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The superconducting electronic states of Nd 1.85 Ce 0.15 CuO 4Ϫ␦ ͑NCCO͒ are studied by applying the phasesensitive capability of tunneling spectroscopy. Unlike the YBa 2 Cu 3 O 7Ϫ␦ cases, the conductance spectra measured on ͑100͒-, ͑110͒and ͑001͒-oriented surfaces showed V-shaped gap structures, and no zero-bias conductance peaks were observed even around steps on the surfaces. The present results reject the possibility of d x 2 Ϫy 2-wave and d xy -wave symmetries for the pair potential in NCCO. The experimental spectra are well fitted to theoretical curves of anisotropic s-wave symmetry with a large smearing factor.

Perovskite thin‐film electroluminescence devices are prepared, opening up a new optical application of perovskite materials. With increasing driving voltage, the intensity of electroluminescence increases dramatically. High‐quality red color is produced and the working voltage for whole‐surface electroluminescence is as low as 10 V.

Oxide phosphors are attractive materials for various applications in optoelectronic devices due to their high chemical stability and efficient luminescent characteristics. As yet, however, the fabrication of high-quality luminescent thin films on a glass substrate remains challenging for practical implementation. Here, we report the efficient fabrication of highly oriented luminescent perovskite oxide films on a glass substrate using a monolayer film of oxide nanosheets as the seed layer. A densely packed monolayer film of Ca2Nb3O10 nanosheets was prepared by the Langmuir−Blodgett (LB) method, where hybridization of the cationic molecules and the Ca2Nb3O10 nanosheets produced stable LB films with large-area processability. Oriented thin films with a sharp and intense emission of Pr0.002(Ca0.6Sr0.4)0.997TiO3 were successfully obtained on a glass substrate modified with a seed layer. Highly luminescent transparent films are producible on inexpensive noncrystalline substrates; this approach also enables large-area processing of high-quality thin-film phosphors.

Intense red photoluminescence ͑PL͒ under ultraviolet ͑UV͒ excitation was observed in epitaxially grown Pr-doped Ca 0.6 Sr 0.4 TiO 3 perovskite films. The films were grown on SrTiO 3 ͑100͒ substrates by pulsed laser deposition, and their epitaxial growth was confirmed by x-ray diffraction and reflected high-energy electron diffraction. The observed sharp PL peak centered at 610 nm was assigned to the transition of Pr 3+ ions from the 1 D 2 state to the 3 H 4 state. The PL intensity was markedly enhanced by postannealing treatments at 1000°C, above the film-growth temperature of 600 or 800°C. Because the excitation and absorption spectra are similar to each other, it was suggested that the UV energy absorbed by the host lattice was transferred to the Pr ions, resulting in the red luminescence.

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