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Hydrogen incorporation into nitrogen vacancies in silicon nitride and its effects on electron trap level are analyzed using simulation based on density functional theory with temperature- and pressure-dependent hydrogen chemical potential. If the silicon dangling bonds around a nitrogen vacancy are well separated each other, hydrogen incorporation is energetically stable up to 900 °C, which is in agreement with the experimentally observed desorption temperature. On the other hand, if the dangling bonds strongly interact, the incorporation is energetically unfavorable even at room temperature because of steric hindrance. An electron trap level caused by a nitrogen vacancy becomes shallow by the hydrogen incorporation. An electron is trapped in a deep level created by a silicon dangling bond before hydrogen incorporation, whereas it is trapped in a shallow level created by an anti-bonding state of a silicon-silicon bond after hydrogen incorporation. The simulation results qualitatively explain the experiment, in which reduced hydrogen content in silicon nitride shows superior charge retention characteristics.

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The Ar+ laser-enhanced chemical etching of a modified PbTiO3 ceramics is studied. It is shown that 10 mol/lKOH water solution is the best etchant for the ceramics, giving excellent appearances and edge definitions for hole and slot machining. The depth etch rate is as high as 150 µm/s for the hole machining in the first one second irradiation at 1 W output at 514.5 nm wavelength. It is postulated the main etching mechanism is not direct melting, dissolving or vaporizing of the ceramics but removing of the ceramic grains one after another.