Ultrathin (Bi_1-xSb_x)₂Se₃ Field Effect Transistor with Large ON/OFF Ratio

Ultrathin three-dimensional topological insulator films are promising for use in field effect devices. (Bi_1-xSb_x)₂Se₃ ultrathin films were fabricated on SrTiO₃ substrate, where large resistance changes of ∼25 000% could be achieved using the back gate voltage. We suggest that the large ON/OFF ratio was caused by the combined effect of Sb-doping and the reduction of film thickness down to the ultrathin regime. The crossover of different quantum transport under an electric field may form the basis for topological insulators (TI)-based spin transistors with large ON/OFF ratios in the future.