Microstructural characterisation of Bi2Se3 thin films

The microstructure of Bi2Se3 thin films grown by molecular beam epitaxy on Si(111), InP(111)B and Fe-doped InP(111)B substrates has been studied in detail using scanning transmission electron microscopy. Films grown on Si(111) and InP(111)B substrates show the formation of twin domains: rotation twins (with the grain boundary perpendicular to the substrate) and lamellar twins (with the grain boundary parallel to the substrate). The presence of twins was confirmed by atomic-force microscopy (AFM) and X-ray diffraction (XRD). At the interface between Bi2Se3 film and Si(111) or InP(111)B substrates poorly crystallized layers of about 1 nm and 1.8 nm thickness, respectively, followed by well-crystallized Bi2Se3 layers, were found. The use of a Fe-doped InP (111) substrate with a rough surface enables the suppression of twin formation.