Scanning tunneling microscopy of gate tunable topological insulator Bi sub(2)Se sub(3) thin films

Electrical-field control of the carrier density of topological insulators (TIs) has greatly expanded the possible practical use of these materials. However, the combination of low-temperature local probe studies and a gate tunable TI device remains challenging. We have overcome this limitation by scanning tunneling microscopy and spectroscopy measurements on in situ molecular-beam epitaxy grown Bi sub(2)Se sub(3) films on SrTiO sub(3) substrates with prepatterned electrodes. Using this gating method, we are able to tune the Fermi level of the top surface states within a range of [approximate]250 meV on a 3-nm-thick Bi sub(2)Se sub(3) device. We report field effect studies of the surface-state dispersion, band gap, and electronic structure at the Fermi level.