bluuebunny/crossref_metadata_2025_split huggingface dataset:
Formation Chemistry of Polycrystalline Cu(InGa)Se2 Thin-Film Absorbers Prepared by Selenization of Cu-Ga/In Stacked Precursor Layers with H2Se Gas
Authors: Kushiya K. , Kuriyagawa S. , Kase T. , Sugiyama I. , Tachiyuki M. , Takeshita H. 
Published: April 2011

AbstractThe purpose of this study is to improve the reliability and reproducibility of our fabrication process for polycrystalline Cu(InGa)Se2 (CIGS) thin-film absorbers and to make a better absorber with higher efficiency. The current baseline process of selenization has been evaluated through the investigation of the formation chemistry of the device-quality CIGS thin-film absorbers with a graded band-gap structure. It has been verified that the current selenization process has been performed in a good balancing point with both Cu/III ratio and thickness of the precursor layer and the total amount of Se through H2Se gas incorporated from the surface during the selenization. A simplified model to explain the formation chemistry of the selenization in this study has been proposed.
Investigation of Electrochemical Processes for Synthesis and Removal of CuInSe2 Thin Films
Authors: Menezes Shalini 
Published: April 2011

AbstractElectrochemical deposition of CuInSe2 films has been explored as a low-cost alternative to vacuum deposition. A special feature of this approach is that each element or compound may be selectively deposited or dissolved at a specific potential. This approach could further provide an environmentally benign means to recycle CuInSe2 from spent or defective modules. The paper investigates the reaction mechanisms for co-deposition, as well as, removal of CuInSe2. Rotating ring-disk and photoelectrochemical methods probe the formation and dissolution of Se, Cu2Se, In2Se3 and CuInSe2 films and the corrosion of CuInSe2 single crystal. The results provide important insights into the multiple reaction paths leading to the electrosynthesis of CuInSe2 films and new directions for developing an electrochemical recycling scheme for CuInSe2 modules.
The Effects of Kcn Etching on Cu-Rich Epitaxial CuInSe2 Thin Films
Authors: Fons P. , Nikl S. , Yamada A. , Nishitanp M. , Wada T. , Kurafuji T. 
Published: April 2011

AbstractA series of Cu-rich CuInSe2 epitaxial thin films were grown by molecular beam epitaxy on GaAs(001) substrates from elemental sources at a growth temperature of 450 °C. All samples were grown with an excess of Cu. Electron microprobe analysis (EPMA) indicated a Cu/ In ratio of about 2.1–2.6 in the as-grown films. Additionally, the Se/ (In+Cu) ratio was observed to be ∼0.95 indicating that the films were slightly Se poor. These Cu-rich samples were etched in a KCN solution for periods ranging from 30 seconds to 3 minutes. EPMA measurements indicated that the bulk Cu/ In ratio was reduced to ∼0.92 in all films regardless of etching time. Atomic force microscopy (AFM) was used to characterize the topology of each sample before and after etching. These measurements indicated that the precipitates present on the as-grown films were removed and large nearly isotropic holes were etched into the sample to a depth of over 1000 Å even for etching times as short as 30 seconds. The samples were also evaluated both before and after etching using a Phillips MRD diffractometer with parallel beam optics and a 18,000 watt Cu rotating anode X-ray source in the chalcopyrite [001], [101], and [112] directions. A peak was observed at ∼15 degrees in the [001] scan after etching consistant with the presence of the ordered vacancy compound, CuIn3Se5. Additionally the integrated intensity ratios of the chalcopyrite (202) reflection to the chalcopyrite (101) reflection ∝(fCu-fIn)2 along the [101] direction indicated the presence of a near-surface region containing cation sublattice disorder that was subsequently removed by the etching process.
Defect Chalcopyrite Cu(In1-x, Gax)3Se5 Polycrystalline Thin-Film Materials
Authors: Contreras Miguel A. , Wiesner Holm , Matson Rick , Tuttle John , Ramanathan Kannan , Noufi Rommel 
Published: April 2011

AbstractThe defect chalcopyrite material CuIn3Se5 has been identified as playing an essential role in efficient photovoltaic action in CuInSe2-based devices; it has been reported to be of n-type conductivity, forming a p-n junction with its p-type counterpart CuInSe2. Because the most efficient cells consist of the Cu(In1-xGax)Se2 quaternary, knowledge of some physical properties of the Ga-containing defect chalcopyrite Cu(In1-xGax)3Se5 may help us better understand the junction phenomena in such devices.Polycrystalline Cu(Inl-xGax)3Se5 (with O<x<l) thin films have been grown on 7059 Coming glass, soda-lime silica glass, n-type (100)Si, and Mo-coated soda-lime glass by coevaporation from elemental sources. In general, optical data show direct optical bandgaps that range from 1.20 eV for x=0 to ∼1.85 eV for x=l (this represents ∼200 meV higher bandgaps than the Cu(In, Ga)Se2 counterparts). Micrographs of the thin films show a substantial change in morphology as the Ga content is increased—for identical conditions of growth rate and substrate temperature. X-ray diffraction patterns agree with previously publish data for the ternary case (x=0), where these materials have been referred to as ordered vacancy compounds. Pole figures confirm a high degree of texturing in the films and a change in preferred orientation as Ga content is increased.
Real Time Composition Monitoring Methods in Physical Vapor Deposition oF Cu(In, Ga)Se2 Thin Films
Authors: Negami Takayuki , Nishitani Mikihiko , Kohara Naoki , Hashimoto Yasuhiro , Wada Takahiro 
Published: April 2011

AbstractThree real-time composition monitoring methods in physical vapor deposition process of CIGS thin films were proposed. One is the detection of near infrared (NIR) transmittance through the CIGS films from the IR source such as a heater back side of the substrate. One is the detection of NIR reflectance of the incident light from the films. The other is the measurement of the substrate temperature during the preparation of the CIGS films. These methods utilize the difference of the carrier density between Cu-rich (∼ 1020/cm3) and (In+Ga)-rich ( > 1016/cm3) films. The NIR transmittance through and reflectance from the Cu-rich film decrease due to high free carrier absorption. The temperature of the Cu-rich films was lower than that of the (In+Ga)-rich ones under the constant heating power because the Cu-rich films have larger radiation in proportion to absorption. Therefore, the change of Cu/(In+Ga) ratios at stoichiometry can be monitored by the variation of the NIR transmittance, NIR reflectance or the film temperature in real time. These composition monitoring methods are very useful and easily applied to the physical vapor deposition process of the CIGS films for photovoltaic application. The solar cell with active area of about 0.5 cm2, fabricated by obtaining the CIGS film using the latter monitoring method, showed an efficiency of 17.0%.
Technological Development for Commercialization of Amorphous Silicon Based Multijunction Modules
Authors: Yang Liyou , Bennett M. , Chen L. , Jansen K. , Kessler J. , Li Y. , Newton J. , Rajan K. , Willing F. , Arya R. , Carlson D. , Solarex  
Published: April 2011

AbstractSome of the significant steps in technological development for large-scale commercialization of amorphous silicon (a-Si:H) based multijunction photovoltaic modules are presented. These developments are establishing a high quality baseline process for manufacturing large-area ( ∼ 8 ft2) a-Si:H/a-SiGe:H tandem junction modules with improved stabilized conversion efficiency, throughput, yield, and reduced materials usage.
Intermixing at the CdS/CdTe Interface and its Effect on Device Performance
Authors: Dhere R. G. , Albin D. S. , Rose D. H. , Asher S. E. , Jones K. M. , Al-Jassim M. M. , Moutinho H. R. , Sheldon P. 
Published: April 2011

AbstractA study of the CdS/CdTe interface was performed on glass/SnO2/CdS/CdTe device structures. CdS layers were deposited by chemical solution growth to a thickness of 80–100 nm, and CdTe was deposited by close-spaced sublimation at substrate temperatures of 500°, 550°, and 600°C. Post-deposition CdCl2 heat treatment was performed at 400°C. Samples were analyzed by optical spectroscopy, secondary ion mass spectrometry (SIMS), spectral response, and current-voltage measurements. SIMS analysis shows that the intermixing of CdS and CdTe is a function of substrate temperature and post-deposition CdCl2 heat treatment. The degree of intermixing increases with increases in substrate temperature and the intensity of CdCl2 heat treatment. Optical analysis and X-Ray diffraction data show that the phases of CdSxTe1-x are also a function of the same parameters. Formation of a Te-rich CdSxTe1-x alloy is favored for films deposited at higher substrate temperatures. Spectral response of the devices is affected by the degree of alloying at the interface. The degree of alloying is indicated by simultaneous changes in long wavelength response (due to the formation of lower bandgap intermixed CdSxTe1-x) and the short wavelength response (due to the change in CdS thickness). Device performance is heavily influenced by alloying at the interface. With optimized intermixing, improvements in Voc, and diode quality factors are observed in the resulting devices.
Properties of Pulsed Laser Deposited CdSxTe1-x Films on Glass
Authors: Compaan D. , Feng Z. , Contreras-Puente G. , Narayanswamy C. , Fischer A. 
Published: April 2011

AbstractInterdiffusion of sulfur and tellurium across the CdS/CdTe interface is fundamentally important in the operation of CdTe solar cells. However, the properties of the resulting alloy semiconductor, CdSxTe1-x, are not well understood. We have prepared films of this ternary material by pulsed excimer laser deposition (PLD) across the alloy range. These films were examined by x-ray diffraction, wavelength dispersive x-ray spectroscopy, optical absorption, and Raman scattering to determine the influence of sulfur content on the crystal structure, lattice constant, energy gap, and vibrational mode behavior.
Preparation and Properties of Transparent Conductors
Authors: Gordon Roy G. 
Published: April 2011

AbstractTransparent, electrically conductive films have been prepared from several different metal oxides, including those of tin, indium and zinc. Deposition methods for these materials are reviewed, and their properties summarized and compared. A figure of merit for a transparent conductor may be defined as the ratio of the electrical conductivity to the optical absorption coefficient of the film. The figure of merit for fluorine-doped zinc oxide is shown to be larger than that of other transparent conductors, such as boron-doped zinc oxide, fluorine-doped tin oxide, and tin-doped indium oxide. Physical, chemical and thermal durability, deposition temperature, and cost are other factors which may also influence the choice of material for a particular application.
Optical Indices of Pyrolytic Tin-Oxide Glass
Authors: Von Rottkay K. , Rubin M. 
Published: April 2011

AbstractSnO2:F is a widely used transparent conductor and commercially available in a multilayer structure as Tech glass. Current applications include photovoltaics, electrochromics and displays. Optical design of these and other applications requires knowledge of the optical constants, in some cases, over the whole solar spectrum. Various optical property measurements were performed including variable angle spectroscopic ellipsometry, and spectral transmittance and reflectance measurements. This material is deposited in several steps and has a fairly complex structure. The measured data were fit to models based on this structure to obtain the optical indices. Atomic force microscopy confirmed the optically modeled surface roughness.
The Growth of Surface Textured Aluminum Doped ZnO Films for a-Si Solar Cells by RF Magnetron Sputtering At Low Temperature
Authors: Selvan J. A. Anna , Keppner H. , Shah A. 
Published: April 2011

AbstractTransparent Conducting Oxide films are essential for all kind of thin film solar cells. Doped Zinc Oxide (ZnO) in particular has several advantages when compared to other TCOs. It is stable in a hydrogen plasma and it acts as a diffusion barrier with respect to impurities from the substrate. In this work results on textured ZnO films deposited by RF magnetron sputtering are presented. The dependence of the film properties on the RF power, the substrate temperature and the water-vapor partial pressure added to the argon atmosphere has been investigated. We have found that high quality textured aluminum doped ZnO (ZnO:AI) films can be grown at low temperatures (150 °C) using the sputtering technique. Textured surfaces show two types of surface morphology; columnar and granular, depending on the deposition conditions. The ZnO:AI films seem to undergo a structural transition from hexagonal (mostly columnar appearance) to cubic structure (mostly granular appearance).
Role Of Deep Level Trapping On Surface Photovoltage Of semiinsulating GaAs
Authors: Liu Qiang , Ruda Harry E. , Koutzarov Ivoil P. , Jedral Lech , Chen Genmao , Prasad Manoj 
Published: April 2011

AbstractDual beam (bias and probe) transient Surface Photovoltage (SPV) measurements were made on undoped Semi-Insulating (SI) GaAs over an extended temperature range. Above 270 K, SPV recovery transients following a bias pulse were shown to reflect near surface conductivity changes; these are in turn controlled by surface/interface state thermal emission. Owing to the absence of a strong surface electric field in this material, the emitted carriers are not immediately removed from the near surface region. The recapturing of the emitted carriers is shown to be responsible for non-exponential conductivity and reciprocal-SPV transients. This behavior is considered to be characteristic of relaxation-type semiconductors with near-surface ungated structures. Below 150 K, the photoinduced transition of EL2 from its ground to metastable state EL2& was shown to change the effective electron and hole mobilities and augment the SPV signals immediately following the bias pulse. Thermally induced EL2& recovery above 120 K decreases the SPV signal from its maximum. This decay transient was analyzed and the decay rate fitted to a single exponential. An activation energy of 0.32 eV and a pre-exponential constant of 1. 9× 1012 s−1 were obtained, and attributed to the thermal recovery rate for EL2&.
The Valence Band Tail Density of States and Bond Angle Distortion in a-SiNx: H Alloys
Authors: Budaguan B. G. , Aivazov A. A. , Stryahilev D. A 
Published: April 2011

AbstractFilms of a-SiNx:H with x = 0.0..0.62 were deposited by glow discharge decomposition of (10% SiH4+90%/H2 )+ NH3 mixture. The chemical bonding and composition of films were investigated with using of infrared spectroscopy. The deformation energy per Si atom connected to bond bending Vkθ was calculated from data of Raman scattering. Characteristic energy of valence band tail (VBT) states distribution, E0v, were determined fromrsubgap absorption spectra. The dependencies of E0v and Vkθ on film composition, x, were considered in order to estimate the influence of the bond angle disorder on the distribution of VBT states.The essential difference in behavior of E0v and Vkθ dependencies on x was found for Si-rich (x<0. 15) alloys. When Vkθ value increase with x, the E0v parameter stays almost constant; while at x>0. 15 the E0v increase with x as well as the VKO. It means that bond angle disorder in the bulk of the material contributes to VBT characteristic energy, but it is not the only source. Another factors as it was shown may be connected with valence states of Si atoms, localized near inner boundaries.
A Global Electricai-Optical Model of Thin Film Solar Cells on Textured Substrates
Authors: Chatterjee P. , Leblanc F. , Favre M. , Perrin J. 
Published: April 2011

AbstractIn order to simulate the performance of the present day state-of-the-art multijunction solar cells in its entirety, an integrated electrical-optical model has been developed. The one-dimensional ab initio electrical model for the analysis of the transport properties of such devices can handle a very general semiconductor device structure where the material properties vary with position and the gap state properties with position and energy. The original semi-empirical optical model used takes into account both specular interference effects, and diffused reflectances and transmittances due to interface roughness. The latter are derived from angular-resolved photometric measurements and used as input parameters to the numerical programme. Comparison of the illuminated current density-voltage (J-V) characteristics, calculated on the basis of (a) a simple exponential absorption law and (b) the optical model, reveals an increase of ˜1 mA cm−2 in the short-circuit current and ˜8% in the cell conversion efficiency for case (b). Also the long wavelength quantum efficiency (QE) shows a marked improvement, while the blue QE decreases since proper account is taken of the absorption in the transparent conducting oxide and reflection from the device. The combined model is being applied to simulate the characteristics of wideband-gap-emitter-layer solar cells deposited in a three chamber conventional glow discharge reactor onto (i) highly textured SnO2 and (ii) weakly textured indium tin oxide substrates. The cells have been characterised experimentally by J-V and QE measurements. Preliminary results indicate that the integrated model matches the experimental J-V and QE data with a more realistic set of material parameters as compared to case (a).
Numerical Simulation of Surface Diffusion Controlled Motion and Shape Change of Electromigration Voids
Authors: Kraft O. , Mockl U. E. , Arzt E. 
Published: April 2011

AbstractIn order to simulate void motion and shape change of electromigration voids a numerical model was developed in which electromigration-driven diffusion on the void surfaces is assumed to act as the primary transport mechanism. The simulation describes the motion and shape evolution of a "two-dimensional void" having a simple initial shape in an isotropic medium. The current density distribution in the vicinity of a void was calculated by the application of a finite element method. Subsequently, the void shape changes by surface diffusion were examined using a finite difference scheme which includes the influence of gradients in curvature along the void surface. The model has been extended to allow other diffusion pathways, such as grain boundaries. The often observed faceting of voids and the formation of slit-like voids are discussed on the basis of simulations in which anisotropic surface tension and anisotropic surface diffusivity were assumed.
A Molecular Dynamics Study of Cu Segregation to the Σ11 Grain Boundary In Al
Authors: Huang Hanchen , Rubia T. Diaz de la , Fluss M. J. 
Published: April 2011

AbstractWe present results of molecular dynamics (MD) simulation studies of Cu segregation to the Σ11 grain boundary (GB) in Al. The simulations were performed with Embedded Atom Method (EAM) potentials for Al and Al-Cu. The results predict that copper atoms tend to order along either side of the interface even at the pure symmetrical GB, forming alternating chains along the direction. The nucleation of the chains is driven by a change in the local atomic level stress induced by the pre-existing Cu atoms at the GB.
In Situ Study of Al2Cu Precipitate Evolution During Zlectromigration in Submicron Al Interconnects
Authors: Theiss Silva K. , Prybyla J. A. 
Published: April 2011

AbstractWe have studied the behavior of Al2Cu precipitates during electromigration in submicron runners using in situ plan view TEM. Al (0.5 wt. % Cu) runners of widths between 0.3 and 1.0 μ were stressed at temperatures between 200 and 275° C and a current density of 2×106A/cm2. A greater number of precipitates nucleate per unit length in narrower runners (0.3 and 0.5 μ wide) than in wider runners (0.8 and 1.0 μ wide), although their average size is smaller in the narrower runners. The distribution of precipitates along the length of the runners is skewed towards the anode ends. Their number decreases and the skewing of their distribution increases with increasing temperature and linewidth. Precipitates are three times more likely to be found “downstream” (with respect to the electron flow) of a polygranular region and “upstream” of a blocking grain than the reverse. After their initial nucleation and growth, precipitates either decline in size or continue to grow during electromigration stressing depending on their position in the line and on the local grain structure. Grain boundaries profoundly influence the speed and direction of growth; however, the direction of growth cannot be predicted based on grain boundary inclinations alone. Precipitates tend to stay in one place and grow (or shrink) rather than migrate, in contrast to the behavior of voids which tend to migrate at higher temperatures. When precipitate migration occurs, it is either in association with void migration or by the replacement of small Al grains. Small precipitates remain compact as voids pass over or under them.
Electromigration in Single-Crystal Aluminum Lines Pre-Damaged by Nanoindentation
Authors: Joo Young-Chang , Baker Shefford P. , Knaufß Michael P. , Arzt Eduard 
Published: April 2011

AbstractElectromigration tests have been performed on single-crystal Al lines which were predamaged by rows of submicrometer-depth indentations made using a nanoindentation device. Indentations were placed close to each other so that their plastic deformation zones overlapped. During subsequent electromigration testing at 280°C and I to 2 MA/cm2, no damage was observed in non-indented single-crystal lines, while the indented lines showed electromigrationinduced voids at the cathode-side ends of the indented areas, and hillocks at the anode-side ends. The voids grew and moved away from the indentations towards the cathode. Fhe electromigration damage morphology of the indented lines indicates that the mechanical damage generates a local fast diffusion path in the single-crystal lines, which is believed to be due to dislocation core diffusion. A minimum indentation row length was observed, below which no void formed. This electromigration behavior is found to be phenomenologically similar to that of polygranular clusters in near-bamboo lines.
Further Investigations of the Microstructural Mechanism of Electromigration Failure in Al-Cu Lines with Quasi-Bamboo Microstructures
Authors: Kang S. H. , Génin F. Y. , Kim C. , Morris J. W. 
Published: April 2011

AbstractThin-film Al-2Cu conducting lines with “quasi-bamboo” microstructures were investigated to understand the microstructural mechanism of electromigration failure. Both conventional test structures and electron-transparent lines fabricated on silicon nitride windows were utilized to identify the “weakest” polygranular segments. Even when the current density was reduced to 0.75 MA/cm2 and the segment length was on the order of a few microns, failure occurs at the upstream termination of the longest polygranular segment in the line, at a time that decreases exponentially with the segment length. There is no apparent “Blech length” in quasi-bamboo Al- Cu lines; the longest segments are the failure sites, and their lifetime decreases with segment length in a regular way, even when the longest segments are only a few microns in length. It follows (and is observed) that the time-to-failure distribution of a group of lines is fixed by the distribution of the longest polygranular segments within them. This distribution can be effectively controlled by post-pattern annealing, which can refine the quasi-bamboo structure so that the longest polygranular segments are short and the distribution of longest polygranular segment lengths is narrow. Consequently, post pattern annealing is a very effective method for improving reliability by increasing the time to first failure.