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Magnesium oxide (MgO) films were prepared on a Si(001) substrate by the rf sputtering method at low ambient pressure using a metal target. The X-ray diffraction verified the epitaxial growth of MgO( 001) with a cubic-on-cubic arrangement despite the large lattice mismatch between MgO(100) and Si(100), and contractions of the unit cell along both the out-of-plane and in-plane directions. Epitaxial growth is described as a domain epitaxial relation with a domain mismatch consisting of (k × ) lattice units of the Si substrate and (m × n) ones of the MgO film. To visualize the domain mismatch with combinations of k, , m and n, coherent strains were depicted on polar coordinates. The domain mismatch was estimated as a small value, which was further decreased by the contraction of the unit cell in the epitaxial MgO film.

The thermal stability of (0001) sapphire was investigated at atmospheric pressure using the in situ gravimetric monitoring (GM) method. The weight change of a sapphire substrate was monitored at various hydrogen partial pressures in carrier gas (PH2) at temperatures over 1200 °C. Although the sapphire substrate was stable up to 1450 °C in an inert carrier gas (PH2 = 0.0 atm), sapphire decomposition started to occur at 1200 °C in H 2 carrier gas (PH2 = 1.0 atm). Moreover the activation energy and order of reaction for sapphire surface decomposition changed at approximately 1300 °C. These results indicate that the rate-limiting reaction for sapphire decomposition shifts near 1300 °C. 1 Introduction Group-III nitrides such as InN, GaN and AlN are very promising materials for potential use in optical devices and high-speed electronic devices. These materials and their alloys, such as InGaN and AlGaN, have a direct-transition band structure and cover the energy band gap range from 0.7 to 6.2 eV, which corresponds to the emission wavelength range from 200 nm (UV) to 1770 nm (IR). In particular, since AlN has the widest band gap energy (6.2 eV) and high thermal conductivity (3.3 W m

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SrRuO3 films were grown on (001)SrTiO3 single crystal substrates by rf magnetron sputtering under various total pressures, and their crystal structure, room temperature resistivity, and temperature dependency of resistivity were investigated. High-resolution X-ray diffraction (XRD) analysis revealed that the unit cell volume of these films decreased with increasing total pressure from 1.3 to 27 Pa and was almost constant above 27 Pa corresponding to that of bulk SrRuO3. SrRuO3 films deposited under a total pressure of 27 Pa showed the lowest room temperature resistivity, i.e., 250 µΩ·cm, almost the same as the reported one of the SrRuO3 single crystal. This film also showed a positive temperature dependency of resistivity with a temperature dependency change at about 150 K, which was also in good agreement with the reported one of the SrRuO3 single crystal.