High-Density Well-Aligned Dislocations Introduced by Plastic Deformation in Bi1−xSbx Topological Insulator Single Crystals

Abstract

Topological insulators (TIs) have a bulk bandgap and gapless edge or surface states that host helically spin-polarized Dirac fermions. Theoretically, it has been predicted that gapless states could also be formed along dislocations in TIs. Recently, conductivity measurements on plastically deformed bismuth antimony (Bi1−xSbx) TIs have revealed excess conductivity owing to dislocation conduction. For further application of them, fundamental study on dislocations in TIs is indispensable. Dislocations controlled based on fundamental studies could potentially be useful not only for experimental investigations of the dislocation properties but also for diverse device applications. In the present study, Bi1−xSbx TI single crystals were fabricated by a zone-melting method. The crystals were plastically deformed at room temperature. The resultant dislocations were observed by transmission electron microscopy (TEM). It was found that high-density dislocations with the Burgers vector satisfying the condition for the formation of gapless states were successfully introduced. The dislocations were mostly of edge type with lengths on the order of more than a few micrometers.

High Mechanical Property and Texture Degree of Hot-Extruded Bi_0.905Sb_0.095

“…Despite Bi1-xSbx single crystals exhibiting good thermoelectric properties, their poor mechanical performances have hindered their practical applications. In the past decades, powder metallurgy combined post-deformation, [19][20][21][22] extrusion, [23][24][25][26] and hot-pressing [27][28][29] have been utilized to improve mechanical strength. The reduction of grain size can effectively prevent further extension of the fracture and then improve the mechanical properties.…”

High Mechanical Property and Texture Degree of Hot-Extruded Bi0.905Sb0.095

“…Despite Bi 1−x Sb x single crystals exhibiting good thermoelectric properties, their poor mechanical performances have hindered their practical applications. In the past decades, powder metallurgy combined post-deformation [19][20][21][22] extrusion [23][24][25][26], and hot-pressing [27][28][29] have been utilized to improve mechanical strength. The reduction in grain size can effectively prevent further extension of the fracture and then improve the mechanical properties.…”