Ultra-low carrier concentration andsurface-dominant transport in antimony-dopedBi_2se_3 topological insulator nanoribbons

摘要

A topological insulator is the state of quantum matter possessing gapless spin-locking surfacestates across the bulk band gap, which has created new opportunities from novel electronicsto energy conversion. However, the large concentration of bulk residual carriers has been amajor challenge for revealing the property of the topological surface state by electron transportmeasurements. Here we report the surface-state-dominant transport in antimony-doped, zincoxide-encapsulated Bi_2se_3 nanoribbons with suppressed bulk electron concentration. In thenanoribbon with sub-10-nm thickness protected by a zinc oxide layer, we position the Fermilevels of the top and bottom surfaces near the Dirac point by electrostatic gating, achievingextremely low two-dimensional carrier concentration of 2×1011cm~(-2). The zinc oxide-capped, antimony-doped Bi_2se_3nanostructures provide an attractive materials platform to studyfundamental physics in topological insulators, as well as future applications.