Browsing by Author "Chen, Yu-Chun"

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A Wearable Channel Selection-Based Brain-Computer Interface for Motor Imagery Detection
(2016-02-01)
Lo, Chi-Chun
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Chien, Tsung-Yi
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Chen, Yu-Chun
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Tsai, Shang-Ho
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Fang, Wai-Chi
Motor imagery-based brain-computer interface (BCI) is a communication interface between an external machine and the brain. Many kinds of spatial filters are used in BCIs to enhance the electroencephalography (EEG) features related to motor imagery. The approach of channel selection, developed to reserve meaningful EEG channels, is also an important technique for the development of BCIs. However, current BCI systems require a conventional EEG machine and EEG electrodes with conductive gel to acquire multi-channel EEG signals and then transmit these EEG signals to the back-end computer to perform the approach of channel selection. This reduces the convenience of use in daily life and increases the limitations of BCI applications. In order to improve the above issues, a novel wearable channel selection-based brain-computer interface is proposed. Here, retractable comb-shaped active dry electrodes are designed to measure the EEG signals on a hairy site, without conductive gel. By the design of analog CAR spatial filters and the firmware of EEG acquisition module, the function of spatial filters could be performed without any calculation, and channel selection could be performed in the front-end device to improve the practicability of detecting motor imagery in the wearable EEG device directly or in commercial mobile phones or tablets, which may have relatively low system specifications. Finally, the performance of the proposed BCI is investigated, and the experimental results show that the proposed system is a good wearable BCI system prototype.
Analysis of Anomalous Capacitance Induced by TAGIDL in p-Channel LTPS TFTs
(2010)
Lin, Chia-Sheng
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Chen, Ying-Chung
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Chang, Ting-Chang
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Li, Hung-Wei
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Chen, Shih-Ching
In this work, a mechanism of anomalous capacitance in p-channel low temperature polycrystalline silicon thin film transistors (LTPS TFTs) was investigated. In general, the effective capacitance of the LTPS TFTs was only dependent with the overlap area between the gate and source/drain under the off-state. However, the experimental results reveal that the off-state capacitance was increased with decreasing measurement frequency and/or with increasing measurement temperature. By fitting the curve of the drain current vs electric field under off-state region, it was verified that the trap-assisted gate-induced drain leakage (TAGIDL) consists of the Pool-Frenkel emission and thermal field emission. In addition, the charge density calculated from the C(gsd)-V(g) measurement also has the same dependence with electric field. This result demonstrates that the anomalous capacitance is mainly due to the TAGIDL. To suppress the anomalous capacitance, a band-to-band hot electron stress was utilized to reduce the vertical electric field between the gate and the drain. The electric field simulation was also performed by TCAD software. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3483759] All rights reserved.
Analysis of Electrical Characteristics and Reliability Change of Zinc-Tin-Oxide Thin-Film Transistors by Photo-Thermal Treatment
(2013)
Chen, Yu-Chun
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Chang, Ting-Chang
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Li, Hung-Wei
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Chung, Wan-Fang
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Hsieh, Tien-Yu
This study investigates the influence of a photo-thermal treatment on the electrical characteristics and bias-induced instability of amorphous Zn-Sn-O thin film transistors. Sequences of measurements made in both vacuum and oxygen ambient reveal the most pronounced threshold voltage (V-T) shift, i.e., the highest sensitivity of oxygen, occurs in a device with photo-thermal-treatment. After gate-bias stress in vacuum, the treated device shows less V-T shift than that untreated, which can be attributed to residual adsorbed gas molecules on the backchannel. Thus, the proposed photo-thermal-treatment should be conducted before depositing a passivation layer to increase the reliability of devices after stress. (c) 2013 The Electrochemical Society. All rights reserved.
Bias-induced oxygen adsorption in zinc tin oxide thin film transistors under dynamic stress
(2010-06-28)
Chen, Yu-Chun
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Chang, Ting-Chang
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Li, Hung-Wei
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Chen, Shih-Ching
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Lu, Jin
This study investigates the effects of bias-induced oxygen adsorption on the electrical characteristic instability of zinc tin oxide thin film transistors in different ambient oxygen partial pressures. When oxygen pressure is largest, the threshold voltages showed the quickest increase but the slowest recovery during the stress phase and recovery phase, respectively. This finding corresponds to the charge trapping time constant and recovery time constant, which are extracted by fitting the stretched-exponential equation and which exhibit a relationship with oxygen pressure. We suggest that the gate bias reduces the activation energy of oxygen adsorption during gate bias stress. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3457996]
Characterization of environment-dependent hysteresis in indium gallium zinc oxide thin film transistors
(2013-09-01)
Chen, Yu-Chun
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Chang, Ting-Chang
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Li, Hung-Wei
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Chung, Wan-Fang
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Chen, Shih-Cheng
This study investigates environmentally dependent electrical performance as a function of hysteresis phenomena for amorphous indium-gallium-zinc-oxide (a-IGZO) thin film transistors (TFTs). Because ambient gas has a great influence on the electrical characteristics of zinc oxide-based TFTs during electrical measurements, the hysteresis for current-voltage and capacitance-voltage measurements are employed in different ambient gases (ambient air, vacuum, oxygen ambient and moisture ambient) to study this issue. Although the hysteresis phenomenon has been explained by the charge trapping and de-trapping model, in order to obtain stable electrical characteristics it is necessary to clarify the original principal mechanism leading to threshold voltage instability under gate bias operations in different environments. Also, the relationship between de-trapping rate and electrical hysteresis is investigated by prolonging the integration time of the semiconductor parameter analyzer. This study may be of importance in explaining the dynamic relationship between the TFT electrical characteristics and ambient gas, as well as providing a better understanding of the environment-dependent hysteresis phenomenon of the IGZO TFTs. (C) 2012 Elsevier B.V. All rights reserved.
Dependence of Light-Accelerated Instability on Bias and Environment in Amorphous Indium-Gallium-Zinc-Oxide Thin Film Transistors
(2013)
Chen, Yu-Chun
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Chang, Ting-Chang
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Li, Hung-Wei
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Chung, Wan-Fang
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Hsieh, Tien-Yu
This study examines the dependence of light-accelerated instability on bias and environment in amorphous indium-gallium-zinc-oxide thin film transistors. When device is in vacuum ambient, the threshold voltage of device after negative gate bias illumination stress (NBIS) showed bias-dependent electrical degradation behavior. However, experimental results show the degradation of electrical characteristic in a-IGZO devices does not only rely on the charge trapping mechanism for NBIS. During NBIS in oxygen, moisture-simulated and atmosphere ambient, the negative shift in electrical characteristic is suppressed when compared to that in vacuum. This implies that the adsorbent gas species in the surrounding environment dominates the electrical characteristic degradation of devices during NBIS, which leading the change of dominant mechanism from photon-created carrier trapping to adsorbed/desorbed gas phenomenon. (C) 2013 The Electrochemical Society. All rights reserved.
Dual operation characteristics of resistance random access memory in indium-gallium-zinc-oxide thin film transistors
(2014-04-14)
Yang, Jyun-Bao
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Chang, Ting-Chang
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Huang, Jheng-Jie
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Chen, Yu-Chun
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Chen, Yu-Ting
In this study, indium-gallium-zinc-oxide thin film transistors can be operated either as transistors or resistance random access memory devices. Before the forming process, current-voltage curve transfer characteristics are observed, and resistance switching characteristics are measured after a forming process. These resistance switching characteristics exhibit two behaviors, and are dominated by different mechanisms. The mode 1 resistance switching behavior is due to oxygen vacancies, while mode 2 is dominated by the formation of an oxygen-rich layer. Furthermore, an easy approach is proposed to reduce power consumption when using these resistance random access memory devices with the amorphous indium-gallium-zinc-oxide thin film transistor. (C) 2014 AIP Publishing LLC.
Environment-dependent thermal instability of sol-gel derived amorphous indium-gallium-zinc-oxide thin film transistors
(2011-04-11)
Chung, Wan-Fang
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Chang, Ting-Chang
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Li, Hung-Wei
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Chen, Shih-Ching
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Chen, Yu-Chun
The environment-dependent electrical performances as a function of temperature for sol-gel derived amorphous indium-gallium-zinc-oxide (a-IGZO) thin film transistors are investigated in this letter. In the ambients without oxygen, thermal activation dominates and enhances device performance. In oxygen-containing environments, mobility and drain current degrades and the threshold slightly increase as temperature increases. We develop a porous model for a-IGZO film relating to the drain current and mobility lowering due to film porosity and oxygen adsorption/penetration. It also relates to the threshold voltage recovery at high temperature owing to the varying form of adsorbed oxygen and the combination of oxygen and vacancies. (C) 2011 American Institute of Physics. [doi:10.1063/1.3580614]
Examination of the temporal effect in a flow injection analysis system using multi-channel absorbance detection
(2009-05-22)
Lin, Shu-Hui
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Chang, Kai-Chieh
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Chen, Yu-Chun
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Yu, Tiing
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Pai, Su-Cheng
In addition to the Poiseuille effect, a so-called temporal effect was proposed recently to elucidate the commonly observed tailing peak signals of flow injection analysis (FIA). A multi-channel absorbance detector was used in this study to obtain the FIA peaks on both the spatial and temporal coordinates. The temporal effect was analyzed by comparison of the profiles between the experimental and the corresponding Gaussian peaks. and by comparison of asymmetry factors between the spatial and the temporal peaks. The temporal effect appeared to be the major factor under flow rates ranging from 0.5 to 8 ml min(-1). This was despite the presence of a spatially frontal peak observed in the FIA tubing, which was found to result in a tailing peak on the temporal coordinate due to this discussed cause. in addition, the temporal effect became greater as the flow rate increased. (C) 2009 Published by Elsevier B.V.
Exposure to Mono-n-Butyl Phthalate in Women with Endometriosis and Its Association with the Biological Effects on Human Granulosa Cells
(2020-03-01)
Chou, Ya-Ching
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Chen, Yu-Chun
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Chen, Ming-Jer
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Chang, Ching-Wen
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Lai, Guan-Lin
To study the association between urinary phthalate metabolite levels, endometriosis, and their effects on human granulosa cells, we recruited patients who underwent laparoscopy to confirm endometriosis (n = 123) and control patients (n = 78). Liquid chromatography-tandem mass spectrometry was used to measure the following five urinary phthalate metabolites: mono-n-butyl phthalate (MnBP), mono(2-ethylhexyl) phthalate, monobenzyl phthalate, mono(2-ethyl-5-oxo-hexyl) phthalate, and mono(2-ethyl-5-hydroxyhexyl) phthalate. Urinary MnBP levels were higher in patients with endometriosis than in controls after multivariable logistic regression including the number of deliveries, body mass index, and use of medicine as covariables. MnBP correlates with other phthalate metabolites. Previous studies found that endometriosis was a detrimental condition for granulosa cells. In our study, we observed whether MnBP affected granulosa cells. MnBP treatment altered the gene expression of BIRC5, BUB1B, CDC20, cyclin B1, IL-1 beta, TNF-alpha, inhibin-B, StAR, and P450ssc and attenuated the ratio of the mitochondrial membrane potential in human granulosa cells. Moreover, MnBP decreased the expression of the anti-Mullerian hormone. These findings suggest that MnBP concentration is associated with endometriosis and may affect the health and steroidogenesis of human granulosa cells.
H(2)O-Assisted O(2) Adsorption in Sol-Gel Derived Amorphous Indium Gallium Zinc Oxide Thin Film Transistors
(2011-01-01)
Chung, Wan-Fang
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Chang, Ting-Chang
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Li, Hung-Wei
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Chen, Shih-Ching
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Chen, Yu-Chun
This paper investigates the environmental effects and related adsorbent species reactions on sol-gel derived amorphous indium gallium zinc oxide thin film transistors (a-IGZO TFTs). The discrepancy between device characteristics measured in atmospheric and vacuum conditions was clarified through experiments with thermal annealing and different gas partial pressures. The measurement of a-IGZO TFTs in simulated water vapor environment was also utilized. We verified that the adsorbed water originating from the surrounding atmosphere can cause an increase in off-current and also enhance more oxygen molecule adsorption on the exposed back-channel surface, leading to more serious degradation in on-current. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3568831] All rights reserved.
H2O-Assisted O-2 Adsorption in Sol-Gel Derived Amorphous Indium Gallium Zinc Oxide Thin Film Transistors
(2011-01-01)
Chung, Wan-Fang
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Chang, Ting-Chang
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Li, Hung-Wei
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Chen, Shih-Ching
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Chen, Yu-Chun
This paper investigates the environmental effects and related adsorbent species reactions on sol-gel derived amorphous indium gallium zinc oxide thin film transistors (a-IGZO TFTs). The discrepancy between device characteristics measured in atmospheric and vacuum conditions was clarified through experiments with thermal annealing and different gas partial pressures. The measurement of a-IGZO TFTs in simulated water vapor environment was also utilized. We verified that the adsorbed water originating from the surrounding atmosphere can cause an increase in off-current and also enhance more oxygen molecule adsorption on the exposed back-channel surface, leading to more serious degradation in on-current. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3568831] All rights reserved.
High-stability oxygen sensor based on amorphous zinc tin oxide thin film transistor
(2012-06-25)
Chen, Yu-Chun
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Chang, Ting-Chang
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Li, Hung-Wei
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Chung, Wan-Fang
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Wu, Chang-Pei
This research presents a sol-gel derived zinc tin oxide thin film transistor (TFT) as a high-stability oxygen sensor. Due to its high sensitivity, oxygen has been traditionally regarded as having a negative influence on the electrical characteristics of zinc-based TFTs; however, TFTs can also act as an oxygen sensor. After illumination with visible light in oxygen-rich ambient, a significant increase in drain current of nearly 10 4 times occurs with fixed gate and drain voltages. It is expected that an optimized method of illumination can help to reset the electrical characteristics or distinguish the on/off state of this reliable oxygen sensor. (C) 2012 American Institute of Physics. [ http://dx.doi.org/10.1063/1.4731773]
Improvement in the bias stability of amorphous InGaZnO TFTs using an Al2O3 passivation layer
(2013-09-01)
Huang, Sheng-Yao
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Chang, Ting-Chang
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Chen, Min-Chen
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Chen, Te-Chih
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Jian, Fu-Yen
This work presents the light-color-dependent negative bias stress (NBIS) effect on amorphous indium gallium zinc oxide (a-IGZO) thin film transistors (TFTs) with Al2O3 passivation layer. The colors of incident photon are varied from red to blue, that incident photon energies are all lower than the optical band gap of IGZO (3.2 eV). The experimental results show that the Al2O3 passivated devices present stable electrical behaviors under different incident lights (Delta V-T<0.1 V of dark and red, Delta V-T<1 V of green, and Delta V-T<4 V of blue), whereas the unpassivation devices exhibit observable negative shifts during NBIS (Delta V-T<1 V of dark and red, Delta V-T>8 V of green, and Delta V-T>15 V of blue). The degradation mechanism of the negative bias stress under illumination of a-IGZO TFTs is dominated by the photo-generated hole trapping at the gate insulator and/or interface between insulator and channel. In this result, the Al2O3 passivation layer can effectively passivate the defect in the a-IGZO film, reducing electron hole pair generated during the illumination processed. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.
Influence of H(2)O Dipole on Subthreshold Swing of Amorphous Indium-Gallium-Zinc-Oxide Thin Film Transistors
(2011-01-01)
Chung, Wan-Fang
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Chang, Ting-Chang
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Li, Hung-Wei
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Chen, Chi-Wen
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Chen, Yu-Chun
The original influence of water on the back-channel of sol-gel derived amorphous indium-gallium-zinc-oxide thin film transistors was studied in various relative humidity environments. As humidity increased from 0 to 80%, the mobility increased from 0.22 to 0.24 cm(2)/(V s), threshold voltage decreased from 6.6 to 4.4 V, and subthreshold swing changed from 0.77 to 1.27 V/dec. The conflicting phenomenon among the three parameters was suggested to be due to a division of the gate voltage by the water molecules which adsorbed on the thin film transistor back-channel and acted as dipoles. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3526097] All rights reserved.
Influence of H2O Dipole on Subthreshold Swing of Amorphous Indium-Gallium-Zinc-Oxide Thin Film Transistors
(2011-01-01)
Chung, Wan-Fang
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Chang, Ting-Chang
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Li, Hung-Wei
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Chen, Chi-Wen
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Chen, Yu-Chun
The original influence of water on the back-channel of sol-gel derived amorphous indium-gallium-zinc-oxide thin film transistors was studied in various relative humidity environments. As humidity increased from 0 to 80%, the mobility increased from 0.22 to 0.24 cm(2)/(V s), threshold voltage decreased from 6.6 to 4.4 V, and subthreshold swing changed from 0.77 to 1.27 V/dec. The conflicting phenomenon among the three parameters was suggested to be due to a division of the gate voltage by the water molecules which adsorbed on the thin film transistor back-channel and acted as dipoles. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3526097] All rights reserved.
Instantaneous normal mode analysis for intermolecular and intramolecular vibrations of water from atomic point of view
(2013-11-28)
Chen, Yu-Chun
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Tang, Ping-Han
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Wu, Ten-Ming
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物理研究所
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Institute of Physics
By exploiting the instantaneous normal mode (INM) analysis for models of flexible molecules, we investigate intermolecular and intramolecular vibrations of water from the atomic point of view. With two flexible SPC/E models, our investigations include three aspects about their INM spectra, which are separated into the unstable, intermolecular, bending, and stretching bands. First, the O- and H-atom contributions in the four INM bands are calculated and their stable INM spectra are compared with the power spectra of the atomic velocity autocorrelation functions. The unstable and intermolecular bands of the flexible models are also compared with those of the SPC/E model of rigid molecules. Second, we formulate the inverse participation ratio (IPR) of the INMs, respectively, for the O- and H-atom and molecule. With the IPRs, the numbers of the three species participated in the INMs are estimated so that the localization characters of the INMs in each band are studied. Further, by the ratio of the IPR of the H atom to that of the O atom, we explore the number of involved OH bond per molecule participated in the INMs. Third, by classifying simulated molecules into subensembles according to the geometry of their local environments or their H-bond configurations, we examine the local-structure effects on the bending and stretching INM bands. All of our results are verified to be insensible to the definition of H-bond. Our conclusions about the intermolecular and intramolecular vibrations in water are given. (C) 2013 AIP Publishing LLC.
Nitrogen Plasma-Assisted Codoped P-type (In, N):SnO(2) Ultra-Fine Thin Films and N-ZnO/p-In:SnO(2) Core-Shell Heterojunction Diodes Fabricated by an Ultrasonic Spray Pyrolysis Method
(2011-11-24)
Chantarat, N.
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Chen, Yu-Wei
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Lin, Chin-Ching
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Chiang, Mei-Ching
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Chen, Yu-Chun
In this study, tin oxide (SnO(2)) solution mixtures containing indium (In) of 0%, 3%, 7%, 15%, and 30% were used to fabricate In- and N-codoped SnO(2) films on glass at 400 degrees C using an ultrasonic spray pyrolysis method combined with thermal annealing at 600 degrees C and post nitrogen plasma treatment. X-ray diffraction analysis demonstrated that the incorporation of elemental In in the SnO(2) film primarily induces the evolution of crystalline phases from In-doped SnO(2) to Sn-doped In(2)O(3), depending on the doping concentration. Upon exposure to N plasma, the dark current dramatically increases in proportion to the treatment duration (5-40 min); the dark current can be enhanced for the 3% and 7%-doped samples by as much as 3 orders of magnitude compared to the untreated samples. Hall measurements confirmed that hole carriers could dominate the SnO(2) host matrix to promote p-type properties at a low In content (3% and 7%) with an increase in resistance compared to undoped samples. However, samples with higher In content (15% and 30%) showed the opposite trend, due to the formation of a secondary phase of n-type In(2)O(3). X-ray photoelectron spectroscopy was used to probe the incorporation and dissociation of chemical bonds between the doped In and N atoms in the SnO(2). Moreover, depth profile measurements showed a correlation between the elemental compositions and elemental distributions of the codoped SnO(2) film. Current-voltage (I-V) characterization revealed the improved behavior of heterojunction diodes consisting of a p-type (In, N)-doped SnO(2) thin film deposited on n-type ZnO nanorod arrays.
Nitrogen Plasma-Assisted Codoped P-type (In, N):SnO2 Ultra-Fine Thin Films and N-ZnO/p-In:SnO2 Core-Shell Heterojunction Diodes Fabricated by an Ultrasonic Spray Pyrolysis Method
(2011-11-24)
Chantarat, N.
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Chen, Yu-Wei
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Lin, Chin-Ching
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Chiang, Mei-Ching
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Chen, Yu-Chun
In this study, tin oxide (SnO2) solution mixtures containing indium (In) of 0%, 3%, 7%, 15%, and 30% were used to fabricate In- and N-codoped SnO2 films on glass at 400 degrees C using an ultrasonic spray pyrolysis method combined with thermal annealing at 600 degrees C and post nitrogen plasma treatment. X-ray diffraction analysis demonstrated that the incorporation of elemental In in the SnO2 film primarily induces the evolution of crystalline phases from In-doped SnO2 to Sn-doped In2O3, depending on the doping concentration. Upon exposure to N plasma, the dark current dramatically increases in proportion to the treatment duration (5-40 min); the dark current can be enhanced for the 3% and 7%-doped samples by as much as 3 orders of magnitude compared to the untreated samples. Hall measurements confirmed that hole carriers could dominate the SnO2 host matrix to promote p-type properties at a low In content (3% and 7%) with an increase in resistance compared to undoped samples. However, samples with higher In content (15% and 30%) showed the opposite trend, due to the formation of a secondary phase of n-type In2O3. X-ray photoelectron spectroscopy was used to probe the incorporation and dissociation of chemical bonds between the doped In and N atoms in the SnO2. Moreover, depth profile measurements showed a correlation between the elemental compositions and elemental distributions of the codoped SnO2 film. Current-voltage (I-V) characterization revealed the improved behavior of heterojunction diodes consisting of a p-type (In, N)-doped SnO2 thin film deposited on n-type ZnO nanorod arrays.
Novel Noncontact Dry Electrode With Adaptive Mechanical Design for Measuring EEG in a Hairy Site
(2015-12-01)
Chen, Yu-Chun
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Lin, Bor-Shyh
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Pan, Jeng-Shyang
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影像與生醫光電研究所
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Institute of Imaging and Biomedical Photonics
Electroencephalography (EEG) can provide important and useful information in clinical diagnosis. The conventional EEG electrode with conductive gel (wet electrode) is most frequently used for measuring EEG. However, the wet electrode encounters the issue of dehydration for long-term measurement. Recently, different types of dry electrodes were proposed to overcome the above issue, but measuring EEG in a hairy site is still a challenge for these electrodes. In this paper, a novel noncontact dry electrode with adaptive mechanical design is proposed to measure EEG in a hairy site without conductive gel. The proposed noncontact dry electrode can measure EEG across the hair layer to reduce the influence of hair. By the adaptive mechanical design, the influence of motion artifact can also be effectively improved. From the experimental results, the proposed noncontact dry electrode can provide a good performance of measuring EEG in a hairy site and a good ability to avoid the influence of motion artifact.