Effect of substrate temperature on properties of WS thin films.

The WS thin films were deposited on glass substrates with RF magnetron sputtering using a WS target to study the effect of substrate temperature (25, 100, 200, and 300 °C) on their properties. In this study, we investigated the morphological, structural, and optical characteristics of the films. FESEM images show that all the samples consist of nanoparticles, with the exception of the film deposited at 200 °C, which uniquely exhibited a nanosheet morphology. The AFM spectrum of the samples determined that the sample with a substrate temperature of 200 °C had the highest roughness, which confirms the results obtained from the FESEM images of the samples. The XRD patterns of all the thin films showed the preferred orientation (104) related to the WS phase, and among the samples, the film deposited at 200 °C exhibited the largest crystallite size and the lowest strains. Also, no additional peak related to the oxide phase was observed in XRD and Raman spectra. The band gap of the 200 °C sample was lower than the other samples, and because it has a larger crystal size, this can be caused by quantum confinement. At 200 °C, the resistivity reached its highest value, accompanied by a significant decrease in carrier mobility and concentration, likely due to structural disorder and increased porosity in this sample.