HIGHLY ORIENTED WSE2 THIN-FILMS PREPARED BY SELENIZATION OF EVAPORATED WO3

Thin films of WSe2 were prepared by high temperature selenization of vacuum evaporated WO3 films on quartz in an open tube furnace. The films were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and optical absorption. They were found to consist of the hexagonal 2H phase. It was established that the substrate has a critical role in the growth process. A thin Ni, or Ni-Cr intermediate layer significantly accelerates the crystallization resulting in larger crystallite size compared with the WSe2 films grown on quartz substrate only. Also films prepared on Ni/quartz or Ni-Cr/quartz substrates were found to be predominantly oriented with their c-axis perpendicular to the substrate (perpendicular-to c). Raising the reaction temperature led to an improved crystallinity and perpendicular c texture. These films exhibit optical properties similar to those of a single crystal.