Selective oxidation of metallic contacts for localized chemical vapor deposition growth of 2D-transition metal dichalcogenides

Abstract

Chemical vapor deposition (CVD) is the most common fabrication method for transition metal dichalcogenides (TMDs) where direct chemical vapor phase reaction between an oxide transition metal and chalcogen powder results in formation of high-quality crystals of TMDs. However, in this method the nucleation is often random with incomplete nucleation and non-uniform thickness. In this work we studied the formation of a localized transition metal oxide which resulted in controllable growth of mono- to few-layer MoS2 around the formed oxide region. Bulk molybdenum patterns were irradiated with a 532 nm continuous wave laser creating a localized hot-spot which, under ambient conditions, resulted in the formation of molybdenum oxide. The characteristics of the subsequent MoS2 growth depended on the type and thickness of the MoOx which was determined by the power and duration of laser exposure. The resulting MoOx and MoS2 growth around the localized oxide regions were investigated by Raman and photoluminescence spectroscopy. Our studies have shown that exposing bulk molybdenum patterns to 10 mW of laser power for about 2s results in the minimal formation of MoO2 which coincides with high quality mono- to few-layer MoS2 growth.