Browsing by Author "Tsai, Wan-Lin"

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A Novel pH Sensor of Extended-Gate Field-Effect Transistors With Laser-Irradiated Carbon-Nanotube Network
(2012-11-01)
Chien, Yun-Shan
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Tsai, Wan-Lin
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Lee, I-Che
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Chou, Jung-Chuan
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Cheng, Huang-Chung
The extended-gate field-effect transistors (EGFETs) with only the carbon-nanotube (CNT) thin film as both the sensing membrane and the contact electrode have been demonstrated for the first time to exhibit superior pH sensing characteristics. The continuous-wave laser was necessary to improve the pH sensitivity to be 50.9 mV/pH and the linearity values to be 0.9978 for pH = 3 to pH = 13 wide sensing range, respectively. It implied that the laser energy would unzip the chemically modified multiwalled CNTs (MWCNTs) into numerous graphite slices, resulting in the elevated sensing sites and the improved electrical and sensing properties. Therefore, the laser-irradiated MWCNT network is promising for the applications in the flexible and transparent pH-EGFETs.
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
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Huang, Yu-Chin
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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
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Wang, Kuang-Yu
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Chang, Yao-Jen
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Li, Yu-Ren
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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.
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
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Tsai, Wan-Lin
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Yang, Po-Yu
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Chou, Chia-Hsin
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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
Field Emission Properties of Carbon Nanotube Arrays on the Thickness-Controlled Flexible Substrate by the Pattern Transfer Process
(2012-07-01)
Chang, Chia-Tsung
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Juan, Chuan-Ping
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Lin, Yi-Chan
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Li, Yu-Ren
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Tsai, Wan-Lin
A technigal with the polydimethylsiloxane (PDMS) solution infiltrated into the SiOx-coated CNTAs has been utilized to directly transfer the CNTAs away from the silicon substrate. The oxide coating layer was utilized to protect the morpholgy of as-grown patterned vertical aligmed carbon nanotube (CNTs) arrays. The high density plasma reactive ions etching (HDP-RIE) system was used to make the CNTs emerge from the surface of the flexible substrate and modify the crystallines of CNTs. After the protecting oxide was HDP-RIE-processed for 8 min, the emission current properties were enhanced to be 1.03 V/mu m and 1.43 V/mu m, respectively, for the turn-on field and the threshold field, as compared with 1.25 V/mu m and 1.59 V/mu m for the as-grown CNTs, accordingly. The Field Emission (FE) enhancement after dry etching could be attributed to the open-ended structures and better crystalline.
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
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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
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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.
Growth and Field Emission Characteristics of Pillar-like Carbon Nanotubes Using Co-Ti/Al Co-deposited Catalysts at Low Temperature
(2010)
Chang, C. T.
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Lee, C. Y.
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Lin, K. C.
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Lai, R. L.
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Tsai, Wan-Lin
In this essay, the pillar-like CNT field emission arrays synthesis with co-deposited catalysts at low temperature (550 degrees C) was proposed. Pillar-like CNT has been successfully synthesized by thermal CVD system. The current density of this proposed pillar like CNTs was as high as 1272 mu A/cm(2) at 6 V/mu m and the turn-on field was 3.6 V/mu m. Additionally, the reliability was more stable as lower than 7% degradation of initial current density.
High-Performance Programmable Metallization Cell Memory With the Pyramid-Structured Electrode
(2013-10-01)
Huang, Yu-Chih
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Tsai, Wan-Lin
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Chou, Chia-Hsin
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Wan, Chung-Yun
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Hsiao, Ching
The pyramid structure fabricated with the potassium hydroxide (KOH) anisotropically etched (100) silicon substrate has been deposited with a copper film as the bottom electrode of the programmable metallization cell (PMC) memory to significantly improve the resistive switching characteristic. As compared with the conventional flat copper electrode, this pyramid-structured electrode exhibited the set/reset voltage as low as 1/0.6 V and superior endurance of 2400 cycles at the set/reset voltages of -5/+3 V for the voltages pulsewidth of 1 mu s. The high performance of this PMC could be attributed to high local electrical fields at the tips of the pyramid structure, resulting in the formation of the narrower conductive filaments that facilitate the lower operation voltage and better endurance.
High-performance resistive switching characteristics of programmable metallization cell with oxidized Cu-Ti electrodes
(2013-09-30)
Huang, Yu-Chih
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Chou, Chia-Hsin
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Liao, Chan-Yu
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Tsai, Wan-Lin
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Cheng, Huang-Chung
Programmable metallization cell (PMC) memory devices with oxidized Cu-Ti alloy films as the bottom electrodes have been shown to exhibit a superior on/off state current ratio (memory window) of as high as 10(3) and endurance of 3000 cycles as compared to conventional pure copper and unoxidized Cu-Ti alloy electrodes. It was conjectured that the Cu-Ti alloy electrodes could obtain the appropriate amount of copper atoms to format and rupture the conductive filaments in the resistive switching layer. Furthermore, the oxidized Cu-Ti alloys could control the Cu cations from the Cu and Cu2O to the appropriate amountto achieve the most favorable PMC characteristics. (C) 2013 AIP Publishing LLC.
High-sensitivity extended-gate field-effect transistors as pH sensors with oxygen-modified reduced graphene oxide films coated on different reverse-pyramid silicon structures as sensing heads
(2016-04)
Li, Yu-Ren
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Chang, Shih-hsueh
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Chang, Chia-Tsung
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Tsai, Wan-Lin
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Chiu, Yu-Kai
A high-performance extended-gate field-effect transistor (EGFET) as pH sensor with its microstructured sensing head composed of an oxygen-modified reduced graphene oxide film (RGOF) on a reverse-pyramid (RP) Si structure was developed to achieve a high sensitivity of 57.5mV/pH with an excellent linearity of 0.9929 in a wide pH sensing range of 1-13. These features were ascribed to the large amount of sensing sites and large sensing area. In contrast, the planar Si substrate with the oxygen-plasma-treated RGOF (OPT-RGOF) at the optimal bias power showed a sensitivity of 52.9mV/pH compared with 45.0mV/pH for that without plasma treatment. It reveals that oxygen plasma can produce oxygen-containing groups as sensing sites, enhancing proton sensing characteristics. However, oxygen plasma treatment at high bias powers would cause damage to the RGOFs, resulting in poor conducting and sensing properties. On the other hand, the use of the RP structures could increase the effective sensing area and further promote the sensing performance. (C) 2016 The Japan Society of Applied Physics
High-sensitivity extended-gate field-effect transistors as pH sensors with oxygen-modified reduced graphene oxide films coated on different reverse-pyramid silicon structures as sensing heads
(2016-04-01)
Li, Yu-Ren
;
Chang, Shih-hsueh
;
Chang, Chia-Tsung
;
Tsai, Wan-Lin
;
Chiu, Yu-Kai
A high-performance extended-gate field-effect transistor (EGFET) as pH sensor with its microstructured sensing head composed of an oxygen-modified reduced graphene oxide film (RGOF) on a reverse-pyramid (RP) Si structure was developed to achieve a high sensitivity of 57.5mV/pH with an excellent linearity of 0.9929 in a wide pH sensing range of 1-13. These features were ascribed to the large amount of sensing sites and large sensing area. In contrast, the planar Si substrate with the oxygen-plasma-treated RGOF (OPT-RGOF) at the optimal bias power showed a sensitivity of 52.9mV/pH compared with 45.0mV/pH for that without plasma treatment. It reveals that oxygen plasma can produce oxygen-containing groups as sensing sites, enhancing proton sensing characteristics. However, oxygen plasma treatment at high bias powers would cause damage to the RGOFs, resulting in poor conducting and sensing properties. On the other hand, the use of the RP structures could increase the effective sensing area and further promote the sensing performance. (C) 2016 The Japan Society of Applied Physics
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
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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.
Improved Field Emission Characteristics with different Electrode Materials by forming process in a Quasi-planar Thin Film Field Emission Diode
(2010-01-01)
Chang, C. T.
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Hsu, Y. Y.
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Lin, K. C.
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Tsai, Wan-Lin
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Chien, Yun-Shan
The essay was reported the different electrode materials in a quasi-planar thin film field emission diode by different forming process. The forming process causes an increased surface roughness of emitters or reduced the work function of the emitter and results in a higher field enhancement factor, which shows better field emission characteristics. The turn on voltage could from 15 V to 8 V and 6.5V with Co and Pd electrode at the emission current of 100 nA for samples.
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.
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
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Huang, Bai-Tao
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Yang, Po-Yu
;
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.
Sensitivity Enhancement of Ultraviolet Photodetectors With the Structure of p-NiO/Insulator-SiO2/n-ZnO Nanowires
(2015-08-01)
Li, Yu-Ren
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Wan, Chung-Yun
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Chang, Chia-Tsung
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Huang, Yu-Chih
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Tsai, Wan-Lin
A high-performance photodetector with the structure of NiO/SiO2/ZnO nanowires has been proposed. The devices with 6-nm-thick SiO2 exhibited a better rectification ratio (J(forward)/J(reverse)) of 246 at +/- 2 V, lower dark current density (J(dark)) of 3.5 x 10(-7) A/cm(2) at a reverse bias of 2 V, and superior ultraviolet (UV) sensitivity (I-UV/I-dark) of 16.23 than those without the SiO2 layer (J(forward)/J(reverse) = 44, Jdark = 4.7x10(-6) A/cm(2), and I-UV/I-dark = 5.5). The improved performance was mainly due to the ultrathin inserted SiO2 layer that builds a barrier height to minimize the transmission probability of low-energy carriers, leading to the enhancement of the UV sensing characteristics.
The mechanism of the surface morphology transformation for the carbon nanotube thin film irradiated via excimer laser
(2013-05-06)
Chien, Yun-Shan
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Lee, I-Che
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Yang, Po-Yu
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Wang, Chao-Lung
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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.
The pH Sensing Characteristics of the Extended-Gate Field-Effect Transistors of Multi-Walled Carbon-Nanotube Thin Film Using Low-Temperature Ultrasonic Spray Method
(2012-07-01)
Chien, Yun-Shan
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Yang, Po-Yu
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Tsai, Wan-Lin
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Li, Yu-Ren
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Chou, Chia-Hsin
A novel, simple and low-temperature ultrasonic spray method was developed to fabricate the multi-walled carbon-nanotubes (MWCNTs) based extended-gate field-effect transistors (EGFETs) as the pH sensor. With an acid-treated process, the chemically functionalized two-dimensional MWCNT network could provide plenty of functional groups which exhibit hydrophilic property and serve as hydrogen sensing sites. For the first time, the EGFET using a MWCNT structure could achieve a wide sensing rage from pH = 1 to pH = 13. Furthermore, the pH sensitivity and linearity values of the CNT pH-EGFET devices were enhanced to 51.74 mV/pH and 0.9948 from pH = 1 to pH = 13 while the sprayed deposition reached 50 times. The sensing properties of hydrogen and hydroxyl ions show significantly dependent on the sprayed deposition times, morphologies, crystalline and chemical bonding of acid-treated MWCNT. These results demonstrate that the MWCNT-EGFETs are very promising for the applications in the pH and biomedical sensors.
Thickness effect of NiO on the performance of ultraviolet sensors with p-NiO/n-ZnO nanowire heterojunction structure
(2015-08-01)
Li, Yu-Ren
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Wan, Chung-Yun
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Chang, Chia-Tsung
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Tsai, Wan-Lin
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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.