Thermoelastic and electronic properties of Bi1-xSbx and similarly bound materials.

Abstract

The thermoelastic effect (TEE) of perfectly grown ${\mathrm{Bi}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sb}}_{\mathit{x}}$ crystals shows a clear periodic behavior as a function of the composition parameter x with a period of 5.5% for 0\ensuremath{\le}x\ensuremath{\le}0.19. Melting and subsequent rapid solidification of the samples causes this phenomenon to disappear, leading to the assumption of superlattice incorporation of the Sb constituents into the bismuth matrix in the first case. Furthermore, since the weakest bonds should dominate the TEE, they have to be correlated with the electronic energy extrema at the L points of the pseudocubic Brillouin zone. Insertion of Sb and Bi atoms in the ratio 1:2 into one of the trigonal layers with a trigonal lattice constant over three double layers leads to a 1/3 occupation of the superlattice for x=0.055 with equidistant hexagonal layers. The assumption of two different ${\mathit{sp}}^{3}$${\mathit{d}}^{2}$ and ${\mathit{p}}^{3}$${\mathit{d}}^{3}$ valence hybrids suggests a relation between the superlattice crystal axes and the main axes of the L-band constant-energy surfaces, which also applies to ${\mathrm{V}}_{2}$${\mathrm{VI}}_{3}$, IV-VI, IV-${\mathrm{VI}}_{2}$, and similar materials.