Growth of phase-pure β-NiS thin films via single-source MOCVD and enhanced substrate interaction for electrocatalytic hydrogen evolution

Nickel monosulfide (NiS) is a promising material in electrochemical energy conversion and storage owing to its high conductivity, chemical stability, and cost-effectiveness. However, achieving high-quality, phase-pure, and homogeneous NiS thin films remains challenging. In this study, we synthesized phase-pure β-NiS films on silicon dioxide/silicon substrates using the single-source precursor bis(N,N-dimethylamino-2-methylpropane-2-thiolato)nickel(II) (Ni(dmampS)₂) via metal organic chemical vapor deposition (MOCVD). The unique distorted square-planar structure of Ni(dmampS)₂ facilitates favorable interactions with the substrate surface, enhancing adsorption and enabling uniform film growth at relatively low temperatures. Consequently, we obtained highly crystalline films with minimal secondary phases or impurities. Electrochemical measurements further demonstrated that β-NiS films exhibit excellent catalytic activity and stability for the hydrogen evolution reaction under acidic conditions. This study highlights the potential of single-source precursor MOCVD as a scalable method for producing high-quality β-NiS thin films.