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Vanadium pentoxide (V2O5) and indium tin oxide (ITO) coated V2O5 thin films were prepared by hydrothermal technique. The influence of different molarity of V2O5 on the electrical properties of ITO-V2O5 films was investigated. The films were found to be polycrystalline and to belong to a V2O5 orthorhombic crystal system based on their X-ray diffraction (XRD) analysis. It was confirmed by Fourier transform infrared (FTIR) spectrum that V2O5 functional groups formed a V-O bond. The optical band gaps were found to increases with increasing molarity in the range 2.18 - 2.89 eV. Scanning electron microscopy (SEM) analysis shows crumbled paper-like morphology in the sheet-like layer arrangement. The dielectric current (DC) electrical conductivity was studied as function of molarity which indicated the semiconducting nature. The morphological and structural studies show enhanced results for 4% sample which makes it a viable candidature for optical and electrical applications. [ABSTRACT FROM AUTHOR]

Abstract Bi-rich Bi 2 Te 3 thin films are prepared at 300 K using e-beam evaporation technique. A source power of 45 W for e-beam is used. Post deposition, these as-deposited Bi-rich Bi 2 Te 3 (Bi-BT-AD) films are annealed at 100 °C (Bi-BT-100), 200 °C (Bi-BT-200) and 300 °C (Bi-BT-300) for 1 h under a pressure of 3 × 10−4 Pa. X-ray diffraction measurements reveal the presence of Bi phase together with crystalline Bi 2 Te 3 indicating the possible presence of Bi-rich Bi 2 Te 3 phase in the Bi-BT-AD film. The broad peaks from Bi 2 Te 3 (015) plane indicate nanocrystalline nature of particles. With annealing, no change in diffraction pattern is observed for Bi-BT-100. However, Bi-BT-200 and Bi-BT-300 films show the emergence of x-ray reflection from unknown phases around 2θ ~ 20° and 47°. This indicates Bi related secondary phase segregation and the thermodynamic instability for the presence of Bi in Bi 2 Te 3 lattice. From Raman studies it is discerned that Bi secondary phase coexists along with the Bi-rich Bi 2 Te 3 nanocrystalline grains. On vacuum annealing Bi-rich Bi 2 Te 3 phase in thin films prevails as evidenced from the p-type electrical characteristics, while excess Bi disappears and converts into an unknown minor phase. The resistivity of all the annealed films are ~ 0.9 × 10−4 Ωcm. The Seebeck coefficients also do not show any change and remain around 33 to 36 μV/K. Thermoelectric properties of Bi-BT-100 exhibit high power factors when measured at different ΔT with a maximum of ~ 17.5 × 10−4 W/K2 m for ΔT = 100 °C. Thus, unlike the near-stoichiometric thin films, Bi-rich thin films require low temperature annealing (~100 °C) to achieve optimized parameters. Bi-rich Bi 2 Te 3 thin films also show higher power factor compared to the near-stoichiometric thin films. Thus, favourable thermoelectric properties can be achieved at 300 K for temperature sensitive device fabrication using Bi-rich Bi 2 Te 3 thin films. Highlights • Nanocrystalline Bi-rich Bi 2 Te 3 (Bi-BT) thin films are made by e-beam evaporation. • Vacuum annealed Bi-BT thin films exhibit p-type conductivity. • High power factor of ~ 17.5 × 10−4 W/K2 m are favourable for thermoelectric applications. • For low temperature processed device applications, Bi-BT are most suitable. • Bi-BT require low annealing (~100 °C) to acquire desirable thermoelectric properties. [ABSTRACT FROM AUTHOR]

Size tunability and enhanced optical properties of cadmium sulphide (CdS) nanoparticles entrapped in polymethyl methacrylate (PMMA) matrix were presented in this paper. The three-dimensional quantum confinement of CdS in the PMMA matrix was achieved by the in situ technique. X-ray diffraction results show the presence of CdS in the PMMA matrix for higher concentration of CdS nanoparticles (1:20). The particle size and energy band gap were determined by UV-visible spectroscopy. The photoluminescence spectrum shows broadened surface trapped emissions that are shifted towards the blue region. The formation of CdS and its stoichiometric ratio has been confirmed using X-ray photoelectron spectroscopy. The transmission electron microscope results reveal the uniform distribution of nanometre sized particles in the PMMA matrix. The size distribution of CdS nanoparticles in the nanocomposite was carried out by atomic force microscope. [ABSTRACT FROM AUTHOR]

Abstract: In this paper solution mixing and casting of Cd(NO3)2·4H2O and poly(ethylene oxide) (PEO) at different molar ratios (1:100–1:600) followed by hydrogen sulfide treatment were employed to fabricate solid films of cadmium sulfide (CdS)/polyethylene oxide (PEO) nanocomposites. The nanocomposites were found to exhibit uniform distribution of CdS nanoparticles in the polymer matrix without any additional capping agent. Systematic investigations on the role of PEO on the optical properties of CdS are presented. The optical properties of the composites examined by UV–vis absorption spectroscopy show that the band gap of CdS nanoparticles increases from 2.45eV to 2.54eV with decreasing concentration of CdS in PEO films. X-ray diffraction pattern shows the broadening in shape of the PEO peaks which is induced by the CdS particles in PEO matrix. The CdS particle sizes ranging from 10 to 20nm are clearly seen in a transmission electron microscope (TEM). The X-ray photoelectron spectroscopic studies (XPS) also confirm the presence of CdS in PEO. Fourier transform infrared spectroscopy studies using attenuated total reflectance (FTIR-ATR) indicate the influence of Cd2+ ion on C–O–C stretching in PEO and confirm the presence of CdS nanoparticles within PEO. Photoluminescence spectroscopy (PL) shows the broad emission due to the presence of surface trapped carrier states. [Copyright &y& Elsevier]

Ge 2 Sb 2 Te 5 thin films were deposited by electron beam evaporation onto glass substrates at 303 K and 453 K substrate temperatures. The effect of film microstructure (modified by substrate temperature) on optical properties over the visible region was analyzed. It is observed that Ge 2 Sb 2 Te 5 thin films show good optical contrast in the lower wavelength region. Microstructural and spectral dependence on optical constants (n & k) of the films were studied. The optical band gap and the nature of transition of the Ge 2 Sb 2 Te 5 thin films also have been reported. Amorphous to crystalline microstructural phase change due to substrate temperature in these films was confirmed by X-ray diffraction and SEM analysis. [ABSTRACT FROM AUTHOR]

• Nanocrystalline Te-rich Bi 2 Te 3 thin film is prepared by e−−beam deposition at 300 K. • Vacuum annealing lead to intergrown Te-rich layers between the quintuples. • Disordered planar structures are mostly concentrated on the crystallite surface. • Seebeck coefficient becomes maximum (~ 97 μV/K) for the film annealed at 200 °C. • Te-rich Bi 2 Te 3 with S2σ ~29 × 10−4 W/K2m is good for thermoelectric applications. Tellurium-rich Bi 2 Te 3 thin films are deposited by electron−beam evaporation technique at 300 K. These as-deposited thin films are further annealed at 100 °C, 200 °C and 300 °C for 1 h at a pressure of 3 × 10−4 Pa. X-ray diffraction (XRD) patterns of as-deposited films distinctly show Te phase along with Bi 2 Te 3. Peak intensity ratio suggests the polycrystalline nature of as-deposited Bi 2 Te 3 films. On vacuum annealing Te-rich Bi 2 Te 3 films exhibit improved crystallinity with a c -axis preferred orientation. In addition, structural features related to Te and Bi 2 Te 3 composition change with Te fraction diminishing on annealing at 300 °C. From Raman spectral studies, the presence of distinct Te-rich regions, predominantly within the interlayers of Bi 2 Te 3 , are discerned. Te becomes structurally integrated within the quintuples of Bi 2 Te 3 lattice as intergrown layers. Disordered planar structures, mostly concentrated on crystallite surfaces result from Te accumulations as evidenced in high-resolution transmission electron microscopy lattice images and energy dispersive X-ray spectroscopy mapping. These are consistent with the observations from XRD and Raman studies further confirming Te-rich Bi 2 Te 3 characteristics. Electrical properties of Te-rich Bi 2 Te 3 thin films exhibit n-type semiconductor behaviour. Seebeck coefficient for as-deposited film is ~ 32 μV/K, which increases to ~ 97 μV/K on 200 °C annealing. Resistivity increases from 1.39 × 10−4 Ωcm to 18.76 × 10−4 Ωcm and power factor changes from 7.4 × 10 − 4 W / K 2 m to 27.17 × 10 − 4 W / K 2 m going through a maximum at 200 °C upon systematic annealing. Te-rich Bi 2 Te 3 thin films annealed at 200 °C exhibit high power factor (∼ 29 × 10 − 4 W / K 2 m) for a wide range of temperature gradients (ΔT from 30 °C to 165 °C). [ABSTRACT FROM AUTHOR]

A simple close-spaced vapour transport (CSVT) system has been designed and fabricated. Copper indium diselenide (CuInSe2) thin films of wide range of thickness (4000–60000 A˚) have been prepared using the fabricated CSVT system at source temperatures 713, 758 and 843 K. A detailed study on the deposition temperature has been made and the temperature profile along with the reaction kinetics is reported. The composition of the chemical constituents of the films has been determined by energy dispersive X-ray analysis. The structural characterization of the as-deposited CuInSe2 films of various thicknesses has been carried out by X-ray diffraction method. The diffractogram revealed that the CuInSe2 films are polycrystalline in nature with chalcopyrite structure. The structural parameters such as lattice constants, axial ratio, tetragonal distortion, crystallite size, dislocation density and strain have been evaluated and the results are discussed. The surface morphology of the as-deposited CuInSe2 thin films has been studied using scanning electron microscope. The transmittance characteristics of the CuInSe2 films have been studied using double beam spectrophotometer in the wavelength range 4000–15000 A˚ and the optical constants n and k are evaluated. The absorption coefficient has been found to be very high and is of the order of 105–106 m−1. CuInSe2 films are found to have a direct allowed transition and the optical band gap is found to be in the range 0.85–1.05 eV. [Copyright &y& Elsevier]

Gallium-doped zinc oxide (GZO) thin films with very high conductivity and transparency were successfully deposited by RF magnetron sputtering at a substrate temperature of 400 °C. The dependence of the film properties over the thickness was investigated. X-ray diffraction (XRD) results revealed the polycrystalline nature of the films with hexagonal wurtzite structure having preferential orientation along [001] direction normal to the substrate. The lowest resistivity obtained from electrical studies was 5.4×10 −4 Ω cm. The optical properties were studied using a UV–vis spectrophotometer and the average transmittance in the visible region (400–700 nm) was found to be 92%, relative to the transmittance of a soda–lime glass reference for a GZO film of thickness 495 nm and also the transparency of the films decreases in the near IR region of the spectra. The mobility of the films showed a linear dependence with crystallite size. GZO film of thickness 495 nm with the highest figure of merit indicates that the GZO film is suitable as an ideal transparent conducting oxide (TCO) material for solar cell applications. [ABSTRACT FROM AUTHOR]