Location-selective growth of two-dimensional metallic/semiconducting transition metal dichalcogenide heterostructures

Abstract

An electrical contact between metallic electrodes and semiconductors is critical for the performance of electronic and optoelectronic devices. Two-dimensional (2D) transition metal dichalcogenides (TMDs) contain semiconducting, metallic and insulating material members, which enables the fabrication of highly integrated electronic devices fully based on 2D TMDs. However, location-selective synthesis of metallic/semiconducting heterostructures by a chemical vapor deposition (CVD) method has rarely been reported. In this study, a two-step CVD method was applied to fabricate 2D metallic/semiconducting heterostructures. Semiconducting WS₂ was first synthesized and served as the template for the following CVD growth of metallic NbS₂. In the growth process, NbS₂ flakes selectively nucleate at the edges of WS₂ monolayers, thus resulting in the formation of NbS₂ islands circling around the WS₂ monolayers. The as-grown NbS₂/WS₂ heterostructure was further systematically characterized by Raman spectroscopy, atomic force microscopy (AFM) and scanning transition electron microscopy (STEM). The NbS₂ layers epitaxially grown on the WS₂ monolayers exhibit a 3R phase and there was no discernible lattice strain in the NbS₂/WS₂ van der Waals (vdW) heterostructure. The growth of the metallic/semiconducting 2D heterostructures could benefit the nanoelectronic device fabrication and provide a platform for the 2D contact resistance study.