Adjustment of thermal hysteresis in epitaxial VO₂ films by doping metal ions

Abstract

Thermal hysteresises of electrical resistance, accompanying with a structural phase transition, in epitaxial VO₂ films have been successfully reduced to 1°C or less by doping Ti or Nb ions. We considered that owing to the metal-ion-substitutive structural defects induced by doping metal ions into VO₂ films, the structural phase transition easily occurred without superheating or supercooling. In Nb-doped VO₂ films, the hysteresis disappeared at a lower doping level than Ti-doped VO₂ films. The maximum values of the temperature coefficient of the resistance of V_0.91Ti_0.09O₂ and V_0.982Nb_0.018O₂ films, which exhibited non-hysteretic MI transitions, were −24.8%/°C at 46°C and −21.6%/°C at 19°C, respectively.