Low-temperature growth of ultrathin and epitaxial MoC nanosheets a vapor-liquid-solid process.

Due to the unique physical and chemical properties, transition metal carbides (TMCs) have many potential applications in the fields of energy conversion and catalysis. Chemical vapor deposition (CVD) is a promising method to synthesize TMCs. However, spatially inhomogeneous supply of transition metal precursor vapor in the normal CVD process generally leads to poor control of the morphology and uniformity of the products. Here, we report a vapor-liquid-solid (VLS) growth process where non-volatile NaMoO is used to act as a liquid precursor for the growth of uniform ultrathin MoC nanosheets on AlO(0001). The morphology of the nanosheets can be controlled by tuning the precursor concentration, annealing time and growth temperature. The roles of Na and the liquid-solid interface in consolidating Mo atoms and promoting the epitaxial growth of MoC nanosheets are demonstrated. Furthermore, we show that the liquid-solid interface can cause the crystalline phase transition of MoC nanosheets through verification experiments.