Influence of Surface Roughness on the Photoresponse of WS₂/Pt Schottky Junction

The surface roughness of multilayer WS₂ grown by chemical vapor deposition and modified with platinum nanoparticles (Pt NPs) was tuned by ultraviolet ozone treatment with the durations ranging from 0 to 4 min. The surface roughness (S_a) reached a maximum value of approximately 14 nm when the treatment time was 2 min, primarily attributed to the formation of amorphous WO_x due to the oxidation of the WS₂ surface by ultraviolet ozone. As the treatment duration was extended, the underlying fresh layers of multilayer WS₂ were exposed, mitigating the aforementioned oxidation effect. Characterization results demonstrated that the WS₂/Pt Schottky junction treated with ultraviolet ozone for 2 min exhibited superior photoresponse performance in the wavelength range of 400—900 nm, particularly at 750 nm in the near-infrared region, with a responsivity as high as 18 A/W, representing a nearly 60% improvement compared to the untreated WS₂/Pt Schottky junction. This enhanced performance can be primarily attributed to the increased surface roughness of the WS₂ in the WS₂/Pt Schottky junction induced by ultraviolet ozone treatment. The increased roughness not only facilitated the separation of photo-generated electron-hole pairs but also enhanced the hot electron injection from Pt to WS₂.