The influence of annealing temperature on the structural, electrical and optical properties of ion beam sputtered CuInSe2 thin films

CuInSe₂ (CIS) thin films were prepared by ion beam sputtering deposition of copper layer, indium layer and selenium layer on BK7 glass substrates followed by annealing at different temperatures for 1 h in the same vacuum chamber. The influence of annealing temperature (100-400 °C) on the structural, optical and electrical properties of CIS thin films was investigated. X-ray diffraction (XRD) analysis revealed that CIS thin films exhibit chalcopyrite phase and preferential (112) orientation when the annealing temperature is over 300 °C. Both XRD and Raman show that the crystalline quality of CIS thin film and the grain size increase with increasing annealing temperature. The reduction of the stoichiometry deviation during the deposition of CIS thin films is achieved and the elemental composition of Cu, In and Se in the sample annealed at 400 °C is very near to the stoichiometric ratio of 1:1:2. This sample also has an optical energy band gap of about 1.05 eV, a high absorption coefficient of 10⁵ cm⁻¹ and a resistivity of about 0.01 Ω cm.     

Study of electrochemically grown copper indium diselenide (CIS) thin films for photovoltaic applications

CIS thin films have been grown electrochemically from an aqueous electrolyte at room temperature on fluorine doped tin oxide coated glass substrate at different deposition potentials ranging from ?0.7 to ?1.0 V versus Ag/AgCl reference electrode. Cyclic voltammetry was studied at slow scan rate to optimize the deposition potential. The thin film samples were selenized in a tubular furnace at 400 °C for 20 min. X-ray diffraction and Raman analysis was used to study the structural properties. Optical absorption, scanning electron microscopy and energy dispersive X-ray analysis (EDAX) have been used to investigate the band-gap, surface morphology and compositional analysis. Electrical properties were studied with the help of current–voltage measurements. Conductivity type for CIS thin films was studied by using photo-electrochemical study. The prominent reflections (112), (204/220) and (312/116) of tetragonal chalcopyrite CIS have been revealed for all as-grown and selenized samples. The energy band gap of the selenized CIS thin film deposited at various deposition potentials was found to be ~1.03 to 1.24 eV. Granular, uniform and void free surface was observed in as-prepared sample, while large clusters were noticed in selenized samples. EDAX results reveal that the stoichiometric CIS thin film are deposited ?0.8 V, however, Cu-rich and In-rich CIS layers were grown at lower and higher cathodic deposition potentials, deviated from ?0.8 V. The values ideality factor (η) calculated from I–V measurements were found to be decreased upon selenization. The Raman spectra of stoichiometric CIS thin film shows dominant A1 mode with spectral features sensitive to the microcrystalline quality of the layers. A ordered defect compound layer and secondary phases of CuSe are observed in In-rich and Cu-rich CIS layers, respectively.     

Influence of vacuum annealing on the properties of SILAR CuInS2 thin films and optimization of annealing duration

The structural, compositional, morphological and optical properties of as-deposited and vacuum annealed CuInS₂ thin films prepared by successive ionic layer adsorption and reaction method are studied by X-ray diffractometer, energy dispersive X-ray analyzer, scanning electron microscope and spectrophotometer respectively. The influence of vacuum annealing on the properties of CuInS₂ (CIS) thin films is discussed, annealing duration has also been optimized and reported in this paper.     

Synthesis and substructure of oriented CuInSe<Subscript>2</Subscript> films

The substructure, phase composition, and orientation of CuInSe₂ (CIS) films produced by consecutive deposition from two-component vapors (Cu-Se and then In-Se) were studied by transmission electron microscopy. The films were grown by thermal evaporation from separate elemental sources and by magnetron sputtering of compound targets. The results demonstrate that consecutive deposition on NaCl, fluorphlogopite, and Mo surfaces leads to the growth of Cu₂Se films in the first step of the process and CIS films in the second step. The epitaxial CIS films grown on (001) NaCl consist of grains in two orientations, with shear defects present in both types of grains. On (111) NaCl and (001) fluorphlogopite, epitaxial CIS films are obtained, which consist of blocks with identical orientations. It is shown that biaxially textured CIS films can be grown on trioriented Mo layers.Translated from Neorganicheskie Materialy, Vol. 41, No. 1, 2005, pp. 15–22.Original Russian Text Copyright © 2005 by Ievlev, Belonogov, Kharin.     

Fabrication and Properties of MgB2 Coated Superconducting Tapes

We present the formation of MgB₂ coatings by simple and novel aerosol deposition technique which has a potential to escalate towards the fabrication of long superconducting tapes. The thin MgB₂ coatings were produced by using pre-synthesized MgB₂ powder. The ability of this technique to form a precursor powder in a thin film form has greatly reduced the intricacies involved in the synthesis of MgB₂ by other techniques like hybrid physical chemical vapor deposition etc. The as-synthesized thin films were characterized by the x-ray diffraction technique to study the structural properties. The thin films were found to be x-ray amorphous in nature depicting the formation of frustrated structure which showed a superconducting transition onset at around 36 K.     

Optimization of growth conditions of ZnO nano thin films by chemical double dip technique

Abstract

Zinc oxide (ZnO) nano thin films have been deposited by the chemical double-dip technique using aqueous ZnSO₄ and NaOH solutions. The ZnO films were characterized in terms of surface morphology by x-ray diffraction, energy-dispersive x-ray analysis (EDX), the use of a scanning electron microscope (SEM) and atomic force microscope (AFM) for surface morphology. The films exhibited a smooth morphology. The chemical states of oxygen and zinc in the ZnO nano thin films were also investigated by x-ray photoelectron spectroscopy (XPS). In the present investigations, highly textured ZnO thin films with a preferential (002)-orientation were prepared on glass substrates. The deposition conditions were optimized to obtain device-quality films for practical applications.     

Low cost CuInSe2 thin films production by stacked elemental layers process for large area fabrication of solar cell application

Low cost deposition of large area CuInSe₂ (CIS) thin films have been grown on Mo-coated glass substrate by simple and economic stacked elemental layer deposition technique in vacuum. The grown parameters such as concentration of Cu, In and Se elements have been optimized to achieve uniform thin film in vacuum chamber. The as-grown Cu/In/Se stacked layers have been annealed at 200 °C and 350 °C for 1 h in air ambient. The as-grown and annealed films have been further subjected to characterization by X-ray diffraction (XRD), optical absorption, atomic force microscopy (AFM) and I-V measurement techniques. XRD patterns revealed that as-grown Cu/In/Se stacked layers represent amorphous nature while annealed CIS film reproduces nano-polycrystalline nature with chalcopyrite structure. The optical band gap of annealed films increases with respect to air annealing which confirms the reduction of crystallite size. Surface morphology of as-grown Cu/In/Se stacked layers and annealed CIS thin films have been confirmed by AFM images. The electrical measurements show enhancement of conductivity which is useful for solar cell application.     

Electrochemical synthesis and characterization of zinc selenide thin films

In this work, electrochemical deposition and characterization of zinc selenide (ZnSe) thin films is reported. ZnSe thin films were deposited onto tin oxide (SnO₂) coated conducting glass substrates from an aqueous solution bath containing ZnSO₄ and SeO₂. The effect of deposition parameters such as bath temperature, deposition time and electrolyte composition on the properties of the ZnSe films has been studied. Cyclic Voltammetric studies were carried out to optimize the deposition potential for the co-deposition of Zn and Se. Deposited ZnSe films have been characterized by X-ray diffraction (XRD), energy dispersive X-ray (EDX), scanning electron microscope (SEM) and optical techniques for their structural, compositional and optical properties and the results are discussed.     

Contribution study of properties of copper indium diselenide thin films

Stoichiometric powder of CuInSe₂ (CIS) was prepared from molten stoichiometric quantities of the elements. The structure analyzed by X-ray diffraction powder (XRD), shows mainly the chalcopyrite phase. CIS polycrystalline thin films deposited from this powder have been grown on glass substrates in vacuum by thermal evaporation method. The structural and electrical properties of both as-deposited and annealed films were studied using X-ray diffraction and dark conductivity measurements respectively. As-prepared films at room temperature showed an amorphous structure. However, the chalcopyrite structure with (112) preferential orientation was observed after annealing in vacuum at 400 °C during 30 min. The influence of the annealing process on the dark conductivity of the films was also discussed.     

Composition and Morphology of Electrodeposited CuInSe2 Precursor Films

CuInSe₂ (CIS) precursor films have been prepared by electrodeposition in aqueous solution. The electrodeposited films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) for structural, morphological and componential properties. The influence of deposition potential and Na-citrate concentration on composition and morphology of electrodeposited films was studied in detail. It is found that the film morphology is strongly influenced by deposition potential and Na-citrate concentration. Films with large and homogenous grain size and ratio of Cu/In approaching 1 were obtained at deposition potentials of -0.7 and -0.75 V vs the saturated calomel electrode (SCE) and Na-citrate concentration of 500 mmol/L. Chalcopyrite phase CuInSe₂ is contained in precursor films that have poor crystallinity.     

Raman spectroscopy of CuIn1 − xGaxSe2 for in-situ monitoring of the composition ratio

Metal organic vapor deposition (MOCVD) is a well known method for preparing high quality and large area CuIn_1 − xGa_xSe₂ (CIGS) absorber layers. Some in-situ non-contact monitoring systems are needed when CIGS absorber layers are manufactured in industry. In this study, CuInSe₂ (CIS) and CIGS thin films with different composition ratios, [Cu]/[In + Ga], were prepared by MOCVD using [Me₂In(μ-SeMe)]₂, hexafluoroacetylacetonate Cu(I) (3,3-dimethyl-1-butene), trimethyl gallium and dimethyle diselenide as the In-Se single source, Cu, Ga and Se precursors, respectively. The Raman shift spectra of the films with various composition ratios were analyzed to produce a basic algorithm that can determine the composition ratios of CIS and CIGS thin films indirectly.     

Enhanced Flux Pinning Properties of BaZrO3-doped YBCO Films Grown by Pulsed Laser Deposition on LaAlO3(100) Substrates Decorated with Y2O3 Nanoislands

In this work, we intend to investigate the interaction between two types of nanoscaled artificial pinning centers and their pinning properties in YBCO thin films grown by pulsed laser deposition technique. The two types of artificial pinning centers were prepared in different processes, (1) Y₂O₃ nanoislands decorated on substrates prior to the deposition of YBCO thin film, and (2) BaZrO₃ nanoparticles self-assembled within YBCO matrix during the deposition of YBCO thin film. We compared the transport characteristics of the YBCO thin films containing these two types of artificial pinning centers with those of pure YBCO thin films grown on decorated substrates and BZO-doped YBCO thin films grown on undecorated substrates. It was found that these two types of artificial pinning centers, which are simultaneously present, acted constructively to enhance the pinning properties of YBCO thin films.     

Photoelectrochemical performance of surfactant (polyvinyl alcohol) assisted PbS thin films grown by chemical route

Polyvinyl alcohol is used as a surfactant in the chemical bath deposition of PbS thin films, which causes compact, pinhole free and uniform PbS thin films. Influence of deposition time on the structural, optical, morphological, compositional, electro-chemical and photo-electrochemical (PEC) properties of the PbS thin films are studied. The charge transfer resistance is analysed using electrochemical impedance spectroscopy. The best PEC device fabricated using optimized deposition time (3 h) showed short circuit current density (J_sc) of 1.68 mA. After annealing the optimised P₆₃ sample at 75?°C for 1.5 h the composition changed from Pb rich to near stoichiometric. For typical PA sample J_sc improves to 2.13 mA and photo conversion efficiency advances from 0.045 to 0.072%.     

Addition of Na into CuInS2 thin film via co-evaporation

While most of studies focus on the addition of Na into CuInGaSe₂ as well as CuInGaS₂ thin films, this study examines the addition of Na into CuInS₂ (CIS) thin films. Moreover, an alternative approach has been used to incorporate Na into CIS thin films. Two source evaporation (Cu and In) was first performed to obtain Cu-In layers with desired thicknesses. Three source evaporation (Cu, In, and NaF) then followed subsequently to produce Na-doped Cu-In precursor films having different Na concentrations. The precursor films were immediately sulfurized in the same evaporation chamber to form CIS thin films. The addition of Na was found to enhance (112) preferred orientation and reduce the grain size. Raman spectra show that the addition of Na does not alter the needed phase transformation from CuInS₂-CuAu structure to CuInS₂-chalcopyrite structure during the sulfurization. Blue shift of the CIS Raman CH mode occurs as a result. The doping of Na was also found to decrease the film resistivity or increase the hole concentration in the films.     

Room temperature synthesis and characterization of polythiophene thin films by chemical bath deposition (CBD) method

Polythiophene thin films were deposited successfully on glass substrate by chemical bath deposition method using FeCl₃ as an oxidant and chloroform as solvent. The effect of oxidant concentration on the properties of polythiophene thin films was studied. The surface morphology was influenced by oxidant concentration and deposition time. The oxidation concentration also strongly affects the optical properties of the polythiophene thin films. The transmittance decreases while the absorption, band gap and refractive index increases due to increase in oxidant concentration.     

CuInS2 thin films obtained by spray pyrolysis for photovoltaic applications

Copper indium disulphide, CuInS₂, is a promising absorber material for thin film photovoltaic which has recently attracted considerable attention due to its suitability to reach high efficiency solar cells by using low-cost techniques. In this work CuInS₂ thin films have been deposited by chemical spray pyrolysis onto glass substrates at ambient atmosphere, using different composition solutions at various substrate temperatures. Structural, chemical composition and optical properties of CIS films were analysed by X-ray diffraction, energy dispersive X-ray spectroscopy and optical spectroscopy. Sprayed CIS films are polycrystalline with a chalcopyrite structure with a preferential orientation along the <112> direction and no remains of oxides were found after spraying in suitable conditions. X-ray microanalysis shows that a chemical composition near to stochiometry can be obtained. An optical gap of about 1.51 eV was found for sprayed CIS thin films.     

Electrical and optical studies of Ga-doped ZnO thin films

Nanostructure Ga-doped zinc oxide (GZO) thin films with highly (0 0 2) preferred orientation were fabricated on glass substrates, using radio frequency magnetron sputtering with an GZO ceramic target (The Ga₂O₃ contents was about 3 wt%) and different deposition conditions. The structural features, surface morphology and electrical and optical properties of the GZO thin films were studied, in terms of the deposition parameters. A Grey-based Taguchi method was used to determine the optimal deposition parameters for GZO thin films by considering multiple performance characteristics. The response graph and table for each level of the deposition parameters forms the Grey relational grade and the optimal levels of the deposition parameters were chosen. The experimental results show that the process pressure and the thickness make the most significant contribution to the overall performance. In the confirmation runs, Grey relational analysis showed that the improvement in deposition rate is 14.2 %, the improvement in electrical resistivity 38.1 % and the improvement in optical transmittance is 1.2 %. Annealing in a vacuum further improved the crystalline quality and optoelectronic performances of the GZO thin films.     

Application of Taguchi approach to optimize the sol–gel process of the quaternary Cu2ZnSnS4 with good optical properties

Present research deals with the optimal deposition parameters configuration for the synthesis of Cu₂ZnSnS₄ (CZTS) thin films using the sol–gel method associated to spin coating on ordinary glass substrates without sulfurization. The Taguchi design with a L9 (3⁴) orthogonal array, a signal-to-noise (S/N) ratio and an analysis of variance (ANOVA) are used to optimize the performance characteristic (optical band gap) of CZTS thin films. Four deposition parameters called factors namely the annealing temperature, the annealing time, the ratios Cu/(Zn + Sn) and Zn/Sn were chosen. To conduct the tests using the Taguchi method, three levels were chosen for each factor. The effects of the deposition parameters on structural and optical properties are studied. The determination of the most significant factors of the deposition process on optical properties of as-prepared films is also done. The results showed that the significant parameters are Zn/Sn ratio and the annealing temperature by applying the Taguchi method.     

Characterization of sprayed CuInS2 films by XRD and Raman spectroscopy measurements

We studied CuInS₂ (CIS) film growth using two deposition methods, which were high electrostatic field assisted ultrasonic spray (HEFAUS) deposition and sulfurization of Cu-In metallic film. The sprayed-films were grown with chalcopyrite ordering and Cu-Au ordering mixed. In order to obtain higher quality CIS films, post-sulfurization was carried out for sprayed-films. The post-sulfurization induced improvement of crystallinity and enhancement of chalcopyrite ordering. However, it was observed that Cu-Au ordering still coexisted in the CIS film after post-sulfurization. With the same sulfurization condition, sulfurization was done to transform Cu-In metallic film into CIS film. The sulfurized metallic film was turned out to be formed as CIS film with higher crystallinity and better chalcopyrite ordering than sulfurized sprayed-films. All fabricated films were characterized by X-ray diffraction, Raman scattering, scanning electron microscope and energy dispersive X-ray analysis measurements.     

Properties of spray deposited niobium oxide thin films

Niobium Oxide (Nb₂O₅) thin films were deposited on the glass substrates, using spray pyrolysis technique. During deposition the preparative parameters like nozzle to substrate distance, spray rate, concentration of the sprayed solution were kept constant at optimized values. The effect of substrate (deposition) temperature (varied between 250 to 450°C) and post annealing treatment (at temperature 500°C) on the structural, optical and electrical properties of thin films were studied. Using scanning electron microscopy and X-ray diffraction technique morphological and structural characterizations of the films were carried out. For optical and electrical properties of thin films, optical absorption and two probe electrical resistivity techniques were used. It has been observed that with increase in the substrate temperature films become micro or polycrystalline. Annealed films exhibit higher crystallinity. Other parameters like thickness, electrical resistivity and band gap energy value decrease with increase in substrate temperature.