bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effects of Cu on Field Aided Lateral Crystallization (FALC) of Amorphous Silicon (a-Si) Films
Authors: Lee Jae-Bok , Kim Chul-Ho , Kwon Se-Youl , Choi Duck-Kyun 
Published: April 2011

ABSTRACTA novel concept of field aided lateral crystallization (FALC) and the effects of Cu on FALC of amorphous silicon (a-Si) were investigated. Cu was found to induce the lateral crystallization toward a metal-free region as well as the crystallization of a-Si in contact with Cu. In particular, the lateral crystallization caused by Cu was noticeably accelerated at the negative electrode side in every pattern with an aid of electric field, while it was retarded at the positive electrode side. The occurrence of Cu-FALC phenomenon was interpreted in terms of dominant diffusing species (DDS) in the reaction between metal and Si. The FALC velocity increased with the applied field intensity and the annealing temperature. The crystallization of a-Si was achieved at temperatures as low as 375°C when the annealing time increased in the presence of high electric field, above 30V/cm. Therefore, we could demonstrate the possibility of low temperature (<500°C) polycrystalline silicon (poly-Si) crystallization using Cu as a mediator in FALC technology.
Post-Deposition Sulfur Incorporation into CuInSe2 Thin Films
Authors: Titus Jochen , Schock Hans-Werner , Birkmire Robert W. , Shafarman William N. , Singh Udai P. 
Published: April 2011

ABSTRACTThe effect of initial film composition and substrate in the sulfurization of CuInSe2 was investigated. CuInSe2 films deposited on either soda-lime glass (SL) or Corning 7059® borosilicate glass (7059) substrates were reacted in flowing H2S for times from 1 to 8 hours. Films with Cu-rich composition, Cu/In > 1, reacted for 1 hour had nearly all the Se replaced by S. For Cu-poor films the incorporation of S was significantly reduced. In addition, in Cu-poor films on SL glass CuInS2 and NaInS2 were found at the film surface. These phases were not detected in films on 7059 substrates or in Cu-rich films. A phenomenological model is proposed to explain the formation of segregated surface phases in Cu-poor films on SL substrates.
Thermochemical and Kinetic Aspects of Cadmium Telluride Solar Cell Processing
Authors: McCandless Brian E. 
Published: April 2011

ABSTRACTA chemical and kinetic basis underlying processing strategies for thin film polycrystalline CdTe/CdS solar cell fabrication is presented. The processing conditions employed for moderate and high conversion efficiency CdTe/CdS solar cells fall within a consistent framework based on temperature and concentration of CdCl2 and O2 species during film deposition or thermal treatment. Detailed microstructural and compositional results are compared for thin-film CdTe/CdS structures with CdTe deposited by physical vapor deposition, electrodeposition and close-space sublimation. X-ray diffraction coupled with a model for diffusion of CdS into CdTe is used to determine the effect of treatment conditions on bulk and grain boundary diffusion coefficients. The effects of CdS diffusion, oxides, recrystallization and grain growth with respect to device efficiency, stability and process control over large area are discussed.
Molecular Level Approach for Low-Temperature Synthesis of CuInSe2 Films
Authors: Menezes Shalini 
Published: April 2011

ABSTRACTThis paper presents a new approach for relatively rapid and inexpensive synthesis of morphologically homogenous CuInSe2 absorber layers without high-temperature treatment. The approach, molecular layer electrodeposition, combines the low-cost, scale-up and environmental advantages of electrodeposition with the atomic level control of epitaxial deposition. This patented method entails building a superlattice of CuInSe2 monolayers by electro-deposition from a single electrolyte. The monolayer deposition approach extends the utility of epitaxial methods to device fabrication with simpler apparatus and practical deposition rates. The paper outlines the concepts underlying molecular layer electrodeposition, describes the special deposition apparatus and presents the results of initial investigations involving the synthesis of a ternary compound in a flow cell, controlled at molecular level.
Improvements in Non-vacuum Deposition of Particulate Materials
Authors: Eberspacher Chris , Pauls Karen , Serra Jack 
Published: April 2011

ABSTRACTOne of the most promising strategies for lowering the cost of photovoltaics (PV) is the use of thin-film technologies in which thin films are formed from particulate precursor materials deposited by non-vacuum techniques. The quality of particle-based PV thin films and in turn the sunlight-to-electricity conversion efficiencies and cost structures of devices based these films are strongly affected by the planarity and packing density of the layers of particles from which the films are formed and by the materials use efficiency of the processes used to deposit the layers. This paper reports progress made in depositing planar, well-packed layers of particles using non-vacuum spray deposition techniques.
Composition dependent doping and transport properties of CuGaSe2
Authors: Siebentritt Susanne , Gerhard Andreas , Brehme Stephan , Lux-Steiner Martha Ch. 
Published: April 2011

ABSTRACTChalcopyrites are doped by intrinsic defects, therefore their doping behavior depends on their composition. The doping and transport properties of epitaxial CuGaSe2 layers prepared under varying Cu excess have been investigated by temperature dependent Hall effect and conductivity measurements. Two acceptors, 134 meV and 80 meV deep, and a high degree of compensation, increasing with decreasing Cu excess, are found. The temperature dependence of the mobility indicates scattering with phonons, demonstrating high quality material. Defect scattering dominates at lower temperatures for CuGaSe2 grown under moderate Cu excess. CuGaSe2 grown under little or no Cu excess shows transport in a defect band at lower temperatures.
Preparation and Characterization of CdSxTe1−x Alloys and Films
Authors: Dhere R.G. , Albin D.S. , Asher S.E. , Moutinho H.R. , Compton D. , Gessert T.A. 
Published: April 2011

ABSTRACTIntermixing at the CdS/CdTe interface is considered crucial for the performance of CdTe-based solar cells. High-efficiency devices have been fabricated in spite of large lattice mismatch between CdS and CdTe. Intermixing and formation of CdSxTe1−x alloys in present-generation devices result from high-temperature CdTe deposition and post-deposition CdCl2 treatment. In this paper, we present our work on preparation of CdSxTe1−x-alloy powders and films. In this process, the CdS and CdTe powders are sized and mixed, isostatically pressed into a bar, sealed into closed-quartz ampoules, annealed at temperatures >1000°C, and water quenched. X-ray diffraction (XRD) analysis showed that they contained only distinct phases on S-rich and Te-rich sides of the phase diagram. Recently, two new batches of CdSxTe1−x material, produced by an improved process have been obtained (x =0.71 and x= 0.35 in CdSxTe1−x alloy). Initial XRD results from the films deposited by close spaced sublimation (CSS) using these powders reveal that both samples of bulk powders (prior to CSS deposition) are single-phase and demonstrate CdS-like characteristics (hexagonal). We have deposited CdSxTe1−x-alloy films using these powders. These alloy powders evaporate more congruently as opposed to mixed powders of CdS and CdTe. We will also present results on the structural properties of thin CdSxTe1−x alloy films deposited using these powders by CSS.
Characterization of the CuGaSe2/ZnSe Interface Using Kelvin Probe Force Microscopy
Authors: Sadewasser S. , Glatzel Th. , Rusu M. , Meeder A. , Fuertes Marrón D. , Jäger-Waldau A. , Lux-Steiner M.Ch. 
Published: April 2011

ABSTRACTTo improve the efficiency of heterostructure solar cells based on chalcopyrite semiconductors a good understanding of the interface properties is crucial. By Kelvin Probe Force Microscopy it is possible to obtain laterally resolved images of the work function of semiconductor surfaces in addition to the topographical information usually obtained by noncontact atomic force microscopy. We studied the CuGaSe2/ZnSe interface prepared by growth of CuGaSe2 onto the (110) face of freshly cleaved ZnSe single crystals using chemical vapor deposition. We observed different work function values for different crystal facets on single CuGaSe2 grains. From the obtained work function data and surface photovoltage measurements a schematic band diagram for the CuGaSe2/ZnSe heterostructure is proposed.
Properties of RF Sputtered ZnTe:N films for Back Contact to CdS/CdTe Solar Cells
Authors: Drayton Jennifer , Gupta A. , Makhratchev K. , Price K. J. , Bohn R. G. , Compaan A.D. 
Published: April 2011

ABSTRACTMost of the low resistance back contacts formed on high efficiency CdS/CdTe solar cells involve copper either in elemental form (such as Cu/Au back contacts) or as dopant in other material (such as Cu-doped ZnTe). But copper is also suspected to be a cause of degradation of devices in long-term stability tests due to its high diffusion coefficient in polycrystalline CdTe. In this paper, we present results on the development of nitrogen-doped ZnTe back contacts for CdS/CdTe solar cells. Reproducible N-doped p-ZnTe films were prepared using reactive RF magnetron sputtering with Ar/N2 gas mixtures. The conductivity of the doped ZnTe films was more than five orders of magnitude higher than that of intrinsic films. We find that annealing in air can further increase the conductivity. Efficiencies near 10% have been achieved with a ZnTe:N/Ni back contact.
Interface Investigation of ZnO/CdS/CuIn1−xGaxSe2/Mo Solar Cells
Authors: Hasoon F.S. , Al-Thani H.A. , Jones K.M. , Yan Y. , Moutinho H. R. , Young M. , Asher S. E. , Alleman J. , Bhattacharya R. , Ramanathan K. , Keane J. , Al-Jassim M.M. 
Published: April 2011

ABSTRACTGraded-band-gap CuIn1−xGaxSe2 (CIGS) absorbers with Ga/Ga+In value in the 20%-30% range have a demonstrated efficiency of 18.8%. For CdS-containing devices, the shortcircuit current density (Jsc) has almost reached its expected maximum. However, the open-circuit voltage of CIGS solar cells is limited by the surface microstructure and chemistry. In this work, we examine the microstructural properties and chemistry of CIGS. We also attempted to correlate the above observations and device performance.
Cu(In,Ga)Se2 Thin-Film Evolution During Growth from (In,Ga)2Se3 Precursors
Authors: AbuShama Jehad , Noufi Rommel , Yan Yanfa , Jones Kim , Keyes Brian , Dippo Pat , Romero Manuel , Al-Jassim Mowafak , Alleman Jeff , Williamson Don L. 
Published: April 2011

ABSTRACTWe examined the Cu(In,Ga)Se2 thin-film growth from (In,Ga)2Se3 precursors and found that the evolution of the microstructure and intrinsic native defects depends on the compositional changes that occur as the film transitions from being Cu rich to In(Ga) rich.
Characterization and Photoelectrochemistry of Layer-by-Layer Self Assembled Films of CdS Quantum Dots in Polyelectrolyte Matrix
Authors: Halaoui Lara. I. 
Published: April 2011

ABSTRACTPhotoelectrochemical studies of polyacrylate-capped CdS nanoparticles embedded in a polyelectrolyte matrix on electrode surfaces are presented. Multilayered films of polyacrylatecapped Q-CdS are assembled layer-by-layer on solid surfaces modified with a cationic polyelectrolyte, poly(diallyldimethylammonium chloride). The characterization of the layer-bylayer growth by means of UV-visible absorption, photoluminescence, FT-IR spectroscopy and ellipsometry measurements revealed the incorporation of the nanoparticles in the matrix and the reproducible surface-charge reversal taking place. In this paper, we present initial photocurrentvoltage studies of films thus formed, where the feasibility of charge conduction through the polyelectrolyte matrix and the dependence of photocurrent magnitude on the number of bilayers are demonstrated. In addition, the dependence of photocurrent direction on the electrode potential, and the observation of anodic photocurrent spikes attributed to surface states in the presence of dissolved oxygen are reported.
When, Why and Where are CdTe/CdS Solar Cells Stable?
Authors: Dobson K. D. , Visoly-Fisher Iris , Jayakrishnan R. , Gartsman K. , Hodes G. , Cahen David 
Published: April 2011

ABSTRACTThe role of Cu in CdTe/CdS solar cell instability remains the subject of much debate. The investigation of a range of ‘Cu’-contacted CdTe/CdS cells, which had received various thermal stress treatments, is described. Cells that were stressed in air exhibit strong current-voltage (I-V) rollover and junction degradation. No such degradation was observed for ‘Cu’-contacted cells that had been stressed in dry-N2 atmosphere. Cu is found to diffuse rapidly through the cell structure during back contact annealing and to accumulate in the CdS layer. With stress, significant levels of Cu dope the grain bulk, producing (with Cl) high resistance, photoconducting CdS. This behavior is independent of stress atmosphere and is, therefore, unlikely to (initially) be a dominating mechanism for cell degradation. Our results suggest simple air oxidation of the back contact interface to be a likely origin of I-V rollover in CdTe/CdS cells.
Ultra-Thin Zirconium Oxide Films Deposited by Rapid Thermal Chemical Vapor Deposition (RT-CVD) as Alternative Gate Dielectric
Authors: Chang Jane P. , Lin You-Sheng 
Published: April 2011

ABSTRACTZrO2 ([.kappa]∼ 18) was deposited on Si(100) wafers by rapid thermal chemical vapor deposition (RT-CVD) process to replace SiO2 as the gate dielectric material in metal-oxide- semiconductor devices for its high dielectric constant, good thermal stability on silicon, and large bandgap. The deposited films are nearly stoichiometric, amorphous, uniform, and highly smooth, as determined by X-ray photoemission spectroscopy, X-ray diffraction, ellipsometry, and atomic force microscopy. The high resolution transmission electron microscopy (TEM) image shows an interfacial ZrSiO4 layer between ZrO2 and the silicon substrate, and this interfacial layer is verified by thermodynamic calculations and etching resistance measured at the interface. Excellent step coverage was observed for depositing ZrO2 on nanometer scale features with an aspect ratio of 4. The dielectric constant of RTCVD ZrO2 was 15-18, with small C-V hysteresis and low leakage current.
Annealing Behaviour of WSix Films Prepared By CVD
Authors: Katiyar M. , Samal G. S. , Deepak R. K. Gupta , Sahoo P. K. , Kulkarni V. N. , Adetutu O. 
Published: April 2011

ABSTRACTTungsten silicide (WSix) films, deposited by chemical vapour deposition are normally amorphous in nature, and need to be annealed at high temperature to obtain low resistivity required for interconnections and metallization layers in VLSI circuits. In this paper, we focus on this annealing process for films deposited on Si and SiO2 substrate, and having Si/W ratio of 2.4. The characterization methods used were time-resolved X-ray diffraction, Resistivity measurement, and Rutherford backscattering spectroscopy analysis. We observe that 30 minutes is not sufficient for complete transformation of the WSi2.4 films on Si substrate. We also report on the dependence of annealing behaviour of nonstoichiometric WSixfilm on the substrate type.
A Study on Solid Phase Reactions of Ni and Pt on Si-Ge Alloys as Contacts to Ultra-Shallow P+N Junctions for CMOS Technology Nodes Beyond 70nm
Authors: Liu Jing , Mo Hongxiang , Ötürk Mehmet C. 
Published: April 2011

ABSTRACTRecently, selectively deposited SiGeB alloys have been proposed to form ultra-shallow source/drain junctions for 35-70 nm CMOS. The technology provides super-abrupt junctions with above equilibrium dopant activation at temperatures lower than 800°C. In addition to their low resistivities, the lower bandgap of SiGeB provides the potential advantage of reducing the Schottky barrier height and therefore, the junction contact resistance. This is a critical concern for future CMOS technology nodes since the contact resistance will dominate the MOSFET series resistance unless new technologies yielding contact resistivities near 10−8 ω−cm2 are developed. This paper examines the solid phase reactions of Ni and Pt with SiGeB alloys in order to form self-aligned low resistivity contacts. The results show that both Ni and Pt can form germanosilicides with low sheet resistances. Furthermore, both metals can form self-aligned contacts with a contact resistivity near 10−8 ω−cm2.
Mechanical behavior of thin Cu films studied by a four-point bending technique
Authors: Weihnacht Volker , Brückner Winfried 
Published: April 2011

ABSTRACTFour-point bending experiments in combination with thermal cycling of thin films on substrates were performed in a dedicated apparatus. Strains up to ±0.8% could be imposed into Cu films of 0.2, 0.5, and 1.0 μm thickness on Si substrates by bending the substrates at various temperatures in high vacuum. After relief of the bending, the residual stress was measured by the wafer-curvature method. At temperatures below 250°C, the yield behavior is asymmetric in tension and compression. The amount of plastic strain introduced by external bending increases with film thickness, but the absolute values of the introduced plastic strains are very low throughout. At higher temperatures, there is no clear thickness dependence and no asymmetry in tension and compression. The results are discussed in connection with the formation of misfit dislocations during plastic deformation of thin films.
Mechanism for the Reduction of Threading Dislocation Densities in Si0.82Ge0.18 Films on Silicon on Insulator Substrates
Authors: Rehder E.M. , Kuan T.S. , Kuech T.F. 
Published: April 2011

ABSTRACTWe have made an extensive study of Si0.82Ge0.18 film relaxation on silicon on insulator (SOI) substrates having a top Si layer 40, 70, 330nm, and 10[.proportional]m thick. SiGe films were deposited with a thickness up to 1.2[.proportional]m in an ultrahigh vacuum chemical vapor deposition system at 630°C. Following growth, films were characterized by X-ray diffraction and a dislocation revealing etch. The same level of relaxation is reached for each thickness of SiGe film independent of the substrate structure. Accompanying the film relaxation is the development of a tetragonal tensile strain in the thin Si layer of the SOI substrates. This strain reached 0.22% for the 1.2[.proportional]m film on the 40nm SOI and decreases with SOI thickness. The Si thickness of the SOI substrate also effected the threading dislocation density. For 85% relaxed films the density fell from 7×106 pits/cm2 on bulk Si to 103pits/cm2 for the 40, 70, and 330nm SOI substrates. The buried amorphous layer of the SOI substrate alters the dislocation dynamics by allowing dislocation core spreading or dislocation dissociation. The reduced strain field of these dislocations reduces dislocation interactions and the pinning that results. Without the dislocation pinning, the misfit dislocations can extend longer distances yielding a greatly reduced threading dislocation density.
Dislocation Core Spreading at Interfaces between Crystalline and Amorphous Solids
Authors: Gao Huajian , Zhang Lin , Baker Shefford P. 
Published: April 2011

ABSTRACTA fundamental question addressed here is concerned with the equilibrium structure of a dislocation core at an interface between a crystalline and an amorphous solid. This is motivated by experimental observations that the contrast of dislocations at an interface between a crystalline film and an amorphous substrate disappears under transmission electron microscopy. We have developed a mathematical moedl to describe the time-dependent behavior of dislocation core spreading as a function of the adhesive strength of the interface. The equilibrium core width and the rate of core spreading are determined in closed form solutions.
Dislocation Networks Strain Fields Induced By Si Wafer Bonding.
Authors: Eymery J. , Fournel F. , Rousseau K. , Buttard D. , Leroy F. , Rieutord F. , Rouvière J.L. 
Published: April 2011

ABSTRACTBuried dislocation superlattices are obtained by bonding ultra-thin single crystal Si (001) films on Si (001) wafers. The twist of two Si wafers induces a regular square grid of dissociated screw dislocations and the tilt a 1-D array of mixed dislocation. The Burgers vector is a/2 <110> for both types of dislocation. The atomic displacements and deformations of pure screw and edge dislocations are calculated with an isotropic elasticity approximation taking into account the free surface and the thickness of the upper crystal. It is shown by these calculations that the elastic strain field propagates up to the surface, and quantitative arguments are given to choose the network period / film thickness ratio.
Ge Layer Transfer To Si For Photovoltaic Applications
Authors: Zahler James M. , Ahn Chang-Geun , Zaghi Shahrooz , Atwater Harry A. , Chu Charles , Iles Peter 
Published: April 2011

ABSTRACTWe have successfully used hydrophobic direct wafer bonding along with hydrogen-induced layer splitting of germanium to transfer 700 nm thick, single-crystal germanium (100) films to silicon (100) substrates without using a metallic bonding layer. The metal-free nature of the bond makes the bonded wafers suitable for subsequent epitaxial growth of layered solar cells at high temperatures without concern about metal contamination of the device active region. Contact mode atomic force microscopy images of the transferred germanium surface generated by the formation of micro-bubbles and micro-cracks along the hydrogen-induced layer-splitting interface reveals minimum rms surface roughness of between 10 nm and 23 nm. Electrical measurements indicated ohmic I-V characteristics for germanium layers bonded to silicon substrates with ∼400 Ω cm−2 resistance at the interface. Triple-junction solar cell structures grown on these Ge/Si heterostructure templates by metal-organic chemical vapor deposition show comparable photoluminescence intensity and minority carrier lifetime to a control structure grown on bulk Ge. The use of a molecular beam epitaxy Ge buffer layer to smooth the cleaved surface of the Ge heterostructure has been shown to smooth the rms surface roughness from ∼11 nm to as low as 1.5 nm with a mesa-like morphology that has a top surface roughness of under 1.0 nm giving a promising surface for improved solar cell growth on solar cell structures.
Direct Bonding of Silicon Wafers with Simultaneous Dopant Diffusion
Authors: Grekhov Igor V. , Agrunova Tatiana S. , Kostina Lioudmila S. , Shmidt Natalia M. , Föll Helmut , Kostin Konstantin B. 
Published: April 2011

ABSTRACTBonding of silicon surfaces in aqueous solution of compounds containing III and IV impurities was performed for the first time. It was observed that the presence of aluminum at the bonding interface improved structural quality of the interface. This phenomenon is explained by the increase of the contact area due to Al-OH group sandwiched between the water molecules adsorbed at hydrophilic wafer surfaces at the first bonding stage. The incorporation of Al produces a p-type layer and the I/V characteristics of the resultant np+n diodes is shown not to be influenced by the presence of the bonding interface. The technique developed could be advantageous for the design of multi-layer large area semiconductor devices.