Low defect density in MoS monolayers grown on Au(111) by metal-organic chemical vapor deposition.

Monolayers of transition metal dichalcogenides (TMDs) possess high potential for applications in novel electronic and optoelectronic devices and therefore the development of methods for their scalable growth is of high importance. Among different suggested approaches, metal-organic chemical vapor deposition (MOCVD) is the most promising one for technological applications because of its lower growth temperature compared to the most other methods, e.g., conventional chemical vapor or atomic layer deposition (CVD, ALD). Here we demonstrate for the first time the epitaxial growth of MoS monolayers on Au(111) by MOCVD at 450 °C. We confirm the high quality of the grown TMD monolayers down to the atomic scale using several complementary methods. These include Raman spectroscopy, non-contact atomic force microscopy (nc-AFM), X-ray photoelectron spectroscopy and scanning tunneling microscopy (STM). The topographic corrugation of the MoS monolayer on Au(111), revealed in a moiré structure, was measured as ≈20 pm by nc-AFM. The estimated defect density calculated from STM images of the as-grown MoS monolayers is in the order of 10 vacancies/cm. The defects are mainly caused by single sulfur vacancies. Our approach is a step forward towards the technologically relevant growth of high-quality, large-area TMD monolayers.