Magnetron sputtered WS2; Optical and structural analysis

Abstract

Remarkable properties of graphene have renewed interest in inorganic, Transition Metal Dichalgogenits (TMDC) due to unique electronic and optical properties. TMDCs such as MoS2, MoSe2, WS2 and WSe2 have sizable bandgaps that change from indirect to direct in single layers, allowing applications such as solar cells, transistors, photodetectors and electroluminescent devices in which the graphene is not actively used. So, fabrication and analysis of these films are important for new generation devices. In this work, polycrystalline WS2 films were grown by radio frequency magnetron sputtering (RFMS) on different substrates like n-Si(100), n-Si(111), p-Si(100), glass and fused silica. Structural, morphological, optical and electrical properties were investigated as a function of film thickness and RF power. From XRD analysis, signals from planes of (002), (100), (101), (110), (008) belong to the hegzagonal WS2 were obtained. Raman spectra of the WS2 show that there are two dominant peaks at ∼351 cm-1 (in-plane phonon mode) and ∼417 cm-1 (out-of-plane phonon mode). XPS analysis of the films has shown that binding energy and the intensity of tungsten 4f shells shifts by depending on the depth of the films which might be due to the wellknown preferential sputtering.