Low-Temperature Chemical Vapor Deposition of Zirconium(IV) Sulfide Thin Films

The transition metal dichalcogenide zirconium disulfide absorbs visible light, and its monolayers can have exceptionally large carrier mobilities. Integrating TMDC materials into wafer-based devices will likely require deposition methods operating below 400 °C. Chemical vapor deposition (CVD) may offer one such route, because it is suitable for large substrate areas and complex substrate geometries. However, current CVD methods deposit ZrS2 above 400 °C, typically from ZrCl4 and sulfur. Guided by thermochemical calculations that showed the reaction between hydrogen sulfide and tetrakis(dimethylamido)zirconium(IV) would be more favorable, we demonstrate low-temperature CVD using these compounds. Film deposition proceeds rapidly at 150-350 °C, producing stoichiometric, polycrystalline ZrS2. Films can grow at rates >100 nm/min, although slower growth increases the film crystallinity and decreases C and N impurities. At substrate temperatures above 250 °C, the film morphology transitions from densely packed small grains to larger, more loosely packed vertical sheets. In an excess of H2S, decreasing the Zr(NMe2)4 partial pressure can suppress the growth of these plates. Resistivities of product films are within 1-3 orders of magnitude of single crystal data. Optical properties are consistent with previously reported films of ZrS2, suggesting this route may offer a method for integrating ZrS2 into thermally sensitive devices.