Tuning and stabilizing topological insulator Bi_2Se_3 in the intrinsic regime by charge extraction with organic overlayers

摘要

In this work, we use charge extraction via organic overlayer deposition to lower the chemical potential of topological insulator (TI) Bi_2Se_3 thin films into the intrinsic (bulk-insulating) regime. We demonstrate the tuning and stabilization of intrinsic topological insulators at high mobility with low-cost organic films. With the protection of the organic charge extraction layers tetrafluorotetracyano-quinodimethane or tris(acetylacetonato)cobalt(Ⅲ) (Co(acac)_3), the sample is stable in the atmosphere with chemical potential ～135 meV above the Dirac point (85 meV below the conduction band minimum, well within the topological insulator regime) after four months, which is an extraordinary level of environmental stability. The Co complex demonstrates the use of an organometallic for modulating TI charge density. The mobility of surface state electrons is enhanced as high as ～2000 cm~2/V s. Even at room temperature, a true topologically insulating state is realized and stabilized for months' exposure to the atmosphere.