P. H. Soni

Creep activation energy of flow process in Bi2Te2·8Se0·2 single crystals

Temperature dependence of the Vickers microhardness of Bi2Te2·8Se0·2 single crystals has been studied. Loading time dependence of microhardness at different temperatures has been used for creep study in the temperature range 303 K-373 K. The activation energy for indentation creep of the crystals has been evaluated.

Optical bandgap of Sb0.2Bi1.8Te3 thin films

Sb0.2Bi1.8Te3 Thin Films were grown using the thermal evaporation technique on a (001) face of NaCl crystal as a substrate at room temperature. The optical absorption was measured in the wave number range 500 cm−1 to 4000 cm−1. From the optical absorption data the bandgap has been evaluated and studied as a function of the film thickness and deposition temperature. The data indicate absorption through direct interband transition with a bandgap around 0.21 eV. The detailed results are reported.

Effects of anisotropy and annealing on microhardness of In x Bi2−x Te3 (x=0·1 to 0·5) single crystals

The crystals of InxBi2−xTe3 (x=0·1 to 0·5) have been grown by zone-melting method. In order to study anisotropy exhibited by the (0001) plane of the crystals, the directional hardness was determined by producing indentations at various azimuthal orientations of the indentor with respect to the surface over a range 0–180°. The crystal was rotated about the indentor axis in steps of 15° while keeping applied load and loading time constant at 50 g and 20 sec, respectively. For annealing study, the sample was kept at a temperature of 375°C. It was observed that softening of crystal takes place and the hardness decreases to a considerable extent.