Browsing by Author "Huang, S. Y."

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Analysis of diffusive interface resistance for measurements with perpendicular current in Fe/Nb multilayers
(2006-04-15)
Huang, S. Y.
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Lee, S. F.
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Yu, C. Y.
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Hsu, S. Y.
;
Yao, Y. D.
In this study, we investigated the electron transport properties of interface between a ferromagnet and a superconductor with flowing current perpendicular to plan (CPP) at 4.2 K in Fe/Nb multilayers. The CPP resistance increased linearly with layer thickness and with bilayer number. We extracted the unit area resistance value of one pair of interface for superconducting and normal Fe/Nb by using a series resistor model. Hence, we can quantitatively analyze the interface resistance between Fe and Nb in the diffusive regime. (C) 2006 American Institute of Physics.
Analysis of the proximity effect and the interface transparency with perpendicular current in Ni/Nb system
(2009-04-01)
Huang, S. Y.
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Chiu, Y. C.
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Liang, J. J.
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Lin, L. K.
;
Tsai, T. C.
We quantitatively study the interface resistance in Ni/Nb multilayers fabricated by sputtering system. For a fixed Ni layer thickness in Ni/Nb/Ni trilayers, the superconducting temperature T(c) decreases with decreasing Nb thickness. By analyzing the data with the proximity effect, the critical thickness below which superconductivity vanished was deduced. From current perpendicular to plane (CPP) measurement interpreted with a one-band series-resistor model, we obtained the CPP resistivities of Nb and Ni and the unit area resistances of 4.2 +/- 0.2 and 1.5 +/- 0.4 f Omega m(2) for superconducting and normal Ni/ Nb interfaces. The transparency parameter is directly calculated in terms of interface resistance. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3073657]
Correlated Electric Fluctuations in GaN Nanowire Devices
(2009-02-01)
Li, L. C.
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Huang, S. Y.
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Wei, J. A.
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Suen, Y. W.
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Lee, M. W.
We report an experimental study on the correlation spectrums between different sections of a multicontact GaN nanowire device. Our results indicate that there exists a negative correlation between the voltage fluctuations of adjacent sections of the nanowire separated by a metal contact in the transition region between the low-frequency 1/f noise and the high-frequency white thermal noise. We suggest that this correlation is caused by the voltage fluctuation under the contact area.
Demonstration of edge roughness effect on the magnetization reversal of spin valve submicron wires
(2010-07-12)
Chiang, T. W.
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Chang, L. J.
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Yu, C.
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Huang, S. Y.
;
Chen, D. C.
We prepared submicron wide trilayer spin valve wires designed with periodic "spikes" as artificial roughness. The height and the pitch of the spikes were varied systematically. No obvious dependence was found between the roughness and the domain wall velocity when the spikes were smaller than a threshold of 30 nm for NiFe. The average velocity was slowed down when the height of the spikes were larger than the threshold. In-plane transverse magnetic fields help to reduce the critical current density for current induced domain-wall motion. Our results could be attributed to the space modulation of the local magnetization. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3463459]
Dimensional crossover and flux pinning of decoupled Cu(50)Ni(50)/Nb multilayers
(2008-04-01)
Huang, S. Y.
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Liang, J. -J.
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Tsai, T. C.
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Lin, L. K.
;
Lin, M. S.
The behaviors of superconducting transition temperature T(c) and upper critical field H(c2) as a function of different superconductor thicknesses have been investigated in Cu(50)Ni(50)/Nb trilayers and multilayers. We deduced superconductor critical thickness, below which superconductivity vanishes, by analyzing the data in terms of proximity theory. The temperature dependence of H(c2) measurement reveals the spatial dimensional crossover and the flux pinning mechanism in the superconductor. A strong pair-breaking effect was observed in the weak ferromagnetic Cu(50)Ni(50) layers from both measurements. We attribute our observation to the high interface transparency between Cu(50)Ni(50) and Nb. (C) 2008 American Institute of Physics.
Effect of compressive stress on nickel-induced lateral crystallization of amorphous silicon thin films
(2012-01-31)
Huang, S. Y.
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Lin, H. L.
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Chao, C. G.
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Liu, T. F.
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材料科學與工程學系
The present study describes a method enabling the metal-induced lateral crystallization (MILC) of amorphous silicon (a-Si) films. Glass substrates coated with a-Si films were contacted with ground nickel sheets under compressive stresses ranging from 3.7 to 265.8 MPa at 550 degrees C for 1 h. Subsequently, the nickel sheet and stress were removed and the specimens were annealed at 550 degrees C for 1 to 4 h. The experimental results indicate that the extent of MILC decreased when the preliminary compressive stress was increased, while all specimens exhibited the same rate of lateral crystallization during annealing. The present study indicates that, by applying an appropriate compressive stress (similar to 4 MPa), an effective method to reduce the residual Ni content in polycrystalline silicon (poly-Si) can be obtained. (C) 2011 Published by Elsevier B.V.
Investigation of Cu(0.5)Ni(0.5)/Nb interface transparency by using current-perpendicular-to-plane measurement
(2011-01-01)
Huang, S. Y.
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Liang, J. J.
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Hsu, S. Y.
;
Lin, L. K.
;
Tsai, T. C.
A direct determination of the interfacial transparency on the basis of current-perpendicular-to-plane (CPP) resistances for Cu(0.5)Ni(0.5)/Nb layered system is presented. This particular realization has substantial significance for understanding the interfacial transport in such heterostructures. The unexpected large critical thickness for this weak ferromagnetic containing system can be attributed to the strong pair-breaking effect as a result of the high interfacial transparency. Besides, the strong pair-breaking also plays a decisive role in the occurrence of the dimensionality crossover of the temperature dependent upper critical magnetic field.
Investigation of Cu0.5Ni0.5/Nb interface transparency by using current-perpendicular-to-plane measurement
(2011-01-01)
Huang, S. Y.
;
Liang, J. J.
;
Hsu, S. Y.
;
Lin, L. K.
;
Tsai, T. C.
A direct determination of the interfacial transparency on the basis of current-perpendicular-to-plane (CPP) resistances for Cu0.5Ni0.5/Nb layered system is presented. This particular realization has substantial significance for understanding the interfacial transport in such heterostructures. The unexpected large critical thickness for this weak ferromagnetic containing system can be attributed to the strong pair-breaking effect as a result of the high interfacial transparency. Besides, the strong pair-breaking also plays a decisive role in the occurrence of the dimensionality crossover of the temperature dependent upper critical magnetic field.
Optical fine structures of highly quantized InGaAs/GaAs self-assembled quantum dots
(2010-06-30)
Ramirez, H. Y.
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Lin, C. H.
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Chao, C. C.
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Hsu, Y.
;
You, W. T.
A theoretical model for the electron-hole exchange interaction in three-dimensionally (3D) confining semiconductor nanostructures is presented to explain the observed decreasing tendency of the fine-structure splittings (FSSs) of small InGaAs/GaAs self-assembled quantum dots (QDs) with increasing the emission energies. The experimentally revealed FSS reduction is shown to be highly associated with the significant 3D spreading of electronic orbitals and reduced overlap of electron and hole wave functions in small and/or Ga-diffused QDs. The combination of quantum size and Ga-diffusion effects substantially reduces the averaged e-h exchange interaction and leads to the reduced FSSs in the regime of high emission energy.
Properties of superconductivity for decoupled ferromagnet/superconductor trilayers and multilayers in Fe/Nb system
(2006-09-01)
Huang, S. Y.
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Lee, S. F.
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Liang, Jun-Jih
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Yu, C. Y.
;
You, K. L.
The transition temperature T(c) and upper critical field H(c2) of sputtered Fe/Nb trilayers and multilayers have been determined by measurement of electrical resistivity. For a fixed Fe layer thickness, T(c) decreases with decreasing Nb thickness up to a critical thickness d(Nb)(crit) approximate to 34 nm below which superconductivity vanishes. When the superconducting layers are thin (d(Nb) < 140 nm) and decoupled by pair breaking in the ferromagnetic layers, the parallel critical field exhibits nonlinear temperature dependence, revealing a change in the superconducting dimensionality. The strong decrease of T(c) with decreasing Nb thickness as well as the temperature dependence of H(c2) can be well described by theoretical model. (C) 2006 Elsevier B. V. All rights reserved.
Singlet-triplet transitions in highly correlated nanowire quantum dots
(2010-02-01)
Chen, Y. T.
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Chao, C. C.
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Huang, S. Y.
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Tang, C. S.
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Cheng, S. J.
We consider a quantum dot embedded in a three-dimensional nanowire with tunable aspect ratio a. A configuration interaction theory is developed to calculate the energy spectra of the finite ID quantum dot systems charged with two electrons in the presence of magnetic fields B along the wire axis. Fruitful singlet-triplet transition behaviors are revealed and explained in terms of the competing exchange interaction, correlation interaction, and spin-Zeeman energy. In the high aspect ratio regime, the singlet-triplet transitions are shown designable by tuning the parameters a and B. The transition also manifest the highly correlated nature of long nanowire quantum dots. (C) 2009 Elsevier B.V. All rights reserved.
Temperature dependence of the excess noise of a GaN nanowire device
(2007)
Li, L. C.
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Huang, S. Y.
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Wei, J. A.
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Suen, Y. W.
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Lee, M. W.
We report on the study of the low-frequency excess noise of a GaN nanowire (NW) device from room temperature to 135 K. A Lorentzian noise is found to be embedded in the 1/f noise background, and becomes more significant as the bias current increases or the temperature decreases. The temperature dependance of the associated characteristic time, extracted from the spectrum, shows two thermally activated regions with different activation energies, which originate from different carrier-trapping levels in the NW device. The temperature dependence of the 1/f noise is difficult to unveil due to the presence of the strong Lorentzian noise.