Yoshinobu Ueba

Preparation of Alkaline-Metal-Doped C60 Superconducting Film and Its Stabilization in Air with Protective Coatings

Preparation conditions of C60 film were studied by varying substrates, substrate temperature and the rate of evaporation. Crystalline C60 thin films were prepared on GaAs(100) at the substrate temperature of 100° C in order to obtain superconductors by alkaline metal doping. The Rb/Cs-doped film showed a superconducting transition with T c( onset)=24±3 K and T c( zero)=8 K. The composition of the superconducting film was measured by micro-Auger electron spectroscopy. Air stability of Rb3C60 superconducting film with protective coatings applied was studied. A Si protective film maintained superconductivity for 220 min in air. In addition a Si/Al protective coatings maintained superconductivity for 8 h.

An organic electroluminescent device with a molecularly doped polymer hole transport layer

Electroluminescent(EL) devices have been fabricated using four different polymers with different glass transition temperatures (Tg) dispersed with N,N′-bis-(3-methylphenyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (TPD) as a hole transport layer and tris(8-hydroxyquinoline) aluminum (Alq3) as an emitting layer. It was found that the higher the Tg of the polymer, the longer the lifetime of the device. From observations of TPD-doped polymer films with optical microscope and atomic force microscope, dispersing TPD in the polymers was found to suppress the crystallization that causes the roughness of the film surface. It was also observed that the higher the Tg of the host polymers, the more difficult TPD crystallization was. The property of the EL device with polyethersulfone (PES) dispersed with TPD was also investigated. The lifetime of EL device with the TPD doped PES film was improved more than five times at a current density below 10 mA/cm2 compared with the device with a conventional TPD hole transport layer.

Stabilization of Rb 3 C 60 Superconducting Film in Air

The air stability of Rb3C60 superconducting film was studied with applying protective coatings. Rb3C60 superconducting thin film was prepared with vacuum deposition equipment using the conventional method. The protective film was deposited on the Rb3C60 film using the electron beam method. The sample with a Si protective film shows superconducting transition at TC(onset) =24K, TC (zero)=10K. Si protective film maintained superconductivity for 220 minutes in air. In addition Si/Al double protective coatings maintained superconductivity for 8 hours.

Chemistry en Route to Applications of Organic Superconductors

Sonochemically or thermally induced oxidation of bis(ethylendithiolo)tetrathiafulvalene (BEDT-TTF or ET) with Cu(SCN)2 yields superconducting, microcrystalline к-(ET)2Cu(NCS)2. IR- and ESR-spectra as well as X-ray diffractograms of so-obtained material are in accordance with those of authentic samples and prove the exclusive formation of the desired compound in both procedures. Susceptibility measurements gave superconducting transition temperatures Tc around 10 K and clear evidence of a Meissner effect, which suggests that superconductivity is a bulk-property of the powder samples.

Alkaline Metals Doping into C60 Thin Films

C60 thin films were prepared on GaAs(100) and quartz substrates by two different vapour deposition methods. Rb and Cs were found to be doped in crystalline C60 thin films by the resistance measurement during the course of the doping experiment. The Rb/Cs-doped film showed a superconducting transition at Tc(onset)=24±3 K and Tc(zero)=8 K. The composition of the superconducting film was investigated by µ-Auger Electron Spectroscopy (µ -AES). This is the first confirmation of superconductivity in a Cs/Rb-doped Cgo thin film.

Preparation of C60 Thin Films and Cs-Rb Doping

Abstract The effect of preparation conditions onto the crystallinity of C60 thin films were studied by using two different vapor deposition methods. Rb and Cs were found to be doped in C60 thin films by the resistance measurement during the course of the doping experiment. The Rb/Cs-doped film showed a superconducting transition at Tc(onset)=24±3K and Tc(zero)=8K.

Growth and Structure of (Tl,Bi,Pb)Sr2CaCu2OX Single Crystal

Crystal growth and structural analysis of (Tl,Bi,Pb)Sr2CaCu2Ox single crystals were performed. A single crystal with superconducting onset transition temperature of 85K was grown in a sealed gold tube by the slow-cooling method. The crystal structure was determined to be tetragonai(P4/mmm) with lattice constants of a=3.80A and c=12.09A. The refinement of the crystal structure was carried out based on the single-crystal X-ray diffraction data.