Effects of UV ozone treatment on the photoresponse of the Pt nanoparticles decorated WS2

Chemical vapor deposition (CVD)-grown and Pt nanoparticles (NPs) decorated multilayer WS 2 is treated by ultraviolet (UV) ozone for the modification of the surface roughness to realize the enhanced hot carriers injection via the internal photoemission (IPE). The morphology, structure and photophysical properties as well as the dependence of the photoresponse on the UV ozone treatment are investigated. The UV ozone treatment demonstrates obvious effect on the WS 2 surface roughness (S a ), which reaches the maximum around 14 nm after 2 min exposure and subsequently decrease with the extension of treatment duration. UV ozone treatment also leads to obviously diminished photoluminescence (PL) and shortened excitons lifetime for bare WS 2 while its influence on the electronic structure is negligible. The diminished PL, shortened PL decaying lifetime and increased S a are all originated from the formation of WO x due to the consumption of top WS 2 layer by the severe oxidation , and such effects will be greatly alleviated when the fresh and undisturbed underlying WS 2 layer appears with the treatment duration extended to 4 min. The 2 min UV ozone treated WS 2 /Pt exhibits optimal wide spectrum photoresponse (400–900 nm) with the near infrared (NIR) responsivity around 18 A/W at 750 nm, about 60 % higher compared to that of untreated one while the 4 min overtreated WS 2 /Pt demonstrates much deteriorated photoresponse. Such behavior can be ascribed to the enhanced hot electrons injection from Pt to WS 2 due to the formation of rough Schottky contact as well as the separation of photo-excited electron-hole pairs by Schottky junction. Our study proves that the S a is a key factor not only for the exciton dynamics but also for the hot electron injection from Pt to WS 2 . • The influence of ultraviolet (UV) ozone treatment on photophysical and photoresponse properties of WS 2 /Pt nanoparticles (NPs) investigated. • The optimal UV ozone treatment time observed with wide spectrum photoresponse (400–900 nm). • 60 % higher responsivity at 750 nm ascribed to the enhanced hot electrons injection from Pt to WS 2 due to the rough Schottky contact .