The synchronous generation of the surface streamer discharges from two electrodes in air is investigated in terms of wavelength and intensity of the discharge light as a trigger for the synchronization of the surface streamers. It is found that the light emitted from the first streamer causes the photoelectron emission and the photoionization in the vicinity of the opposing electrode, triggering synchronous discharge of the second streamer. The wavelength of the light contributing to this phenomenon is shorter than 250 nm, with a remarkable rise in synchronization probability from 164 nm to 115 nm. This is considered to be due to the existence of the photoabsorption windows for oxygen in this vacuum ultraviolet region. These results suggest that the photon energy required to supply initial electrons sufficient to trigger the surface streamers on an acrylic resin insulator is at least 5 eV and more enhancement is found at 8 and 10 eV in this study.

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The (111)-oriented chemical-vapor-deposited diamond homoepitaxial layers with low defect density exhibited well-resolved free-exciton transitions in cathodoluminescence at 13 K and a sharp peak at 1332 cm À1 (linewidth: 1.9 cm À1 ) in Raman scattering. Furthermore, using these (111) layers, we fabricated metal-semiconductor field-effect transistors (FETs). FETs with an 11-mm-long gate exhibited a maximum drain current of 24 mA/mm and maximum transconductance of 14 mS/mm. These values are of the same order as those for the (001) orientation.

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