Browsing by Author "Ho, Johnny C."

Now showing 1 - 4 of 4

Dielectric Engineering of a Boron Nitride/Hafnium Oxide Heterostructure for High-Performance 2D Field Effect Transistors
(2016-03-09)
Zou, Xuming
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Huang, Chun-Wei
;
Wang, Lifeng
;
Yin, Long-Jing
;
Li, Wenqing
A unique design of a hexagonal boron nitride (h-BN)/HfO2 dielectric heterostructure stack is demonstrated, with few-layer h-BN to alleviate the surface optical phonon scattering, followed by high-kappa HfO2 deposition to suppress Coulombic impurity scattering so that high-performance top-gated two-dimensional semiconductor transistors are achieved. Furthermore, this dielectric stack can also be extended to GaN-based transistors to enhance their performance.
Environmentally and Mechanically Stable Selenium 1D/2D Hybrid Structures for Broad-Range Photoresponse from Ultraviolet to Infrared Wavelengths
(2018-10-17)
Chen, Yu-Ze
;
You, Yen-Ting
;
Chen, Pin Jung
;
Li, Dapan
;
Su, Teng-Yu
Selenium (Se) is one of the potential candidates as photodetector because of its outstanding properties such as high photoconductivity (similar to 8 x 10(4) S cm(-1)), piezoelectricity, thermoelectricity, and nonlinear optical responses. Solution phase synthesis becomes an efficient way to produce Se, but a contamination issue that could deteriorate the electric characteristic of Se should be taken into account. In this work, a facile, controllable approach of synthesizing Se nanowires (NWs)/films via a plasma-assisted growth process was demonstrated at the low substrate temperature of 100 degrees C. The detailed formation mechanisms of nanowires arrays to thin films at different plasma powers were investigated. Moreover, indium (In) layer was used to enhance the adhesive strength with 50% improvement on a SiO2/Si substrate by mechanical interlocking and surface alloying between Se and In layers, indicating great tolerance for mechanical stress for future wearable devices applications. Furthermore, the direct growth of Se NWs/films on a poly(ethylene terephthalate) substrate was demonstrated, exhibiting a visible to broad infrared detection ranges from 405 to 1555 nm with a high on/off ratio of similar to 700 as well as the fast response time less than 25 ms. In addition, the devices exhibited fascinating stability in the atmosphere over one month.
Interface Engineering for High-Performance Top-Gated MoS2 Field-Effect Transistors
(2014-09-24)
Zou, Xuming
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Wang, Jingli
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Chiu, Chung-Hua
;
Wu, Yun
;
Xiao, Xiangheng
Experimental evidence of the optimized interface engineering effects in MoS2 transistors is demonstrated. The MoS2/Y2O3/HfO2 stack offers excellent interface control. Results show that HfO2 layer can be scaled down to 9 nm, yet achieving a near-ideal sub-threshold slope (65 mv/dec) and the highest saturation current (526 mu A/mu m) of any MoS2 transistor reported to date.
Two-Dimensional Cobalt Phosphate Hydroxide Nanosheets: A New Type of High-Performance Electrocatalysts with Intrinsic CoO6 Lattice Distortion for Water Oxidation
(2019-10-23)
Bu, Xiuming
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Chiang, ChaoLung
;
Wei, Renjie
;
Li, Zebiao
;
Meng, You
Despite the recent advances in electrochemical water splitting, developing cost-effective and highly efficient electrocatalysts for oxygen evolution reaction (OER) still remains a substantial challenge. Herein, two-dimensional cobalt phosphate hydroxides (Co-5(PO4)(2)(OH)(4)) nanosheets, a unique stacking-disordered phosphate-based inorganic material, are successfully prepared via a facile and scalable method for the first time to serve as a superior and robust electrocatalyst for water oxidation. On the basis of the detailed characterization (e.g., X-ray absorption near-edge structure and X-ray photoelectron spectroscopy), the obtained nanosheets consist of special zigzag CoO6 octahedral chains along with intrinsic lattice distortion and excellent hydrophilicity, in which these factors contribute to the highly efficient performance of prepared electrocatalysts for OER. Specifically, (Co-5(PO4)(2)(OH)(4)) deposited on glassy carbon electrode (loading amount approximate to 0.553 mg cm -2 ) can exhibit an unprecedented overpotential of 254 mV to drive a current density of 10 mA cm(-2) with a small Tafel slope of 57 mV dec(-1) in alkaline electrolytes, which outperforms the ones of CO3(PO4)(2)(370 mV) and Co(OH)(2) (360 mV) as well as other advanced catalysts. Evidently, this work has opened a new pathway to the rational design of promising metal phosphate hydroxides toward the efficient electrochemical energy conversion.