Large-area, thermally-sulfurized WS₂ thin films: control of growth direction and use as a substrate for GaN epitaxy

We present a detailed study of the influence of metal seed thickness, amount of sulfur, sulfurization time and temperature on the morphology of large-area WS2 thin films prepared by sulfurization of electron-beam evaporated tungsten layers. We show how preferably horizontally or vertically oriented films can be achieved. The WS2 films with horizontal morphology were used as nearly lattice-matched substrates for the growth of GaN layers by MOVPE. While epitaxial films of GaN could be demonstrated, the thin-film WS2 layers show a enhanced propensity for degradation in the strongly reducing and high-temperature MOVPE growth environment.