Thin film growth of 3R-b’-In2Se3 on Al2O3 and Si(111) substrates by molecular beam epitaxy

This work describes the growth of b-In2Se3 via molecular beam epitaxy along with characterization of its properties. The thin film morphology, crystal structure and phase maps of b-In2Se3 on Si(111) and Al2O3(0001) were evaluated by atomic force microscopy, x-ray diffraction, and Raman spectroscopy as a function of atomic Se/In flux ratio and growth temperature. Scanning transmission electron microscopy (STEM) confirms the 3R polytype of b-In2Se3 in films on both substrates with minor disorder associated with the 2H polytype at the interface. Indications of in-plane Se atom displacements characteristic of the 3R-b’-In2Se3 polytype were found by STEM, and second harmonic generation analysis in films on Al2O3(0001), but not in films on Si(111). Electrical transport measurements demonstrated locally varying anisotropic responses with the applied electric fields along different in-plane directions with some hysteresis associated with trapping of charges.