Two-dimensional MoO3 via a top-down chemical thinning route

Two-dimensional MoO3 is a versatile planar material, whose properties can be readily tuned, rendering it anywhere from a wide bandgap semiconductor to semi-metallic. This makes it a desirable candidate for a wide range of applications. However, to utilise its full potential, a repeatable process to produce high-quality two-dimensional (2D) crystals is yet to be reported. Here, we report a wet chemical etching process to controllably thin down bulk crystals of MoO3. This process does not result in any structural or compositional changes, while retaining the desirable intrinsic electronic properties of the material. Field effect transistors based on post-etched crystals exhibit switching ratios of over three orders of magnitude. As such, the proposed thinning process opens pathways to exploit the exotic properties of planar MoO3 to create versatile 2D systems.