/substrate interface, and it can be deposited over the metal to encapsulate it and protect the metal from corrosion or other degradation. Mirrors coated with silicon nitride according to this invention can also be used as front surface mirrors.

Study of thickness and uniformity of oxide passivation with DI-O3 on silicon substrate for electronic and photonic applications

NASA Astrophysics Data System (ADS)

Sharma, Mamta; Hazra, Purnima; Singh, Satyendra Kumar

2018-05-01

Since the beginning of semiconductor fabrication technology evolution, clean and passivated substrate surface is one of the prime requirements for fabrication of Electronic and optoelectronic device fabrication. However, as the scale of silicon circuits and device architectures are continuously decreased from micrometer to nanometer (from VLSI to ULSI technology), the cleaning methods to achieve better wafer surface qualities has raised research interests. The development of controlled and uniform silicon dioxide is the most effective and reliable way to achieve better wafer surface quality for fabrication of electronic devices. On the other hand, in order to meet the requirement of high environment safety/regulatory standards, the innovation of cleaning technology is also in demand. The controlled silicon dioxide layer formed by oxidant de-ionized ozonated water has better uniformity. As the uniformity of the controlled silicon dioxide layer is improved on the substrate, it enhances the performance of the devices. We can increase the thickness of oxide layer, by increasing the ozone time treatment. We reported first time to measurement of thickness of controlled silicon dioxide layer and obtained the uniform layer for same ozone time.

Laser generation in microdisc resonators with InAs/GaAs quantum dots transferred on a silicon substrate

NASA Astrophysics Data System (ADS)

Nadtochiy, A. M.; Kryzhanovskaya, N. V.; Maximov, M. V.; Zhukov, A. E.; Moiseev, E. I.; Kulagina, M. M.; Vashanova, K. A.; Zadiranov, Yu. M.; Mukhin, I. S.; Arakcheeva, E. M.; Livshits, D.; Lipovskii, A. A.

2013-09-01

Microdisc resonators based on InAs/GaAs quantum dots separated from a GaAs substrate by selective etching and fixed to a silicon substrate by epoxy glue are studied using luminescence spectroscopy. A disc resonator 6 μm in diameter exhibits quasi-single-mode laser generation at a temperature of 78 K with a threshold power of 320 μW and λ/Δλ ˜ 27000.

Buried MoO x/Ag Electrode Enables High-Efficiency Organic/Silicon Heterojunction Solar Cells with a High Fill Factor.

PubMed

Xia, Zhouhui; Gao, Peng; Sun, Teng; Wu, Haihua; Tan, Yeshu; Song, Tao; Lee, Shuit-Tong; Sun, Baoquan

2018-04-25

Silicon (Si)/organic heterojunction solar cells based on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and n-type Si have attracted wide interests because they promise cost-effectiveness and high-efficiency. However, the limited conductivity of PEDOT:PSS leads to an inefficient hole transport efficiency for the heterojunction device. Therefore, a high dense top-contact metal grid electrode is required to assure the efficient charge collection efficiency. Unfortunately, the large metal grid coverage ratio electrode would lead to undesirable optical loss. Here, we develop a strategy to balance PEDOT:PSS conductivity and grid optical transmittance via a buried molybdenum oxide/silver grid electrode. In addition, the grid electrode coverage ratio is optimized to reduce its light shading effect. The buried electrode dramatically reduces the device series resistance, which leads to a higher fill factor (FF). With the optimized buried electrode, a record FF of 80% is achieved for flat Si/PEDOT:PSS heterojunction devices. With further enhancement adhesion between the PEDOT:PSS film and Si substrate by a chemical cross-linkable silance, a power conversion efficiency of 16.3% for organic/textured Si heterojunction devices is achieved. Our results provide a path to overcome the inferior organic semiconductor property to enhance the organic/Si heterojunction solar cell.

Silicon-on-ceramic process: Silicon sheet growth and device development for the large-area silicon sheet task of the low-cost solar array project

NASA Technical Reports Server (NTRS)

Whitehead, A. B.; Zook, J. D.; Grung, B. L.; Heaps, J. D.; Schmit, F.; Schuldt, S. B.; Chapman, P. W.

1981-01-01

The technical feasibility of producing solar cell quality sheet silicon to meet the DOE 1986 cost goal of 70 cents/watt was investigated. The silicon on ceramic approach is to coat a low cost ceramic substrate with large grain polycrystalline silicon by unidirectional solidification of molten silicon. Results and accomplishments are summarized.

Fabrication of terahertz metamaterials using electrohydrodynamic jet printing for sensitive detection of yeast

NASA Astrophysics Data System (ADS)

Pradhipta Tenggara, Ayodya; Park, S. J.; Teguh Yudistira, Hadi; Ahn, Y. H.; Byun, Doyoung

2017-03-01

We demonstrated the fabrication of terahertz metamaterial sensor for the accurate and on-site detection of yeast using electrohydrodynamic jet printing, which is inexpensive, simple, and environmentally friendly. The very small sized pattern up to 5 µm-width of electrical split ring resonator unit structures could be printed on a large area on both a rigid substrate and flexible substrate, i.e. silicon wafer and polyimide film using the drop on demand technique to eject liquid ink containing silver nanoparticles. Experimental characterization and simulation were performed to study their performances in detecting yeast of different weights. It was shown that the metamaterial sensor fabricated on a flexible polyimide film had higher sensitivity by more than six times than the metamaterial sensor fabricated on a silicon wafer, due to the low refractive index of the PI substrate and due to the extremely thin substrate thickness which lowers the effective index further. The resonance frequency shift saturated when the yeast weights were 145 µg and 215 µg for metamaterial structures with gap size 6.5 µm fabricated on the silicon substrate and on the polyimide substrate, respectively.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Yu; School of Mechanical and Electrical Engineering, Wuhan Institute of Technology, Wuhan 430073; Guo, Zhiguang, E-mail: zguo@licp.cas.cn

Graphical abstract: A double-metal-assisted chemical etching method is employed to fabricate superhydrophobic surfaces, showing a good superhydrophobicity with the contact angle of about 170°, and the sliding angle of about 0°. Meanwhile, the potential formation mechanism about it is also presented. Highlights: ► A double-metal-assisted chemical etching method is employed to fabricate superhydrophobic surfaces. ► The obtained surfaces show good superhydrophobicity with a high contact angle and low sliding angle. ► The color of the etched substrate dark brown or black and it is so-called black silicon. -- Abstract: Silicon substrates treated by metal-assisted chemical etching have been studied formore » many years since they could be employed in a variety of electronic and optical devices such as integrated circuits, photovoltaics, sensors and detectors. However, to the best of our knowledge, the chemical etching treatment on the same silicon substrate with the assistance of two or more kinds of metals has not been reported. In this paper, we mainly focus on the etching time and finally obtain a series of superhydrophobic silicon surfaces with novel etching structures through two successive etching processes of Cu-assisted and Ag-assisted chemical etching. It is shown that large-scale homogeneous but locally irregular wire-like structures are obtained, and the superhydrophobic surfaces with low hysteresis are prepared after the modifications with low surface energy materials. It is worth noting that the final silicon substrates not only possess high static contact angle and low hysteresis angle, but also show a black color, indicating that the superhydrophobic silicon substrate has an extremely low reflectance in a certain range of wavelengths. In our future work, we will go a step further to discuss the effect of temperature, the size of Cu nanoparticles and solution concentration on the final topography and superhydrophobicity.« less

The 19th Project Integration Meeting

NASA Technical Reports Server (NTRS)

Mcdonald, R. R.

1981-01-01

The Flat-Plate Solar Array Project is described. Project analysis and integration is discussed. Technology research in silicon material, large-area silicon sheet and environmental isolation; cell and module formation; engineering sciences, and module performance and failure analysis. It includes a report on, and copies of visual presentations made at, the 19th Project Integration Meeting held at Pasadena, California, on November 11, 1981.

Conducting LaAlO3/SrTiO3 heterointerfaces on atomically-flat substrates prepared by deionized-water

PubMed Central

Connell, J. G.; Nichols, J.; Gruenewald, J. H.; Kim, D.-W.; Seo, S. S. A.

2016-01-01

We have investigated how the recently-developed water-leaching method for atomically-flat SrTiO3 (STO) substrates affects the transport properties of LaAlO3 (LAO) and STO heterointerfaces. Using pulsed laser deposition at identical growth conditions, we have synthesized epitaxial LAO thin-films on two different STO substrates, which are prepared by water-leaching and buffered hydrofluoric acid (BHF) etching methods. The structural, transport, and optical properties of LAO/STO heterostructures grown on water-leached substrates show the same high-quality as the samples grown on BHF-etched substrates. These results indicate that the water-leaching method can be used to grow complex oxide heterostructures with atomically well-defined heterointerfaces without safety concerns. PMID:27033248

High performance and reusable SERS substrates using Ag/ZnO heterostructure on periodic silicon nanotube substrate

NASA Astrophysics Data System (ADS)

Lai, Yi-Chen; Ho, Hsin-Chia; Shih, Bo-Wei; Tsai, Feng-Yu; Hsueh, Chun-Hway

2018-05-01

Surface-enhanced Raman scattering (SERS) substrate with a higher surface area, enhanced light harvesting, multiple hot spots and strong electromagnetic field enhancements would exhibit enhanced Raman signals. Herein, the Ag nanoparticle/ZnO nanowire heterostructure decorated periodic silicon nanotube (Ag@ZnO@SiNT) substrate was proposed and fabricated. The proposed structure employed as SERS-active substrate was examined, and the results showed both the high performance in terms of high sensitivity and good reproducibility. Furthermore, the Ag@ZnO@SiNT substrate demonstrated the self-cleaning performance through the photocatalytic degradation of probed molecules upon UV-irradiation. The results showed that the proposed nanostructure had high performance, good reproducibility and reusability, and it is a promising SERS-active substrate for molecular sensing and cleaning.

Physical and biological evaluations of sintered hydroxyapatite/silicone composite with covalent bonding for a percutaneous implant material.

PubMed

Furuzono, Tsutomu; Wang, Pao-Li; Korematsu, Arata; Miyazaki, Kozo; Oido-Mori, Mari; Kowashi, Yusuke; Ohura, Kiyoshi; Tanaka, Junzo; Kishida, Akio

2003-05-15

A composite (HA/silicone) of hydroxyapatite (HA) microparticles with an average diameter of 2.0 micro m covalently linked to a silicone substrate has been developed, and its physical and biological properties as a percutaneous soft-tissue-compatible material have been evaluated. In tensile property measurement, samples of HA/silicone and the original silicone were similar in tensile strength, ca. 7.8 MPa, and elongation at break, ca. 570%. It was found that chemical surface modification with HA particles presented no mechanical disadvantage. In an adhesive-tape peeling test, scanning electron microscopic (SEM) observation showed that HA particles coupled directly to the substrate were not removed. HA particles may bond strongly with the substrate. In human periodontal ligament fibroblast attachment and proliferation experiments, the number of cells attached to HA/silicone was 14 times greater than that attached to the original silicone after 24 h of incubation. The value on HA/silicone was ca. 80% versus that on a tissue-culture plastic used as a positive control. After 72 h of incubation, the number of cells grown on HA/silicone increased to the level of the positive control. In observation of fluorescence microscopy stained by Hoechst 33342, cells appeared to tightly adhere to HA particles coupled to the silicone sheet due to intact nuclear morphology. Observation of cells by fluorescence dye with rhodamin phalloidin showed an extensive F-actin cytoskeleton on HA/silicone. In a 4-week animal implant test, force required to pull out the HA/silicone sheet was 15 times that of the original silicone. HA-particle coating on silicone with covalent linkage gave the inert surface bioactivity. The HA composite thus effectively prevents germ infection percutaneously. Copyright 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 65B: 217-226, 2003

Method of Forming Textured Silicon Substrate by Maskless Cryogenic Etching

NASA Technical Reports Server (NTRS)

Yee, Karl Y. (Inventor); Homyk, Andrew P. (Inventor)

2014-01-01

Disclosed herein is a textured substrate comprising a base comprising silicon, the base having a plurality of needle like structures depending away from the base, wherein at least one of the needle like structures has a depth of greater than or equal to about 50 micrometers determined perpendicular to the base, and wherein at least one of the needle like structures has a width of less than or equal to about 50 micrometers determined parallel to the base. An anode and a lithium ion battery comprising the textured substrate, and a method of producing the textured substrate are also disclosed.

A sub-atmospheric chemical vapor deposition process for deposition of oxide liner in high aspect ratio through silicon vias.

PubMed

Lisker, Marco; Marschmeyer, Steffen; Kaynak, Mehmet; Tekin, Ibrahim

2011-09-01

The formation of a Through Silicon Via (TSV) includes a deep Si trench etching and the formation of an insulating layer along the high-aspect-ratio trench and the filling of a conductive material into the via hole. The isolation of the filling conductor from the silicon substrate becomes more important for higher frequencies due to the high coupling of the signal to the silicon. The importance of the oxide thickness on the via wall isolation can be verified using electromagnetic field simulators. To satisfy the needs on the Silicon dioxide deposition, a sub-atmospheric chemical vapor deposition (SA-CVD) process has been developed to deposit an isolation oxide to the walls of deep silicon trenches. The technique provides excellent step coverage of the 100 microm depth silicon trenches with the high aspect ratio of 20 and more. The developed technique allows covering the deep silicon trenches by oxide and makes the high isolation of TSVs from silicon substrate feasible which is the key factor for the performance of TSVs for mm-wave 3D packaging.

High-quality graphene flakes exfoliated on a flat hydrophobic polymer

NASA Astrophysics Data System (ADS)

Pedrinazzi, Paolo; Caridad, José M.; Mackenzie, David M. A.; Pizzocchero, Filippo; Gammelgaard, Lene; Jessen, Bjarke S.; Sordan, Roman; Booth, Timothy J.; Bøggild, Peter

2018-01-01

We show that graphene supported on a hydrophobic and flat polymer surface results in flakes with extremely low doping and strain as assessed by their Raman spectroscopic characteristics. We exemplify this technique by micromechanical exfoliation of graphene on flat poly(methylmethacrylate) layers and demonstrate Raman peak intensity ratios I(2D)/I(G) approaching 10, similar to pristine freestanding graphene. We verify that these features are not an artifact of optical interference effects occurring at the substrate: they are similarly observed when varying the substrate thickness and are maintained when the environment of the graphene flake is completely changed, by encapsulating preselected flakes between hexagonal boron nitride layers. The exfoliation of clean, pristine graphene layers directly on flat polymer substrates enables high performance, supported, and non-encapsulated graphene devices for flexible and transparent optoelectronic studies. We additionally show that the access to a clean and supported graphene source leads to high-quality van der Waals heterostructures and devices with reproducible carrier mobilities exceeding 50 000 cm2 V-1 s-1 at room temperature.

Light-induced V{sub oc} increase and decrease in high-efficiency amorphous silicon solar cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stuckelberger, M., E-mail: michael.stuckelberger@epfl.ch; Riesen, Y.; Despeisse, M.

High-efficiency amorphous silicon (a-Si:H) solar cells were deposited with different thicknesses of the p-type amorphous silicon carbide layer on substrates of varying roughness. We observed a light-induced open-circuit voltage (V{sub oc}) increase upon light soaking for thin p-layers, but a decrease for thick p-layers. Further, the V{sub oc} increase is enhanced with increasing substrate roughness. After correction of the p-layer thickness for the increased surface area of rough substrates, we can exclude varying the effective p-layer thickness as the cause of the substrate roughness dependence. Instead, we explain the observations by an increase of the dangling-bond density in both themore » p-layer—causing a V{sub oc} increase—and in the intrinsic absorber layer, causing a V{sub oc} decrease. We present a mechanism for the light-induced increase and decrease, justified by the investigation of light-induced changes of the p-layer and supported by Advanced Semiconductor Analysis simulation. We conclude that a shift of the electron quasi-Fermi level towards the conduction band is the reason for the observed V{sub oc} enhancements, and poor amorphous silicon quality on rough substrates enhances this effect.« less

Silicon-slurry/aluminide coating. [protecting gas turbine engine vanes and blades

NASA Technical Reports Server (NTRS)

Deadmore, D. L.; Young, S. G. (Inventor)

1983-01-01

A low cost coating protects metallic base system substrates from high temperatures, high gas velocity ovidation, thermal fatigue and hot corrosion and is particularly useful fo protecting vanes and blades in aircraft and land based gas turbine engines. A lacquer slurry comprising cellulose nitrate containing high purity silicon powder is sprayed onto the superalloy substrates. The silicon layer is then aluminized to complete the coating. The Si-Al coating is less costly to produce than advanced aluminides and protects the substrates from oxidation and thermal fatigue for a much longer period of time than the conventional aluminide coatings. While more expensive Pt-Al coatings and physical vapor deposited MCrAlY coatings may last longer or provide equal protection on certain substrates, the Si-Al coating exceeded the performance of both types of coatings on certain superalloys in high gas velocity oxidation and thermal fatigue and increased the resistance of certain superalloys to hot corrosion.

Experimental study of optical and electrical properties of ZnO nano composites electrodeposited on n-porous silicon substrate for photovoltaic applications

NASA Astrophysics Data System (ADS)

Selmane, Naceur; Cheknane, Ali; Gabouze, Nourddine; Maloufi, Nabila; Aillerie, Michel

2017-11-01

ZnO films deposited on silicon porous substrates (PS) were prepared by electro-deposition anodization on n type (100) silicon wafer. This ZnO/PS structure combines substrates having specific structural and optical properties (IR emission), with nano-composites of ZnO potentially interesting due to their functional properties (UV emission) to be integrated as constitutive elements of devices in various optoelectronic applications mainly in blue light emitters. With this combined structure, the blue shift in the PL peak is possible and easy to obtain (467nm). The vibration modes of PS and ZnO films on PS substrates (ZnO /PS) were investigated by infrared (FTIR) measurements and their behaviors were analyzed and discussed by considering the structural properties characterized by X-ray diffraction (DRX) and scanning electronic microscopy (MEB).

Effects of macro- versus nanoporous silicon substrates on human aortic endothelial cell behavior

PubMed Central

2014-01-01

Human aortic endothelial cells play a key role in the pathogenesis of atherosclerosis, which is a common, progressive, and multifactorial disease that is the clinical endpoint of an inflammatory process and endothelial dysfunction. Study and development of new therapies against cardiovascular disease must be tested in vitro cell models, prior to be evaluated in vivo. To this aim, new cell culture platforms are developed that allow cells to grow and respond to their environment in a realistic manner. In this work, the cell adhesion and morphology of endothelial cells are investigated on functionalized porous silicon substrates with two different pore size configurations: macroporous and nanoporous silicon. Herein, we modified the surfaces of porous silicon substrates by aminopropyl triethoxysilane, and we studied how different pore geometries induced different cellular response in the cell morphology and adhesion. The cell growth over the surface of porous silicon becomes an attractive field, especially for medical applications. Surface properties of the biomaterial are associated with cell adhesion and as well as, with proliferation, migration and differentiation. PMID:25246859

Performance study of double SOI image sensors

NASA Astrophysics Data System (ADS)

Miyoshi, T.; Arai, Y.; Fujita, Y.; Hamasaki, R.; Hara, K.; Ikegami, Y.; Kurachi, I.; Nishimura, R.; Ono, S.; Tauchi, K.; Tsuboyama, T.; Yamada, M.

2018-02-01

Double silicon-on-insulator (DSOI) sensors composed of two thin silicon layers and one thick silicon layer have been developed since 2011. The thick substrate consists of high resistivity silicon with p-n junctions while the thin layers are used as SOI-CMOS circuitry and as shielding to reduce the back-gate effect and crosstalk between the sensor and the circuitry. In 2014, a high-resolution integration-type pixel sensor, INTPIX8, was developed based on the DSOI concept. This device is fabricated using a Czochralski p-type (Cz-p) substrate in contrast to a single SOI (SSOI) device having a single thin silicon layer and a Float Zone p-type (FZ-p) substrate. In the present work, X-ray spectra of both DSOI and SSOI sensors were obtained using an Am-241 radiation source at four gain settings. The gain of the DSOI sensor was found to be approximately three times that of the SSOI device because the coupling capacitance is reduced by the DSOI structure. An X-ray imaging demonstration was also performed and high spatial resolution X-ray images were obtained.

Nanoconfinement platform for nanostructure quantification via grazing-transmission X-ray scattering

DOEpatents

Black, Charles T.; Yager, Kevin G.

2017-01-31

A nano-confinement platform that may allow improved quantification of the structural order of nanometer-scale systems. Sample-holder `chips` are designed for the GTSAXS experimental geometry. The platform involves fabricated nanostructured sample holders on and in one or more corners of a substrate support where the sample material of interest is positioned at the corner of the substrate support. In an embodiment, the substrate material making up the substrate support beneath the sample-holding area is removed. A scattering x-ray sample platform includes a substrate support arranged in a parallelepiped form, having a substantially flat base and a substantially flat top surface, the top surface being substantially parallel with the base, the parallelepiped having a plurality of corners. At least one corner of the substrate support has a sample holding area formed in the top surface of the substrate support and within a predetermined distance from the corner. The sample holding area includes a regular array of nano-wells formed in the top surface of the substrate support.

Light Trapping in Thin Film Silicon Solar Cells on Plastic Substrates

NASA Astrophysics Data System (ADS)

de Jong, M. M.

2013-01-01

In the search for sustainable energy sources, solar energy can fulfil a large part of the growing demand. The biggest threshold for large-scale solar energy harvesting is the solar panel price. For drastic cost reductions, roll-to-roll fabrication of thin film silicon solar cells using plastic substrates can be a solution. In this thesis, we investigate the possibilities of depositing thin film solar cells directly onto cheap plastic substrates. Micro-textured glass and sheets, which have a wide range of applications, such as in green house, lighting etc, are applied in these solar cells for light trapping. Thin silicon films can be produced by decomposing silane gas, using a plasma process. In these types of processes, the temperature of the growing surface has a large influence on the quality of the grown films. Because plastic substrates limit the maximum tolerable substrate temperature, new methods have to be developed to produce device-grade silicon layers. At low temperature, polysilanes can form in the plasma, eventually forming dust particles, which can deteriorate device performance. By studying the spatially resolved optical emission from the plasma between the electrodes, we can identify whether we have a dusty plasma. Furthermore, we found an explanation for the temperature dependence of dust formation; Monitoring the formation of polysilanes as a function of temperature using a mass-spectrometer, we observed that the polymerization rate is indeed influenced by the substrate temperature. For solar cell substrate material, our choice was polycarbonate (PC), because of its low cost, its excellent transparency and its relatively high glass transition temperature of 130-140°C. At 130°C we searched for deposition recipes for device quality silicon, using a very high frequency plasma enhanced chemical deposition process. By diluting the feedstock silane with hydrogen gas, the silicon quality can be improved for amorphous silicon (a-Si), until we reach the nanocrystalline silicon (nc-Si) regime. In the nc-Si regime, the crystalline fraction can be further controlled by changing the power input into the plasma. With these layers, a-Si thin film solar cells were fabricated, on glass and PC substrates. The adverse effect of the low temperature growth on the photoactive material is further mitigated by using thinner silicon layers, which can deliver a good current only with an adequate light trapping technique. We have simulated and experimentally tested three light trapping techniques, using embossed structures in PC substrates and random structures on glass: regular pyramid structures larger than the wavelength of light (micropyramids), regular pyramid structures comparable to the wavelength of light (nanopyramids) and random nano-textures (Asahi U-type). The use of nanostructured polycarbonate substrates results in initial conversion efficiencies of 7.4%, compared to 7.6% for cells deposited under identical conditions on Asahi U-type glass. The potential of manufacturing thin film solar cells at processing temperatures lower than 130oC is further illustrated by obtained results on texture-etched aluminium doped zinc-oxide (ZnO:Al) on glass: we achieved 6.9% for nc-Si cells using a very thin absorber layer of only 750 nm, and by combining a-Si and nc-Si cells in tandem solar cells we reached an initial conversion efficiency of 9.5%.

Screening method for selecting semiconductor substrates having defects below a predetermined level in an oxide layer

DOEpatents

Warren, W.L.; Vanheusden, K.J.R.; Schwank, J.R.; Fleetwood, D.M.; Shaneyfelt, M.R.; Winokur, P.S.; Devine, R.A.B.

1998-07-28

A method is disclosed for screening or qualifying semiconductor substrates for integrated circuit fabrication. The method comprises the steps of annealing at least one semiconductor substrate at a first temperature in a defect-activating ambient (e.g. hydrogen, forming gas, or ammonia) for sufficient time for activating any defects within on oxide layer of the substrate; measuring a defect-revealing electrical characteristic of at least a portion of the oxide layer for determining a quantity of activated defects therein; and selecting substrates for which the quantity of activated defects is below a predetermined level. The defect-revealing electrical characteristic may be a capacitance-versus voltage (C-V) characteristic or a current-versus-voltage (I-V) characteristic that is dependent on an electrical charge in the oxide layer generated by the activated defects. Embodiments of the present invention may be applied for screening any type of semiconductor substrate or wafer having an oxide layer formed thereon or therein. This includes silicon-on-insulator substrates formed by a separation by the implantation of oxygen (SIMOX) process or the bond and etch back silicon-on-insulator (BESOI) process, as well as silicon substrates having a thermal oxide layer or a deposited oxide layer. 5 figs.

EPITAXIAL GROWTH OF SILICON

DTIC Science & Technology

Epitaxial growth of silicon on a silicon substrate by hydrogen reduction of SiCl4 was investigated. The chemical and physical processes involved in...silicon layers were produced at temperatures between 1100 and 1300 C. The effects of the concentration of SiCl4 in H2, the flow rate of the gas, the

Fast assembling microarrays of superparamagnetic Fe3O4@Au nanoparticle clusters as reproducible substrates for surface-enhanced Raman scattering

NASA Astrophysics Data System (ADS)

Ye, Min; Wei, Zewen; Hu, Fei; Wang, Jianxin; Ge, Guanglu; Hu, Zhiyuan; Shao, Mingwang; Lee, Shuit-Tong; Liu, Jian

2015-08-01

It is currently a very active research area to develop new types of substrates which integrate various nanomaterials for surface-enhanced Raman scattering (SERS) techniques. Here we report a unique approach to prepare SERS substrates with reproducible performance. It features silicon mold-assisted magnetic assembling of superparamagnetic Fe3O4@Au nanoparticle clusters (NCs) into arrayed microstructures on a wafer scale. This approach enables the fabrication of both silicon-based and hydrogel-based substrates in a sequential manner. We have demonstrated that strong SERS signals can be harvested from these substrates due to an efficient coupling effect between Fe3O4@Au NCs, with enhancement factors >106. These substrates have been confirmed to provide reproducible SERS signals, with low variations in different locations or batches of samples. We investigate the spatial distributions of electromagnetic field enhancement around Fe3O4@Au NCs assemblies using finite-difference-time-domain (FDTD) simulations. The procedure to prepare the substrates is straightforward and fast. The silicon mold can be easily cleaned out and refilled with Fe3O4@Au NCs assisted by a magnet, therefore being re-useable for many cycles. Our approach has integrated microarray technologies and provided a platform for thousands of independently addressable SERS detection, in order to meet the requirements of a rapid, robust, and high throughput performance.It is currently a very active research area to develop new types of substrates which integrate various nanomaterials for surface-enhanced Raman scattering (SERS) techniques. Here we report a unique approach to prepare SERS substrates with reproducible performance. It features silicon mold-assisted magnetic assembling of superparamagnetic Fe3O4@Au nanoparticle clusters (NCs) into arrayed microstructures on a wafer scale. This approach enables the fabrication of both silicon-based and hydrogel-based substrates in a sequential manner. We have demonstrated that strong SERS signals can be harvested from these substrates due to an efficient coupling effect between Fe3O4@Au NCs, with enhancement factors >106. These substrates have been confirmed to provide reproducible SERS signals, with low variations in different locations or batches of samples. We investigate the spatial distributions of electromagnetic field enhancement around Fe3O4@Au NCs assemblies using finite-difference-time-domain (FDTD) simulations. The procedure to prepare the substrates is straightforward and fast. The silicon mold can be easily cleaned out and refilled with Fe3O4@Au NCs assisted by a magnet, therefore being re-useable for many cycles. Our approach has integrated microarray technologies and provided a platform for thousands of independently addressable SERS detection, in order to meet the requirements of a rapid, robust, and high throughput performance. Electronic supplementary information (ESI) available: XRD, reflection spectra, zeta potential, TEM images, evaluations of reproducibility, EDS, tables of EF and RSD values of different substrates. See DOI: 10.1039/c5nr02491a

Titanium disilicide formation by sputtering of titanium on heated silicon substrate

NASA Astrophysics Data System (ADS)

Tanielian, M.; Blackstone, S.

1984-09-01

We have sputter deposited titanium on bare silicon substrates at elevated temperatures. We find that at a substrate temperature of about 515 °C titanium silicide is formed due to the reaction of the titanium with the Si. The resistivity of the silicide is about 15 μΩ cm and it is not etchable in a selective titanium etch. This process can have applications in low-temperature, metal-oxide-semiconductor self-aligned silicide formation for very large scale integrated

Thin film photovoltaic device with multilayer substrate

DOEpatents

Catalano, Anthony W.; Bhushan, Manjul

1984-01-01

A thin film photovoltaic device which utilizes at least one compound semiconductor layer chosen from Groups IIB and VA of the Periodic Table is formed on a multilayer substrate The substrate includes a lowermost support layer on which all of the other layers of the device are formed. Additionally, an uppermost carbide or silicon layer is adjacent to the semiconductor layer. Below the carbide or silicon layer is a metal layer of high conductivity and expansion coefficient equal to or slightly greater than that of the semiconductor layer.

Imaging antenna array at 119 microns. [for plasma diagnostics

NASA Technical Reports Server (NTRS)

Neikirk, N. P.; Tong, P. P.; Putledge, D. B.; Park, H.; Young, P. E.

1982-01-01

A focal-plane imaging antenna array has been demonstrated at 119 microns. The array is a line of evaporated silver bow-tie antennas with bismuth microbolometer detectors on a silicon substrate. Radiation is coupled into the array by a lens placed on the back of the substrate. The bolometers are thermally isolated from the silicon substrate with a half-micron layer of polyimide. The array performance is demonstrated by coherent imaging of a series of holes at half the diffraction-limited cut-off frequency.

Surface properties of atomically flat poly-crystalline SrTiO3

PubMed Central

Woo, Sungmin; Jeong, Hoidong; Lee, Sang A.; Seo, Hosung; Lacotte, Morgane; David, Adrian; Kim, Hyun You; Prellier, Wilfrid; Kim, Yunseok; Choi, Woo Seok

2015-01-01

Comparison between single- and the poly-crystalline structures provides essential information on the role of long-range translational symmetry and grain boundaries. In particular, by comparing single- and poly-crystalline transition metal oxides (TMOs), one can study intriguing physical phenomena such as electronic and ionic conduction at the grain boundaries, phonon propagation, and various domain properties. In order to make an accurate comparison, however, both single- and poly-crystalline samples should have the same quality, e.g., stoichiometry, crystallinity, thickness, etc. Here, by studying the surface properties of atomically flat poly-crystalline SrTiO3 (STO), we propose an approach to simultaneously fabricate both single- and poly-crystalline epitaxial TMO thin films on STO substrates. In order to grow TMOs epitaxially with atomic precision, an atomically flat, single-terminated surface of the substrate is a prerequisite. We first examined (100), (110), and (111) oriented single-crystalline STO surfaces, which required different annealing conditions to achieve atomically flat surfaces, depending on the surface energy. A poly-crystalline STO surface was then prepared at the optimum condition for which all the domains with different crystallographic orientations could be successfully flattened. Based on our atomically flat poly-crystalline STO substrates, we envision expansion of the studies regarding the TMO domains and grain boundaries. PMID:25744275

Surface Control of Actuated Hybrid Space Mirrors

DTIC Science & Technology

2010-10-01

precision Nanolaminate foil facesheet and Silicon Carbide ( SiC ) substrate embedded with electroactive ceramic actuators. Wavefront sensors are used to...integrate precision Nanolaminate foil facesheet with Silicon Carbide ( SiC ) substrate equipped with embedded electroactive ceramic actuators...IAC-10.C2.5.8 SURFACE CONTROL OF ACTUATED HYBRID SPACE MIRRORS Brij. N. Agrawal Naval Postgraduate School, Monterey, CA, 93943, agrawal

Sputtered silicon nitride coatings for wear protection

NASA Technical Reports Server (NTRS)

Grill, A.; Aron, P. R.

1982-01-01

Silicon nitride films were deposited by RF sputtering on 304 stainless steel substrates in a planar RF sputtering apparatus. The sputtering was performed from a Si3N4 target in a sputtering atmosphere of argon and nitrogen. The rate of deposition, the composition of the coatings, the surface microhardness and the adhesion of the coatings to the substrates were investigated as a function of the process parameters, such as: substrate target distance, fraction nitrogen in the sputtering atmosphere and sputtering pressure. Silicon rich coating was obtained for fraction nitrogen below 0.2. The rate of deposition decreases continuously with increasing fraction nitrogen and decreasing sputtering pressure. It was found that the adherence of the coatings improves with decreasing sputtering pressure, almost independently of their composition.

Sensors for ceramic components in advanced propulsion systems

NASA Technical Reports Server (NTRS)

Koller, A. C.; Bennethum, W. H.; Burkholder, S. D.; Brackett, R. R.; Harris, J. P.

1995-01-01

This report includes: (1) a survey of the current methods for the measurement of surface temperature of ceramic materials suitable for use as hot section flowpath components in aircraft gas turbine engines; (2) analysis and selection of three sensing techniques with potential to extend surface temperature measurement capability beyond current limits; and (3) design, manufacture, and evaluation of the three selected techniques which include the following: platinum rhodium thin film thermocouple on alumina and mullite substrates; doped silicon carbide thin film thermocouple on silicon carbide, silicon nitride, and aluminum nitride substrates; and long and short wavelength radiation pyrometry on the substrates listed above plus yttria stabilized zirconia. Measurement of surface emittance of these materials at elevated temperature was included as part of this effort.

Triple-junction thin-film silicon solar cell fabricated on periodically textured substrate with a stabilized efficiency of 13.6%

NASA Astrophysics Data System (ADS)

Sai, Hitoshi; Matsui, Takuya; Koida, Takashi; Matsubara, Koji; Kondo, Michio; Sugiyama, Shuichiro; Katayama, Hirotaka; Takeuchi, Yoshiaki; Yoshida, Isao

2015-05-01

We report a high-efficiency triple-junction thin-film silicon solar cell fabricated with the so-called substrate configuration. It was verified whether the design criteria for developing single-junction microcrystalline silicon (μc-Si:H) solar cells are applicable to multijunction solar cells. Furthermore, a notably high short-circuit current density of 32.9 mA/cm2 was achieved in a single-junction μc-Si:H cell fabricated on a periodically textured substrate with a high-mobility front transparent contacting layer. These technologies were also combined into a-Si:H/μc-Si:H/μc-Si:H triple-junction cells, and a world record stabilized efficiency of 13.6% was achieved.

Hard carbon nitride and method for preparing same

DOEpatents

Haller, Eugene E.; Cohen, Marvin L.; Hansen, William L.

1992-01-01

Novel crystalline .alpha. (silicon nitride-like)-carbon nitride and .beta. (silicon nitride-like)-carbon nitride are formed by sputtering carbon in the presence of a nitrogen atmosphere onto a single crystal germanium or silicon, respectively, substrate.

Fabrication of nanopore and nanoparticle arrays with high aspect ratio AAO masks.

PubMed

Li, Z P; Xu, Z M; Qu, X P; Wang, S B; Peng, J; Mei, L H

2017-03-03

How to use high aspect ratio anodic aluminum oxide (AAO) membranes as an etching and evaporation mask is one of the unsolved problems in the application of nanostructured arrays. Here we describe the versatile utilizations of the highly ordered AAO membranes with a high aspect ratio of more than 20 used as universal masks for the formation of various nanostructure arrays on various substrates. The result shows that the fabricated nanopore and nanoparticle arrays of substrates inherit the regularity of the AAO membranes completely. The flat AAO substrates and uneven AAO frontages were attached to the Si substrates respectively as an etching mask, which demonstrates that the two kinds of replication, positive and negative, represent the replication of the mirroring of Si substrates relative to the flat AAO substrates and uneven AAO frontages. Our work is a breakthrough for the broad research field of surface nano-masking.

Fabrication of nanopore and nanoparticle arrays with high aspect ratio AAO masks

NASA Astrophysics Data System (ADS)

Li, Z. P.; Xu, Z. M.; Qu, X. P.; Wang, S. B.; Peng, J.; Mei, L. H.

2017-03-01

How to use high aspect ratio anodic aluminum oxide (AAO) membranes as an etching and evaporation mask is one of the unsolved problems in the application of nanostructured arrays. Here we describe the versatile utilizations of the highly ordered AAO membranes with a high aspect ratio of more than 20 used as universal masks for the formation of various nanostructure arrays on various substrates. The result shows that the fabricated nanopore and nanoparticle arrays of substrates inherit the regularity of the AAO membranes completely. The flat AAO substrates and uneven AAO frontages were attached to the Si substrates respectively as an etching mask, which demonstrates that the two kinds of replication, positive and negative, represent the replication of the mirroring of Si substrates relative to the flat AAO substrates and uneven AAO frontages. Our work is a breakthrough for the broad research field of surface nano-masking.

Integrated Microfluidic Gas Sensors for Water Monitoring

NASA Technical Reports Server (NTRS)

Zhu, L.; Sniadecki, N.; DeVoe, D. L.; Beamesderfer, M.; Semancik, S.; DeVoe, D. L.

2003-01-01

A silicon-based microhotplate tin oxide (SnO2) gas sensor integrated into a polymer-based microfluidic system for monitoring of contaminants in water systems is presented. This device is designed to sample a water source, control the sample vapor pressure within a microchannel using integrated resistive heaters, and direct the vapor past the integrated gas sensor for analysis. The sensor platform takes advantage of novel technology allowing direct integration of discrete silicon chips into a larger polymer microfluidic substrate, including seamless fluidic and electrical interconnects between the substrate and silicon chip.

Growing Cobalt Silicide Columns In Silicon

NASA Technical Reports Server (NTRS)

Fathauer, Obert W.

1991-01-01

Codeposition by molecular-beam epitaxy yields variety of structures. Proposed fabrication process produces three-dimensional nanometer-sized structures on silicon wafers. Enables control of dimensions of metal and semiconductor epitaxial layers in three dimensions instead of usual single dimension (perpendicular to the plane of the substrate). Process used to make arrays of highly efficient infrared sensors, high-speed transistors, and quantum wires. For fabrication of electronic devices, both shapes and locations of columns controlled. One possible technique for doing this electron-beam lithography, see "Making Submicron CoSi2 Structures on Silicon Substrates" (NPO-17736).

Flat-plate solar array progress and plans

NASA Technical Reports Server (NTRS)

Callaghan, W. T.

1984-01-01

The results of research into the technology of flat-plate solar arrays undertaken in the Flat-Plate Solar Array Project under the sponsorship of the U.S. Department of Energy are surveyed. Topics examined include Si refinement, ribbon-sheet substrate formation, module process sequences, environmental isolation, module engineering and testing, and photovoltaic-array economics.

Passivation of InGaAs(001)-(2 × 4) by Self-Limiting Chemical Vapor Deposition of a Silicon Hydride Control Layer.

PubMed

Edmonds, Mary; Kent, Tyler; Chagarov, Evgueni; Sardashti, Kasra; Droopad, Ravi; Chang, Mei; Kachian, Jessica; Park, Jun Hong; Kummel, Andrew

2015-07-08

A saturated Si-Hx seed layer for gate oxide or contact conductor ALD has been deposited via two separate self-limiting and saturating CVD processes on InGaAs(001)-(2 × 4) at substrate temperatures of 250 and 350 °C. For the first self-limiting process, a single silicon precursor, Si3H8, was dosed at a substrate temperature of 250 °C, and XPS results show the deposited silicon hydride layer saturated at about 4 monolayers of silicon coverage with hydrogen termination. STS results show the surface Fermi level remains unpinned following the deposition of the saturated silicon hydride layer, indicating the InGaAs surface dangling bonds are electrically passivated by Si-Hx. For the second self-limiting process, Si2Cl6 was dosed at a substrate temperature of 350 °C, and XPS results show the deposited silicon chloride layer saturated at about 2.5 monolayers of silicon coverage with chlorine termination. Atomic hydrogen produced by a thermal gas cracker was subsequently dosed at 350 °C to remove the Si-Cl termination by replacing with Si-H termination as confirmed by XPS, and STS results confirm the saturated Si-Hx bilayer leaves the InGaAs(001)-(2 × 4) surface Fermi level unpinned. Density function theory modeling of silicon hydride surface passivation shows an Si-Hx monolayer can remove all the dangling bonds and leave a charge balanced surface on InGaAs.

Directed dewetting of amorphous silicon film by a donut-shaped laser pulse.

PubMed

Yoo, Jae-Hyuck; In, Jung Bin; Zheng, Cheng; Sakellari, Ioanna; Raman, Rajesh N; Matthews, Manyalibo J; Elhadj, Selim; Grigoropoulos, Costas P

2015-04-24

Irradiation of a thin film with a beam-shaped laser is proposed to achieve site-selectively controlled dewetting of the film into nanoscale structures. As a proof of concept, the laser-directed dewetting of an amorphous silicon thin film on a glass substrate is demonstrated using a donut-shaped laser beam. Upon irradiation of a single laser pulse, the silicon film melts and dewets on the substrate surface. The irradiation with the donut beam induces an unconventional lateral temperature profile in the film, leading to thermocapillary-induced transport of the molten silicon to the center of the beam spot. Upon solidification, the ultrathin amorphous silicon film is transformed to a crystalline silicon nanodome of increased height. This morphological change enables further dimensional reduction of the nanodome as well as removal of the surrounding film material by isotropic silicon etching. These results suggest that laser-based dewetting of thin films can be an effective way for scalable manufacturing of patterned nanostructures.

Ultra-Thin Monocrystalline Silicon Solar Cell with 12.2% Efficiency Using Silicon-On-Insulator Substrate.

PubMed

Bian, Jian-Tao; Yu, Jian; Duan, Wei-Yuan; Qiu, Yu

2015-04-01

Single side heterojunction silicon solar cells were designed and fabricated using Silicon-On-Insulator (SOI) substrate. The TCAD software was used to simulate the effect of silicon layer thickness, doping concentration and the series resistance. A 10.5 µm thick monocrystalline silicon layer was epitaxially grown on the SOI with boron doping concentration of 2 x 10(16) cm(-3) by thermal CVD. Very high Voc of 678 mV was achieved by applying amorphous silicon heterojunction emitter on the front surface. The single cell efficiency of 12.2% was achieved without any light trapping structures. The rear surface recombination and the series resistance are the main limiting factors for the cell efficiency in addition to the c-Si thickness. By integrating an efficient light trapping scheme and further optimizing fabrication process, higher efficiency of 14.0% is expected for this type of cells. It can be applied to integrated circuits on a monolithic chip to meet the requirements of energy autonomous systems.

Silicon Satellites: Picosats, Nanosats, and Microsats

NASA Technical Reports Server (NTRS)

Janson, Siegfried W.

1995-01-01

Silicon, the most abundant solid element in the Earth's lithosphere, is a useful material for spacecraft construction. Silicon is stronger than stainless steel, has a thermal conductivity about half that of aluminum, is transparent to much of the infrared radiation spectrum, and can form a stable oxide. These unique properties enable silicon to become most of the mass of a satellite, it can simultaneously function as structure, heat transfer system, radiation shield, optics, and semiconductor substrate. Semiconductor batch-fabrication techniques can produce low-power digital circuits, low-power analog circuits, silicon-based radio frequency circuits, and micro-electromechanical systems (MEMS) such as thrusters and acceleration sensors on silicon substrates. By exploiting these fabrication techniques, it is possible to produce highly-integrated satellites for a number of applications. This paper analyzes the limitations of silicon satellites due to size. Picosatellites (approximately 1 gram mass), nanosatellites (about 1 kg mass), and highly capable microsatellites (about 10 kg mass) can perform various missions with lifetimes of a few days to greater than a decade.

Low-Temperature Growth of Amorphous Silicon Films and Direct Fabrication of Solar Cells on Flexible Polyimide and Photo-Paper Substrates

NASA Astrophysics Data System (ADS)

Madaka, Ramakrishna; Kanneboina, Venkanna; Agarwal, Pratima

2018-05-01

Direct deposition of hydrogenated amorphous silicon (a-Si:H) thin films and fabrication of solar cells on polyimide (PI) and photo-paper (PP) substrates using a rf-plasma-enhanced chemical vapor deposition technique is reported. Intrinsic amorphous silicon films were deposited on PI and PP substrates by varying the substrate temperature (T s) over 70-150°C to optimize the deposition parameters for best quality films. The films deposited on both PI and PP substrates at a temperature as low as 70°C showed a photosensitivity (σ ph/σ d) of nearly 4 orders of magnitude which increased to 5-6 orders of magnitude when the substrate temperature was increased to 130-150°C. The increase in σ ph/σ d is due to the presence of a few nanometer-sized crystallites embedded in the film. Solar cells (n-i-p) were fabricated directly on PI, PP and Corning 1737 glass (Corning) at 150°C for different thicknesses of an intrinsic amorphous silicon layer (i-layer). With the increase in i-layer thickness from 330 nm to 700 nm, the solar cell efficiency was found to increase from 3.81% to 5.02% on the Corning substrate whereas on the flexible PI substrate an increase from 3.38% to 4.38% was observed. On the other hand, in the case of cells on PP, the i-layer thickness was varied from 200 nm to 700 nm and the best cell efficiency 1.54% was obtained for the 200-nm-thick i-layer. The fabrication of a-Si (n-i-p) solar cells on photo-paper is presented for the first time.

Novel Approach for Positioning Sensor Lead Wires on SiC-Based Monolithic Ceramic and FRCMC Components/Subcomponents Having Flat and Curved Surfaces

NASA Technical Reports Server (NTRS)

Kiser, J. Douglas; Singh, Mrityunjay; Lei, Jin-Fen; Martin, Lisa C.

1999-01-01

A novel attachment approach for positioning sensor lead wires on silicon carbide-based monolithic ceramic and fiber reinforced ceramic matrix composite (FRCMC) components has been developed. This approach is based on an affordable, robust ceramic joining technology, named ARCJoinT, which was developed for the joining of silicon carbide-based ceramic and fiber reinforced composites. The ARCJoinT technique has previously been shown to produce joints with tailorable thickness and good high temperature strength. In this study, silicon carbide-based ceramic and FRCMC attachments of different shapes and sizes were joined onto silicon carbide fiber reinforced silicon carbide matrix (SiC/ SiC) composites having flat and curved surfaces. Based on results obtained in previous joining studies. the joined attachments should maintain their mechanical strength and integrity at temperatures up to 1350 C in air. Therefore they can be used to position and secure sensor lead wires on SiC/SiC components that are being tested in programs that are focused on developing FRCMCs for a number of demanding high temperature applications in aerospace and ground-based systems. This approach, which is suitable for installing attachments on large and complex shaped monolithic ceramic and composite components, should enhance the durability of minimally intrusive high temperature sensor systems. The technology could also be used to reinstall attachments on ceramic components that were damaged in service.

Investigation of the silicon ion density during molecular beam epitaxy growth

NASA Astrophysics Data System (ADS)

Eifler, G.; Kasper, E.; Ashurov, Kh.; Morozov, S.

2002-05-01

Ions impinging on a surface during molecular beam epitaxy influence the growth and the properties of the growing layer, for example, suppression of dopant segregation and the generation of crystal defects. The silicon electron gun in the molecular beam epitaxy (MBE) equipment is used as a source for silicon ions. To use the effect of ion bombardment the mechanism of generation and distribution of ions was investigated. A monitoring system was developed and attached at the substrate position in the MBE growth chamber to measure the ion and electron densities towards the substrate. A negative voltage was applied to the substrate to modify the ion energy and density. Furthermore the current caused by charge carriers impinging on the substrate was measured and compared with the results of the monitoring system. The electron and ion densities were measured by varying the emission current of the e-gun achieving silicon growth rates between 0.07 and 0.45 nm/s and by changing the voltage applied to the substrate between 0 to -1000 V. The dependencies of ion and electron densities were shown and discussed within the framework of a simple model. The charged carrier densities measured with the monitoring system enable to separate the ion part of the substrate current and show its correlation to the generation rate. Comparing the ion density on the whole substrate and in the center gives a hint to the ion beam focusing effect. The maximum ion and electron current densities obtained were 0.40 and 0.61 μA/cm2, respectively.

Optical detector having a plurality of matrix layers with cobalt disilicide particles embedded therein

NASA Technical Reports Server (NTRS)

Fathauer, Robert W. (Inventor); Schowalter, Leo (Inventor)

1994-01-01

Silicon and metal are coevaporated onto a silicon substrate in a molecular beam epitaxy system with a larger than stoichiometric amount of silicon so as to epitaxially grow particles of metal silicide embedded in a matrix of single crystal epitaxially grown silicon. The particles interact with incident photons by resonant optical absorption at the surface plasmon resonance frequency. Controlling the substrate temperature and deposition rate and time allows the aspect ratio of the particles to be tailored to desired wavelength photons and polarizations. The plasmon energy may decay as excited charge carriers of phonons, either of which can be monitored to indicate the amount of incident radiation at the selected frequency and polarization.

Deposition of device quality low H content, amorphous silicon films

DOEpatents

Mahan, A.H.; Carapella, J.C.; Gallagher, A.C.

1995-03-14

A high quality, low hydrogen content, hydrogenated amorphous silicon (a-Si:H) film is deposited by passing a stream of silane gas (SiH{sub 4}) over a high temperature, 2,000 C, tungsten (W) filament in the proximity of a high temperature, 400 C, substrate within a low pressure, 8 mTorr, deposition chamber. The silane gas is decomposed into atomic hydrogen and silicon, which in turn collides preferably not more than 20--30 times before being deposited on the hot substrate. The hydrogenated amorphous silicon films thus produced have only about one atomic percent hydrogen, yet have device quality electrical, chemical, and structural properties, despite this lowered hydrogen content. 7 figs.

Deposition of device quality low H content, amorphous silicon films

DOEpatents

Mahan, Archie H.; Carapella, Jeffrey C.; Gallagher, Alan C.

1995-01-01

A high quality, low hydrogen content, hydrogenated amorphous silicon (a-Si:H) film is deposited by passing a stream of silane gas (SiH.sub.4) over a high temperature, 2000.degree. C., tungsten (W) filament in the proximity of a high temperature, 400.degree. C., substrate within a low pressure, 8 mTorr, deposition chamber. The silane gas is decomposed into atomic hydrogen and silicon, which in turn collides preferably not more than 20-30 times before being deposited on the hot substrate. The hydrogenated amorphous silicon films thus produced have only about one atomic percent hydrogen, yet have device quality electrical, chemical, and structural properties, despite this lowered hydrogen content.

Nano-Welding of Multi-Walled Carbon Nanotubes on Silicon and Silica Surface by Laser Irradiation.

PubMed

Yuan, Yanping; Chen, Jimin

2016-02-24

In this study, a continuous fiber laser (1064 nm wavelength, 30 W/cm²) is used to irradiate multi-walled carbon nanotubes (MWCNTs) on different substrate surfaces. Effects of substrates on nano-welding of MWCNTs are investigated by scanning electron microscope (SEM). For MWCNTs on silica, after 3 s irradiation, nanoscale welding with good quality can be achieved due to breaking C-C bonds and formation of new graphene layers. While welding junctions can be formed until 10 s for the MWCNTs on silicon, the difference of irradiation time to achieve welding is attributed to the difference of thermal conductivity for silica and silicon. As the irradiation time is prolonged up to 12.5 s, most of the MWCNTs are welded to a silicon substrate, which leads to their frameworks of tube walls on the silicon surface. This is because the accumulation of absorbed energy makes the temperature rise. Then chemical reactions among silicon, carbon and nitrogen occur. New chemical bonds of Si-N and Si-C achieve the welding between the MWCNTs and silicon. Vibration modes of Si₃N₄ appear at peaks of 363 cm -1 and 663 cm -1 . There are vibration modes of SiC at peaks of 618 cm -1 , 779 cm -1 and 973 cm -1 . The experimental observation proves chemical reactions and the formation of Si₃N₄ and SiC by laser irradiation.

Effect of back reflectors on photon absorption in thin-film amorphous silicon solar cells

NASA Astrophysics Data System (ADS)

Hossain, Mohammad I.; Qarony, Wayesh; Hossain, M. Khalid; Debnath, M. K.; Uddin, M. Jalal; Tsang, Yuen Hong

2017-10-01

In thin-film solar cells, the photocurrent conversion productivity can be distinctly boosted-up utilizing a proper back reflector. Herein, the impact of different smooth and textured back reflectors was explored and effectuated to study the optical phenomena with interface engineering strategies and characteristics of transparent contacts. A unique type of wet-chemically textured glass-substrate 3D etching mask used in superstrate (p-i-n) amorphous silicon-based solar cell along with legitimated back reflector permits joining the standard light-trapping methodologies, which are utilized to upgrade the energy conversion efficiency (ECE). To investigate the optical and electrical properties of solar cell structure, the optical simulations in three-dimensional measurements (3D) were performed utilizing finite-difference time-domain (FDTD) technique. This design methodology allows to determine the power losses, quantum efficiencies, and short-circuit current densities of various layers in such solar cell. The short-circuit current densities for different reflectors were varied from 11.50 to 13.27 and 13.81 to 16.36 mA/cm2 for the smooth and pyramidal textured solar cells, individually. Contrasted with the comparable flat reference cell, the short-circuit current density of textured solar cell was increased by around 24%, and most extreme outer quantum efficiencies rose from 79 to 86.5%. The photon absorption was fundamentally improved in the spectral region from 600 to 800 nm with no decrease of photocurrent shorter than 600-nm wavelength. Therefore, these optimized designs will help to build the effective plans next-generation amorphous silicon-based solar cells.