Two-dimensional current percolation in nanocrystalline vanadium dioxide films

Simultaneous measurements of the transmittance and the resistance were carried out on 20-nm-thick VO2 wires during the semiconductor-to-metal transition (SMT). They reveal an offset between the effective electrical and optical switching temperatures. This shift is due to current percolation through a network of nanometer-scale grains of different sizes undergoing a SMT at distinct temperatures. An effective-medium approximation can model this behavior and proves to be an indirect method to calculate the surface coverage of the films. (c) 2006 American Institute of Physics.