Electrical, morphological and structural properties of RF magnetron sputtered Mo thin films for application in thin film photovoltaic solar cells

Molybdenum (Mo) thin films were deposited using radio frequency magnetron sputtering, for application as a metal back contact material in ‘‘substrate configuration’’ thin film solar cells. The variations of the electrical, morphological, and structural properties of the deposited films with sputtering pressure, sputtering power and post-deposition annealing were determined. The electrical conductivity of the Mo films was found to increase with decreasing sputtering pressure and increasing sputtering power. X-ray diffraction data showed that all the films had a (110) preferred orientation that became less pronounced at higher sputtering power while being relatively insensitive to process pressure. The lattice stress within the films changed from tensile to compressive with increasing sputtering power and the tensile stress increased with increasing sputtering pressure. The surface morphology of the films changed from pyramids to cigar-shaped grains for a sputtering power between 100 and 200 W, remaining largely unchanged at higher power. These grains were also observed to decrease in size with increasing sputtering pressure. Annealing the films was found to affect the resistivity and stress of the films. The resistivity increased due to the presence of residual oxygen and the stress changed from tensile to compressive. The annealing step was not found to affect the crystallisation and grain growth of the Mo films

Secondary crystalline phases identification in Cu2ZnSnSe4 thin films: contributions from Raman scattering and photoluminescence

In this work, we present the Raman peak positions of the quaternary pure selenide compound Cu2ZnSnSe4 (CZTSe) and related secondary phases that were grown and studied under the same conditions. A vast discussion about the position of the X-ray diffraction (XRD) reflections of these compounds is presented. It is known that by using XRD only, CZTSe can be identified but nothing can be said about the presence of some secondary phases. Thin films of CZTSe, Cu2SnSe3, ZnSe, SnSe, SnSe2, MoSe2 and a-Se were grown, which allowed their investigation by Raman spectroscopy (RS). Here we present all the Raman spectra of these phases and discuss the similarities with the spectra of CZTSe. The effective analysis depth for the common back-scattering geometry commonly used in RS measurements, as well as the laser penetration depth for photoluminescence (PL) were estimated for different wavelength values. The observed asymmetric PL band on a CZTSe film is compatible with the presence of CZTSe single-phase and is discussed in the scope of the fluctuating potentials’ model. The estimated bandgap energy is close to the values obtained from absorption measurements. In general, the phase identification of CZTSe benefits from the contributions of RS and PL along with the XRD discussion.info:eu-repo/semantics/publishedVersio

Electrochemical impedance studies of hybrids of perfluorosulfonic acid ionomer and silicon oxide by sol-gel reaction from solution

Hybrids of Nafion (R) and silica were prepared from solution, growing the inorganic phase by hydrolysis/condensation of alkoxy silanes. Using tetraethoxysilane (TEOS) as the inorganic precursor, transparent and rigid films were obtained. Substituting part of the TEOS (20 wt% substitution) by 1,1,3,3 tetramethyl-1,3-diethoxydisiloxane (TMDES) more flexible films were obtained. These films were translucent and showed a phase segregation which was clearly observed by transmission electron microscopy. The ionic conductivity of the hybrids was measured by electrochemical impedance spectroscopy using two stainless steel electrodes, a frequency range of 0.1 to 10(5) Hz, and temperatures from 25 to 100 degrees C. Samples were also characterized by modulated differential scanning calorimetry. (C) 1998 Elsevier Science S.A. All rights reserved.44541671394

SYNTHESIS AND CHARACTERIZATION OF A COMPOSITE CONTAINING POLY(3-METHYLTHIOPHENE) AND NITRILIC RUBBER

The electrochemical synthesis of a composite of poly(3-methylthiophene) and poly(acrylonitrile-co-butadiene), nitrilic rubber, is described. The effect of the synthesis conditions on the electrochemical properties of the material was studied by cyclic voltammetry and chronoamperometry. I. r. spectroscopy thermogravimetry, d.s.c., elemental analysis and scanning electron microscopy were used to characterize the inclusion of the conductive polymer in the rubber matrix. The data indicated a low miscibility between the composite components. Stress-strain measurements indicated a toughening of the composite material in relation to the pure rubber. The electrical conductivity of the composite is one order of magnitude lower than that of the pure polymer.33214611461

Hybrids of cellulose acetate and sol-gel silica: Morphology, thermomechanical properties, water permeability, and biodegradation evaluation

Hybrids based on cellulose acetate (CA) and SiO2 were prepared by hydrolysis of tetraethoxysilane (TEOS). More rigid films were obtained with an inorganic phase incorporation. The thermal stability of the hybrids was similar to pure CA. Composite membranes were prepared by casting of CA/TEOS mixtures onto a poly(vinylidene fluoride) support. The water permeation decreased with the incorporation of the inorganic phase. Hybrid membranes were able to retain solutes with a molar mass of congruent to 9000 g/mol ( congruent to98% retention). Hybrids were submitted to biodegradation tests. The presence of the inorganic phase did not inhibit the growth of Thricoderma harzianum fungi. (C) 2002 Wiley Periodicals, Inc.84122196220

Preparation and characterization of polymeric electrolytes constituted by poly(ethylene oxide), sol-gel silica and lithium perchlorate

Electrolytes made up of poly(ethylene oxide) (PEO), sol-gel silica and LiClO4 were prepared. Poly(ethylene oxide-g-dimethylsiloxane) (SEO) was used as a compatibilizer. Two groups of samples were investigated: in group A, the PEO content relative to the tetraethoxysilane, SEO and LiClO4 changed from 2.6 to 10 wt.%; in group B it varied from 35 to 69 wt.%. Electrolytes with conductivity in the range of 10(-6)-10(-4) S/cm (25 degreesC) were obtained. In group A, transparent gels, transparent and flexible films and white powders were obtained. Differential scanning calorimetry (DSC) and light microscopy showed that all these samples are amorphous. On the other hand, all samples of group B were translucent films, showing typical spherulites of the PEO crystalline fraction. In the DSC analysis, an endothermic peak near 70 degreesC, assigned to the PEO crystalline fraction melting, was observed. Most of the samples of both groups A and B were thermally stable up to 200 degreesC. (C) 2002 Published by Elsevier Science B.V.1474167115717

Sol-gel titanium dioxide thin films on platinum substrates: preparation and characterization

Titanium dioxide was prepared by hydrolysis and polycondensation of titanium tetraisopropoxide. TiO2 films were obtained by spin-coating platinum substrates with the precursor solution. Infrared reflection-absorption spectroscopy, Raman spectroscopy and X-ray diffractrometry showed that films prepared at 100 degreesC were amorphous, films dried at 400 and 600 degreesC were composed of anatase and those prepared at 800 degreesC were rutile. Independent of the drying temperature, field emission scanning electron microscopy of the electrode surface showed that films have a cracked morphology. Cyclic voltammetry carried out at different scan rates showed that in films dried from 100 to 600 degreesC, the mass transport occurs by a semi-infinite linear diffusion. For rutile, however, the cyclic voltammetry results were better fitted considering a linear peak current, I-p, dependence on scan rate, i.e., the mass transport can be characterized by a surface reaction where the diffusion occurs only on the electrode I film interface (thin layer diffusion). Films were also characterized by electrochemical impedance spectroscopy. For an ac frequency equal to 10,000 Hz, the flatband potentials shifted toward more positive potentials as the drying temperature increased. The S800 sample showed lower donor densities (1.2 x 10(18) cm(-3) at 10,000 Hz) compared with the other samples. The electrochemical behavior of the films was discussed in the light of structural differences. (C) 2003 Elsevier Science B.V. All rights reserved.544475

Infrared reflection-absorption characterization of TiO2 films on ITO: detection of LO modes

By exploiting the high reflectivity of ITO substrates in the infrared and the detection of longitudinal optical (LO) modes provided by oblique incidence of radiation (Berreman effect), we showed that reflection-absorption experiments in the MID-IR can be successfully performed when thin inorganic oxide films deposited on ITO are used as samples. The samples we used were TiO2 films deposited on ITO by a sol-gel method. After being annealed at different temperatures, the films presented different structures, which could be detected by the IR spectra. Cyclic voltammograms of the samples were also presented and correlated to the IR spectra. Since we expect that other inorganic oxides can yield similar results, this simple, non-destructive and inexpensive technique can be routinely used in an electrochemical laboratory. (C) 2002 Elsevier Science B.V. All rights reserved.4430130