Enabling high quality dielectric passivation on Monolayer WS2 using a sacrificial Graphene Oxide template

Abstract Two-dimensional transition metal dichalcogenides (2D TMDC’s) hold a wide variety of applications, among which microelectronic devices. However, various challenges hinder their integration e.g., good dielectric deposition on the 2D TMDC surface. In this work, a sacrificial, Graphene oxide (GrO)-based buffer layer is used to 1) serve as a passivation layer, protecting the underlying 2D TMDC (WS 2 ) and 2) act as a nucleation layer, enabling uniform dielectric (HfO 2 ) growth. A Graphene layer is transferred on monolayer WS 2 , after which polymeric transfer residues are cleaned via a combination of wet- and dry treatments. Next, the cleaned Graphene is functionalized via a dry UV/O 3 oxidative exposure. It is shown that the Graphene UV/O 3 oxidation rate is substrate dependent and proceeds slower when Graphene is transferred on WS 2 compared to SiO 2 , due to UV-light induced, ultrafast charge transfer between the Graphene and WS 2 monolayer. The carbon-oxygen groups formed on Graphene’s basal plane act as nucleation sites in a subsequent HfO 2 atomic layer deposition process, achieving a smoother dielectric layer in comparison to direct deposition on bare WS 2 . Finally, by means of a GrO FET device, it is shown that the GrO nucleation layer does not compromise the device transport characteristics i.e., will not give rise to significant leakage currents in a 2D heterostack device.