Synthesis of two-dimensional MoO₂ nanoplatelets and its multistep sulfurization into MoS₂

To control the growth of layered two-dimensional structures, such as transition metal dichalcogenide materials or heterostructures, understanding the growth mechanism is crucial. Here, we report the synthesis of ultra-thin MoO2 nanoplatelets through the sublimation of MoO3. Rhombus MoO2 nanoplatelets with the P2(1)/c space group were characterized using various microscopic and spectroscopic techniques. Introducing sulfur sources into the chemical vapor deposition system also leads to the formation of monoclinic MoO2 nanoflakes due to the incomplete sulfurization of MoO3. With a gradual increase in the vapor concentration of sulfur, MoO3 undergoes stepwise reduction into MoS2/MoO2 and eventually into MoS2. Additionally, utilizing MoO2 as a precursor for Mo sources enables the formation of monolayer MoS2 single crystals. This work provides an effective approach for growing MoO2 nanoplatelets and elucidates the mechanism behind the stepwise sulfurization of MoO3.