Tuning and Stabilizing Topological Insulator Bi2Se3 in the Intrinsic Regime by Charge Extraction with Organic Overlayers

TL;DR

This study demonstrates a cost-effective method to tune and stabilize the chemical potential of Bi2Se3 topological insulator films into the intrinsic regime using organic overlayers, achieving high mobility and environmental stability.

Contribution

It introduces organic charge extraction layers to control and maintain the intrinsic state of topological insulators, including the first use of an organometallic compound for this purpose.

Findings

Achieved chemical potential ~135 meV above Dirac point after 4 months.

Enhanced surface state electron mobility up to ~2000 cm2/Vs.

Realized stable topological insulator state at room temperature for months.

Abstract

In this work, we use charge extraction via organic overlayer deposition to lower the chemical potential of topological insulator Bi2Se3 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 tetrafluorotetracyanoquinodimethane(F4TCNQ) 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 represents the first use of an organometallic for modulating TI charge density. The mobility of surface state electrons is enhanced as high as ~2000 cm2/Vs. Even at room temperature, a true topologically insulating state is realized and stabilized for months' exposure to the atmosphere.