Tunability of Amorphous MoS₂ Thin Film Properties Through Pulsed KrF Laser Deposition Rate

In this study, we demonstrate how the physical properties of amorphous thin MoS_x films can be controlled through pulsed laser deposition conditions. We show that the sulfur content in thin MoS_x films can be specifically tuned from MoS₄ to MoS₂ by the laser fluence in the range of 1.3 to 20.4 J/cm² using a repetition rate of 1 Hz. Focusing on stoichiometric amorphous thin MoS₂ films, we further found that while the stoichiometry of MoS₂ is maintained at different repetition rates (1, 3, 5, and 10 Hz) of a pulsed KrF laser, X-ray photoelectron spectroscopy reveals a significant increase in the ratio of 1T'/2H structural units as the laser repetition rate increases. This structural shift is attributed to the increased adatom mobility and cumulative surface heating occurring at higher repetition rates, which favor the stabilization of the metastable 1T' phase while simultaneously promoting the desorption of excess polysulfides and surface molybdenum oxide impurities. Consequently, the optical parameters (refractive index and extinction coefficient) of amorphous thin MoS₂ films show a pronounced increase with laser frequencies ranging from 1 to 10 Hz. Furthermore, we show that higher photothermal conversion is systematically associated with an increased extinction coefficient. These findings are expected to advance both fundamental research and application-driven studies, including photothermal cancer therapy, sterilization, and disinfection.