Switchable reflectivity on silicon from a composite VO2-SiO2 protecting layer

Surfaces whose reflectivity can be thermally controlled were formed on single crystals of silicon by using ion beams to create a nanocomposite layer consisting of VO2 precipitates embedded in a thin-film matrix of amorphous SiO2. The surface nanocomposite layer was produced by first thermally oxidizing a Si crystal to produce an overlying SiO2 film with a desired thickness. Stoichiometric coimplantation of vanadium and oxygen ions and subsequent thermal processing were then employed to form embedded VO2 nanoparticles in the SiO2 film. The reflectivity of the vanadium dioxide particles undergoes large changes at the VO2 semiconductor-to-metal phase transition, thereby providing the mechanism for thermally controlling the reflectivity of the VO2/SiO2/Si layer and, effectively, the Si crystal surface. The VO2/SiO2 nanocomposite layer was applied in a device configuration in which heating via current through the Si substrate is used to control the surface reflectivity. (C) 2004 American Institute of Physics.