A New Synthetic Method for HfS2Thin Films Using MOCVD

Hafnium disulfide (HfS<inf>2</inf>) is expected to surpass MoS<inf>2</inf> and WS<inf>2</inf> as a two-dimensional (2D) semiconductor, with the added advantage that its native oxide, HfO<inf>2</inf>, is a widely used high-k dielectric. Unlike MoS<inf>2</inf> and WS<inf>2</inf>, which are generally synthesized by metal–organic chemical vapor deposition (MOCVD) for semiconductor applications, HfS<inf>2</inf> has not yet been grown by this method, probably due to a lack of suitable precursors for depositing thin, uniform, and stoichiometric films. Here, we introduce two nitrogen-coordinated hafnium precursors, [Hf(TMSAEDMA)(NMe<inf>2</inf>)<inf>3</inf>] 1 and [Hf(TMSAEDMA)(NEtMe)<inf>3</inf>] 2, derived from the functionalized ligand system N-trimethylsilylamino-ethane-N′,N′-dimethylamine (TMSAEDMA). Both complexes exhibit adequate volatility and high reactivity toward elemental sulfur, enabling MOCVD under moderate, H<inf>2</inf>S-free conditions. Using precursor 1, crystalline HfS<inf>2</inf> was deposited, confirmed by structural and compositional analyses. X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) revealed rapid surface oxidation to HfO<inf>2</inf> and HfO<inf>x</inf>S<inf>y</inf>, naturally forming heterostructures relevant for transistor applications. For electrical characterization, HfS<inf>2</inf> films were directly deposited on interdigitated electrode (IDE) structures. Their conductivity was evaluated both with the native oxide present and after capping with a thin ZnS layer, with both configurations preserving the conductivity. This work establishes the first MOCVD method for high-quality HfS<inf>2</inf>, identifies 1 as a versatile precursor for chalcogenide growth, and provides detailed insights into oxidation pathways, highlighting the material’s potential for next-generation semiconductor devices.