Browsing by Author "Li, SY"

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Characteristics and electrochemical performance of supercapacitors with manganese oxide-carbon nanotube nanocomposite electrodes
(2005)
Lee, CY
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Tsai, HM
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Chuang, HJ
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Li, SY
;
Lin, P
Supercapacitor characteristics of manganese oxide/nickel (MnOx/Ni) and manganese oxide/carbon nanotubes/nickel (MnOx/CNTs/Ni) nanocomposite electrodes were investigated in this study. The CNTs were deposited on the Ni substrate by electrophoresis in a 0.5 mg CNT/1 mL dimethylformamide solution, whereas the MnOx were synthesized by anodic deposition in a 0.16 M manganese sulfate pentahydrate aqueous solution on substrates. The crystallinity and surface morphology of these electrodes were determined by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The capacitive properties of these electrodes were demonstrated by cyclic voltammetry with scan rates ranging from 5 to 100 mV/s. The specific capacitances of the MnOx/CNT/Ni nanocomposite electrode were 415 and 388 F/g with scan rates of 5 and 100 mV/s, respectively. After 1000 cycles of operation, this electrode can maintain 79% of its original capacitance. These MnOx/CNT/Ni nanocomposite electrodes possessing good electrochemical reversibility and high capacitance may be appropriate for supercapacitor application in the future. (c) 2005 The Electrochemical Society.
Copper-catalyzed ZnO nanowires on silicon (100) grown by vapor-liquid-solid process
(2003-01-01)
Li, SY
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Lee, CY
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Tseng, TY
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
The ZnO nanowires were synthesized using vapor liquid-solid (VLS) growth process on copper coated p-type Si (100) Substrate. Copper catalyzed the growth of ZnO nanowires of diameters 80-150 nm and lengths of 2.5-4.0 mum. The ZnO nanowires had hexagonal structure and exhibited <0002> orientation. The photoluminescence measurements showed that the ZnO nanowires had a strong ultraviolet emission at around 381 nm and a very weak green emission around 520 nm. (C) 2002 Elsevier Science B.V. All rights reserved.
Effect of atmosphere on growth of single crystal zinc oxide nanowires
(2004-08-01)
Li, SY
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Lin, P
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Lee, CY
;
Tseng, TY
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材料科學與工程學系
Single crystal zinc oxide (ZnO) nanowires were prepared by using enhanced two-step vapor-liquid-solid (VLS) growth mechanism. The experimental results indicate that the growth rate and morphologies of the nanowires depends on the carrier gas ambient during the thermal reaction process. The ZnO nanowire grown with N-2, not only has the smaller diameter of about similar to 30 nm but also exhibits a higher growth rate and larger number of density of nanowires per unit area than those grown with Ar. The photoluminescence measurements show that the ZnO nanowires grown with N-2 have a stronger ultraviolet emission than those grown with Ar. (C) 2004 Kluwer Academic Publishers.
Effect of phosphorus dopant on photoluminescence and field-emission characteristics of Mg0.1Zn0.9O nanowires
(2006-01-15)
Lee, CY
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Tseng, TY
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Li, SY
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Lin, P
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材料科學與工程學系
The photoluminescence and field-emission properties of Mg0.1Zn0.9O nanowires (MZO NWs) hydrothermally grown on the p-type silicon (100) substrates with and without phosphorus dopant were investigated in this study. Parts of MZO NWs were treated with PH3 plasma to form phosphorus-doped MZO NWs (PMZO NWs). The MZO and PMZO are wurtzite single crystals, and the surface morphologies of MZO NWs are identical to those of PMZO NWs with an average diameter of 50 nm and a length of 500 nm. The direct band gaps and emitted ultraviolet photoluminescences of the MZO and PMZO NWs are 3.41 eV and 403.8 nm and 3.56 eV and 385.4 nm, respectively. The MZO NWs grown on Si substrates have an emission threshold electric field of 1.8 V/mu m (current density of 1.0 mA/cm(2)) and a field enhancement factor, beta, of 3048 while the PMZO NWs show enhanced properties with a threshold electric field of 1.5 V/mu m and a beta value of 3054. These field-emission properties are also enhanced by illumination, which reveals that the emission behavior is affected by the surface charge state. Therefore, it is suggested that the band structure of MZO NWs has been modulated by phosphorus incorporation. (c) 2006 American Institute of Physics.
Effect of Sn dopant on the properties of ZnO nanowires
(2004-08-21)
Li, SY
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Lin, P
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Lee, CY
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Tseng, TY
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Huang, CJ
Sri doped ZnO (SZO) nanowires were fabricated by a vapour-liquid-solid growth process. The reaction temperature for the formation of the nanowires can be reduced to similar to100degreesC due to Sri doping. The growth direction and morphology of SZO nanowires depend on the amount of Sn, which is attributed to the difference in sizes between Zn and Sri atoms. The ultraviolet emission of SZO nanowires varies from 380 to 396 nm since Sri acts as a doubly ionized donor and introduces deep states in the band gap. In addition, the SZO nanowires exhibit significantly Improved field emission characteristics with a turn-on electric field of 0.05 V mum(-1) under a current density of 0.5 mA cm(-2) in comparison with undoped ZnO nanowires. The work function of the SZO nanowire decreases for higher carrier concentrations and the field enhancement factor increases for smaller diameters. Also, the resistance of the SZO nanowire is decreased for the higher Sri mole fraction. Therefore, it is expected that SZO nanowires can be applied in nano-lasers and flat panel displays in the future.
Electrical characterizations of a controllable field emission triode based on low temperature synthesized ZnO nanowires
(2006-01-14)
Lee, CY
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Tseng, TY
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Li, SY
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Lin, P
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材料科學與工程學系
Fabrication and field emission properties of a ZnO nanowire (NW) triode were investigated in this study. The ZnO NWs have a single-crystalline wurtzite structure, similar to 50 nm diameter and 3.4 x 10(10) cm(-2) number density. The ZnO NW triode shows good and controllable emission properties with the turn-on anode electric field (at a current density of 1 mu A cm(-2)), threshold anode electric field (at a current density of 1 mA cm(-2)) and field enhancement factor of 1.6, 2.1 V mu m(-1) and 3340, respectively. The ZnO NW triode exhibits transistor characteristics with a gate leakage region, linear region and saturation region. Furthermore, the controllable field emission performance of the ZnO NW triode can be enhanced by illumination and argon ion bombardment. A low temperature Si-based microelectronic compatible fabrication process was provided for successfully making ZnO NW based triodes with good field emission properties.
Fabrication of vertical ZnO nanowires on silicon(100) with epitaxial ZnO buffer layer
(2004-11-01)
Li, SY
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Lin, P
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Lee, CY
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Ho, MS
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Tseng, TY
Vertical ZnO nanowires were successfully grown on epitaxial ZnO (002) buffer layer/Si (100) substrate. The nanowire growth process was controlled by surface morphology and orientation of the epitaxial ZnO buffer layer, which was deposited by radio-frequency (rf) sputtering. The copper catalyzed the vapor-liquid-solid growth of ZnO nanowires with diameter of similar to30 nm and length of similar to5.0 mum. The perfect wurtzite epitaxial structure (HCP structure) of the ZnO (0002) nanowires synthesized on ZnO (002) buffer layer/Si (100) substrate results in excellent optical characteristics such as strong UV emission at 380 nm with potential use in nano-optical and nano-electronic devices.
Field emission and photofluorescent characteristics of zinc oxide nanowires synthesized by a metal catalyzed vapor-liquid-solid process
(2004-04-01)
Li, SY
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Lin, P
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Lee, CY
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Tseng, TY
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材料科學與工程學系
The ZnO nanowires synthesized by vapor-liquid-solid growth mechanism with Cu and Au as the catalyst were investigated. The principal differences in morphology between Cu and Au catalyzed ZnO nanowires are observed and lead to significant differences in their field emission and photofluorescent characteristics. The Cu catalyzed ZnO nanowires with a high-quality wurtzite structure were grown vertically on p-type Si(100) substrate along [0002] direction. A strong ultraviolet emission at 381 nm is observed. These ZnO nanowires show excellent field emission properties with turn-on field of 0.83 V/mum and corresponding current density of 25 muA/cm(2). The emitted current density of the ZnO nanowires is 1.52 mA/cm(2) at a bias field of 8.5 V/mum. The large field emission area factor, beta arising from the morphology of the nanowire field emitter, is partly responsible for the good emission characteristics. The ZnO nanowires with high emission current density and low turn-on field are expected to be used in field emission flat panel display. (C) 2004 American Institute of Physics.
Field-emission triode of low-temperature synthesized ZnO nanowires
(2006-05-01)
Lee, CY
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Li, SY
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Lin, P
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Tseng, TY
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材料科學與工程學系
A field-emission triode based on the low-temperature (75 degrees C) and hydrothermally synthesized single-crystalline zinc-oxide nanowires; (ZnO NWs) grown on Si substrate with a silicon dioxide (SiO2) insulator was fabricated for the controllable field-emission device application. Field-emission measurement reveals that the ZnO NWs fabricated on the Si substrate exhibit a good emission property with the turn-on electric field and threshold electric field (current density of 1 mA/cm(2)) of 1.6 and 2.1 V/mu m, respectively, with a field enhancement factor beta of 3340. The field-emission properties of the ZnO NW-based triode exhibit the controllable characteristics. The well-controlled field-emission characteristics can be divided into three parts: gate leakage region, linear region, and saturation region. Therefore, this study provides a low-temperature field-emission triode fabrication process that is compatible with the Si-based microelectronic integration, and the field-emission measurements also reveal that the emission behavior can be well controlled by adopting the triode structure.
Gate-controlled ZnO nanowires for field-emission device application
(2006-01-01)
Li, SY
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Lee, CY
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Lin, P
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Tseng, TY
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材料科學與工程學系
Gate-controlled field-emission devices have great promise for a number of applications such as bright electron source or flat display array. The gate-controlled ZnO nanowire (NW) field-emission device was fabricated using lift-off fabrication process to synthesize side-gate control in the present investigation. This device effectively controls the turn-on electron beams and switches the drain current (Id) under a threshold gate voltage (V-T) of similar to 35 V. In the meantime, the current density of the device is similar to 1 mA/cm(2) that is similar to carbon nanotube (CNT) field-emission level with a potential for the design of field-emission display (FED) devices. Furthermore, when the gate voltage (V-g) is equal to 0 V, the turn-on electric field (E-to) for ZnO NWs is similar to 0.8 V/mu m and the effective-field-enhancement factor 8 is similar to 7000. As Vg is increased to 10, 20, 30, and 40 V, the E, lowers to the range of -0.8-0.6 V/mu m and the 8 value increases to similar to 7600-17 800. The continuous increases in V,, lowers the turn-on electric field because the local electric field (E-local) generated induces an extra force that enhances electron emission from the ZnO NWs. Besides, the transconductance (g) value can approach 0.388 mS while the V-g is increased to 44.5 V. The devices have well-controlled behavior and exhibit better Fowler-Nordheim characteristic in comparison with classic CNT field-emission devices. The gated ZnO NW array has a good opportunity to be applied to FED devices and be integrated to the semiconductor industry in the future. (c) 2006 American Vacuum Society.
Identification of Atractylodes plants in Chinese herbs and formulations by random amplified polymorphic DNA
(2001-06-01)
Chen, KT
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Su, YC
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Lin, JG
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Hsin, LH
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Su, YP
AIM: An efficient, precise, and sensitive method for identifying Atractylodes plants has been established and will contribute significantly to quality control and scientific analysis in Chinese traditional medicine. METHODS: Twenty primers were applied for setting up the RAPD (randomly amplified polymorphic DNA) markers of Atractylodes plants, Atractylodes lancea DC (A lancea MG:), Atractylodes japonica Koidz (A japonica K), and Atractylodes ovata DC (A ovata DC). The primer OPF03, OPF05, and OPF14 could discriminate them successfully. The results were also able to apply on the Chinese formulations with Atractylodes purchased from local markets. RESULTS: RAPD was used to investigate phylogenetic relationships among and within closely related species. RAPD analysis reflects heritable changes in the nucleotides sequence in both the coding and noncoding regions, because it is conducted directly from the DNA level. This work first conducted RAPD analysis of Atractylodes plants to establish their RAPD makers. CONCLUSION: The RAPD markers could be applied extensively in the Chinese herbal formulations.
Low temperature synthesized Sn doped indium oxide nanowires
(2005-04-01)
Li, SY
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Lee, CY
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Lin, P
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Tseng, TY
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材料科學與工程學系
Selective, well controlled and directionally grown Sri doped In2O3 nanowires (In2O3: Sn nanowires, SIO NWs) were synthesized at a low fabrication temperature (&SIM; 770&DEG; C) through a vapour-liquid-solid (VLS) process under a precise carrier gas flow. The majority of the SIO NWs are grown along [222], with [400] and [440] as minority forming directions, which implies a nearly epitaxial crystal structure. There are fewer physical defects, such as line or planar defects and contaminations, in the SIO NWs than in pure In2O3 nanowires seen through high resolution transmission electron microscopy (HR-TEM) observations. The spectrum of photoluminescence (PL) emission indicates a stable strong blue light peak located at &SIM; 440 nm with an excited wavelength of 275 nm at room temperature. The Sri dopant in the SIO NWs can enhance the conductivity of the nanowires leading to the lowering of the turn-on electric-field to 0.66 V μ m(-1) under a current density of up to 1.0 mA cm(-2) based on their field emission characteristics. Furthermore, the field emission enhancement coefficient, β, is also increased to 1.48 x 10(5), which is very close to the carbon nanotube, (CNT) level. SIO NWs fabricated by a VLS process offer a potential application in flat panel displays as demonstrated in this study.
Molecular epidemiology of long-term colonization of Candida albicans strains from HIV-infected patients
(2006-04-01)
Li, SY
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Yang, YL
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Chen, KW
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Cheng, HH
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Chiou, CS
Twenty-one Candida albicans isolates from three HIV-infected patients were collected over a period of 3 years and characterized for fluconazole susceptibility, infectivity and genetic relatedness. Fluconazole resistance was found in five isolates, four exhibited dose-dependent susceptibility and the remainder were fully susceptible to this agent. Pulsed-field gel clectrophoresis of SfiI restriction digests of the genomic DNA from the isolates revealed that isolates from the same swab specimen were identical despite differences in Susceptibility to fluconazole and isolates recovered over time from the three patients retained clonally related DNA fingerprints within each patient. This small-scale study confirms the persistence of oral colonization of C. albicans strains in HIV-infected patients. Clinical data also suggests that the primary infecting strain may become a persistent colonist in the oral cavity once the immune function of the patient has been restored.
Single-crystalline MgxZn1-xO (0 <= x <= 0.25) nanowires on glass substrates obtained by a hydrothermal method: growth, structure and electrical characteristics
(2005-08-01)
Lee, CY
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Tseng, TY
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Li, SY
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Lin, P
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材料科學與工程學系
Single-crystalline Mg-x-Zn1-xO(0 <= x <= 0.25) nanowires (MZONWs) were synthesized on glass substrates by a hydrothermal method using a mixture of an aqueous solution of zinc nitrate hexahydrate, magnesium nitrate hexahydrate and diethylenetriamine at temperatures that ranged from 75 to 105 degrees C. X-ray diffraction, scanning electron microscopy and transmission electron microscopy investigations were carried out to characterize the crystallinity, surface morphologies and orientations of these nanowires, respectively. These nanowires with direct band gaps ranging from 3.21 to 3.95 eV emitted ultraviolet photoluminescence from 406 to 397 nm at room temperature as the Mg content increased. Field emission measurements revealed that the turn-on electric field and threshold electric field (current density of 1 mA cm(-2)) of ZnO NWs are 1.6 and 2.1 V mu m(-1) with the value of 3340. Therefore, low temperature synthesized MZO NWs (0 <= x <= 0.25) with modulated band gaps may be applied in solar cells, light emission devices and other nanoheterojunction devices in the future.
Susceptibilities to amphotericin B and fluconazole of Candida species in TSARY 2002
(2005-03-01)
Yang, YL
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Li, SY
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Cheng, HH
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Lo, HJ
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生物科技學系
Susceptibilities to amphotericin B and fluconazole of 909 Candida species collected during the Taiwan Surveillance of Antimicrobial Resistance of Yeasts (TSARY) in 2002 were determined by the broth microdilution method. There were 395 (43.5%) Candida albicans, 244 (26.8%) C. tropicalis, 187 (20.6%) C. glabrata, 63 (6.9%) C. parapsilosis, 9 (1%) C. krusei, and 11 (1.2%) others. Among them, 23 (2.5%) isolates were resistant to amphotericin B. They consisted of 10 C. glabrata, 6 C. krusei, 3 C. albicans, 1 C. tropicalis, 1 C. parapsilosis, and 2 others. The resistance rate to amphotericin B has increased compared with that of TSARY 1999 (2.5% versus 0.5%). There were 7 C. krusei, 5 C. albicans, 3 C. glabrata, and 2 others isolates resistant to fluconazole. The resistance rate to fluconazole has decreased from 8.4% in 1999 to 1.9% in 2002. A pattern of coresistance to both amphotericin B and fluconazole was observed. (c) 2005 Elsevier Inc. All rights reserved.
The trend of susceptibilities to amphotericin B and fluconazole of Candida species from 1999 to 2002 in Taiwan
(2005-11-03)
Yang, YL
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Li, SY
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Cheng, HH
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Lo, HJ
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生物科技學系
Background: Candida species have various degrees of susceptibility to common antifungal drugs. The extent of resistance to amphotericin B and fluconazole of Candida glabrata isolates causing candidemia has been reported. Active surveillance may help us to monitor the trend of susceptibility to antifungal drugs and to determine if there is an emerging co-resistance to both drugs of Candida species, specifically, of C. glabrata in Taiwan. Methods: The susceptibilities to amphotericin B and fluconazole of Candida species collected in 1999 and 2002 of the Taiwan Surveillance of Antimicrobial Resistance of Yeasts (TSARY) were determined by the microdilution method. Results: The antifungal susceptibilities of 342 and 456 isolates collected from 11 hospitals participating in both TSARY 1999 and TSARY 2002, respectively, have been determined. The resistance rate to amphotericin B has increased from 0.3% in the TSARY1999 to 2.2% in the TSARY 2002. In contrast, the resistance rate to fluconazole has decreased from 8.8% to 2.2%. Nevertheless, significantly more C. glabrata isolates were not susceptible to fluconazole in the TSARY 2002 (47.4%) than that in the TSARY 1999 (20.8%). There were 9.8% and 11% of C. glabrata isolates having susceptible-dose dependent and resistant phenotype to fluconazole in the TSARY 1999, verse 45.3% and 2.1% in the TSARY 2002. Conclusion: There was an increase of resistance rate to amphotericin B in C. glabrata. On the other hand, although the resistance rate to fluconazole has decreased, almost half of C. glabrata isolates were not susceptible to this drug. Hence, continuous monitoring the emerging of coresistance to both amphotericin B and fluconazole of Candida species, specifically, of C. glabrata, will be an important early-warning system.
ZnO nanowires hydrothermally grown on PET polymer substrates and their characteristics
(2005-07-01)
Lee, CY
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Li, SY
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Lin, P
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Tseng, TY
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材料科學與工程學系
Zinc oxide nanowires (ZnO NWs) were successfully synthesized on the]TO/PET polymer substrates by a hydrothermal method. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy investigations were carried out to characterize the crystallinity, surface morphologies, and orientations of these NWs, respectively, The influence of NW surface morphologies on the optical and electrical properties of ZnO NWs was studied, The hydrothermally grown ZnO NWs with direct band gap of 3.21 eV emitted ultraviolet photoluminescence of 406 nm at room temperature. Field emission measurements revealed that the threshold electric fields (E-th, current density of 1 mA/cm(2)) of ZnO NWs/ITO/PET and ZnO NWs/ZnO/ITO/PET are 1.6 and 2,2 V/mu m with the enhancement factors, beta values, of 3275 and 4502, respectively. Furthermore, the field emission performance of ZnO NWs deposited on the ITO/PET substrate can be enhanced by illumination with E-th of 1.3 V/mu m and displays a maximum emission current density of 18 mA/cm(2). The ZnO NWs successfully grown on polymer substrate with high transmittance, low threshold electric field, and high emission current density may be applied to a flexible field emission display in the future.