To obtain low-dislocation-density c-plane AlN on sapphire, we have studied the annealing of AlN films at 1650 °C. We prepared an AlN film with a thickness of 20 nm by radio-frequency (RF) sputtering, on which an AlN epilayer with a thickness of 280 nm was grown by metalorganic vapor phase epitaxy (MOVPE) at different growth temperatures. Finally, the AlN film on sapphire was annealed at 1650 °C. The full width at half maximum (FWHM) of the X-ray rocking curve (XRC) for AlN(0002) was approximately 50 arcsec for all samples, whereas that for AlN( 1012) significantly decreased from 6500 to 350 arcsec after thermal annealing. A surface morphology with atomic steps and a terrace structure was clearly observed after thermal annealing. From these results, we concluded that a high-quality AlN film can be obtained by annealing a stacking structure of MOVPE-grown AlN (buffer layer)/sputtered AlN (nucleation layer)/sapphire substrate.
A Cu 2 O thin film of cuprite crystal structure was fabricated via a decomposition reaction of water vapor generated by ultrasonic vibration. The thin film, which was grown on a soda-lime glass substrate at 530 • C, exhibited a prominent (111) preferred orientation with an optical bandgap of about 2.1 eV and resistivity of 2.81 × 10 4 Ω · cm. Generation of H 2 gas during the reaction process contributed to suppressing the growth of impurity tenorite phase. In a conventional process of thermal oxidation, the formation of the cuprite phase was always accompanied by that of the tenorite phase due to an excess oxygen exposure near the surface of the films.
Peroxy-trans-crotonic acid was prepared from dicrotonyl peroxide by alkaline cleavage and isolated for the first time in a crystalline state, mp 41–42°C. It was characterized by NMR and IR spectra, and its stability briefly tested. Reaction with dimethyl sulfide gave a quantitative yield of crotonic acid. Its pKa in water at 25°C was 8.2. Second order rate constants of reaction with crotonaldehyde in benzene (Table 4) were measured: Ea, 13.3 kcal/mol; log A(l/mol sec), 5.3; ΔS\eweq, −36 eu/mol. Detection of a possible intermediate, a peracid-aldehyde complex X, was attempted by means of NMR but evidence for it was not obtained.
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