Crystalline quality and optical properties of gallium oxide films grown on SiO2substrates by RF magnetron sputtering were studied. After the post annealing, it could be confirmed growth of gallium oxide (Ga2O3) film changed in a β ‐Ga2O3 film. Estimated optical energy gap of as‐grown and post annealed films are the same from 4.85 to 4.90 eV. The energy gap for as‐deposited film corresponds to band gap of β ‐Ga2O3.It has a property of β ‐Ga2O3 nevertheless the as‐deposited Ga2O3 films. The integrated absorption coefficient under the energy gap decreases with increasing thickness of Ga2O3 film. These results indicate that crystalline quality of β ‐Ga2O3 film is improved by increment the film thickness. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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We have investigated the photoluminescence (PL) properties of a CuBr microcavity at 10 K, including the temporal profiles, from the viewpoint of cavity-polariton condensation. The excitation energy density dependence of the PL intensity (band width) of the lower polariton branch at an in-plane wave vector of k// = 0 exhibits a threshold-like increase (decrease). A large blueshift in the PL energy of ∼10 meV caused by the cavity-polariton renormalization is correlated with the excitation energy density dependence of the PL intensity. The estimated density of photogenerated electron-hole pairs at the threshold is two orders lower than the Mott transition density. These results consistently demonstrate the occurrence of cavity-polariton condensation. In addition, we found that the PL rise and decay times are shortened dramatically by the cavity-polariton condensation, which reflects the bosonic final state stimulation in the relaxation process and the intrinsic cavity-polariton lifetime in the decay process.

Phenylxanthyl, phenylthioxanthyl, phenylselenoxanthyl, 9-phenylfluorenyl, dioxadehydrocoranthryl, and their derivatives were studied by the electron spin resonance (ESR) technique, and the odd-electron distribution in the radicals was examined. From the results, the angle between the plane of the phenyl group and the plane of the rest of the molecule was estimated at about 63°. Since these radicals are in equilibria with their dimers, heat of reaction in the system was also determined on two of them. Some discussion of the correlation between the heat of reaction and the molecular shape was undertaken.