Modification of the Electronic Transport in Atomically Thin WSe2 by Oxidation

Atomically thin tungsten diselenide (WSe2) is a promising 2D semiconductor for nanoelectronics and optoelectronics. Using UV ozone and low‐power O2 plasma treatments, it is demonstrated that the formation of WSe2(1−x)O2x (WSeyOx) leads to hysteretic behavior in vertical transport measurements and also enables to an improvement in the p‐type transfer characteristics in lateral transport measurements. The amount of oxidation correlates well with the resistive switch behavior in oxidized WSe2/graphene, and WSeyOx formation under the electrical contact of the horizontal devices leads to increased p‐branch on/off by 100×. In addition to its effect for residue removal, oxidation on field effect transistor channel also helps mitigate n‐type dominated transfer characteristics of WSe2 commonly seen on sapphire. It is demonstrated that light oxidation of WSe2 is a multifunctional post‐growth treatment that enables vertical resistive switch junctions, contact improvement, and continuous tuning of transistor transport properties. Atomically thin epitaxial WSe2 is oxidized by UV‐ozone exposure and O2 plasma at room temperature. The oxidation of WSe2 is found self‐limited. Atomic force microscopy, scanning tunneling microscopy/spectroscopy, X‐ray photoemission spectroscopy, z‐contrast scanning transmission electron microscopy experiments, and electrical measurements characterize the tungsten oxide (WO3−x)/WSe2. The non‐volatile switching phenomena and contact improvement found on WO3−x/WSe2 vertical and lateral devices are compared with their natural counterparts and discussed in detail.