Raman Laser-Induced Structural Modification in CVD-Grown Monolayer MoS2 for Multi-Purposed Nanofabrication

Abstract

Molybdenum disulfide (MoS2) has been extensively explored to be utilized as an electronic material in a variety of device applications. In particular, the tunability of MoS2 enhances its electrical properties making it an intriguing candidate for field-effect transistors (FETs), while also extending beyond electrical properties to structural phase engineering. Laser-induced modifications, particularly with Raman lasers, offer a straightforward method to modulate materials via thermal processes with precise patterning control and energy-level flexibility. However, most studies on the modification of MoS2 have focused on multilayered structures or have been conducted under low-power laser conditions, leaving the feasibility of structural modifications in monolayer MoS2 elusive. In this study, we fundamentally elucidated the effects of high-power Raman laser irradiation on the surface of chemical vapor deposition (CVD)-grown monolayer MoS2 under ambient conditions and uncovered the underlying mechanisms of laser-induced modifications by applying intense photon energy with highly interactive reactions. Our results revealed both etching and deposition phenomena in two discernible regions, and it can be demonstrated by intensity regimes based on the spatial distribution of laser irradiance within the laser-irradiated spot. Furthermore, phase transition was found to be inhibited due to the promoted oxidation and the deposition of hydrogenated amorphous carbon (a-C:H), and p-type doping was observed, likely occurring in the region beneath the a-C:H deposition as substitutional doping on the 2H phase of MoS2. To compare the thermal effects, MoS2 modifications were further analyzed using simplified heat transfer estimations. These findings deepen our understanding of how Raman laser irradiation modifies MoS2 under ambient conditions, providing guidelines for optimizing its modification processes.