bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Spectral Effect on Phase Evolution in Neutron-Irradiated Aluminum?
Authors: Farrell K. 
Published: April 2011

AbstractIt is proposed that the spatial distribution of transmutation-produced silicon precipitates formed in aluminum by capture of thermal neutrons is systematically modified by the fast neutron portion of the spectrum, and the tensile strength is altered accordingly. The concept is used to rationalize some previously erratic tensile data.
Microstructural Characterization of Iron Implanted Sapphire Nanocomposites
Authors: Ren Shelly X. , Mchargue Carl J. , Allard L. F. , Chen Y. , Hunn J. D. , Lucas B. N. , Williams R. K. 
Published: April 2011

AbstractNanocomposites of iron in sapphire (α-A12 O3) prepared by ion implantation have been studied as a model to investigate the potential of such materials for applications in high technology areas. The implantation was performed with 160 keV ions at several doses; the nanocomposites were then annealed at selected temperatures between 700 and 1400°C in an Ar-4&H2 atmosphere for 1 hour. Rutherford backscattering spectroscopy and high resolution transmission electron microscopy (TEM) were used to characterize the structure of these nanocomposites. Measurements showed that damage depth extended to about 300 nm and the embedded iron extended to about 200 nm. This region became amorphous when the fluence reaches 2x1017 Fe/cm2 at this energy. At this dose, oriented precipitates with diameters of 2 to 3 nm were identified by TEM techniques as α-Fe which had the following orientation relationship with the sapphire matrix: <111>Fe||<310>Sapphire and (011)Fe||{006}sapphire. Thermal annealing could be used to restore the crystallinity to the damaged near-surface region, to form the metallic colloids, and also to coarsen the precipitates. The optical density and luminescence spectra were also measured. The predominant defects were oxygen vacancies with two electrons (F center) at the known absorption peak of 200 nm.
Defects Induced by Protons and γ-Rays in Semi-Insulating Gaas Detectors
Authors: Castaldini A. , Cavallini A. , Del Papa C. , Fuochi G. , Alietti M. , Canali C. , Nava F. , Paccagnellam A. , Lanzieriv C. 
Published: April 2011

AbstractSemi-insulating gallium arsenide has been irradiated by protons and by gamma-rays with different doses. The irradiation-induced deep level defects have been investigated by current transient spectroscopy to find their energy, capture cross sections and generation rate.Two electron traps at Ec+0.14eV(E13) and Ec-0.70eV(E4) and a hole trap at Ec-0.14eV(H2) in addition to the levels existing before the irradiation have been detected in the irradiated samples. These findings have been related to the performance of gallium arsenide charge particle detectors.
Effect of Contacts on Capacitance Transient Measurements in N-Type Hydrogenated Amorphous Silicon
Authors: Jackson W. B. , Johnson N. M. , Walker J. 
Published: April 2011

ABSTRACTMeasurement of the dependence of emission capacitance transients on filling pulse duration has been extended to devices with Ohmic back contacts. Capacitance transients on devices possessing identical bulk 20-ppm P doped a-Si:H but either Ohmic contacts or blocking contacts were compared. The devices with blocking contacts completely reproduced in quantitative detail the previously observed anomalous dependence of capacitance transients on filling pulse duration. The diodes with Ohmic contacts showed no evidence of the anomalous filling pulse effect even for light-degraded, resistive samples. Current injection measurements show that blocking contacts delay the charge injection into the device by about 10–100 msec.
Nanostructure of a-Si:H and Related Materials by Small-Angle X-Ray Scattering
Authors: Williamson D. L. 
Published: April 2011

ABSTRACTThe use of small-angle x-ray scattering to examine nanostructural features of a-Si:H and the related alloys a-SiGe:H and a-SiC:H will be reviewed. A wide range of H, Ge, and C compositions has been investigated. The films examined came from several film- and device-making groups and represent current state-of-the-art solar cell material or attempts to develop improved and more stable material. A detailed comparison of the three classes of materials reveals dramatic differences in nanostructure. The diffuse component of the small-angle scattering, not recognized or discussed in previous small-angle scattering experiments on these materials by other groups, is shown to contain potentially valuable information on the atomic-scale structure.
Carrier Recombination in A-SI:H P-I-N Devices Studied by PL and EL Spectroscopies
Authors: Yeh C. N. , Han D. X. , Wang K. D. , McNeil L. E. 
Published: April 2011

ABSTRACTBoth photoluminescence (PL) and electroluminescence (EL) energy spectra were studied in the temperature range of 80 to 300 K on a-Si:H p-i-n structures. The EL spectrum depends on several parameters such as the i-layer thickness and the sample structure with or without a buffer layer (b-layer), while the PL spectrum shows no difference when those parameters are varied. Comparing PL and EL in 0.5 μm p-i-n devices with and without a buffer layer, we found that (a) at 80 K, the main-band peak energy is 1.3 eV for PL and 1.2 eV for EL; (b) the PL spectral line shape does not change with the insertion of a buffer layer, but the EL spectra show more enhanced main-band luminescence with the buffer layer; (c) the temperature dependence of the PL intensity shows a slope of 26 K which is similar to that of a-Si:H films, but the EL efficiency shows a weaker temperature dependence that varies with the diode structure.
Effect of Light Soaking on Hot Wire Deposited a-Si:H Films
Authors: Kwon Daewon , David Cohen J. , Nelson Brent P. , Iwaniczko Eugene 
Published: April 2011

ABSTRACTWe present the results of studies on the defect properties and the effect of light soaking for various hot wire deposited (HW) films. We employ junction capacitance measurements together with the transient photocapacitance spectroscopy to measure the deep defect densities in as-grown state (state A) and in light soaked state (state B). Good agreement is found between the defect densities measured from both measurements. The HW film with a hydrogen content of 10 – 12 at.% shows physical characteristics and defect densities similar to conventional PECVD films. The HW films with hydrogen content, CH, in the range 2 – 9 at.% show a smaller defect density in state B than the defect density of the film with higher CH. However, the film with a hydrogen level of less than 1 at.% exhibits markedly inferior physical properties.
Light-Induced Metastable Changes in a-SiSx:H
Authors: Wang S. L. , Taylor P. C. 
Published: April 2011

ABSTRACTMetastable light-induced increases in the dark conductivities of a-SiSx:H alloys are explained as photo-activation of hydrogen-passivated sulfur donor sites. For a sulfur concentration (sulfur-to-silicon ratio) of 5.6 × 103 the excess dark conductivity as a function of illumination temperature is thermally activated with an activation energy of 0.72 eV. When the sulfur concentration is 3.3 × 102, the temperature dependence is very weak. This dramatic difference in the temperature dependence of the creation of increased dark conductivity is explained by a lowering of the annealing temperature for the metastable changes as the sulfur concentration increases. We discuss the influence of this new metastability on the possibility of obtaining more stable films.
An Expanding Thermal Plasma for Deposition of a-Si:H
Authors: Severens R. J. , Brussaard G. J. H. , Verhoeven H. J. M. , Van de Sanden M. C. M. , Schram D. C. 
Published: April 2011

ABSTRACTA remote argon/hydrogen plasma is used to deposit amorphous hydrogenated silicon. The plasma is generated in a DC thermal arc (typical operating conditions 0.5 bar, 5 kW) and expands into a low pressure chamber (20 Pa) thus creating a plasma jet with a typical flow velocity of 103 m/s. Pure silane is injected into the jet immediately after the nozzle, in a typical flow mixture of Ar:H2:SiH4=55:10:6 scc/s. The electron temperature in the jet is low (typ. 0.3 eV) : silane radicals are thought to be produced mainly by hydrogen abstraction, but also by a sequence of dissociative charge exchange and consecutive dissociative recombination. In-situ ellipsometry yields refractive indices of 3.6–4.2 at 632.8 nm and growth rates of 10–20 nm/s. FTIR analysis yields a hydrogen content of 9–25 at.% and refractive indices of 2.7–3.3 in the infrared. The SiH density decreases with increasing hydrogen content, whereas the SiH2 density increases. Above 11 at.%, the majority of hydrogen is bonded in the SiH2 configuration. The optical bandgap remains constant at approximately 1.72 eV. The photoconductivity is of the order 101–6 (Ωcm) 1–6 and the photoresponse 106.
Pulsed-Light-Induced Metastable Defect Creation in Hydrogenated Amorphous Silicon
Authors: Yoon Jong-Hwan , Kim H. L. 
Published: April 2011

ABSTRACTWe report the results of a study of metastable defect creation by pulsed light soaking in undoped hydrogenated amorphous silicon (a-Si:H). An illumination time dependence of the defect density, a saturated defect density, and light-induced annealing under pulsed laser light have been studied. Measurements show approximately a t1/2 time-dependence of the defect creation, which is independent of light intensity. It is observed that the saturation value of the defect density is about one order of magnitude higher than by cw illumination in device quality films. It has been suggested that these results would be due to the difference in the light-induced defect annealing rate between cw and pulsed lights, in which it is found that the light-induced annealing rate by pulsed light is lower than by cw light.
Study of Electron Transport in a-Si:H p-i-n Diodes: Use of the Transient Space-Charge-Limited-Current Technique
Authors: Adriaenssens G. J. , Yan B. , Eliat A. 
Published: April 2011

ABSTRACTA full and detailed transient space-charge-limited current (T-SCLC) study of a-Si:H p-i-n diodes has been carried out in the time range from 108s to 10s. In the short-time regime, general features of T-SCLC such as the current cusp and the carrier extraction period were observed, and related transport parameters were deduced. Electron emission from deep states was studied by measuring the current transients well beyond the extraction time. The emission time is thermally activated at temperatures higher than 250K and levels off at lower temperatures. The high temperature behaviour places the upper edge of the deep states at 0.42–0.52eV below the conduction band edge, and the attempt-to-escape frequency in the range of 1011-1013Hz. An observed shift of emission time with light intensity is attributed to defect relaxation.
Transient Infrared Stimulated Photoconductivity in a-SI:H at Low Temperatures
Authors: Heck S. , Stradins P. , Fritzsche H. 
Published: April 2011

ABSTRACTDual beam photoconductivity with bandgap primary light and hv = 0.4- 0.6eV infrared light steps was measured with Ims time resolution in hydrogenated amorphous silicon (a-Si:H) at 4.2K. The results can be described by assuming that the photocurrent transients are due to energy-loss hopping of photocarriers and that the infrared light promotes recombination by reexciting photocarriers thereby enhancing the probability of tunneling recombination.
Analytical approach for transient photoconductivity in undoped a-Si:H
Authors: Goerlitzer M. , Pipoz P. , Beck H. , Wyrsch N. , Shah A. V. 
Published: April 2011

ABSTRACTTransient photoconductive response of undoped a-Si:H has been studied; the changes were analysed between two slightly different steady-state illumination conditions, at room temperature. A theoretical model is developed to describe transient photoconductivity; it yields good agreement with the measured curves for a whole range of light intensities. Numerical evaluations allows one to extract the recombination time of electrons. Comparison with steady-state photoconductivity yields a band mobility of free electrons between 0.1 and 6 cm2V−1s−1, depending upon sample quality.
Improved Ambipolar Diffusion Length in a-Si1-xGex:H Alloys for Multi-Junction Solar Cells
Authors: Fölsch J. , Finger F. , Kulessa T. , Siebke F. , Beyer W. , Wagner H. 
Published: April 2011

ABSTRACTTo prepare hydrogenated amorphous silicon-germanium alloys as low gap material for multi-junction solar cells in plasma enhanced chemical vapour deposition, the well established concept of strong dilution of the process gases with hydrogen has been used. Two different regimes of alloying were found: for low Ge content (x < 0.40) we observe material with low defect density, small Urbach energy and high values of the ambipolar diffusion length. In the regime of high Ge content (x > 0.40) the defect densities and Urbach energies are high and the values of the ambipolar diffusion length low. The transition is accompanied by the appearance of a low-temperature peak in hydrogen effusion experiments indicating a void rich film structure. Material from just above and below the transition zone is used in pin solar cells leading to a much enhanced red response compared with a-Si:H cells. The differences seen in the material quality are mirrored in the solar cell properties. By carefully adjusting the active layer thickness material with low diffusion length shows also reasonable solar cell performance.
Utilization of Amorphous Silicon Carbide (a-Si:C:H) as a Resistive Layer in Gas Microstrip Detectors
Authors: Hong W. S. , Cho H. S. , Perez-Mendez V. , Gong W. G. 
Published: April 2011

ABSTRACTThin semiconducting films of hydrogenated amorphous silicon (a-Si:H) and its carbon alloy (a-Si:C:H) were applied to gas microstrip detectors in order to control gain instabilities due to charges on the substrate. Thin (∼100 nm) layers of a-Si:H or p-doped a-Si:C:H were placed either over or under the electrodes using the plasma enhanced chemical vapor deposition (PECVD) technique to provide the substrate with a suitable surface conductivity. By changing the carbon content and boron doping density, the sheet resistance of the a-Si:C:H coating could be successfully controlled in the range of 1012 ∼ 1017 μ/□, and the light sensitivity, which causes the resistivity to vary with ambient light conditions, was minimized. An avalanche gain of 5000 and energy resolution of 20% FWHM were achieved and the gain remained constant over a week of operation. A-Si:C:H film is an attractive alternative to ion-implanted or semiconducting glass due to the wide range of resistivities possible and the feasibility of making deposits over a large area at low cost.
Brightness Degradation Controlled by Current Induced Metastable Defect Creation in a-SiC:H Based Light Emitting Diodes
Authors: Rizzoli R. , Summonte C. , Galloni R. , Ruth M. , Desalvo A. , Zignanf F. , Rava P. , Demichelis F. , Pirri C. F. , Tresso E. , Crovini G. , Giorgis F. , Madan A. 
Published: April 2011

ABSTRACTA study of the electroluminescence degradation of a-SiC:H based light emitting devices (LED) is presented for the first time. The best initial peak brightness obtained is 4.2 cd/m2. All LEDs reported in this paper emit a red light which, when operated under continuous bias in a not fully darkened room, is visible for several minutes, depending on degradation rate. The time dependence of LED degradation, which is reversible upon annealing, can be explained if self-annealing is taken into account. There is evidence of an improved LED performance for lower temperature operation. Pulsed operation, with respect to dc operation, produces a markedly lower defect production rate, associated to a higher brightness after degradation. The possibility of some optimization of the operation parameters (peak current, duty cycle) is discussed.
Phase separation of Si1-xGex alloys
Authors: Kim Eunja , Lee Young Hee 
Published: April 2011

AbstractWe generate liquid and amorphous Si1_xGex alloys for various Ge compositions using ab initio molecular dynamics approach. The electronic bonding characters and structural properties are discussed in terms of radial distribution function, bond angle distribution, and order parameters. Although the order parameters suggest approximately random alloy for all compositions, the snapshots reveal clearly phase separation. We will discuss how the phase can be separated in SiGe alloy system.
Nucleation & Growth of Defects in SOI Materials
Authors: Silvestre G. C. M. , Moore R. A. , Kennedy B. J. 
Published: April 2011

AbstractTo produce Silicon-On-Insulator (SOI) materials with thin Si overlayer, sacrificial oxidation is often used. This creates defects which have adverse effects on device performance. It has been observed that Stacking Faults (SFs) in thin Separation-by-IMplantation-of-OXygen (SIMOX) or Bonded-and-Etched-back-SOI (BESOI) films of less than 600 Å, do not shrink as expected during neutral Ar anneals. Shrinkage of SFs in standard bulk substrates with different capping layers has been investigated to promote the understanding of the Si/Si02 interface effects on Si interstitial incorporation during anneals. The activation energy for growth and shrinkage of SOI samples thicker than 800 A was found to be the same as bulk Si: 2.3 eV (growth) and 4.6 eV (shrinkage). Bulk silicon implanted with low doses of oxygen, permitted investigation of the nucleation sites of SFs in SIMOX where oxygen precipitates are believed to act as nuclei for SFs. A five step etch procedure was modified to reveal the defects in very thin SOI and an automatic defect counting system developed at T.C.D. permitted fast and reliable measurements of size and density of the defects. It appears that the two Frank partial dislocations that bound SFs, are pinned at the two Si/Si02 interfaces for both SIMOX and BESOI films thinner than 500 Å. In thicker SOI, the mechanisms for growth and shrinkage of SFs are the same as for bulk silicon.
Low-Temperature, Solid-Phase Epitaxial Growth of Amorphized, Non-Stoichiometric GaAs
Authors: Belay K. B. , Llewellyn D. L. , Ridgway M. C. 
Published: April 2011

AbstractNon-stoichiometric GaAs layers with semi-insulating properties can be produced by low-temperature molecular beam epitaxy or ion implantation. The latter is the subject of the present report wherein the solid-phase epitaxial growth of amorphized, non-stoichiometric GaAs layers has been investigated with time-resolved reflectivity, Rutherford backscattering spectrometry and transmission electron microscopy. GaAs substrates were implanted with Ga and/or As ions and annealed in air at a temperature of 260°C. The recrystallized material was composed of a thin, crystalline layer bordered by a thick, twinned layer. Non-stoichiometry results in a roughening of the amorphous/crystalline interface and the transformation from planar to non-planar regrowth. The onset of the transformation and the rate thereof can increase with an increase in non-stoichiometry. Non-stoichiometry can be achieved on a macroscopic scale via Ga or As implants or on a microscopic scale via Ga and As implants. The influence of the latter is greatest at low doses whilst the former dominates at high doses.
Lateral Diffusion and Capture of Iron in P-Type Silicon
Authors: Beaman Kevin L. , Agarwal Aditya , Koveshnikov Sergei V. , Rozgonyi George A. 
Published: April 2011

AbstractThe lateral motion of iron impurities was observed and studied in ptype iron contaminated silicon. The lateral diffusion was induced by and then measured using Schottky diodes with a special interdigitated fingers design. Capture of the impurities was done by diffusing to laterally placed dislocation loops formed by a self aligned ion implantation. Lateral changes in Fe concentration were determined using capacitance-voltage and deep level transient spectroscopy.
Phosphorus and Aluminum Gettering of Gold in Silicon: Simulation and Optimization Considerations
Authors: Gafiteanu R. , Gösele U. , Tan T. Y. 
Published: April 2011

AbstractUsing the diffusion-segregation equation, modeling and simulations of gettering Au (a substi-tutional-interstitial species in Si) away from the Si bulk have been performed. Three external gettering schemes have been considered: wafer frontside P indiffusion gettering, wafer backside Al deposition gettering, and a combination of the two processes. Under the same processing conditions, it has been shown that P indiffusion gettering is faster than Al gettering, but P gettering has a lower gettering capacity and is less stable than Al gettering for longer gettering times. The combined P and Al gettering process is as fast as P gettering in reaching an optimum gettered state, and possesses the capacity and stability of the Al gettering process.
Gettering of Interstitial Iron in P/P+ Epitaxial Silicon Wafers
Authors: Wijaranakula W. , Gao X. , Curtis K. , Haddad H. 
Published: April 2011

AbstractGettering of interstitial iron in p/p+ epitaxial silicon wafers during an integrated circuit device simulation annealing was examined. The results from the deep level transient spectroscopy and optical microscope examination suggest no correlation between the interstitial iron concentration in the epitaxial layer and the bulk microdefect density. An electron microscopic analysis revealed that gettering of interstitial iron took place at an oxide polyhedral precipitate located at the center of a bulk stacking fault. By comparing the results of iron implanted to non-implanted samples, it is concluded that iron gettering occurs via a phase transformation of Si02 to an α FeSi2 iron disilicide. In this study, it is suggested that gettering of iron atoms is fundamentally different from that of other transition metals where the silicide formation occurs predominantly along the Frank partial dislocations of the bulk stacking fault.
Mechanism of Iron Gettering by Polycrystalline Silicon Film in P-Type Czochralski (CZ) Silicon
Authors: Mishra Kamal K. 
Published: April 2011

AbstractIron gettering in p-type CZ silicon at 600C has been investigated using deep level transient spectroscopy(DLTS), and the surface photovoltage(SPV) method. A quantitative analysis of the gettering kinetics of iron using the polycrystalline silicon film is presented for the first time. Depth profiles of iron concentration indicated a sharp gradient in the Fe concentration near the polycrystalline silicon/substrate interface. Concurrent decrease in the minority carrier diffusion length was also observed in the same region. The majority of iron gettering from the bulk silicon was found to be associated with the enhancement of the internal gettering.The presence of small oxygen precipitates/nuclei generated by prolonged heat treatment at 600C was found to prevent regeneration of FeB pairs at the room temperature. On the other hand, large precipitates formed at lOOOC do not influence the diffusion or the recombination of Fei with B to form FeB pairs.
Hydrogen-Related Electron Traps in GaAs and their Relation to Crystal Stoichiometry
Authors: Shinagawa Tatsuyuki , Okumura Tsugunori 
Published: April 2011

ABSTRACTDeep-level formation upon plasma hydrogenation has been studied with n-GaAs grown by various methods. Four electron traps (EH0-EH3) were generated in As-rich n-GaAs crystals. No electron traps were observed in the LPE layer before and after hydrogenation. The hydrogen as well as excess arsenic defects are responsible for the formation of these deep levels. Two of the generated levels in our study, EH0/EH2, exhibit metastability and are identical to the M3/M4 levels reported by Buchwald et al. It can be speculated that both diffused hydrogen and already existing As antisite defects are responsible for the generation of the metastable defects.