Intrinsic Ultrathin Topological Insulators Grown via MBE Characterized by in-situ Angle Resolved Photoemission Spectroscopy

TL;DR

This paper reports the successful growth of high-quality ultrathin topological insulator films of Bi2Se3 and Bi2Te3 via molecular beam epitaxy, characterized by in-situ ARPES, showing intrinsic bulk insulating behavior and surface states crossing the Fermi level.

Contribution

It introduces a novel growth method that maintains the intrinsic insulating nature of ultrathin topological insulator films, overcoming limitations of previous techniques.

Findings

Films remain intrinsic bulk insulators with surface states crossing the Fermi level

Thermal cracking of Te and Se improves film quality

ARPES confirms the bandstructure of grown films

Abstract

We demonstrate the capability of growing high quality ultrathin films of the topological insulators Bi2Se3 and Bi2Te3 using molecular beam epitaxy. Unlike previous growth techniques, which often pin the Fermi energy in the conduction band for ultrathin samples, our samples remain intrinsic bulk insulators. We characterize these films using in-situ angle resolved photoemission spectroscopy (ARPES), which is a direct probe of bandstructure, and ex-situ atomic force microscopy. We find that the conduction band lies above the Fermi energy, indicating bulk insulating behavior with only the surface states crossing EF . We conclude that thermal cracking of Te and Se in our growth leads to higher quality thin films, paving the way for future improvements in growth of topological insulators.