Hideyuki Noshiro

RuO2 Thin Films as Bottom Electrodes for High Dielectric Constant Materials

Ruthenium dioxide ( RuO2) thin films are evaluated as a bottom electrode for SrTiO3. It was found that a thin RuO2(50 nm)/Ru(20 nm) layer on Si is quite effective as a barrier layer for both orygen atoms and metals when depositing SrTiO3 at a relatively low temperature of 450° C. To test its suitability for high-temperature processes such as CVD of SrTiO3, the RuO2/Ru electrode on Si was annealed in air at 600° C for 1 hour. Even under this severe condition, the electrode using 100-nm-thick RuO2 was sufficient for preventing oxygen diffusion into Si.

Josephson Junctions Using Polyimide Langmuir-Blodgett Films with a Nb/Au/PI/(Pb-Bi) Structure

We fabricated Josephson junctions with the structure of Nb/Au/PI/(Pb-Bi) using an ultrathin polyimide (PI) Langmuir- Blodgett film as an electrically insulating layer with neither the presence of native oxide layers formed on the base Nb layer nor the dissolution of the base-Nb/Au electrode during the imidization of PAA (Polyamic acid long alkylamine salts) films to produce PI LB films. A typical I-V characteristic of weakly-coupled Josephson junctions was found to be obtained.

Influence of Electrode Contacts on Leakage Current of SrTiO3 Capacitors

The current-voltage (I-V) characteristics of capacitors using SrTiO3 film were investigated. Rectification characteristics were observed, either when oxygen gas was introduced during sputter deposition of top electrodes, or when the SrTiO3 film was annealed in oxygen. These I-V characteristics are attributed to blocking contacts between SrTiO3 and the electrodes. It is considered that such contacts are formed because of the reduction of the crystal defects in SrTiO3 films, and they have decisive influence on the leakage current of the capacitor.

Electrical transport properties of Josephson junctions with a Nb/Au/PI(PbBi) structure

Abstract We fabricated tunnel junctions with structures of Au/PI/Pb and of Nb/Au/PI/(PbBi) incorporating high-quality and ultrathin polyimide (PI) Langmuir-Blodgett (LB) films and then examined the electrical transport properties of the junctions. The inelastic electron tunneling spectroscopy (IETS) spectra of the Au/PI/Pb junctions reveals that the inelastic electron tunneling process accompanied by the energy loss due to the coupling of tunneling electrons with the vibrational modes of polyimide does not make a significant contribution. For Nb/Au/PI/(PbBi) Josephson junctions, we obtained typical I–V characteristics of a weakly coupled superconductor.