Superconductivity in transparent zinc-doped InO films having low carrier density.

Thin polycrystalline zinc-doped indium oxide (InO-ZnO) films were prepared by post-annealing amorphous films with various weight concentrations of ZnO in the range 0⩽ ⩽0.06. We have studied the dependences of the resistivity ρ and Hall coefficient on temperature and magnetic field in the range 0.5⩽ ⩽300 K, ⩽6 Tfor 350 nm films annealed in air. Films with 0⩽x⩽0.03 show the superconducting resistive transition. The transition temperature is below 3.3 K and the carrier density is about 10-10 m. The annealed InO-ZnO films were examined by transmission electron microscopy and x-ray diffraction analysis revealing that the crystallinity of the films depends on the annealing time. We studied the upper critical magnetic field () for the film with = 0.01. From the slope of d /d, we obtain the coherence length ξ (0) ≈ 10 nm at = 0 K and a coefficient of electronic heat capacity that is small compared with those of other oxide materials.