bluuebunny/crossref_metadata_2025_split huggingface dataset:
In Situ Measurements of Hydrogen Flux, Surface Coverage, Incorporation and Desorption During Magnetron Sputter-Deposition of A-SI:H.
Authors: Abelson J. R. , Maley N. , Doyle J. R. , Feng G. F. , Fitzner M. , Katiyar M. , Mandrell L. , Myers A. M. , Nuruddin A. , Ruzic D. N. , Yang S. 
Published: March 2011

ABSTRACTHigh quality a-Si:H films are deposited by d.c. magnetron reactive sputtering of a Si target in an (Ar + H2) plasma. This paper reports the first comprehensive understanding of the growth process. The incident flux, surface H coverage, H2 release, and bulk H incorporation are determined using four in situ, real time techniques: double modulation mass spectroscopy, isotope replacement experiments, reflection absorption infra-red spectroscopy, and spectroscopic ellipsometry. In addition, the sputtered particle transport is simulated using Monte-Carlo techniques. For conditions which produce electronic quality a-Si:H, the total H flux arriving at the surface varies between 0.5 – 2 times the depositing Si flux; approximately half of this flux appears to reflect from the surface without interaction. The growth surface has excess H varying between 0.5 – 2 × 1015/cm2, and this surface H coverage is uniquely related to the bulk H incorporation.
Preparation of High-Quality a-SiGe:H films with Low Impurity Oncentration by the Hydrogen Dilution Method
Authors: Sayama Katsunobu , Haku Hisao , Dohjoh Hiroshi , Isomura Masao , Nakamura Noboru , Tsuda Shinya , Kishi Yasuo , Nakano Shouichi , Kuwano Yukinori 
Published: March 2011

ABSTRACTA-SiGe: H film properties with a low impurity concentration were investigated using a super chamber in the range of Ge content of 0% to 36%. These a-SiGe films can maintain a high photosensitivity of about 106 for Ge content up to 13%, which is comparable to high-quality a~Si films. It was found that impurity incorporation deteriorates optoelectronic properties in the range of a small amount of Ge content, and film rigidity in the range of a large amount of Ge content. Using high-quality a-SiGe films with a low impurity concentration in solar cells, the highest conversion efficiency of 3.15% was obtained for an a-SiGe single-junction cell under red light (AM-1.5, 100mW/cm2 light through the optical filter, in which the wavelength of transmitted light is longer than 650nm). A stacked cell of a-Si/a-Si/a-SiGe has a conversion efficiency of 11.9%.
Kinetics of Gas-Phase Chemical Reactions and Growth of a-SiC:H Films from Silane and Acetylene in a Remote Hydrogen Plasma Reactor
Authors: Johnson N. M. , Santos Paulo V. , Walker J. , Stevens K. S. 
Published: March 2011

ABSTRACTGas-phase chemical reactions of interest for the deposition of amorphous silicon carbide in a remote hydrogen plasma reactor have been quantitatively characterized with electron spin resonance, and the deposition of a-SiC:H from silane and acetylene is demonstrated.
Substrate Induced Crystallinity in Reactive Sputter Deposition of Hydrogenated Silicon
Authors: Feng G. F. , Katiyar M. , Abelson J. R. , Maley N. 
Published: March 2011

ABSTRACTWe use in situ multi-wavelength ellipsometry to study growth of hydrogenated amorphous silicon and crystalline silicon deposited by reactive DC magnetron sputtering. Crystal silicon covered with native oxide and oxide free crystal silicon are used as substrates. Deposition on c-Si/ox over a wide range of conditions yields amorphous films, and the growth proceeds with formation of small islands, regardless of hydrogen partial pressure. Growth on oxide free c-Si, on the other hand, is hydrogen dependent. Even at a low hydrogen pressure, a layer with mixed phase of c-Si and a-Si:H begin to appear near the c-Si substrate. This layer thickness and its c-Si fraction increase with hydrogen pressure. Bombardment of growing surface by energetic particles, both silicon and hydrogen species, appears to lead to the crystallization.
ArF Excimer Laser Doping into Amorphous Silicon thin films
Authors: Elliq M. , Slaoui A. , Fogarassy E. , Pattyn H. , Stuck R. , Siffert P. 
Published: March 2011

ABSTRACTDoping of amorphous silicon (a-Si or a-Si:H) coated by a spin-on oxide film containing the dopant (phosphorus or boron) using an ArF excimer laser has been investigated as a function of laser fluence, number of pulses and dopant film thickness. From these results, it is found that the surface concentration and the junction depth vary with the number of pulses, and that the doping process is rate limiting. Sheet resistance lower than 10 kΩ/□ have been obtained. It is also shown that for a-Si:H films, laser irradiation produces exodiffusion of hydrogen from the molten layer resulting in rough surface. This one-step process seems suitable for polycrystalline silicon thin film transistors (TFT's) fabrication.
Wide Bandgap Fluorinated Silicon-Carbide-Nitride Films Using NF3
Authors: Goh H. C. , Tan S. M. , Naseem H. A. , Ang S. S. , Brown W. D. 
Published: March 2011

ABSTRACTAmorphous hydrogenated silicon carbide has been studied extensively because of its properties as a wide bandgap material. However, a large amount of methane is needed to deposit the material. Also, the high carbon content of these films poses some problems. The addition of NF3 to the gas stream results in wide bandgap films with a substantial reduction in the required CH4 flow for deposition. Amorphous SiCx Ny :H:F films were prepared using rf glow discharge decomposition of silane, methane, and nitrogen trifluoride in a parallel-plate stainless steel reactor. Gas flow rate and power density were varied. For a gas mixture containing 6% NF3 and 78% CH4, FTIR measurements reveal a reduction in C-H peak heights at 2960 cm-1 and 2880 cm-1 with respect to the Si-H peak at 2080 cm-1 indicating a smaller carbon content in the film. The C-H peaks shift to higher wavenumbers with increasing NF3. The use of NF3 increases the bandgap from 2.6 to 3.14 eV while reducing the refractive index from 2.12. to 1.87. A maximum deposition rate of 625 A/min was achieved. This should be compared to the very low deposition rate of 18 A/min for comparable bandgap Si-C films deposited using 97% methane in silane. Increasing the deposition power density resulted in a larger bandgap and a smaller refractive index.
Methods of Improving Glow-Discharge-Deposited a-Si1−xGex:H
Authors: Tsuo Y. S. , Xu Y. , Ramsay E. A. , Crandall R. S. , Salomon S. J. , Balberg I. , Nelson B. P. , Xiao Y. , Chen Y. 
Published: March 2011

ABSTRACTWe have studied methods of improving glow-discharge-deposited a-Si1−x Gex :H alloys deposited using silane and germane gas mixtures. Material processing methods studied include (1) varying the substrate temperature from 170° to 280°C, (2) varying the process gas composition and pressure, (3) dilution of the feed gas by hydrogen, argon, or helium, (4) enhancing etching during deposition by adding small amounts of XeF2 vapor into the process gas, and (5) postdeposition annealing and/or hydrogenation.
Effects of Substrate Parameters on Amorphous-Crystalline Silicon Interface
Authors: Besi Vetrella U. , Cohen J. D. 
Published: March 2011

ABSTRACTCapacitance vs. temperature, deep-level transient spectroscopy (DLTS), and transient photocapacitance spectroscopy have been used to investigate the amorphous-crystalline silicon interface region of a device made of hydrogenated amorphous silicon deposited on a lightly doped n-type crystalline silicon.By comparing our results between substrates with and without oxide contamination with those in a earlier study, we have been able to correlate the effects of substrate preparation on the density of interface states.
A-Si:H Ambipolar Diffusion Length and Effective Lifetime Measured by Flying Spot Technique (FST)
Authors: Vieira M. , Martins R. , Fortunato E. , Soares F. , Guimaraes L. 
Published: March 2011

ABSTRACTThe determination of the ambipolar diffusion length, L*, and the effective lifetime, τ*, in p/i and a-Si:H Schottky barriers (ITO/p/a-Si:H/Al-Si; Cr/a-Si:H/Cr/Ag) have been determined by Flying Spot Technique, FST. This technique consists in the transient analysis of the photocurrent/photopotential induced by a laser beam that moves perpendicularly to the structure with a constant motion ratio, at different velocities. Taking into account the competition between the diffusion/drift velocities of the excess carriers and the velocity of the flying spot, it is possible to solve the transport equations and to compute separately L* and τ*, from the asymmetrical distribution responses.
High Pressure Studies of Liquid Crystalline Transitions
Authors: Shashidhar R. 
Published: March 2011

ABSTRACTSome of the important results emerging from our recent investigations
on liquid crystals at high pressure are presented. In particular the following topics will be discussed:
i) The relation between Pm, the maximum pressure of smectic stability, and the temperature range of the nematic phase in reentrant nematogenic compounds.
ii) Piezothermal studies in the vicinity of the smectic A-nematic transition in 8 OCB.
iii) The effect of molecular ordering on the pressure behaviour of the nematic-isotropic transition in reentrant nematic mixtures.
iv) The first observation of a multicritical point in a single component liquid crystal.
Photoluminescence of Bis-Tetrabutylammonium Tetrabromomanganate to 440 K and 3 Kbar
Authors: VöGele H.P. , TöDheide K. 
Published: March 2011

ABSTRACTThe absorption and emission spectra and the phosphorescence decay time of bis-tetrabutylammonium tetrabromomanganate-(II) were measured to 440 K and 3 kbar. In addition the melting pressure of the salt and its viscosity and electrical conductivity at normal pressure were determined as functions of temperature.
Metastability in the H2O and D2O Systems at High Pressure
Authors: Piermarini G. J. , Munro R. G. , Block S. 
Published: March 2011

ABSTRACTThe pressure and temperature parameters which delineate the equilibrium thermodynamic stability fields of the liquid, VI and VII phases, includinq the triple point, were measured for the H2;0 and D2;0 systems over the pressure range, 0.8 to 2.4 GPa, and the temperature interval, 20 to 135 °C. The phenomenon of metastability associated with the liquid-VII phase boundary was observed during this work; and, subsequently, a metastable extension of this coexistence curve was determined from the liquid-VI-VII triple point down to 20 °C for both H2;0 and D2;0. The measurements were made by optical polarizing microscopy in conjunction with a diamond anvil cell equipped with a miniature resistance coil heatinq element. Pressures were measured by the ruby fluorescence method.
Effects of Viscosity, Temperature, and Rate of Rotation on the Operation of a Controlled-Clearance Piston Gauge
Authors: Sharma J.K.N. , Jain Kamlesh K. , Bean Vern E. , Welch B.E. , Lazos Ruben J. 
Published: March 2011

ABSTRACTThe calculation of the pressure generated by a controlled clearance piston gauge depends upon the jacket pressure corresponding to zero clearance between the piston and cylinder, Pz;. The dependence of Pz; on the viscosity of the pressure transmitting fluid, the temperature, and the rate of piston rotation has been measured.The value of Pz; is nearly independent of viscosity below 60 cp. Above 60 cp, Pz; depends strongly upon viscosity. Variations of Pz; with femperature and rate of rotation are more severe at figher viscosities.These results are a clear indication that for the most accurate pressure measurements, a controlled-clearance piston gauge must be characterized using the same operational and environmental conditions with the same fluid as in normal operation.
Power Law Behavior of the Pressure Dependence of Expansivity in the Liquid Hexane as a Model for Liquids. Limit of Thermodynamic Stability
Authors: Pruzan Ph. 
Published: March 2011

ABSTRACTIn this work a power lay is used to fit the isothermal pressure dependence of the expansivity α = V−1(∂V/∂T)p of liquid hexane. This functional form is also observed to fit the expansivity and the isothermal compressibility KT = −V−1(∂V/∂P)T data of the three liquids : hexane, argon, carbon dioxide.
PVT Measurements and Critical Parameters of Water
Authors: Hanafusa H. , Kawai K. , Sato H. , Uematsu M. , Watanabe K. 
Published: March 2011

ABSTRACTThe PVT properties and vapor-pressures of water have been measured in the critical region by using a constantvolume apparatus immersed in the constant-temperature bath with the procedure of varying the sample mass along a prescribed isotherm. Ninety-one PVT and five vapor-pressure measurements along 11 isotherms cover the region of temperatures 643 to 673 K and of pressures 19.7 to 38.6 MPa, which corresponds to a density variation from 108 to 618 kg/m3. The experimental uncertainties of temperature, pressure and density are estimated 4 mK, 5 kPa and 0.04%, respectively. Based on these measurements, the critical parameters of water are proposed to be 647.061 K, 22.041 MPa and 322.4 kg/m3 by the scaling law analysis.
Apparatus for the Measurement of Isothermal and Adiabatic Compressibility of Gases up to 10 Kbar
Authors: Biswas S.N. , Muringer M.J.P. , Trappeniers N.J. 
Published: March 2011

ABSTRACTA pVT apparatus based on a combination of gas expansion and isochoric method and an ultrasonic apparatus for sound velocity measurements based on phase comparison pulse-echo technique have been developed for precise measurements of isothermal and adiabatic compressibility of gases at pressures up to 10 kbar and temperatures down to the melting line.
Aqueous Mixtures with Nonpolar Gases at High Pressures and Supercritical Temperatures
Authors: Franck E.U. 
Published: March 2011

ABSTRACTPTx-phase diagrams and critical curves for binary aqueous systems are briefly discussed. New results of the two-phase boundary surface and the critical curve for the water-nitrogen system to 2500 bar and 400°C are presented as isotherms in the Px-plane. A new extended Carnahan-Starling and squarewell type equation permits calculations of spinodal isopleths of the water-methane system and a prediction of the critical curve. - Excess volumes of supercritical benzene-water mixtures are given as functions of composition and pressure. Excess Gibbs energies and activity coefficients are derived. For the same system the static dielectric constant was measured between 300 and 400 °C in the homogeneous supercritical fluid for all concentrations. At 400 °C and 2000 bar the dielectric constant of pure water is 20 and decreases steeply with the addition of benzene. Addition of water to benzene causes at first only a slow increase above the value of 2 (for pure benzene). A short discussion of the description of the dielectric constant of such polar-nonpolar mixtures for wide ranges of density is given. - The solubility of anthracene in high density water to 250 °C was measured spectroscopically. Data are given. The “enhancement factor” is high at low temperature but decreases to unity at 250 °C and a water density of 1 g . cm−3
X-Ray and Raman Studies of Interlayer Mixing in SimGem Superlattices
Authors: Bowman R. C. , Adams P. M. , Chang S. J. , Arbet-Engels V. , Wang K. L. 
Published: March 2011

ABSTRACTInterface mixing between the Ge and Si layers in symmetrically strained SimGem superlattices occurs during post growth thermal anneals. Interdiffusion coefficients were obtained from intensity changes in the low angle superlattice x-ray satellites on samples with nominal periodicities between 1.4nm and 5.6nm. A common activation energy of 3.0±0.1 eV was found. The bulk interdiffusion coefficients for SimGem were derived since measurements were made on samples with different layer thicknesses. Intermixing appears to occur by diffusion of Si atoms into the Ge layers via a vacancy mechanism. Raman scattering measurements support this process as well as the formation of Si1−xGex, alloy layers during the anneals.
Defect Centers Formed During Wet Oxidation of Si-Ge/Si Heterostructures
Authors: Zvanut M. E. , Carlos W. E. , Prokes S. M. , Stahlbush R. E. 
Published: March 2011

ABSTRACTGermanium incorporated oxide films formed by wet oxidation of SiGe substrates have been studied using Electron Paramagnetic Resonance. SiGe layers 400 nm thick were prepared by molecular beam epitaxy and oxidized in a steam ambient at 900° C. After a 10 Mrad x-ray irradiation, an oxide defect with a zero crossing at g=1.995 is observed. Comparison of the spectrum with that obtained from Ge-doped silica suggests that the defect observed in the thin film is an oxygen vacancy related defect, a Ge E' center.
Low Temperature Hydrogen Plasma Cleaning Processes of Si (100), Ge (100), and SixGe1−x (100)
Authors: Schneider T. P. , Aldrich D. A. , Cho J. , Nemanich R. J. 
Published: March 2011

ABSTRACTWet chemical and in situ hydrogen plasma cleaning processes were studied and a low temperature cleaning process was developed for Si (100), Ge (100) and SixGe1−x (100) surfaces. A uv-ozone and HF based spin etch were used to initially remove contaminants and oxides from the Si (100) and SixGe1−x (100) surfaces. The Ge (100) surfaces were treated with deionized water prior to entry to UHV. Residual gas analysis (RGA) was used in the investigation of the surface removal process of the in situ H-plasma cleaning. Low Energy Electron Diffraction (LEED) and angle resolved UV-Photoemission Spectroscopy (ARUPS) were used to examine the surface structure and electronic states. The 2×1 LEED patterns were obtained for Si (100), Ge (100) and SixGe1−x (100) after cleaning at a maximum processing temperature of 300°C. By varying process conditions, the LEED showed the 1×1 and 2×1 surface diffraction patterns. The ARUPS spectra showed the electronic states and the chemistry of the cleaned surfaces.
X-Ray Study of Non-Periodic Si/SiGe Multilayers
Authors: Herzog H. -J. , Kibbel H. , Schäffler F. 
Published: March 2011

ABSTRACTX-ray diffraction is applied for the assessment of structural data such as lattice mismatch and layer thickness of MBE grown Si/Si1−xGex heterobipolar transistor and double-barrier resonant-tunneling structures. Rocking curves from the former structure show distinct features which are obviously correlated to the individual layer parameters. The diffraction profile of the resonant tunneling structure is not only more complicated because of the larger number of parameters but also due to the strong interference effects resulting from the layer set-up. For a determination of the structural parameters a comparison of the experimental diffraction pattern with simulated rocking curves is performed.
The Effect of Oxygen on the Thermal Stability of Si1−xGex Strained Layers Grown by Limited Reaction Processing
Authors: Noble D. B. , Hoyt J. L. , Kuo P. , Nix W. D. , Gibbons J. F. , Laderman S. S. , Turner J. E. , Rosner S. J. , Scott M. P. 
Published: March 2011

ABSTRACTSi1−xGex layers containing 2×1020 oxygen atoms/cm3 exhibit an enhancement in thermal stability when compared to similar films (comparable Ge content and thickness) with 2 orders of magnitude less oxygen. X-ray measurements of the lattice constants in the strained films indicate that the oxygen does not substantially change the amount of strain in the layers. A prediction of the effect of oxygen based on solid solution strengthening theory is shown to be consistent with experimental annealing results. In addition, experimental measurements of slower misfit dislocation velocities in the layers with high oxygen content compared to those measured in films with low oxygen content, support the idea of solid solution strengthening. It is therefore likely that oxygen impedes the kinetics of dislocation formation.
Wet Oxidation of Epitaxial Ge.36Si.64 on (100)Si
Authors: Liu W. S. , Bai G. , Nicolet M-A. , Chern C. H. , Arbet V. , Wang K. L. 
Published: March 2011

ABSTRACTThe thermal oxidation of epitaxial Ge.36Si.64 on (100)Si is investigated experimentally for a wet ambient at 700°C and 1000°C. A pure silicon dioxide layer with pile-up of Ge behind the oxide is formed at 1000°C. At 700°C, however, both Ge and Si are oxidized. The Ge is included uniformly into the oxide layer without changing the initial Ge/Si ratio. The result at 1000°C follows the thermodynamical picture which predicts the same result at 700°C also, contrary to observation. The different result at 700°C is due to kinetic constraints which can be explained by different activation energies for the rate of the oxidation reaction and for the Ge or Si diffusivities in GeSi.
MBE Growth and Characterization of SxGe1−x Multilayer Structures on Si (100) for Use as a Substrate for GaAs Heteroepitaxy
Authors: Posthill J. B. , Malta D. P. , Venkatasubramanian R. , Sharps P. R. , Timmons M. L. , Markunas R. J. , Humphreys T. P. , Parikh N. R. 
Published: March 2011

ABSTRACTInvestigation has continued into the use of SixGe1−x multilayer structures (MLS) as a buffer layer between a Si substrate and a GaAs epitaxial layer in order to accommodate the 4.1% lattice mismatch. SixGe1−x 4-layer and 5-layer structures terminating in pure Ge have been grown using molecular beam epitaxy. Subsequent GaAs heteroepitaxy has allowed evaluation of these various GaAs/SixGe1−xMLS/Si (100) structures. Antiphase domain boundaries have been eliminated using vicinal Si (100) substrates tilted 6° off-axis toward [011], and the etch pit density in GaAs grown on a 5-layer SixGe1−x MLS on vicinal Si (lOO) was measured to be 106 cm−2.
Deep Luminescence from ‘Relaxed’ Si1−xGex Epitaxial Layers
Authors: Davies Gordon , Higgs Victor , Kubiak Richard , Powell Adrian , Whall Terry , Parker Evan 
Published: March 2011

ABSTRACTIn MBE Si1−xGex which is grown to thicknesses greater than the critical thickness hc, the dislocation-related luminescence peaks Dl and D2 have energies which are independent of x up to x ≈ 0.3, and then decrease, as observed in LPE Si1−xGex. In MBE Si1−xGex layers grown to thicknesses less than hc, post-growth annealing produces dramatic changes in the luminescence, giving spectra as from relaxed alloy, even though the relaxation determined by X-rays is negligible. These results establish photoluminescence as a sensitive diagnostic tool for detecting dislocations in Si1−xGe*.
Raman Study of Strain and Confinement Effects in Si/Ge Strained Layer Superlattices Under Hydrostatic Pressure
Authors: Sui Zhifeng , Herman Irving P. , Bevk Joze 
Published: March 2011

ABSTRACTThe effects of strain and confinement on optical phonons in a Si12Ge4 strained layer superlattice grown by MBE on c-Si (001) were studied as a function of hydrostatic pressure (T = 295 K) using Raman scattering. The change of phonon frequency with pressure, dω/dP, for the principal quasi-confined LO mode in the Ge layers is found to be significantly smaller than that for bulk crystalline Ge because the magnitude of biaxial strain decreases in the Ge layers with added pressure and because the Grüneisen parameter of the confined mode is smaller than that of the Γ-point optical phonon. More generally, it is noted that the magnitude of biaxial strain in many strained layer superlattices initially decreases with the application of hydrostatic pressure, making the structures more stable.
Intersubband Absorption in the Conduction Band of Si/Si1−xGex Multiple Quantum Wells
Authors: Hertle H. , Schuberth G. , Gornik E. , Abscreiter G. , Schäffler F. 
Published: March 2011

ABSTRACTThe intersubband absorption of electrons in modulation doped Si/Si1−xGex multiple quantum wells has been observed [1]. Various samples with different well widths and carrier densities have been studied. Narrow absorption lines are observed in waveguide geometry. Self consistent subband calculations are in good agreement with the experimental values.