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

Stoichiometric crystals of Bi₂Te₃ and Bi₂Te_2.9Se_.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 Bi₂Te_2.9Se_.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.