Photoinduced heterostructure in a vanadium dioxide film

A photoinduced semiconductor–metal phase transition that occurs in a surface layer of vanadium dioxide film on an aluminum substrate within the time $\Delta t<$ 1 ps has been studied theoretically. A nonthermal mechanism of the development of instability has been considered. It has been shown that a heterophase structure containing metallic and semiconductor layers is formed in the VO$_2$ film. The phase transition time $\tau$ has been calculated as a function of the distance $z$ from the film surface. Comparison with the experiment has been carried out.