Non-linear thermo-optical properties of WS2 and Au/WS2 Schottky-type nano/hetero-junctions

Tungsten disulfide (WS2) nanoflakes are synthesized by thermal chemical vapor deposition on a Si/SiO2 sub-strate. Subsequently, WS2 is anchored by Au nanostructures to form Au/WS2 Schottky-type nano/hetero-junc-tions (Au/WS2 NHs), in various gold molar ratios of 1% and 10%, using DC magnetron sputtering. The crystalline structure, surface morphology and optical properties of the samples are investigated by X-ray diffraction, field emission scanning electron microscopy, UV-visible and Raman spectroscopy, respectively. UV-visible spectra reveal the reduction of absorption rate in terms of Au abundance. According to Raman spectra, there is a notable red shifting for A(1g) and E-2g(1) peaks and the elevation of A(1g) to E-2g(1) intensity ratio after Au anchoring. In addition, the Z-scan technique measures the corresponding nonlinear thermo-optical properties indicating a change over from self-focusing to self-defocusing modes in favor of Au/WS2 nanoflakes.