bluuebunny/crossref_metadata_2025_split huggingface dataset:
Theoretical and Experimental Study of Shunt Effects in Thin-film Photovoltaics
Authors: Karpov V. G. , Rich G. , Rose D. H. , Subashiev A. V. , Dorer G. 
Published: April 2011

ABSTRACTWe present an analytical model that quantitatively describes the physics behind shunting in thin-film photovoltaics and predicts size-dependent effects in the I/V characteristics of solar cells. The model consists of an array of micro-diodes and shunt in parallel between the two electrodes, one of which mimics the TCO and has a finite resistance. We introduce the concept of the screening length L, over which the shunt affects the electrical potential of the system. The nature of this screening is that the system generates currents in response to the point perturbation caused by the shunt. L is expressed explicitly in terms of the system parameters. We find the spatial distribution of the electrical potential in the system and its I/V characteristics. The measured I/V characteristics depend on the relationship between the cell size l and L, being markedly different for the cases of small (l<<L) and large (l>>L) cells. This model is verified experimentally; good agreement is obtained.
A TEM Study of the Microstructure Evolution of Cu(In,Ga)Se2 Films from Cu-Rich to In-Rich
Authors: Yan Y. , Jones K.M. , AbuShama J. , Al-Jassim M.M. , Noufi R. 
Published: April 2011

ABSTRACTThe microstructure of Cu(In,Ga)Se2 (CIGS) films with compositions ranging from Cu-rich to In-rich was investigated by transmission electron microscopy (TEM) and energy-dispersive Xray spectroscopy (EDS). We found that the Cu-rich samples have larger grain sizes than the Inrich sample. In the Cu-rich samples, sub-interfaces were observed. The two sides of the subinterfaces were found to have different Cu concentration. In the In-rich sample, Ga inhomogeneity across grains was observed.
Interface Engineering of Chalcogenide Semiconductors in Thin Film Solar Cells: CdTe as an Example
Authors: Fritsche J. , Kraft D. , Thissen A. , Mayer Th. , Klein A. , Jaegermann W. 
Published: April 2011

ABSTRACTIn this paper the electronic properties of the different interfaces of CdTe thin film solar cells will be analysed by using a surface science approach. Experimental basis for the experiments is an integrated UHV systems which allows to prepare and analyse real solar cells as well as appropriate model interfaces. Recently obtained data on the ITO surface, the ITO/SnO2/CdS front contact, the CdS/CdTe heterojunction and the CdTe/Te back contact will be presented. In addition, bulk properties as doping and lateral inhomogeneities will be addressed. For all these interfaces experimentally determined band energy diagrams will be given and discussed in relation to solar cell performance. Finally, the sum of the results will be used to propose a modified band energy diagram of the complete CdTe thin film solar cell and its implication for further cell improvement will be presented.
Diffusion Behavior and Microstructural Properties of the CBD-ZnS/CIGS Interface Boundary
Authors: Nakada Tokio 
Published: April 2011

ABSTRACTThe diffusion behavior and microstructural properties of the CBD-ZnS/Cu(In,Ga)Se2 (CIGS) interface of high-efficiency Cd-free CIGS thin film solar cells with efficiencies exceeding 17 % have been investigated using energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). CBD-ZnS thin layers are found to grow with small polycrystalline grains that consist of sphalerite and wurtzite phases. This is in sharp contrast to CBD-CdS layers which grow epitaxially on CIGS grains. Micro-EDX analysis revealed Zn indiffusion into the CIGS thin layer a distance of approximately 40 nm from the CBD-ZnS/CIGS interface boundary after air-annealing at 200°C, whereas no diffusion of Zn was observed before annealing. These results suggest that the main role of the air-annealing process is not substitution of Se vacancies by oxygen atoms but the diffusion of Zn into CIGS which may result in the formation of a pn homojunction. On the other hand, negligible Zn-diffusion into a CuGaSe2 thin film was found at the CBD-ZnS/CuGaSe2 interface boundary even after air-annealing. The cell performance of CBD-ZnS/CIGS thin film solar cells is discussed in connection with the Ga/(In+Ga) atomic ratio, conduction band-offset and Zn-diffusion.
CuIn1−XGaXSe2-Based Photovoltaic Cells From Electrodeposited Precursor Films
Authors: Bhattacharya Raghu N. , Fernandez Arturo M. 
Published: April 2011

ABSTRACTWe have developed an electrodeposition bath based on a buffer solution so that the stability of the electrodeposition process is enhanced and no metal oxides or hydroxides precipitate out of solution. The buffer-solution-based bath also deposits more gallium in the precursor films. Asdeposited precursors are stoichiometric or slightly Cu-rich CuIn1−XGaXSe2 (CIGS). Only a minimal amount of indium was added to the electrodeposited precursor films by physical vapor deposition to obtain a 9.4%-efficient device.
Chemical Bath Deposition of Zinc Sulfide from Acidic Solutions
Authors: O'Hare Iain P. , Govender Kuvasani , O'Brien Paul , Smyth-Boyle David 
Published: April 2011

ABSTRACTAt present, the soft processing of materials attracts considerable interest. Chemical bath deposition (CBD) effects film formation by means of a controlled chemical reaction. Adherent, uniform and reproducible films of zinc sulfide (ZnS) have been deposited, upon low iron-content microscope slides, under acidic conditions, from a solution containing zinc chloride, urea and thioacetamide. Scanning electron micrographs of the deposited layers suggest that, as the reaction proceeds, uniform film growth is associated with increasing particle size, rather than continuous nucleation and deposition of new primary particles. Energy Dispersive Analysis by X-Rays (EDAX) spectra are typical of CBD-deposited films of ZnS; signals attributable to elements within the glass substrate are also detected, an observation consistent with the thin nature of the films. Grain size distributions have been investigated using computational image analysis, and an average increase in the diameter of the deposited particles of 33.7 nanometres per hour has been calculated.
Cadmium Telluride Solar Cells on Molybdenum Substrates
Authors: Matulionis Ilvydas , Han Sijin , Drayton Jennifer A. , Price Kent J. , Compaan Alvin D. 
Published: April 2011

ABSTRACTWe report on the development of Mo/CdTe/CdS/indium-tin-oxide, thin-film solar cells grown by radio-frequency magnetron sputtering. This is an inverted configuration compared to the conventional glass/tin-oxide/CdS/CdTe/metal cells. Molybdenum was chosen as a substrate because its thermal expansion coefficient and the work function are close to those of CdTe. We have achieved AM1.5 conversion efficiencies of 7.8 percent on 0.05 cm2 area devices. Our best cells had a nitrogen-doped ZnTe layer between the molybdenum and the CdTe for a somewhat improved back contact. However, we observe a significant rollover in the IV curve in forward current that indicates a back-diode effect. This implies the need for improvement of the electronic properties of the molybdenum - CdTe and possibly CdS - ITO interfaces.
CBD-In(OH)xSy Thin Films: An Approach to the Growth Mechanism
Authors: Bayón Rocío , Herrero José 
Published: April 2011

ABSTRACTThe surface morphology of chemical bath deposited In(OH)xSy thin films has been studied using SEM and TEM. Different surface morphologies have been obtained depending on the deposition conditions (reactant concentrations, pH and bath temperature) as a consequence of the variation of both the homogeneous nucleation and particle-growth rates with them. The In(OH)3 colloids present in the bulk solution and on the substrate surface play an important role in the growth mechanism since they promote the In(OH)xSy formation. It has been found that the growth mechanism of the films is the socalled particle-by-particle or colloidal growth.
Device Analysis of Cu(In,Ga)Se2Heterojunction Solar Cells - Some Open Questions
Authors: Rau U. , Weinert K. , Nguyen Q. , Mamor M. , Hanna G. , Jasenek A. , Schock H. W. 
Published: April 2011

ABSTRACTThe paper discusses the electronic properties of Cu(In,Ga)Se2–based heterojunction solar cells with a special focus on questions which at present are not satisfactorily understood. First, we discuss an apparent quantitative contradiction between measured concentrations of recombination centers in the Cu(In,Ga)Se2absorber material and the actual recombination rate in the solar cells. We propose, as a possible explanation for that observation, that the defect concentration in Cu(In,Ga)Se2is spatially inhomogeneous with a systematic increase towards the heterojunction interface. Second, we address the issue of electronic metastabilities in ZnO/CdS/Cu(In,Ga)Se2heterojunctions and, especially, in devices that use alternative buffer materials instead of CdS. Starting from a brief review of the experimentally observed types of metastabilities, we demonstrate by thermally stimulated capacitance measurements that a specific type of metastability that severely limits the performance of solar cells with non-CdS buffers is present also in high-efficiency standard devices though it has virtually no influence on the output parameters in the latter case. A possible explanation of this type of metastability points to a metastable defect reaction localized in the close to surface region of Cu(In,Ga)Se2. At the moment we cannot propose conclusive models for both open questions. However, we can localize the answers to both problems in the close-to-surface region of the Cu(In,Ga)Se2absorber.
Electrical Characteristics of TaOxNy/ZrSixOy Stack Gate Dielectric for MOS Device Applications
Authors: Jung Hyungsuk , Yang Hyundoek , Im Kiju , Hwang Hyunsang 
Published: April 2011

ABSTRACTThis letter describes a unique process for the preparation of high quality tantalum oxynitride (TaOxNy) with zirconium silicate (ZrSixOy) as an interfacial layer for use in gate dielectric applications. Compared with conventional native silicon oxide and oxynitride as an interfacial layer, tantalum oxynitride (TaOxNy) MOS capacitors using zirconium silicate (ZrSixOy) as an interfacial layer exhibit lower leakage current levels at the same equivalent oxide thickness. We were able to confirm TaOxNy/ZrSixOy stack structure by auger electron spectroscopy (AES) and transmission electron microscope (TEM) analysis. The estimated dielectric constant of TaOxNy and ZrSixOywere approximately 67 and 7, respectively. The zirconium silicate is a promising interfacial layer for future high-k gate dielectric applications.
Investigation on the Thermal and Electrical Properties of Ti-Si-O Film Formed by the Composite Sputtering Deposition
Authors: Nishiyama Akira , Kaneko Akio , Koyama Masato , Kamata Yoshiki , Fujiwara Ikuo , Koike Masahiro , Yoshiki Masahiko , Koike Mitsuo 
Published: April 2011

ABSTRACTTi-Si-O films were sputter deposited from TiO2+SiO2 composite targets with various SiO2 content. The phase separation occurred for every SiO2 content used in this experiment (from 14% to 75%) and it has been revealed that nanocrystalline (TiO2)1-x(SiO2)x films in which anatase TiO2 forms tiny grains were obtained when x in the film is larger than 0.26. The tiny grain was effective for suppressing the thermal grooving phenomenon of the thin films by the post deposition annealing which leads to the leakage current increase. The dielectric constant of the nanocrystalline film was varied with the SiO2 content from the value of the bulk anatase to SiO2.
A Comparative Study of Nickel Silicide Formation Using a Titanium Cap Layer and a Titanium Interlayer
Authors: Tan W.L. , Pey K. L. , Chooi Simon Y.M. , Ye J.H. 
Published: April 2011

ABSTRACTNiSi formation is known to be hindered by interfacial native oxide. Such oxide is easily formed on the Si surface through inefficient cleaning or a long time lag prior to Ni deposition. In this study, two methodologies were investigated to remove this layer of native oxide when no DHF clean was performed prior to metal deposition. Firstly, the deposition of a 100°C Ti cap layer after Ni deposition and secondly, the deposition of a middle 50Å Ti prior to Ni deposition. The samples were then rapid thermal annealed from 500 to 800°C. It was found for the Ti / Ni / SiO2 / Si stack, a layer of NiSi was formed starting from 600°C. Transformation to the NiSi2 phase begins at 750°C. As for the Ni / Ti / SiO2 / Si stack, a layer of NiSi was formed after 500°C annealing and conversion to NiSi2 also took place at 750°C. However, it was found that at low temperatures such as 500-600°C, facets of NiSi2 were identified under the thick NiSi layers, embedded in the Si substrate. Ternary phases like TixNiySiz were also identified at the surface of the sample.
Lack of hardening effect in TiN/NbN multilayers
Authors: Molina-Aldareguia Jon M. , Lloyd Stephen J. , Barber Zoe H. , Clegg William J. 
Published: April 2011

ABSTRACTThere is evidence indicating that multilayer films can be harder than monolithic ones. To investigate this, TiN/NbN multilayers with bilayer thicknesses ranging from 4 nm to 30 nm have been grown on MgO (001) single crystals using reactive magnetron sputtering. The sharpness of the interface and the composition modulation, which would be expected to strongly influence dislocation motion, have been studied by X-ray diffraction (XRD). These experiments show that the interfaces remain reasonably sharp (interface thickness ∼1 nm) and the composition modulation amplitude is maximum for multilayers with bilayer thicknesses greater than ∼10 nm. With thinner bilayers, the composition modulation decreases but the layered structure remains. Despite this, the nanoindentation hardness of the multilayers is between 20 and 25 GPa, which is similar to that of TiN and NbN alone, and therefore, no hardening due to the layering is observed. The deformation mechanisms observed under the indent in the TEM are consistent with these results.
Development of Cross-Hatch Morphology During Growth of Lattice Mismatched Layers
Authors: Andrews A. Maxwell , Speck J.S. , Romanov A.E. , Bobeth M. , Pompe W. 
Published: April 2011

ABSTRACTAn approach is developed for understanding the cross-hatch morphology in lattice mismatched heteroepitaxial film growth. It is demonstrated that both strain relaxation associated with misfit dislocation formation and subsequent step elimination (e.g. by step-flow growth) are responsible for the appearance of nanoscopic surface height undulations (0.1-10 nm) on a mesoscopic (∼100 nm) lateral scale. The results of Monte Carlo simulations for dislocation- assisted strain relaxation and subsequent film growth predict the development of cross-hatch patterns with a characteristic surface undulation magnitude ∼50 Å in an approximately 70% strain relaxed In0.25Ga0.75As layers. The model is supported by atomic force microscopy (AFM) observations of cross-hatch morphology in the same composition samples grown well beyond the critical thickness for misfit dislocation generation.
Anodic Bonding at Room Temperature
Authors: Baier Volker , Gebhardt Andreas , Barth Stefan 
Published: April 2011

ABSTRACTSpecial phosphate glasses (niobium-phosphate glasses) are used for anodic bonding experiments. They are optimized particularly with regard to elevated alkali ion conductivity at room temperature due to high contents of Li or Na ions. The compounds anodically bonded at room temperature show the strength of the breakage of the glass. Only a few seconds up to a few minutes at voltages of maximum 500 V are necessary for bonding. The glasses have a thermal expansion coefficient, which is not fitted to that of silicon. Therefore, stability of the bonded compounds is achieved only at temperature jumps up to 100 K in the case of bulk samples. For higher temperature jumps the probability of breakage increases continuously. It is possible to get thin films of these glasses with ac and dc magnetron sputter techniques for example on silicon. These thin layers are anodically bondable and the compounds with silicon show a higher temperature stability (at least 233 to 473 K).
Structured monocrystalline Si thin-film modules from layer-transfer using the porous Si (PSI) process
Authors: Richard Auer , Rolf Brendel 
Published: April 2011

ABSTRACTWe demonstrate a novel technique for fabricating monolithically series connected solar modules from surface structured thin monocrystalline Si films that we prepare by layer transfer using porous Si (PSI process). The novel series connection technique bases on reactive ion etching of the silicon film in a microwave plasma prior and after layer transfer. The module has an area of 25 cm2 and consists of 5 unit cells that have a film thickness of 16 µm. We measure an open-circuit voltage of 3028 mV and a confirmed efficiency of 9.9%. The Si film has a randomly textured surface for light trapping.
Ablation Lithography for TFT-LCD
Authors: Suzuki Kenkichi , Hayashi Nobuaki , Masuhara Hiroshi , Lippert Thomas K. 
Published: April 2011

AbstractAblation lithography is based on the photo-decomposition ablation of polymer materials by excimer laser. It is a self-development process, and accordingly possible to reduce the throughput time and manufacturing cost of TFT-LCD. The major alterations from the conventional photolithography are the resist material and the mask. Developing both the technologies and using an experimental exposure& aligner, we fabricated a TFT pattern on 300 × 400 mm2 glass substrate. The result proves the feasibility of EAL as an high throughput lithography suitable for a-Si TFT.
Low Temperature Process Technologies for the Next Generation High Performance Polycrystalline Silicon Thin-Film Transistors
Authors: Higashi Seiichiro , Abe Daisuke , Inoue Satoshi , Shimoda Tatsuya 
Published: April 2011

AbstractLow temperature process technologies for high performance polycrystalline silicon (poly-Si) thin-film transistors (TFTs) are discussed based on the investigations of pulsed laser crystallization, plasma treatment of poly-Si films, and SiO2/Si interface formation. Although highdensity (∼1018 cm−3) trap states localized at grain boundaries are introduced to the poly-Si films by laser crystallization, they are efficiently decreased to the order of 1016 cm−3 by following hydrogen plasma treatment. It is also shown that high quality SiO2/Si interfaces with the density of interface trap states (Dit) in the order of 1010 cm−2eV−1 are achieved using electron cyclotron resonance (ECR) plasma enhanced chemical vapor deposition (PECVD). By applying these low temperature process technologies to the fabrication process, high performance poly-Si TFTs with high n-channel mobility μn) of 187 cm2V−1s−1, low threshold voltage (Vth) of 1.97 V and small subthreshold swing (S) of 210 mV/dec. were obtained. These results indicate that the development of low temperature process technologies that can control trap states is the key to the next generation high performance poly-Si TFTs.
High Quality Growth of SiO2 at 80° C by Electron Cyclotron Resonance (ECR) for Thin Film Transistors
Authors: Rashid Riyaz , Flewitt A. J. , Grambole D. , Kreiβig U. , Robertson J. , Milne W. I. 
Published: April 2011

AbstractSilicon dioxide (SiO2) films have been deposited at 80°C in an Electron Cyclotron Resonance (ECR) plasma reactor from a gas phase combination of He, O2 and SiH4. The ECR configuration provides a highly ionised plasma (∼1016 m−3) with low ion energies (∼10eV) that gives efficient dehydrogenation of the growing material whilst minimizing defect creation. The physical characterisation of the material gives a refractive index of 1.46, an etch rate in buffered HF below 3 nm/s and a hydrogen content of less than 2 at.%. Electrical tests reveal a resistivity in excess of 1014Ωcm, an average breakdown strength of 5 MV/cm, and fixed charge and interface state densities of 1011 cm−2 and 1012 eV−1cm−2 respectively. This has been achieved using a O2:SiH4 flow ratio ≍ 2:1.
Preparation and Characterization of Low Temperature Silicon Dioxide Thin Films Using Tetramethylsilane (TMS) for Microfabrication Applications
Authors: Lin Xin , Fonash Stephen J. 
Published: April 2011

AbstractLow temperature silicon dioxide depositions have been carried out by plasma enhanced chemical vapor deposition (PECVD) using TMS as the Si precursor at 100-200°C at the pressure of 2-8 Torr. An RF power of 40 W and a TMS:O2 gas flow rate ratio of 1:500 without inert gas dilution were used in the depositions. It was found that the current-voltage (I-V) characteristics of as-deposited oxide films improved as the substrate temperature increased or deposition pressure decreased. Oxide films deposited at 2-3 Torr exhibited typical Fowler-Nordheim (F-N) tunneling characteristics and breakdown voltages greater than 8 MV/cm. The best capacitance-voltage (C-V) characteristics, giving a small flat band voltage shift, a small amount of positive oxide charge, a small hysteresis in bi-directional C-V sweep, and a low interface trap density, were obtained at 3 Torr. Post-deposition annealing in forming gas at the deposition temperature was performed and proved to be an effective approach for improving the electrical properties of the deposited oxide films without compromising the low temperature aspect of the process. By annealing at 200°C, the F-N tunneling barrier height increased by as much as 0.6 eV, the flat-band voltage and the hysteresis in C-V sweep were reduced by 0.74 V and 0.08 V, respectively. In addition, hydrogen was found to play a key role in the annealing treatment and its mechanisms were discussed.
Nano Crystalline Silicon Film Serves as the Emission Material for the Field Emission Pressure Sensor
Authors: Bo Liao 
Published: April 2011

AbstractThe prototype of a field-emission pressure sensor with a novel structure based on the quantum tunnel effect is designed and manufactured. Moreover the nano crystalline silicon film technology is introduced into the fabrication of the device effectively, which performs the function mostly as the field-emission material, the device field-emission characteristic of the nano silicon film is investigated, the experimental results show that the measured current density emitted from the effective area of the sensor can reach 53.5A/m2, when the exterior electric field is 5.6×105V/m.
Flat Panel Imagers Based on Excimer Laser Annealed, poly-Si Thin Film Transistor Technology
Authors: Lu J.P. , Schuylenbergh K. Van , Fulks R. T. , Ho J. , Wang Y. , Lau R. , Nylen P. , Mei P. , Mulato M. , Boyce J.B. , Street R.A. 
Published: April 2011

AbstractPulsed Excimer-Laser Annealing (ELA) has become an important technology to produce high performance, poly-Si Thin Film Transistors (TFTs) for large area electronics. The much-improved performance of these poly-Si TFTs over the conventional hydrogenated amorphous Si TFTs enables the possibility of building next generation flat panel imagers with higher-level integration and better noise performance. Both the on-glass integration of peripheral driver electronics to reduce the cost of interconnection and the integration of a pixel level amplifier to improve the noise performance of large area imagers have been demonstrated and are discussed in this paper.
Investigation of MgO and Mg1-xTixO thin Films by Electrostatic Spray Deposition Method for a Protective Layer of AC-Plasma Display Panel
Authors: Kim Soo Gil , Kim Young-Kee , Park Chung-Hoo , Kim Hyeong Joon 
Published: April 2011

AbstractMgO and Mg1-xTixO thin films were deposited by the electrostatic spray deposition method using Mg(tmhd)2 and Ti(OiPr)2(tmhd)2 as source materials and tetrahydrofuran and 1-octyl alcohol as solvents. The refractive index of the films shows a strong change from 1.73 for MgO to 2.39 for TiO2. The optical band gap energy values are 3.83 eV for TiO2 film and higher than 5.1 eV for films of Mg/(Mg+Ti) > 0.67. The discharge voltage and current increased with a content of Ti in Mg1-xTixO films. All these changes are closely associated with different Mg/(Mg+Ti) ratios of the films.