Synthesis and characterization of size-controlled vanadium dioxide nanocrystals in a fused silica matrix

Vanadium dioxide single-crystal precipitates with controlled particle sizes were produced in an amorphous, fused ${\mathrm{SiO}}_2$ host by the stoichiometric coimplantation of vanadium and oxygen ions and subsequent thermal processing. The effects of the vanadium dioxide nanocrystal size, nanocrystal morphology, and particle/host interactions on the ${\mathrm{VO}}_2$ semiconductor-to-metal phase transition were characterized. ${\mathrm{VO}}_2$ nanoparticles embedded in amorphous ${\mathrm{SiO}}_2$ exhibit a sharp phase transition with a hysteresis that is up to 50 °C in width—one of the largest values ever reported for this transition. The relative decrease in the optical transmission in the near-infrared region in going from the semiconducting to the metallic phase of ${\mathrm{VO}}_2$ ranges from 20% to 35%. Both the hysteresis width and the transition temperature are correlated with the size of the precipitates. Doping the embedded ${\mathrm{VO}}_2$ particles with ions such as titanium alters the characteristics of the phase transition, pointing the way to control the hysteresis behavior over a wide range of values and providing insight into the operative physical mechanisms.