Effect of magnetron sputtering parameters and stress state of W film precursors on WSe₂ layer texture by rapid selenization

Tungsten diselenide (WSe₂) film was obtained by rapid selenization of magnetron sputtered tungsten (W) film. To prevent WSe₂ film peeling off from the substrate during selenization, the W film was designed with a double-layer structure. The first layer was deposited at a high sputtering-gas pressure to form a loose structure, which can act as a buffer layer to release stresses caused by WSe₂ growth. The second layer was deposited naturally on the first layer to react with selenium vapour in the next step. The effect of the W film deposition parameters(such as sputtering time, sputtering-gas pressure and substrate bias voltage)on the texture and surface morphology of the WSe₂ film was studied. Shortening the sputtering time, increasing the sputtering-gas pressure or decreasing the substrate bias voltage can help synthesize WSe₂ films with more platelets embedded vertically in the matrix. The stress state of the W film influences the WSe₂ film texture. Based on the stress state of the W film, a model for growth of the WSe₂ films with different textures was proposed. The insertion direction of the van der Waals gap is a key factor for the anisotropic formation of WSe₂ film.