Vertically-oriented MoS2 nanosheets for nonlinear optical devices

Abstract

Transition metal dichalcogenides such as MoS₂ represent promising candidates for building blocks of ultra-thin nanophotonic devices. For such applications, vertically-oriented MoS₂ (v-MoS₂) nanosheets could be advantageous as compared to conventional horizontal MoS₂ (h-MoS₂) given that their inherent broken symmetry would favor an enhanced nonlinear response. However, the current lack of a controllable and reproducible fabrication strategy for v-MoS₂ limits the exploration of this potential. Here we present a systematic study of the growth of v-MoS₂ nanosheets based on the sulfurization of a pre-deposited Mo–metal seed layer. We demonstrate that the sulfurization process at high temperatures is driven by the diffusion of sulfur from the vapor–solid interface to the Mo seed layer. Furthermore, we verify an enhanced nonlinear response in the resulting v-MoS₂ nanostructures as compared to their horizontal counterparts. Our results represent a stepping stone towards the fabrication of low-dimensional TMD-based nanostructures for versatile nonlinear nanophotonic devices.