Influence of Gadolinium-doping on the microstructures and phase transition characteristics of VO2 thin films

Abstract Rare earth (RE)-doping is an effective approach for modulating the microstructures and properties of oxide semiconductors. We investigate the influence of Gadolinium-doping on the microstructures and semiconductor-to-metal transition (SMT) characteristics of VO 2 thin films prepared by a reactively co-sputtering process. The chemical state of Gd, microstructures, surface morphologies, and electrical properties of Gd-doped VO 2 thin films were analyzed by means of X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and four-point probe measurement, respectively. Gd-doping obviously reduces the grain size, and even induces amorphization in VO 2 thin films for a relatively high doping level. The SMT temperature of Gd-doped VO 2 thin films decreases with increasing the doping level (x, the concentration ratio of Gd to (V + Gd)). Furthermore, the SMT feature disappears as x increases up to 0.041. The resistivity of the Gd-doped VO 2 thin film (x = 0.041) is lower than undoped VO 2 thin films by nearly three orders. This can be attributed to weakened dimerization of V atoms and induced Gd 4f state above the lower d || V band due to Gd-doping.