Annealing effect on the superconductivity of In2O3-ZnO thin films

We have investigated the relation among ρ-T characteristics, superconductivity, annealing conditions and the crystallinity of polycrystalline (In2O3)1−x-(ZnO)x films. We annealed as-grown amorphous films in air by changing annealing temperature and time. It is found that the films annealed at 200 °C or 300 °C for a time over 0.5 h shows the superconductivity. Transition temperature Tc and the carrier density n are Tc < 3.3 K and n ≈ 1025-1026 m−3, respectively. Investigations for films with x = 0.01 annealed at 200 °C have revealed that the Tc, n and crystallinity depend systematically on annealing time. Further, we consider that there is a suitable annealing time for sharp resistive transition because the transition width becomes wider with longer annealing times. We studied the upper critical magnetic field Hc2(T) for the film with different annealing time. From the slope of dHc2/dT for all films, we have obtained the resistivity ρ dependence of the coherence length ξ(0) at T = 0 K.