K. R. Murali

Preparation and properties of zinc phosphide thin films

Abstract Zinc phosphide (Zn3P2) was prepared by the carbon reduction process. Thin films of Zn3P2 were evaporated onto glass substrates at various substrate temperatures. Films evaporated onto substrates at and above 220 °C were polycrystalline in nature. Films of different thicknesses were grown and their electrical conductivity was measured in the temperature range 100–300 K. Four characteristic energy gaps of 1.3, 1.66, 1.75 and 1.82 eV were obtained from the analysis of the optical absorption spectrum.

Growth and characterization of CuInSe2 films by close-space evaporation

Abstract CuInSe 2 thin films were prepared on mica substrates using an evaporation technique which involved varying the distance between the source and the substrate. Films evaporated on substrates at distances less than 1 cm from the source exhibited preferential orientation in the (112) direction. The grain size increased from 0.5 to 1.0 μ m as the source substrate distance decreased from 3 to 1 cm. The conductivity increased with a decrease in the distance between the source and substrate. Electron probe microanalysis of these films showed that films coated on substrates farther away from the source had a slight selenium deficiency and an excess of indium. Three characteristic energy gaps of 1.01, 1.25 and 2.4 eV were obtained from an analysis of the optical absorption spectrum. The optical transition probability for valence band to conduction band transitions was estimated to be 10.91 eV which gives an admixture of copper d states to the valence band of 32%.

Properties of Zn3P2 films grown by close space evaporation

Zn3P2 thin films have been prepared on mica substrates by the evaporation technique, varying the distance between the source and substrate. Films evaporated on substrates at distances less than 3 cm from the source were polycrystalline in nature. The grain size increased from 0.2 to 0.8 μm as the source-to-substrate distance decreased from 3 to 1 cm. The variation in electrical conductivity has been studied in the temperature range 100–300 K. The conductivity increases with an increase in temperature and with a decrease in distance between the source and substrate. These results have been analysed on the basis of Motts variable-range hopping mechanism. Four characteristic energy gaps of 1.3, 1.52, 1.68 and 1.88 eV were obtained from an analysis of the optical absorption spectrum.

The role of impurities in the dielectric properties of Zn3P2 phosphide crystals

Abstract The dielectric properties of zinc phosphide (Zn3P2) crystals doped with impurities such as magnesium, indium, tin and selenium have been studied in the frequency range 103–105 Hz and in the temperature T range 300–500 K. It may be inferred from the present study that doping Zn3P2 with the above-mentioned impurities results either in a reduction in the number of grain boundaries or in a decrease in the space charge density at room temperature. At higher temperatures the behaviour is not systematic.