Vapor-Liquid-Solid Growth of Monolayer MoS2 Nanoribbons

TL;DR

This paper demonstrates a novel vapor-liquid-solid (VLS) method for growing monolayer MoS2 nanoribbons, resulting in highly crystalline structures with potential applications in advanced device architectures.

Contribution

First demonstration of VLS growth of monolayer MoS2 nanoribbons using molten Na-Mo-O droplets, enabling controlled ribbon-shaped 2D material synthesis.

Findings

Produced straight and kinked MoS2 ribbons with well-defined orientations

Ribbons exhibit homoepitaxial growth with 2H- or 3R-type stacking

Growth mode involves molten droplet-mediated crawling motion

Abstract

Chemical vapor deposition (CVD) of two-dimensional (2D) materials such as monolayer MoS2 typically involves the conversion of vapor-phase precursors to a solid product in a process that may be described as a vapor-solid-solid (VSS) mode. Here, we report the first demonstration of vapor-liquid-solid (VLS) growth of monolayer MoS2 yielding highly crystalline ribbon-shaped structures with a width of a few tens of nanometers to a few micrometers. The VLS growth mode is triggered by the reaction between molybdenum oxide and sodium chloride, which results in the formation of molten Na-Mo-O droplets. These droplets mediate the growth of MoS2 ribbons in the "crawling mode" when saturated with sulfur on a crystalline substrate. Our growth yields straight and kinked ribbons with a locally well-defined orientation, reflecting the regular horizontal motion of the liquid droplets during growth. Using atomic-resolution scanning transmission electron microscopy (STEM) and second harmonic generation (SHG) microscopy, we show that the ribbons are homoepitaxially on monolayer MoS2 surface with predominantly 2H- or 3R-type stacking. These findings pave the way to novel devices with structures of mixed dimensionalities.