bluuebunny/crossref_metadata_2025_split huggingface dataset:
Radiation-Induced Segregation: A Microchemical Gauge to Quantify Fundamental Defect Parameters
Authors: Simonen E. P. , Bruemmer S. M. 
Published: April 2011

AbstractDefect kinetic parameters for radiation-induced grain boundary segregation in austenitic stainless alloys are evaluated by comparing model predictions to measured responses. Heavy-ions, neutrons, and proton irradiations having substantial statistical bases are examined. The combined modeling and measurement approach is useful for quantifying fundamental defect parameters. The mechanism evaluation indicates that vacancy migration energies were 1.15 eV or less and the vacancy formation energy at grain boundaries was 1.5 eV. Damage efficiencies of heavy ions and light-water reactor neutrons were about 0.03. Inferred proton damage efficiencies were about 0.15. Segregation measured in an advanced gas-cooled reactor component was much greater than predicted from those parameters alone.
Optimization of Reverse Saturable Absorber Limiters: Material Requirements and Design Considerations
Authors: Hagan D. J. , Xia T. , Dogariu A. , Said A. A. , Van Stryland E. W. 
Published: April 2011

AbstractWe present numerical beam-propagation simulations of optimized reverse-saturable absorption (RSA) based optical limiters where the depth of focus of the input beam is much smaller than the thickness of the nonlinear material. The optimization is achieved by allowing the molecular concentration to vary along the propagation path, allowing the entire length of the limiter to reach the maximum possible nonlinear absorption before eventual damage to the limiter. We review in detail the analytic model originally derived by Miles [1] to determine the design and performance of such limiters. This model requires the usual 5-level model used in the numerical solution to be approximated by a quasi-three-level system. We show that this effective 3-level excited-state cross section is both pulsewidth and fluence dependent. The numerical propagation output shows that there is considerable diffractive beam distortion, which cannot be accounted for in the analytic model. The end result is that while there is qualitative agreement with numerical results, the magnitude of the limited output can be an order-of-magnitude underestimated. We determine that the fluence level at all parts of the limiter must be at least ten times the saturation fluence to efficiently utilize the nonlinear absorption. We further describe how the optimized distribution of molecular density is the limit of the multi-element tandem limiter for an infinite number of elements. By carefully accounting for saturation over the entire length of each individual element, we show how a multi-element limiter may be designed to closely approach the performance of the optimized distribution for as few as four elements. With current materials technology the damage threshold of solid hosts needed to vary the molecular density is much lower than that of glass cuvettes used for liquid based limiters. Therefore, a multi-element liquid based tandem limiter can be used in full saturation so that better limiter performance should be obtained. Ultimately, however, the operation of all RSA-based limiters involves a strict trade-off between performance and linear transmittance.
Broadband Excited State Dynamics of Common Reverse Saturable Absorbing Dye Media.
Authors: McEwan Kenneth J. , Hollins Richard C. 
Published: April 2011

AbstractIn this paper we describe a technique by which the broadband excited state absorption/emission and dynamics can be measured for materials with either linear or two photon absorption. The technique is applied to two different dyes in solution and to a cyano-biphenyl organic liquid. The ratio of σex/σgr for HITCI in methanol is greater than 1 from 400 to 570nm and at 532nn is determined to be 25; the excited state lifetime is 800ps. For CAP in methanol σex/σgr is greater than 1 from 400–650nm and is 14 at 532nm. Dimer absorption and emission are found to contribute to the excited state response in this material. In the organic liquid broadband (400–570nm) excited state absorption is measured following two photon excitation at 588nm.
Plasma Deposition and Characterization of Stable a-Si:H (Cl) From a Silane-Dichlorosilane Mixture
Authors: Osborne I. S. , Hata N. , Matsuda A. 
Published: April 2011

ABSTRACTHydrogenated amorphous silicon containing chlorine (a-Si:H (Cl)) films have been grown by plasma enhanced chemical vapor deposition from a mixture of silane and dichlorosilane with a dichlorosilane concentration up to 60%. We report on the film properties in the as-deposited state and the behavior of the films under both high intensity pulsed laser illumination and long-term AMI illumination. With increasing dichlorosilane concentration the films show an increased resilience to the creation of light induced defects, as determined from the constant photocurrent method. After 900 hours under AMI illumination, the defect density shows a minimum (< 1016 cnr−3) for a 10 % mixing ratio.
Characterization of Compositional Gradients in Amorphous Semiconductor thin Films By Real Time Spectroscopic Ellipsometry
Authors: Kim Sangbo , Lu Yiwei , Collins R. W. 
Published: April 2011

ABSTRACTA new approach has been developed for the analysis of real time spectroscopie ellipsometry (RTSE) data that has important applications in characterizing compositionally-graded layers in amorphous semiconductor devices. The new RTSE data analysis approach determines (i) the instantaneous deposition rate, (ii) the surface roughness layer thickness, and (iii) the dielectric function of the near-surface layer (top 20 Å) of the growing film, all without any knowledge of the deposition history. We tested this new approach by characterizing a-Si1-xCx:H (x ∼ 0.09) alloy films with continuously graded void volume fractions. The results reported here are unique in that they represent the first successful optical analysis of amorphous semiconductor structures having continuously varying properties with depth into the film.
The Influence of Frequency and Pressure on the Material Quality of PECVD A-SI:H
Authors: Van Sark W.G.J.H.M. , Bezemer J. , Heller E. M. B. , Kars M. , Van Der Weg W. F. 
Published: April 2011

ABSTRACTA systematic study of material quality has been performed for a-Si:H layers deposited by plasma enhanced chemical vapour deposition at frequencies between 30–80 MHz. The effect of frequency variation was studied in combination with the variation of pressure and power density. The process conditions were optimised not only for ‘device quality’ opto-electronic properties but also for a uniformity in layer thickness better than 5 %. For every frequency an optimum pressure exists for which the properties of the deposited layer satisfy the ‘device quality’ requirements. A clear correlation is observed between the transition from the so-called α- to the γ-regime of the plasma and the dependence of the deposition rate γd with pressure pand frequency ƒ: γ d ∝ pƒ2/3.
Equilibration in Amorphous Silicon Nitride Alloys
Authors: Dunnett Bruce , Cooper Christopher H. , Murley Darren T. , Gibson Roderick A. G. , Jones David I. , Powell Martin J. , Deane Steven C. , French Ian D. 
Published: April 2011

ABSTRACTSeveral series of amorphous silicon nitride thin films have been grown by plasma-enhanced chemical vapour deposition, where the ratio of ammonia and silane feed gases was held constant for each series while the deposition temperature was varied from 160 °C to 550 °C, and all other deposition conditions were held constant. Photothermal Deflection Spectroscopy measurements were used to determine the Urbach slope E0 and the defect density ND. It is found that ND is determined by E0 for most of these samples, suggesting that defect equilibration occurs in a-SiNx:H for x up to at least 0.6. The growth temperature at which the disorder is minimised increases to higher values with increasing x, which is explained in terms of a hydrogen-mediated bond equilibration reaction. Fourier Transform Infra Red spectroscopy measurements were performed to determine the changes in hydrogen bonding with growth temperature. The results suggest that a second bond equilibration reaction also occurs at the growing surface, but that equilibrium cannot be reached at higher temperatures because of hydrogen evolution from Si-H bonds.
Defects and Microstructure in Optimized a-Si:Ge:H - New Results from Electron Spin Resonance Experiments
Authors: Malten C. , Finger F. , Fölsch J. , Kulessa T. , Wagner H. , Ray S. , Middya A. R. , Hazra S. 
Published: April 2011

ABSTRACTAmorphous silicon germanium alloys with improved properties for photovoltaic applications are investigated by electron spin resonance. Spin densities in this material are strongly reduced with optimized deposition conditions. Still the Ge dangling bond remains the dominating deep defect and the ratio of Ge over Si dangling bond defects is not much changed. The spin resonance spectra of these samples show distinctive differences from conventional material. The superposition signal can not be deconvoluted into modified Si- and Ge- dangling bond resonances as done previously. Instead a lineshape asymmetry or additional resonances are needed to deconvolute the spectra. The development of g-values with alloy composition indicate a more homogeneous chemical ordering in optimized material in agreement with other experimental data.
Band Discontinuity Effect on a-Si:H and a-SiGe:H Solar Cells
Authors: Xu X. , Banerjee A. , Yang J. , Guha S. , Vasanth K. , Wagner S. 
Published: April 2011

ABSTRACTThe electrical bandgap of microcrystalline silicon (μc-Si:H) p type layers used in a-Si:H alloy solar cells and the band edge discontinuities between μc-Si:H and a-Si:H alloys have been determined by internal photoemission measurements. The bandgap of μc-Si:H is found to be in the range of 1.50 to 1.57 eV, and the discontinuities at the conduction and the valence band edges are 0 to 0.07 and 0.26 to 0.35 eV, respectively. Use of these parameters in the numerical simulation of single-junction a-Si:H and a-SiGe:H alloy solar cells is found to predict experimental results of solar cell performance.
A Semi-Insulating Layer for Novel High Voltage Polysilicon Thin Film Transistors
Authors: Clough F. J. , Chen Y. , Brown A. O. , Sankara Narayanan E. M. , Milne W. I. 
Published: April 2011

ABSTRACTThis work describes the deposition and characterisation of semi-insulating oxygen-doped silicon films for the development of high voltage polycrystalline silicon (poly-Si) circuitry on glass. The performance of a novel poly-Si High Voltage Thin Film Transistor (HVTFT) structure, incorporating a layer of semi-insulating material, has been investigated using a two dimensional device simulator. The semi-insulating layer increases the operating voltage of the HVTFT structure by linearising the potential distribution in the device offset region.A glass compatible semi-insulating layer, suitable for HVTFT applications, has been deposited by the Plasma Enhanced Chemical Vapour Deposition (PECVD) technique from silane (SiH4), nitrous oxide (N2O) and helium (He) gas mixtures. The as-deposited films are furnace annealed at 600°C which is the maximum process temperature. By varying the N2O/SiH4 ratio the conductivity of the annealed films can be accurately controlled up to a maximum of around 10−7 Ω−1.cm−1 Helium dilution of the reactant gases improves both film uniformity and reproducibility. Raman analysis shows the as-deposited and annealed films to be completely amorphous. A model for the microstructure of these Semi-Insulating Amorphous Oxygen-Doped Silicon (SIAOS) films is proposed to explain the observed physical and electrical properties.
Realization of an Amorphous N-I-P-I-N Three Color Sensor
Authors: Eberhardt K. , Neidlinger T. , Schubert M. 
Published: April 2011

ABSTRACTUtilizing the high optical absorption of amorphous silicon in conjunction with advanced signal processing capabilities of modern ASICs offers the possibility of simply realizing smart color sensors with random pixel access and without any losses in active area due to the signal processing circuitry. Thin-film photodiodes have to be incorporated into a layer sequence of ASIC/insulator/metal/a-Si:H based multilayer/TCO for this so-called Thin Film on ASIC (TFA) concept[l]. Amorphous silicon and silicon carbide photodiodes have been studied, and discrimination of the fundamental colors (red, green and blue) has been obtained from 2-terminal n-i-p-i-n devices at small bias voltages within ±2 V. Changing of the bias voltage applied to the two back-to-back p-i-n junctions allows for adjusting the location of predominant photo-carrier collection, and therefore enables color readout according to the energy dependent absorption profile of the incident light. Film thickness and optical bandgap of the individual layers have been optimized to achieve optimum color sensitivity. Switching experiments in the voltage mode give some information about conceivable frame rates these TFA sensors could be operated at. Light-induced degradation does not hamper the performance of the sensors thanks to low light intensity, reverse bias conditions, and small i-layer thickness.
Hydrogenated Amorphous Silicon Speed Sensor Based on the Flying Spot Technique
Authors: Vieira M. , Fantoni A. , Maçarico A. , Soares F. , Evans G. , Martins R. 
Published: April 2011

ABSTRACTIn the past we have developed a transient technique, called the Flying Spot Technique (FST). FST allows, not only to infer the ambipolar diffusion length but also the effective lifetime of the photogenerated carriers once the light spot velocity and geometry of the structure were known.In this paper, we propose to apply this technique backwards in order to detect the path and velocity of an object that is moving in the direction of a light source. The light reflected back from the object is analyzed through a p.i.n structure being the transient transverse photovoltage dependent on the movement of the object (position and velocity). Assuming that the transport properties of the material and the geometry of the device are known and using a triangulation method we show that it is possible to map the movement of the object. Details concerning material characterization, simulation and device geometry are presented.
Fabrication of a Single Crystal Silicon Substrate for AM-LCD Using Vertical Etching of (110) Silicon
Authors: Yoon Jun-Bo , Lee Ho-Jun , Han Chul-Hi , Kim Choong-Ki 
Published: April 2011

ABSTRACTIn this paper, feasibility of crystalline silicon (c-Si) substrate for transmissive active matrix liquid crystal displays (AM-LCDs) has been investigated. The transparent pixel areas of AM-LCD were formed by vertical etching of (110) silicon substrate using anisotropie etching property of aqueous KOH. Combining this vertical etching process with the conventional MOSFET fabrication process, the pixel switching devices, peripheral circuits and transparent apertures were successfully integrated on the same c-Si substrate. The pixel NMOS devices exhibit an electron mobility of about 600cm2/V-s, a subthreshold slope of 65mV/decade and ON/OFF current ratio of 9 decades at 5V drain voltage. And the gate delay time is 3.3ns at 10V power voltage, measured from a ring oscillator which has enhancement-load type NMOS inverters having the (W/L) iload- (W/L) driverer of 25μm/15μm - 50μm/10μm.
Efficient Nonradiative Recombination Centers in MBE-Grown Si and SiGe/Si Heterostructures
Authors: Chen W. M. , Buyanova I. A. , Henry A. , Ni W.-X. , Hansson G. V. , Monemar B. 
Published: April 2011

AbstractWe carry out an investigation of grown-in nonradiative defects in Si and SiGe/Si heterostructures grown by molecular-beam-epitaxy (MBE). A number of such defects are observed by the optical detection of magnetic resonance (ODMR) technique, in samples with various structures and growth conditions. These defects are shown to provide efficient nonradiative shunt paths for carrier recombination, competing with and reducing radiative recombination processes. It is revealed that the dominant nonradiative defect is a low-symmetry vacancy-related complex, evident from a characteristic hyperfine structure due to 29Si ligands (with nuclear spin I=1/2 and natural abundance of 4.67 %) connected to the dangling bonds. The introduction of these defects is believed to be largely due to a low surface adatom mobility during the low temperature growth. By varying the substrate bias during the MBE growth, it is shown that the formation of these nonradiative defects can be effectively enhanced by exposure to accelerated positive ions, presumably dominated by the Si+ ions. Effects of hydrogenation on these defects are also studied.
Point Defect Supersaturation During Zinc Diffusion into InP
Authors: Wittorf D. , Jäger W. , Rucki A. , Urban K. , Hettwer H.-G. , Stolwijk N. A. , Mehrer H. 
Published: April 2011

AbstractFormation of defects during Zn diffusion into undoped and Fe-doped InP single crystals at 700°C has been observed by transmission electron microscopy for various diffusion conditions. The observations are correlated with Zn concentration profiles obtained by electron microprobe measurements and secondary-ion mass spectrometry. The results allow the conclusion that indiffusing interstitial Zn can occupy In sublattice sites via a kick-out reaction. Under appropriate diffusion conditions supersaturations of In self-interstitial atoms result leading to defect formation. Observations in Fe-doped InP suggest that Zn also replaces Fe on In sublattice sites leading to redistribution and to precipitation of Fe.
Minority Carrier Diffusion Length Improvement in Czochralski Silicon by Aluminum Gettering
Authors: Joshi Subhash M. , GÖsele Ylrich M. , Tan Teh Y. 
Published: April 2011

AbstractGettering is widely used for fabricating integrated circuits using Si substrates, and has great potential for solar cell fabrications as well. Recently available solar cell efficiency studies have shown the benefits of the wafer backside Al, attributable to effects of gettering, a wafer backside field, and passivation of grain boundaries and dislocations. In this paper, we report experimental results which showed unambiguously that Czochralski Si wafer bulk minority carrier diffusion lengths can be significantly improved due to gettering of impurities by wafer backside Al, which also provided a protection from environmental contamination.
Characterization of the Damage on the Back Side of Silicon Wafers
Authors: Lindo S. E. , Matney K. M. , Goorsky M. S. 
Published: April 2011

AbstractGettering represents a standard procedure to remove harmful impurities from device active regions of a silicon wafer. An affordable technique for the creation of a defect free (denuded) zone is the introduction of gettering sites on the wafer back side via mechanical damage (i.e. lapping). However, optimizing the extrinsic gettering process requires a technique to quantify the extent of damage introduced through a typical back-side damaging step. Here, we present results from a study using triple axis x-ray diffraction. We characterized the level of damage present in wafers subjected to different lapping conditions. By comparing reciprocal space maps from samples that had undergone different lapping steps, we concluded that all the as-lapped samples showed similar levels of damage in terms of both strain variations and lattice tilts. However, the integrated diffuse scattering intensities decreased from medium to soft t.-double-soft lapping, which confirmed that the double soft lapping introduced the least damage. Typically, the damage step introduced a symmetrical distribution of both lattice strain and lattice tilts (mosaicity) in the surface layer. KOH etching was employed to determine the depth of the damaged layer. In all cases the as-lapped samples had integrated intensities two orders of magnitude greater than those of the etched samples. Analysis of the residual damage present in the lapped samples after chemical etching confirmed that the more aggressive lapping conditions introduced damage of greater depth.
Spectroscopy of Transition-Metal-Hydrogen Complexes in Silicon
Authors: Stavola Michael , Uftring S.J. , Evans M.J. , Williams P.M. , Watkins G.D. 
Published: April 2011

AbstractTransition-metal-hydrogen complexes have been introduced into bulk Si samples that contained Pt, Au, or Rh by the indiffusion of hydrogen at 1250°C from H2 gas. The structure and electrical properties of a PtH2 complex in Si have been studied by vibrational spectroscopy and electron paramagnetic resonance (EPR). The PtH2 complex has been found to introduce two levels in the Si bandgap. There is one paramagnetic charge state for which EPR provides detailed structural information and two nonparamagnetic charge states. The hydrogen vibrations of all three charge states of PtH2 have been assigned. In addition to the PtH2 complex, the hydrogen vibrations of several additional complexes in Si samples that contain hydrogen and Pt, Au, or Rh have been identified.
Low-Temperature Diffusivity of Hydrogen in Different Silicon Substrates
Authors: Deng Xiaojun , Sopori Bhushan L. 
Published: April 2011

AbstractThe diffusivity of deuterium (D) at 250°C was determined in silicon samples grown by different techniques. It is found that the diffusivity increases with the growth speed, increase in carbon content and a decrease in oxygen concentration of the substrate. These growth conditions correlate well with the concentration of vacancy-type defects in the as-grown state. Hence, we conclude that a vacancy mechanism is responsible for low-temperature hydrogen diffusion in silicon. The highest diffusivity for hydrogen, calculated from these data, was found to be 3 × 10−7 cm2/s.
Control of Oxygen Content in Heavily Sb-Doped CZ Si Crystal by Adjusting Ambient Pressure
Authors: Izunome Koji , Huang Xinming , Togawa Shiniji , Terashima Kazutaka , Kimura Shigeyuki 
Published: April 2011

AbstractIn Czochralski-grown (CZ) silicon single crystals, antimony (Sb) doping decreases the oxygen concentration by enhancing oxygen evaporation from the melt surface. In this study, Ar ambient pressures of around 100 Torr over the silicon melt were found to suppress evaporation of oxide species. To clarify the effect of the growth chamber ambient pressure on oxygen concentration, heavily Sb-doped CZ silicon crystals were grown under Ar pressures of 30, 60, and 100 Torr. Increasing Ar pressure increases the oxygen and Sb concentrations at the melt surface. The oxygen concentration under an Ar pressure of 100 Torr was 1.2 times higher that under 30 Torr when the solidified fractions are 0.5 or larger. The oxygen evaporation rate is controllable by gas phase transport of Sb2O at high Ar pressures.
Noncontact Photoconductivity Amplitude Technique to Characterize Polishing- and Slicing-Induced Residual Damage in Si Wafers
Authors: Ogita Y. , Nakano M. , Masumura H. 
Published: April 2011

ABSTRACTThe photoconductivity amplitude (PCA) technique with UV laser carrier excitation has been proposed to characterize surface property and subsurface damage. Combining this new technique with mechanochemical polishing has determined the depth profile of the slicing-induced residual damage. Combining SC1 cleaning with this technique allows to determine the depth profile of residual damage induced by mirror polishing. This result leads that the mirror polishing-induced damage can be removed by the SC1 cleaning.
X-ray Topography of Strain Fields Induced by 100 MeV Ti7+ Ion Irradiated Si(100)
Authors: Sharma B. B. , Gupta S. R. , Sharma R. K. , Kumar V. , Tiwari U. , Sen P. , Mehta G. K. 
Published: April 2011

AbstractThe lattice deformation caused by 100 MeV Ti7+ ion irradiation in Si (100) has been studied using X-ray topographic techniques. An important finding is the appearance of a strain field perpendicular to the ion beam direction in the irradiated region well separated from the projected range of implanted ions. This in-plane strain extends in the bulk of the sample and is not merely confined to the surface. The implanted region has been found to experience an out of plane strain which is expected to be tensile in nature.