bluuebunny/crossref_metadata_2025_split huggingface dataset:
Equivalent-circuit Modeling of Microcrystalline Silicon pin Solar Cells prepared over a Wide Range of Absorber-layer Compositions
Authors: Reynolds Steve , Smirnov Vladimir 
Published: August 2010

AbstractAn equivalent-circuit electrical model is used to simulate the photovoltaic properties of mixed-phase thin-film silicon solar cells. Microcrystalline and amorphous phases are represented as separate parallel-connected photodiode equivalent circuits, scaled by assuming that the photodiode area is directly proportional to the volume fraction of each phase. A reasonable correspondence between experiment and simulation is obtained for short-circuit current and open-circuit voltage vs. volume fraction. However the large dip in fill-factor and reduced PV efficiency measured for cells prepared in the low-crystalline region is inadequately reproduced. It is concluded that poor PV performance in this region is not due solely to shunting by more highly-crystalline filaments, which supports the view that the low-crystalline material has transport properties inferior to either microcrystalline or amorphous silicon.
Photonic Crystal Back Reflectors for Enhanced Absorption in Amorphous Silicon Solar Cells
Authors: Curtin Benjamin , Biswas Rana , Dalal Vikram 
Published: August 2010

AbstractPhotonic crystal back reflectors offer enhanced optical absorption in thin-film solar cells, without undesirable losses. Rigorous simulations of photonic crystal back reflectors predicted maximized light absorption in amorphous silicon solar cells for a pitch of 700-800 nm. Simulations also predict that for typical 250 nm i-layer cells, the periodic photonic crystal back reflector can improve absorption over the ideal randomly roughened back reflector (or the ‘4n2classical limit') at wavelengths near the band edge. The PC back reflector provides even higher enhancement than roughened back reflectors for cells with even thinner i-layers. Using these simulated designs, we fabricated metallic photonic crystal back reflectors with different etch depths and i-layer thicknesses. The photonic crystals had a pitch of 760 nm and triangular lattice symmetry. The average light absorption increased with the PC back reflectors, but the greatest improvement (7-8%) in short circuit current was found for thinner i-layers. We have studied the dependence of cell performance on the etch depth of the photonic crystal. The photonic crystal back reflector strongly diffracts light and increases optical path lengths of solar photons.
On The Mechanism of Nucleation in Pulsed-laser Quenched Si Films on SiO2
Authors: Deng Yikang , Hu Qiongying , Chung Ui-Jin , Chitu Adrian , Limanov Alexander , Im James 
Published: August 2010

AbstractWe have investigated the solid nucleation mechanism in laser-quenched Si films on SiO2. Previously neglected experimental steps, consisting of BHF-etching and irradiation in vacuum, were implemented to reduce potential extrinsic influences. The resulting experimental findings and computational analysis lead us to conclude that solid nucleation consistently takes place heterogeneously at, and only at, the bottom liquid Si-SiO2 interface.
Investigation of Near-IR Emission from Hydrogenated Nanocrystalline Silicon – The Oxygen Defect Band
Authors: Fields Jeremy David , Taylor Craig , Bobela David , Yan Baojie , Yue Guozhen 
Published: August 2010

AbstractHydrogenated nanocrystalline silicon (nc-Si:H), a mixture of nanometer sized crystallites and amorphous silicon tissue, demonstrates a photoluminescence band centered at ∼ 0.7 eV, which emerges in response to annealing at an onset temperature of ∼ 200–300 °C. This temperature range correlates well with hydrogen effusion spectroscopy studies, and evidence suggests thermal liberation of hydrogen from grain boundary regions allows oxidation of crystallite surfaces during annealing. We tentatively attribute the 0.7 eV PL in nc-Si:H to deep donor defect states related to oxygen precipitates, and argue for the possible involvement of dislocations inside of crystallites to accompany these precipitates.
Assignment of High Wave-number Absorption and Raman Scattering Peaks in Microcrystalline Silicon
Authors: Johnson Erik V. , Kroely Laurent , Roca i Cabarrocas Pere 
Published: August 2010

AbstractIn the optimization of high-growth rate hydrogenated microcrystalline silicon (μc-Si:H) for photovoltaics, the observation of the infrared (IR) absorption peaks around 2000 cm-1 - which originate from silicon hydrogen (Si-HX) bonds in the film bulk - can provide useful information about the properties of the film. If the films are deposited on IR transparent substrates, Fourier Transform infrared (FTIR) spectroscopy is the most commonly used technique to measure the absorption in this regime. The rich spectrum of Si-HX peaks that can be observed in this wavenumber region describes the distribution of the bonded hydrogen amongst the various possible SiHX configurations, and as well, the presence of a pair of narrow, twin peaks at 2085 and 2100 cm-1 is indicative of material that is porous and prone to oxidation upon exposure to air. Many of these high wavenumber peaks are also observable using Raman scattering spectroscopy, allowing one to observe films on substrates that are not IR transparent. As well, the different absorption/scattering cross sections of the two techniques provide a useful tool to understand the origins of the various peaks, and in particular, those of the twin narrow peaks. In this work, we examine the dynamics upon exposure to atmosphere of these twin peaks in μc-Si:H grown by Matrix Distributed Electron Cyclotron Resonance (MD-ECR) PECVD. This deposition technique is an extremely promising one for growing μc-Si:H thin films at high deposition rates, and has demonstrated μc-Si:H film deposition at up to 28Å/s. By using both FTIR and Raman spectroscopy to characterize these films, we examine the differences in the dynamics of each of the twin peaks according to the technique used. In addition, secondary ion mass spectrometry (SIMS) measurements on the films show the physical distribution of oxygen in the films after five months of air exposure, and XRD measurements correlate the presence of these twin peaks with a [111] preferential surface orientation. Using these observations, we assign these absorption and scattering features to specific configurations of Si-HX within the film, and explain both the dynamics of the peaks over time and the similarity of the peaks for a wide range of samples.
Standard Characterization of Multi-junction Thin-film Photovoltaic Modules: Spectral Mismatch Correction to Standard Test Conditions and Comparison with Outdoor Measurements
Authors: Pravettoni Mauro , Tzamalis Georgios , Anika Komlan , Polverini Davide , Müllejans Harald 
Published: August 2010

AbstractMulti-junction thin-film devices have emerged as very promising PV materials due to reduced cost, manufacturing ease, efficiency and long term performance. The consequent growing interest of the PV community has lead to the development of new methods for the correction of indoor measurements to standard test conditions (STC), as presented in this paper. The experimental setup for spectral response measurement of multi-junction large-area thin-film modules is presented. A method for reliable corrections of indoor current-voltage characterization to STC is presented: results are compared with outdoor measurements where irradiance conditions are close to standard ones, highlighting ongoing challenges in standard characterization of such devices.
Optimization of the a-SiC p-layer in a-Si:H-based n-i-p Photodiodes
Authors: Vygranenko Yuri , Sazonov Andrei , Heiler Gregory , Tredwell Timothy , Vieira Manuela , Nathan Arokia 
Published: August 2010

AbstractOur work is aimed at enhancing the external quantum efficiency (EQE) of n-i-p photodiodes by reducing the absorption losses in the p-layer and the recombination losses in the p-i interface. We have applied boron-doped and undoped hydrogenated amorphous silicon carbon alloy (a-SiC:H) grown in hydrogen-diluted, silane-methane plasma to both the p-layer and undoped buffer layer, thus tailoring the p-i interface. The current-voltage, capacitance-voltage, and spectral-response characteristics of fabricated photodiodes are correlated with the doping level, optical band gap, and deposition conditions for a-SiC:H layers. The optimized device exhibits a leakage current of about 110 pA/cm2 at the reverse bias of 5 V, and a peak value of 89% EQE at a wavelength of 530 nm. At shorter wavelengths, the EQE decreases down to 56% at a 400 nm wavelength. Calculations of transmission/reflection losses at the front of the photodiode show that observed short-wavelength sensitivity enhancement can be attributed to improved separation of electron-hole pairs in the p-layer depletion region.
Demultiplexer/Photodetector Integrated System Based on a-SiC:H Multilayered Structures
Authors: Louro Paula , Vieira Manuela , Vieira M. A. , Costa João , Fernandes Miguel , Barata Manuel 
Published: August 2010

AbstractIn this paper we present results on the use of multilayered a-SiC:H heterostructures as an integrated device for simultaneous wavelength-division demultiplexing and measurement of optical signals. These devices are useful in optical communications applications that use the wavelength division multiplexing technique to encode multiple signals into the same transmission medium.The device is composed of two stacked p-i-n photodiodes, both optimized for the selective collection of photo generated carriers. Band gap engineering was used to adjust the photogeneration and recombination rates profiles of the intrinsic absorber regions of each photodiode to short and long wavelength absorption and carrier collection in the visible spectrum. The generated photocurrent signal using different input optical channels was analyzed at reverse and forward bias and under steady state illumination. A demux algorithm based on the voltage controlled sensitivity of the device was proposed and tested. An electrical model of the WDM device is presented and supported by the solution of the respective circuit equations. Other possible applications of the device in optical communication systems are also proposed.
A Full p-Type Poly-Si TFT Shift Register for Active Matrix Displays
Authors: Jung Myoung-Hoon , Chung Hoon-Ju , Park Young-Ju , Kim Ohyun 
Published: August 2010

AbstractA new shift register using p-type poly-Si thin-film transistors (TFTs) for active matrix display is proposed. It utilizes only p-type TFTs to simplify the fabrication process, and provides time-shifted output signals with a voltage swing from VSS to VDD without signal-level loss. In the proposed shift register, output is structurally separated from carry and therefore has a high immunity to output signal distortion caused by output load capacitance. We also propose a new light emitting control method using this shift register for high image quality active-matrix organic light emitting diode (AMOLED) displays. The proposed shift register was verified by simulation and measurement.
Crystallization Kinetics in High-rate Electron Beam Evaporated Poly-Si Thin Film Solar Cells on ZnO:Al
Authors: Sontheimer Tobias , Becker Christiane , Klimm Carola , Gall Stefan , Rech Bernd 
Published: August 2010

AbstractThe microstructure and crystallization kinetics of electron beam evaporated Si on ZnO:Al coated glass for polycrystalline solar cells was studied by electron backscatter diffraction and optical microscopy at various deposition temperatures. A time dependent analysis of the dynamics of the crystallization allowed for the individual determination of growth and nucleation processes. The nucleation process of Si on ZnO:Al was found to be influenced by a variation of the deposition temperature of the amorphous Si in a critical temperature regime of 200 ˚C to 300 ˚C. The nucleation rate decreased significantly with decreasing deposition temperature, while the activation energy for nucleation increased from 2.9 eV at a deposition temperature of 300 ˚C to 5.1 eV at 200 ˚C, resulting in poly-Si which comprised grains with features sizes of several μm.
Study of Crystallinity in μc-Si:H Films Deposited by Cat-CVD for Thin Film Solar Cell Applications
Authors: Hsu Cheng-Hang , Hsu Yi-Peng , Yao Fang-Hong , Huang Yen-Tang , Tsai Chuang-Chuang , Zan Hsiao-Wen , Bi Chien-Chung , Lu Chun-Hsiung , Yeh Chih-Hung 
Published: August 2010

AbstractThe crystallinity of the hydrogenated microcrystalline silicon (μc-Si:H) film was known to influence the solar cell efficiency greatly. Also hydrogen was found to play a critical role in controlling the crystallinity. Instead of employing conventional plasma deposition techniques, this work focused on using catalytic chemical vapor deposition (Cat-CVD) to study the effect of hydrogen dilution and the filament-to-substrate distance on the crystallinity, deposition rate, microstructure factor and electrical property of the μc-Si:H film. We found that the substrate material and structure can affect the crystallinity of the μc-Si:H film and the incubation effect. Comparing bare glass, TCO-coated glass, a-Si:H-coated glass and μc-Si:H-coated glass, the microcrystalline phase grows the fastest onto μc-Si:H surface, but the slowest onto a-Si:H surface. Surprisingly, the template effect lasted for more than a thousand atomic layers of silicon.
Growth of Large Diameter 6H SI and 4H n+ SiC Single Crystals
Authors: Gupta Avinash , Wu Ping , Rengarajan Varatharajan , Xu Xueping , Yoganathan Murugesu , Martin Cristopher , Emorhokpor Ejiro , Souzis Andrew , Zwieback Ilya , Anderson Thomas 
Published: August 2010

AbstractSiC single crystals are grown at II-VI by the seeded sublimation technique. The process has been scaled up and optimized to support commercial production of high-quality 100 mm diameter, Semi-Insulating (SI) 6H substrates and 100 mm 4H n+ substrates. The growth process incorporates special elements aimed at achieving uniform sublimation of the source, steady growth rate, uniform doping and reduced presence of background impurities.Semi-insulating 6H substrates are produced using precise vanadium compensation. Vanadium doping is optimized to yield SI material with very high resistivity and low capacitance.Crystal quality of the substrates is evaluated using a wide variety of techniques. Specific defects, their interaction and evolution during growth are described with emphasis on micropipes and dislocations. The current quality of the 6H SI and 4H n+ crystals grown at II-VI is summarized.
Non-destructive Detection and Visualization of Extended Defects in 4H-SiC Epilayers
Authors: Feng Gan , Suda Jun , Kimoto Tsunenobu 
Published: August 2010

AbstractThe extended defects, such as dislocations and in-grown stacking faults (IGSFs), in 4H-SiC epilayers have been detected and visualized by a non-destructive method, the micro photoluminescence (μ-PL) intensity mapping method, at room temperature. The one-to-one correspondence between the extended defects and the μ-PL mapping contrast has been successfully obtained. A threading dislocation corresponds to a dark circle with the reduced intensity in the μ-PL mapping image performed at 390 nm, while a basal plane dislocation dissociates into a single Shockley SF during the measurements. Three kinds of IGSFs have been identified in the samples. Each kind of IGSF shows the distinct PL emission located at 460 nm, 480 nm, and 500 nm, respectively. The shapes and distributions of IGSFs have also been profiled by μ-PL intensity mapping.
Systematic first principles calculations of the effects of stacking faults defects on the 4H-SiC band structure
Authors: Camarda Massimo , delugas pietro , Canino Andrea , Severino Andrea , piluso nicolo , La Magna Antonino , La Via Francesco 
Published: August 2010

AbstractShockley-type Stacking faults (SSF) in hexagonal Silicon Carbide polytypes have received considerable attention in recent years since it has been found that these defects are responsible for the degradation of forward I-V characteristics in p-i-n diodes. In order to extend the knowledge on these kind of defects and theoretically support experimental findings (specifically, photoluminescence spectral analysis), we have determined the Kohn-Sham electronic band structures, along the closed path Γ-M-K-Γ, using density functional theory. We have also determined the energies of the SSFs with respect to the perfect crystal finding that the (35) and (44) SSFs have unexpectedly low formation energies, for this reason we could expect these two defects to be easily generated/expanded either during the growth or post-growth process steps.
Monolithic a-SiC:H Stack Architectures as Tunable Optical Filters for Spectral Analysis
Authors: Vieira Manuela , Louro Paula , Vieira M. A. , Costa João , Fernandes Miguel , Vygranenko Yury , Barata Manuel 
Published: August 2010

AbstractThe characteristics of a tunable wavelength filter in a-SiC:H multilayered stack p-i'i-n graded cells are studied both theoretically and experimentally. Three different architectures are tested for proper fine tuning of the spectral sensitivity. The simplest configuration is a two terminal p-i-n photodiode where the active intrinsic layer is a double layered a-SiC:H/a-Si:H thin film. In the others the active device consists of a p-i'(a-SiC:H)-n / p-i(a-Si:H)-n heterostructures where the doped layers can have high or low conductivities. The spectral analysis of the device is performed under different optical and electrical applied bias and frequencies. Results show that, depending on the architecture and time window used, the device acts as an optical filter, an amplifier or a multiplexer /demultiplexer for optical signal processing, wavelength conversion, signal demultiplexing, and pattern recognition. A theoretical analysis supported by numerical and electrical simulations is presented. The analysis uses simple phototransistor and photodiode equations to explain the response of the device under different optical signals, and to compare the generated photocurrent with the experimental data.
Pulse Performance and Reliability Analysis of a 1.0 cm24H-SiC GTO
Authors: O'Brien Heather , Ogunniyi Aderinto , Zhang Qingchun Jon , Agarwal Anant 
Published: August 2010

AbstractA 1.0 cm2silicon carbide Super-GTO was designed and fabricated for Army pulsed power applications. It is a milestone, being the first SiC Super-GTO of this size. The design is the culmination of several years of research into material improvement, termination and gate patterns, optimizing device size, and calibrating pulse performance. The SGTO's forward blocking voltage is 9.0 kV, and its on-state voltage is 2.9 V at turn-on. Six devices were evaluated for pulse capability in a high-energy RLC circuit that was designed to produce a 1-ms wide half-sine shaped pulse. The maximum safe operating current for each of the six Super-GTOs varied from 2.2 kA to 3.4 kA, with 13 V being the typical VAKat a current of 3.0 kA. Two of the GTOs were also tested for pulse reliability and repeatability. They were individually switched in the pulse circuit for >500 pulses at very low duty cycle. This study is base-level research on pulse capability of the newest generation of SiC Super-GTOs and as such strives to identify the defining characteristics of an optimal device as well as the predominant modes of device failure.
Passivation by N Implantation of the SiO2/SiC Acceptor Interface States: Impact on the Oxide Hole Traps and the Gate Oxide Reliability
Authors: Poggi Antonella , Moscatelli Francesco , Solmi Sandro , Nipoti Roberta 
Published: August 2010

AbstractThis study compares p-MOS capacitors fabricated on N+ implanted and on virgin 4H-SiC. The former sample have N at the SiO2/SiC interface, the latter have not. To investigate the presence of deep and shallow hole traps at the SiO2/SiC interface, high frequency and quasi-static capacitance voltage measurements under dark have been compared for bias sweeping from accumulation to depletion and from depletion to accumulation, the latter after white light illumination. The presence of N has an effect on the density of the shallow donor like traps but none effect on the deep ones. The positive charge trapped in the oxide and/or at the oxide interface after equivalent tunneling hole injection have been compared and are equivalent. Time dependent dielectric breakdown tests have been compared too. The oxide grown on N+implanted SiC broken at lower electric field.
Micromachining of thin 3C-SiC films for mechanical properties investigation
Authors: Michaud Jean-Francois , Jiao Sai , Bazin Anne-Elisabeth , Portail Marc , Chassagne Thierry , Zielinski Marcin , Alquier Daniel 
Published: August 2010

AbstractIn this work, the mechanical properties of cubic silicon carbide are explored through the analysis of the static and dynamic behavior of 3C-SiC cantilevers. The investigated structures were micro-machined using Inductively Coupled Plasma (ICP) etching of thin 3C-SiC films grown on silicon. The aim was to evaluate the influence of some basic parameters (film orientation, film thickness, defect density) on the mechanical properties of the material.X-Ray Diffraction was used to evaluate the crystalline quality of the epilayers. Scanning Electron Microscopy observations of static cantilever deflection highlight the major difference between the stress states of (100) and (111) oriented layers for which the intrinsic stresses are of opposite signs. The cantilever deflection is highly dependent on the film thickness, as stated for (100) oriented epilayers. The lowest deflection is obtained for the thickest layer. The Young's modulus of 3C-SiC is calculated from the resonance frequency of clamped-free cantilevers, measured by laser Doppler vibrometry. The relatively low and orientation independent value of Young's modulus (~350GPa) found on the samples is probably associated with the high defect density usually observed in very thin 3C-SiC films grown on Si.
CMP for Copper TSV Applications
Authors: Gage Max , Liu Feng , Xu Kun , Wang You , Wang Yuchun , Xia Sherry , Tu Wen-Chiang , Karuppiah Lakshmanan 
Published: August 2010

AbstractThrough-silicon via (TSV) 3-D packaging and integration present many new opportunities and challenges for metals CMP applications. For front-side TSV polishing, challenges include the removal of large amounts of copper overburden, dishing control during copper clearing steps, and removal of large amounts of barrier metal and dielectric layers while still maintaining control over topography and defectivity. Additionally, the choice of barrier material can have significant impact on polishing in terms of the mechanical reliability regarding adhesion between the barrier metal and underlying dielectric layers. This paper will address many of these challenges with an emphasis on innovative technologies for superior process and endpoint controls, such as real-time profile control for thick copper films up to 6μm or more in thickness and automatic endpoint controls for barrier removal and dielectric stopping. The paper will also discuss some salient challenges for back-side TSV polishing, including the handling and polishing of bonded wafer pairs and strategies to minimize handling and polishing damage to the potentially fragile thinned device wafer. Additionally, the development of slurries with highly tunable copper-to-dielectric selectivity will be critical for enabling a wide range of final topographies, depending on requirements for subsequent bonding steps.