Browsing by Author "Li, Yuan-Yao"

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Influences of Contact Metals on the Performances of MoS2 Devices under Strains
(2019-12-19)
Tseng, Sian-Hong
;
Chen, Hung-Yi
;
Hsu, Wei-Ting
;
Wang, Hsiang-Chen
;
Li, Yuan-Yao
The growth of large-area MoS2 films was achieved through atmospheric pressure chemical vapor deposition via vapor management in this study. The thickness of the MoS2 film changed upon varying the amount of vapor deposited on the substrate. Gratifyingly, large-area monolayer MoS2 was obtained under controlled conditions. Studies using transmission electron microscopy and second harmonic generation confirmed that the MoS2 films were composed of grains having sizes ranging from 40 to 70 mu m. Flexible MoS2 device arrays were fabricated on a polyimide substrate; the device arrays displayed high spatial uniformity in their carrier transport properties. The contact metals affected the electrical characteristics of the MoS2 devices under strain; the sensitivity of devices featuring Schottky contacts was higher than that of those with ohmic contacts. Importantly, the device arrays exhibit sensitive and endurance performances under strain cycles of up to 10(5) times. These results suggest a means for the feasible growth of large-area single-layer MoS2 films, as well as the exploitation of flexible MoS2 device arrays in strain and human motion sensor applications.
Silver-carbon nanocapsule electrocatalyst for oxygen reduction reaction
(2007)
Wu, Cheng-Yeou
;
Wu, Pu-Wei
;
Lin, Pang
;
Li, Yuan-Yao
;
Lin, Ying-Mei
The types of carbonaceous material and electrocatalyst are the critical components in fabrication of gas diffusion electrodes for fuel cells and metal-air batteries. In this study, carbon nanocapsule (15-30 nm) and Ag-carbon nanocapsule powders were synthesized and characterized for their electrochemical performances as oxygen reduction electrocatalyst in alkaline electrolyte using commercial noncatalyzed gas diffusion electrode as substrate. The i-V polarization response of the carbon nanocapsule demonstrated enhanced electrocatalytic capability over those of XC-72R and vapor growth carbon fiber, delivering 0.80 V at 200 mA/cm(2). In addition, Ag-carbon nanocapsule powders exhibited a value of 0.99 V at 200 mA/cm(2), surpassing commercially available Mn-catalyzed, and MnCo-catalyzed gas diffusion electrodes. Galvanostatic discharge of these Ag-carbon nanocapsule powders from 10 to 200 mA/cm(2) confirmed their stability and sustainability. This report identified a class of carbon material that not only exhibits electrocatalytic capability itself but also provides opportunity as substrate for known electrocatalysts. (c) 2007 The Electrochemical Society.
Synthesis of Petal-Like Carbon Nanocapsule@MnO2 Core-Shell Particles and Their Application in Supercapacitors
(2014)
Lee, Ting-Ting
;
Hong, Jing-Ru
;
Lin, Wei-Chen
;
Hu, Chi-Chang
;
Wu, Pu-Wei
Carbon nanocapsule (CNC)@MnO2 core-shell particles are prepared with a reaction of KMnO4 with CNC at 90 degrees C. Birnessite-type MnO2 nanoflakes are grown on CNC seeds, resulting in CNC@MnO2 particles with a petal-like structure. The electrochemical characteristics of the prepared materials show that the highest specific capacitance (163 Fg(-1)) was obtained with a scan rate of 2 mVs(-1) in 1 M Na2SO4. In addition, the synthesized material has superior cycling stability. The capacitance retains 97.8% of its initial value after 5000 cycles with a scan rate of 100 mVs(-1). (C) 2014 The Electrochemical Society. All rights reserved.