A power MEMS is a micro-electromechanical system to supply electric power or kinetic power. The power MEMS for electric power supply is attractive as a portable power source replacing batteries. State-of-the-art batteries suffer from insufficient energy and power density. The secondary battery needs time-consuming recharge at the place where a facility electric line is available. Moreover, recycling batteries is limited due to difficulties in balancing the cost and classifying many kinds of used batteries, although used batteries are accompanied with such problems as environmental pollution. The power MEMS is expected to realize new functions, such as high energy density, high power density, continuous operation without recharge and environmental friendliness, not found in batteries by using chemical fuels with energy density 1-2 digits higher than batteries or environmental energy. Another important application of the power MEMS is a micro-thruster for 1-10 kg class micro-spacecrafts. Currently, fuel cells, fuel reformers, combustion engine generators, combustion-based thermoelectric generators and thrusters are being miniaturized using MEMS technology. Also, ceramic micromachining for high-temperature power MEMS is under development.

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Photo-diodes with vertical overflow drain has been used to suppress blooming. The γ characteristics at the saturation region of the diodes is important factor to minimize smear and to expand dynamic range for incident light. However, the characteristics have not been analyzed yet. In this paper, we have clarified the dependence of γ characteristics on the substrate impurity profile that is most important design parameter in the diode from view point of γ control. The γ characteristics were calculated by one dimensional analysis to understand how the characteristics are decided and by three dimensional numerical analysis to obtain more exact results. The analyses indicate that γ characteristics became lager for the lower substrate density. However, lower substrate density brings about high reset voltage. To reduce reset voltage while keeping large γ characteristics, we proposed photo-diodes with three substrate layers, and succeeded, in simulation, to realize both characteristics at a same time.

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Frequency shift measurement circuit with high sampling rate using reciprocal method for QCM odor sensor is proposed. Although the circuit including an analog-type mixer achieved the high sampling rate, the digital mixer in place of analog one is required since all the circuits can be implemented into one chip. The proposed digital mixer helped us achieve 128ms time resolution, 8 times faster than the conventional one, without the deterioration of the frequency resolution. Then, it was found that its introduction into the gas odor visualization system enabled us to have clear image. After the successful implementation into a FPGA, its ASIC version was fabricated. The increase in the mixer performance brought us further increase in the sampling rate of the frequency shift.

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The authors produced a driving circuit for resistive humidity sensor using the timer IC and applied it to the thermo-hygrometer. This paper describes as follows: (1) a simple driving circuit using the timer IC was produced and the theoretical equation of its oscillating frequency was derived. (2) relative humidity as low as 10 %RH could be measured using the driving circuit for resistive humidity sensor. (3) the measurement error of the thermo-hygrometer using the driving circuit was achieved within ± 3 %RH above 30 %RH.

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Lattice-mismatched InGaAs photodiodes with low dark current and very wide wavelength spectral response for near-infrared spectroscopy applications are presented. We have demonstrated almost complete relaxation of the strain by using the composition-graded InAsP buffer and also shown good reproducibility of the PD fabrication process.

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The design concept and theoretical investigation of a micro multi-axis force-moment sensor utilizing the piezoresistive effect in silicon are described. The purpose of the sensor development is to measure the force and moment acting on boundary particles in a turbulent liquid flow. The sensor is designed to independently detect 3 components of force and 3 components of moment in three orthogonal directions. Conventional p-type and four-terminal p-type piezoresistors have been combined in a single sensing chip in the plane (111) of silicon.

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Effects of aluminum (Al) addition on variations in electrical properties of silicon carbide (SiC) ceramics were investigated. In this study, SiC ceramics added Al in the range from 0 to 0.6 mass% were sintered at 2273 K for 1 hour. The resistance (R) and thermistor constant (Bt) were measured, through which their averages and variations were obtained. As the amount of the Al addition increased, the variations of R and Bt increased. It was suggested that the increase of the microstructural variation causes the increase of the electrical variation in SiC ceramics.

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