bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrical and Structural Characterization of the Interface of Wafer Bonded InP/Si
Authors: Morral A. Fontcuberta i , Zahler J. M. , Atwater Harry A. , Frank M. M. , Chabal Y. J. , Ahrenkiel P. , Wanlass M. 
Published: May 2017

AbstractA study of the interfacial properties of wafer bonded InP/Si is presented. The electrical properties are measured by bonding InP to Si with different doping concentrations and by measuring the current voltage characteristics of the bonded pairs. Two different kinds of structures are studied: 1) n+InP doped to 3×1018 cm-3 bonded with n+Si doped to 1×1019 cm-3, and 2) n+InP doped to 3×1018 cm-3 bonded with p-Si doped to 6×1014 cm-3. After a 350°C anneal, structure 1 shows low resistive ohmic behavior while structure 2 is rectifying due to its higher sensitivity to interfacial chemistry. Indeed, both the reverse and forward current are reduced by annealing in structure 2, suggesting the formation of an interfacial barrier during annealing. This hypothesis is supported by High Resolution Transmission Electron Microscopy combined with Fourier Transform Infrared Spectroscopy, which indicate the formation of an amorphous interfacial oxide from the reaction of adsorbed water trapped at the InP/Si interface.
Formation of CdxHg1-xTe Layers on CdTe after NP-Etching and HgTe-Graphite Pasting
Authors: Yan Yanfa , Jones K.M. , Wu X. , Al-Jassim M.M. 
Published: May 2017

AbstractWe report on our investigation of the microstructure and chemical composition at the CdTe/Te-rich interfaces generated by NP-etching polycrystalline and single-crystalline CdTe films and followed with HgTe-graphite pasting and thermal annealing. We find that after this process, a thin layer of CdxHg1-xTe forms between CdTe and Te-rich layers, giving a structure like CdTe/CdxHg1-xTe/Te. High-resolution electron microscopy reveals that the CdxHg1-xTe layer has an epitaxial relationship with the CdTe. No CdxHg1-xTe layer has been observed in bromine/methanol-etched samples or samples with intentionally deposited Te layers.
Chemical and Electronic Properties of Metal/Sb2Te3/CdTe Contacts for CdTe Thin Film Solar Cells Studied by Photoelectron Spectroscopy
Authors: Kraft D. , Späth B. , Thißen A. , Klein A. , Jaegermann W. 
Published: May 2017

AbstractFormation of low resistance back contacts in CdTe thin film solar cells has been a research issue for many years. Ohmic contacts to the absorber layer are typically prepared using the diffusion of dopant atoms from the back contact material into the CdTe forming a thin space charge layer that can be easily tunnelled. Stable CdTe solar cells with reasonable back contact characteristics have been prepared using metal/Sb2Te3 layer sequences. In this study the chemical and electronic properties of such layer systems have been investigated using photoelectron spectroscopy. The vacuum deposited Sb2Te3 layers do not react with the CdTe substrate. Band alignment does not indicate the formation of a good back contact. By subsequent deposition of metals a chemical reaction is induced forming metal-tellurides, a metal/Sb-alloy and elemental Sb. Although an Sb diffusion into the CdTe absorber is observed, no increase of p-doping in the surface region is evident.
Analysis of the ZnTe:Cu Contact on CdS/CdTe Solar Cells
Authors: Gessert T.A. , Romero M.J. , Dhere R.G. , Asher S.E. 
Published: May 2017

AbstractWe report on the recent use of cathodoluminescence (CL) to probe the depth-dependent changes in radiative recombination that occur in CdTe devices during ZnTe:Cu contacting procedures. These types of CL measurements may be useful to assist in linking impurity diffusion (e.g., Cu) from the contact with depth-dependent variation in electrical activation within the CdTe layer. Variable-energy CL suggests that diffusion from the ZnTe:Cu contact interface may assist in reducing effects of shallow donors in the CdTe bulk, and yield higher acceptor levels in the region near the contact. CL analysis near abrupt metal discontinuities provides estimates of diffusion lengths for carriers associated with both excitonic and donor-to-acceptor pair recombination. Finally, CL measurements at increasing excitation levels (i.e., increasing electron-beam current) provides estimates of the defect state density, as well as providing evidence that discrete multiple defect bands may exist in CdTe prior to contacting.
Cu K-edge XAFS in CdTe before and after treatment with CdCl2
Authors: Liu Xiangxin , Compaan Alvin D. , Leyarovska Nadia , Terry Jeff 
Published: May 2017

AbstractWe have used the fine structure in the Cu K-edge x-ray absorption spectrum to help elucidate the lattice location of Cu in polycrystalline, thin-film CdTe solar cells. In particular, we have studied how the typical CdCl2 vapor treatment in dry air changes the local environment of the Cu in CdTe. We find the Cu absorption spectrum to be similar to that of Cu2Te in the as-deposited CdTe film but to convert to a spectrum similar to Cu2O environment after the vapor CdCl2 treatment.
Magnetron Sputtering for Low-temperature Deposition of CdTe-based Photovoltaics
Authors: Compaan Alvin D. 
Published: May 2017

AbstractAlthough the deposition over large areas of polycrystalline thin-film semiconductors such as CdTe is possible by a variety of methods including close spaced sublimation, vapor transport deposition, physical vapor deposition, organometallic chemical vapor deposition, and electrodeposition, the use of a plasma-based method such as magnetron sputtering can have significant advantages. In this paper I review recent results from our group in the fabrication of CdS/CdTe cells using rf magnetron sputtering and discuss some of the advantages that appear possible from the use of sputtering methods in this class of materials. Some of these advantages are particularly relevant as the polycrystalline thin-film community address issues related to the challenges of fabricating high efficiency tandem cells with efficiencies over 25%. Recently we have achieved: improvements in sputtered cell performance with cells based on commercial SnO2:F as well as on substrates with our own sputtered ZnO:Al, progress in the use of reactive sputtering for the deposition of oxygen alloys of CdS and N-doped layers of ZnTe, and progress in the sputtering of wider and narrower bandgap alloys of CdTe with Zn, Mn, and Hg. Details of the sputtering process and some of the recent achievements are discussed below.
Characterization of Transparent and Conductive ZnO:Ga Thin Films Produced by Rf Sputtering at Room Temperature
Authors: Fortunato E. , Assunçāo V. , Marques A. , Ferreira I. , Águas H. , Pereira L. , Martins R. 
Published: May 2017

AbstractGallium-doped zinc oxide films were prepared by rf magnetron sputtering at room temperature as a function of the substrate-target distance. The best results were obtained for a distance of 10 cm, where a resistivity as low as 2.7×10-4 Ωcm, a Hall mobility of 18 cm2/Vs and a carrier concentration of 1.3×1021 cm-3 were achieved. The films are polycrystalline presenting a strong crystallographic c-axis orientation (002) perpendicular to the substrate. The films present an overall transmittance in the visible part of the spectra of about 85 %, in average. The low resistivity, accomplished with a high growth rate deposited at RT, enables the deposition of these films onto polymeric substrates for flexible applications.
Explanation of Light/Dark Superposition Failure in CIGS Solar Cells
Authors: Gloeckler Markus , Jenkins Caroline R. , Sites James R. 
Published: May 2017

AbstractCIGS solar cells in many cases show a failure of light/dark superposition of their current-voltage (J-V) curves. Such failure generally becomes more pronounced at lower temperatures. J-V measurements under red light may also show an additional distortion, known historically as the “red kink”. The proposed explanation is that a secondary barrier results from the conduction band offset between CIGS and the commonly employed CdS window layer. This barrier produces a second diode with the same polarity and in series with the primary photodiode. The secondary-diode barrier height is modified by photoinduced changes of trap occupancy in the CdS layer, hence creating a voltage shift between dark and light conditions. Numerical modeling of the proposed explanation, including a band offset consistent with experimental and theoretical values, gives a very good fit to measured light and dark J-V curves over a wide temperature range. It also predicts the observed difference between illuminated J-V curves with photon energy above the CdS band gap, and those with sub-band-gap illumination.
Vapor Transport Deposition and Characterization of Polycrystalline CdTe Solar Absorbers
Authors: Kestner James M. , McElvain Sarah , Wolden Colin A. , Kelly Stephen , Ohno Tim R. , Woods Lawrence M. , Ribelin Rosine 
Published: May 2017

AbstractVapor transport deposition is being developed for high-rate synthesis of CdTe thin films. Films have been deposited at rates in excess of 20 μm/min. Thegrowth ratedependenceon source temperature yielded an apparent activation energy of 42 kcal/mol, in good agreement with the theoretical value for CdTe sublimation (45.7 kcal/mol). For substrate temperatures greater than 400°C the rate limiting step was resublimation. This phenomenon had a dramatic influence on morphology, although x-ray diffraction of all films indicated a strong (111) orientation. A preliminary device optimization investigating the effect of CdTe deposition temperature, post-deposition CdCl2 anneal parameters, alternative back contacts, and high-resistance buffer layers yielded a best cell with efficiency of 9.8% (704 mV Voc, 21.0mA/cm2 Jsc, 66% FF).
A Barrier to Trap Filling in CuIn1-xGaxSe2
Authors: Young David L. , Ramanathan Kannan , Contreras Miguel , Abushama Jehad , Crandall Richard S. 
Published: May 2017

AbstractVoltage pulses of variable length were applied to CuIn1-xGaxSe2/CdS (0 < x < 1) junction solar cells. The resulting transient capacitance emission signal was recorded for several minutes. The amplitude of the capacitance emission signal increased linearly with the log of pulse time. These data do not follow the standard model for trap capture and emission of carriers. Instead they follow a simple electrostatic model based on electrostatic charging of traps.
Photoluminescence Fatigue in CdTe Photovoltaics
Authors: Shvydka Diana , Verzella C. , Karpov V. G. 
Published: May 2017

AbstractJunction photoluminescence intensity (PL) in polycrystalline CdTe/CdS solar cells gradually decreases over time, similar to the PL fatigue in chalcogenide glasses. We discriminate between the fatigue per se and concomitant short-time PL drop due to the laser heating. The fatigue is more profound at higher temperatures and laser beam powers and can be as large as 80 percent in two hours. We attribute the observed phenomenon to defect creation by the light-generated electrons and holes. The defects provide additional non-radiative recombination channels. Simultaneously, this negative feedback makes the defect-generation rate slowing down, so that the PL fatigue saturates.
Diffusion of Ga and In in Sequentially Prepared Cu(In, Ga)S2 Thin Films for Photovoltaic Applications
Authors: Neisser Axel , Klenk Reiner , Lux-Steiner Martha Ch. 
Published: May 2017

AbstractThis contribution investigates the diffusion of In and Ga in Cu(In1-xGax)S2 thin film absorbers for photovoltaic applications. Sequentially prepared Cu-rich CuGaS2/CuInS2thin film diffusion couples have been annealed at temperatures in the range of 500°C to 600°C. Annealed samples have been examined by XRD and SNMS depth profiling. It was found that despite significant interdiffusion of Ga and In the bilayer retains its two phase structure of two layers of almost homogeneous composition, where the composition of these layers depends on the annealing temperature. Furthermore the interdiffusion process is less effective if the binary copper-sulfide phase is removed before annealing. On the basis of a tentative two dimensional diffusion model, which includes rapid diffusion along path ways of high diffusivity, the Ga-depth distribution could be modeled by numerical fits of calculated XRD-spectra to the experimental data. CuS is proposed as a possible pathway for rapide In-Ga interdiffusion.
High-Quality Transparent Conducting Oxide Films Deposited by a Novel Ion Plating Technique
Authors: Sakemi T. , Shirakata S. , Iwata K. , Matsubara K. , Tampo H. , Fons P. , Niki S. , Awai K. , Yamamoto T. 
Published: May 2017

AbstractA novel ion plating technique that has the attributes of both superb controllability of the high density plasma used as well as ion beam shape has been developed and applied to the deposition of transparent conducting oxides. The advantages of this technique include reduced ion damage, scale-up capability, in-plane uniformity, the use of low growth temperatures and fast deposition rates suggesting that the technique is very promising for a variety of applications such as solar cells and organic device fabrication. Gallium doped zinc oxide films have been deposited on glass substrates at 200°C. Resistivities as low as ρ∼2.7×10-4 Ω-cm with high transparency have been demonstrated. In addition, this technique has been successfully applied to large area deposition such as 65 cm × 55 cm-sized glass substrates.
Real-Time Fault Diagnosis of Sensors for Fault-Tolerant Control of Thin-Film CIGS Photovoltaics Process
Authors: Joshi Bharat , Beck Markus E. , Britt Jeffrey S. , Chaffin Michael , Gomez Nicholas , Muha John , Simpson L.J. , Wiedeman Scott 
Published: May 2017

AbstractITN Energy Systems, Inc., (ITN) and Global Solar Energy, Inc., (GSE) have continued the advancement of copper indium gallium diselenide (CIGS) production technology through the development of a number of activities, including fault-tolerant control, in-situ sensors, and process improvements, with the goal of enabling uninterrupted continuous manufacturing of high quality CIGS materials that are very sensitive to processing conditions. In this paper real-time sensor fault detection and diagnosis strategies developed by ITN and GSE to enable fault-tolerant controllers for thin-film CIGS deposition process are presented. The results indicate that these strategies are very effective and they would play a major role in improving system reliability, thereby also improving yield, throughput, and efficiency. Sensing process reconfiguration methodologies that lead to fault-tolerant controllers also are briefly discussed.
Modeling of Flux Composition for Thermal CdCl2:O2 Annealing of Polycrystalline CdTe
Authors: Hiie Jaan , Valdna Vello , Taklaja Andres 
Published: May 2017

AbstractDifferential thermal analysis (DTA) measurements were carried out in order to investigate thermal properties of model flux compositions of CdTe-CdCl2 with CdTeO3, the last recognized as a main oxidation product of CdTe. The composition of the flux was chosen to obtain larger quantity of residual flux phases for analyses and the presence of solid CdTe phase (about 20 mol%) at the fusion temperature 520 °C in a vacuum-closed isothermal quartz ampoule. Quantity of CdTeO3 constituted 20 mol % of the whole sample mass. DTA curves taken in the 300-700°C interval reveal considerable lowering of melting and solidification temperatures for the flux with addition of CdTeO3. The fused batches were vacuum annealed at 470 °C in a long narrow quartz tube for separation and deposition of volatile components CdCl2 and Te at the room temperature part of the tube. After vacuum annealing the residual CdTe phase on the batch with tellurite was coated with transparent platelike crystals morphologically typical to the CdTeO3, while oxide-free batch had no alien phases. In the flux, CdCl2 has a role of catalytic agent forming low melting point composition with native oxides and CdTe. After processing, CdCl2 can be separated by vacuum annealing.
Effect of Growth Interruption on the Properties of GaInAsSb/AlGaAsSb/GaSb Heterostructures and the Performance of Thermophotovoltaic Devices
Authors: Wang C.A. , Shiau D.A. , Connors M.K. , Danielson L.R. , Nichols G. , Donetsky D. , Anikeev S. , Belenky G. 
Published: May 2017

AbstractThe effect of growth interruption on the properties of GaInAsSb/(Al)Ga(As)Sb heterostructures and on the performance of GaInAsSb/AlGaAsSb/GaSb thermophotovoltaic (TPV) devices grown by organometallic vapor phase epitaxy is reported. In-situ reflectance monitoring is shown to be sensitive for observation of surface degradation during growth interruption, and this data was correlated with materials characterization by high-resolution x-ray diffraction and 4K photoluminescence (PL). Minority-carrier lifetime by time-resolved PL was used to determine interfacial recombination velocity of GaInAsSb/AlGaAsSb and GaInAsSb/GaSb double heterostructures grown with and without interruption, respectively. GaInAsSb/AlGaAsSb TPV devices grown without growth interruption have a slightly higher performance compared to those grown with interruption.
Electrodeposition of CIGS on Metal Substrates
Authors: Kampmann A. , Rechid J. , Raitzig A. , Wulff S. , Mihhailova M. , Thyen R. , Kalberlah K. 
Published: May 2017

AbstractThe development of a low cost roll-to-roll production process for CIGS remains an attractive goal. In the present approach, the absorber is prepared by electrodeposition techniques, while molybdenum, copper or stainless steel (SS) are used as flexible substrates. Two electrodeposition routes are evaluated: sequential plating of Cu, In and Ga followed by Se evaporation is compared to simultaneous (= ternary) electrodeposition of Cu, In and Se. Ternary electrodeposition yields 7.5 % efficiency on stainless steel. The sequential process leads to 9.0 % cell efficiency on copper and on stainless steel substrates.
Oxygenated CdS Window Layer for Sputtered CdS/CdTe Solar Cells
Authors: Gupta Akhlesh , Allada Karthikeya , Lee Sung Hyun , Compaan Alvin D. 
Published: May 2017

AbstractIt is known that carriers photogenerated in the polycrystalline CdS layer of a CdS/CdTe cell are not collected. Thus, the short-circuit current (JSC) of CdS/CdTe devices should be improved if the bandgap of CdS is increased to permit better blue response. Wu, et al, showed that alloying of CdS with oxygen can increase the absorption edge of the layer. We report here on studies of this ‘oxygenated’ CdS and its use in sputtered cells. We find that at a deposition temperature of 250°C the addition of O2 to the sputter gas results in a red shift of the absorption edge (from 2.35 eV to 1.94 eV), but that room temperature deposition gives a blue shift (from 2.36 eV to 3.28 eV). The Raman spectra of the room temperature deposited films show a considerable broadening of LO phonon peaks suggesting a micro- to nano- to amorphous transition as the O2 fraction increases. XRD measurements of these films confirm the formation of an amorphous structure at high O2 fractions. The quantum efficiency measurements of CdS/CdTe device with room temperature deposited oxy-CdS show an improvement in blue response and hence increased JSC, but are accompanied by poorer junction quality so that the overall efficiency is not increased.
Defects in Copper Indium Aluminum Diselenide Films and their Impact on Photovoltaic Device Performance
Authors: Heath Jennifer T. , Cohen J. David , Shafarman William N. 
Published: May 2017

AbstractThe electronic properties of polycrystalline CuIn1-xAlxSe2 (CIAS) films, which are incorporated as the absorber layer in photovoltaic devices, have been studied to better understand limitations on device performance. These studies have shown that compared to lower Al content films and to CuIn1-yGaySe2films, films with x ≥ 0.29 are relatively intrinsic, spatially nonuniform, and have broader bandtails characterized by much higher Urbach energies. This indicates that the CIAS films with x ≥ 0.29 are significantly more disordered than lower Al content CIAS or corresponding CIGS films, which likely negatively impacts the resulting photovoltaic device performance.
The Study of Deep Levels in CdS/CdTe Solar Cells Using Admittance Spectroscopy and its Modifications
Authors: Gilmore A.S. , Kaydanov V. , Ohno T.R. 
Published: May 2017

AbstractMeasurements of an admittance over a wide frequency range were used to detect the defect electronic states and evaluate their properties in CdTe based solar cells. Cells prepared in various ways, from various facilities all exhibited a high defect state density (>1014cm-3, and often >1015cm-3). Two distinct energy levels or bands were observed at approximately 0.37eV and 0.61eV above the valence band. These were tentatively attributed to CuCd- and VCd-- respectively. Various post-CdTe deposition treatments, as well as stress tests, were applied to alter the defect state densities. The high defect concentration measured was not observed to inhibit cell performance in any way.
Synthèse des études sur la compétence vectorielle en Europe : que savons-nous ? que reste-t-il à apprendre ?
Authors: Carpenter Simon 
Published: May 2017

The correct identification of all potential vectors of bluetongue virus (BTV) is crucial for the implementation of integrated control measures, disease risk analysis and management of this disease. The collection of Culicoides midges and virus isolation from the captured midges will give an indication of what Culicoides species may be involved in the transmission of the virus. The number of midges collected with light traps will give an indica­tion of the risk of the virus spreading in the area. Reliable detection of BTV from field-collected vectors is dif­ficult due to several constraints related to the vector itself and to laboratory procedures. A clear recommendation will be to maximise insect collections after viraemias are detected in mam­mals. Where possible, captured individuals should be identified to species level and populations’ age graded. Virus detection in the collected midges is conducted by using molecular tech­niques [e.g. polymerase chain reaction (PCR)], and virus isola­tion is performed using either embryonated chicken eggs or cell cultures. Positive results from either pools or individuals have different meanings in terms of vector competence and need to be evaluated with care. Individually analysed parous midges from which virus could be isolated indicate that the insect has fed on a viraemic host. It does, however, not show that the virus has replicated in the vector and that transmission could be related to that species. Current laboratory techniques for measuring vector competence have several drawbacks, e.g. low blood feeding rates (especially so for European Culicoides species), the small size of Culicoides species involved, and the limited availability of laboratory colo­nies of European Culicoides species. Some techniques, as for example multiplex PCR, have increased the number of sam­ples which can be processed in one day (up to 800 insects). A recent trial, with field-collected Culicoides fed and incubated in the laboratory, showed transmissible infection levels in C. scoticus for BTV-9 and 8 similar to that reported from the field. Future needs in this field are the evaluation of cell types, e.g. Culicoides cell lines for virus isolation, detection of the virus in the saliva of Culicoides, the development of a reference colony (i.e. C. sonorensis), the sequencing of its genome, as well as the standardisation of experimental procedures run across wide geographic areas.