Direct current magnetron sputtered In<inf>2</inf>O<inf>3</inf> films as tunnel barriers

Insulating films of In2O3 were prepared by sputtering indium in the presence of pure oxygen using dc magnetron sputtering. Transmission electron microscopic investigations showed the films to be single phase and polycrystalline. Analysis of the optical transmittance data showed the films to have an optical band gap of 3.71±0.01 eV. Tunnel junctions were made with high Tc superconductors Bi2Sr 2Ca1Cu2Oy and NdBa 2Cu3O7-δ using indium oxide as the barrier layer and Pb0.5In0.5 as the counter electrode. The conductance spectra displayed prominent structures attributable to energy gap. The reduced gap parameters for Bi2Sr2Ca1Cu 2Oy and NdBa2Cu3O 7-δ were found to be 4.0±0.5 and 5.2±0.6, respectively.