Abstract
By eliminating normal fabrication processes, we preserve the bulk insulating state of calcium-doped BiSe single crystals in suspended nanodevices, as indicated by the activated temperature dependence of the resistivity at low temperatures. We perform low-energy electron beam irradiation ( keV) and electrostatic gating to control the carrier density and therefore the Fermi level position in the nanodevices. In slightly -doped BiCaSe devices, continuous tuning of the Fermi level from the bulk valence band to the band gap reveals an enhancement (a factor of 10) in the field-effect mobility, which suggests suppressed backscattering expected for the Dirac fermion surface states in the gap of topological insulators.
- Received 16 October 2011
DOI:https://doi.org/10.1103/PhysRevB.85.201402
©2012 American Physical Society