Electrical conductivity of the semiconducting phase in vanadium dioxide single crystals

The electrical conductivity of the semiconducting phase of vanadium dioxide single crystals is studied over a wide range of temperatures. It is shown that the electrical conductivity varies with temperature as log sigma similar to T in the range 340-170 K and as log sigma similar to 1/T at temperatures below 120 K. The experimental results are described in the framework of the model in which the temperature dependence of the hopping conductivity of L, small-radius polarons is determined by the dependence of the resonance integral on the amplitude of thermal lattice vibrations.