Browsing by Author "Liu, Chien-Cheng"

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Dynamics and reversibility of oxygen doping and de-doping for conjugated polymer
(2008-05-15)
Liao, Hua-Hsien
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Yang, Chia-Ming
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Liu, Chien-Cheng
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Horng, Sheng-Fu
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Meng, Hsin-Fei
We perform comprehensive long-time monitoring of the p-doping and de-doping of poly(3-hexyl thiophene) under changing external conditions of oxygen, light, and temperature. They are shown to be controlled by the complex adsorption and desorption process with time scales ranging from seconds to weeks. The oxygen doping at atmospheric pressure takes several hours in the dark. The doping is dramatically accelerated to be within seconds with light of wavelength of 500-700 nm. Even at low oxygen pressure of 10(-4) torr doping occurs within minutes with light. The de-doping by oxygen desorption takes as long as weeks at room temperature and vacuum of 10(-4) torr, but when the temperature is raised to near the polymer glass temperature of 370 K, the de-doping is accelerated to minutes as the enhanced chain motion releases the trapped oxygen. Even though visible and near infrared light causes very efficient doping within seconds or minutes depending on vacuum level, such light-induced doping is not a chemical reaction and is fully reversible by thermal annealing at the end without sacrificing the mobility. For the polymer field-effect transistors, only the carrier density is changed while the mobility remains roughly a constant for all the conditions. (c) 2008 American Institute of Physics.
Effect of gate metal on polymer transistor with glass substrate
(2006-12-11)
Meng, Hsin-Fei
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Liu, Chien-Cheng
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Jiang, Chin-Jung
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Yeh, Yu-Lin
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Horng, Sheng-Fu
Poly(3-hexylthiophene) (P3HT) field-effect transistors (FETs) are fabricated on glass substrates with SiO2 as a gate dielectric over the gate. Indium tin oxide (ITO), Al, and Cr are employed as gate metals. For spin-coated FET, the mobility increases from 10(-4)-10(-5) cm(2)/V s for ITO and Al gates to 10(-2) cm(2)/V s for Cr gate. After O-2 plasma treatment, the SiO2 roughness can be made as low as 0.7 nm. The mobility is further improved up to 0.3 cm(2)/V s by dip-coating P3HT. "Crossed rods" such as morphology can be observed in dip-coated FET with high mobility, indicating high degree of self-assembly facilitated by the flat SiO2 surface over Cr gate. (c) 2006 American Institute of Physics.
Interface effect of oxygen doping in polythiophene
(2009-06-01)
Liu, Chien-Cheng
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Yang, Chia-Ming
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Liu, Wen-Hsing
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Liao, Hua-Hsien
;
Horng, Sheng-Fu
Long-time evolution of the electrical characteristics for two-terminal and transistor of poly(3-hexylthiophene) film with various gate dielectric interfaces are measured. The oxygen doping is found to depend sensitively on the amount of hydroxyl groups of the interface and irreversible after long time in vacuum except for quartz. For a given interface, dip-coated film always has a higher doping level and slower de-doping than spin-coated films because of higher porosity. With careful control of the oxygen level transistor with mobility of 0.12 cm(2)/V s and on-off ratio of 29,000 are obtained for dip-coated film on glass substrate. (C) 2009 Elsevier B.V. All rights reserved.
LABEL-FREE SENSOR
(2010-09-23)
Meng, Hsin- Fei
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Hong, Sheng-Fu
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Chao, Yu-Chiang
;
Liu, Chien-Cheng
;
Liu, Wen-Hsing
A label-free sensor is disclosed. The label-free sensor comprises a substrate, a first electrode formed on the substrate, a second electrode formed on the substrate and spaced away from the first electrode, and a semiconductor layer formed on the substrate and is in contact with the first electrode and the second electrode, wherein the semiconductor layer has a plurality of probe groups, which are bonded to the semiconductor layer by functionalization, for sensing a coupling-specific substance, which has bonding specificity with the probe groups. The semiconductor layer of the label-free sensor of the present invention is bonded with probe groups, and the detection of detected object is performed in instant, quick, rapid, and sensitive manner by measuring variation in electric current, thereby avoiding the use of the fluorescent reading equipment for reading fluorescent signals.
Selective real-time nitric oxide detection by functionalized zinc oxide
(2009-08-07)
Liu, Chien-Cheng
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Li, Jan-Hao
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Chang, Cheng-Chung
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Chao, Yu-Chiang
;
Meng, Hsin-Fei
Ferriprotoporphyrin IX chloride (haemin)-functionalized Al-doped zinc oxide (ZnO) is used for nitric oxide (NO) sensing at room temperature. The devices show high selectivity to NO against CO(2) and O(2). There is no such selectivity without haemin. Porous ZnO film made by a polystyrene sphere template is used to provide a high surface area. In comparison with non-porous ZnO film with low surface area, both the sensitivity and the response speed of the sensor made by porous ZnO are clearly improved. NO concentration down to 1 ppm can be detected. The response time is 20 s. The sensor is reversible after purging with pure nitrogen for about 100 s. Such a device is able to detect real-time variation of NO which is a vital physiological signalling molecule.