Al 2 O 3 -SiO 2 glasses doped with Sm 3+ ions were irradiated with an 800 nm wavelength femtosecond laser pulse and the formation of Sm 2+ ions was investigated. The Sm 3+ ions were reduced to Sm 2+ within a few minutes of laser irradiation. Electron spin resonance spectra indicated that the hole was trapped in non-bridging oxygen bound to Al 3+ , while the electron was captured in the Sm 3+ , leading to the Sm 2+ formation. The thermal stability of the photoinduced Sm 2+ ions was also investigated by fluorescence spectroscopy. The Sm 2+ ions were converted to Sm 3+ ions by heating the glasses in air at 300-400 • C.

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In this study, we proposed germanium (Ge) metal-interlayer-semiconductor-metal (MISM) photodiodes (PD), with an anode of a metal-interlayer-semiconductor (MIS) contact and a cathode of a metal-semiconductor (MS) contact, to efficiently suppress the dark current of Ge PD. We selected titanium dioxide (TiO₂) as an interlayer material for the MIS contact, due to its large valence band offset and negative conduction band offset to Ge. We significantly suppress the dark current of Ge PD by introducing the MISM structure with a TiO₂ interlayer, as this enhances the hole Schottky barrier height, and thus acts as a large barrier for holes. In addition, it collects photo-generated carriers without degradation, due to its negative conduction band offset to Ge. This reduces the dark current of Ge MISM PDs by ×8000 for 7-nm-thick TiO₂ interlayer, while its photo current is still comparable to that of Ge metal-semiconductor-metal (MSM) PDs. Furthermore, the proposed Ge PD shows ×6,600 improvement of the normalized photo-to-dark-current ratio (NPDR) at a wavelength of 1.55 μm. The proposed Ge MISM PD shows considerable promise for low power and high sensitivity Ge-based optoelectronic applications.

1,2-Phenylene-bridged dicobalt diporphyrin 1 catalyzes efficiently the four-electron reduction of dioxygen to water in acidic solution. The catalytic activity of the diporphyrin is strongly affected by the substituents on the phenyl rings attached to the porphyrin macrocycles.

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