Browsing by Author "Hsu, Nai-Feng"

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A rapid synthesis/growth process producing massive ZnO nanowires for humidity and gas sensing
(2014-09-01)
Hsu, Nai-Feng
;
Chung, Tien-Kan
;
機械工程學系
;
Department of Mechanical Engineering
We report a rapid and simple process to massively synthesize/grow ZnO nanowires capable of manufacturing massive humidity/gas sensors. The process utilizing a chemical solution deposition with an annealing process (heating in vacuum without gas) is capable of producing ZnO nanowires within an hour. Through depositing the ZnO nanowires on the top of a Pt-interdigitated-electrode/SiO2/Si-Wafer, a humidity/gas-hybrid sensor is fabricated. The humidity sensitivity (i.e., ratio of the electrical resistance of the sensor at 11-95 % relative humidity level) is approximately 10(4). The response and recovery time with the humidity changing from 11 to 95 % directly and reversely is 6 and 10 s, respectively. The gas sensitivity (i.e., ratio of electrical resistance of the sensor under the air to vaporized ethanol) is increased from 2 to 56 when the concentration of the ethanol is increased from 40 to 600 ppm. Both the response and recovery times are less than 15 s for the gas sensor. These results show the sensor utilizing the nanowires exhibits excellent humidity and gas sensing.
A rapid synthesis/growth process producing massive ZnO nanowires for humidity and gas sensing
(2014-09-01)
Hsu, Nai-Feng
;
Chung, Tien-Kan
;
機械工程學系
;
Department of Mechanical Engineering
We report a rapid and simple process to massively synthesize/grow ZnO nanowires capable of manufacturing massive humidity/gas sensors. The process utilizing a chemical solution deposition with an annealing process (heating in vacuum without gas) is capable of producing ZnO nanowires within an hour. Through depositing the ZnO nanowires on the top of a Pt-interdigitated-electrode/SiO2/Si-Wafer, a humidity/gas-hybrid sensor is fabricated. The humidity sensitivity (i.e., ratio of the electrical resistance of the sensor at 11-95 % relative humidity level) is approximately 10(4). The response and recovery time with the humidity changing from 11 to 95 % directly and reversely is 6 and 10 s, respectively. The gas sensitivity (i.e., ratio of electrical resistance of the sensor under the air to vaporized ethanol) is increased from 2 to 56 when the concentration of the ethanol is increased from 40 to 600 ppm. Both the response and recovery times are less than 15 s for the gas sensor. These results show the sensor utilizing the nanowires exhibits excellent humidity and gas sensing.
Rapid Synthesis of Piezoelectric ZnO-Nanostructures for Micro Power-Generators
(2013-10-01)
Hsu, Nai-Feng
;
Chung, Tien-Kan
;
Chang, Ming
;
Chen, Hong-Jun
;
機械工程學系
In this paper, we report a rapid synthesis of piezoelectric ZnO-nanostructures and fabrication of the nanostructures-based power-generators demonstrating an energy conversion from an environmental mechanical/ultrasonic energy to an electrical energy. The ZnO nanostructures are grown on a silicon wafer by a modified chemical solution method (CSD, chemical-solution-deposition) with a two-step thermal-oxidation approach. The synthesis process can be completed within 1 h. By varying the mixture-ratio of Zn micro-particles in an oxalic acid solution with 0.75 mol/l concentration in the CSD process, the growth mechanism is well-controlled to synthesize three different types of ZnO-nanostructures (i.e., dandelion-like nanostructures, columnar nanostructures, and nanowires). Furthermore, through oxidizing at different temperatures in the thermal-oxidation process, the featured geometry of the nanostructures (e. g., the length and diameter of a nanowire) is modified. The geometry, size, morphology, crystallization, and material phase of the modified nanostructures are characterized by scanning electron microscopy and X-ray diffraction. Finally, the nanostructures are used to fabricate several micro power-generators. Through the piezoelectric effect, a maximum current density output of 0.28 mu A cm(-2) generated by a power-generator under an ultrasonic wave is observed.