UV response of ZnO nanowire nanosensor has been studied under ambient condition. By utilizing Schottky contact instead of Ohmic contact in device fabrication, the UV sensitivity of the nanosensor has been improved by four orders of magnitude, and the reset time has been drastically reduced from ϳ417 to ϳ0.8 s. By further surface functionalization with function polymers, the reset time has been reduced to ϳ20 ms even without correcting the electronic response of the measurement system. These results demonstrate an effective approach for building high response and fast reset UV detectors. © 2009 American Institute of Physics. ͓DOI: 10.1063/1.3133358͔ Ultraviolet ͑UV͒ photon detectors have a wide range of applications from environmental monitoring, missile launching detection, space research, high temperature flame detection to optical communications.1 For these applications, fast response time, fast reset time, high selectivity, high responsivity, and good signal-to-noise ratio are commonly desired characteristics.2 For UV photon detector based on polycrystalline ZnO thin film, a slow response time ranging from a few minutes to several hours is commonly observed.3,4 Due to large surface-to-volume ratio and reduced dimensionality of the active area, ZnO nanostructures are expected to have high photon conductance.5 Kind et al. 6 reported the photon response of a single ZnO nanowire ͑NW͒ under UV illumination, which has also been studied by other groups.7-9 Most of the studies have been focused on the mechanism investigation 10,11 and improving the sensitivity. 9,12 For example, Lao et al. 9 have improved the sensitivity of the ZnO NW UV nanosensor ͑NS͒ for five orders of magnitude by functionalizing the surface of ZnO nanobelts using polymers that have a high absorption at the UV range. However, little attention has been paid on improving the response and recovery time 13 especially the reset time ͑defined as the time need to recovery to 1 / e ͑37%͒ of the maximum photocurrent͒.In this letter, we demonstrate effective ways for improving both the sensitivity and reset time of ZnO NW NSs. By fabricating Schottky type ͑ST͒ devices instead of Ohmic type ͑OT͒ devices, the UV sensitivity of ZnO NW NS has been improved for four orders of magnitude, and the reset time has been decreased from ϳ417 to ϳ0.8 s. By further surface coating with positive charged poly͑diallydimethylammonium chloride͒ ͑PDADMAC͒ and negative charged poly͑sodium 4-styrenesulfonate͒ ͑PSS͒, the reset time has been decreased to ϳ20 ms even without correcting the electronic response of the measurement system. The ZnO NWs for the NS fabrication were synthesized by thermal evaporation of ZnO powders without using any catalyst.14 UV response of our devices was characterized by a portable UV lamp ͑Spectroline, Model ENF-280C, 365 nm͒. The photon-response spectrum measurement was carried out in a PTI QuantaMaster Luminescence ͑QM 3PH͒ system. All of the measurements were carried out at room temperature in ambient condition.We first studied the performance of...

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Piezoelectric materials have been integrated with silicon microelectromechanical systems (MEMS) in both microsensor and microactuator applications. Thin-film materials selection and processing routes are reviewed. Some recent and emerging applications of piezoelectric MEMS are presented including acoustic emission microsensors, vibration monitors, molecular recognition biosensors, precision positioners, micropumps, and linear stepper motors.