Characteristics of Tc and ρ(T) of polycrystalline (In2O3)-(ZnO) films with low carrier density

For the polycrystalline (In2O3)-(ZnO) prepared by annealing in air, we investigated the relation among superconductivity, rho(T) characteristics and preparation conditions. To clarify the distribution of elements, we studied the microstructure by scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS). It was found that 1) The films annealed at restricted regions of annealing temperature T-a and time t(a) show the superconductivity. Transition temperature T-c and carrier density n are T-c<3.3K and n approximate to 10(25)/m(3)similar to 10(26)/m(3), respectively. 2) The data on EELS spectra mapping of indium plasmon indicate that droplets of the pure indium phase distribute discretely on grain boundaries and near the interface between the film and the glass substrate. 3) Although data in the T-c -T-a relation are scattered, the T-c shows relatively good correlation with n, taking a convex form.