A highly-efficient approach for reducing phase transition temperature of VO2 polycrystalline thin films through Ru4+-doping

摘要

A low semiconductor-metal transition (SMT) temperature (T-SMT) is highly desirable for advancing practical applications of VO2. The doping with tetravalent metal elements attracts little attention as an effective approach for reducing the T-SMT of VO2. Here we investigate the effect of Ru-doping on the microstructure and SMT characteristics of VO2 polycrystalline thin films. X-ray photoelectron spectroscopy reveals that Ru ions exist in the tetravalent oxidation state in Ru-doped VO2 thin films. X-ray diffraction patterns and Raman spectra indicate that substitutional Ru4+ ions decrease the crystallite size of films and induce the local tetragonal symmetry in the framework of monoclinic VO2 lattice. As a result, Ru4+-doping reduces the T-SMT of VO2 polycrystalline thin films at the rate of 10.5 degrees C/at%. Moreover, the room temperature resistivity of thin films decreases from 9.98 Omega.cm for undoped VO2 to 0.63 Omega.cm for Ru-doped one with Ru atomic concentration of 2.32 at%, which is ascribed to the narrowed band gap and enhanced density of states of the V 3d band.

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