Low-Temperature Growth of 2D-MoS2 Thin Films by Plasma-Enhanced Atomic Layer Deposition Using a New Molybdenum Precursor and Applicability to Gas Sensors

Abstract

Two-dimensional transition-metal dichalcogenides (2DTMDs) suchas molybdenum disulfide (MoS2) have received great attentionfor various applications. However, large-scale synthesis of high-quality2D TMDs remains a challenge. Atomic layer deposition (ALD) is a promisingdeposition method for synthesizing large-area 2D TMDs, but it showspoor film quality due to the narrow process temperature window causedby the low thermal stability of conventional precursors. In this study,a plasma-enhanced atomic layer deposition (PEALD) process utilizinga new cyclopentadienyl-based Mo precursor (r-cyclopentadienyldicarbonyl nitrosyl molybdenum, IM-02) was presented for synthesizingcrystalline MoS2 at a low growth temperature. IM-02 exhibitedexcellent thermal stability and suitability as an ALD precursor. Theresulting MoS2 thin films showed good uniformity and crystallinitywithout additional thermal treatment. Interestingly, the quality ofthe MoS2 film was further improved by exposure to H2S plasma, which increased crystallinity and reduced grainboundaries and surface defects, suppressing surface contaminationby carbon and oxygen in air. The resulting MoS2 thin filmswere highly selective for NO2 gas, with a response rateof about 50% at 100 ppm NO2 even at room temperature, indicatingtheir potential for use in gas sensors. These results suggest thePEALD process using IM-02 and H2S plasma as a promisingapproach for synthesizing high-quality MoS2 thin films,with potential applications in various fields.