Sulfurization of planar MoO3 optical crystals: Enhanced Raman response and surface porosity

Abstract Surface properties of planar crystals can be controlled for multi-purpose application. In this regards, we demonstrate a successful MoO 3 planar crystal growth proposed for a wide tunability in surface characteristics. Such planar crystals are exposed systematically in sulfur gas at different temperatures. A large enhancement in Raman intensity was observed by sulfurization at 300 °C with the maximum of 46 times w.r.t. the non-sulfurized crystals due to surface oxygen vacancy. During sulfurization at higher temperatures, an MoS 2 phase was observed to form at the surface of the crystals. Moreover, systematic imaging of surface evolution and optical response with increasing sulfurization temperature show systematic increase in surface porosity, decrease in optical band gap together with significant crystal color changes. Our findings can open pathways towards the growth of planar crystals at large scales with tunable characteristics for application in the fields of optics, sensor and energy.