Tuning the electrical properties of WSe ₂ via O ₂ plasma oxidation: towards lateral homojunctions

Abstract

Controlled oxygen plasma exposure of multilayer WSe2 can modulate the carrier type of WSe2 field effect transistors. XPS shows with increased exposure, the top WSe2 layer(s) oxidizes to amorphous WO(x−3) layer-by-layer with a high degree of controllability as both single or 2 layers can be transformed. A systematic study of Raman and photoluminescence signatures clearly demonstrate the processing times necessary to selectively oxidized the top 1 or 2 layers of exfoliated WSe2 flakes. WSe2 devices exposed in the channel regions experience an increase in p-type conduction and large layer-dependent n-type suppression. Devices exposed in the contact region prior to metalization show slight increases of both p-type and n-type conduction. Devices made on flakes, which were completely exposed show suppression of p-type conduction and layer dependent suppression of n-type conduction. Based on these results we were able to fabricate self-rectifying lateral p–n homojunctions with rectification ratios exceeding 300.