Browsing by Author "Wang, Kuang-Yu"

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Annealing effect on the photoluminescence characteristics of ZnO-nanowires and the improved optoelectronic characteristics of p-NiO/n-ZnO nanowire UV detectors
(2015-06-01)
Li, Yu-Ren
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Wan, Chung-Yun
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Chang, Chia-Tsung
;
Huang, Yu-Chin
;
Tsai, Wan-Lin
Transparent ultraviolet (UV) detectors with nanoheterojunctions (NHJs) of p-type NiO and n-type ZnO nanowires (ZnO-NWs) were successfully fabricated using a DC sputtering system and a hydrothermal process, respectively. After annealing in nitrogen ambient, the near-band-edge emission to deep level emission ratio (NBE/DLE) of ZnO-NWs gradually increased as the temperature increased and reached a maximum of 28.9 at a temperature setting of 500 degrees C. In contrast, after annealing in oxygen atmosphere, the NBE/DLE of ZnO-NWs initially increased from 1.2 to 5.9 and then decreased to 3.2. At a reverse bias of 2V, the devices with the 500-degrees C-N-2-annealed ZnO-NWs exhibited better sensitivity (J(UV)/J(Dark) = 5.65; J(Visible)/J(Dark) = 1.35) to UV light (365 nm, 0.3 mW/cm(2)) than those with the as-grown ZnO-NWs (J(UV)/J(Dark) = 4.98; J(Visible)/J(Dark) = 3.82) because the structural defects in ZnO-NWs were effectively eliminated after annealing in nitrogen ambient at 500 degrees C. (C) 2015 The Japan Society of Applied Physics
Conductivity enhancement of multiwalled carbon nanotube thin film via thermal compression method
(2014-08-29)
Tsai, Wan-Lin
;
Wang, Kuang-Yu
;
Chang, Yao-Jen
;
Li, Yu-Ren
;
Yang, Po-Yu
For the first time, the thermal compression method is applied to effectively enhance the electrical conductivity of carbon nanotube thin films (CNTFs). With the assistance of heat and pressure on the CNTFs, the neighbor multiwalled carbon nanotubes (CNTs) start to link with each other, and then these separated CNTs are twined into a continuous film while the compression force, duration, and temperature are quite enough for the reaction. Under the compression temperature of 400 degrees C and the compression force of 100 N for 50 min, the sheet resistance can be reduced from 17 to 0.9 k Omega/sq for the CNTFs with a thickness of 230 nm. Moreover, the effects of compression temperature and the duration of thermal compression on the conductivity of CNTF are also discussed in this work.
Densification effects of the carbon nanotube pillar array on field-emission properties
(2016-06)
Wang, Kuang-Yu
;
Chou, Chia-Hsin
;
Liao, Chan-Yu
;
Li, Yu-Ren
;
Cheng, Huang-Chung
In this study, a simple densification method for carbon nanotube (CNT) pillars is proposed to achieve high-performance field emission characteristics and stable emission. Through capillary force during solution evaporation, the CNT density in each pillar can be increased by about six times without causing damage to the crystallinity of CNTs. The densified CNT pillars exhibit lower series resistance, sharper pillars, better contacts, higher thermal conductivity, and better mechanical stiffness than as-grown ones. Therefore, the threshold field of the field emitter with such CNT pillars of 50 mu m height can be reduced to 1.98 V/mu m, as compared with 2.2V/mu m for the undensified ones. Moreover, the fluctuation of field-emission current decreases from 15.5 to 9.4% after the stress tests at a field of 2V/mu m for 1800 s. These findings imply that the densified CNT pillars are promising for the field-emission applications. (C) 2016 The Japan Society of Applied Physics
Densification effects of the carbon nanotube pillar array on field-emission properties
(2016-06-01)
Wang, Kuang-Yu
;
Chou, Chia-Hsin
;
Liao, Chan-Yu
;
Li, Yu-Ren
;
Cheng, Huang-Chung
In this study, a simple densification method for carbon nanotube (CNT) pillars is proposed to achieve high-performance field emission characteristics and stable emission. Through capillary force during solution evaporation, the CNT density in each pillar can be increased by about six times without causing damage to the crystallinity of CNTs. The densified CNT pillars exhibit lower series resistance, sharper pillars, better contacts, higher thermal conductivity, and better mechanical stiffness than as-grown ones. Therefore, the threshold field of the field emitter with such CNT pillars of 50 mu m height can be reduced to 1.98 V/mu m, as compared with 2.2V/mu m for the undensified ones. Moreover, the fluctuation of field-emission current decreases from 15.5 to 9.4% after the stress tests at a field of 2V/mu m for 1800 s. These findings imply that the densified CNT pillars are promising for the field-emission applications. (C) 2016 The Japan Society of Applied Physics
Effect of oxygen plasma treatment on horizontally aligned carbon nanotube thin film as pH-sensing membrane of extended-gate field-effect transistor
(2015-04-01)
Wang, Kuang-Yu
;
Tsai, Wan-Lin
;
Yang, Po-Yu
;
Chou, Chia-Hsin
;
Li, Yu-Ren
The high-performance pH-sensing membrane of extended-gate field-effect transistors (EGFET) composed of high-conductivity horizontally aligned carbon nanotube thin films (HACNTFs) after oxygen plasma treatment is successfully demonstrated. The 10-mu m-wide catalytic metal lines with 60 mu m interspace produced CNT vertical plates, and the plates were mechanically pulled down and densified to form HACNTFs. A large amount of oxygen-containing functional groups are decorated on the CNTs after the oxygen plasma treatment. These functional groups act as the sensing sites and respond to the H+ or OH- ions in solutions with different pH values. Therefore, these functionalized HACNTFs as pH-EGFET-sensing membranes can achieve a high voltage sensitivity of 40 mV/pH and high current sensitivity of 0.78 mu A(1/2)/pH. Moreover, large linearity of 0.998 is measured in a wide sensing range from pH 1 to 13. These results reveal that the oxygen plasma treatment is an effective way to improve the CNT-sensing characteristics in pH-EGFET sensors. (C) 2015 The Japan Society of Applied Physics
Effects of crystallization mechanism on the electrical characteristics of green continuous-wave-laser-crystallized polycrystalline silicon thin film transistors
(2013-07-29)
Chou, Chia-Hsin
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Lee, I-Che
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Yang, Po-Yu
;
Hu, Ming-Jhe
;
Wang, Chao-Lung
Thin film transistors (TFTs) with amorphous silicon films crystallized via continuous-wave green laser at a wavelength of 532 nm exhibit very different electrical characteristics in various crystallization regions, corresponding to the Gaussian energy density distribution of the laser beam. In the center region subjected to the highest energy density, the full melting scheme led to the best crystallinity of the polycrystalline silicon film, resulting in the highest field-effect mobility of 500 cm(2) V-1 s(-1). In contrast, the edge region that resulted in solid phase crystallization exhibited the worst mobility of 48 cm 2 V-1 s(-1) for the polycrystalline silicon TFTs. (C) 2013 AIP Publishing LLC.
Electrochemical Capacitors of Horizontally Aligned Carbon Nanotube Electrodes with Oxygen Plasma Treatment
(2017-01-01)
Wang, Kuang-Yu
;
Chiu, Yu-Kai
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Cheng, Huang-Chung
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
A electrochemical capacitor (EC) composed of horizontally aligned carbon nanotube (HACNT) electrodes treated with oxygen plasma has been successfully shown to achieve superior specific capacitance. Cyclic voltammetry (CV) measurement reveals that the HACNT thin films on the Si substrate modified by the oxygen plasma with a bias power of 60 W obtain the highest specific capacitance of 6.81 mF/cm(2), which is 5.6 times that of non-plasma-treated ones. Such improvement can be attributed to the increase of oxygen-containing functional groups, such as C-OH, C=O, and COOH as well as to structural defects which remarkably increase the extra redox reactions to enhance the specific capacitance. The electrochemical stabilities of the oxygen-plasma-treated (OPT) HACNT thin films were also verified. Finally, the OPT HACNT thin films were transferred to the flexible PET thin foil and still achieved characteristics similar to those on the hard Si substrate. Even after a bending test of 200 bends with a bending radius of 1 cm and bending angle of 90 degrees, the variation of specific capacitance is less than 3% for such flexible ECs. The electrochemical stability of the OPT HACNT thin films after mechanical bending is equal to that of the Si substrate. This shows that such OPT HACNT ECs have promise for the future flexible applications in the energy storage field. (C) The Author(s) 2017. Published by ECS. All rights reserved.
Flexible Atmospheric-Pressure Gas Ionization Sensors with Horizontally Aligned Carbon Nanotube Electrodes
(2016-12)
Wang, Kuang-Yu
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Tsai, Wan-Lin
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Yang, Po-Yu
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Chou, Chia-Hsin
;
Liao, Chan-Yu
A flexible atmospheric-pressure gas ionization sensor (GIS) with the horizontally aligned carbon nanotube (HACNT) electrodes in the planar structure has been demonstrated for the first time via the proposed rolling-down technique of CNTs. The gap between the electrodes of high-density and uniform HACNTs could be therefore precisely controlled via adjusting the length of the CNTs and the interspacing between the patterned catalysts. High-performance sensing characteristics to various gases Ar, N-2, air, and O-2 at atmospheric pressure with the breakdown voltages as low as 160, 193, 205, and 233, respectively, have been achieved with the electrode gap of 20 mu m. It is attributed to the field enhancement from the small gap and the double-side nanostructures. The superior flexibility of the proposed GIS with different bending tests has also been obtained. It reflects that the HACNTs possess excellent material properties, including great mechanical strength and good electrical conductivity. Such a simple, low-cost, and flexible GIS is promising for its applications in portable and wearable personal monitoring devices.
Functionalized Carbon Nanotube Thin Films as the pH Sensing Membranes of Extended-Gate Field-Effect Transistors on the Flexible Substrates
(2014-07-01)
Tsai, Wan-Lin
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Huang, Bai-Tao
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Wang, Kuang-Yu
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Huang, Yu-Chih
;
Yang, Po-Yu
The oxygen-plasma-functionalized carbon nanotube thin films on the flexible substrates as the pH sensing membranes of extended-gate field-effect transistors are proposed for the first time. The carbon nanotubes are ultrasonically sprayed onto the polyimide substrates followed by an oxygen-plasma functionalization. Such oxygen-plasma-treated carbon nanotube thin films (CNTFs) exhibit superior pH sensing characteristics with the sensitivity of 55.7 mV/pH and voltage linearity of 0.9996 in a wide sensing range of pH 1-13. Moreover, the excellent flexibility of carbon nanotube is also demonstrated and the oxygen-plasma-treated CNTFs still maintain the sensitivity of 53.6 mV/pH and voltage linearity of 0.9943 even after five-cycle bending test. These results reveal that the oxygen-plasma-treated CNTFs have great potentials in the practically disposal and wearable biosensor applications.
High-Performance Single-Crystal-Like Strained-Silicon Nanowire Thin-Film Transistors via Continuous-Wave Laser Crystallization
(2015-04-01)
Chou, Chia-Hsin
;
Chan, Wei-Sheng
;
Lee, I-Che
;
Wang, Chao-Lung
;
Wu, Chun-Yu
High-performance polycrystalline-silicon nanowire (NW) thin-film transistors (TFTs) have been demonstrated via continuous-wave laser crystallization (CLC) to exhibit the low subthreshold swing of 216 mV/decade and high ON/OFF ratio of 1.6x10(9). In addition, the thermal stress of similar to 800 MPa induced from the CLC process also contributed to the single-crystal-like silicon NW CLC TFTs to achieve an excellent field-effect mobility of up to 900 cm(2)V(-1)s(-1).
Highly Sensitive pH Sensors of Extended-Gate Field-Effect Transistor With the OxygenFunctionalized Reduced Graphene Oxide Films on Reverse Pyramid Substrates
(2015-11-01)
Li, Yu-Ren
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Chang, Shih-Hsueh
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Tsai, Wan-Lin
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Chang, Chia-Tsung
;
Wang, Kuang-Yu
The oxygen-plasma-treated reduced graphene oxide films (OPT-RGOFs) as the pH sensing membranes for the extended-gate field-effect transistors were demonstrated to achieve the higher pH sensitivity of 52 mV/pH and better linearity of 0.996 in a wide sensing range of pH 1-13 than those without plasma treatment. It was attributed to the oxygen-containing functional groups on the RGOF induced from the plasma treatment. In addition, the OPT-RGOFs sprayed on the reverse pyramid substrates were also proposed to further enhance the sensing sites, leading to a superior pH sensitivity of 57 mV/pH with an excellent linearity of 0.996.
Laser-unzipped carbon nanotube based glucose sensor for separated structure of enzyme modified field effect transistor
(2013-12-15)
Tsai, Wan-Lin
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Chien, Yun-Shan
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Yang, Po-Yu
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Lee, I-Che
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Wang, Kuang-Yu
A glucose sensing film composed of unzipped multiwalled carbon nanotubes (MWCNTs) via continuous-wave laser irradiation is investigated. Some structural defects decorate on MWCNTs after an acid treatment, and the MWCNTs are unzipped into sheet-shaped layers initiated from these defects after the laser irradiation. The laser-irradiated carbon nanotube thin films (CNTFs) possess higher conductance owing to larger contact area, and the side edges of unzipped CNTs could act as sensing sites for hydrogen ions. Thus the laser-irradiated CNTF as a glucose sensing film could achieve a higher sensitivity of 0.302 mV (mg/dl)(-1), equal to 7.55 mV(mg/dl)(-1) per centimeter square, and a larger linearity of 0.9947 than the as-sprayed one. Moreover, the fully low-temperature processes of this work also reveal the potentials for flexible and disposable biosensors. (C) 2013 Published by Elsevier B.V.
Novel junctionless silicon-oxide-nitride-oxide-silicon memory devices with field-enhanced poly-Si nanowire structure
(2015-08-01)
Chou, Chia-Hsin
;
Chan, Wei-Sheng
;
Wu, Chun-Yu
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Lee, I-Che
;
Liao, Ta-Chuan
In this work, a novel gate-all-around (GAA) low-temperature poly-Si (LTPS) junctionless (JL) silicon-oxide-nitride-oxide-silicon (SONOS) nonvolatile memory device with a field-enhanced nanowire (NW) structure has been proposed to improve the programing/erasing (P/E) performance. Each nanowire has three sharp corners fabricated by a sidewall spacer formation technique to obtain high local electrical fields. Owing to the higher carrier concentration in the channel and the high local electrical field from the three sharp corners, such a JL SONOS memory device exhibits a significantly enhanced P/E speed, a larger memory window, and better data retention properties than a conventional inversion mode NW-channel memory device. (C) 2015 The Japan Society of Applied Physics
Oxygen Plasma Functionalized Multiwalled Carbon Nanotube Thin Film as A pH Sensing Membrane of Extended-Gate Field-Effect Transistor
(2013-10-01)
Tsai, Wan-Lin
;
Huang, Bai-Tao
;
Yang, Po-Yu
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Wang, Kuang-Yu
;
Hsiao, Ching
High-performance pH sening membranes of extended-gate field-effect transistors (EGFETs) composed only of oxygen-plasma-functionalized carbon nanotube thin films (CNTFs) are demonstrated. A large number of oxygen-containing functional groups are decorated on the sidewalls of carbon nanotubes (CNTs) after the oxygen plasma treatment. These functional groups act as the sensing sites and accurately respond to the ions of interest in different pH levels. Therefore, these functionalized CNTFs as the pH-EGFET sensing membranes can achieve a high voltage sensitivity of 56.8 mV/pH, a large voltage linearity of 0.9995, and a wide sensing range of pH 1-13. In addition, the oxygen-plasma-functionalized CNTFs also exhibit superior reliability with a small hysteresis voltage of 4.98 mV.
The mechanism of the surface morphology transformation for the carbon nanotube thin film irradiated via excimer laser
(2013-05-06)
Chien, Yun-Shan
;
Lee, I-Che
;
Yang, Po-Yu
;
Wang, Chao-Lung
;
Tsai, Wan-Lin
In this paper, the surface morphology transformation of the sprayed carbon nanotube (CNT) thin film irradiated with the excimer laser has been systematically investigated. Under the excimer-laser irradiation, two phenomena, including the annealing and ablation effects, were found to be dependent on the incident laser energy and overlapping ratios. Moreover, the extremely high protrusions would be produced in the interface between the annealing and ablation regions. The mechanism of the CNT thin film under the excimer laser irradiation was, therefore, proposed to derive the surface morphology modifications and the further reinforced crystallinity with proper laser energy densities and overlapping ratios. (C) 2013 AIP Publishing LLC.
Thickness effect of NiO on the performance of ultraviolet sensors with p-NiO/n-ZnO nanowire heterojunction structure
(2015-08-01)
Li, Yu-Ren
;
Wan, Chung-Yun
;
Chang, Chia-Tsung
;
Tsai, Wan-Lin
;
Huang, Yu-Chih
Based on the p-NiO/n-ZnO nanowire (NW) heterojunction structure, a high-performance ultraviolet (UV) sensor has been achieved in this work. The sputtered p-type NiO exhibited good coverage on the hydrothermally-grown n-type ZnO Nano-Wires (NW\'s). The devices with 250-nm-thick NiO obtained the highest UV light sensitivity (I-UV/I-Dark = 4.98; I-Visible/I-Dark = 3.82 biased at -2 V) under UV (lambda = 365 nm) intensity as low as 300 mu W/cm(2). Such p-n junction with thinner or thicker NiO layer led to worse UV detecting characteristics due to the fully-depleted NiO layer and larger series resistance, respectively. Furthermore, the N-2 annealing process can increase the UV light response and suppress the visible light response because of the reduced structural defects in ZnO NWs and the fewer interfacial defects (I-UV/I-Dark = 5.65; I-Visible/I-Dark = 1.35 biased at -2 V). (c) 2015 Elsevier Ltd. All rights reserved.