Suppressing twin formation in Bi2Se3 thin films

TL;DR

This study demonstrates that using a rough Fe-doped InP(111)B substrate suppresses twin formation in Bi2Se3 thin films, resulting in high-quality, defect-minimized topological insulator layers with controlled domain structures.

Contribution

It reveals that substrate surface roughness and termination critically influence twin domain formation and defect structures in Bi2Se3 thin films grown by molecular beam epitaxy.

Findings

Rough Fe-doped InP(111)B substrates eliminate twin formation.

The films exhibit a perfect interface with the substrate.

Antiphase domain boundaries are the main remaining defects.

Abstract

The microstructure of Bi2Se3 topological-insulator thin films grown by molecular beam epitaxy on InP(111)A and InP(111)B substrates that have different surface roughnesses has been studied in detail using X-ray diffraction, X-ray reflectivity, atomic force microscopy and probe-corrected scanning transmission electron microscopy. The use of a rough Fe-doped InP(111)B substrate results in complete suppression of twin formation in the Bi2Se3 thin films and a perfect interface between the films and their substrates. The only type of structural defects that persist in the "twin-free" films is an antiphase domain boundary, which is associated with variations in substrate height. It is also shown that the substrate surface termination determines which family of twin domains dominates.