Growth and electrical properties of vanadium dioxide single crystals containing selected impurity ions

Abstract

A series of vanadium dioxide single crystals containing small concentrations of different impurity ions were grown by a thermal decomposition technique. The impurity ions were chosen to have different electronic structure from the V 4+ ion they replace. It was expected that these ions would produce a systematic change in the semiconductor-metallic transition exhibited by the VO 2 phase. Contrary to expectations, no correlation with the electronic configuration of the substitutent ions could be recognized. However, this study leads to three qualitative conclusions relating the effect of impurities to the transition in conductivity: (1) The transition temperature is unaffected by the conductivity, i.e. carrier concentration, of the crystal. (2) Significant changes in the transition temperature are produced only by high doping levels—on the order of 1 mol %. (3) The direction of the change in transition temperature can be correlated with the relative size of the impurity ion compared to that of the V 4+ ion.