bluuebunny/crossref_metadata_2025_split huggingface dataset:
Super Sims for Ultrasensitive Impurity Analysis
Authors: Anthony J. M. , Donahue D. J. , Jull A. J. T. 
Published: March 2011

AbstractThe technique of accelerator mass spectrometry has been used extensively in recent years as a method for detecting low levels (< 1 part per trillion atomic) of radioactive isotopes in solid materials. The technique consists of a Secondary Ion Mass Spectrometer (SIMS) system in which the conventional mass spectrometer has been replaced by a particle accelerator. We have applied this method to the study of stable elements, primarily semiconductor dopants, using the Univ. of Arizona tandem accelerator mass spectrometer. The use of tandem accelerators allows molecular interferences to be removed due to dissociation of the molecules. Particle energies of several MeV are produced, and energy spectroscopy removes the background due to scattered particles, detector noise, etc. to provide positive particle identification. The current detection limits (-10 parts per billion atomic) are primarily due to ion source contamination and their origin is discussed. Removal of this contamination will allow parts per trillion level detection of stable elements.
Optical Current DLTS with a Bipolar Rectangular Weighting Function for High-Resistivity Neutron Transmutation Doped Silicon
Authors: Tokuda Yutaka , Usami Akira 
Published: March 2011

AbstractDefects in high-resistivity neutron transmutation doped (NTD) silicon without annealing were characterized by optical current DLTS with a bipolar rectangular weighting function using a GaAs LED. The DLTS method with a bipolar rectangular weighting function was also described. Two clear peaks labeled A and B were observed in addition to unresolved peaks due to overlaps of DLTS signals of several defects. The thermal emission activation energies of defects A and B were 0.15 and 0.50 eV, respectively. The DLTS signals of these defects were broader than the calculated ones. This indicates the clustered nature of defects produced by fast neutron irradiation. However, the fact that the characteristic peaks were observed suggests that the material state of high-resistivity NTD silicon is crystalline but not amorphous.
Materials Analysis with X-Ray Rocking Curves
Authors: Paine Bruce M. 
Published: March 2011

AbstractWe review the technique of x-ray double crystal diffractometry as applied to measurement of microscopic profiles of strain in semiconductor materials. The first step in this technique is the extraction of average strains and layer thicknesses directly from the x-ray rocking curves. Profiles of strains with depth are then found by iterative fitting of the experimental rocking curves with trial distributions, incorporated into a theoretical model for the diffraction. The kinematic approximation is accurate for thicknesses up to 1μm in most semiconductors. For greater thicknesses, the more precise dynamical model must be applied.
Studies of Defects and Limits of Solid Solubility in SPE Grown in and Sb Implanted Silicon
Authors: Narayan J. , Holland O. W. 
Published: March 2011

ABSTRACTTransmission electron microscopy (plan-view as well as cross-section) and high-resolution Rutherford backscattering and channeling techniques have been combined to investigate residual defects and substitutional concentrations of In and Sb in <100> and <111> orientations of ion implanted silicon layers after solid-phase-epitaxial (SPE) growth at 475–600°C. The maximum concentrations of Sb and In in substitutional sites were found to be, respectively, 1.3 × 1021 and 5.0 × 1019 cm−3 , exceeding the respective retrograde maxima by factors of 18 and 60. These results provide direct evidence of solute trapping and metastable alloying under solid-phase growth conditions. Accumulation of solute at the crystalline-amorphous interface was observed only for indium above a certain interfacial concentration. At still higher interfacial concentrations, the planar interface was observed to become unstable and SPE growth was retarded.
Structure and Properties Changes During Ion Bombardment of Crystalline Fe75B25
Authors: Berkowitz A.E. , Johnston W.G. , Mogro-Campero A. , Walter J.L. , Bakhru H. 
Published: March 2011

ABSTRACTRibbons of Fe75B25, prepared by quenching from the melt, were mostly amorpbous. After annealing at 773 K, the ribbons were entirely crystalline, with the phases Fe3B, Fe2B and α - Fe. Annealed ribbons were bombarded at RT with 4 MeV argon ions, at a damage rate of 7 × 10−4 dpa sec−1 near the surface. The Fe3B was completely converted to an amorphous form at 0.15 dpa, the lowest damage level at which amorphization of a metal alloy has been reported. The Fe2B disappeared by about 1.5 dpa. The α -Fe disappeared between 17 and 50 dpa, apparently by ion beam mixing rather than direct amorphization. Amorphous films also were prepared by sputtering at low power level, and crystallized at 773 K, which also caused sintering. Bombardment with argon ions produced major changes in resistivity and magnetic coercive force at the same low damage levels that caused amorphization of Fe3B Hc of the bombarded film was the same as in an as-quencheo amorpous ribbon. The relatively high resistivity of as sputtered amorphous film was apparently due to the porosity in the columnar cell walls. With present technology, it should be possible to produce amorphous films or structures of Fe3B at rates approaching 50 m2 hr−1.
Mossbauer Spectroscopy Study of the Amorphization of Tellurium by Ion Implantation
Authors: Langouche G. , Dezsi I. , Van Rossum M. , De Potter M. , De Bruyn J. , Schroyen D. , Coussement R. 
Published: March 2011

ABSTRACT125Te was implanted into Te single crystals, held at different temperatures, and studied by Mössbauer Spectroscopy. It is shown that amorphization of the target occurs during implantation at liquid nitrogen temperature. The role of the target temperature in the Naguib and Kelly criterion for amorphization is discussed.
Transmission Electron Microscopy and Resistivity Measurements on Pd1−x Six Alloys Prepared by Ion Implantation.
Authors: Traverse A. , Ruault M.O. , Mendoza-Zelis L. , Schack M. , Bernas H. , Chaumont J. , Dumoulin L. 
Published: March 2011

ABSTRACTAfter 6K implantation of Si in Pd films, resistivity measurements (previously reported (1)) had provided preliminary evidence that an amorphous state had been reached for a composition Pd.80 SiO 20· This result has been recently confirmed by transmission electron microscopy (TEM) observations : diffuse diffraction rings appear in the implanted part of the Pd film. New experiments are reported : - resistivity dose dependence (and temperature dependence) of a 300K Si implanted Pd film ; - in situ TEM experiments to follow the amorphization process during implantation.
Ion Mixing and Demixing in The Au-Si System
Authors: Liu Bai-Xin , Wieluński Leszek S. , Nicolet Marc-A. , Lau S. S. 
Published: March 2011

ABSTRACTAfter a relatively low dose Xe+ irradiation (∼ 2 × 1015 Xe/cm2), an initially discrete multilayered film of average composition Au7Si3 transforms to a uniform layer and forms a metastable phase. This is the well known ion mixing process. The same samples were subjected to higher dose irradiation (> 4 × 1015 Xe/cm2). It was found that the Si migrates to the sample surface and forms a nonuniform depth profile in BS spectra. At the same time, the metastable phase dissociates into Au and Si phases. As this process is opposite to that of ion mixing, we suggest to name this process ion demixing. These observations demonstrate that ion mixing and ion demixing can both occur in the same system, if it is properly chosen. Possible mechanism responsible for these processes are discussed.
Ion Beam Mixing of Ceramic Alloys - Preparation Andmechanical Properties
Authors: Lewis M. B. , McHargue C. J. 
Published: March 2011

ABSTRACTTechniques used to produce unique states of pure metals mixed into ceramic materials are presented. The samples were prepared by irradiating a 1-MeV Fe+ beam on A12O3 crystal surfaces over which a thin chromium or zirconium film had been evaporated. The limitations of using noble gas ion beams are noted. Micro Knoop hardness tests performed near the surfaces of the samples indicated a significant increase in the hardness of most samples prepared by ion beam mixing.
The Dangling Bond in Undoped Amorphous Hydrogenated Silicon: Trap or Recombination Center?
Authors: Parker M. A. , Conrad K. A. , Schiff E. A. 
Published: March 2011

ABSTRACTThe role of the neutral dangling bond defect upon photocarrier processes in undoped amorphous hydrogenated silicon (a-Si:H) is discussed. The evidence that the dangling bond is a simple recombination center is reviewed, and it is shown that this model does not account for photocurrent response time measurements. Experimental data pertinent to the role of electrical contacts upon response time measurements are presented, and it is concluded that contact effects do not account for response-time measurements. The possibility that the dangling bond is primarily an electron trap is discussed.
Analytical Determination of Generation-Recombination Rate In Amorphous Silicon
Authors: Furlan Jože , Amon Slavko 
Published: March 2011

ABSTRACTA general expression for generation-recombination rate in a-Si based on classical SRH theory including different electron and hole capture cross-sections for donor-like and acceptor-like centers inside the mobility gap is derived. Applying appropriate approximations and two-exponential model for localized states distribution two methods of analytical solution are presented and discussed.
Increased Conductivity in P-Type Hydrogenated Amorphous Silicon
Authors: Pankove Jacques I. , Dresner Joseph 
Published: March 2011

ABSTRACTThe low conductivity of B-doped a-Si:H is usually attributed to the fact that only a small fraction of the boron is tetrahedrally coordinated. In the presence of hydrogen, that small fraction can be inactivated via the acceptor-neutralization process that was described for the case of B-doped crystalline Si. When a B-doped sample of a-Si:H was annealed to drive away hydrogen near the boron atoms, the conductivity increases by a factor of 600.
Although a-Si:H can be doped either n-type or p-type, the doping efficiency is orders of magnitude poorer than in crystalline Si. In fact the doping efficiency of boron is one order of magnitude lower than that of phosphorus. Several models account for the low doping efficiency of a-Si:H, the most plausible being the location of B in a trigonal site, i.e. surrounded by three Si-atoms as shown in Fig. 1. Such a center is neutral and cannot act as an acceptor.
The present work is an offshoot of our study of the hydrogenation of dangling bonds in crystalline Si (1). The awareness that H ties to a Si dangling bond more strongly than another Si-atom led us to passivate the numerous dangling bonds on the surface a Si-crystal. Then, we passivated dangling bonds in grain boundaries and in dislocations and we showed that ion implantation damage also could be neutralized by atomic hydrogen thus removing non-radiative recombination centers and allowing the luminescent transitions to become more efficient.
Capacitance Studies of Metastable Defect Creation in Hydrogenated Amorphous Silicon
Authors: Cohen J. D. , Mahavadi K. , Zellama K. , Harbison J. P. , Delahoy A. E. 
Published: March 2011

ABSTRACTWe have studied the light induced instability problem in hydrogenated amorphous silicon using junction capacitance techniques. These techniques are used to examine specific changes in the density of gap states, and occupation of gap states, for undoped a-Si:H samples after light saturation and for a series of partial anneal “states” which culminate in the original dark annealed state (state A). We find that the observed changes in the metastable occupied and unoccupied defects contradict the Si-Si bond breaking model and indicate at least two defect creation processes. In several samples we also find clear evidence that the metastable defect distribution near midgap has a slightly different energy distribution than the stable deep state (dangling bond) distribution. At the same time, these results seem to be qualitatively consistent with many aspects of recent ESR and optical absorption studies of metastable defect creation. We discuss these findings in terms of alternative possible microscopic models for metastable effects in a-Si:H.
Time Dependence of the Metastable, Optically-Induced Esr in a-Si:H
Authors: Lee C. , Ohlsen W. D. , Taylor P. C. 
Published: March 2011

ABSTRACTThe occurrence of optically-induced, metastable changes in the paramagnetism in films of a-Si:H is well known. The effect was first observed with white light in powdered samples, but recent experiments with both white and monochromatic light incident on films on substrates have observed a similar effect. This optically-induced ESR appears to be stable at temperatures < 400 K. Typical inducing curves for samples with initial dark spin densities ns > 1016 spins/cm3 approach a power law behavior (ns ∼ t1 / 3) at long times. However, when the dark spin density is less than 1016 spins/cm3, the samples exhibit an inducing curve (on a log-log scale) with a continuously decreasing slope. The curve does not exhibit a unique power law behavior over an extended range of time and is at all times < t1 / 3.
Microcrystallinity in α-Si, Ge:H, F Alloys
Authors: Shen D. S. , Kolodzey J. , Slobodin D. , Conde J. P. , Lane C. , Campbell I. H. , Fauchet P. M. , Wagner S. 
Published: March 2011

ABSTRACTMicrocrystalline inclusions in hydrogenated and fluorinated amorphous silicongermanium alloys, α-Si, Ge:H, F, were studied. Microcrystals grown during RF or DC glow discharge deposition from SiF4, GeF4 and H2 consist of either pure Si or Ge. Microcrystals produced by thermal annealing of initially amorphous alloys are either microcrystalline Ge or microcrystalline Si-Ge alloys depending on the annealing temperature. Values for the grain size were calculated from X-ray diffraction (XRD) and Raman spectra. The grain size of the “grown” microcrystal ranges from 8 to 60 nm. These grown grains exhibit preferential orientation of the (220) planes parallel to the substrate surface. Microcrystals produced by high-temperature anneal are randomly oriented. Scanning electron micrographs of as-grown samples show protruding platelets several 100 nm long and several 10 nm wide. Fractured cross sections exhibit columnar structure.
Deuteron Magnetic Resonance in a-Si and a-SiGe Produced from Fluorides
Authors: Bork V. P. , Fedders P. A. , Norberg R. E. , Leopold D. J. , Mackenzie K. D. , Paul W. 
Published: March 2011

ABSTRACTDeuteron magnetic resonance line shapes and spin lattice relaxation times are presented for a-Si:D, F and a-SiGe:D, F. These parameters differ from those for typical a-Si:D, H samples, but in some respects are similar to those for an annealed a-Si:D, H sample. The a-SiGe:D, F spectra display an unusually large broad central weakly bound D resonance component and a barely-resolved Ge-D quadrupolar doublet. Comparisons indicate substantial differences in void morphology between the a-Si:D, F and a-SiGe:D, F.
Characterization of a-Si:H Near a-Sinx:H/a-Si:H Interface by Photoluminescence Spectra
Authors: Yoshimura Tetsuzo , Hiranaka Kouichi , Yamaguchi Tadahisa , Yanagisawa Shintaro , Asama Kunihiko 
Published: March 2011

ABSTRACTThe influence of the a-SiNx:H composition on the near-interface properties of the a-SiNx:H/a-Si:H layered structure was studied by photoluminescence measurements and the results were compared with a-Si TFT characteristics. It was found that the cw photoluminescence spectra of a-Si:H near the interface tend to shift to the low-energy side with an increase in nitrogen content of the a-SiNx:H layer. Time-resolved photoluminescence measurement revealed that the low-energy shift of the cw photoluminescence band is attributed to an enhancement of an additional broad band, which is caused by deep states, appearing in the low-energy side of the band arising from the transition between band tail electrons and holes. A decrease in field effect mobility in TFTs with an a-SiNx:H gate-insulator was observed when the nitrogen content of the a-SiNx:H increases, and correlated well with the low-energy shift of the cw photoluminescence band. These results suggest that the deep states in a-Si:H near the interface tend to increase with the nitrogen content of the a-SiNx:H. The origin of the states is believed to be a lattice strain induced in the a-Si:H layer.
Origin of Persistent Photoconductivity in Modulation Doped Amorphous Silicon Multilayers
Authors: Agarwal S. C. , Guha S. 
Published: March 2011

ABSTRACTWe show that persistent photoconductivity (PPC) observed in npn … multilayers of hydrogenated amorphous silicon (a-Si:H) and compensated thin a-Si:H films have a common origin. It is caused by special centers lying in the upper half of the mobility gap. The centers are not related to the presence of argon during deposition. Similarities of PPC between the layered and compensated films are shown. We also find that PPC in compensated samples, is not entirely a surface effect. Experiments are suggested to decide whether these centers are P-B complexes or can arise from the presence of boron alone.
a-Si Basis Heterojunction Stacked Solar Cells
Authors: Hamakawa Y. , Matsumoto Y. , Zhang-Yang Xu , Okuyama M. , Takakura H. , Okamoto H. 
Published: March 2011

ABSTRACTA systematic study has been made on a-Si basis heterojunction tandem structure solar cells. Design rule and optimizations of cell parameters on two and three stacked heterojunction solar cells are discussed on various material bottom junctions stacked with a-Si. A series of experimental trials has been made on some candidate materials. Technical data on cell fabrication processes, device performance are presented. In the -present stage of experiments, 13.3% efficiency on a-Si/poly-Si two terminals tandem solar cell and also on a-Si//poly- CdS/CdTe four terminals cell have been obtained. Some key technologies for future low cost massproduction processes such as growth of polycrystalline thin film for bottom cell are also discussed.
Asymmetries in Amorphous Silicon Devices
Authors: Smith Z E. , Wagner S. 
Published: March 2011

ABSTRACTThe consequences of the asymmetries in the density of electronic states of hydrogenated amorphous silicon on the behavior of electronic devices are discussed. Asymmetries in the relative widths of valence and conduction bandtails, the position of the dangling-bond states within the gap, and the occupation statistics of non-correlated defects are shown to affect the performance of p-i-n solar cells, and explain their superior performance and stability when compared with such devices illuminated through the n-layer (n-i-p). The device-modeling concepts which emerge help explain the differences between cell degradation via light exposure under various bias conditions, and cell degradation by dark forward bias.
Wavelength Dependence of the Turn-Off Character in a-Si:H Solar Cells
Authors: Oqinghai Mia , Guang Gao , Baocheng Cao , Guocai Dai 
Published: March 2011

ABSTRACTThe turn-off character in a-Si:H solar cells has been studied by rectangular monochromatic light pulses. It is found that the turn-off time increases obviously with the decrease of the excitation light wavelengths when the turn-off steady photovoltages are the same. This phenomenon can be explained by the wavelength dependence of the photocapacitance and the time constant products RC in the a-Si:H solar cells.
Amorphous Silicon Alloy Technology For Active Matrix Displays
Authors: Yaniv Z. , Cannella V. , Baron Y. , Lien A. , McGill J. 
Published: March 2011

ABSTRACTThin film semiconductor devices have been investigated over the past twenty years for application in large area flat panel displays. The development of thin film transistors and diodes based on amorphous silicon (a-Si) alloy materials has made the application of these devices, to display technologies, very attractive. More recently, manufacturing techniques to produce high quality large area films of amorphous silicon alloys have been demonstrated for photovoltaic applications.Most of the current research and development effort on active matrix liquid crystal displays (LCDs) has concentrated on a-Si alloy TFTs. The success of TFT based displays for large area flat panel displays has been limited so far, mainly due to the difficulty of obtaining a high quality gate dielectric by plasma deposition and due to the presence of crossing conductors on the same substrate, both increasing the probability of defects in the display. When a two terminal sandwich device is used, on the other hand, no gate dielectric is required, hence, a higher yield can be expected. Metal-insulator-metal and hydrogenated amorphous silicon alloy devices have been proposed for incorporation in LCDs. Performance requirements for a useful active matrix switching element and a comparison among the different a-Si alloy thin film devices used for this purpose will be reviewed.
Tellurium Alloys for Reversible Optical Data Storage
Authors: Young R. T. , Strand D. , Gonzalez-Hernandez J. , Ovshinsky S. R. 
Published: March 2011

ABSTRACTTellurium-based chalcogenide alloys, which are used for electronic switch materials, also have the appropriate optical and thermal properties for reversible optical data recording. One of the major concerns encountered with this type of phase change material is that there can be two contradictory characteristics of the material, i.e., the amorphous phase thermal stability and the crystallization rate are involved. We have demonstrated, in this paper, that this problem can be solved. We report that certain transition metal elements added to Te alloy films can substantially improve the rate of crystallization without any reduction of the amorphous phase stability.
The Optical Properties and Stability of GE and Sn-Doped TEOx Films
Authors: Lee W -Y , Davis C. R. , Lim G. , Coufal H. , Sequeda F. 
Published: March 2011

ABSTRACTThe optical properties and the thermal stability of Ge and Sn doped TeOx films prepared by coevaporating TeO2, Te, Ge and Sn are reported. These films are amorphous as-deposited and crystalline Te appears after annealing at, e.g., 100 to 250°C. As expected, the addition of Ge and Sn increases the absorption of the TeOx films at the wavelength of interest (e.g., 830 nm). However, the thermal stability of (TeO1.1)1-xGex (x=0 to ~0.7) films is found to decrease with increasing x initially, starting to increase with increasing x only after x reaches a value between 0.3 and 0.4. These results differ from those reported previously for Ge and Sn-doped TeOx films and from those observed for Te-Ge alloy films. Interpretations of these results based on a solid state reaction between TeO2 and Ge or Sn during deposition are presented and discussed.
Tem Characterization of Solid-Phase Epitaxy in Amorphized Polysilicon
Authors: Chang P.-H. , Sundaresan R. 
Published: March 2011

ABSTRACTSolid Phase Epitaxy (SPE) of amorphous silicon thin films can be employed to build novel device structures for VLSI applications. One way of achieving SPE is to use a room temperature silicon implant to amorphize a polysilicon layer followed by a thermal treatment to promote epitaxial growth. Both vertical SPE, in which the epitaxial film is grown directly on silicon substrate, and lateral SPE, in which the epitaxial growth is extended over a thin layer of oxide using the vertical SPE region as a seed, have been realized using this approach. This paper presents results obtained by cross-sectional TEM analysis of the epitaxial films, with particular emphasis on the effects of implant schedule and annealing conditions on the epitaxial regrowth.