DIRECT-CURRENT MAGNETRON-SPUTTERED IN2O3 FILMS AS TUNNEL BARRIERS

Insulating films of In2O3 were prepared by sputtering indium in the pr esence of pure oxygen using dc magnetron sputtering. Transmission elec tron microscopic investigations showed the films to be single phase an d polycrystalline. Analysis of the optical transmittance data showed t he films to have an optical band gap of 3.71 +/- 0.01 eV. Tunnel junct ions were made with high T(c) superconductors Bi2Sr2Ca1Cu2Oy and NdBa2 Cu3O7-delta using indium oxide as the barrier layer and Pb0.5In0.5 as the counter electrode. The conductance spectra displayed prominent str uctures attributable to energy gap. The reduced gap parameters for Bi2 Sr2Ca1Cu2Oy and NdBa2Cu3O7-delta were found to be 4.0 +/- 0.5 and 5.2 +/- 0.6, respectively.