Suppressing twin formation in Bi2Se3 thin films

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.