Generation and characterization of extended-length dislocations in BiSb alloys

Abstract

Narrow bandgap semiconducting Bi–Sb alloys with ∼10 at. % Sb were recently identified as strong topological insulators with non-trivial weak indices. Consequently, topologically-protected conduction is predicted to occur along certain dislocations. Recently, uniaxial compression of Bi0.87Sb0.13 was reported to lead to a conductivity enhancement presumed to be associated with dislocations. However, with dislocation lengths limited to 1–2 μm, the nature of the dislocations and their role in enhanced conduction in deformed BiSb remains unknown. Here, we generate multiple-micrometer-length {011}⟨100⟩ type dislocations in [111]-oriented Bi0.89Sb0.11 single crystals using cyclic uniaxial compression along [2¯11] and instrumented nanoindentation with a wedge-shaped tip. We consider the contributions to plastic deformation via secondary slip, including dislocation pile-ups, cross-slip, and twinning. Finally, we describe a framework for probing the topological states associated with dislocations using high magnetic fields to suppress bulk conduction and a Corbino contact geometry to eliminate side-surface conduction.