Preparation of MoO2 sub-micro scale sheets and their optical properties

MoO2 sub-micro sheets have been synthesized in a large scale on silicon substrate with MoO3 and C powders as raw materials using a novel chemical vapour deposition method. The lengths and widths of MoO2 sheets are in the range of several to dozens micrometers, and the thickness of MoO2 sub-micro sheets is ∼200 nm. Transmission electron microscopy and high-resolution electron microscopy show that the MoO2 sheets are of single crystal with a monoclinic structure. The sheets exhibit fluorescent emissions at 304.4, 343.5 and 350.6 nm when the 220 nm light excitation is applied at room temperature, and the emissions result from some defects and the electron transition between valence band and conduction band. UV–vis spectrum shows the MoO2 sub-micro sheets have absorption peaks between 200and 300 nm and the emissions should be attributed to the defect states of MoO2. Furthermore, the band-gap is estimated to be approximately 4.22 eV. The growth mechanism of the two-dimensional MoO2 sub-micro scale sheets is also discussed.

► A novel method to synthesize MoO2 sub-micro sheets is proposed.
► Detailed morphology, structure and chemical composition analysis of the sheets are presented.
► Optical properties and growth mechanism are discussed.