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

Two-dimensional transition-metal dichalcogenides (2D TMDs) such as molybdenum disulfide (MoS 2 ) have received great attention for various applications. However, large-scale synthesis of high-quality 2D TMDs remains a challenge. Atomic layer deposition (ALD) is a promising deposition method for synthesizing large-area 2D TMDs, but it shows poor film quality due to the narrow process temperature window caused by the low thermal stability of conventional precursors. In this study, a plasma-enhanced atomic layer deposition (PEALD) process utilizing a new cyclopentadienyl-based Mo precursor ( r -cyclopentadienyl dicarbonyl nitrosyl molybdenum, IM-02) was presented for synthesizing crystalline MoS 2 at a low growth temperature. IM-02 exhibited excellent thermal stability and suitability as an ALD precursor. The resulting MoS 2 thin films showed good uniformity and crystallinity without additional thermal treatment. Interestingly, the quality of the MoS 2 film was further improved by exposure to H 2 S plasma, which increased crystallinity and reduced grain boundaries and surface defects, suppressing surface contamination by carbon and oxygen in air. The resulting MoS 2 thin films were highly selective for NO 2 gas, with a response rate of about 50% at 100 ppm NO 2 even at room temperature, indicating their potential for use in gas sensors. These results suggest the PEALD process using IM-02 and H 2 S plasma as a promising approach for synthesizing high-quality MoS 2 thin films, with potential applications in various fields.