Browsing by Author "Sung, Chao-Feng"

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Flexible Fullerene Field-Effect Transistors Fabricated Through Solution Processing
(2009-12-18)
Sung, Chao-Feng
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Kekuda, Dhananjay
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Chu, Li Fen
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Lee, Yuh-Zheng
;
Chen, Fang-Chung
C60-based thin-film transistors are fabricated through solution processing. On rigid indium tin oxide (ITO) glass, the transistors display electron mobilities as high as 0.21 cm(2) V(-1) s(-1) and a threshold voltage of 0.7V, only slightly lower than those of organic thin-film transistors prepared through vacuum deposition. On ITO-coated PET substrates, the mobilities in the flexible devices (see image) are approximately one order of magnitude lower than those of devices prepared on rigid glass substrates.
Flexible Fullerene Field-Effect Transistors Fabricated Through Solution Processing (vol 21, pg 4845, 2009)
(2010-12-01)
Sung, Chao-Feng
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Kekuda, Dhananjay
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Chu, Li Fen
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Lee, Yuh-Zheng
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Chen, Fang-Chung
Flexible Organic Thin Film Transistors Incorporating a Biodegradable CO2-Based Polymer as the Substrate and Dielectric Material
(2018-05-25)
Rullyani, Cut
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Sung, Chao-Feng
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Lin, Hong-Cheu
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Chu, Chih-Wei
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材料科學與工程學系
Employing CO2-based polymer in electronic applications should boost the consumption of CO2 feedstocks and provide the potential for non-permanent CO2 storage. In this study, polypropylene carbonate (PPC) is utilized as a dielectric and substrate material for organic thin film transistors (OTFTs) and organic inverter. The PPC dielectric film exhibits a surface energy of 47 mN m(-1), a dielectric constant of 3, a leakage current density of less than 10(-6) A cm(-2), and excellent compatibility with pentacene and PTCDI-C8 organic semiconductors. Bottom-gate top-contact OTFTs are fabricated using PPC as a dielectric; they exhibits good electrical performance at an operating voltage of 60 V, with electron and hole mobilities of 0.14 and 0.026 cm(2)V(-1)s(-1), and on-to-off ratios of 105 and 103, respectively. The fabricated p-and n-type transistors were connected to form a complementary inverter that operated at supply voltages of 20 V with high and low noise margins of 85 and 69%, respectively. The suitability of PPC as a substrate is demonstrated through the preparation of PPC sheets by casting method. The fabricated PPC sheets has a transparency of 92% and acceptable mechanical properties, yet they biodegraded rapidly through enzymatic degradation when using the lipase from Rhizhopus oryzae.
Hybrid TiO(x)/fluoropolymer bi-layer dielectrics for low-voltage complementary inverters
(2010-01-01)
Sung, Chao-Feng
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Kekuda, Dhananjay
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Chu, Li Fen
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Chen, Fang-Chung
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Cheng, Shiau-Shin
In this article, low temperature processed, reactively evaporated titanium oxide layers were utilized as gate dielectrics for achieving low voltage driven transistors and complementary inverters. The surface of the gate dielectric was modified by an ultra thin (similar to 30 nm) fluoropolymer Cytop (R) layer which partially helped to reduce the leakage in the dielectric films and also enhanced the organic transistor performance. The current investigation demonstrates the ability of these high capacitance bi-layer dielectrics (k similar to 20). The combined p-type and n-type field-effect transistors show similar saturation mobility similar to 0.3 cm(2)/Vs to achieve low voltage driven complementary circuits with output gain of 22. Low temperature processing of these dielectric layers make them easily integrated. (C) 2009 Elsevier B.V. All rights reserved.
Hybrid TiOx/fluoropolymer bi-layer dielectrics for low-voltage complementary inverters
(2010-01-01)
Sung, Chao-Feng
;
Kekuda, Dhananjay
;
Chu, Li Fen
;
Chen, Fang-Chung
;
Cheng, Shiau-Shin
In this article, low temperature processed, reactively evaporated titanium oxide layers were utilized as gate dielectrics for achieving low voltage driven transistors and complementary inverters. The surface of the gate dielectric was modified by an ultra thin (similar to 30 nm) fluoropolymer Cytop (R) layer which partially helped to reduce the leakage in the dielectric films and also enhanced the organic transistor performance. The current investigation demonstrates the ability of these high capacitance bi-layer dielectrics (k similar to 20). The combined p-type and n-type field-effect transistors show similar saturation mobility similar to 0.3 cm(2)/Vs to achieve low voltage driven complementary circuits with output gain of 22. Low temperature processing of these dielectric layers make them easily integrated. (C) 2009 Elsevier B.V. All rights reserved.
Improved performance in n-channel organic thin film transistors by nanoscale interface modification
(2008-04-01)
Chu, Chih-Wei
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Sung, Chao-Feng
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Lee, Yuh-Zheng
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Cheng, Kevin
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光電工程學系
We demonstrate that the electrical properties of n-channel thin film transistors can be enhanced by inserting a nanoscale interfacial layer, namely, cesium carbonate (Cs2CO3) between organic semiconductor and source/drain electrodes. Devices with the Cs2CO3/Al electrode showed a reduction of contact resistance, not only with respect to Al, but also compared to Ca. The improvement is attributed to the reduction in the energy barrier of electron injection and the prevention of unfavorable chemical interaction between the organic layer and the metal electrode. High field-effect mobility of 0.045 cm (2)/V s and on/off current ratios of 10(6) were obtained in the [6,6]-phenyl C60 butyric acid methyl ester-based organic thin film transistors using the Cs2CO3/Al electrodes at a gate bias of 40 V. (c) 2007 Elsevier B.V. All rights reserved.
Natural polymers for disposable organic thin film transistors
(2018-03-01)
Rullyani, Cut
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Ramesh, Mohan
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Sung, Chao-Feng
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Lin, Hong-Cheu
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Chu, Chih-Wei
In this study, eco-friendly PTCDI-C8-based organic thin film transistors (OTFTs) were fabricated by incorporating polymers from renewable sources as gate dielectrics and substrates. Chitosan, a polysaccharide obtained from the deacetylation of chitin, and natural rubber (NR), extracted from natural rubber tree, have good dielectric properties, biocompatibility, and biodegradability. To examine the practical applicability of these materials, we fabricated OTFTs using bilayer PVPy/NR and chitosan/NR films as gate dielectric materials. NR not only improved the insulation properties of the dielectric film but also acted as a surface modifier. The fabricated OTFT incorporating chitosan/NR dielectric operated under a low driving voltage, with values of mu and V-th of 0.027 cm(2)V(-1)s(-1) and 0.83 V, respectively. It also displayed an electrical response in the presence of DNA at different concentrations. Because, chitosan possesses high transparency and good mechanical properties, it can be readily cast to form transparent flexible substrates. Accordingly, a flexible disposable OTFT device was fabricated using PVPy/NR as the dielectric material on chitosan as the substrate. The disposable device exhibited a carrier mobility of 0.011 cm(2)V(-1)s(-1), a value of V-th of 0.83 V, and an on/off ratio of 10(3), while being workable over 100 bending cycles.
Stimuli-responsive polymer as gate dielectric for organic transistor sensors
(2020-10-01)
Rullyani, Cut
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Singh, Mriganka
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Li, Sheng-Han
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Sung, Chao-Feng
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Lin, Hong-Cheu
Temperature is a characteristic often correlated with environmental and health issues. This paper presents an organic thin film transistor (OTFT) based temperature sensor having a detection range of 30-45 degrees C, which, therefore, encompasses the human body temperature. The OTFT sensor featured thermosensitive poly(N-iso-propylacrylamide) (PNIPAM) and pentacene as the gate dielectric and semiconductor, respectively. The PNIPAM film possessed a dielectric constant of 4.2 with very low leakage current density. The OTFT exhibited high electrical performance, with a hole mobility (mu) of 0.90 +/- 0.04 cm(2) V-1 s(-1), a threshold voltage (V-th) of -15.4 +/- 1.16 V, and an on/off ratio of 10(4). Significant changes in the drain current and the values of V-th and mu occurred when the temperature of the device was varied within the range 30-45 degrees C at an interval of 0.5 degrees C. The operating principle for this temperature sensor was based on the structural transformation of the PNIPAM dielectric and the enhanced charge transport of the pentacene semiconductor upon varying the temperature. Flexible OTFTs fabricated on polyethylene terephthalate substrate displayed hole mobilities as high as 0.39 +/- 0.01 cm(2) V-1 s(-1), values of V-th of 18.6 +/- 0.45, and on/off ratios of 10(2), and were workable for over 100 bending cycles.