Size-Dependent Insulator-to-Metal and Metal-to-Insulator Phase Transitions in VO_2 Microrods Grown on a Silicon Substrate

摘要

Light scattering from VO_2 microrods (MRs) synthesized on a silicon substrateis studied as a function of temperature and wavelength through the insulatorto-metal (IMT) and the metal-to-insulator (MIT) transitions. Light scatteringexhibits substantial and reproducible changes. By focusing the light onindividual MRs, it is shown that for small-sized MRs (<1 × 10 μm), the IMTand MIT are very sharp with transition temperatures varying within 31–64 °C(IMT) and within 58–76 °C (MIT). In contrast, for large-sized MRs(≈4 × 40 μm), only the IMT at 68 C is sharp, whereas MIT is stretched with aprominent low-temperature shoulder at 35–50 °C. The observed phenomenaare assumed to be connected with the external substrate-induced mechanicalstress emerging during the phase transition. A simple model is developed toexplain both the temperature-stretched MIT and the low-temperatureshoulder.