Two sources of room temperature visible luminescence are identified from SiO 2 films containing ion beam synthesized Si nanocrystals. From a comparison of luminescence spectra and photoluminescence decay lifetime measurements between Xe ϩ -implanted SiO 2 films and SiO 2 films containing Si nanocrystals, a luminescence feature attributable to defects in the SiO 2 matrix is unambiguously identified. Hydrogen passivation of the films selectively quenches the matrix defect luminescence, after which luminescence attributable to Si nanocrystals is evident, with a lifetime on the order of milliseconds. The peak energy of the remaining luminescence attributable to Si nanocrystals ''redshifts'' as a function of different processing parameters that might lead to increased nanocrystal size and the intensity is directly correlated to the formation of Si nanocrystals. Upon further annealing hydrogen-passivated samples at low temperatures ͑Ͻ500°C͒, the intensity of nanocrystal luminescence increases by more than a factor of 10.

Synthesis of Ge nanocrystals in SiO 2 films is carried out by precipitation from a supersaturated solid solution of Ge in SiO 2 made by Ge ion implantation. The films exhibit strong room-temperature visible photoluminescence. The measured photoluminescence peak energy and lifetimes show poor correlations with nanocrystal size compared to calculations involving radiative recombination of quantum-confined excitons in Ge quantum dots. In addition, the photoluminescence spectra and lifetime measurements show only a weak temperature dependence. These observations strongly suggest that the observed visible luminescence in our samples is not due to the radiative recombination of quantum-confined excitons in Ge nanocrystals. Instead, observations of similar luminescence in Xe ϩ -implanted samples and reversible PL quenching by hydrogen or deuterium suggest that radiative defect centers in the SiO 2 matrix are responsible for the observed luminescence.

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Electroluminescent devices were fabricated in SiO 2 films containing Ge nanocrystals formed by ion implantation and precipitation during annealing at 900°C, and the visible room-temperature electroluminescence and photoluminescence spectra were found to be broadly similar. The electroluminescent devices have an onset for emission in reverse bias of approximately Ϫ10 V, suggesting that the mechanism for carrier excitation may be an avalanche breakdown caused by injection of hot carriers into the oxide. The electroluminescent emission was stable for periods exceeding 6 h.

In this paper, we present recent work on the design, fabrication, and packaging of a silicon Micro-Electro-Mechanical System (MEMS) microgyroscope designed for space applications. A hermetically sealed package that houses the microgyroscope and most of its control electronics has been built and tested. The entire microgyroscope package is approximately 1 x 1 x 0.7 inches in dimensions. The rest of the control electronics which includes the drive and lock-in amplifier circuitry are mounted outside the gyro box on a 1 x 1 inch circuit board. This packaged microgyroscope has a 7 Hz split between its drive and sense mode and has a scale factor of 24mV/deglsec, bias stability of 70 deghr, angle random walk of 6.3 degldhr, and a rate ramp of 0.2 deglhrlsec. Recent improvements on the fabrication and assembly procedures and microgyroscope design have resulted in cloverleaf structures with matched drive and sense resonant frequency. These new structures have a very small temperature dependent frequency shift of 0.23 Hiddegree for both the drive and sense modes.