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A nanoelectromechanical device incorporating the nanocrystalline silicon ͑nc-Si͒ dots is proposed for use as a high-speed and nonvolatile memory. The nc-Si dots are embedded as charge storage in a mechanically bistable floating gate. Position of the floating gate can therefore be switched between two stable states by applying gate bias. Superior on-off characteristics are demonstrated by using an equivalent circuit model which takes account of the variable capacitance due to the mechanical displacement of the floating gate. Mechanical property analysis conducted by using the finite element method shows that introduction of nc-Si dot array into the movable floating gate results in reduction of switching power. High switching frequency over 1 GHz is achieved by decreasing the length of the floating gate to the submicron regime. We also report on experimental observation of the mechanical bistability of the SiO 2 beam fabricated by using the conventional silicon etching processes.

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Amorphous SixC1−x : H alloys are prepared by simultaneous rf reactive sputtering of silicon and graphite in a H2-Ar gas mixture. Silicon, carbon, and hydrogen contents are measured for the entire range of x by electron spectroscopy for chemical analysis (ESCA), Rutherford-backscattering method, and thermal evolution of hydrogen. Evolution temperature dependence of the number of evolved hydrogen atoms is measured. The hydrogen-evolution behavior and the optical gap are x dependent. These phenomena are discussed in the light of chemical-bonding states.

Red luminescence in CdS has been studied in as-grown and ion-implanted crystals. An IR band consisting of two emission bands, IR1 and IR2, is produced by ion implantation. The higher-energy band, IR1, has the same origin as the R band observed in some as-grown crystals. A comparison of the R and IR1 bands in CdS with self-activated (SA) luminescence in ZnS and GaAs shows that they are SA luminescence at 1.7 eV at low temperatures in CdS. The temperature variations in peak energy, half-width, and intensity of luminescence are discussed, and the behavior is explained in terms of a configurational coordinate model. A vibrational energy of 0.025 eV, which is about 70% of the LO phonon energy in CdS, is calculated for the excited state of the center. The study of the excitation dependence of the center shows that the luminescence is due to an electronic transition within a localized center and not due to a donor-acceptor pair recombination. The center has an excitation band about 0.22 eV below the band gap. The annealing behaviors of the IR1 and IR2 centers are similar to each other, the bands abruptly disappear over 400°C. There are competitive phenomena between the IR1 and IR2 centers as to temperature and excitation-intensity dependences. We tentatively attribute the IR2 band to an aggregation defect center.