Growth of Transition Metal Dichalcogenide Layers from Corresponding Metal Powders

In a method provided herein for forming a chalcogenide film on a substrate, an elemental solid is exposed to a hydrogen halide gas in a heated reaction environment at a temperature at which the hydrogen halide gas promotes the elemental solid to evolve into an elemental halide-based gas. The elemental halide-based gas is then exposed to a chalcogen gas provided in the heated reaction environment, at a temperature at which the elemental halide-based gas is reactive with the chalcogen gas to produce a solid chalcogenide reaction product. A substrate is provided in the heated reaction environment for deposition thereon of a solid film of the solid chalcogenide reaction product that results from exposure of the elemental halide-based gas to the chalcogen gas in the heated reaction environment.