bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photovoltaics on Wire
Authors: Rojahn M. , Rakhlin M. , Schubert M. B. 
Published: April 2011

ABSTRACTThis contribution presents an approch to use wire-like substrates for thin-film devices. Based on plasma deposition processes for metals, hydrogenated amorphous silicon (a-Si:H) and transparent conductive oxides, solar cells are fabricated onto metal wires coated by a dielectric. Photolithography using a N2-laser and etching steps serve to pattern the thin film layers. Scanning electron microscope pictures and current-voltage characteristics of the device are demonstrated. Simple geometric simulations show the spectrally resolved intensity of the light that is scattered into the a-Si:H layers as a function of the diameter ratio of the substrate material and the deposited thin films. Finally, we discuss light concentrating and light trapping designs of sensors on transparent fibre substrates.
Vibrational Stretching Modes of the Si-H and Si-D Bonds in Amorphous Silicon Nitride
Authors: Lin Shu-Ya 
Published: April 2011

ABSTRACTThe vibrational density of states for the SiH(D) and SiH2(D2) groups in amorphous silicon nitride are calculated. The Si-H(D) bond-stretching modes of the SiH2(D2) groups are found to split, with the Si-D bond-stretching mode having larger splitting. The difference between the Si-D bond-stretching frequency of the SiD group and the Si-D asymmetrical stretching frequency of the SiD2 group has about the same value as that of the Si-H bonds. The differences in the effective masses of the Si-H and Si-D bonds and the degrees of the bond-stretching splitting of the SiH2 and SiD2 groups have compensating effects.
Orientation-Dependence of Low Temperature Epitaxial Silicon Growth
Authors: Wagner Thomas A. , Oberbeck Lars , Nerding Melanie , Strunk Horst P. , Bergmann Ralf B. 
Published: April 2011

ABSTRACTElectronic properties of thin epitaxial silicon films deposited at temperatures below 650°C by means of ion-assisted deposition strongly depend on substrate orientation as well as on deposition temperature: In (100)-oriented epitaxial films we find a low density of structural defects, and the minority carrier diffusion length is only limited by the presence of point defects or point defect complexes. These investigations also show an improvement of the electronic quality with increasing deposition temperature. Epitaxy on non-(100)-oriented substrates results in a significantly higher density of structural defects. The electronic properties of films deposited on stable flat surfaces, such as (111)- and (113)-oriented substrates are inferior as compared to (100)-oriented films, but are still superior to those of films deposited on faceted surfaces, as shown by light beam induced current and electron back-scattering diffraction measurements of polycrystalline thin films.
Effect of Experimental Noise on Recovery of the Electronic Density of States from Transient Photocurrent Data
Authors: Reynolds Steve , Main Charlie , Gueorguieva Mariana J. 
Published: April 2011

ABSTRACTThe effects of random noise on density of states determination from transient photocurrent data are examined by superimposing noise levels similar to those found experimentally (1% to 20%) on computer-simulated current-time data. Mathematically approximate methods based on Fourier and Laplace transformations are found to operate effectively at noise levels of up to 20%. Mathematically exact methods offer higher resolution, but this is compromised by greater susceptibility to noise. A Tikhonov regularisation method yields both high resolution and good noise tolerance.
Properties of silicon films deposited under argon dilution
Authors: Longeaud C. , Roy D. , Chaudhuri P. , Gupta N. Dutta , Ray P. Pratim , Vignoli S. , Meaudre R. , Meaudre M. , Saviot L. 
Published: April 2011

ABSTRACTFour series of samples, prepared at 250° C by decomposition of a mixture of silane and argon in a radio frequency powered deposition systems (rf-PECVD), have been studied. The dilution rates were 1 %, 1.5 %, 5 % and 10 % of silane in argon and the total pressure was 0.5 Torr for the first series and 0.2 Torr for the others. Structural and transport properties of the materials have been studied as function of power density. Structural studies show the transition from purely amorphous material towards microcrystalline material with increasing rf power density. The transport parameters were measured in the as-deposited, light-soaked and annealed states and compared to those obtained on state of the art material. The best material obtained is clearly device grade material. This study shows that argon dilution allows to tailor the material for a given application.
Structural and Optical Features of Nano-Crystalline Silicon Films Prepared by Pecvd and Rf Magnetron Sputter Techniques
Authors: Park M.-B. , Cho N.-H. 
Published: April 2011

ABSTRACTNano-crystalline Si films were prepared by plasma enhanced chemical vapor deposition (PECVD) and rf-magnetron sputter techniques at various deposition conditions, and the relations of the photoluminescence (PL) phenomena of the films with process variables are discussed. The phase of the films prepared at R.T. by PECVD techniques is somewhere between amorphous and crystalline states, consisting of nano-crystallites of size ranging from 3.2 to 5.3 nm. These films exhibit significant PL intensities near blue light region; the PL peaks shift from 510 to 460 nm with decreasing the reaction gas (SiH4) fraction from 4.7 to 2.0%. The films prepared at 500 °C by PECVD are composed of about 5 and 150 nm crystallites, exhibiting little PL phenomena. The PL intensity of the films prepared by sputter techniques was observed to increase with raising the sputter power and the post-deposition heat-treatment temperature.
Increasing The Dark Conductivity Activation Energy in Undoped Microcrystalline Silicon by Post-Growth Anneals
Authors: Yoon Jong-Hwan 
Published: April 2011

ABSTRACTUndoped µc-Si:H film of the strong n-type character with the dark conductivity activation energy of about 0.28 eV was annealed. Annealing was carried out by slowly increasing the temperature from 25 °C to 450 °C at a constant rate of 12 °C/min (one annealing cycle). Annealing effects were monitored by measuring the changes in dark conductivity, oxygen and hydrogen concentrations, and photoluminescence (PL). Dark conductivity activation energy gradually increases with increasing the number of annealing cycles to a saturation value of about 0.6 eV. There is little or no change in the oxygen concentration, but the hydrogen concentration decreases with increasing the number of annealing cycles. The PL band near 1.2 eV disappears with annealing, while the low energy PL band near 0.85 eV dominates rather as the number of annealing cycles increases. A possible explanation will be discussed.
Optical Simulations of the Effects of Transparent Conducting Oxide Interface Layers on Amorphous Silicon Solar Cell Performance
Authors: Ferreira Gelio M. , Ferlauto Andre S. , Rovira Pablo I. , Chen Chi , Nguyen Hien V. , Wronski Christopher R. , Collins Robert W. 
Published: April 2011

ABSTRACTSpectroscopic ellipsometry (SE) analysis of so-called “specular” (macroscopically smooth) and “textured” (macroscopically rough) thin film amorphous silicon (a-Si:H) based solar cell structures demonstrates the need to incorporate interface layers into the multilayer stack in order to simulate the observed Stokes vector of the specularly-reflected beam. In most cases, these layers can be attributed to microscopic roughness (e.g., at the SnO2/p-layer/i-layer interface in a-Si:H p-i-n solar cells), as verified by atomic force microscopy (AFM). In limited cases, the layers may include regions wherein chemical intermixing also occurs (e.g., at the ZnO/Ag interface in back-reflectors), particularly for overlying films prepared by sputtering. In spite of the clear evidence for the existence of interface layers, they have been neglected in previous simulations of the optical quantum efficiency (QE) of the solar cells. In this study, we incorporate the experimentally- observed characteristics of interface layers as input into optical models for the p-i-n solar cell structure. In this way, we demonstrate the beneficial effects of SnO2/p/i interface microroughness as an anti-reflector and the detrimental effects of the ZnO/Ag interlayer as a parasitic absorber.
Proton NMR and Magnetic Susceptibility in a-Si:H
Authors: Baugh Jonathan , Han Daxing , Kleinhammes Alfred , Wu Yue 
Published: April 2011

ABSTRACTProton nuclear magnetic resonance (NMR) is an important tool for characterizing the structure of a-Si:H over a wide range of length scales including short- and medium-range order as well as nanostructures. Some of the structural information obtained by NMR is based directly on proton NMR characteristics such as the lineshape and dipolar interactions that probe distances between hydrogen atoms and hydrogen environment. Based on such information it is shown that hydrogenated multi-vacancy model for Si-H clusters is fully consistent with both experimental and theoretical observations. It is demonstrated thatchanges of short- and medium-range order can be detected by measuring the magnetic susceptibility χ. Here ï is not directly related to NMR characteristics and NMR is used merely as a sensitive and accurate magnetometer. The result indicates that a-Si:H prepared by hot-wire CVD (HWCVD) and plasma-enhanced CVD (PECVD) with high H-dilution have higher structural order compared to conventional a-Si:H. By carrying out NMR measurements on single a-Si:H thin film new NMR features were observed such as the orientation dependence of the proton NMR spectrum with respect to the magnetic field. Based on such orientation dependence, strong evidence of aligned nano-channels was obtained in some device quality a-Si:H films.
The Properties of Low Hydrogen Silicon Thin Films Deposited by Mesh-type PECVD
Authors: Ryu Se-Won , Kwon Do-Hyun , Park Sung-Gye , Kim Hyoung-June 
Published: April 2011

ABSTRACTWe propose a mesh-type PECVD to minimize the hydrogen concentration in this study. Since in this system deposition rate is very slow, so for increasing a deposition rate, we suggest an applied DC bias enhanced sputtering process. We investigated several conditions to compare with conventional PECVD. Excimer-laser melting and regrowth of thin a-Si films is for fabricating polycrystalline-Si (poly-Si). Furthermore, we fabricate poly-Si thin-film transistor(TFTs) and measure threshold voltage (V), field-effect mobility (cm2 /Vs) and on/off current ratio
Thermal Annealing Study of Variable Band-Gap a-SiN:H Alloy Films
Authors: Banerji N. , Faro E. , Serra J. 
Published: April 2011

ABSTRACTA study of the effects of thermal annealing on the bond structure, optical properties, morphology and stoichiometry of variable band gap a-SixNyHz alloy films deposited by ArF LCVD has been made. These films were generated through two different photochemical pathways resulting from the use of either SiH4/NH3 or Si2H6/NH3 as precursor gases. Thermal annealing study of these films which span a wide compositional (0.22 < x/y < 1.44) and band-gap (Eg) range (1.7–5.2 eV) has led to the analysis of the stability of different bond configurations. We report here hydrogen bond stability and rearrangement of the near-neighbor environment of SiN bonds analyzed through FTIR, refractive index variations measured by ellipsometry and surface morphological changes observed through AFM during to the process of annealing. Results indicate that in the SiH4/NH3 deposited nitrogen-rich SiN:H films, SiHn bonds persist even upto 900°C and SiH bonds are less thermally stable than SiH2. Also, while the total bonded hydrogen decreases, the extent of SiN bond increases through a reaction mechanism involving: SiH + NH → SiN + H2. In the Si2H6/NH3 deposited silicon-rich film, whose initial spectra shows Si-H stretching and Si-H wagging bands, a rapid loss of Si-H bonds occurs at T ≤ 650°C. Based on the bond configurational interpretations of the Random bonding model proposed by Bustarret, we calculate the variations in film stoichiometry and density with the annealing temperature.
Physical Vapor Deposition of Cu(In,Ga)Se2Films for Industrial Application
Authors: Wada T. , Nishiwaki S. , Hashimoto Y. , Negami T. 
Published: April 2011

ABSTRACTCu(In,Ga)Se2 thin films were prepared by physical vapor deposition. The CIGS films were deposited by three kinds of method. The 1st was “2-stage process” in which (In,Ga)2Se3 precursor layer was deposited on Mo coated soda-lime glass at the 1st stage, and then exposed to Cu and Se fluxes to form CIGS films at the 2nd stage. The 2nd method was an ordinary “3-stage process”. The 3rd method was “2-stage deposition and post-annealing process” in which CIGS films were deposited at low substrate temperatures and then the obtained CIGS precursor films were annealed in Se flux at high temperatures. A solar cell using a CIGS film prepared at 400 °C by the “2-stage process” showed an efficiency of 11.8 % and that using a CIGS film deposited at 350 °C by the “3-stage process” showed an efficiency of 12.4 %. The CIGS films deposited by the “2-stage deposition and post-annealing process” have similar microstructures to the device quality CIGS films deposited by the “3-stage process” at high temperatures. The solar cell with an MgF2/ITO/ZnO/CdS/CIGS/Mo/glass structure showed an efficiency of 17.5 % (Voc=0.634 V, Jsc=36.4 mA/cm2, FF=0.756). The thin CIGS films with a smooth and flat surface can be fabricated by the “2-stage deposition and post-annealing process”. The solar cell using a 0.7μm CIGS absorber layer showed an efficiency of over 12 % and a large open circuit voltage of 0.677 V.
Next-Generation Transparent Conducting Oxides for Photovoltaic Cells: an Overview
Authors: Ginley David , Coutts Tim , Perkins John , Young David , Li Xiaonan , Parilla Phil 
Published: April 2011

ABSTRACTTransparent conducting oxides (TCOs) are becoming a more critical element in thin-film photovoltaic devices. In the continued drive to increase efficiency and stability while reducing cost and optimizing performance, the optical, electrical, and materials properties of TCOs gain increasing importance. TCOs can perform a variety of important functions, including contacts, antireflection coatings, and chemical barriers. In this paper, we will review some of the current advances in the field of transparent conductors and, where possible, will relate these advances to thin-film photovoltaic devices. Highlights will be on the rapidly growing collection of new n- and p-type materials; the implications of these materials on PV have not been fully assessed.
Structural and Optical Properties of Highly Efficient 2- μm Thick CdS/CdTe Thin Film Solar Cells
Authors: Nakamura K. , Gotoh M. , Fujihara T. , Toyama T. , Okamoto H. 
Published: April 2011

ABSTRACTThe structural and optical properties of CdS/CdTe(S) interface region of 2-μm thick CdS/CdTe solar cells have been studied in conjunction with photovoltaic performances of the solar cells. The properties are found to be crucially influenced by the annealing temperature and oxygen concentration of the CdCl2 treatment. An increase in VOC and F.F. found in the solar cells with the CdCl2 treatment at < 360°C is interpreted as due to suppression of interdiffusion of sulfur and tellurium at the CdS/CdTe(S) interface. On the other hand, the electromodulated photoluminescence with UV light excitation (UVE-EMPL) study reveals that the increasing VOC due to increasing oxygen concentration to 5% is likely to be caused by an increase in the built-in electric field in n+-CdTe1−xSx just adjacent to the CdS/CdTe(S) interface. As a result of the modification of the process parameters, we have achieved the conversion efficiency of 13.6% (VOC: 0.817V, JSC: 23.0 mA/cm2, F.F.: 0.725) using 2.3-μm thick PV active layer without anti-reflection coating.
Atomic Layer Deposition of Indium Sulfide Layers for Copper Indium Gallium Diselenide Solar Cells
Authors: Donsanti F. , Weinberger B. , Cowache P. , Bernard M. C. , Lincot D. 
Published: April 2011

ABSTRACTGrowth and properties of indium sulfide layers (< 300 nm) prepared by atomic layer deposition (ALD) have been studied. Growth rate of about 0.6 A per cycle has been measured for films deposited at 160°C from indium acetylacetonate and hydrogen sulfide precursors. The films are crystalline with the β modification. They possess high band gap values (2.7-2.8 eV) which are related to small grain sizes (3-4 nm) through quantum size effects. Electrical properties have been addressed using the semiconductor electrolyte junction. They are n type with a doping level around 1016 cm−3 and possess a good blocking behavior under reverse bias. The flat band potential is close to -1 V vs MSE. These figures are close to those measured under similar conditions with CdS CBD buffer layers and could explain the good cell performances obtained with ALD In2S3.
Comprehensive Study of Light-Soaking Effect in ZnO/Cu(InGa)Se2 Solar Cells with Zn-Based Buffer Layers
Authors: Chaisitsak Sutichai , Yamada Akira , Konagai Makoto 
Published: April 2011

ABSTRACTThe light-soaking effect in ZnO/ Cu(InGa)Se2 (CIGS) based solar cells has been studied. A CIGS thin film with Cu(InGa)(SeS)2 surface layer was obtained by selenization (H2Se)/sulfurization (H2S). A high resistively ZnO buffer layer deposited by the atomic layer deposition technique was used as a buffer layer. We found that the light-soaking effect mainly correlates with the properties of the CIGS surface, rather than with the properties of the ZnO buffer/window layer. This phenomenon can be eliminated by surface etching or doping CIGS surface with Zinc. Zinc diffusion using diethylzinc gas has been proposed in this work. To date, we have achieved efficiency of 13.9% (Voc: 560 mV, Jsc: 35.0 mA/cm2, FF: 0.71) without light soaking effect.
Preliminary First Principles Study Of Hf and Zr Aluminates as Replacement High-k Dielectrics
Authors: Haverty Michael , Kawamoto Atsushi , Jun Gyuchang , Cho Kyeongjae , Dutton Robert 
Published: April 2011

ABSTRACTBulk Density Functional Theory calculations were performed on Hf and Zr substitutions for Al in κ-alumina. The lowest energy configuration found was an octahedrally coordinated Zr site. Zr dissolution was favorable with an enthalpy of -2eV/unit cell for forming Al1.875Zr0.125O3 from pure Zr and κ-alumina. Hf and Zr substitution for Al atoms introduced empty d-states below the conduction band edge reducing the Eg of pure κ-alumina (7.5eV) to 6.4-5.9eV. The edge of the valence band however remained fixed by the O p-state character. The substitution of Hf and Zr into the alumina structure may lead to a higher dielectric constant, but will also reduce Eg and result in a trade off in tunneling currents in devices.
Electrical Performance and Scalability of Ni-monosilicide towards sub 0.13 μm Technologies
Authors: Lauwers Anne , de Potter Muriel , Lindsay Richard , Steegen An , Roelandts Nico , Loosen Fred , Vrancken Christa , Maex Karen 
Published: April 2011

ABSTRACTThe relationship between silicide thickness, sheet resistance and silicon consumption is experimentally checked for Co-disilicide and Ni-monosilicide. The reverse bias leakage current of shallow Ni-silicided and Co-silicided square diodes is compared for varying junction depth and varying silicide thickness. A lower reverse bias leakage current is obtained for a Ni-silicided shallow junction as compared to its Co-silicided counterpart. This can be attributed to the reduced silicon consumption. The Ti cap does not play an active role during the Ni-silicidation of narrow active area and poly lines. It is shown that a Ni-silicidation process is scalable without Ti cap.
Wafer Bonding between Magnetic Garnet and Lithium Niobate for Semi-Leaky Isolator
Authors: Yokoi Hideki , Mizumoto Tetsuya , Shimizu Masafumi 
Published: April 2011

ABSTRACTA semi-leaky isolator composed of a magneto-optic / anisotropic waveguide was fabricated by wafer bonding technique. Characteristics of the semi-leaky isolator were investigated. The magneto-optic / anisotropic waveguide exhibited the semi-leaky characteristics. The isolation ratio of 7.2 dB/cm was obtained at a wavelength of 1.55 μm.
Characterization of Low Temperature Polysilicon TFTs with Self-Aligned Graded LDD Structure
Authors: Lin Ching-Wei , Cheng Li-Jing , Lu Yin-Lung , Cheng Huang-Chung 
Published: April 2011

AbstractA simple process sequence for fabrication of low temperature polysilicon (LTPS) TFTs with self-aligned graded LDD structure was demonstrated. The graded LDD structure was self-aligned by side-etch of Al under the photo-resist followed by excimer laser irradiation for dopant activation and laterally diffusion. The graded LDD polysilicon TFTs were suitable for high-speed operation and active matrix switches applications because they possessed low-leakage-current characteristic without sacrificing driving capability significantly and increasing overlap capacitance. The leakage current of graded LDD polysilicon TFTs at Vd = 5V and Vg = −10V could attain to below 1pA/μm without any hygrogenation process, when proper LDD length and laser activation process were applied. The on/off current ratios of these devices were also above 108. Furthermore, due to graded dopant distribution in LDD regions, the drain electric field could be reduced further, and as a result, graded LDD polysilicon TFTs provided high reliability for high voltage operation.
Optically Assisted Metal-Induced Crystallization of Thin Si Films for Low-Cost Solar Cells
Authors: Chen Wei , Sopori Bhushan , Jones Kim , Reedy Robert , Ravindra N. M. , Aparacio Roger , Birkmire Robert , Morrison Scott , Madan Arun 
Published: April 2011

AbstractOptically assisted, metal induced crystallization (MIC) was used to convert amorphous Si films, deposited on Al coated glass substrates, into polycrystalline Si (pc-Si). The study investigated the effects of deposition temperature, process temperature, and film thickness on the grain orientation, grain size, and crystallization front of the processed films. Furthermore, we have attempted to examine the role of Al in MIC – in particular, whether the metal can be confined to the interface while grain enhancement occurs.
Thin Film Metal Oxide Semiconductors Deposited on Polymeric Substrates
Authors: Fortunato Elvira , Nunes Patrícia , Marques António , Costa Daniel , ÁGuas Hugo , Ferreira Isabel , Costa Maria E. V. , Martins Rodrigo 
Published: April 2011

AbstractHighly textured transparent conducting ZnO:Al thin films have been prepared by r.f. magnetron sputtering. The films were deposited on polyester (Mylar type D, 100 μm thickness) and glass substrates at room temperature. Surface stylus profiling, X-ray diffraction, scanning electron microscopy, transmission electron microscope and Hall effect measurements as a function of temperature, using the van der Pauw technique have characterized the films. The samples are polycrystalline with a hexagonal wurtzite structure and a strong crystallographic c-axis orientation (002) perpendicular to the substrate surface (columnar structure). The ZnO:Al thin films with a resistivity as low as 3.6×10−2 ωcm have been obtained, as deposited.