bluuebunny/crossref_metadata_2025_split huggingface dataset:
Substrate Temperature Dependence of the Optical and Electronic Properties of Glow Discharge Produced a-Ge:H
Authors: Li Yuan- Min , Turner Warren A. , Lee Choochon , Paul William 
Published: March 2011

ABSTRACTGlow discharge a-Ge:H films produced at substrate temperatures (Tδ) between 50°C and 350°C, with and without a top a-Si:H capping layer, have been studied. The uncapped samples produced at Tδ < 250°C suffer severe post-deposition atmospheric contamination, resulting in orders of magnitude of unstable increase in both the photoresponse and dark conductivity. The capped samples, which have very much reduced immediate post-deposition contamination, show only small increases in the efficiency-mobility-lifetime product (ŋμτ) with increasing Tδ. This contrasts with the results of earlier similar studies on uncapped samples, which showed a peak in either the photoconductivity1 or the ratio of photoconductivity to dark conductivity2 for 150°C < Tδ < 2000C. We have also observed a decrease in the bandgap, a narrowing of the band-tails, an increase in the index of refraction, and a reduction of hydrogen content of the films with increasing Tδ.
Carrier Transport Properties of DC Magnetron Reactive Sputtered a-Si:H Films
Authors: Pinarbasi M. , Maley N. , Abelson J. R. , Chu V. , Wagner S. 
Published: March 2011

ABSTRACTWe have prepared device quality hydrogenated amorphous silicon (a-Si:H) films by DC magnetron reactive sputtering in an Ar+H2 atmosphere. The hydrogen content (CH) of these films ranges from ∼10 to ∼28 at.% (determined from IR absorption) and is controlled mainly by the hydrogen partial pressure in the discharge. The electron and hole transport, and the density of defect states show that these films are suitable for solar cell applications. In this report we will emphasize the carrier transport properties of the films. The electron drift mobilities, determined by time-of-flight experiments, are between 0.5 and 2 cm2/V-sec. The minority carrier (hole) mobility-recombination lifetime product, (μτrec)p, has been determined on Schottky barrier structures from a fit of the voltage dependence of the photocurrent to the Hecht expression. This measurement gives results of (μτrec)p ∼ 0.9- 3×10−8 cm2/V. The density of deep-level defect states for these films (10≤CH≤28), measured with CPM, is between ∼1×1015 and ∼1×1016 cm−3. The AM-1 photoconductivity is in the range from 0.8−3.5×10−5 (Ω-cm)−1 and the dark conductivity decreases from ∼1×10−9 to ∼1×10−12 (Ω-cm)−l as the hydrogen content (CH) increases. These results show that device quality a-Si:H films can be grown by the DC magnetron reactive sputtering technique.
Alternative Complex Liquid Crystal Displays
Authors: Raynes E P 
Published: March 2011

ABSTRACTThe first major progress towards complex LCD's has been made using arrays of thin film transistors (TFT's) fabricated using amorphous silicon (a - Si) technology. However, apart from other two and three terminal devices, there are also two new LCD technologies which directly improve the performance of the LCD without the need for extra switching elements. These are the supertwist (or STN) LCD and displays based on ferroelectric liquid crystals (FELC). These two alternative technologies are described and teir performance compared with that of displays fabricated using α - Si TFT's.
Plasma Chemistry in Silane and Silane-Germane Discharge Deposition
Authors: Gallagher A. , Doyle J. , Doughty D. 
Published: March 2011

ABSTRACTThe spatial and energetic characteristics of rf and dc parallel-plate deposition discharges are discussed, along with their implications to plasma chemistry. We discuss the results and interpretation of our recent measurements of silane, disilane, germane, and mixed-gas stochiometry. These yield the initial dissociation branching between even and odd dangling-bond radicals, as well as the relative roles of higher silanes and silyl germanes (produced by the discharge) in the chemistry. Our deposition model and supporting data are discussed, as are various causes of film-quality variations which this suggests.
Properties of High Conductivity Phosphorous Doped Hydrogenated Microcrystalline Silicon and Application in Thin Film Transistor Technology
Authors: Kanicki J. , Hasan E. , Griffith J. , Takamori T. , Tsang J. C. 
Published: March 2011

ABSTRACTDevice quality phosphorous (P) doped hydrogenated microcrystalline silicon (n+μc - Si:H) has been prepared by using the plasma enhanced chemical vapor deposition technique. The dependence of physical, chemical, structural and electrical properties on substrate temperature have been investigated. Conductivities for thick films up to 12 Ω−lcm−1 and 40 Ω−1cm−1 have been achieved for layers deposited at 300°C and 500°C, respectively. For films 50 nm thick deposited at 300°C a conductivity of about 5 Ω−1cm−1 has been obtained. A maximum average grain size around 30 nm was obtained. The etch rates of P-doped microcrystalline silicon have been found to be between 8 and 10 times higher than that of undoped hydrogenated amorphous silicon (a-Si:H) films deposited at the same temperature. Thin film transistors incorporating heavily P-doped amorphous and microcrystalline layer between source/drain metal and the a-Si:H channel have been fabricated. We show that an n+μc - Si:H source/drain contacts in thin film transistors provides very good characteristics, yielding an average effective field effect mobility, threshold voltage, and on/off current ratio of about 0.9cm2V−1 sec−1, below 4 V, and above 107, respectively.
Is B(CH3)3 An Interesting Alternative to B2H6 for a-Si:H p Doping?
Authors: Zongyan Wu , Lloret A. , Siefert J.-M. , Cabarrocas P. Roca i , Equer B. 
Published: March 2011

ABSTRACTThe contamination effects induced by B2H6 and B(CH3)3 in a-Si:H layers are compared, using in-situ Kelvin probe experiments as well as SIMS measurements. It is found that B(CH3)3 induces at least 50 times less contamination, even at 250°C. It is also found that materials containing CH3 radicals have a lower electron affinity.
Temperature Dependence of Structure, Transport and Growth of Microcrystalline Silicon: Does Grain Size Correlate with Transport?
Authors: Tsai C. C. , Anderson G. B. , Wacker B. , Thompson R. , Doland C. 
Published: March 2011

ABSTRACTThe temperature dependence of the growth, structure and transport of plasma-deposited microcrystalline and polycrystalline silicon films have been investigated over the temperature range of 50°C to 350°C. While low substrate temperature yields small grain sizes as expected, high temperature also tends to suppress the grain growth, contrary to the normal behavior observed in thermal CVD (chemical vapor deposition) where crystallinity grows with temperature. In fact, the highest temperature of 350°C corresponds to the lowest degree of crystallinity. Furthermore, it is found that, unlike the polycrystalline Si prepared by thermal CVD, the transport properties of the Si films do not necessarily correlate with the grain size or structural defects. While the largest average grain size of 800–1000 Å was obtained at 200°C, the highest Hall mobility and conductivity were obtained near 250°C, which corresponds to a material with smaller grains and an abundance of voids.
Radiation Effects on the Optical and Transport Properties of Amorphous Silicon
Authors: Payson J. Scott , Li Yang , Woodyard James R. 
Published: March 2011

ABSTRACTThe focus of our work is to investigate the role of defects introduced by particle irradiation on the electrical and optical properties of amorphous silicon based alloys. We have studied photovoltaic cells and intrinsic films and have found that irradiation produces electrical and optically active defects which anneal at temperatures less than 200 degrees Celsius. The defects produce sub-band-gap states with a peak 1.4 eV below the conduction band edge; the structure of the material does not appear to be altered as evidenced by the band-tail states. Significant room temperature annealing effects have been observed following 1.00 MeV proton irradiation of intrinsic films.
Low Temperature Crystallization of Amorphous Silicon Films Using an Excimer Laser
Authors: Ready S. E. , Boyce J. B. , Bachrach R. Z. , Johnson R. I. , Winer K. , Anderson G. , Tsai C. C. 
Published: March 2011

ABSTRACTIn an effort to enhance the electrical properties of silicon thin films, we have performed recrystallization experiments on a variety of amorphous silicon films using an excimer laser. The intense, pulsed UV produced by the laser (308nm, using XeCl gas) is highly absorbed by the amorphous material and thus provides intense localized heating in the near surface region. Two types of starting films were studied: plasma CVD a-Si:H and LPCVD a-Si. The subsequent modification produces crystallites whose structure and electrical characteristics vary due to starting material and laser scan parameters. The treated films have been characterized using Raman, x-ray diffraction, TEM, SIMS and transport measurements. The results indicate that crystallites nucleate in the surface region. The degree of crystallization near the surface increases dramatically as a function of deposited laser energy density and less so as a function of laser shot density. The hall mobility of the highly crystallized samples exhibit an increase of 2 orders of magnitude over the amorphous starting material. In the PECVD material, the rapid diffusion of hydrogen causes voids to be formed at intermediate laser energy densities and removal of film at higher energy densities. The LPCVD material withstands the high laser energies to produce well crystallized films with crystallite sizes greater then 1000Å.
Deposition of a-Si:H Films with a Remote Hydrogen Plasma
Authors: Johnson N. M. , Walker J. , Doland C. M. , Winer K. , Street R. A. 
Published: March 2011

ABSTRACTResults are presented on the properties of a-Si:H thin films deposited with a remote hydrogen plasma. An essential feature of the reactor design is the use of an alumina (rather than quartz) tube to contain the hydrogen plasma for low oxygen contamination of the films. High doping efficiency is demonstrated for both P-and B-doped amorphous films, and the effects of high silane dilution and deposition temperature are illustrated with P-doped amorphous and microcrystalline silicon films.
Amorphous Silicon-Germanium Alloy Solar Cells with Profiled Band Gaps
Authors: Yang J. , Ross R. , Glatfelter T. , Mohr R. , Guha S. 
Published: March 2011

ABSTRACTWe have studied the spectral dependence of various types of amorphous silicon-germanium (a-Si:Ge) alloy p-i-n solar cells in which the band gap of the intrinsic (i) layer is profiled between 1.4 and 1.7 eV. It is observed that the cell performance depends critically on the shape of the profile, especially for red-light illumination where the device output is found to vary by more than a factor of two. We have correlated the experimental data with optical absorption and dynamic internal collection efficiency (DICE) measurements. We have also fabricated two-cell tandem and three-cell triple devices by incorporating a-Si:Ge alloy with multiple band-gap profiles in the bottom cell and achieved 13.0% and 13.7% conversion efficiencies, respectively. These are the highest efficiency amorphous silicon-based alloy solar cells reported to date.
High Deposition Rate P-I-N Solar Cells Prepared from Disilane Using VHF Discharges
Authors: Chatham H. , Bhat P. K. 
Published: March 2011

ABSTRACTWe report on the influence of the discharge excitation frequency on the material properties of intrinsic a-Si:H films deposited from disilane. A monotonic increase in the deposition rate with increasing frequency is observed in the range 13.56–110 MHz. Comparison of the properties of materials deposited at ˜1.5 nm/s using 13.56 and 110 MHz discharges in disilane indicates that there are some advantages to using 110 MHz. The performance of p-i-n devices fabricated from disilane at ˜2 nm/s at these two frequencies support this conclusion. We have fabricated a device from disilane at 1.8 nm/s using a frequency of 110 MHz with an AMl.5 efficiency of 9.7%.
Substrate Temperature Dependence of the Structural Properties of Glow Discharge Produced a-Ge:H
Authors: Jones Scott J. , Lee Susanne M. , Turner Warren A. , Paul William 
Published: March 2011

ABSTRACTA series of glow discharge a-Ge:H films has been produced at substrate temperatures, Ts, between 100 and 350°C. The films were structurally characterized using Differential Scanning Calorimetry (DSC), Gas Evolution (GE), Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM). The DSC and GE results are substrate dependent. Two exothermic peaks are seen in DSC spectra for films deposited on aluminum foil while only one peak, identified by Raman measurements as the crystallization peak, is seen for samples deposited on beryllium, NaCl, carbon coated mica, crystalline silicon and 7059 glass. The crystallization peak temperature of films deposited on 7059 glass decreases with increasing Ts until 250°C where it then remains constant up to Ts=350°C. GE results show a relative increase of high temperature evolution with an increase in Ts. A well defined island/tissue structure seen in TEM micrographs of low Ts films disappears at higher Ts values. SEM measurements show columnar structure present only in films produced at Ts≤250°C. All the structural measurements point to a more stable material of higher density for Ts>250°C.
Stability, Performance and Trend Modeling of Amorphous Silicon Photovoltaic Modules
Authors: Mrig L. , Berry W. B. 
Published: March 2011

ABSTRACTThe Solar Energy Research Institute (SERI) has been conducting field tests on amorphous silicon modules and analyzing the results in terms of both stability and performance. Both single p-i-n and tandem modules have been under evaluation for the past few years. This paper presents performance test results for several of these modules. Analytical models for efficiency and fill factor are presented. These models are used to project design lifetime performance. Mean square error curve fitting techniques are used to overcome data scatter. The models bracket best and worst case performance. A phenomena based, double exponential model is included to project end of life performance. This model primarily focuses on degradation due to light induced defects.
Hydrogen-Plasma Reactive Flushing for a-Si:H P-I-N Solar Cell Fabrication
Authors: Tsuo Y. S. , Xu Y. , Crandall Richard S. , Ullal H. S. , Emery K. 
Published: March 2011

ABSTRACTWe have studied the effects of a hydrogen-plasma reactive flush between the pand i-layer depositions in fabricating solar cells of glass/TCO/p(a-SiC:H)-i(a-Si:H)-n(a-Si:H)/metal in a single-chamber, glow-discharge deposition system. Spectral response, photoluminescence, and photovoltaic conversion efficiency measurements show that the hydrogen-plasma reactive flush is effective in reducing the p-i interface recombination of charge carriers and in improving solar cell performance.
Double-Stacked a-Si/a-Si and a-Sic/a-Si Tandem Solar Cells with High Efficiency and High Reliability
Authors: Sakai Hiroshi , Yoshida Takashi , Fujikake Shinji , Ichikawa Yukimi 
Published: March 2011

ABSTRACTAmorphous silicon (a-Si) based solar cells with a double-stacked tandem structure have been studied with a view to reduce light-induced degradation in photovoltaic performance without lowering the initial conversion efficiency. We have attained a conversion efficiency of 11.3% in a 1cm2 a-Si/a-Si tandem cell and 10.8% in a 1cm2 a-SiC/a-Si tandem cell. Using an a-Si/a-Si tandem cell with an initial efficiency of more than 10%, we have carried out a light soaking test, and found that the degradation in conversion efficiency was about 10% under open-circuit condition after 600 hours exposure.
Band Tailing and Transport in a-SiGe:H-Alloys
Authors: Bauer G. H. , Nebel C. E. , Schubert M. B. , Schumm G. 
Published: March 2011

ABSTRACTOptical and transport studies of both cb- and vb-tail states in a-Si1−xGex:H such as subband absorption (PDS), instationary photocurrent experiments (TOF, PTS) for electrons and holes, Modulated Photocurrent Spectroscopy (MPS), and Raman scattering have been performed. The main consequences of Ge-alloying into the a-Si:H network are i) an increase in cb-tail state density at the conduction band edge and in the exponential cb- tail even for small x (O<x<0.3), accompanied by ii) a rise in deep cb-tail and midgap states which to some extent can be reduced by appropriate deposition methods; iii) at the valence band side up to x≈0.3 the tail seems not to be affected at all and for 0.3<x<0.9 the vb-tail obviously can be kept similar to that of a-Si:H (Evo≈(50–60) meV). Halfwidths of Raman TO-like modes point to the existence of a rigid Si-network in O<x<0.3 in which Ge is incorporated and to a transition at x>0.35 into a Si-Ge compound structure with maximum disorder at x≈0.5.
Hole properties of a-Si:H and a-Si,Ge:H,F alloys
Authors: Chu V. , Liu J. Z. , Conde J. P. , Wagner S. 
Published: March 2011

ABSTRACTWe present a study of the temperature and intensity dependence of the (μτ)p for Schottky barriers on an a-Si:H and a 1.3eV aSi,Ge:H,F alloy. Measured values for the activation energy of (μτ)p, , and the generation rate exponent of the (μτ)p, φ, show good agreement with calculated values. We also relate the (μτ)p with the mid-gap defect density, Na.
Effects of Hydrogen Radicals on the Composition and Hydrogen Bonding of Amorphous Silicon-Germanium Thin Films
Authors: Albright D. E. , Fortmann C. M. , Russell T. W. F. 
Published: March 2011

ABSTRACTA reaction engineering model of the mercury sensitized photochemical vapor deposition of amorphous silicon-germanium thin films is used in conjunction with experimental results to describe the role of hydrogen radical reactions in determining film composition, hydrogen bonding and microcrystallinity. Selective removal of silicon from the film by hydrogen radicals is shown to increase with decreasing temperature, raising the germanium content of films in hydrogen diluted depositions below 2 torr. Etching of a-Ge:H by hydrogen radicals is determined to be nearly two orders of magnitude slower than that of a-Si:H. Hydrogen radicals are also shown to promote microcrystallinity by selectively removing amorphous phase silicon and bonded hydrogen.
Physical Properties of Annealed a-CSiGe:H Alloys
Authors: Demichelis F. , Kaniadakis G. , Pirri C. F. , Tagliaferro A. , Tresso E. 
Published: March 2011

ABSTRACTThe optoelectronic properties of the new semiconducting alloy a-CSiGe:H have been studied with particular regard to the dependence upon deposition and annealing temperature. Infrared and electrical results are interpreted in terms of hydrogen bonding.
Effect of Low-Level Boron Doping on Transport Properties of a-Si:H and a-SiGe:H Alloys
Authors: Yang Liyou , Catalano A. , Arya R. R. , Bennett M. S. , Balberg I. 
Published: March 2011

ABSTRACTLarge simultaneous changes in ambipolar diffusion length and d.c. photoconductivity are observed with boron doping below 5ppm. We show that the observation can be explained successfully with a model for the doping effect, which is also consistent with earlier studies. The μτ products for both carriers as a function of doping are determined. The light intensity dependence of diffusion length and photoconductivity is also discussed.
Dispersive Hydrogen Motion and Creation of Light-Induced Defects in Hydrogenated Amorphous Silicon
Authors: Jackson W. B. 
Published: March 2011

ABSTRACTThis paper investigates the application of the dispersive hydrogen diffusion defect kinetic equation for the generation of light-induced defects. Self-limited monomolecular carrier defect generation by dispersive motion can explain the observed t1/3 and the G0.6 dependence where t is the illumination time and G is the illumination intensity as well as the equilibrium defect density as a function of temperature. However, the temperature dependence of the creation rate and compatibility with current degradation experiments remain unresolved problems.
Defect Relaxation in Disordered Materials: Stretched Exponentials, Meyer-Neldel Rule, and Staebler-Wronski Effect
Authors: Crandall Richard S. 
Published: March 2011

ABSTRACTUsing an exponential distribution of activation barriers, annealing data for metastable effects in hydrogenated amorphous silicon, a-Si:H, are quantitatively explained. This includes the stretched exponential time dependence of annealing and a Meyer-Neldel rule for the annealing time constant. An exponential distribution of annealing energies arises because defects are frozen in during growth at high temperature. Mechanisms that lead to an exponential distribution of annealing energies are weak bond-breaking and charge trapping.
Stability Studies on A-Si:H Films
Authors: Dalal Vikram L. , Fuleihan Camille 
Published: March 2011

ABSTRACTWe report on kinetics of photo-induced degradation in a-Si:H films and devices. We find that in device-quality films, the degradation kinetics do not follow either the time or the intensity behavior predicted by the bondbreaking model. Instead, there is a strong tendency towards saturation, as predicted by Redfield's equilibration model. We also find that increased SiH2 bonding in the film leads to increased degradation. The initial degradation kinetics follow the intensity behavior predicted by the trap-todangling bond conversion model of Adler. Trace levels of impurities such as O and P significantly increase the initial degradation, also in accord with the predictions of the trap conversion model.
Imaging Transfer Devices Operated by PSD Mode a-Si P-I-N Junctions
Authors: Yamaguchi M. , Murakami S. , Todo S. , Tawada Y. 
Published: March 2011

ABSTRACTTwo types of position sensitive device (PSD) using a-Si:H thin films have been developed. One has been produced by large area plasma CVD, with usual metal deposition techniques. The other is the application of a linear image sensor as a one dimensional position sensor. There are some advantages and disadvantages in these two types of position sensitive device. Resolution of the linear image sensor is limited by the size of the elements and the pitch; in contrast, uniformity of the electrodes on the p-i-n diode and thickness of the a-Si thin film are the key factors for the resolution of one and two dimensional analogue PSDs.The analogue PSD is applicable to a digitizer which takes the role of a man-machine (computer) interface. The large area two dimensional digitizer was fabricated using the same technique as large area solar cell production, and was shown to be useful as a drawing tool on a CRT or other display devices with the aid of a micro-computer.
Surface States on a-Si:H,F Grown from SiF4 and H2
Authors: Maruyama A. , Liu J. Z. , Chu V. , Shen D. S. , Wagner S. 
Published: March 2011

ABSTRACTWe describe a detailed study of surface states on a-Si:H, F films deposited by DC-plasma from SiF4 and H2. In the a-Si:H, F growth from these source gases, the density of surface states (Nss) and the Urbach Energy (Eu) show a reciprocal relation, meaning that the film grown with less bond distortion is accompanied by a higher density of surface states. These surface states can be reduced by keeping the films at growth temperature after termination of growth; immediate cooling produces a high density. This suggests that bonds can rearrange on or near the film surface at growth temperature, after growth termination. Nss can be made as high as l×1014 cm−2. The surface states can be measured by optical subgap absorption, but do not give an ESR signal. A high density of these surface states lowers the Pd-Schottky barrier height. Time-of flight electron collection data show that the surface states act as deep electron traps, located at about 0.4eV below the conduction band edge. We present and discuss other experimental results to help understand these nature of the surface state on a-Si:H, F.