Can fluorophlogopite mica be used as an alkali metal ion source to boost the growth of two-dimensional molybdenum dioxide?

Everyone familiar with two-dimensional (2D) materials is aware of fluorophlogopite mica (FM), which has an atomic-level flat surface that provides an ideal platform for the growth of 2D materials. Since it has been demonstrated that the alkali metal ions (AMI) can aid in the growth of large-sized 2D materials by chemical vapor deposition (CVD) in recent years, it became a major mystery whether FM which contains AMI benefits from them in the preparation of 2D materials by CVD, too. In this article, we dispelled this ambiguity and discovered that temperature is the key for FM as an AMI source to boost the growth of large-sized 2D materials. We carried out variable temperature experiments and found that FM can indeed be incorporated into the growth of large-sized 2D materials as an AMI source at high temperatures and successfully obtained the highly crystalline MoO2 with a larger size compared to those without FM. This finding is of great importance to the understanding of the growth mechanism of FM for 2D materials by CVD and to better exploit its role in the growth of 2D materials.