B.S. Naidu

Physical investigations on electron beam evaporated V2O5–MoO3 thin films

Abstract Thin films of the system (V 2 O 5 ) 1− x –(MoO 3 ) x with 0⩽ x ⩽l were prepared by electron-beam evaporation technique in an oxygen partial pressure of 2×10 −4 mbar onto silicon substrate maintained at temperature of 423 K. X-ray photoelectron spectroscopy and infrared data of these samples suggest that the film composition nearly approaches the nominal stoichiometry. The optical absorption studied in the wavelength range 300–1500 nm shows that the optical band gap increases with the increase of the MoO 3 content in V 2 O 5 –MoO 3 films. The electrical measurements exhibit a decrease of the conductivity with increasing MoO 3 concentration. Results suggest the formation of the (V 2 O 5 ) 1− x –(MoO 3 ) x solid solution.

Characterization of laser-ablated V2O5 thin films

Vanadium pentoxide thin films have been prepared by the pulsed laser deposition technique. The influence of substrate temperature on the growth of V2O5 films was studied. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and atomic force microscopy (AFM) measurements have been carried out in order to understand the growth mechanism. The crystallization in V2O5 thin films starts at deposition temperatures as low as 473 K and the grain size increased with deposition temperature. The films exhibited predominantly (0 0 1) orientation, representing the orthorhombic layered structure. The infrared (IR) and Raman measurements supported the above data.

A.c. conductivity studies on Al/MoO3/Al sandwich structures

Abstract Molybdenum trioxide films were grown by an electron beam evaporation technique onto Corning glass substrates maintained at temperatures in the range 303–573 K. The films were characterized by studying their structure and optical properties. The d.c. conductivity studies revealed that electron hopping and thermally activated conduction processes were operated in the temperature range 160–400 K. The frequency and temperature dependences of the capacitance and the dielectric loss were systematically studied and the activation energy is found to be about 0.3 eV.

Characterization of p-AglnSe2/n-Zn0.35Cd0.65S polycrystalline thin film heterojunctions

Abstract Polycrystalline thin film p -AglnSe 2 / n -Zn 0.35 Cd 0.65 S heterojunctions were fabricated and the current density-voltage, capacitancevoltage and spectral response characteristics of the junctions were studied. The heterojunction was illuminated in the back-wall configuration and an open-circuit voltage of 425 mV, a short-circuit current density of 30 mA cm −2 and an electrical conversion efficiency of 7.5% have been obtained for a cell with an active area of 1 cm 2 under a solar input of 100 mW cm −2 .

Electrical properties of CuGaTe2 thin films

Abstract CuGaTe 2 thin films were prepared by the flash evaporation technique. The influence of substrate temperature ( T s ) on the electrical characteristics was studied. The films formed at T s = 523–573 K were polycrystalline, single phase and nearly stoichiometric. The films of 0.7 μm thickness showed an electrical resistivity of about 10 −2 Ω cm, a mobility of 55 cm 2 V −1 s −1 with a carrier concentration of 1.5 × 10 19 cm −3 . The electrical resistivity was found to decrease with film thickness, whereas the mobility increased. The activation energies were also determined in the temperature range 300–575 K.