Browsing by Author "Yang, YL"

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Atomic force microscopy study on the surface structure of oxidized porous silicon
(1996-08-01)
Young, TF
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Huang, IW
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Yang, YL
;
Kuo, WC
;
Jiang, IM
We study the surface structure of porous silicon (PS) using atomic force microscopy (AFM), before and after oxidation in a HNO3 solution. The AFM image shows the PS surface with a self-affine random fractal structure of wires, hillocks and voids in various scales. After oxidization the wires and hillocks of PS structures are glazed with oxide and the voids are filled, PS structure is altered to a simple self-affine fractal structure of hillock clusters. The fractal dimension D of PS is around 2.3, which decreases with increasing oxidization to about 2.0 of a smooth surface for the saturated oxidization. Our direct observation of the fractal structure of PS from AFM data reveals a good explanation for the recently found novel nonlinear de-response in Ag thin films deposited on PS. We find the fractal surface structure of oxidized PS responds to the stepwise avalanche electric breakdown of the resistivity of Ag thin films deposited on oxidized PS.
Blocking the dengue virus 2 infections on BHK-21 cells with purified recombinant dengue virus 2 E protein expressed in Escherichia coli
(2003-09-26)
Chiu, MW
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Yang, YL
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生物科技學系
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Department of Biological Science and Technology
Dengue viruses (DVs) are mosquito-borne infectious pathogens. They have become an expanding public health problem in the tropics and subtropics. The dengue envelope (E) protein is one of the viral structure proteins responsible mainly for the virus attachment and entry onto host cells. It is also the major immunogen for virus neutralization. In this study, we have constructed a recombinant plasmid expressing a truncated E protein of DV-2 virus PL046 strain: The C-terminal hydrophobic domain of the E protein was removed and replaced with the sequence of S peptide to facilitate expression and purification. When expressed in Escherichia coli, the recombinant E proteins were found to be in the form of aggregated state. Through denaturation and dialysis processes, the receptor-interacting function of the purified recombinant E proteins was maintained, which was demonstrated by its ability to inhibit the DV-2 plaque-forming efficiency on mammalian BHK-21 host cells. (C) 2003 Elsevier Inc. All rights reserved.
CaNdt80 is involved in drug resistance in Candida albicans by regulating CDR1
(2004-12-01)
Chen, CG
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Yang, YL
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Shih, HI
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Su, CL
;
Lo, HJ
Overexpression of CDR1, an efflux pump, is one of the major mechanisms contributing to drug resistance in Candida albicans. CDR1 p-lacZ was constructed and transformed into a Saccharomyces cerevisiae strain so that the lacZ gene could be used as the reporter to monitor the activity of the CDR1 promoter. Overexpression of CaNDT80, the C albicans homolog of S. cerevisiae NDT80, increases the beta-galactosidase activity of the CDR1 p-lacZ construct in S. cerevisiae. Furthermore, mutations in CaNDT80 abolish the induction of CDR1 expression by antifungal agents in C albicans. Consistently, the Candt80/Candt80 mutant is also more susceptible to antifungal drugs than the wild-type strain. Thus, the gene for CaNdt80 may be the first gene among the regulatory factors involved in drug resistance in C. albicans whose function has been identified.
Characterization of multilayered Ti/TiN films grown by chemical vapor deposition
(1998-11-02)
Hu, JC
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Chang, TC
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Chen, LJ
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Yang, YL
;
Chang, CY
The resistivity of multilayered Ti/TiN films grown by chemical vapor deposition can be reduced from 240 mu Omega cm (standard sample) to 120 mu Omega cm with NH3 plasma post-treatment for 300 s. Increasing the number of multilayered Ti/TiN mu ms of reduced thickness and a plasma post-treatment technique contributed to reducing the resistivity of TiN films effectively. Smooth multilayered Ti/TiN films were observed by XTEM image. The content of chlorine in the multilayered Ti/TiN film was 1.6 at.%. Therefore, corrosion in the subsequent Al film should be minimized. SIMS depth profiles of the multilayered Ti/TiN sample showed that Ti atom distribution is fairly uniform. The result is in agreement with the observation of XTEM and the measurement of AES depth profiles. The resistivity of multlayered Ti/TiN films can be further reduced to 75 mu Omega cm with an in situ NH3 plasma post-treatment (500 W) for 300 s followed by RTA at 900 degrees C for 60 s. Therefore, low resistivity (<100 mu Omega cm) and low Cl concentration (<2 at.%) CVD TiN films can be achieved by a combination of forming a multilayered Ti/TiN structure, and using NH3 plasma post-treatment and RTA. (C) 1998 Elsevier Science S.A. All rights reserved.
Characterization of TiN film grown by low-pressure-chemical-vapor-deposition
(1997-10-31)
Mei, YJ
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Chang, TC
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Hu, JC
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Chen, LJ
;
Yang, YL
Conformal TiN films were deposited by thermal low-pressure-chemical-vapor-deposition (LPCVD) in a rotating disk reactor, using TiCl4 and NH3 with N-2 as a dilution gas. TiN plug with 0.05 mu m contact size was achieved. No void formation was observed in the TiN plug. The result demonstrated that LPCVD-TiN can be used to fill very small contact holes. The excellent step coverage and uniformity resulted from a surface-reaction-rate-limited deposition. The resistivity of TiN film was reduced to 133 mu Omega cm by in-situ NH3 plasma post-treatment. The concentration of chlorine in the TiN him was measured to be less than 2 atomic % (at.%) by Auger electron spectroscope measurement. For Al deposited on TiN, the Al orientation was found to be dependent on the deposition method of Al film, but not on the underlying TiN orientation. (C) 1997 Elsevier Science S.A.
Colonization of human immunodeficiency virus-infected outpatients in Taiwan with Candida species
(2005-04-01)
Hung, CC
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Yang, YL
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Lauderdale, TL
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McDonald, LC
;
Hsiao, CF
To understand the Candida colonization of human immunodeficiency virus (HIV)-infected outpatients in Taiwan, we have conducted a prospective cohort study of Candida colonization and its risk factors at the National Taiwan University Hospital from 1999 to 2002. More than 50% of the patients were colonized with Candida species, and 12% developed symptomatic candidiasis. Patients colonized with fluconazole-resistant strains of Candida species had a higher prevalence of candidiasis than those colonized with susceptible strains. Our analysis found that antibiotic treatment and lower CD4(+) counts (< 200 cells/mm(3)) increased the rate of oropharyngeal candidiasis in HIV-infected patients, while antiretroviral therapy protected patients from the development of candidiasis.
Comparing lanes in the pulsed-field gel electrophoresis (PFGE) images
(2001)
Cheng, WZ
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Yen, KS
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Lin, CY
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Ching, YT
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Yang, YL
Pulsed-field Gel Electrophoresis (PFGE) is an important tool in genomic analysis. The result of PFGE is presented in an image. Each image contains several lanes. And each lane consists of bands. Two lanes are identical if the relative positions of bands are the same. We present a method that uses computer to extract the lanes and compare the lanes in the electrophoresis images. The presented method consists of two major steps. The first step is image processing and lane extraction. The second step is to convert a lane into chain code representation. The lane comparison is carried out through calculating the longest common subsequence between lanes. We define the distance between lanes in term of the LCS and the lengths of two lanes. Two lanes have smaller distance tend to have similar pattern. This method eliminates those very different patterns to help biologists reduce the lanes that need to be compared.
Distribution and antifungal susceptibility of Candida species causing candidemia from 1996 to 1999
(2004-01-01)
Cheng, MF
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Yu, KW
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Tang, RB
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Fan, YH
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Yang, YL
Susceptibilities to amphotericin B and fluconazole of 383 Candida species isolated from blood were determined. Candida albicans was the most common species (55.6%), followed by Candida parapsilosis (17.5%), Candida tropicalis (16.5%), Candida glabrata (5.2%), Candida guilliermondii (2.3%), and others (2.9%). All but three isolates, Candida ciferrii, C. tropicalis, and C glabrata, one each, were susceptible to amphotericin B. A total of 367 (95.8%) and 15 (4.2%) isolates were susceptible and susceptible-dose dependent to fluconazole, respectively. Only one isolate, a C glabrata, was resistant to fluconazole. Few patients (13%) having prior fluconazole treatments may explain the low rate of resistance to fluconazole in this study. (C) 2004 Elsevier Inc. All rights reserved.
Distribution and susceptibility to amphotericin B and fluconazole of Candida spp. isolated from Taiwan
(2005-04-01)
Yang, YL
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Ho, YA
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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 628 clinical yeast strains collected from 22 hospitals in Taiwan were determined. A total of 53 isolates (8.4%) were resistant to fluconazole. Each hospital had different resistance rate to fluconazole ranging from 0 % to 24 %. None of the 186 isolates from eight of the 22 hospitals was resistant to fluconazole. In contrast, isolates from nine of the remaining 14 hospitals had greater than 10 % resistance rate to fluconazole. Consistently, 88.9 % (8/9) fluconazole-resistant C. albicans isolates were from hospitals having a high resistance rate to fluconazole. The prevalence of various Candida spp. in each hospital was different. A positive association was found between the prevalence of C. tropicalis and the resistance rate to fluconazole for individual hospitals. Although only three isolates (0.5 %) were resistant to amphotericin B, a co-resistance to both amphotericin B and fluconazole was observed, which highlights the emerging problem of drug resistance.
Effect of prolonged HAART on oral colonization with Candida and candidiasis
(2006-01-20)
Yang, YL
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Lo, HJ
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Hung, CC
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Li, YC
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生物科技學系
Background: Progressive cell-mediated immunodeficiency with decrease of CD4+ lymphocyte count to less than or equal to 200 cells/mm(3) is a major risk factor for colonization with Candida species and development of candidiasis. Oropharyngeal candidiasis may occur in up to 90% of human immunodeficiency virus (HIV)-infected patients during the course of the disease. This study is to determine the effect of prolonged highly active antiretroviral therapy (HAART) on oropharyngeal colonization with Candida species and oral candidiasis. Methods: A prospective, longitudinal follow-up study in HIV-infected patients receiving HAART. Results: The mean CD4+ count increased from 232.5 to 316 cells/mm(3) and the proportion of patients whose CD4+ count less than 200 cells/mm(3) decreased from 50.0% to 28.9% (p = 0.0003) in patients receiving HAART for at least 2 years. The prevalence of oral candidiasis decreased from 10.6% to 2.1% (p = 0.004). The decrease in Candida colonization was less impressive, falling from 57.8% to 46.5% (p = 0.06). Of the 142 patients enrolled in at least two surveys, 48 (33.8%) remained colonized with Candida and 42 (29.6%) remained negative. In the remaining 52 patients, 34 switched from culture positive to negative, and an increase in CD4+ lymphocytes was noted in 91.2% of them. Among the 18 patients who switched from culture negative to positive, 61.1% also demonstrated an increase in CD4+ lymphocyte count (p = 0.01). Conclusion: These findings indicate that HAART is highly effective in decreasing oral candidiasis in association with a rise in CD4+ lymphocyte counts, but only marginally effective in eliminating Candida from the oropharynx.
Effectively blocking copper diffusion at low-k hydrogen silsesquioxane/copper interface
(1999-11-01)
Liu, PT
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Chang, TC
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Yang, YL
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Cheng, YF
;
Shih, FY
The interaction between copper and low-k hydrogen silsesquioxane (HSQ) film was investigated using a Cu/HSQ/Si metal insulation semiconductor capacitor and hydrogen plasma posttreatment. Owing to serious diffusion of copper atoms in HSQ film, degradation of the dielectric properties are significant with the increase of thermal stress. By applying hydrogen plasma treatment to the HSQ film, however, the phenomena of serious Cu penetration were not observed by electrical characteristic measurements and secondary ion mass spectroscopy (SIMS) analysis even in the absence of diffusion barrier layers. Therefore, hydrogen plasma treatment can effectively block the diffusion of copper in low-k HSQ film.
Effects of H-2 plasma treatment on low dielectric constant methylsilsesquioxane
(1999-09-01)
Chang, TC
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Liu, PT
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Mei, YJ
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Mor, YS
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Perng, TH
The quality of organic low-k methylsilsesquioxane (MSQ) film is degraded by the damage of oxygen plasma and hygroscopic behavior during photoresist stripping. In addition, the interaction between MSQ and copper is worth investigating. In this work, we have studied the H-2 plasma treatment to improve the quality and enhance the copper penetration resistance of MSQ, Experimental results show the leakage current of MSQ decreases as the H-2 plasma treatment time is increased. The dielectric constant of treated samples also remains constant (similar to 2.7). In addition, the copper diffusion resistance of MSQ film is significantly promoted. The H-2 plasma treatment can provide additional hydrogen to passivate the inner structure of porous MSQ film as well as reduce the probability of moisture uptake and interaction with Cu atoms. Therefore, the low-k dielectric properties of MSQ are significantly enhanced by H-2 plasma treatment. (C) 1999 American Vacuum Society. [S0734-211X(99)05105-7].
Effects of NH3-plasma nitridation on the electrical characterizations of low-k hydrogen silsesquioxane with copper interconnects
(2000-09-01)
Liu, PT
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Chang, TC
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Yang, YL
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Cheng, YF
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Sze, SM
The interaction between topper interconnects and low-k hydrogen silsesquioxane! (HSQ) film was investigated using a Cu/HSQ/Si metal insulation semiconductor capacitor and NH3 plasma post-treatment. Owing to serious diffusion of copper atoms in HSQ film, degradations of the dielectric properties are significant with the increase of thermal stress, The leakage current behavior in high field conduction is well explained by the Poole-Frenkel (P-F) mechanism. By applying NH3-plasma treatment to the HSQ film, however, the leakage current is decreased and P-F conduction can be significantly suppressed. In addition, the phenomenon of serious Cu penetration is not observed by means of electrical characteristic measurements and secondary ion mass spectroscopy (SIMS) analysis even in the absence of diffusion barrier layers. This indicates the copper diffusion in low-k HSQ film can be effectively blocked by NH3 plasma post-treatment.
Efg1 involved in drug resistance by regulating the expression of ERG3 in Candida albicans
(2005-03-01)
Lo, HJ
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Wang, JS
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Lin, CY
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Chen, CG
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Hsiao, TY
The ERG3 gene in Candida albicans was identified as a gene whose mRNA level was higher in the cph1/cph1 efg1/efg1 double mutant than in the wild-type cells. Further study showed that Efg1, but not Cph1, negatively regulated ERG3. Mutations in EFG1 consistently increased the susceptibility of the cells to antifungal agents.
Elimination of dielectric degradation for chemical-mechanical planarization of low-k hydrogen silisesquioxane
(2001-05-01)
Chang, TC
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Liu, PT
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Tsai, TM
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Yeh, FS
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Tseng, TY
The characteristics of post-chemical mechanical polishing (post-CMP) low-k hydrogen silsesquioxane (HSQ) have been investigated in this work. Dielectric properties of HSQ are damaged by the CMP process. We propose NH3-plasma treatment to improve the characteristics of post-CMP HSQ film. Both of the leakage current and dielectric constant of NH3 plasma-treated HSQ are significantly decreased as compared with those of untreated HSQ. NH3 plasma treatment slightly nitridates the surfaces of the polished HSQ film. The thin nitride layer prevents moisture absorption in the post-CMP HSQ. As a result, the dielectric degradation of HSQ after the CMP process can be effectively recovered using the NH3 plasma treatment.
Enhancement of barrier properties in chemical vapor deposited TiN employing multi-stacked Ti/TiN structure
(2000-02-01)
Chang, TC
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Liu, PT
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Yang, YL
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Hu, JC
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Sze, SM
A novel multi-stacked Ti/TiN structure was proposed to enhance the barrier properties of chemical vapor deposited TiN film. Both the chlorine content and the resistivity of the multi-stacked Ti/TiN films are significantly decreased when compared with a single layer of chemical vapor deposited (CVD) TiN film with the same thickness. Secondary ion mass spectrometry (SIMS) data showed that Ti atom distribution is fairly uniform to fill the grain boundary of TiN film. Therefore, the leakage current resulted from junction spiking was further reduced by the grain boundary effects when employing multi-stacked Ti/TiN as diffusion barrier layer instead of a single layer of TiN film.
High-performance integration of copper interconnects with low-k hydrogen silsesquioxane employing deuterium plasma treatment
(2000)
Liu, PT
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Chang, TC
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Yang, YL
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Cheng, YF
;
Lee, JK
The interaction between copper interconnects and low-k hydrogen silsesquioxane (HSQ) film was investigated using a Cu/HSQ/Si metal insulation semiconductor capacitor and deuterium plasma post-treatment. Owing to serious diffusion of copper atoms in HSQ film, the degradations of dielectric properties are significant with the increase of thermal stress. By applying deuterium plasma treatment to HSQ film, however, this degradation was alleviated. In addition, the phenomena of serious Cu penetration were not observed by means of electrical characteristic measurements and secondary ion mass spectroscopy (SIMS) analysis, even in the absence of diffusion barrier layers. This indicates that copper diffusion in low-k HSQ film can be effectively blocked by deuterium plasma post-treatment. Therefore, further improvement in RC reduction can be obtained due to the minimized thickness requirement for conventional barriers such as inorganic Si3N4 and metallic TaN layers.
Identification of trans-regulatory factors of the efflux pumps involved in drug resistance in Candida albicans.
(2003-07-01)
Chen, CG
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Shih, HI
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Yang, YL
;
Lo, HJ
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生物科技學系
Improvement in light-output efficiency of AlGaInP LEDs fabricated on stripe patterned epitaxy
(2005-12-01)
Lee, YJ
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Tseng, HC
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Kuo, HC
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Wang, SC
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Chang, CW
Quaternary AlGaInP light-emitting diodes (LEDs) operating at a wavelength of 630 nm with a stripe-patterned omni-directional reflector (ODR) were fabricated. It is demonstrated that the geometrical shape of stripe-patterned structure improves the light extraction efficiency by increasing the extraction of guided light. The optical and electrical characteristics of stripe-patterned ODR LEDs are presented and compared to typical ODR and distributed Bragg reflector (DBR) LEDs with the same epitaxial structure and emitting wavelength. It is shown that the output power of the stripe-patterned ODR LED exceeds that of the typical ODR and DBR LEDs by a factor of 1.15 and 2 times, respectively, and with an acceptable forward voltage of about 2.2 V.
Improvement in light-output efficiency of near-ultraviolet InGaN-GaN LEDs fabricated on stripe patterned sapphire substrate
(2005)
Lee, YJ
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Hsu, TC
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Kuo, HC
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Wang, SC
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Yang, YL
The output power of GaN-based near ultraviolet stripe patterned sapphire substrate (PSS) LEDs was 20% higher than that of the conventional LEDs. The possible mechanism of this enhancement will be discussed in this report.