Browsing by Author "Chen, Wei-Chun"

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Advanced Functional Nanomaterials Synthesis and Nanocrystal Growth Technology
(2015-01-01)
Chen, Wei-Chun
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Kuo, Hao-Chung
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Tiwari, Rajanish Nath
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Kuo, Shou-Yi
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Lai, Fang-I
Diamond plates on dome-like particles: preparation, characterization and field emission properties
(2010-08-01)
Tiwari, Rajanish N.
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Chen, Wei-Chun
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Tiwari, Jitendra N.
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Wang, Wei-Lin
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Chang, Li
Thin diamond microplates have been grown on dome-like/hemispherical carbon particles on titanium carbide by a microwave plasma chemical vapour deposition (MPCVD) method using a gas mixture of methane and hydrogen. The diamond microplates have a thickness of about 200 nm. A thin (300 nm) film of titanium carbide was formed during carburization of sputtered titanium on an Si(100) substrate in MPCVD. The hemispherical carbon particles were covered with diamond microplates. The diamond microplates are isolated electron-emitting spherules and exhibit a low threshold (50 V mu m (1)) and high current density (0.92 mA cm(-2)) in their field emission properties. A possible mechanism for the formation of the diamond microplates and hemispherical carbon particles is presented.
Effect of In/Al ratios on structural and optical properties of InAlN films grown on Si(100) by RF-MOMBE
(2014-05-01)
Chen, Wei-Chun
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Wu, Yue-Han
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Peng, Chun-Yen
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Hsiao, Chien-Nan
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Chang, Li
InxAl1-xN films were deposited on Si(100) substrate using metal-organic molecular beam epitaxy. We investigated the effect of the trimethylindium/trimethylaluminum (TMIn/TMAI) flow ratios on the structural, morphological, and optical properties of InxAl1-xN films. Surface morphologies and microstructure of the InxAl1-xN films were measured by atomic force microscopy, scanning electron microscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM), respectively. Optical properties of all films were evaluated using an ultraviolet/visible/infrared (UV/Vis/IR) reflection spectrophotometer. XRD and TEM results indicated that InxAl1-xN films were preferentially oriented in the c-axis direction. Besides, the growth rates of InxAl1-xN films were measured at around 0.6 mu m/h in average. Reflection spectrum shows that the optical absorption of the InxAl1-xN films redshifts with an increase in the In composition.
Electric Field Induced Nitride Trapped Charge Lateral Migration in a SONOS Flash Memory
(2017-01)
Liu, Yu-Heng
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Jiang, Cheng-Min
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Chen, Wei-Chun
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Wang, Tahui
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Tsai, Wen-Jer
We investigated electric field-induced trapped electron lateralmigration in a SONOS flash cell. The threshold voltage shift (Delta V-t) andgate-induceddrain leakage(GIDL) current were measured to monitor nitride electron movement in retention. We applied different voltages to the gate and the source/drain in retention to vary the vertical and lateral electric fields. Our study shows that: 1) GIDL current can be used tomonitor trapped charge lateralmigration and 2) nitride charge lateral migration exhibits strong dependence on the lateral electric field. Based on measured temperature and field dependence, a nitride trapped charge emission process via thermally assisted tunneling is proposed for electron lateral migration. The emission rates of thermally assisted tunneling, direct trap-to-band tunneling and Frenkel-Poole emission were compared.
Electric Field Induced Nitride Trapped Charge Lateral Migration in a SONOS Flash Memory
(2017-01)
Liu, Yu-Heng
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Jiang, Cheng-Min
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Chen, Wei-Chun
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Wang, Tahui
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Tsai, Wen-Jer
We investigated electric field-induced trapped electron lateralmigration in a SONOS flash cell. The threshold voltage shift (Delta V-t) andgate-induceddrain leakage(GIDL) current were measured to monitor nitride electron movement in retention. We applied different voltages to the gate and the source/drain in retention to vary the vertical and lateral electric fields. Our study shows that: 1) GIDL current can be used tomonitor trapped charge lateralmigration and 2) nitride charge lateral migration exhibits strong dependence on the lateral electric field. Based on measured temperature and field dependence, a nitride trapped charge emission process via thermally assisted tunneling is proposed for electron lateral migration. The emission rates of thermally assisted tunneling, direct trap-to-band tunneling and Frenkel-Poole emission were compared.
Epitaxial growth of semipolar InN(10(1)over-tilde3) on LaAlO3 substrate: Epitaxial relationship analysis
(2017-05-01)
Chen, Wei-Chun
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Kuo, Shou-Yi
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Tian, Jr. -Sheng
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Wang, Wei-Lin
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Lai, Fang-I
Epitaxial semipolar InN(10 (1) over tilde3) crystals were grown on a LaAlO3(112) substrate using radio frequency plasma-assisted molecular beam epitaxy without any interlayer. The lattice mismatch between InN and LaAlO3 was estimated to be % 7.75% along the [1 (2) over tilde 10](InN) direction and 0.2% along the [(3) over tilde 032](InN) direction. The InN film is epitaxic with the LaAlO3 substrate, with orientation relationships between InN(10 (1) over tilde3) parallel to LaAlO3(112) and [1 (2) over tilde 10](InN) parallel to [11 (1) over tilde](LAO). InN grown on LaAlO3(112) appears (10 (1) over tilde3) plane orientated, with two types of domains. Semipolar InN(10 (1) over tilde3) layers can be grown at 510 degrees C and show X-ray rocking curve FWHMs of 1830 and 1408 arcsec for InN(0002) and InN(10 (1) over tilde3), respectively. However, InN grown at 510 degrees C has the highest peak intensity and the narrowest FWHM of the prepared samples, indicating high-quality crystal growth. (C) 2017 The Japan Society of Applied Physics
Epitaxy of m-plane ZnO on (112) LaAlO(3) substrate
(2009-05-01)
Ho, Yen-Teng
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Wang, Wei-Lin
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Peng, Chun-Yen
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Chen, Wei-Chun
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Liang, Mei-Hui
Heteroepitaxial growth of non-polar in-plane (10 (1) over bar0) ZnO has been demonstrated on (112) LaAlO(3) single crystal substrates using the pulsed laser deposition method. X-ray diffraction, reflection high energy electron diffraction, and cross-sectional transmission electron microscopy with selected-area diffraction, have been used to characterize the structural properties of deposited ZnO films. The epitaxial relationship between ZnO and LAO is shown to be (10 (1) over bar0)(ZnO) parallel to (112)(LAO), (11 (2) over bar0)(ZnO) parallel to ((1) over bar(1) over bar1)(LAO), and [0001](ZnO) parallel to [(1) over bar 10](LAO). (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Epitaxy of m-plane ZnO on (112) LaAlO3 substrate
(2009-05-01)
Ho, Yen-Teng
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Wang, Wei-Lin
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Peng, Chun-Yen
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Chen, Wei-Chun
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Liang, Mei-Hui
Heteroepitaxial growth of non-polar in-plane (10 (1) over bar0) ZnO has been demonstrated on (112) LaAlO3 single crystal substrates using the pulsed laser deposition method. X-ray diffraction, reflection high energy electron diffraction, and cross-sectional transmission electron microscopy with selected-area diffraction, have been used to characterize the structural properties of deposited ZnO films. The epitaxial relationship between ZnO and LAO is shown to be (10 (1) over bar0)(ZnO) parallel to (112)(LAO), (11 (2) over bar0)(ZnO) parallel to ((1) over bar(1) over bar1)(LAO), and [0001](ZnO) parallel to [(1) over bar 10](LAO). (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Growth and characterization of diamond films on TiN/Si(100) by microwave plasma chemical vapor deposition
(2009-02-01)
Chen, Wei-Chun
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Wang, Wei-Lin
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Tiwari, Rajanish N.
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Chang, Li
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材料科學與工程學系
Polycrystalline diamond films were deposited on silicon (100) substrate by microwave plasma chemical vapor disposition (MPCVD) using similar to 300 nm thick < 001 > textured titanium nitride (TiN) films as buffer layer which were prepared by radio-frequency reactive sputtering. The diamond/TiN films were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. The results show that no apparent change can be observed for the < 100 > oriented TiN buffer layers after MPCVD even with a negative bias voltage applied onto the substrates. (C) 2008 Published by Elsevier B.V.
Growth of Semipolar InN(10(1)over-bar3) on LaAlO(3)(112) Substrate
(2011-04-01)
Chen, Wei-Chun
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Tian, Jr-Sheng
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Wang, Wei-Lin
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Ho, Yen-Teng
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Chang, Li
In this study, we report the growth and characterization of semipolar (10 (1) over bar3) InN films grown on LaAlO(3)(112) substrate by metalorganic molecular beam epitaxy. InN films were grown at various substrate temperatures in the range of 465-540 degrees C. Structural and optical properties of semipolar InN were investigated by high resolution X-ray diffraction, scanning electron microscopy, and photoluminescence measurements. The results show that semipolar (10 (1) over bar3) InN layers can be grown at 510 degrees C with the full-width at half maximum of the X-ray rocking curve about 1400 arcsec and electron mobility of 494 cm(2)V(-1)s(-1). (C) 2011 The Japan Society of Applied Physics
Growth of Semipolar InN(10(1)over-bar3) on LaAlO3(112) Substrate
(2011-04-01)
Chen, Wei-Chun
;
Tian, Jr-Sheng
;
Wang, Wei-Lin
;
Ho, Yen-Teng
;
Chang, Li
In this study, we report the growth and characterization of semipolar (10 (1) over bar3) InN films grown on LaAlO3(112) substrate by metalorganic molecular beam epitaxy. InN films were grown at various substrate temperatures in the range of 465-540 degrees C. Structural and optical properties of semipolar InN were investigated by high resolution X-ray diffraction, scanning electron microscopy, and photoluminescence measurements. The results show that semipolar (10 (1) over bar3) InN layers can be grown at 510 degrees C with the full-width at half maximum of the X-ray rocking curve about 1400 arcsec and electron mobility of 494 cm(2)V(-1)s(-1). (C) 2011 The Japan Society of Applied Physics
HCV NS5A Up-Regulates COX-2 Expression via IL-8-Mediated Activation of the ERK/JNK MAPK Pathway
(2015-07-31)
Chen, Wei-Chun
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Tseng, Chin-Kai
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Chen, Yen-Hsu
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Lin, Chun-Kuang
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Hsu, Shihhsien
Chronic hepatitis C virus (HCV) infection leads to intrahepatic inflammation and liver cell injury, which are considered a risk factor for virus-associated hepatitis, cirrhosis, and hepatocellular carcinoma worldwide. Inflammatory cytokines are critical components of the immune system and influence cellular signaling, and genetic imbalances. In this study, we found that cyclooxygenase-2 (COX-2) and interleukin-8 (IL-8) were significantly induced by HCV infection and HCV NS5A expression, and induction of COX-2 correlated with HCV-induced IL-8 production. We also found that the ERK and JNK signaling pathways were involved in the regulation of IL-8-mediated COX-2 induction in response to HCV infection. Using a promoter-linked reporter assay, we identified that the C/EBP regulatory element within the COX-2 promoter was the dominant factor responsible for the induction of COX-2 by HCV. Silencing C/EBP attenuated HCV-induced COX-2 expression. Our results revealed that HCV-induced inflammation promotes viral replication, providing new insights into the involvement of IL-8-mediated COX-2 induction in HCV replication.
Heteroepitaxial growth of InN on GaN intermediate layer by PA-MOMBE
(2011-07-01)
Lai, Fang-I
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Kuo, Shou-Yi
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Chen, Wei-Chun
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Lin, Woei-Tyng
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Wang, Wei-Lin
In this paper, high-quality wurtzite indium nitride was epi-grown on sapphire substrates by plasma-assisted metal-organic molecule beam epitaxy system (PA-MOMBE). Structural and electrical properties of the InN films were significantly improved by employing a GaN buffer layer. In addition, high-resolution X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy (TEM), Hall Effect, Raman and photoluminescence spectroscopy were carried out to characterize the effect of the growth temperature on structural and optoelectronic properties. It was found that highly c-axis oriented InN epilayer can be obtained by optimizing growth conditions. TEM images reveal that the epitaxially grown InN/GaN interface is sharp, and the spacing of the InN(0 0 0 2) lattice plane is about 0.57 nm. Raman spectra also show a sharp peak at 491 cm(-1) attributed to the E(2)(high) mode of wurtzite InN. These results indicate that the improvement of InN material quality can be achieved using heteroepitaxy on GaN/sapphire templates. (C) 2011 Elsevier B.V. All rights reserved.
Heteroepitaxial growth of TiN film on MgO (100) by reactive magnetron sputtering
(2014-10-03)
Chen, Wei-Chun
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Peng, Chun-Yen
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Chang, Li
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材料科學與工程學系
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Department of Materials Science and Engineering
TiN thin films were deposited on MgO (100) substrates at different substrate temperatures using rf sputtering with Ar/N-2 ratio of about 10. At 700 degrees C, the growth rate of TiN was approximately 0.05 mu m/h. The structural and electrical properties of TiN thin films were characterized with x-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Hall measurements. For all deposition conditions, XRD results show that the TiN films can be in an epitaxy with MgO with cube-on-cube orientation relationship of (001)(TiN) // (001)(MgO) and [100](TiN) // [100](MgO). TEM with selected-area electron diffraction pattern verifies the epitaxial growth of the TiN films on MgO. SEM and AFM show that the surface of the TiN film is very smooth with roughness approximately 0.26 nm. The minimum resistivity of the films can be as low as 45 mu Omega cm.
Human heme oxygenase 1 is a potential host cell factor against dengue virus replication
(2016-08-24)
Tseng, Chin-Kai
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Lin, Chun-Kuang
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Wu, Yu-Hsuan
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Chen, Yen-Hsu
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Chen, Wei-Chun
Dengue virus (DENV) infection and replication induces oxidative stress, which further contributes to the progression and pathogenesis of the DENV infection. Modulation of host antioxidant molecules may be a useful strategy for interfering with DENV replication. In this study, we showed that induction or exogenous overexpression of heme oxygenase-1 (HO-1), an antioxidant enzyme, effectively inhibited DENV replication in DENV-infected Huh-7 cells. This antiviral effect of HO-1 was attenuated by its inhibitor tin protoporphyrin (SnPP), suggesting that HO-1 was an important cellular factor against DENV replication. Biliverdin but not carbon monoxide and ferrous ions, which are products of the HO-1 on heme, mediated the HO-1-induced anti-DENV effect by non-competitively inhibiting DENV protease, with an inhibition constant (Ki) of 8.55 +/- 0.38 mu M. Moreover, HO-1 induction or its exogenous overexpression, rescued DENV-suppressed antiviral interferon response. Moreover, we showed that HO-1 induction by cobalt protoporphyrin (CoPP) and andrographolide, a natural product, as evidenced by a significant delay in the onset of disease and mortality, and virus load in the infected mice's brains. These findings clearly revealed that a drug or therapy that induced the HO-1 signal pathway was a promising strategy for treating DENV infection.
Indium-rich InAlN films on GaN/sapphire by molecular beam epitaxy
(2014-03)
Wu, Yue-Han
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Wong, Yuen-Yee
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Chen, Wei-Chun
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Tsai, Dung-Sheng
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Peng, Chun-Yen
Here, we report the results of characterization of indium (In)-rich InAlN films on GaN/Sapphire (0001) substrates grown by molecular beam epitaxy. The highquality similar to 123 nm thick InAlN films with 85% In content without phase separation were assessed with x-ray diffraction and transmission electron microscopy (TEM) with x-ray energy dispersive spectroscopy. High-resolution TEM analysis reveals the relaxation at InAlN/GaN interface with misfit dislocations of 1.59 nm spacing. Finally, optical and electrical properties of the InAlN films are presented from absorption spectroscopy and Hall measurements.
Influence of V/III Flow Ratio on Growth of InN on GaN by PA-MOMBE
(2013)
Chen, Wei-Chun
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Tian, Jr-Sheng
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Wu, Yue-Han
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Wang, Wei-Lin
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Kuo, Shou-Yi
InN epilayers were prepared on c-GaN/sapphire substrates by plasma-assisted metal-organic molecular beam epitaxy using N-2 and trimethylindium precursor as the V/III sources. We studied the influence of the V/III flow ratio on the film structure, surface morphology, film compositions, and optical and electrical properties using scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray diffraction, X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), photoluminescence (PL) measurement and Hall effect. The results show that epitaxial InN films can be obtained with the V/III ratio in the range between 1.81 and 4 at 500 degrees C. The InN growth rate decreases from 1.9 to 1.4 mu m/h when the ratio increases from 1.81 to 4. The surfaces of the InN films are not smooth in the V/III range used. Cross-sectional TEM revealed that the planar defect density in InN is as high as similar to 1.5 x 10(6) cm(-1) at a V/III ratio of similar to 1.81. XPS and SIMS results show that the film surface contains oxygen, which is found to affect the measured carrier mobility and concentration. (C) 2013 The Electrochemical Society. All rights reserved.
Lucidone suppresses dengue viral replication through the induction of heme oxygenase-1
(2018-01-01)
Chen, Wei-Chun
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Tseng, Chin-Kai
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Lin, Chun-Kuang
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Wang, Shen-Nien
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Wang, Wen-Hung
Dengue virus (DENV) infection causes life-threatening diseases such as dengue hemorrhagic fever and dengue shock syndrome. Currently, there is no effective therapeutic agent or vaccine against DENV infection; hence, there is an urgent need to discover anti-DENV agents. The potential therapeutic efficacy of lucidone was first evaluated in vivo using a DENV-infected Institute of Cancer Research (ICR) suckling mouse model by monitoring body weight, clinical score, survival rate, and viral titer. We found that lucidone effectively protected mice from DENV infection by sustaining survival rate and reducing viral titers in DENV-infected ICR suckling mice. Then, the anti-DENV activity of lucidone was confirmed by western blotting and quantitative-reverse-transcription-polymerase chain reaction analysis, with an EC50 value of 25 +/- 3 mu M. Lucidone significantly induced heme oxygenase-1 (HO-1) production against DENV replication by inhibiting DENV NS2B/3 protease activity to induce the DENV-suppressed antiviral interferon response. The inhibitory effect of lucidone on DENV replication was attenuated by silencing of HO-1 gene expression or blocking HO-1 activity. In addition, lucidone-stimulated nuclear factor erythroid 2-related factor 2 (Nrf2), which is involved in transactivation of HO-1 expression for its anti-DENV activity. Taken together, the mechanistic investigations revealed that lucidone exhibits significant anti-DENV activity in in vivo and in vitro by inducing Nrf2-mediated HO-1 expression, leading to blockage of viral protease activity to induce the anti-viral interferon (IFN) response. These results suggest that lucidone is a promising candidate for drug development.
Reactive Sputtering Deposition of Epitaxial TiC Film on Si (100) Substrate
(2020-07-01)
Fang, Yu-Siang
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Thi Hien Do
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Chiu, Kun-An
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Chen, Wei-Chun
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Chang, Li
Epitaxial (100) TiC film deposition on Si (100) substrate by direct current magnetron reactive sputtering of a metallic Ti target with 3%-6% CH4 in Ar gas was investigated. X-ray diffraction and cross-sectional scanning transmission electron microscopy (STEM) reveal that epitaxial cubic TiC can be grown on the Si substrate by domain matching epitaxy in 5/4 ratio with the epitaxial relationship of TiC (100)[0 (1) over bar1] // Si (100)[0 (1) over bar 1]. For sputtering with 3% and 4% CH4, the deposited films are found to consist of both TiC and metallic Ti phases. Increasing the CH4 flow ratio to 5% results in a deposited film completely consisting of TiC without metallic Ti phase. The crystallinity of the deposited TiC is also improved with increasing the CH4 ratio to 5%. X-ray photoelectron spectroscopy shows that the [C]/[Ti] atomic ratio in TiC is nearly close to 1 for growth with 5% CH4 flow ratio and above. The measured electrical resistivities of the deposited films also increase from 41 to 153 mu omega center dot cm with increasing the CH4 ratio from 3% to 6%. With film growth beyond 50 nm thickness, it is shown that some disoriented TiC grains are formed.
Realizing omnidirectional light harvesting by employing hierarchical architecture for dye sensitized solar cells
(2016)
Hsieh, Ming-Yang
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Lai, Fang-I
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Chen, Wei-Chun
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Hsieh, Min-Chi
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Hu, Hsiang-Yi
To improve the omnidirectional light-harvesting in dye-sensitized solar cells (DSSCs), here we present a dandelion-like structure composed of ZnO hemispherical shells and nanorods. Uniformly distributed hemispherical shells effectively suppress the reflection over the broadband region at incident angles up to 60 degrees, greatly improving the optical absorption of the DSSCs. In addition, modulating the length of the ZnO nanorods controls the omnidirectional characteristics of DSSCs. This phenomenon is attributed to the degree of periodicity of the ZnO dandelion-like structures. Cells with shorter rods exhibit a high degree of periodicity, thus the conversion efficiencies of the cells show specific angle-independent features. On the other hand, the cells with longer lengths reveal angle-dependent photovoltaic performance. Along with the simulation, the cells with dandelion-like ZnO structures can couple incident photons efficiently to achieve excellent broadband and omnidirectional light-harvesting performances experimentally, and the DSSCs enhanced the conversion efficiency by 48% at large incident angles. All these findings not only provide further insight into the light-trapping mechanism in these complex three-dimensional nanostructures but also offer efficient omnidirectional and broadband nanostructured photovoltaics for advanced applications.