Structural defects and microindentation analysis of zone melted Bi2Te3−xSex whiskers

The dislocation density and microhardness of Bi2Te3−xSex (x=0–0.3 at% Se) grown by the zone melting method have been investigated. We also have got the whiskers of Bi2Te3−xSex at the end of ampoule during the growth process. SEM was characterized for surface analysis of the grown whisker. The length of the grown whiskers was around 10 mm in the direction of the crystallographic c-axis. Concentric pairs of dislocation triangle were observed on the as-grown surfaces of short hexagonal prisms. A systematic study of dislocations in these crystals was carried out by the chemical etching technique. Dislocation etching was achieved on all crystal planes examined using a saturated solution of citric acid and nitric acid as the etchant. The dislocation etchant has been found to give reproducible etch-pits on the cleavage surface. The use of citric acid and nitric acid proved to be especially advantageous for the basal plane, producing etched pits suitable for dislocation etch pit counting. The effects of Se doping, annealing and quenching on the mechanical properties have also been studied on the (001) faces of Bi2Te3−xSex.

► No major change is seen in c/a ratio with Se doping.
► The weak binding results in generation of needle shape whiskers.
► The Vickers hardness of quenched samples has been found to increase whereas for annealed sample it decreases.