A tubular sensor using yttria-stabilized zirconia ͑YSZ͒ and a spinel-type oxide sensing-electrode ͑SE͒ was fabricated and examined for NO x detection at high temperatures. Among spinel-type oxides tested and reported in the literature to date, ZnFe 2 O 4 has the highest sensitivity to NO 2 in air at temperatures of 550-700°C. In this temperature range, the electromotive force ͑emf͒ response of the sensor was almost linear to the logarithm of NO or NO 2 concentration in the range from 25 to 436 ppm. Scanning electron microscopy and X-ray diffraction analysis were used to examine the morphology and crystalline structure of the ZnFe 2 O 4 film. Investigation of the sensor stability showed that the output emf to 100 ppm NO 2 have been gradually increased within ϳ20% range after ϳ20 day operation up to 200 days examined at 700°C in dry synthetic air. The air base has been stable during the whole test period.The nitrogen oxides, NO and NO 2 , abbreviated as NO x , emitted from automobile engines and boilers are a major source of atmospheric pollution. To solve effectively the NO x problems related to car exhausts, it is necessary to develop a compact solid-state NO x sensor capable of working at high temperatures. If a highperformance NO x sensor is installed in the vehicle, it can be used for an on-board diagnosis of a de-NO x catalyst. By detecting the NO x concentration after the NO x storage catalyst, it will be possible to optimize the timing of regeneration of the catalyst by the flow of fuel-rich gas.Many solid electrolyte potentiometric 1-6 and amperometric 7-11 NO x sensors based on the yttria-stabilized zirconia ͑YSZ͒ and metal oxide sensing electrode ͑SE͒ have been developed and reported to date. Some sensors using an oxide SE, such as CdMn 2 O 4 1 and CdCr 2 O 4 , 4 are based on a sensing mechanism involving mixed potential and can detect NO or NO 2 in oxygen containing atmospheres at 550-650°C. Unfortunately, the sensitivity of these sensors to NO x is still low at temperatures above 600°C. This suggests the importance of further search of SE materials. The geometry and morphology of electrode materials will influence the mixed potential response. The mass production of reproducible electrode structures as well as the long-term stability of the electrodes at elevated temperatures should be established for commercialization of the sensors. The substitution of refractory oxide electrodes for metal electrodes offers promise in improving the selectivity and the long-term stability of these sensors. The selection of metal oxide SE, therefore, is vital to obtain excellent sensing performance. Ongoing research is concentrated mainly on obtaining incremental improvements in the sensing properties of these oxides. Any increases in the sensitivity and selectivity to NO 2 or ͑NO͒ at high temperature are important in terms of enhancing the performance of NO x sensors. Moreover, any increase in the stability of the NO x sensor by manufacturing technology or by careful selection of the SE materials has a considerable ef...

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The hot-carrier (HC) instability for surface channel PMOS is investigated intensively. We found from experimental data for the first time that hot-carrier injection is occurring at the center of channel at most serious stress condition of Vgs=Vds and that a physical mechanism similar to NBTI is responsible for degradation at room temperature, and confirmed from hydrodynamic simulations. We demonstrate that mechanical stress resulting from sidewall spacer accelerates this anomalous degradation in shokchannel PMOS under hot-carrier stress. We show management of this degradation mechanism is crucial and indispensable for achieving high reliability of future generation PMOS devices.

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