Influences of synthesizing temperatures on the properties of Cu2ZnSnS4 prepared by sol-gel spin-coated deposition

In this work Cu2ZnSnS4 (CZTS) suitable for the absorption layer in solar cells was successfully prepared by sol-gel spin-coated deposition. CZTS precursors were prepared by using solutions of copper (II) chloride, zinc (II) chloride, tin (IV) chloride, and thiourea. Texture structures with kesterite crystallinity reflected from the X-ray diffraction of (112), (200), and (312) planes of the CZTS were obtained as synthesized at a temperature of over 240 A degrees C. The absorption coefficients of the CZTS films are higher than 10(4) cm(-1), and the optical-energy gap is about 1.5 eV. Without sulfurization treatment, a near stoichiometry composition of the CZTS is obtained at a synthesizing temperature of 280 A degrees C

Bounded version vectors

Version vectors play a central role in update tracking under optimistic distributed systems, allowing the detection of obsolete or inconsistent versions of replicated data. Version vectors do not have a bounded representation; they are based on integer counters that grow indefinitely as updates occur. Existing approaches to this problem are scarce; the mechanisms proposed are either unbounded or operate only under specific settings. This paper examines version vectors as a mechanism for data causality tracking and clarifies their role with respect to vector clocks. Then, it introduces bounded stamps and proves them to be a correct alternative to integer counters in version vectors. The resulting mechanism, bounded version vectors, represents the first bounded solution to data causality tracking between replicas subject to local updates and pairwise symmetrical synchronization.FCT project POSI/ICHS/44304/2002, FCT under grant BSAB/390/2003

Surface Enhanced Raman Scattering of Light by ZnO Nanostructures

Raman scattering (including nonresonant, resonant, and surface enhanced scattering) of light by optical and surface phonons of ZnO nanocrystals and nanorods has been investigated. It has been found that the nonresonant and resonant Raman scattering spectra of the nanostructures exhibit typical vibrational modes, E-2(high) and A(1)(LO), respectively, which are allowed by the selection rules. The deposition of silver nanoclusters on the surface of nanostructures leads either to an abrupt increase in the intensity (by a factor of 10(3)) of Raman scattering of light by surface optical phonons or to the appearance of new surface modes, which indicates the observation of the phenomenon of surface enhanced Raman light scattering. It has been demonstrated that the frequencies of surface optical phonon modes of the studied nanostructures are in good agreement with the theoretical values obtained from calculations performed within the effective dielectric function model

A Study on the Hydrogen Evolving Activity of Electroplated Ni-P Coating by Using the Taguchi Method

The optimal catalytic activity of the electrodeposited Ni-P coating with the control of the process parameters was performed in this study by using Taguchi's method The controlled process parameters included current density, duty cycle and the concentration of the phosphorous acid in the electrolyte. The correlation among the controlled parameters and the resulted hydrogen evolution reaction (HER) activity was discussed with emphasis on the influence of the P content, internal stress, roughness and grain size of the coating. The optimal HER property was obtained for the electrodeposition of Ni-P coating with a phosphorous acid concentration of 5g/l, current density of 16A/dm(2) and duty cycle of 100 %. The resulted Ni-P coating with a better HER property was the one with P content 3at%, an internal stress higher than 10MPa, grain size 10 similar to 15nm and surface roughness higher than 100nm. In addition, the cracking of the coating due to high internal stress favored the raise of the HER activity

Simulation and Fabrication of Heterojunction Silicon Solar Cells from Numerical Computer and Hot-Wire CVD

In this paper, we will present a Pc1D numerical simulation for heterojunction (HJ) silicon solar cells, and discuss their possibilities and limitations. By means of modeling and numerical computer simulation, the influence of emitter-layer/intritisic-layer/crystalline-Si heterostructures with different thickness and crystallinity on the solar cell performance is investigated and compared with hot wire chemical vapor deposition (HWCVD) experimental results. A new technique for characterization of n-type microcrystalline silicon (n-mu c-Si)/intrinsic amorphous silicon (i-a-Si)/crystalline silicon (c-Si) heterojunction solar cells from Pc1D is developed. Results of numerical modeling as well as experimental data obtained using HWCVD on mu c-Si (n)/ a-Si (i)/c-Si (p) heterojunction are presented. This work improves the understanding of HJ solar cells to derive arguments for design optimization. Some simulated parameters of solar cells were obtained: tile best results for J(sc) = 39.4 mA/cm(2), V(oc) = 0.64V, FF = 83%, and n = 21% have been achieved. After optimizing the deposition parameters of the n-layer and the H(2) pretreatment of solar cell, the single-side HJ solar cells with J(sc) = 34.6 mA/cm(2) V(oc) = 0.615 V, FF = 71% and an efficiency of 15.2% have been achieved. The double-side HJ solar cell with J(sc) = 34.8 mA/cm(2) V(oc) = 0.645 V, FF = 73%, and an efficiency of 16.4% has been fabricated. Copyright (C) 2009 John Wiley & Sons, Ltd

Wear and Corrosion Investigation on the Electrodeposited Ni-P Coating

The wear and corrosion characteristics of an electrodeposited Ni-P coating were studied using a block-on-ring wear tester. The testing environments included dry wear and immersion wear in a 5 wt% NaCl water solution bath to simulate the corrosive atmosphere. The wear behavior is discussed in terms of the friction coefficient, wear rate, and surface roughness. Under boundary lubrication, the wear mechanism changed from both adhesive and abrasive wear for dry contact to mostly abrasive wear in corrosive salt water. The corrosion pits and corrosion film formed during accelerated corrosion wear testing not only lowered the friction coefficient but decreased the surface roughness. However, due to the accelerated pitting corrosion and removal of the corrosion film, the weight loss was slightly increased. Finally, the X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) analyses confirmed the formation of a porous corrosion film after the wear test in salt water

Effect of Crystalline Quality on Photovoltaic Performance for In0.17Ga0.83As Solar Cell Using X-Ray Reciprocal Space Mapping

This paper presents the In0.17Ga0.83As solar cell grown on misoriented GaAs substrate (2 degrees- and 15 degrees-off) by metalorganic chemical vapor deposition. The crystalline quality of the In0.17Ga0.83As solar cell is determined by X-Ray reciprocal space mapping (RSM). RSM results show that the crystalline quality of In0.17Ga0.83As solar cell grown on 2 degrees-off GaAs substrate is better than that of 15 degrees-off GaAs substrate. Moreover, the photovoltaic performance of In0.17Ga0.83As solar cell grown on 2 degrees-off GaAs substrate is found to be better than that of In0.17Ga0.83As solar cell grown on a 15 degrees-off GaAs substrate, because the InxGa1-xAs epilayer grown on 15 degrees-off GaAs substrate shows a large strain relaxation in the active layer of the solar cell. A large strain relaxation causes high dislocation density at the initial active layer/InxGa1-xAs graded layer interface for the solar cell grown on 15 degrees-off GaAs substrate. The effect of dislocation defects on the solar cell performance can be alleviated using the p-i-n structure as the epilayer grown on 15 degrees-off GaAs substrate

Transformation of microcrystalline silicon films by excimer-laser-induced crystallization

We describe the excimer-laser-induced crystallization of microcrystalline silicon films deposited by plasma-enhanced chemical vapor deposition (PECVD). Microcrystalline silicon films containing 2 at.% hydrogen can be used as precursor films for the laser recrystallization process without a dehydrogenation step, and provide a wider laser energy fluence process window than the previous explosive recrystallization for low temperature polysilicon (poly-Si) thin-film transistor (TFT) fabrication. Ellipsometry, transmission electron microscopy (TEM), and atomic force microscopy (AFM) are used to evaluate the laser irradiated films. Specially, we describe using atomic force microscopy to obtain plane-view grain microstructure images. (C) 2004 Elsevier B.V. All rights reserved

Wafer-bonded 850-nm vertical-cavity surface-emitting lasers on Si substrate with metal mirror

An 850-nm vertical-cavity surface-emitting laser (VCSEL) with a Au/AuBe/TaN/Ta/Si mirror substrate has been realized by low-temperature wafer bonding. It is found that the mirror substrate can be used as the bottom reflector to enhance the reflectivity of a bottom distributed Bragg reflector. The metal mirrors also served as the adhesive layers and ohmic contact layers to bond the Si substrate and the VCSEL epilayers. When the mirror-substrate-bonded VCSELs are excited by continuous-wave current at room temperature, they exhibit lower threshold cur-rent density and differential resistance (22 A/cm(2), 35 Ohm) as compared with the original VCSELs on GaAs substrates (77 A/cm(2), 60 Ohm). This feature is attributed to the finding that the Si substrate provides a good heat sink