Comparative Study of the Microstructure of Bi 2 Se 3 Thin Films Grown on Si(111) and InP(111) Substrates

Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) have been carried out to clarify the microstructure of Bi 2 Se 3 thin films grown by molecular beam epitaxy (MBE) on Si(111) and InP(111) substrates. The film grown on InP displays much better overall quality at the microstructural level than does the film grown on the Si substrate. A layer of poor crystalline quality at the interface followed by well-crystallized Bi 2 Se 3 has been observed for both substrates. The thickness of this interface layer is not uniform; it varies across the sample from zero, showing a sharp interface between the substrate and Bi 2 Se 3, up to ∼1 nm and ∼1.8 nm for Bi 2 Se 3 /InP and Bi 2 Se 3 /Si, respectively. Formation of rotation twin domains and lamellar twins has been observed and is described in detail for both substrates.