Epitaxial films of the 3D semiconductor CdS on the 2D layered substrate MX2 prepared by Van der Waals epitaxy

The growth of epitaxial CdS (wurtzite-type) films on the Van der Waals (0001) surface of the layered compound semiconductors WSe2 and MoTe2 is presented. The film and the heterointerfaces are investigated by electron diffraction, photoelectron spectroscopy, and transmission electron microscopy (TEM). At room temperature and above, the CdS sticking coefficient on Van der Waals surfaces is very low. Film growth could only be achieved by decreasing the substrate temperatures to 170 K for the initial deposition steps. On WSe2, textured films of CdS are grown with the c-axis parallel to the substrate c-axis. The crystallites of mean diameter 200 A have random azimuthal orientation. On MoTe2 the CdS films are aligned with their c- and a-axis parallel to the respective axes of the substrate.