Direct growth of 2D MoO2 single crystal on SiO2/Si substrate by atmospheric pressure chemical vapor deposition

Due to its distinct properties, two-dimensional (2D) materials had attracted much attention and plenty of 2D materials had been synthesized and studied. Metal oxides have been widely used in lithium-ion battery, supercapacitor, catalyst, etc, but the corresponding 2D material of metal oxides has not been sufficiently researched. Here, micrometer-scale 2D Molybdenum dioxide (MoO2) single crystals have been successfully synthesized directly on silicon dioxide/silicon (SiO2/Si) substrate by atmospheric pressure chemical vapor deposition, through the reduction by hydrogen. The growth temperature is 690 degrees C, and the reduction reaction lasted with 90 minutes. Raman spectra and x-ray photoelectronic spectroscopy are used to confirm the chemical component of MoO2. The shape of two-dimensional MoO2 single crystals has three types, including standard parallelogram, parallelogram with two angles misses and hexagonal. The growth model of three shape types is discussed, and the difference in growth velocity between two growth directions is the key factor of the final shape. The theoretical calculation confirmed the metallic property of as-synthesized 2D MoO2 and its resistivity is 2 x 10(-4) Omega*cm, indicating it has excellent conductivity and may have potential application for conducting films.