Optical switching of coherent VO2 precipitates formed in sapphire by ion implantation and annealing

Coherent precipitates of vanadium dioxide have been formed in the near-surface region of sapphire by the stoichiometric coimplantation of vanadium and oxygen combined with subsequent thermal processing at temperatures ranging from 700 to 1000 degrees C. The embedded VO2 precipitates, which are three-dimensionally oriented with respect to the Al2O3 host lattice, undergo a first-order monoclinic-to-tetragonal (and also semiconducting-to-metallic) phase transition at similar to 77 degrees C. This transformation is accompanied by a significant,variation in the optical transmission of the implanted region and results in the formation of an optically active, thermally ''switchable'' surface region on Al2O3. (C) 1996 American Institute of Physics.