C Y Liu

Indiana University Bloomington, Bloomington, Indiana, United States

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Publications (162)265.3 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: In this study, we have established a sulfurization resistance test, which is an immersion process in 0.01 M Na2S solution for 10 min. By using this process, we found that the sulfurized Ag reflector drops significantly over 52%. However, the Ag-Pd alloy reflector does not drop as much as the Ag reflector. The minimum reduction rate (around 20%) occurs at the Ag-Pd reflector with a Pd content of 3.72 at.%. It means that there is an optimal surface Pd content (around 3.72 at.%) for the reduction in reflectivity. Above, two effects of Pd alloying atoms on the sulfurization of the surface Ag atoms have been drawn, which are (1) chemical-state change effect and (2) surface microstructure effect. We found that the chemical-state change effect retards the sulfurization of the surface Ag atoms, but the surface microstructure effect (increase in Ag (111) plane) promotes the sulfurization of the surface Ag atoms. Here, we believe that these two opposite effects explain that there is an optimal Pd content on the Ag-Pd surface for the resistance of the sulfurization on the Ag surface.
    No preview · Article · Oct 2015 · Journal of Electronic Materials
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    ABSTRACT: The development of organs with an epithelial parenchyma relies on reciprocal mesenchymal-epithelial communication. Mouse corneal epithelium stratification is the consequence of a coordinated developmental process based on mesenchymal-epithelial interactions. The molecular mechanism underlying these interactions remains unclear. The Wnt/β-catenin signaling pathway is involved in fundamental aspects of development through the regulation of various growth factors. Here, we show that conditional ablation of either β-catenin (Ctnnb1cKO) or co-receptors Lrp5/6 (Lrp5/6cKO) in corneal stromal cells results in precocious stratification of the corneal epithelium. By contrast, ectopic expression of a murine Ctnnb1 gainof- function mutant (Ctnnb1cGOF) retards corneal epithelium stratification. We also discovered that Bmp4 is upregulated in the absence of β-catenin in keratocytes, which further triggers ERK1/2 (Mapk3/1) and Smad1/5 phosphorylation and enhances transcription factor p63 (Trp63) expression in mouse corneal basal epithelial cells and in a human corneal epithelial cell line (HTCE). Interestingly, mouse neonates given a subconjunctival BMP4 injection displayed a phenotype resembling that of Ctnnb1cKO. Conditional ablation of Bmp4 eradicates the phenotype produced in Ctnnb1cKO mice. Furthermore, ChIP and promoter-luciferase assays show that β-catenin binds to and suppresses Bmp4 promoter activity. These data support the concept that cross-talk between the Wnt/β-catenin/ Bmp4 axis (in the stromal mesenchyme) and Bmp4/p63 signaling (in the epithelium) plays a pivotal role in epithelial stratification during corneal morphogenesis.
    No preview · Article · Oct 2015 · Development
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    ABSTRACT: This study was conducted to investigate the reflectivity and the reflectivity stability of the electroless (Ag) metallization of reflectors used in high-brightness white GaN light-emitting diode packages. Two main reflector metallization schemes were studied: (1) electroless-Ag/electroless-pure-Pd/electroless-Ni plating and (2) electroless-Ag/electroless-Pd(P)/electroless-Ni plating. The reflectivity achieved using all reflector-metallization schemes was >85% in the visible range. However, in the electroless-Ag/electroless-pure-Pd/electroless-Ni reflector, reflectivity exhibited substantial thermal degradation; this was because of two principal factors: (1) the change in the surface morphology of the electroless-Ag surface grains; and (2) the alloying effect on the Ag layer exerted by the interdiffusion occurring with the underlying Pd layer. In this study, P was added to the Pd layer, and the thermal degradation of the annealed electroless-Ag/electroless-Pd(P)/electroless-Ni reflector was measured to be less than that of the electroless-Ag/electroless-pure-Pd/electroless-Ni reflector. The P content retarded the interdiffusion between the Ag and Pd(P) layers and preserved the faceted surface of the electroless-Ag layer, which enhanced the stability of the reflectivity of the electroless-Ag reflector. Furthermore, increasing the thickness of the electroless-Ag layer reduced the amount of Pd diffusing through the Ag layer, which helped retain the reflectivity of the Ag surface.
    No preview · Article · Dec 2014 · Journal of Electronic Materials
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    ABSTRACT: By die-attaching GaN-based light-emitting diodes (LEDs) on Si substrates with eutectic AuSn solder, the external quantum efficiency of the LEDs was enhanced by 3.5% at a current input of 120 A/cm (^{2}) . The enhancement of the external quantum efficiency of the die-attached LED chips is attributed to a reduction in compressive stress and piezoelectric fields in quantum wells after eutectic AuSn die-attachment. Raman and photoluminescence analyses were used to estimate the reduction in compressive stress and piezoelectric field in quantum wells, which is 277.8 MPa and 0.056 MV/cm, respectively, after AuSn die-attachment.
    No preview · Article · Sep 2014 · IEEE Photonics Technology Letters
  • C. Y. Liu · Y. C. Hsu · Y. J. Hu · T. S. Huang · C. T. Lu · A. T. Wu
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    ABSTRACT: A back-fill Sn flow is reported against the current-stressing at Sn/Cu micro-joint interface. Upon current-stressing, as the cathode Cu 6Sn5 compound is dissolving into adjacent Sn solder matrix, Cu in the dissolving Cu6Sn5 compound region would be highlydepleted, which would likely transform to highly-vacant Sn grains. Thus, a large Sn concentration gradient would be established between the highly-vacant Sn grains (dissolving Cu6Sn5 compound) and the Sn solder matrix, which causes Sn atoms diffusing into the newly-formed Sn grains. The driving force of the back-fill Sn flow was evaluated and, indeed, it can overcome the electromigration force.
    No preview · Article · Dec 2013 · ECS Solid State Letters
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    ABSTRACT: Various microstructural zones were observed in the solidified solder of flip-chip solder joints with three metal bond-pad configurations (Cu/Sn/Cu, Ni/Sn/Cu, and Cu/Sn/Ni). The developed microstructures of the solidified flip-chip solder joints were strongly related to the associated metal bond pad. A hypoeutectic microstructure always developed near the Ni bond pad, and a eutectic or hypereutectic microstructure formed near the Cu pad. The effect of the metal bond pads on the solder microstructure alters the Cu solubility in the molten solder. The Cu content (solubility) in the molten Sn(Cu) solder eventually leads to the development of particular microstructures. In addition to the effect of the associated metal bond pads, the developed microstructure of the flip-chip solder joint depends on the configuration of the metal bond pads. A hypereutectic microstructure formed near the bottom Cu pad, and a eutectic microstructure formed near the top Cu pad. Directional cooling in the flip-chip solder joint during the solidification process causes the effects of the metal bond-pad configuration. Directional cooling causes the Cu content to vary in the liquid Sn(Cu) phase, resulting in the formation of distinct microstructural zones in the developed microstructure of the flip-chip solder joint.
    No preview · Article · Oct 2013 · Journal of Electronic Materials
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    ABSTRACT: Comparative study on the interfacial reactions between lead-free Sn-Ag-Cu solder and Ni(P) bond pads (with columnar or layered microstructure) has been performed. The microstructure of the columnar Ni(P) is vertical, while the microstructure of the layered Ni(P) tends to be parallel to the solder/Ni(P) interface. The consumption rate of the columnar Ni(P, 7 at.%) layer is larger than that of the layered Ni(P, 7 at.%). We believe that the faster Ni(P) consumption rate of the columnar Ni(P, 7 at.%) layer is due to the orientation of the grains. Spalling of the interfacial (Cu,Ni)6Sn5 compound can be seen at the reaction interfaces for the columnar Ni(P, 7 at.%) layer. On the contrary, no spalling can be seen for the case of the reacted layered Ni(P).
    No preview · Article · Oct 2013 · Journal of Electronic Materials
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    ABSTRACT: Epitaxial Cu3Sn and Cu6Sn5 grown by liquid-phase electroepitaxy (LPEE) have been demonstrated in this work. X-ray diffraction analysis reveals that LPEE-grown Cu3Sn and Cu6Sn5 grew in particular directions (planes) with respect to the electron flow. LPEE-grown Cu3Sn grew in the (020) and (400) directions, and LPEE-grown Cu6Sn5 grew in the (204) and (62 (3) over bar) directions. With the aid of a molecular simulation software tool, we conclude that the particular growth directions represent the low-resistance paths for electron flow. This means that, along those particular directions in the LPEE-grown Cu-Sn compounds, the traveling electrons would be scattered least by the lattice. Thus, as the electromigrating Cu atoms form Cu-Sn compound, the newly forming Cu-Sn unit cells would orientate themselves in those particular growth directions to facilitate electron flow. Then, the well-oriented newly formed Cu-Sn compound unit cells can incorporate the growth of the highly orientated LPEE-grown Cu-Sn compounds. In addition, the anisotropy of a number of properties of LPEE-grown Cu3Sn and Cu6Sn5, i.e. coefficient of thermal expansion, Vickers microhardness and electrical properties (resistivity, carrier mobility and carrier concentration), along the particular orientations were measured and reported.
    No preview · Article · Sep 2013 · Acta Materialia
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    ABSTRACT: InGaN/GaN multiple-quantum-well solar cells were grown on (111) Si substrates. AlN/AlGaN superlattice and self-assembly Si x N y masking islands were employed to alleviate the material mismatches between Si and GaN. The devices were characterized under the illumination of AM 1.5 G with different solar concentrations. As the concentration ratios increased from 1-sun to 105-sun, energy conversion efficiency was enhanced by 25%, which was noticeably greater than the enhancement reported on sapphire substrates under similar solar concentrations. The result is attributed to the superior heat sinking of Si substrates. &
    Full-text · Article · May 2013 · Solar Energy Materials and Solar Cells
  • S.H. Wu · Y.J. Hu · C.T. Lu · T.S. Huang · Y.H. Chang · C.Y. Liu
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    ABSTRACT: This study investigates the electromigration (EM) effect under a high current density (104 A/cm2) on the different interfacial compound phases at Sn(Cu) solder/electroless nickel immersion gold (ENIG) interfaces. The interfacial Ni3Sn4 phase at the Sn-0.7 wt.%Cu/ENIG joint interface was quickly depleted after a short period (50 h) of current stressing. The inference drawn is that the Ni atoms in the Ni3Sn4 phase at the joint interface are likely forced out under current stressing; however, the ternary (Cu,Ni)6Sn5 compound effectively reduces the EM-driven Ni flux into the Sn bump; thus, a significantly lower Ni(P) consumption was observed at the Sn-1 wt.%Cu/ENIG interface. The EM-induced Ni(P) dissolution rates in the Sn-0.2 wt.%Cu/ENIG and Sn-1 wt.%Cu/ENIG cases were calculated to be 0.028 μm/h and 0.018 μm/h, respectively. In addition, significant EM-assisted Ni3P formation was observed for the current-stressed Sn-0.2 wt.%Cu/ENIG and Sn-0.7 wt.%Cu/ENIG cases; however, for the Sn-1 wt.%Cu/ENIG case, formation of a Ni3P layer was scarcely observed. Moreover, the initial (Cu,Ni)6Sn5 that formed at the interface appeared compact with a layer-type structure, which reduced the EM-driven Ni diffusion.
    No preview · Article · Dec 2012 · Journal of Electronic Materials
  • C.-Y. Liu · Y. Zhang · M. Call · W.W.-Y. Kao
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    ABSTRACT: We have recently reported that excess fibroblast growth factor-7 (FGF-7) in Krt12rtTA/rtTA/tetO-FGF-7 double transgenic mice induced by doxcycline (Dox) resulted in a corneal epithelial tumor resembling human ocular surface squamous neoplasia (OSSN) (Chikama et al. Am. J. Pathol. 172:638-649). Here, we further investigate the role of β-catenin in mediating FGF-7 induced corneal tumorigenesis. Pannus surgically removed from OSSN patients all had nuclear β- catenin and exhibited excess FGF-7. In vitro, FGF-7 induces stabilization and nuclear translocation of β-catenin in human corneal epithelial cells. In vivo, conditional knock-out of β-catenin gene (Ctnnb1) did not have significant effects on corneal morphogenesis or homeostasis, but abolished OSSN formation in Doxtreated Krt12rtTA/rtTA/tetO-FGF-7/tetO-Cre/Ctnnb1lox(E2-6)/lox(E2-6) mice. These results suggest that β-catenin plays a pivotal role in mediating the formation of OSSN. Thus, the administration of inhibitor(s) that prevents activation of β-catenin may be beneficial for treating OSSN.
    No preview · Article · Feb 2012
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    ABSTRACT: A sensing circuit in 0.35 μm CMOS technology for CMOS MEMS capacitive accelerometers has been designed in this work with emphasis on managing noise, sensor offset, and the dc bias at input terminals. The issue of dc bias is particularly addressed and an efficient method is proposed. An example of integrating surface micromachined sensors and the designed sensing circuits on the same chip is demonstrated. Experimental results showed that the proposed circuit led to good noise performance, the random offset in the sensors was efficiently compensated, and the input dc bias voltage was well maintained. The sensitivity of the accelerometer is 457 mV/g. The output noise floor is 54 μg/√Hz, which corresponds to an effective capacitance noise floor of 0.0162 aF/√Hz. The total area of the dual-axis surface micromachined accelerometer chip is 5.66 mm2 and the current consumption is 1.56 mA under a 3.3 V voltage supply.
    Preview · Article · Nov 2011 · Circuits and Systems I: Regular Papers, IEEE Transactions on
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    S S Tan · C Y Liu · L K Yeh · Y H Chiu · Klaus Y J Hsu
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    ABSTRACT: Structure curling induces thermal instability into CMOS MEMS capacitive sensors. The charging effect during reactive ion etching damages the existing on-chip MOS transistors and drastically reduces the yield rate of chips. This paper presents a novel post-CMOS process that solves the problems and leads to CMOS MEMS capacitive sensors with high sensitivity and thermal stability. The novel process was demonstrated with a capacitive accelerometer in 0.35 µm CMOS technology. The accelerometer contains a thermally stable MEMS sensor and an on-chip CMOS sensing circuit with a chopper stabilization scheme. The temperature stabilization was achieved by forming a thick single-crystal silicon (SCS) layer at the bottom of the multi-layer MEMS structure. No leakage current due to charge damage was ever observed in the sample chips. The proposed process also led to minimal undercut of the SCS layer after MEMS structure release. The sensitivity of the accelerometer is 595 mV g−1, and the overall noise floor is 50 µg Hz−1/2 which corresponds to an effective capacitance noise floor of 0.024 aF Hz−1/2. The zero-g temperature coefficient of the accelerometer output voltage is only 1 mV °C−1 in the temperature range from 0 to 70 °C, which corresponds to an effective acceleration variation rate of 1.68 mg °C−1.
    Preview · Article · Feb 2011 · Journal of Micromechanics and Microengineering
  • C.-Y. Liu · Y. Zhang · M. Call · W.W.-Y. Kao
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    ABSTRACT: This book investigates the role of β-catenin in mediating FGF-7 induced corneal tumorigenesis. Pannus surgically removed from OSSN patients all had nuclear β-catenin and exhibited excess FGF-7. In vitro, FGF-7 induces stabilization and nuclear translocation of β-catenin in human corneal epithelial cells. In vivo, conditional knock-out of β-catenin gene (Ctnnb1) did not have significant effects on corneal morphogenesis or homeostasis, but abolished OSSN formation in Dox-treated Krt12rtTA/rtTA/tetO-FGF-7/tetO-Cre/Ctnnb1lox(E2-6)/lox(E2-6) mice. These results suggest that β-catenin plays a pivotal role in mediating the formation of OSSN. Thus, the administration of inhibitor(s) that prevents activation of β-catenin may be beneficial for treating OSSN.
    No preview · Article · Jan 2011
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    ABSTRACT: A counter electrode was prepared for a dye-sensitized solar cell (DSSC) by depositing a thin film of platinum with nanoparticles, each containing multiple pores. We used a thin film of polystyrene nanoparticles as the template on the FTO substrate and electrodeposited the Pt film on the template by cyclic voltammetry (CV). The template was then removed by heating the film at 385 °C for 15 min. A Pt film with nanoparticles containing multiple pores was obtained.
    No preview · Article · Jan 2011
  • S.S. Tan · C.Y. Liu · L.K. Yeh · Y.H. Chiu · K.Y.J. Hsu
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    ABSTRACT: This work reports a new wafer-level post-CMOS process with double-side DRIE for fabricating high-sensitivity, thermally stable capacitive accelerometers. The resultant sensor structures have high aspect ratio (beams with 2.5 μm gaps and 56.2 μm beam thickness comprising 5 μm metal-oxide layers and 51.2 μm single-crystal silicon layer) and show the insensitivity to residual stress and temperature change. Moreover, this method avoids the charge damage problem during the dry-etching procedure. For demonstration, an accelerometer sensor was fabricated by using the proposed process and was integrated with an on-chip sensing circuit in commercial 0.35 μm 2P4M CMOS process. High detection sensitivity of 595 mV/g and low thermal variation of 1.68 mg/°C were achieved.
    No preview · Conference Paper · Jan 2011
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    ABSTRACT: Ni diffusion in Cu6Sn5 intermetallic compound was investigated. First, we successfully fabricated preferred-orientation Cu6Sn5 crystal by liquid-phase electroepitaxy (LPEE). Then, Ni/Cu6Sn5 diffusion couples were produced by sputtering from a Ni thin film onto the Cu6Sn5 crystal. Ni/Cu6Sn5 diffusion couples were annealed at different temperatures of 120°C, 160°C, 200°C, 255°C, 290°C, and 320°C for 2 h in a vacuum. The Ni atomic profile across the Ni/Cu6Sn5 interface was obtained by electron spectroscopy for chemical analysis (ESCA). From the Ni atomic profiles, the Matano method was used to evaluate the Ni interdiffusion coefficients ( $ \tilde{D}_{\rm{Ni}} $ ) in the Cu6Sn5 crystal obtained with different annealing temperatures, which then yields the activation energy for Ni diffusion in the Cu6Sn5 crystal at a particular Ni content. We found that, as Ni diffuses in the ternary Cu6−x Nix Sn5 compound phase, the activation energy of Ni interdiffusion decreases with the Ni content.
    No preview · Article · Jan 2011 · Journal of Electronic Materials
  • C. T. Lu · T.S. Huang · C.H. Cheng · H.W. Tseng · C.Y. Liu
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    ABSTRACT: Cross-interactions between Cu/Sn/Pd and Ni/Sn/Pd sandwich structures were investigated in this work. For the Cu/Sn/Pd case, the growth behavior and morphology of the interfacial (Pd,Cu)Sn4 compound layer was very similar to that of the single Pd/Sn interfacial reaction. This indicates that the growth of the (Pd,Cu)Sn4 layer at the Sn/Pd interface would not be affected by the opposite Cu/Sn interfacial reaction. We can conclude that there is no cross-interaction effect between the two interfacial reactions in the Cu/Sn/Pd sandwich structure. For the Ni/Sn/Pd case, we observed that: (1) after 300s of reflow time, the (Pd,Ni)Sn4 compound heterogeneously nucleated on the Ni3Sn4 compound layer at the Sn/Ni interface; (2) the growth of the interfacial PdSn4 compound layer was greatly suppressed by the formation of the (Pd,Ni)Sn4 compound at the Sn/Ni interface. We believe that this suppression of PdSn4 growth is caused by heterogeneous nucleation of the (Pd,Ni)Sn4 compound in the Ni3Sn4 compound layer, which decreases the free energy of the entire sandwich reaction system. The difference in the chemical potential of Pd in the PdSn4 phase at the Pd/Sn interface and in the (Pd,Ni)Sn4 phase at the Sn/Ni interface is the driving force for the Pd atomic flux across the molten Sn. The diffusion of Ni into the ternary (Pd,Ni)Sn4 compound layer controls the Pd atomic flux across the molten Sn and the growth of the ternary (Pd,Ni)Sn4 compound at the Sn/Ni interface. KeywordsInterfacial reaction–solder joint–ENEPIG–cross-interaction
    No preview · Article · Jan 2011 · Journal of Electronic Materials
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    ABSTRACT: The interfacial reactions between electroplated Ni-yCo alloy layers and Sn(Cu) solders at 250°C are studied. For pure Co layers, CoSn3 is the only interfacial compound phase formed at the Sn(Cu)/Co interfaces regardless of the Cu concentration. Also, the addition of Cu to Sn(Cu) solders has no obvious influence on the CoSn3 compound growth at the Sn(Cu)/Co interfaces. For Ni-63Co layers, (Co,Ni,Cu)Sn3 is the only interfacial compound phase formed at the Sn(Cu)/Ni-63Co interfaces. Unlike in the pure Co layer cases, the Cu additives in the Sn(Cu) solders clearly suppress the growth rate of the interfacial (Co,Ni,Cu)Sn3 compound layer. For Ni-20Co layers, the interfacial compound formation at the Sn(Cu)/Ni-20Co interfaces depends on the Cu content in the Sn(Cu) solders and the reflow time. In the case of high Cu content in the Sn(Cu) solders (Sn-0.7Cu and Sn-1.2Cu), an additional needle-like interfacial (Ni x ,Co y ,Cu1−x−y )3Sn4 phase forms above the continuous (Ni x ,Cu y ,Co1−x−y )Sn2 compound layer. The Ni content in the Ni-yCo layer can indeed reduce the interfacial compound formation at the Sn(Cu)/Ni-yCo interfaces. With pure Sn solders, the thickness of the compound layer monotonically decreases with the Ni content in the Ni-yCo layer. As for reactions with the Sn(Cu) solders, as the compound thickness decreases, the Ni content in the Ni-yCo layers increases. KeywordsInterfacial reactions-Sn(Cu) solder
    Preview · Article · Nov 2010 · Journal of Electronic Materials
  • S.S. Tan · C.Y. Liu · L.K. Yeh · Y.H. Chiu · M.S.-C. Lu · K.Y.J. Hsu
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    ABSTRACT: An integrated high-sensitivity CMOS MEMS capacitive accelerometer with thermal stability has been designed and demonstrated in this work. Issue of obtaining stable DC bias at input terminals is particularly addressed. Sensitivity of 595 mV/g is achieved in the accelerometer and the overall noise floor is 50 μg/√Hz, which corresponds to an effective capacitance noise floor of 0.024 aF/√Hz. The zero-g thermal variation is as low as 1.68 mg/°C.
    No preview · Conference Paper · Oct 2010

Publication Stats

2k Citations
265.30 Total Impact Points

Institutions

  • 2015
    • Indiana University Bloomington
      Bloomington, Indiana, United States
  • 2003-2015
    • National Central University
      • Department of Chemical & Materials Engineering
      Таоюань, Taiwan, Taiwan
  • 2013
    • Central University of the Caribbean
      Bayamon, Cidra, Puerto Rico
  • 2009-2011
    • National Tsing Hua University
      Hsin-chu-hsien, Taiwan, Taiwan
  • 2001
    • National Health Research Institutes
      Miao-li-chieh, Taiwan, Taiwan
  • 1993-2001
    • University of Cincinnati
      • Department of Ophthalmology
      Cincinnati, Ohio, United States
  • 1988-2001
    • Taipei Veterans General Hospital
      • • Infectious Diseases DIvision
      • • Division of Emergency Medicine
      • • Department of Medicine
      T’ai-pei, Taipei, Taiwan
  • 1993-2000
    • National Yang Ming University
      • • School of Medicine
      • • Department of Internal Medicine
      Taipei, Taipei, Taiwan
  • 1995
    • Shin Kong Wu Ho-Su Memorial Hospital
      T’ai-pei, Taipei, Taiwan
  • 1994
    • Bascom Palmer Eye Institute
      Miami, Florida, United States
  • 1992
    • National Defense Medical Center
      T’ai-pei, Taipei, Taiwan