10 results on '"Wei-chen Yang"'
Search Results
2. Comprehensive Non-volatile Photo-programming Transistor Memory via a Dual-Functional Perovskite-Based Floating Gate
- Author
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Wei-Chen Yang, Tsung-Han Chuang, Chu-Chen Chueh, Yan-Cheng Lin, Jeun-Yan Lam, Ming-Yun Liao, Guan-Syuan Li, Wen-Chang Chen, Yun-Fang Yang, and Li-Che Hsu
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Materials science ,business.industry ,Transistor ,Biasing ,02 engineering and technology ,Energy consumption ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,law.invention ,law ,Electrode ,Optoelectronics ,General Materials Science ,Electronics ,Photonics ,0210 nano-technology ,business ,Communication channel ,Data transmission - Abstract
Photonic transistor memory has received increasing attention as next-generation optoelectronic devices for light fidelity (Li-Fi) application due to the attractive advantages of ultra-speed, high security, and low power consumption. However, most transistor-type photonic memories developed to date still rely on electrical bias for operation, imposing certain limits on data transmission efficiency and energy consumption. In this study, the dual manipulation of "photo-writing" and "photo-erasing" of a novel photonic transistor memory is successfully realized by cleverly utilizing the complementary light absorption between the photoactive material, n-type BPE-PTCDI, in the active channel and the hybrid floating gate, CH3NH3PbBr3/poly(2-vinylpyridine). The fabricated device not only can be operated under the full spectrum but also shows stable switching cycles of photo-writing (PW)-reading (R)-photo-erasing (PE)-reading (R) (PW-R-PE-R) with a high memory ratio of ∼104, and the memory characteristics possess a stable long-term retention of >104 s. Notably, photo-erasing only requires 1 s light illumination. Due to the fully optical functionality, the rigid gate electrode is removed and a novel two-terminal flexible photonic memory is fabricated. The device not only exhibits stable electrical performance after 1000 bending cycles but also manifests a multilevel functional behavior, demonstrating a promising potential for the future development of photoactive electronic devices.
- Published
- 2021
3. Determining Nonlinear Optical Coefficients of Metals by Multiple Angle of Incidence Heterodyne-Detected Sum-Frequency Generation Spectroscopy
- Author
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Bertrand Busson, Dennis K. Hore, Wei-Chen Yang, Department of Chemistry, University of Victoria, University of Victoria [Canada] (UVIC), Institut de Chimie du CNRS (INC), Institut de Chimie Physique (ICP), Institut de Chimie du CNRS (INC)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Department of Computer Science, University of Victoria
- Subjects
[PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics] ,Materials science ,010304 chemical physics ,Plane of incidence ,General Physics and Astronomy ,Single element ,010402 general chemistry ,Polarization (waves) ,01 natural sciences ,Spectral line ,0104 chemical sciences ,Computational physics ,[CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry ,Nonlinear optical ,0103 physical sciences ,Multiple beam ,[PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph] ,Physical and Theoretical Chemistry ,Spectroscopy ,Sum frequency generation spectroscopy - Abstract
International audience; We illustrate a technique by which heterodyne-detected sum-frequency generation spectroscopy is performed at multiple angles of incidence in order to decompose components of the second-order susceptibility tensor when all beams are polarized parallel to the plane of incidence. As an illustration we study the non-vibrationally resonant gold response. We benchmark our results by comparing with measurements obtained in a polarization scheme that isolates a single element of the susceptibility tensor. Our technique is particularly valuable in the case of metal substrates, where the surface selection rule often prevents spectra from being acquired in multiple beam polarizations.
- Published
- 2020
4. Determining the Orientation of Chemical Functional Groups on Metal Surfaces by a Combination of Homodyne and Heterodyne Nonlinear Vibrational Spectroscopy
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Wei-Chen Yang and Dennis K. Hore
- Subjects
Heterodyne ,Chemistry ,business.industry ,Phase (waves) ,Nonlinear optics ,Infrared spectroscopy ,02 engineering and technology ,Dielectric ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,Signal ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,General Energy ,Optics ,Molecule ,Physical and Theoretical Chemistry ,0210 nano-technology ,Spectroscopy ,business - Abstract
We illustrate how phase-sensitive sum-frequency generation spectroscopy may be used to determine the polar orientation of organic species on metals, where there is a significant electronic contribution to the second-order signal. It turns out that traditional direct heterodyne schemes, as would be applied to the same molecules on dielectric substrates, are challenging to use here as a result of the large resonant/nonresonant amplitude ratio that diminishes the phase contrast observed in tuning through the vibrational mode. This is demonstrated in a variety of experimental surfaces that illustrate all limiting cases. We propose a scheme that can overcome this challenge and thereby determine the chemical functional group orientation through a combination of the homodyne spectrum and some phase information from a heterodyne approach.
- Published
- 2017
5. Influence of Al/Si Codiffusion on Current Gain Deterioration in AlGaN/GaN Single Heterojunction Bipolar Transistors
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Cheng Wen Lin, Kuo-Liang Cheng, Wei-Chen Yang, K. Y. Chen, and Y. T. Tseng
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010302 applied physics ,Materials science ,Silicon ,business.industry ,Heterojunction bipolar transistor ,Doping ,Bipolar junction transistor ,Wide-bandgap semiconductor ,chemistry.chemical_element ,Gallium nitride ,Nanotechnology ,Heterojunction ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,chemistry ,0103 physical sciences ,Optoelectronics ,Electrical and Electronic Engineering ,0210 nano-technology ,business ,Common emitter - Abstract
AlGaN/GaN single heterojunction bipolar transistors (SHBTs) without using regrown emitter junction are demonstrated. Secondary ion mass spectroscopy analysis shows that a severe codiffusion of Al and Si exists in AlGaN/GaN heterostructures grown at 780 °C. The altered composition and doping profiles greatly degrade the common-emitter current gain of AlGaN/GaN HBTs to ≤0.8. A GaN spacer layer is inserted at the emitter-base junction to alleviate this problem. In an AlGaN/GaN HBT structure inserted with a 20 nm unintentionally doped GaN spacer layer, a current gain $\beta $ about 2 is achieved.
- Published
- 2016
6. Broadband models and their consequences on line shape analysis in vibrational sum-frequency spectroscopy
- Author
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Wei-Chen Yang and Dennis K. Hore
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Physics ,General Physics and Astronomy ,Resonance ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Spectral line ,0104 chemical sciences ,Computational physics ,Direct-conversion receiver ,Amplitude ,Broadband ,Physical and Theoretical Chemistry ,0210 nano-technology ,Spectroscopy ,Chemical function ,Shape analysis (digital geometry) - Abstract
Vibrational sum-frequency generation (SFG) spectroscopy can provide valuable qualitative and quantitative information about molecular species at surface and buried interfaces. For example, the resonance frequency of a particular chemical function group is revealing of the surface environment, especially when compared to what is observed in bulk IR absorption or Raman scattering spectra. Furthermore, the amplitude of the mode can be related to the molecular orientation, providing a detailed quantitative account of the surface structure. Each of these attributes, however, requires fitting the spectra to some vibrationally resonant line shape. This is particularly challenging when the modes of interest co-exist with broad resonance features, such as water O-H stretching. In this perspective, we examine the merits and consequences of different approaches to fitting homodyne SFG data. We illustrate that, while any model can provide a useful description of the data, no model can accurately and consistently provide even the relative phase deeply encoded in homodyne data without the use of additional information.
- Published
- 2018
7. Dispersity effects on phase behavior and structural evolution in ultrathin films of a deuterated polystyrene-block-poly(methyl methacrylate) diblock copolymer
- Author
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Chun Ming Wu, Jung Hong Chang, Jia Wen Hong, Ya Sen Sun, Yi Ming Wang, Yi Fang Chen, Andrew Nelson, Wei Chen Yang, and Yeo Wan Chiang
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Phase transition ,Nanostructure ,Materials science ,Polymers and Plastics ,Organic Chemistry ,Dispersity ,02 engineering and technology ,Substrate (electronics) ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Chemical engineering ,Transmission electron microscopy ,Phase (matter) ,Materials Chemistry ,Neutron reflectometry ,Thin film ,0210 nano-technology - Abstract
We report the unique phase behavior and structural transitions in thin films of a distorted network (DNW) nanostructure, which is an equilibrium phase contained in the bulk of a nearly-symmetric deuterated polystyrene-block-poly (methyl methacrylate), dPS-b-PMMA, block copolymer. The DNW is due to a broad dispersity for the PMMA block. Grazing incidence small-angle X-ray scattering, neutron reflectometry, atomic force microscopy and transmission electron microscopy techniques were used to characterize thermally-annealed dPS-b-PMMA ultrathin films with neutral boundaries at both the free surface and substrate interface. Brief thermal annealing imposed on the ultrathin films leads to perpendicular lamellae (L⊥). Upon increasing the duration of thermal annealing, the dPS-b-PMMA ultrathin films exhibit thickness dependence of phase transition kinetics and different irreversible routes of phase transition. As a result, the protracted thermal annealing of the thin films of various thicknesses produces either hexagonal arrays of perpendicular PMMA cylinders (HEX-C⊥) or disordered PMMA nanostructures (DIS). The phase transition routes and kinetics in ultrathin films suggest various possibilities to obtain diverse nanoscale patterns via thin film self-assembly.
- Published
- 2020
8. Mg incorporation in GaN grown by plasma-assisted molecular beam epitaxy at high temperatures
- Author
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Cheng Wen Lin, Wei-Chen Yang, Hsin-Ying Tseng, P.Y. Lee, Y.T. Tseng, and Keh-Yung Cheng
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010302 applied physics ,Electron mobility ,Materials science ,Analytical chemistry ,02 engineering and technology ,Plasma ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Flux ratio ,Highly sensitive ,Inorganic Chemistry ,Electrical resistivity and conductivity ,0103 physical sciences ,Materials Chemistry ,0210 nano-technology ,Beam (structure) ,Molecular beam epitaxy - Abstract
The influence of growth conditions on the incorporation and activation of Mg in GaN grown by plasma-assisted molecular beam epitaxy at high growth temperature (>700 °C) is presented. It is found that the highest Mg incorporation with optimized electrical properties is highly sensitive both to the Mg/Ga flux ratio and III/V flux ratio. A maximum Mg activation of ~5% can be achieved at a growth temperature of 750 °C. The lowest resistivity achieved is 0.56 Ω-cm which is associated with a high hole mobility of 6.42 cm 2 /V-s and a moderately high hole concentration of 1.7×10 18 cm −3 . Although the highest hole concentration achieved in a sample grown under a low III/V flux ratio and a high Mg/Ga flux ratio reaches 7.5×10 18 cm −3 , the mobility is suffered due to the formation of defects by the excess Mg. In addition, we show that modulated beam growth methods do not enhance Mg incorporation at high growth temperature in contrast to those grown at a low temperature of 500 °C (Appl. Phys. Lett. 93, 172112, Namkoong et al., 2008 [19]).
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- 2016
9. Design the GaN junction barrier schottky diodes with array p-type pillar
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Y. T. Tseng, Yu-Li Wang, Keh-Yung Norman Cheng, Shao-Yen Chiu, and Wei-Chen Yang
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010302 applied physics ,Materials science ,business.industry ,Schottky barrier ,020208 electrical & electronic engineering ,Pillar ,Schottky diode ,02 engineering and technology ,Metal–semiconductor junction ,01 natural sciences ,Electric field ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,Optoelectronics ,business ,Voltage ,Diode - Abstract
The performance of JBS (P, S) structure within threading dislocations-induced (GaN on PSS∼108cm−2) traps and in drift-diffusion simulations, including the critical electric field are studied. As the forward and reverse operation, the pillar-to-pillar of various diode lead to the lower turn-on voltage and high breakdown, respectively. Then, it is important to note that is not punch-through the drift layer to n+-GaN yet because that difference is attributed to whether the intrinsic or extrinsic C-dopants, results in the n−-type drift layer or p+-type with bias-dependent deletion region.
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- 2016
10. GaN Schottky diodes with single-crystal aluminum barriers grown by plasma-assisted molecular beam epitaxy
- Author
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P.Y. Lee, Wei-Chen Yang, K. C. Hsieh, Keh-Yung Cheng, Hsin-Ying Tseng, Kai-Yuan Cheng, Cheng-Wei Lin, and C.-H. Hsu
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010302 applied physics ,Materials science ,Physics and Astronomy (miscellaneous) ,business.industry ,Schottky barrier ,Wide-bandgap semiconductor ,Schottky diode ,02 engineering and technology ,Substrate (electronics) ,021001 nanoscience & nanotechnology ,Epitaxy ,01 natural sciences ,0103 physical sciences ,Optoelectronics ,0210 nano-technology ,business ,Single crystal ,Diode ,Molecular beam epitaxy - Abstract
GaN-based Schottky barrier diodes (SBDs) with single-crystal Al barriers grown by plasma-assisted molecular beam epitaxy are fabricated. Examined using in-situ reflection high-energy electron diffractions, ex-situ high-resolution x-ray diffractions, and high-resolution transmission electron microscopy, it is determined that epitaxial Al grows with its [111] axis coincident with the [0001] axis of the GaN substrate without rotation. In fabricated SBDs, a 0.2 V barrier height enhancement and 2 orders of magnitude reduction in leakage current are observed in single crystal Al/GaN SBDs compared to conventional thermal deposited Al/GaN SBDs. The strain induced piezoelectric field is determined to be the major source of the observed device performance enhancements.
- Published
- 2016
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