Piezoelectric lead zirconate titanate (PZT) thin film has been widely studied in microelectromechanical systems (MEMS) as an electromechanical conversion material. However, the application of the piezoelectric MEMS devices is still delayed by PZT integration difficulties, especially in PZT etching process. In this study, PZT thin film was etched using Ar/SF₆ mixed gas in a conventional ICP-RIE system. The etch rate, etch selectivity and profile of the PZT film as well as platinum bottom electrode and photoresist were investigated as a function of the Ar concentration (Ar %) in Ar/SF₆ mixture. The surface roughness, ferroelectric properties and dielectric properties of the PZT film were evaluated to indentify the effects of various etching receipts. It was found that high Ar % resulted in better PZT surface morphology. The largest PZT etch rate was achieved at 66.7 % of Ar. Reactive-physical mixed etching was preferred for great efficiency, but at the cost of bad surface roughness and low etch selectivity. Moreover, the ferroelectric properties and the dielectric properties of the PZT film were found not degraded by the proposed process. Fine PZT-electrode stack with the feature size of 15 μm and the PZT thickness of 1 μm was successfully obtained in this paper for piezoelectric MEMS application.

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The response characteristics of a proton pumping gate FET (PPG-FET) with a triple layer gate structure (Pd/proton conducting polymer/Pt) to various gases were investigated. Two kinds of hydrogen response signals (DC and AC) were obtained from the PPG-FET when the AC bias voltage was applied between the gate electrodes of the PPG-FET. The DC signals showed high hydrogen sensitivities and the sensitivities were about -30 mV/decade. Additionally, the AC signal decreased by 10 mV with increase in the hydrogen concentration from 100 ppm to 10%. Whereas the DC signals decreased slightly with increasing oxygen concentration, the oxygen response was much smaller than the DC hydrogen sensitivities. In contrast, the AC signal hardly responded to oxygen. This is because a proton conducting polymer layer prevents the movement of oxygen ions. Additionally, the proton pumping gate FET showed good selectivity against other gases (methane, ethane, ammonia, and methanol). These results clarify the high hydrogen sensitivity of the PPG-FET in an AC modulation mode.

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The setup, micro-droplet sampling system combined with a gas-flow system for measurement using laser-induced breakdown spectroscopy (LIBS) is introduced. This setup was designed for high sensitive quantitative analysis using ink-jet technology and gas-flow assistance. The setup presented here allowed precise detection of a uniform volume of 30-μm micro-droplet location for guiding it into a 53.2-μm beam spot area, under the effects of any ambient gas. In this paper, experimental results with the use of two kind of ambient gasses; air and argon gas, were compared in order to find proper time-delay values for time-resolving spectroscopy. From time-gated spectroscopy analysis of these experiments, different relaxation time spectral data were obtained. This result indicates that in the case of using argon ambient for assistance, broader range of time-gate setting is required as compared with the case of using air ambient. Sensitive LIBS measurement for trace elements was shown by using the proper gate-setting value.

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We fabricated an antireflection subwavelength grating (SWG) on a Si micro lens for an optical scanner at optical communication wavelengths. The optical scanner mainly consisted of the micro lens, comb electrodes, and springs, which were formed on a Si layer. A Pyrex glass was used as a substrate and bonded with the Si layer. The optical characteristics of the SWG were calculated using rigorous coupled-wave analysis. The SWG was successfully fabricated on the micro lens with the diameter of 250 μm and the height of 12 μm. The optical scanner with the micro lens was fabricated with high accuracy. We observed that the micro lens with the SWG had higher transmittance compared with that without the SWG. Using the optical scanner without the SWG on the micro lens for only confirming the actuation characteristics, the scanning angle was measured. When the micro lens moved 50 μm at the voltage of 100 V, the scanning angle of 2.53° was achieved, which almost agreed with the calculation value.

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