Browsing by Author "Leu, Jih-Perng"

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Fabrication and carbon monoxide sensing characteristics of mesostructured carbon gas sensors
(2009-12-04)
Liu, Chueh-Yang
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Chen, Chia-Fu
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Leu, Jih-Perng
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Lu, Chih-Cheng
;
Liao, Kuan-Hsun
We demonstrated a micro-chemoresistive gas sensing device using mesoporous carbon as the sensitive film and immobilized by dielectrophoresis (DEP) process. The mesoporous materials were characterized by X-ray diffraction (XRD) patterns, N(2) adsorption-desorption isotherms, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). N(2) adsorption-desorption isotherms shows the specific surface area of 1200 m(2)/g, total pore volume is 1.2 cm(3)/g of the mesoporous carbon, and the pore size distribution of mesoporous carbon yields an average pore size of 3 nm. SEM images show a rod-like morphology and TEM images show a highly ordered pore channel with linear arrays. CO gas sensor properties were measured and the resulting sensitivities were 5.7, 6.8, 8.8, 11.6, and 37.6% for concentrations of 30, 45, 60, 75, and 90 ppm. respectively. Additionally, this sensor also exhibited high sensitivity and fast response times for CO gas. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.
Fabrication and CO Sensing Properties of Mesostructured ZnO Gas Sensors
(2009)
Liu, Chueh-Yang
;
Chen, Chia-Fu
;
Leu, Jih-Perng
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材料科學與工程學系
;
Department of Materials Science and Engineering
This study presents the synthesis of mesostructured ZnO using a template replication method and the fabrication of a carbon monoxide sensor using the synthesized ZnO using the dielectrophoresis process. The mesoporous carbon, CMK-3, was employed for the template and zinc nitrite was used as the precursor for synthesizing the ordered porous ZnO. The mesostructured ZnO was analyzed using X-ray diffraction (XRD) patterns, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, and N(2) adsorption-desorption isotherms. The XRD patterns indicated that the ZnO exhibited a highly ordered structure after the template was removed. The morphology of the ZnO was randomly oriented and the structure was polycrystalline. The surface area, pore volume, and pore size of the porous ZnO were 61.3 m(2) g(-1), 0.31 cm(3) g(-1), and 5.3 nm, respectively. When CO gas was injected, the optimum sensitivities at 250 degrees C were 12.1, 14.6, 18.4, 26.0, and 60% when the CO concentrations were 10, 20, 30, 50, and 70 ppm, respectively.
Fabrication of Mesostructured Cobalt Oxide Sensor and Its Application for CO Detector
(2009)
Liu, Chueh-Yang
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Chen, Chia-Fu
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Leu, Jih-Perng
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材料科學與工程學系
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Department of Materials Science and Engineering
The paper presents a method for mesostructured cobalt oxide sensor fabrication by the template replication method and immobilization using dielectrophoresis process. The method consists of enriching the mesostructured cobalt oxide particles in a microelectrode gap that drove mesostructured cobalt oxide particles to a high electric field region and then exposed to CO gas. The cobalt oxide sensor has improved sensing performance in carbon monoxide (CO) detection at concentration as low as 10 ppm and a very short recovering time, due to the higher surface area.
High oriented ZnO films by sol-gel and chemical bath deposition combination method
(2009-05-05)
Cheng, Hua-Chi
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Chen, Chia-Fu
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Tsay, Chien-Yie
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Leu, Jih-Perng
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材料科學與工程學系
Poly-crystalline ZnO films with high oriented columnar grains were deposited on ZnO-coated seed layers by chemical bath deposition (CBD) in an aqueous-solution bath containing zinc nitrate [Zn(NO(3))(2)center dot 6H(2)O], and dimethylamineborane (DMAB) at 60 degrees C without pre-activation especially. Sol-gel ZnO films on glass substrates were used as the seed layers which the mean size of the crystals in seed layer increased from several to approximately 80nm at temperature from 150 degrees C to 550 degrees C. The deposited ZnO films on the ZnO-coated seed surfaces are preferentially on the (0 0 2) plane and exhibit increased from several 10 nm to 150 nm with increasing seed layer grain size. (C) 2008 Elsevier B.V. All rights reserved.
MESOPOROUS CARBON POWDER GAS SENSORS FOR DETECTION OF CARBON MONOXIDE
(2009-12-01)
Lu, Chih-Cheng
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Liao, Kuan-Hsun
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Tsai, Jeff Tsung-Hui
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Liu, Chueh-Yang
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Leu, Jih-Perng
This article reports a new class of silicon-based microgas sensors utilizing hexagonally-ordered mesoporous carbon powders (MCPs) as the sensitive film. The mesoporous carbon powders featuring high-specific surface area are replicated by the SBA-15 silica template and immobilized between Cr electrodes on a 9 x 9 cm silicon chip by using a. c. dielectrophoresis (DEP) process at room temperature. The silicon sensor platform comprises Cr microheaters embedded in a dielectric thin membrane manufactured by microelectromechanical systems back-etching techniques. It is shown that MCPs can be satisfactorily aligned along electric fields and accumulated to the electrode area. Investigations into CO detection are carried out to verify gas-sensitive characteristics of the MCP nanofilm. Our experimental results disclose the mesoporous carbon powders are successfully chemoresistive to CO, and demonstrate distinct resistance change with respect to ppm-level variation. In addition, response time, recovery time, and reproducible sensing behavior are experimentally obtained.
METHOD FOR FORMING A POROUS MATERIAL
(2009-12-31)
Leu, Jih-Perng
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Hsu, Kuo-Yuan
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Hsu, Hsin-Ling
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Chen, Guan-Yu
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Takasaka, Nobuo
A method for forming a porous material is to mix a porous first basic material with a sacrificial material compatible with the first basic material to let the sacrificial material permeate into the pores of the first basic material to form a first finished product. Subsequently, the first finished product is mixed with a second basic material and heated over the vaporization temperature of the sacrificial material to let the ingredients of the second basic material change and increase viscous force and impossible to enter the pores of the first basic material. Simultaneously, the sacrificial material is heated and vaporized to exhaust out of the pores of the first basic material, disabling the second basic material to permeate into the pores of the first basic material and thus forming a second finished product for reserving the ingredients in the pores of the first basic material.
Pore size evaluation of mesoporous organosilicate films by non-destructive X-ray reflectivity methods
(2015-06-01)
Chien, Yun-San
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Yeh, Yu-Shan
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Chen, Yen-Song
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Leu, Jih-Perng
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Fu, Wei-En
200-nm-thick organosilicate films deposited by mixture of tetraethyl orthosilicate (TEOS) and methyltrimethoxysilane (MTMS) dissolving in different cetrimonium bromide (CTAB)/ethanol ratios were characterized in terms of pore size determination and its distribution. Under the toluene ambient, the pores would adsorb the gas hence elevating the whole film density. The X-ray reflectivity (XRR) equipped with mass flow control was utilized to detect the film density increasing. By fitting with Gaussian function and conversing with Kelvin\'s equation, the pore size was increased from 6.2 to 10.8 angstrom as the CTAB/ethanol ratio increasing to 0.075. It was attributed to the ethanol and CTAB enhanced the TEOS hollow droplets stability and dissolvability. As the CTAB/ethanol ratio is further increased, the pore size is reversely decreased, owing to the formation of solid microspheres. The non-destructive XRR measurement can evaluate the sub-nano pore sizes and its size distribution, which would fascinate the development and characterization of back-end of line process. (C) 2015 The Japan Society of Applied Physics
Tunable interconnectivity of mesostructured cobalt oxide materials for sensing applications
(2009-04-02)
Liu, Chueh-Yang
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Chen, Chia-Fu
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Leu, Jih-Perng
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材料科學與工程學系
;
Department of Materials Science and Engineering
A mesostructured cobalt oxide microsensor was fabricated using a template replication method under different hydrothermal treatments, and attempts were made to enhance the response of this gas sensor. To evaluate the sensing performance, the sensing materials were deposited via the dielectrophoresis (DEP) process, on micro-hot-plate platforms with interdigitated electrodes. The resistance changed when the carbon monoxide target gas was injected at the optimum temperature. The mesostructured cobalt oxide material with high hydrothermal treatment revealed the well-ordered domains, whereas with low hydrothermal treatment it did not contain ordered domains. Moreover, the cobalt oxide high hydrothermal material had 1.5 times the response to 70 ppm carbon monoxide as the low hydrothermal treatment sample. The unobstructed interconnectivity promotes gas diffusion and increases the active surface areas. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.