Investigation of MoS${}_2$-hydrogen interaction using in-situ X-ray diffraction studies

The present manuscript examines the significant effects of hydrogen (H) exposure on the structural properties of molybdenum disulfide (MoS) thin films through in-situ X-ray diffraction (XRD) analysis. Molybdenum (Mo) thin films were initially deposited using the electron beam (e-beam) deposition method and subsequently sulfurized via chemical vapor deposition (CVD) to obtain MoS thin films. The quality of the MoS films was optimized by varying the thickness of the Mo layer, sulfurization temperature, and the temperature of the Mo film. It was determined that crystalline MoS thin films with an optimal thickness of 20 nm can be achieved through sulfurization at 220 °C, while maintaining the Mo thin film at 600 °C. Pressure-dependent hydrogenation of the MoS thin films, as investigated by in-situ XRD, reveals an increase in crystallite size accompanied by a decrease in the relative intensity of the diffraction peaks with rising hydrogen pressure. Furthermore, a microstrain of approximately 6.3% is induced in the MoS films upon exposure to 1% and 10% hydrogen. Notably, the MoS thin films remain predominantly stable up to a hydrogen pressure of 400 mbar; however, they undergo abrupt transformations and become entirely amorphous when the hydrogen gas pressure is subsequently elevated to 800 mbar. These observations of hydrogen-induced crystalline-amorphous phase transformation in MoS not only enhance the understanding of the interactions between MoS and hydrogen but also have critical implications for the application of MoS thin films in various devices.