Shape-controlled synthesis and influence of W doping and oxygen nonstoichiometry on the phase transition of VO₂

Monoclinic VO₂ (M) in nanostructure is a prototype material for interpreting correlation effects in solids with fully reversible phase transition and for the advanced applications to smart devices. Here, we report a facile one-step hydrothermal method for the controlled growth of single crystalline VO₂ (M/R) nanorods. Through tuning the hydrothermal temperature, duration of the hydrothermal time and W-doped level, single crystalline VO₂ (M/R) nanorods with controlled aspect ratio can be synthesized in large quantities, and the crucial parameter for the shape-controlled synthesis is the W-doped content. The dopant greatly promotes the preferential growth of (110) to form pure phase VO₂ (R) nanorods with high aspect ratio for the W-doped level=2.0 at% sample. The shape-controlled process of VO₂ (M/R) nanorods upon W-doping are systematically studied. Moreover, the phase transition temperature (T_c) of VO₂ depending on oxygen nonstoichiometry is investigated in detail.