Epitaxial growth and transport properties of Nb-doped SrTiO3_{3} thin films

Nb-doped SrTiO$_{3}$ epitaxial thin films have been prepared on (001) SrTiO$_{3}$ substrates using pulsed laser deposition. A high substrate temperature ($>1000^{\circ}{C}$) was found to be necessary to achieve 2-dimensional growth. Atomic force microscopy reveals atomically flat surfaces with 3.9 \AA $$ steps. The films show a metallic behavior, residual resistivity ratios between 10 and 100, and low residual resistivity of the order of 10$^{-4}$$\Omega$cm. At 0.3 K, a sharp superconducting transition, reaching zero resistance, is observed.Comment: 4 pages, 4 figure

Detection Efficiency of Lorentz and Dispersion Types of Resonance

開始ページ、終了ページ: 冊子体のページ付

Enantioselective Synthesis of the 5–6–7 Carbocyclic Core of the Gagunin Diterpenoids

A catalytic enantioselective double allylic alkylation reaction has been employed in the synthesis of the core of the gagunin diterpenoids. Enantioenriched material was advanced in 11 steps to afford the core of the highly oxygenated target, which includes two all-carbon quaternary stereocenters

Research into the Retention Force of Electroformed Secondary Bar

INTRODUCTION: Electroformed metals are known to present good adaptability and biocompatibilities, but it is not yet known if the retention force of the electroformed secondary bar frame (ESBF) can endure long use. To clarify this point, the retention force between the primary cast bar and ESBF were measured. MATERIAL AND METHODS: An edentulous model was prepared and four implants (Frialit 2) were embedded. The fabrication of the primary bar was cast from pure titanium. We coated the completed titanium bar with silver lacquer and applied 0.3mm thick electrodeposite. The ESBF was attached to the cast titanium primary bar, cyclical tests performed for 15000 cycles and the retention force measured each time. The retention forces were measured in 37°C distilled water . RESULTS: The retention force value dropped as the number of reseating increased. It was 22N after 1000, 19N after 5000, 18N after 10000 and 16N after 15000 cycles. The hysteresis curve indicated that the resistance during cyclical testing was constant and stable up until the completion of 15000 cycles. CONCLUSION: The results confirmed that the retention force dropped gradually as the number of cycles increased, but that the stress imposed on the implants due to attaching and removal was low. This may be due to the excellent adaptation accuracy. In the case when repetition of attaching and removing for a long period is considerered, we need an attachment to enable the provision of a stable retention force Supported by Wieland Edelmetalle

Photoemission from buried interfaces in SrTiO3/LaTiO3 superlattices

We have measured photoemission spectra of SrTiO3/LaTiO3 superlattices with a topmost SrTiO3 layer of variable thickness. Finite coherent spectral weight with a clear Fermi cut-off was observed at chemically abrupt SrTiO3/LaTiO3 interfaces, indicating that an ``electronic reconstruction'' occurs at the interface between the Mott insulator LaTiO3 and the band insulator SrTiO3. For SrTiO3/LaTiO3 interfaces annealed at high temperatures (~ 1000 C), which leads to Sr/La atomic interdiffusion and hence to the formation of La1-xSrxTiO3-like material, the intensity of the incoherent part was found to be dramatically reduced whereas the coherent part with a sharp Fermi cut-off is enhanced due to the spread of charge. These important experimental features are well reproduced by layer dynamical-mean-field-theory calculation