RF Magnetron Sputtered Tungsten Disulfide Films: Influence of Target Preparation, Deposition Parameters, and Storage Conditions on Thin Film Stoichiometry

ABSTRACT Sputtering of tungsten disulfide (WS 2 ) thin films at room temperature represents a significant challenge in terms of stoichiometry. Often, sulfur is lost during deposition and the resulting thin films contain many defects, due to the high energy impact from the plasma process. The target material is also affected by these phenomena. It has been demonstrated that the storage in ambient atmosphere results in oxidation of the films and the target. This study examines the impact of pre‐sputter time and deposition power on the chemical composition and structure of WS 2 thin films. The target was stored in atmospheric condition and in a dark ambient before mounting into deposition chamber. The impact of light irradiation was examined, with a focus on the chemical and structural modifications of the films. EDS was utilized to analyze the chemical compositions of target and films, while AFM, SEM, TEM and XRD were employed to examine the microstructure of the films depending on the deposition conditions. The thin films have a WS x O y composition with varying S‐ and O‐content. For low sputter power an increasing tendency for crystalline behavior at the surface along with a higher S‐content was observed, while films deposited at 80 W remain X‐ray amorphous.