bluuebunny/crossref_metadata_2025_split huggingface dataset:
A High Speed Contact-Type Image Sensor using Amorphous Silicon Alloy Pin Diodes
Authors: Kitamura K. , Mimura H. , Tsukada K. , Nakayama T. , Yamaguchi M. , Tawada Y. 
Published: March 2011

ABSTRACTA new A4-size contact-type image sensor with 8 elements per millimeter (1,728 elements) was developed by using amorphous silicon alloy pin photodiodes as the light receiving elements. The matrix switching method is employed for signal reading. This method can read the signals from all of the 1,728 photodiodes using a 54 (54-channel input) x 32 (32.channel output) matrix switching scheme. It is advantageous in that the required input and output external circuits can be simplified. To prevent signal crosstalk between the diodes in the matrix, amorphous silicon alloy pin diodes, which are made in the same process as the photodiodes for maintaining a low cost, are connected in series to each photodiode in reverse polarity as blocking diodes.To achieve superior signal-to-noise ratio and response at the same time, amorphous silicon alloy pin diodes are optimized to satisfy both a high photo-to-dark ratio and a high rectification ratio. The image sensor can operate at up to 2 MHz signal reading clock, maintaining a signal-to-noise ratio of over 24 dB under 0. 1–1x sec exposure.
The Role of the a-Si:H Layer in Metal / a-Si:H / Metal Memory Structures
Authors: Osborne I.S. , Hajto J. , Rose M.J. , Snell A.J. , Leœmber P.G. , Owen A.E. 
Published: March 2011

ABSTRACTIn this paper we report the role of the a-Si:H on the electrical behaviour of Metal/ a-Si:H / Metal memory devices. We have investigated layers deposited at 250°C by the glow discharge method with various doping concentrations, from undoped up to 104vppm of either diborane or phosphine in silane. We have found that the a-Si:H layer affects the initial forming process and the subsequent OFF state resistance. The hydrogen contents of the films have been measured and are found to correlate, for the p-type samples, with the forming voltage.
Engineering of PECVD Systems for Macroelectronic Applications
Authors: Martins R. , Ferreira I. , Carvalho C. N. , Maçarico A. , Guimarães L. 
Published: March 2011

ABSTRACTThe materials quality (uniformity and homogeneity) produced by PECVD technique depends on the plasma behaviour. Problems related to the gas dissociation ratio and powder formation are responsible for materials costs and the appearance of voids. In this paper, we present data concerning the role of the plasma and reactor design, on the deposition conditions, suggesting ways to improve them for large area device (macroelectronics) applications.
Role of Hydrogen Microstructure in Amorphous Silicon
Authors: Zafar Sufi , Schiff E. A. 
Published: March 2011

ABSTRACTA model for correlating the observed properties of hydrogenated amorphous silicon (a-Si:H) with the underlying hydrogen microstructure is reviewed. The model provides a unified description of defect equilibration, hydrogen evolution, rehydrogenation and hydrogen diffusion measurements.
Near-Surface Density of States in a-Si:H By Photoelectron Yield Spectroscopies.
Authors: Wang S.L. , Patriarca F. , Evangelisti F. 
Published: March 2011

ABSTRACTThe density of occupied states was investigated in a number of intrinsic a-Si:H samples by means of photoelectron yield spectroscopy operated in the constant final state mode. Valence band edge, exponential tail and deep state distribution were analyzed and compared with the bulk density of states as determined by spectral dependence of photoconductivity. By evaporating Cs atoms on the clean surface the Fermi level position was progressively shifted toward the conduction band and the evolution of localized states was investigated. On the assumption that these near-surface states are paramagnetic centers with positive correlation energy, the results agree with the prediction of the “defect pool” model.
Detection of Atomic Order in Quasiamorphous Materials
Authors: Timsit Roland S. , Waddington W.G. , Gallerneault C. 
Published: March 2011

ABSTRACTThe cross-correlation of intensity fields of different regions of an HREM micrograph can identify regions of structural order in an apparendy random matrix. This paper presents results of cross-correlations on computer-simulated HREM images of a diin Si crystallite located on a relatively thick slab of amorphous Si. These simulations confirm the efficacy of cross-correlations in retrieving atomic order from die image of an apparently amorphous material and thus confirm the interpretation of experimental results obtained earlier.
The Atomistic and Quantum Mechanical Origins of Light-Induced Defects in a-Si
Authors: Fedders P. A. , Fu Y. , Drabold D. A. 
Published: March 2011

ABSTRACTWe present an atomistic and quantum mechanical model of light-induced defects (the Staebler-Wronski effect). The model is based in part on our observations of molecular dynamics simulations with an ab initio code and requires a change in the charge of a well localized state in the gap, such as a dangling bond, to nucleate the new defects. Besides the new defects, a substantial rearrangement of the supercell is observed.
Deuteron Magnetic Resonance Studies of Structure and Photo-Induced Metastable Rearrangements in Deuterated Amorphous Si, Ge and SiGe Films
Authors: Norberg R. E. , Bodart J. , Corey R. , Fedders P. A. , Paul W. , Turner W. A. , Pang D. , Wetsel A. 
Published: March 2011

ABSTRACTThe spin dynamics of deuteron magnetic resonance (DMR) components have been studied in deuterated plasma-deposited thin films of a-Si, Ge and SiGe. Transient recoveries of perturbed deuteron magnetization components evolve via magnetization transport in the limit of large inhomogeneity. The evolution is well-described by an error function expression whose parameters correlate with the film photovoltaic quality as measured by the photoresponse ημτ and the photosensitivity, ΔI/Id. These relaxation results are correlated with our continuing DMR measurements of reversible metastable photo-induced rearrangements in high-quality a-Si:D,H films. These studies indicate that about 0.5% of the hydrogens interact with a light-induced defect.
Charge-Defect Thermodynamic Equilibrium and Metastable Defects in Amorphous Silicon
Authors: Fortmann C.M. , Cohen J. D. 
Published: March 2011

ABSTRACTThe thermodynamic equilibrium framework first presented at the Spring ′91 MRS meeting is refined and applied. The effect of temperature on band gap is added, resulting in a larger estimate of the loss in entropy associated with dangling bond formation. The magnitude of the entropy loss is consistent with a structural rearrangement. At the temperatures of interest, dangling bond defect formation is exothermic with negative entropy and free energy changes. The thermodynamic framework was used to address some practical issues including the estimation of the saturated dangling bond density resulting from low temperature light soaking and the electronic energy levels of the various dangling bond charge states.
Observation of Metastability in Amorphous Silicon Containing 0.1 at.% Hydrogen
Authors: Branz Howard M. , Iwaniczko Eugene 
Published: March 2011

ABSTRACTWe observe reversible quenched-in metastability in the dark conductivity of extremely low-H-content amorphous silicon (a-Si). The sample is sputtered, P-implanted a-Si containing 0.1 at.% of H. Except for the high value of its equilibration temperature (T*), 355° ± 20°C, this metastability is similar to that observed in doped hydrogenated a-Si (a-Si:H). The ∼10 at.% H present in a-Si:H is not essential for a-Si metastability. After hydrogenation with about 10 at.% of H, T* falls to 175° ± 10°C. We propose that higher H content reduces T* by increasing Si network flexibility.
Annealing of Metastable Recombination Centers in Hydrogenated Amorphous Silicon
Authors: Yoon Jong-Hwan , Lee Yoon-Zik 
Published: March 2011

ABSTRACTWe report results on the annealing behaviors of light- and deposition-induced metastable recombination centers, as measured by steady-state photoconductivity, in undoped hydrogenated amorphous silicon. The relaxation time inferred from the stretched-exponential time law reveals a thermally activated behavior, and the activation energies are nearly identical in both (Ea=1.1eV). This value is much less than that of the light-induced darkconductivity relaxation (Ea=1.7eV) measured simultaneously with photoconductivity. While in the deposition-induced case both activation energies of dark- and photoconductivity relaxation time are identical. These results support that there is more than one kind of defect created by light exposure, and at least, as considering activation energies for annealing defects, the light-induced recombination center differ from other metastable defects.
Relation Between Defect Density and Conductivity Changes with Light-Soaking and Annealing in a-Si:H
Authors: Shimizu T. , Iwami M. , Okagawa T. , Morimoto A. , Kumeda M. 
Published: March 2011

ABSTRACTIt is found in a-Si:H and N-doped a-Si:H that the ESR spin density Ns increases and saturates with light-soaking slower than the dark- and photoconductivities (αd and αp) do. In the recovery process by annealing, the change in Nsalso occurs slower than αd and αp. From the measurement of the activation energy for αd the change in αd is found to originate mainly from the movement of the Fermi level Ef. In order to elucidate the origin of different behaviors between Ns and αd or αp, the light-induced ESR and the constant photocurrent method measurements have been carried out.
Effect of Photodegradation on Transient and Steady State Forward Bias Characteristics of A a-Si:H P-I-N Diode
Authors: Amokrane R. , Vanderhaghen R. , Silver M. 
Published: March 2011

ABSTRACTWe have measured dark and photocurrent under double injection. The injection gain gives information on capture rate, dos shape and recombination mechanism. Before degradation, the recombination is bimolecular, and it becomes monomolecular after degradation. We observe effects of interface change as well as thickness inhomogeneity.
Multi-Cycling of Staebler-Wronski Effect
Authors: Guangling Kong , Guosheng Sun 
Published: March 2011

ABSTRACTThe effect of illumination/annealing multi-cycling treatment on the dark and photo conductivities of undoped a-Si:H film has been investigated. With the increase of cycling number the conductivities in annealed state and light-soaked state are drawn close to each other, which provides a unique irreversible effect.
The Farthest Reaches of a-Si,Ge:H,F Parameter Space… Where no One Has Gone Before
Authors: Morin P.A. , Wang N.W. , Wagner S. 
Published: March 2011

ABSTRACTWe report the deposition parameters for optimized a-Si,Ge:H,F alloys in the range of optical (Taue) gap of 1.22eV to 1.65eV. These deposition parameters were optimized using the photosensitivity and initial defect density as figures of merit. We observe two distinct regimes of film growth rate, dependent on the choice of source gases. Growth from fluoride source gases results in a growth rate of less than 0.6 Ås--1. Growth from a mixture of fluorides and silane gives a range of growth rates from 2 Ås-l to 5.5Ås1. Alloys in both regimes display the low defect densities and the high photosensitivities required for devices.
Time-of-Flight Measurement on a-Ge:H and a-SiGe:H Alloys
Authors: Liu E.Z. , Pang D. , Paul W. , Chen J.H. 
Published: March 2011

ABSTRACTWe report TOF measurements on high quality intrinsic a-Ge:H and a-SiGe:H films of E04=1–4.eV in temperature ranges of 200 to 280 and 230 to 300K, respectively. Complete charge collection is achieved in all measurements. For a-Ge:H films, the (μτ)e product obtained from the Hecht plot is (5±3)×10-8 cm2/V above 240K and decreases at lower temperatures. The electron transit signal is dispersive at all temperatures. The a obtained from ttV-1/αis 0.23 at 200K and approaches 1.0 at 260K. The electron drift mobility μd shows activated behavior, with an energy of 0.37±0.05eV, and has an extrapolated room temperature value of 0.03 cm2/Vs. Compared to a-Ge:H, μd of a-SiGe:H alloy samples is lower by one order of magnitude but has a similar activation energy. These results are consistent with a band tail hopping transport model.
Amorphous Ge/Si Multilayer Structures as Models for Optical Memories
Authors: Järrendahl K. , Jansson R. , Sundgren J.-E. , Arwin H. 
Published: March 2011

ABSTRACTPrototype memory cells of a proposed three-bit memory device, whose optical read-out is based on the ellipsometric principle, nas been fabricated by deposition of 5 nm layers of amorphous silicon and amorphous germanium on crystalline silicon substrates. The differences in the ellipsometric parameters of memory cells corresponding to different logical states were much larger than the instrumental resolution. The possibility to optimize with respect to photon energy and angle of incidence is demonstrated.
Non-Equilibrium Carrier Dynamics in a-Si:H/a-SiC:H Multilayers
Authors: Petrauskas M. , Kolenda J. , Galeckas A. , Schwarz R. , Wang F. , Muschik T. , Fischer T. , Weinert H. 
Published: March 2011

ABSTRACTFor a series of a-Si:H/a-SiC:H quantum well structures and superlattices the diffusion coefficient for the lateral ambipolar motion of optically excited free carriers was measured using the transient grating technique. A significant dependence of the diffusion coefficient on the well layer thickness was found. With decreasing quantum well thickness the lateral mobility decreases. These observations may be explained assuming that scattering due to interface roughness is the dominant scattering process.
Metastability of Light-Induced Defects in Very Low Density of Gap States α- Si1-αCα:H Alloys
Authors: Sebastiani M. , Fiorini P. , Alvarez F. , Pozzilli F. , Pulci O. , Evangelisti F. 
Published: March 2011

ABSTRACTWe have prepared silicon carbon alloys with Tauc's gap of 2.1 eV, low defect density (≃ 3–1015cm-3) and large photoconductivity (αPhoto/αdark=105 in AM 1.5 illumination). On these samples light soaking induces a large number of metastable gap defects which are annealed out at 250 °C. We have studied the kinetics of defect formation varying the duration of light exposure and the light intensity. The experimental data are consistent with a bond breaking model (conversion of tail weak bonds into dangling bonds), provided that the actual occupation of tail states is taken into account.
Improved Properties of a-SiC:H Alloys with Reduced Density of CH3 Radicals
Authors: Camargo S. S. , de Oliveira M. L. , Pasa A. A. , Gatts C. 
Published: March 2011

ABSTRACTIn this paper we report on the properties of a-SiC:H alloys with reduced density of CH3 radicals obtained by hydrogen dilution of gases. A reduced density of voids, hydrogen content and density of carbon bonded hydrogen atoms, were obtained; while carbon content and density of Si-H bonds are not affected much. A reduction of the optical gap and an increase of the refractive index were observed and related to the reduced densities of CH3 groups and voids. Dark- and photo- conductivity measurements showed that a performance comparable to the best undiluted films may be easily achieved, associated with a shift of the dark Fermi level towards the conduction band.
A Thermally Stable Silicon Rich Amorphous Silicon Nitride Alloy for Electronic Device Applications
Authors: Bernstein Joseph B. , Gleason Edward F. , Wyatt Peter W. 
Published: March 2011

ABSTRACTWe have developed an alloy of silicon rich amorphous silicon nitride as a linkable interlevel metal dielectric. This material is thermally stable through a heat treatment of 425°C for 30 minutes. The hydrogen content remains at approximately 21 at.%, even after this heat treatment. The breakdown potential is 1.9 × 106 V/cm at which point a metallic filament link forms between the metal contacts. The index of refraction is 2.43 and the HF permittivity is 9 Co- One important property is its ability to store polarized charge like an electret. This feature could allow it to be used in memory applications like MNOS. The alloy is also photoconductive with a response time of less than 5 μs, allowing it to be used as part of an optically sensitive circuit element.
Structural Properties of High Electronic Quality a-Si1-xCx:H by Infrared Spectroscopy
Authors: Eberhardt K. , Lotter E. , Heintze M. , Mohring H.-D. , Bauer G.H. 
Published: March 2011

ABSTRACTInfrared (ir) spectroscopy is used to investigate the structural properties of a-SiC:H in a wide compositional range and as a function of film thickness. Hydrogen content NH increases considerably with increasing carbon fraction. For low carbon alloys this is mainly due to an increase of hydrogen bonded to silicon, incorporated in a mono- or dihydride form. Above Eg=2.3eV the proportion of hydrogen incorporated in C-H bonds increases considerably. Oxidation of high C alloys is observed. Converting experimental transmission exactly into absorption data yields thickness independent NH values. It is shown that the previously reported discrepancy between the hydrogen content calculated from ir and nuclear reaction techniques is an artifact of the ir analysis.
The Impact of a Long-Ranged Random Potential on the Transport Properties of Amorphous Semiconductors
Authors: Overhof Harald 
Published: March 2011

ABSTRACTWe discuss electrostatic random potentials in doped and in compensated amorphous semiconductors. These potentials are caused by the residual inhomogeneity of a random distribution of charged dopants and their compensating charges. Random potentials are also present in undoped material with negative-U defects. A high density of positive-U defects can also give rise to a random potential in undoped material.We demonstrate with the help of detailed model calculations the effect of such random electrostatic potentials on the transport properties. For transport in extended states the random potential does not give rise to a mere shift of the mobility edge. Instead several new features are observed: the activation energy of the resulting Ohmie dc conductivity is virtually unaffected by the random potential in contrast to the activation energy of the thermoelectric power and that of the Hall effect, respectively. The Ohmie dc current changes at high fields into a superlinear current. The random potential contributes to the dispersion of the transients in time-of-flight experiments but leaves the field dependence of the TOF mobility unaltered. Comparing our results with experimental data we discuss under which circumstances the effect of random potentials can be identified.
The Study on Microstructure by NMR, FTIR, Raman, Conductivity and Optical Bandgap in Hydrogenated Amorphous Silicon Prepared by Novel Fabrication Methods
Authors: Hsu K. C. , Chang H. , Hong C. S. , Hwang H. L. 
Published: March 2011

ABSTRACTIt was found that hydrogen dilution in the SiH4/H2 mixture tend to show a sharp line-shape in the NMR spectra as the substrate temperature is higher than 300 °C. The hydrogen-atom-treatment method also produces the same effect at a lower substrate temperature about 250°C. The Raman scattering spectra show that the hydrogen-atom-treatment creates the microcrystalline structure at a temperature higher than 250°C while hydrogen dilution produces mixed phases containing amorphous phase and a small quantity of micro-crystalline phase. Together with the optical bandgap narrowing, the increase of the dark conductivity and the reduction of photo-to-dark conductivity ratio, these samples indicate that with more hydrogen incorporation during deposition and plasma hydrogen treatment, these films possess a much compact structure, and the degree of crystallinity of hydrogenated silicon film was found to be systematically changed.
Simulation of the Steady-State Photocarrier Grating Method Applied to Amorphous Materials
Authors: Abel C.-D. , Bauer G. H. 
Published: March 2011

ABSTRACTGeneral features of the steady-state photocarrier grating technique applied to amorphous semiconductors are investigated by complete numerical simulation. The results are interpreted with an analytical model which delivers a closed-form expression for β(A,E) assuming dominance of one carrier type. The variation of the electric field E instead of the grating period A is suggested as an easier and more accurate tool for the experimental technique.
Deposition Temperature and Optoelectronic Properties of a-Si:H Films
Authors: Wiatkowski C. S. , Hirsch W. , Kunst O. 
Published: March 2011

ABSTRACTIn the present work the change of the opto-electronic properties of intrinsic a-Si:H films as a function of their deposition temperature is investigated by transient photoconductivity measurements with the contactless Time Resolved Microwave Conductivity (TRMC) technique. As well in-situ as ex-situ TRMC-measurements will be presented. It is concluded that the electron drift mobility for a-Si:H films deposited in the temperature range between 200° C and 300° C does not depend on the deposition temperature. For temperatures below 200° C the electron drift mobility decreases with decreasing deposition temperature. Annealing of opto-electronic properties of intrinsic a-Si:H films deposited at lower temperatures is observed.
Delayed Field Transient Photocurrent Measurements in a-Si:H
Authors: Antoniadis Homer , Schiff E. A. 
Published: March 2011

ABSTRACTWe have measured the transient photocurrent in “time-of-flight” structures of a-Si:H using bias voltages applied following photocarrier generation by a laser flash. The delayed field technique appears promising both as a probe of the deep level distribution and also of photocarrier thermalization. We describe a simplified theory for the delayed field transients including the effects of the delay time and the magnitude of the applied voltage. The theory accounts for the measurements adequately.
Optical Absorption Spectra Under DC Light Bias in Undoped a-Si:H
Authors: Liu J. Z. , Conde J. P. , Lewen G. , Roca i Cabarrocas P. 
Published: March 2011

ABSTRACTUnder a dc light bias, the ac constant photocurrent method (CPM) yields an anomalous subgap optical absorption over that without the bias. When the intensity of the bias is high, an absorption band appears. However, absorption measured by ac photothermal deflection spectroscopy (PDS) is much less affected by the bias. A simple model qualitatively explains the effect on the PDS spectra and suggests that the anomalous CPM absorption is an apparent one which represents a variation of the recombination lifetime.
A More Than 18% Efficiency Hit Structure a-Si/c-Si Solar Cell Using Artificially Constructed Junction (ACJ)
Authors: Kuwano Y. , Nakano S. , Tanaka M. , Takahama T. , Matsuyama T. , Isomura M. , Nakamura N. , Haku H. , Nishikuni M. , Nishiwaki H. , Tsuda S. 
Published: March 2011

ABSTRACTWe have obtained the world's highest total area conversion efficiency of 11.1% for a 100cm2 integrated-type single-junction a-Si solar cell submodule. This was achieved by the development of various advanced technologies, such as a new ultra-thin i/n interface layer and a new laser patterning method using an ablation phenomenon.To acheive further improvement in the conversion efficiency of a-Si based solar cells, we focus on polycrystalline silicon (poly-Si) thin-film for a-Si/poly-Si tandem solar cells. As far as material technology is concerned, we have used a new solid phase crystallization (SPC) method from amorphous silicon (a-Si) films deposited by plasma-CVD. The maximum mobility of 623 cm2/V.s was achieved on textured substrates at a carrier concentration of 3.0 × 1015 cm-3. This film has been applied to the active layer of poly-Si solar cells on metal substrates and a conversion efficiency of 6.2% has been obtained with poly-Si film of 12 μm thickness made by SPC at 600°C.In the field of device technology, we have developed new artificially constructed junction (ACJ) solar cells using p-type a-Si/i-type a-Si/n-type crystalline silicon (c-Si). We call this a HIT (Heterojunction with Intrinsic Ihin-layer) structure, and we have achieved a conversion efficiency of 18.1% for this type of solar cells. This is the highest reported value for a cell with a junction fabricated at low temperature (∼ 120°C).