Browsing by Author "Lin, Minn-Tsong"

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Atomic scale depletion region at one dimensional MoSe2-WSe2 heterointerface
(2018-12-10)
Chu, Yu-Hsun
;
Wang, Li-Hong
;
Lee, Shin-Ye
;
Chen, Hou-Ju
;
Yang, Po-Ya
Lateral heterojunctions based on two dimensional (2D) transition metal dichalcogenides (TMDCs) potentially realize monolayer devices exploiting 2D electronic structures and the functions introduced by the presence of 1D heterointerfaces. Electronic structures of a lateral MoSe2-WSe2 junction have been unveiled using scanning tunneling microscopy and spectroscopy. A smooth and narrow depletion region exists despite a defect-rich heterointerface deviating from the preferred zigzag orientations of the TMDC lattice. From the characteristics of the depletion region, a high carrier concentration and high internal electric fields are inferred, offering to benefit designs of lateral TMDC devices. Published by AIP Publishing.
Chiral Second-Harmonic Generation from Monolayer WS2/Aluminum Plasmonic Vortex Metalens
(2020-04-08)
Guo, Wan-Ping
;
Liang, Wei-Yun
;
Cheng, Chang-Wei
;
Wu, Wei-Lin
;
Wang, Yen-Ting
Two-dimensional spiral plasmonic structures have emerged as a versatile approach to generate near-field vortex fields with tunable topological charges. We demonstrate here a far-field approach to observe the chiral second-harmonic generation (SHG) at designated visible wavelengths from a single plasmonic vortex metalens. This metalens comprises an Archimedean spiral slit fabricated on atomically flat aluminum epitaxial film, which allows for precise tuning of plasmonic resonances and subsequent transfer of two-dimensional materials on top of the spiral slit. The nonlinear optical measurements show a giant SHG circular dichroism. Furthermore, we have achieved an enhanced chiral SHG conversion efficiency (about an order of magnitude greater than the bare aluminum lens) from monolayer tungsten disulfide (WS2)/aluminum metalens, which is designed at the C-exciton resonance of WS2. Since the C-exciton is not a valley exciton, the enhanced chiral SHG in this hybrid system originates from the plasmonic vortex field-enhanced SHG under the optical spin-orbit interaction.
Magnetic and Metal Binding Structural Analysis of Mn,Zn-Metallothionein-Green Fluorescence Fusion Protein
(2012-01-31)
Chen, Ting-Kai
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Lin, Yin-Chih
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Chen, Yu-Chen
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Chen, Yen-Lin
;
Tseng, Wei-Lun
Nano Approach Investigation of the Conduction Mechanism in Polyaniline Nanofibers
(2011-02-01)
Lin, Yen-Fu
;
Chen, Chien-Hsiang
;
Xie, Wen-Jia
;
Yang, Sheng-Hsiung
;
Hsu, Chain-Shu
A nanotechnological approach is applied to measurements of the electric field dependence of resistance under a high electric field while in low voltage. With this technique, the conduction mechanism on a mesoscopic scale is explored in a single, nonagglomerated nanofiber. Polyaniline nanofibers are prepared by vigorous mixing of aniline and oxidation agent ammonium persulfate in acid solution. They exhibit a uniform nanoscale morphology rather than agglomeration as that produced via conventional chemical oxidation. The as-synthesized polyaniline nanofibers are doped (dedoped) with a HCl acid (NH(3) base), and their temperature behaviors of resistances follow an exponential function with an exponent of T(-1/2). To measure the conduction mechanism in a single nanofiber, the dieiectrophoresis technique is implemented to position nanofibers on top of two electrodes with a nanogap of 100-600 nm, patterned by electron-beam lithography. After the devices are irradiated by electron beam to reduce contact resistances, their temperature behaviors and electric field dependences are unveiled. The experimental results agree well with the theoretical model of charging energy limited tunneling. Other theoretical models such as Efros-Shklovskii and Mott's one-dimensional hopping conduction are excluded after comparisons and arguments. Through fitting, the size of the conductive grain, separation distance between two grains, and charging energy per grain in a single polyaniline nanofiber are estimated to be about 4.9 nm, 2.8 nm, and 78 meV, respectively. The nanotechnological approach, where the nanogap and the dielectrophoresis technique are used for single nanofiber device fabrication, Is applied for determination of mesoscopic charge transport in a polyaniline conducting polymer.
Superconductivity-induced magnetoresistance suppression in hybrid superconductor/magnetic tunnel junctions
(2009-01-01)
Chang, Yin-Ming
;
Li, Kai-Shin
;
Chiang, Wen-Chung
;
Lin, Jiunn-Yuan
;
Lin, Minn-Tsong
Hybrid superconductor/magnetic tunnel junctions of Nb/CoFe/AlO/CoFe/NiFe have been implemented to investigate the impact of the superconducting Nb layer on the proximal ferromagnetic CoFe layer. A suppression of tunneling magnetoresistance effect is observed as the Nb layer undergoes the superconducting transition. This suppression is thought to be due primarily to the coupling of the magnetic inhomogeneity of CoFe to the superconductivity of Nb. The magnetic structure-vortex interactions interplay each other, inducing a complex domain evolution in the magnetization process and consequently degrading the junction's antiparallel magnetization alignment.
Ultralow Schottky Barriers in Hexagonal Boron Nitride-Encapsulated Monolayer WSe2 Tunnel Field-Effect Transistors
(2020-04-22)
Pande, Gaurav
;
Siao, Jyun-Yan
;
Chen, Wei-Liang
;
Lee, Chien-Ju
;
Sankar, Raman
To explore the potential of field-effect transistors (FETs) based on monolayers (MLs) of the two-dimensional semiconducting channel (SC) for spintronics, the two most important issues are to ensure the formation of variable low-resistive tunnel ferromagnetic contacts (FCs) and to preserve intrinsic properties of the SC during fabrication. Large Schottky barriers lead to the formation of high resistive contacts, and methods adopted to control the barriers often alter the intrinsic properties of the SC. This work aims at addressing both issues in fully encapsulated ML WSe2 FETs using bilayer hexagonal boron nitride (h-BN) as a tunnel barrier at the FC/SC interface. We investigate the electrical transport in ML WSe2 FETs with the current-in-plane geometry that yields hole mobilities of similar to 38.3 cm(2) V-1 s(-1) at 240 K and on/off ratios of the order of 10(7), limited by the contact regions. We have achieved an ultralow effective Schottky barrier (similar to 5.34 meV) with an encapsulated tunneling device as opposed to a nonencapsulated device in which the barrier heights are considerably higher. These observations provide an insight into the electrical behavior of the FC/h-BN/SC/h-BN heterostructures, and such control over the barrier heights opens up the possibilities for WSe2-based spintronic devices.