Dislocation, annealing and quenching effects on the microindentation hardness of Bi2Te3 and Bi2Te2.9Se.1 single crystals

Stoichiometric crystals of Bi2Te3 and Bi2Te2.9Se.1 have been grown from the melt by the horizontal zone melting (HZM) technique. X-ray powder diffraction and energy dispersive X-ray analysis could prove that the grown crystals are stoichiometric with lattice constants a=0.4374 nm, c=3.044 nm for Bi2Te3 and a=0.4374 nm, c=3.038 nm for Bi2Te2.9Se.1. Dislocation density measurements are carried out by etch pit technique and are observed by scanning electron and optical micrograph. The mechanical strength of the as-grown, quenched and annealed crystals is assessed by the Vickers hardness measurements.