Metal–insulator phase transition in iron-doped vanadium dioxide thin films

The electrical conductivity of polycrystalline V$_{(1-x)}$Fe$_{x}$O$_{2}$ films has been investigated in a wide temperature range, which covers both the metal and insulator phase regions. It is shown that with an increase in the iron concentration the metal–insulator phase transition shifts toward lower temperatures, while the temperature range of the transition in doped samples additionally broadens as compared with pure VO$_2$. To explain the temperature dependence of the electrical conductivity of the V$_{(1-x)}$Fe$_{x}$O$_{2}$ insulator phase, a hopping conductivity model has been used, which takes into account the effect of thermal vibrations of atoms on the resonance integral. The values of parameter $\varepsilon$ have been calculated as a function of the degree of VO$_2$ doping.