Promoter-Free Synthesis of Wafer-Scale Monolayer MoS ₂ for Visible to Near-Infrared Photodetection

Atomically thin two-dimensional molybdenum disulfide (MoS₂) has emerged as a promising semiconductor for next-generation optoelectronic applications. While chemical vapor deposition (CVD) enables large-area monolayer growth, achieving high-quality and reproducible synthesis without catalysts or promoters remains a critical challenge as common additives such as NaCl or oxygen can undesirably modify the material properties. In this study, we report the successful batch production of high-quality monolayer MoS₂ films on 2-in. sapphire wafers using a promoter-free CVD approach. By systematically optimizing the growth parameters and precisely controlling the sulfur-to-MoO₃ ratio, particularly the amount of sulfur vapor supplied, we realized additive-free synthesis on a wafer-scale by using a dual-source delivery system with an inner quartz tube configuration. Thermodynamic modeling confirms that separating the MoO₃ and sulfur pathways improves vapor stability, suppresses intermediate phases, and ensures a controlled synthesis. Microscopy, spectroscopy, and electrical measurements confirm the synthesis of highly crystalline monolayer MoS₂ with excellent wafer-scale uniformity and reproducibility. Photodetector arrays fabricated from the films exhibited outstanding performance: statistical analysis of 63 devices (within the 10-90% performance range) demonstrated a responsivity of ∼5.72 A/W (±2.9 A/W), a superior detectivity of ∼1.53 × 10¹² Jones, and an external quantum efficiency of ∼1687% at 450 nm under ambient conditions. Additionally, the devices also showed excellent long-term operational stability. Our method offers a cost-effective, additive-free, and scalable route to produce high-quality MoS₂ toward future optoelectronics.