Investigation of MoS2-hydrogen interaction using in-situ X-ray diffraction studies

Abstract

The present manuscript examines the significant effects of hydrogen (H₂) exposure on the structural properties of molybdenum disulfide (MoS₂) 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 MoS₂ thin films. The quality of the MoS₂ 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 MoS₂ 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 MoS₂ 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 MoS₂ films upon exposure to 1% and 10% hydrogen. Notably, the MoS₂ 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 MoS₂ not only enhance the understanding of the interactions between MoS₂ and hydrogen but also have critical implications for the application of MoS₂ thin films in various devices.