Van der Waals Epitaxy of Two-Dimensional $\alpha $-MoO$_{3}$ Nanosheets using Mica as Grown Templates

The orthorhombic Molybdenum trioxide, $\alpha $-MoO$_{3}$, is one kind of graphene-like layered materials. Since the great promise for future electronic and optoelectronic application, this molybdenum-based two-dimensional (2D) layer material has recently attracted much attention. In this work, we report a Van der Waals epitaxy of $\alpha $-MoO$_{3}$ nanosheets on mica substrate under ambient pressure. This simple physical vapor-phase deposition process is proposed to medicate through the weak Van der Waals interaction between layered $\alpha $-MoO$_{3}$ and mica substrate. As a result, the grown $\alpha $-MoO$_{3}$ nanosheets, whose lateral dimension is up to 0.1mm and thickness less than 2.8 nm (about bilayer MoO$_{3}$ octahedral structure), exhibit defined lattice orientation. From bulk to bilayer, Raman spectra of $\alpha $-MoO$_{3}$ nanosheets show independed with layered number, which unlike to MoS$_{2}$. The measurement of electric resistances at room temperature shows the conductance of original $\alpha $-MoO$_{3}$ nanosheets is already high, moreover, which can be greatly improved by hydrogen doping. Our works indicate that VDWE with mica templates is a simple and feasible strategy to grow high-quality ultrathin $\alpha $-MoO$_{3}$ nanosheets, which have superiorities for investigating its novel physical properties and potential application in future.