Highly Conductive Group VI Transition Metal Dichalcogenide Films by Solution-Processed Deposition

A new soluble synthetic route was developed to fabricate thin films of layered structure transition metal dichalcogendies, MoS₂ and WS₂. High-quality thin films of the dichalcogenides were prepared using new soluble precursors, (CH₃NH₃) ₂MS₄ (M = Mo, W). The precursors were dissolved in organic solvents and spun onto substrates via both single- and multistep spin coating procedures. The thin films were formed by the thermal decomposition of the coatings under inert atmosphere. Structural, electrical, optical absorption, thermal, and transport properties of the thin films were characterized. Surface morphology of the films was analyzed by atomic force microscopy and scanning electron microscopy. Highly conductive and textured n-type MoS₂ films were obtained. The measured room temperature conductivity ∼50 Ω ^-1 cm^-1 is substantially higher than the previously reported values. The n-type WS₂ films were prepared for the first time using solution-processed deposition. WS₂ displays a conductivity of ∼6.7 Ω^-1 cm^-1 at room temperature.