Epitaxial growth of topological insulator Bi2Se3 film on Si(111) with atomically sharp interface

TL;DR

This paper demonstrates a two-step low-temperature then high-temperature growth process for achieving atomically sharp, strain-free Bi2Se3 topological insulator films on Si(111) substrates using MBE, verified by multiple microscopy techniques.

Contribution

It introduces a novel two-step growth method that produces high-quality, interface-free Bi2Se3 films on silicon, overcoming issues of phase separation and disorder.

Findings

Two-step growth yields atomically sharp interfaces.

Lattice relaxes to bulk value during first quintuple layer.

No strain or second phase detected in the film.

Abstract

Atomically sharp epitaxial growth of Bi2Se3 films is achieved on Si (111) substrate with MBE (Molecular Beam Epitaxy). Two-step growth process is found to be a key to achieve interfacial-layer-free epitaxial Bi2Se3 films on Si substrates. With a single-step high temperature growth, second phase clusters are formed at an early stage. On the other hand, with low temperature growth, the film tends to be disordered even in the absence of a second phase. With a low temperature initial growth followed by a high temperature growth, second-phase-free atomically sharp interface is obtained between Bi2Se3 and Si substrate, as verified by RHEED (Reflection High Energy Electron Diffraction), TEM (Transmission Electron Microscopy) and XRD (X-Ray Diffraction). The lattice constant of Bi2Se3 is observed to relax to its bulk value during the first quintuple layer according to RHEED analysis, implying the absence of strain from the substrate. TEM shows a fully epitaxial structure of Bi2Se3 film down to the first quintuple layer without any second phase or an amorphous layer.