Few-Layered MoS2 and MoOx Materials Using Wafers of Alternated MoO3 and S Foils as Catalysts: Chemical Vapor Deposition Experiments

Abstract

A novel one-step chemical vapor deposition approach is introduced for synthesizing high-density vertical molybdenum disulfide (MoS₂) nanoflakes and molybdenum dioxide (MoO₂) structures using pelletized MoO₃/S precursors and abrupt thermal cycling. Unlike conventional multi zone sulfurization methods, the process compacts alternating MoO₃/S/MoO₃/S/MoO₃ layers into 10-ton pressure pellets, ensuring uniform precursor distribution and phase selectivity. Rapid thermal cycling, with an abrupt transition from 25 to 750 °C, followed by rapid cooling after a 5-min deposition under an Ar/H₂ flow, critically influences the crystallization dynamics. A sulfur-to-MoO₃ molar ratio of 2:1 promotes vertical MoS₂ growth (≈100 flakesµm⁻²), whereas a 1.16:1 ratio induces MoO₂ formation with elongated hexagonal morphologies, sizes between (0.70–1.36 µm). This scalable synthesis method offers a reproducible and efficient alternative for nanomaterial fabrication, allowing the production of vertical MoS₂ flakes and enlarged MoO₂ for transfer onto various substrates, as well as uniform vertical structures directly deposited on the substrate. The findings offer key insights into precursor structuring and thermal modulation for the tailored synthesis of 2D materials with applications in catalysis, energy storage, and nanoelectronics.