We have experimentally demonstrated thermal rectification as bulk effect. According to a theoretical design of a thermal rectifier, we have prepared an oxide thermal rectifier made of two cobalt oxides with different thermal conductivities, and have made an experimental system to detect the thermal rectification. The rectifying coefficient of the device is found to be 1.43, which is in good agreement with the numerical calculation.Comment: 4 pages, 4 figures, Appl. Phys. Lett. (in press

The correlation between atomic structure and the electrical properties of thermally grown SiO2/4H-SiC(0001) interfaces was investigated by synchrotron x-ray photoelectron spectroscopy together with electrical measurements of SiC-MOS capacitors. We found that the oxide interface was dominated by Si-O bonds and that there existed no distinct C-rich layer beneath the SiC substrate despite literature. In contrast, intermediate oxide states in Si core-level spectra attributable to atomic scale roughness and imperfection just at the oxide interface increased as thermal oxidation progressed. Electrical characterization of corresponding SiC-MOS capacitors also indicated an accumulation of both negative fixed charges and interface defects, which correlates well with the structural change in the oxide interface and provides insight into the electrical degradation of thermally grown SiC-MOS devices.

The oxidation of Cu{100} with a hyperthermal O2 molecular beam (HOMB) was investigated using x-ray photoemission spectroscopy in conjunction with a synchrotron light source. The efficiency of oxidation with HOMB is higher than that with ambient thermal O2. Further oxidation under oxygen coverage (Θ)⩾0.5 ML occurs rather inefficiently even for the 2.3-eV-HOMB irradiation. We found that such slow oxidation of Cu corresponding to the initial stage of the Cu2O formation can be interpreted in terms of a collision-induced-absorption mechanism. The kinetics of the dissociative adsorption under Θ⩽0.5 ML is well described using the first-order kinetics in a simple Langmuir-type adsorption model.

Using real-time O 1s X-ray photoelectron spectroscopy together with Si 2p X-ray photoelectron spectroscopy, the oxygen bonding configurations of oxides shortly after exposing the Si(111)-7×7 surface to O2 at 300 K are revealed. It is found that the ins structure firstly forms where one oxygen atom sits in the backbond of the silicon adatom. It is confirmed that the chemisorbed molecular oxygen, the so-called paul oxygen, is the adsorbate on top of the ins structure. It is also clarified that the ad–ins structure and the ins–tri structure, where ad means an oxygen atom adsorbed onto top of the silicon adatom and tri means the interstitial oxygen atom, appear after a short time. The results implying the presence of mobile O2 on the surface were obtained.

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