B. Srinivasulu Naidu

Spectroscopic characterization of electron-beam evaporated V2O5 thin films

Thin films of vanadium pentoxide (V2O5) were prepared by electron beam evaporation at different deposition temperatures. The chemical composition and structural and optical properties were investigated employing spectroscopic techniques, viz. X-ray photo-electron spectroscopy (XPS), inductively coupled plasma atomic emission spectroscopy (ICP-AES), infrared spectroscopy (IR), Raman spectroscopy (RS) and optical spectroscopy (OS). The influence of deposition temperature on the film properties were deduced from the spectroscopic measurements. The room temperature (303 K) electron-beam evaporated V2O5 films were nearly stoichiometric. The films formed at elevated temperatures were sub-stoichiometric as revealed (XPS) from the shift of the V(2p3/2) emission peak, the broadening of full width at half maximum (FWHM) and the decrease in the O(1s):V(2p3/2) ratio. The shift of vanadyl mode in the IR and Raman spectra, decrease of the optical band gap and increase in the near-infrared-broad band absorption also supported the sub-stoichimetric nature. Annealing of the films formed at Ts∼553K in an oxygen atmosphere (a partial pressure of 10−4 mbar) at 693 K led to the existence of vanadium in its highest oxidation state.

Preparation and characterization of CdO films deposited by dc magnetron reactive sputtering

This paper deals with the dc magnetron reactive sputtering of cadmium in an oxygen and argon atmosphere. The dependence of cathode potential on the oxygen partial pressure has been explained in terms of cathode poisoning effects. The cadmium oxide films formed during this process have been studied for their structural, electrical and optical properties. At an optimum oxygen partial pressure of 1×10−3 mbar, the films were single phase with polycrystalline in nature. The films showed resistivity of 4.6×10−3 Ω cm, Hall mobility of 53 cm2/V s, carrier concentration of 3.5×1019 cm−3, with an optical transmission of 85% in the wavelength range 600–1600 nm and with a band gap of 2.46 eV.

Physical properties of zinc oxide films prepared by dc reactive magnetron sputtering at different sputtering pressures

Thin films of zinc oxide were deposited by dc reactive magnetron sputtering onto glass substrates held at a temperature of 663 K and oxygen partial pressure of 1x10 -3 mbar, and at different sputtering pressures in the range 3x10 -2 - 10x10 -2 mbar. The effect of sputtering pressure on the structural, electrical and optical properties of the films were systematically studied. The films were polycrystalline in nature with preferred (002) orientation. The temperature dependence of Hall mobility indicated that the grain boundary scattering of the charge carriers are predominant in these films. The films formed at a sputtering pressure of 6x10 -2 mbar showed a low electrical resistivity of 6.9x10 -2 Ω.cm, optical transmittance of 83% with an optical band gap of 3.28 eV.

Physical investigations on electron-beam evaporated vanadium pentoxide films

Abstract Thin films of vanadium pentoxide were prepared by the electron-beam evaporation technique onto Corning 7059 glass and silicon substrates maintained at Ts=553 K by varying the oxygen partial pressure in the range 0.1–20 mPa. These films have been characterized by studying their chemical state, structure, optical and electrical properties. V2O5 films of thickness 0.6 μm prepared at an oxygen partial pressure of 20 mPa exhibit an orthorhombic layered structure with an optical band gap of 2.3 eV. The room temperature electrical conductivity of the films is 2×10−5 S cm−1 with an activation energy of 0.42 eV in the temperature range 303–523 K.

Structure and Optical Properties of dc Reactive Magnetron Sputtered Zinc Oxide Films

Zinc oxide films were deposited on glass substrates in argon and oxygen atmosphere by dc reactive magnetron sputtering using a metallic zinc target. The influence of oxygen pressure and substrate temperature on the structure and optical properties of the films were systematically investigated and optimised the deposition parameters to prepare single phase zinc oxide films with preferred (002) orientation. At an optimum oxygen pressure of 1x10 -3 mbar and substrate temperature of 663 K, the films exhibited an optical transmittance of 83% with a band gap of 3.28 eV.

Structure-composition-property dependence in reactive magnetron sputtered ZnO thin films

Thin films of zinc oxide (ZnO) were prepared by dc reactive magnetron sputtering on glass substrates at various oxygen partial pressures in the range 1 x 10(-4)-6 x 10(-3) mbar and substrate temperatures in the range 548-723 K. The variation of cathode potential of zinc target on the oxygen partial pressure was explained in terms of target poisoning effects. The stoichiometry of the films has improved with the increase in the oxygen partial pressure. The films were polycrystalline with wurtzite structure. The films formed at higher substrate temperatures were (002) oriented. The temperature dependence of Hall mobility of the filins formed at various substrate temperatures indicated that the grain boundary scattering of charge carriers was predominant electrical conduction mechanism in these films. The optical band gap of the films increased with the increase of substrate temperature. The ZnO films formed under optimized oxygen partial pressure of 1 x 10(-3) mbar and substrate temperature of 663 K exhibited low electrical resistivity of 6.9 x 10(-2) Omega cm, high visible optical transmittance of 83%, optical band gap of 3.28 eV and a figure of merit of 78 Omega(-1) cm(-1).

Photovoltaic performance of p-AgInSe2/n-CdS thin film heterojunctions

Abstract Polycrystalline thin film p-AgInSe 2 /n-CdS heterojunctions were fabricated and current density–voltage, capacitance–voltage and spectral response of the junctions were studied. The heterojunction was illuminated in the back-wall configuration and an open-circuit voltage of 500 mV, a short-circuit current density of 24 mA cm −2 and an electrical conversion efficiency of 6% have been obtained for a cell 1 cm 2 in area under a solar input of 100 mW cm −2 .

Optical properties of spray deposited ZnO films

Abstract Transparent conducting ZnO films were deposited on Corning 7059 glass substrates by spray pyrolysis technique. The films showed high transparency around 0.5 μm, at which maximum solar radiation is obtained, and a high reflectance in the infrared region. The figure of merit was evaluated from the resistivity and transmittance data.

Influence of oxygen partial pressure on the optical properties of electron beam evaporated vanadium pentoxide thin films

Vanadium pentoxide thin films were prepared using the electron beam evaporation technique at different oxygen partial pressures keeping the substrate temperature Ts=553 K. The films were characterized by studying their structure and optical properties. The transmittance and reflectance of the films were used to evaluate the optical band gap, width of the localized states and the optical constants n and k. The effect of oxygen partial pressure on the optical band gap, and the width of the localized states was studied in detail. The wavelength dependence of n and k is also reported.

Effect of substrate temperature on the electrical and optical properties of dc reactive magnetron sputtered indium oxide films

Abstract Thin films of indium oxide (In2O3) were deposited onto glass substrates held at temperatures in the range 373–673 K using the dc reactive magnetron sputtering technique. The dependence of electrical and optical properties of the films on the substrate temperature was studied. The films formed at 373 K were amorphous, whereas those prepared at ⩾473 K were polycrystalline in nature. The electrical resistivity of the films decreased from 2.4×10−2 to 1.3×10−3 Ω cm and the Hall mobility increased from 2.5 to 18 cm 2 V −1 s −1 with the increase of substrate temperature from 373 to 673 K, respectively due to improvement in the crystallinity of the films. The temperature dependence of the Hall mobility revealed that the grain boundary scattering of the charge carriers predominated in the films. The optical transmittance (at λ=600 nm) increased from 68% to 85% and the optical band gap increased from 3.64 to 3.78 eV with the increase of substrate temperature from 373 to 673 K, respectively.