Photoresponse dependence of WS2/Pt Schottky junction on the features of Pt nanoparticles

Abstract

In this study, we delve into the photoresponsive characteristics of Schottky junctions fabricated through the deposition of Pt nanoparticles (NPs) onto multilayer WS2 sheets grown via chemical vapor deposition. Our analysis encompasses a comprehensive examination of the junction's morphology, structural attributes, and photophysical behavior. Of particular interest is the intricate relationship between the efficiency of hot electron injection and the specific properties of the Pt NPs, namely their density and size. Our findings reveal that Pt NPs effectively extinguish the photoluminescence of WS2, an outcome attributed to the efficient separation of photo-generated electron-hole pairs facilitated by the WS2/Pt Schottky junction. This process, however, does not significantly alter the electronic configuration of WS2. The modulation of exciton radiative decay is shown to be contingent upon the size and density of the Pt NPs, with an average size of 1.27 nm and density of 0.82/nm² yielding the most rapid exciton decay rate of 1.15 ns. This pronounced dependence of exciton dynamics on Pt NPs features can be attributed to the quenching effect exerted by densely packed Pt NPs, which also plays a pivotal role in the injection of hot electrons from Pt to WS2. The enhancement of internal photoemission is evidenced by a pronounced increase in near-infrared photoresponse within the 800–1000 nm range. Furthermore, the optimization of Pt NPs features leads to superior photoresponsive performance in the WS2/Pt Schottky junctions, manifesting as a responsivity of 280 A/W and a detectivity of 7.77 × 1012 Jones at a wavelength of 850 nm. This photoresponse's dependence on Pt NPs features underscores the dual mechanism governing photodetection in the WS2/Pt Schottky junction: a synergistic interplay between hot electron injection and the separation of photo-excited electron-hole pairs.