Phase control and Young’s modulus of tungsten thin film prepared by dual ion beam sputtering deposition

In this letter, tungsten films of varying thickness from similar to 20 nm to similar to 80 nm were prepared at different deposition temperature by Dual ion beam sputtering deposition (DIBSD) method. The influence of thickness and deposition temperature on the films phase, microstructure and Young's modulus was studied briefly. The experiments prove that a double-layer structure, formation takes place i.e. beta phase tungsten layer (low crystallinity) forms adjacent to the substrate and alpha tungsten phase layer (high crystallinity) forms above beta phase. The increase in both the thickness and deposition temperature promotes the transformation from beta phase to alpha phase which initiates from the interface between two phases. There is a critical thickness of similar to 20 nm below which the film is a pure beta phase, and the minimum thickness of forming pure alpha phase is affected by the deposition temperature, with 74 nm at 450 degrees C, and 58 nm at 600 degrees C. Furthermore, the decrease Young's modulus of the tungsten film is ascribed to the formation of beta phase which possesses low crystallinity with low density. (C) 2018 Author(s).