Browsing by Author "Chou, Chia-Hsin"

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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
;
Wan, Chung-Yun
;
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
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 a capping oxide layer on polycrystalline-silicon thin-film transistors fabricated by continuous-wave laser crystallization
(2018-06-01)
Li, Yi-Shao
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Wu, Chun-Yi
;
Chou, Chia-Hsin
;
Liao, Chan-Yu
;
Chuang, Kai-Chi
A tetraethyl-orthosilicate (TEOS) capping oxide was deposited by low-pressure chemical vapor deposition (LPCVD) on a 200-nm-thick amorphous Si (a-Si) film as a heat reservoir to improve the crystallinity and surface roughness of polycrystalline silicon (poly-Si) formed by continuous-wave laser crystallization (CLC). The effects of four thicknesses of the capping oxide layer to satisfy an antireflection condition, namely, 90, 270, 450, and 630 nm, were investigated. The largest poly-Si grain size of 2.5 x 20 mu m(2) could be achieved using a capping oxide layer with an optimal thickness of 450 nm. Moreover, poly-Si nanorod (NR) thin-film transistors (TFTs) fabricated using the aforementioned technique exhibited a superior electron field-effect mobility of 1093.3 cm(2) V-1 s(-1) and an on/off current ratio of 2.53 x 10(9). (c) 2018 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
;
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.
Enhanced efficiency of the dye-sensitized solar cells by excimer laser irradiated carbon nanotube network counter electrode
(2014-02-03)
Chien, Yun-San
;
Yang, Po-Yu
;
Lee, I-Che
;
Chu, Chih-Chieh
;
Chou, Chia-Hsin
The carbon nanotube network decorated with Pt nanoparticles (PtCNT) irradiated by excimer laser as counter electrode (CE) of dye-sensitized solar cells (DSSCs) has been systematically demonstrated. The conversion efficiency would be improved from 7.12% to 9.28% with respect to conventional Pt-film one. It was attributed to the enhanced catalytic surface from Pt nanoparticles and the improved conductivity due to the adjoining phenomenon of PtCNTs irradiated by laser. Moreover, the laser annealing could also promote the interface contact between CE and conductive glass. Therefore, such a simple laser-irradiated PtCNT network is promising for the future flexible DSSCs applications. (C) 2014 AIP Publishing LLC.
Flexible Atmospheric-Pressure Gas Ionization Sensors with Horizontally Aligned Carbon Nanotube Electrodes
(2016-12)
Wang, Kuang-Yu
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Tsai, Wan-Lin
;
Yang, Po-Yu
;
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.
Formation and characterization of high-performance silicon thin-film transistors with and without location-controlled grain boundary
(2017-10-01)
Liao, Chan-Yu
;
Lin, Hsiao-Chun
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Wang, Chao-Lung
;
Lee, I-Che
;
Chou, Chia-Hsin
This paper reports the demonstration of structural effects on excimer laser crystallization (ELC) for the Si strip with a recessed-channel structure on the silicon nitride under-layer (RCS-ULN). We revealed that a single location-controlled grain boundary (GB) oriented normal to the Si strip in the middle site without any other GB in the recessed region can be attained via ELC for the RCS-ULN structures with a short recessed region between neighboring long thick regions in a narrow Si strip. This can be attributed to the effective production of a significant 2D lateral thermal gradient in the recessed region and neighboring thick regions. Consequently, the RCS-ULN TFTs fabricated at the position one-half of such an optimal recessed region can achieve a superior field-effect mobility of 670 cm(2) V-1 . s(-1) with minor performance variations since the single-crystal-like Si channel has been adopted.
High-Performance Germanium Thin-Film Transistors With Single-Crystal-Like Channel via Continuous-Wave Laser Crystallization
(2018-12-01)
Li, Yi-Shao
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Wu, Chun-Yi
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Liao, Chan-Yu
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Huang, Wen-Hsien
;
Shieh, Jia-Min
This letter reports of the fabrication of high-performance p-channel polycrystalline germanium (poly-Ge) thin-film transistors (TFTs) using continuous-wave laser crystallization (CLC). During the CLC process, the direction of crystallization matches the direction of laser scanning due to a strong temperature gradient in the melting region. This makes it possible to fabricate high-quality poly-Ge thin films with 1-D longitudinal grains as large as 2 mu m x 20 mu m. We fabricated the proposed p-channel CLC Ge TFTs with channel width of 0.7 mu m and a channel length each of 0.7 mu m. Consequently, the proposed p-channel CLC Ge TFTs with single-crystal-like channel fabricated on a longitudinal grain with biaxial tensile strain achieved a superior field-effect mobility of 1014.9 cm(2/)V-s.
High-Performance Low-Temperature p-Channel Polycrystalline-Germanium Thin-Film Transistors via Continuous Wave Laser Crystallization
(2016)
Wu, Chun-Vi
;
Li, Yi-Shao
;
Chou, Chia-Hsin
;
Cheng, Huang-Chung
;
電子工程學系及電子研究所
The continuous wave laser crystallization (CLC) has been considered as a suitable approach to achieve the high-quality Ge films. In order to further overcome the hole concentration of Ge thin films resulting from the acceptor-like defects, the counter-doping (CD) process with a suitable dose of n-type dopants was employed to convert the carrier type in Ge thin films. In this study, the high-performance low-temperature p-channel polycrystalline-germanium thin-film transistors (TFTs) have been demonstrated via continuous wave laser crystallization and counter doping to exhibit the low subthreshold swing of 432 mV/decade, a superior on/off current ratio of 4x10(3) and a high hole field-effect mobility of 290 cm(2)/V-s.
High-performance p-channel polycrystalline-germanium thin-film transistors via excimer laser crystallization and counter doping
(2016-04-01)
Liao, Chan-Yu
;
Huang, Ching-Yu
;
Huang, Ming-Hui
;
Chou, Chia-Hsin
;
Cheng, Huang-Chung
High-quality polycrystalline-germanium (poly-Ge) thin films have been successfully fabricated by excimer laser crystallization (ELC). Grains as large as 1 mu m were achieved by ELC at 300 mJ/cm(2). Meanwhile, the defect-generated hole concentrations in Ge thin films were significantly reduced. Furthermore, the majority carriers could then be converted to n-type by counter doping (CD) with a suitable dose. Then, high-performance p-channel Ge thin-film transistors (TFTs) with a high on/off current ratio of up to 1.7 x 10(3) and a high field-effect mobility of up to 208 cm(2) V-1 s(-1) were demonstrated for a channel width and length both of 0.5 mu m. It was revealed that ELC combined with CD is effective for attaining highp-erformance p-channel poly-Ge TFTs. (C) 2016 The Japan Society of Applied Physics
High-performance p-channel polycrystalline-germanium thin-film transistors via excimer laser crystallization and counter doping
(2016-04)
Liao, Chan-Yu
;
Huang, Ching-Yu
;
Huang, Ming-Hui
;
Chou, Chia-Hsin
;
Cheng, Huang-Chung
High-quality polycrystalline-germanium (poly-Ge) thin films have been successfully fabricated by excimer laser crystallization (ELC). Grains as large as 1 mu m were achieved by ELC at 300 mJ/cm(2). Meanwhile, the defect-generated hole concentrations in Ge thin films were significantly reduced. Furthermore, the majority carriers could then be converted to n-type by counter doping (CD) with a suitable dose. Then, high-performance p-channel Ge thin-film transistors (TFTs) with a high on/off current ratio of up to 1.7 x 10(3) and a high field-effect mobility of up to 208 cm(2) V-1 s(-1) were demonstrated for a channel width and length both of 0.5 mu m. It was revealed that ELC combined with CD is effective for attaining highp-erformance p-channel poly-Ge TFTs. (C) 2016 The Japan Society of Applied Physics
High-Performance Polycrystalline-Silicon Nanowire Thin-Film Transistors With Location-Controlled Grain Boundary via Excimer Laser Crystallization
(2012-11-01)
Wang, Chao-Lung
;
Lee, I-Che
;
Wu, Chun-Yu
;
Chou, Chia-Hsin
;
Yang, Po-Yu
High-performance polycrystalline-silicon (poly-Si) nanowire (NW) thin-film transistors (TFTs) are demonstrated using excimer laser crystallization to control the locations of grain boundaries two-dimensionally. Via the locally increased thickness of the amorphous-silicon (a-Si) film as the seeds, the cross-shaped grain boundary structures were produced among these thicker a-Si grids. The NW TFTs with one primary grain boundary perpendicular to the channel direction could be therefore fabricated to achieve an excellent field-effect mobility of 346 cm(2)/V . s and an on/off current ratio of 3 x 10(9). Furthermore, the grain-boundary-location-controlled NW TFTs also exhibited better reliability due to the control of grain boundary locations. This technology is thus promising for applications of low-temperature poly-Si TFTs in system-on-panel and 3-D integrated circuits.
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
;
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
;
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-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).
Location-Controlled Single-Crystal-Like Silicon Thin-Film Transistors by Excimer Laser Crystallization on Recessed-Channel Silicon Strip With Under-Layered Nitride
(2016-09)
Liao, Chan-Yu
;
Lin, Hsiao-Chun
;
Wang, Chao-Lung
;
Lee, I-Che
;
Chou, Chia-Hsin
High-performance Si thin-film transistors (TFTs) on the recessed-channel Si strips with the under-layered nitride film have been fabricated using excimer laser crystallization (ELC). A nitride film was added as a light absorption layer to suppress solidification along the edge of the Si strip. Thus, only one primary grain boundary perpendicular to the Si strip formed in the middle of the recessed region during ELC. The single-crystal-like Si TFTs fabricated on one-half of the recessed region are capable of excellent field-effect mobility of 640 cm(2)/V-s, with only minor deviation.
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
;
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
Planar junctionless poly-Si thin-film transistors with single gate and double gate
(2014-06-01)
Chou, Chia-Hsin
;
Lee, I-Che
;
Lei, Dai-Che
;
Cheng, Huang-Chung
;
電子工程學系及電子研究所
In this letter, single-and double-gate (SG and DG) planar junctionless (JL) thin-film transistors fabricated via a simple process with an in situ-doped active layer is discussed. The DG structure demonstrated a superior subthreshold swing of 160mV/dec and a lower off-current of 1.3 x 10(-13)A than those of 329mV/dec and 2.1 x 10(-12)A for the SG structure, respectively. It contributes to the enhancement of the gate controllability and ultrathin channel. Consequently, the simple fabrication process of the DG JL device is suitable for future application on system-on-panel and three-dimensional integrated circuits. (C) 2014 The Japan Society of Applied Physics