Temperature dependent conduction and UV induced metal-to-insulator transition in ZnO nanowires

Thin ZnO nanowires with diameters of less than 50nm are configured as field effect transistors and studied for their transport mechanisms at different temperatures under UV illumination and gate modulation. The conductivity exhibits two regimes: at T>50K, thermally activated transport dominates with activation energy around 30–60meV attributed to the shallow donor states and at T<50K, three dimensional variable range hopping reveals in the conduction. In addition, UV irradiation leads to a metal-to-insulator transition at ∼210K. Furthermore, electrostatic gating results in a band bending giving rise to a change in the activation energy.