Impact of Ar Flow Rates on Micro-Structural Properties of WS Thin Film by RF Magnetron Sputtering.

Tungsten disulfide (WS) thin films were deposited on soda-lime glass (SLG) substrates using radio frequency (RF) magnetron sputtering at different Ar flow rates (3 to 7 sccm). The effect of Ar flow rates on the structural, morphology, and electrical properties of the WS thin films was investigated thoroughly. Structural analysis exhibited that all the as-grown films showed the highest peak at (101) plane corresponds to rhombohedral phase. The crystalline size of the film ranged from 11.2 to 35.6 nm, while dislocation density ranged from 7.8 × 10 to 26.29 × 10 lines/m. All these findings indicate that as-grown WS films are induced with various degrees of defects, which were visible in the FESEM images. FESEM images also identified the distorted crystallographic structure for all the films except the film deposited at 5 sccm of Ar gas flow rate. EDX analysis found that all the films were having a sulfur deficit and suggested that WS thin film bears edge defects in its structure. Further, electrical analysis confirms that tailoring of structural defects in WS thin film can be possible by the varying Ar gas flow rates. All these findings articulate that Ar gas flow rate is one of the important process parameters in RF magnetron sputtering that could affect the morphology, electrical properties, and structural properties of WS thin film. Finally, the simulation study validates the experimental results and encourages the use of WS as a buffer layer of CdTe-based solar cells.