Browsing by Author "Tseng, Chien-Chih"

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Activating basal-plane catalytic activity of two-dimensional MoS2 monolayer with remote hydrogen plasma
(2016-12)
Cheng, Chia-Chin
;
Lu, Ang-Yu
;
Tseng, Chien-Chih
;
Yang, Xiulin
;
Hedhili, Mohamed Nejib
Two-dimensional layered transition metal dichalcogenide (TMD) materials such as Molybdenum disufide (MoS2) have been recognized as one of the low-cost and efficient electrocatalysts for hydrogen evolution reaction (HER). The crystal edges that account for a small percentage of the surface area, rather than the basal planes, of MoS2 monolayer have been confirmed as their active catalytic sites. As a result, extensive efforts have been developing in activating the basal planes of MoS2 for enhancing their HER activity. Here, we report a simple and efficient approach using a remote hydrogen-plasma process to creating S-vacancies on the basal plane of monolayer crystalline MoS2; this process can generate high density of S-vacancies while mainly maintaining the morphology and structure of MoS2 monolayer. The density of S-vacancies (defects) on MoS2 monolayers resulted from the remote hydrogen-plasma process can be tuned and play a critical role in HER, as evidenced in the results of our spectroscopic and electrical measurements. The H-2-plasma treated MoS2 also provides an excellent platform for systematic and fundamental study of defect-property relationships in TMDs, which provides insights for future applications including electrical, optical and magnetic devices. (C) 2016 Elsevier Ltd. All rights reserved.
An Efficient Application Processor Architecture for Multicore Software Video Decoding
(2015-02-01)
Tsai, Chun-Jen
;
Chen, Yan-Ting
;
Tseng, Chien-Chih
;
資訊工程學系
;
Department of Computer Science
In this paper, we propose a new multicore application processor architecture that facilitates the adoption of the fine-granularity software-pipeline parallelism without causing an extra burden on the system bus. The proposed system-on-a-chip architecture can simultaneously support the traditional symmetric multiprocessor (SMP) and the proposed software-pipeline applications efficiently. The programming model of the proposed architecture is compatible with the existing SMP operating systems. For the implementation of the pipeline-based parallelism, new programmer-friendly system calls are suggested to take advantage of the new software-pipeline datapath. The proposed architecture with four reduced instruction set computing cores is implemented on an field-programmable gate array development board for verification. An Advanced Video Coding/H.264 baseline profile video decoder that explores the pipeline parallelism with dynamic pipeline-stage partitioning is implemented on the target platform to justify the benefits of the proposed architecture. Experimental results show that the adoption of the proposed pipeline datapath architecture into existing application processors enables new potentials in exploring software parallelism.
Enhanced Electrocatalytic Activity of MoSx on TCNQ-Treated Electrode for Hydrogen Evolution Reaction
(2014-10-22)
Chang, Yung-Huang
;
Nikam, Revannath D.
;
Lin, Cheng-Te
;
Huang, Jing-Kai
;
Tseng, Chien-Chih
Molybdenum sulfide has recently attracted much attention because of its low cost and excellent catalytical effects in the application of hydrogen evolution reaction (HER). To improve the HER efficiency, many researchers have extensively explored various avenues such as material modification, forming hybrid structures or modifying geometric morphology. In this work, we reported a significant enhancement in the electrocatalytic activity of the MoSx via growing on Tetracyanoquinodimethane (TCNQ) treated carbon cloth, where the MoSx was synthesized by thermolysis from the ammonium tetrathiomolybdate ((NH4)(2)MoS4) precursor at 170 degrees C. The pyridinic N- and graphitic N-like species on the surface of carbon cloth arising from the TCNQ treatment facilitate the formation of Mo5+ and S-2(2-) species in the MoSx, especially with S-2(2-) serving as an active site for HER. In addition, the smaller particle size of the MoSx grown on TCNQ-treated carbon cloth reveals a high ratio of edge sites relative to basal plane sites, indicating the richer effective reaction sites and superior electrocatalytic characteristics. Hence, we reported a high hydrogen evolution rate for MoSx on TCNQ-treated carbon cloth of 6408 mL g(-1) cm(-2) h(-1) (286 mmol g(-1) cm(-2) h(-1)) at an overpotential of V = 0.2 V. This study provides the fundamental concepts useful in the design and preparation of transition metal dichalcogenide catalysts, beneficial in the development in clean energy
Enhancing the electrocatalytic water splitting efficiency for amorphous MoSx
(2014-03-26)
Hsu, Chang-Lung
;
Chang, Yung-Huang
;
Chen, Tzu-Yin
;
Tseng, Chien-Chih
;
Wei, Kung-Hwa
Amorphous molybdenum sulfide (MoSx) materials have been considered as cheap and promising catalysts for hydrogen evolution reaction (HER). In this contribution, we report that the amorphous MoSx catalysts prepared by the low temperature thermolysis of the (NH4)(2)MoS4 precursors on carbon clothes (catalyst loading: 3.2 mg/cm(2)) exhibit a Tefal slope of 50.5 mV/dec and a high exchange current density of 1.5 x 10(-3) mA/cm(2) in 0.5 M H2SO4 solutions. Spectroscopic studies of the amorphous MoSx catalysts show that the increase of HER efficiency is positively correlated to the concentration of S-2(2-) species, providing strong evidence to support the argument that S-2(2-) is an active species for electrocatalytic HER. Additionally, the method for preparing catalysts is simple, scalable and applicable for large-scale production. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Graphene-Au nanoparticle based vertical heterostructures: A novel route towards high-ZT Thermoelectric devices
(2017-08-01)
Juang, Zhen-Yu
;
Tseng, Chien-Chih
;
Shi, Yumeng
;
Hsieh, Wen-Pin
;
Ryuzaki, Sou
Monolayer graphene exhibits impressive in-plane thermal conductivity (> 1000 W m(-1) K-1). However, the out-of-plane thermal transport is limited due to the weak van der Waals interaction, indicating the possibility of constructing a vertical thermoelectric (TE) device. Here, we propose a cross-plane TE device based on the vertical heterostructures of few-layer graphene and gold nanoparticles (AuNPs) on Si substrates, where the incorporation of AuNPs further inhibits the phonon transport and enhances the electrical conductivity along vertical direction. A measurable Seebeck voltage is produced vertically between top graphene and bottom Si when the device is put on a hot surface and the figure of merit ZT is estimated as 1 at room temperature from the transient Harman method. The polarity of the output voltage is determined by the carrier polarity of the substrate. The device concept is also applicable to a flexible and transparent substrate as demonstrated.
Metal-Guided Selective Growth of 2D Materials: Demonstration of a Bottom-Up CMOS Inverter
(2019-05-03)
Chiu, Ming-Hui
;
Tang, Hao-Ling
;
Tseng, Chien-Chih
;
Han, Yimo
;
Aljarb, Areej
2D transition metal dichalcogenide (TMD) layered materials are promising for future electronic and optoelectronic applications. The realization of large-area electronics and circuits strongly relies on wafer-scale, selective growth of quality 2D TMDs. Here, a scalable method, namely, metal-guided selective growth (MGSG), is reported. The success of control over the transition-metal-precursor vapor pressure, the first concurrent growth of two dissimilar monolayer TMDs, is demonstrated in conjunction with lateral or vertical TMD heterojunctions at precisely desired locations over the entire wafer in a single chemical vapor deposition (VCD) process. Owing to the location selectivity, MGSG allows the growth of p- and n-type TMDs with spatial homogeneity and uniform electrical performance for circuit applications. As a demonstration, the first bottom-up complementary metaloxide-semiconductor inverter based on p-type WSe2 and n-type MoSe2 is achieved, which exhibits a high and reproducible voltage gain of 23 with little dependence on position.
Wafer-scale single-crystal hexagonal boron nitride monolayers on Cu (111)
(2020-03-01)
Chen, Tse-An
;
Chuu, Chih-Piao
;
Tseng, Chien-Chih
;
Wen, Chao-Kai
;
Wong, H. -S. Philip
Ultrathin two-dimensional (2D) semiconducting layered materials offer great potential for extending Moore's law of the number of transistors in an integrated circuit(1). One key challenge with 2D semiconductors is to avoid the formation of charge scattering and trap sites from adjacent dielectrics. An insulating van der Waals layer of hexagonal boron nitride (hBN) provides an excellent interface dielectric, efficiently reducing charge scattering(2,3). Recent studies have shown the growth of single-crystal hBN films on molten gold surfaces(4) or bulk copper foils(5). However, the use of molten gold is not favoured by industry, owing to its high cost, cross-contamination and potential issues of process control and scalability. Copper foils might be suitable for roll-to-roll processes, but are unlikely to be compatible with advanced microelectronic fabrication on wafers. Thus, a reliable way of growing single-crystal hBN films directly on wafers would contribute to the broad adoption of 2D layered materials in industry. Previous attempts to grow hBN monolayers on Cu (111) metals have failed to achieve mono-orientation, resulting in unwanted grain boundaries when the layers merge into films(6,7). Growing single-crystal hBN on such high-symmetry surface planes as Cu (111)(5,8) is widely believed to be impossible, even in theory. Nonetheless, here we report the successful epitaxial growth of single-crystal hBN monolayers on a Cu (111) thin film across a two-inch c-plane sapphire wafer. This surprising result is corroborated by our first-principles calculations, suggesting that the epitaxial growth is enhanced by lateral docking of hBN to Cu (111) steps, ensuring the mono-orientation of hBN monolayers. The obtained single-crystal hBN, incorporated as an interface layer between molybdenum disulfide and hafnium dioxide in a bottom-gate configuration, enhanced the electrical performance of transistors. This reliable approach to producing wafer-scale single-crystal hBN paves the way to future 2D electronics.
Wafer-scale single-crystal hexagonal boron nitride monolayers on Cu (111)
(1970-01-01)
Chen, Tse-An
;
Chuu, Chih-Piao
;
Tseng, Chien-Chih
;
Wen, Chao-Kai
;
Wong, H. -S. Philip
The epitaxial growth of single-crystal hexagonal boron nitride monolayers on a copper (111) thin film across a sapphire wafer suggests a route to the broad adoption of two-dimensional layered semiconductor materials in industry. Ultrathin two-dimensional (2D) semiconducting layered materials offer great potential for extending Moore's law of the number of transistors in an integrated circuit(1). One key challenge with 2D semiconductors is to avoid the formation of charge scattering and trap sites from adjacent dielectrics. An insulating van der Waals layer of hexagonal boron nitride (hBN) provides an excellent interface dielectric, efficiently reducing charge scattering(2,3). Recent studies have shown the growth of single-crystal hBN films on molten gold surfaces(4) or bulk copper foils(5). However, the use of molten gold is not favoured by industry, owing to its high cost, cross-contamination and potential issues of process control and scalability. Copper foils might be suitable for roll-to-roll processes, but are unlikely to be compatible with advanced microelectronic fabrication on wafers. Thus, a reliable way of growing single-crystal hBN films directly on wafers would contribute to the broad adoption of 2D layered materials in industry. Previous attempts to grow hBN monolayers on Cu (111) metals have failed to achieve mono-orientation, resulting in unwanted grain boundaries when the layers merge into films(6,7). Growing single-crystal hBN on such high-symmetry surface planes as Cu (111)(5,8) is widely believed to be impossible, even in theory. Nonetheless, here we report the successful epitaxial growth of single-crystal hBN monolayers on a Cu (111) thin film across a two-inch c-plane sapphire wafer. This surprising result is corroborated by our first-principles calculations, suggesting that the epitaxial growth is enhanced by lateral docking of hBN to Cu (111) steps, ensuring the mono-orientation of hBN monolayers. The obtained single-crystal hBN, incorporated as an interface layer between molybdenum disulfide and hafnium dioxide in a bottom-gate configuration, enhanced the electrical performance of transistors. This reliable approach to producing wafer-scale single-crystal hBN paves the way to future 2D electronics.