Growth of Few-Layer 2H-MoS₂ by CVD: Effect of Synthesis Time and Precursor Distance Using a Mineral Precursor

Abstract

Few-layer 2H-MoS₂ flakes were synthesized by chemical vapor deposition (CVD) on SiO₂/Si(100) substrates using a low-cost, impure molybdenite mineral powder (~31% impurities) as the Mo precursor, with sulfur supplied separately from a second furnace. Growth was carried out at 650 °C under Ar/H₂ flow, varying the reaction time (10–40 min) and the distance between the precursor sources (14.7–35.7 cm). No crystalline growth was observed for reaction times below 20 min. SEM images revealed polygonal flakes, including triangles, tetragons, pentagons, and hexagons, with lateral sizes ranging from 0.3 to 3 μm. The flakes grew laterally and coalesced with increasing reaction time, without achieving full substrate coverage. Raman spectroscopy revealed flakes consisting of 2–4 layers, with their thickness governed by the precursor distance, as larger separations resulted in thinner flakes. XRD confirmed the formation of the 2H-MoS₂ phase with preferential orientation along the (002) plane. XPS confirmed Mo–S bonding through the characteristic Mo 3d₅/₂ and S 2p₃/₂ binding energies, together with a high overall sample purity. These findings demonstrate that a low-cost, impure mineral precursor can yield good-quality, thickness-controlled MoS₂ flakes, providing an economical route for the synthesis of two-dimensional MoS₂.

Keywords: Chemical vapor deposition; mineral molybdenite; two-dimensional materials