Hot wall epitaxy of topological insulator films

Hot-wall-epitaxy growth of Bi2Se3, Bi2Te3 and Sb2Te3 films is carried out on Si as well as GaAs surfaces. For Bi2Se3, self-assembled dots are formed at the initial stage of the growth due to the large lattice mismatch. The dots expand in a way to fill the whole substrate surface with (0 0 0 1)-oriented domains. While no in-plane epitaxial orientation relationship is established between the films and the substrates, the influence of the substrates is reflected in the morphology of the films. Throughout the growth, micrometer-size free-standing disks are spontaneously generated and eventually cover the whole surface. The disk geometry manifests that the Bi2Se3 crystal grows preferentially in the in-plane directions of the (0 0 0 1)-plane. For Bi2Te3 and Sb2Te3, we experience thermal decomposition. Although nanowires can be generated under low source-flux intensities, they are solely composed of Te as a consequence. Owing to different solidification temperatures, we obtain Bi2Te3 islands when the substrate temperature is raised. The surface of these islands is remarkably flat and the typical thickness is less than 10 nm.