Browsing by Author "Hsu, S. Y."

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0.7 anomaly due to the Rashba interaction in a nonuniform electric field
(2009-01-01)
Hsiao, J. H.
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Liu, K. M.
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Hsu, S. Y.
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Hong, T. M.
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電子物理學系
We demonstrate that three conductance features, 0.5 and 0.7G(0) plateaus and a dip at 0.5G(0), observed in quantum point contacts (QPCs) can be consistently explained by the Rashba interaction in the nonuniform electric field created by the side gates along the transport direction. A quantity gamma is defined which depends on the extent of this nonuniformity and the electron density. A short QPC tends to have a small gamma. Only when gamma is large will the Rashba interaction produce a potential well deep enough to localize the electron. This provides the bound state that forms the Kondo resonance with the tunneling electrons. We propose to compare the medium/long QPC to small/large quantum dots, which are governed by the Kondo physics and the Coulomb blockade, respectively. The relation between 0.7 anomaly and the side-gate voltage, length of QPC, and temperature can all be determined to agree qualitatively with the experiments.
A dispatching rule for photolithography scheduling with an on-line rework strategy
(2006-07-01)
Sha, D. Y.
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Hsu, S. Y.
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Che, Z. H.
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Chen, C. H.
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工業工程與管理學系
Generally speaking, wafer fabrication factories define the photolithography area as the dispatching center of the entire factory. To establish a set of operative dispatching rules in the photolithography area while taking into consideration the rework of defective products would assist in coordinating and balancing the workload of the entire production line. Furthermore, it would help to enhance both the productivity and efficiency of the wafer fabrication, reduce the on-line WIP stock, shorten the production cycle time, and satisfy the requirements of customers regarding production due time and product quality. This research uses on-line rework as the basis for bringing the factor of reworking of a batch process into the dispatching rule for measurement. It then develops the dispatching rule (Rw-DR) which includes the rework strategy. In addition, this research focuses on the batch with high finished proportion in the photolithography area for finding a way to complete the manufacturing procedure faster, lighten the machine workload of the waiting line, and at the same time increase the output quantity. (c) 2006 Elsevier Ltd. All rights reserved.
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.
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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.
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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]
Carrier density dependent electric transport of serially connected two quantum point contacts
(2010-02-01)
Liu, K. M.
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Lin, H. I.
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Umansky, V.
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Hsu, S. Y.
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電子物理學系
We have measured the electric transport of double quantum point contacts in series at low temperatures. Two pairs of metal gates are placed longitudinally and sequentially with an edge-to-edge distance of 600 nm. They are used to form two quantum point contacts in a GaAs/Al(x)Ga(1-x)As heterostructure. Isolating from an insulating layer, a top gate is also fabricated on top of the quantum point contacts to modify the electron densities in the quantum point contacts and the two dimensional electron gas as well. The transport is characterized by the direct transmission probability T(d) which represents the portions of electrons travelling ballistically from one quantum point contact to the other. Our results show that the parameter T(d) decreases with decreasing carrier density. The transport is partially adiabatic in high 20 electron densities and transits to completely ohmic regimes in low densities. Because of the correlation between the coherence length and transmission probability, we attribute the result to the reduction of the coherence length and mean free path in the unconstricted electron gas between quantum point contacts. (C) 2010 Elsevier B.V. All rights reserved.
Diffusion of Co-Sputtered Metals as Bonding Materials for 3D Interconnects During Thermal Treatments
(2012-03-01)
Hsu, S. Y.
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Chen, H. Y.
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Chen, K. N.
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
Diffusion behaviors of co-sputtered metals during thermal treatments were investigated, where these co-sputtered metals can be used as bonding materials for 3D Interconnects. In this paper, we report the diffusion behaviors and discuss the diffusion mechanisms of co-sputtered metals before and after annealing. Atom and vacancy volume, vacancy formation energy, and activation energy are proposed to explain the diffusion direction and diffusion rate among different co-sputtered metals. Based on the excellent bonding performance of this method, Cu/metal co-sputtering bonding is considered as a potential candidate for advanced bonding technology.
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.
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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 impurity scattering on the linear and nonlinear conductances of quasi-one-dimensional disordered quantum wires by asymmetrically lateral confinement
(2010-10-06)
Liu, K. M.
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Juang, C. H.
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Umansky, V.
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Hsu, S. Y.
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電子物理學系
We have studied the linear conductance and source-drain bias spectroscopies of clean and disordered quantum wires (QWs) against thermal cycling and lateral shifting, which change the impurity configuration. Conductance quantization and the zero bias anomaly (ZBA) are robust in clean QWs. In contrast, disordered QWs show complexities in the ways of conductance resonance, peak splitting and trace crossing in source-drain bias spectroscopies. The experimental results and theoretical predictions are in congruence. Moreover, the resonant state arising from the impurities results in either a single peak or double-splitting peaks in the spectroscopies from the detailed impurity configurations. The resonant splitting peaks are found to influence the ZBA, indicating that a clean QW is crucial for investigating the intrinsic characteristics of the ZBA of QWs.
Effect of impurity scattering on the linear and nonlinear conductances of quasi-one-dimensional disordered quantum wires by asymmetrically lateral confinement
(2010-10-06)
Liu, K. M.
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Juang, C. H.
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Umansky, V.
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Hsu, S. Y.
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電子物理學系
We have studied the linear conductance and source-drain bias spectroscopies of clean and disordered quantum wires (QWs) against thermal cycling and lateral shifting, which change the impurity configuration. Conductance quantization and the zero bias anomaly (ZBA) are robust in clean QWs. In contrast, disordered QWs show complexities in the ways of conductance resonance, peak splitting and trace crossing in source-drain bias spectroscopies. The experimental results and theoretical predictions are in congruence. Moreover, the resonant state arising from the impurities results in either a single peak or double-splitting peaks in the spectroscopies from the detailed impurity configurations. The resonant splitting peaks are found to influence the ZBA, indicating that a clean QW is crucial for investigating the intrinsic characteristics of the ZBA of QWs.
Effect of scattering on zero-bias anomaly and conductance reduction in quasi-one-dimensional quantum wires
(2010-06-11)
Liu, K. M.
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Umansky, V.
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Hsu, S. Y.
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電子物理學系
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Department of Electrophysics
We present a systematic study on the zero-bias conductance peak and its dependences on the carrier density and structural geometry in quasi-one-dimensional quantum wires (QWs). This zero-bias anomaly (ZBA) is suppressed by either decreasing the carrier density or increasing the QW length. The differential conductance at zero bias decreases with increasing temperature in accordance with a thermal-activation model up to a well-defined cut-off temperature. We demonstrate that the activation energy, cut-off temperature, and width of the ZBA are correlated, and suggest that these features are controlled by electron scattering in QWs.
Effect of Surface Oxidation on the Magnetization Reversal of Cobalt Planar Wires
(2013-04-01)
Chiang, C. C.
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Ko, S.
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Hsu, S. Y.
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電子物理學系
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Department of Electrophysics
The influence of the antiferromagnetic layer of cobalt oxide on the magnetization reversal of a submicron cobalt planar wire was studied using the magneto-transport measurements. For pure Cobalt (Co) planar wires of width less than 1.2 mu m, length of 30 mu m, and thickness of 30 nm, the shape anisotropy dominates the magnetic behavior revealing all characteristics of a single domain structure. With oxidation, there is a thin layer of CoO on top of the Co layer and the exchange coupling between the CoO (antiferromagnet) and Co (ferromagnetic) layers may suppress the shape anisotropy induced single domain structure and the typical switching behavior of magnetization reversal. The magnetic configuration and magnetization reversal are determined by the competition of unidirectional anisotropy and exchange coupling constant.
Electrical Performances and Quality Investigations of Integrated Bonded Structures and TSVs for 3D Interconnects
(2012)
Chen, K. N.
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Chang, Y. J.
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Ko, C. T.
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Hsu, S. Y.
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Chen, H. Y.
Fabrication and low temperature thermoelectric properties of NaxCoO2 (x=0.68 and 0.75) epitaxial films by the reactive solid-phase epitaxy
(2007-02-05)
Chang, W. J.
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Hsieh, C. C.
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Chung, T. Y.
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Hsu, S. Y.
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Wu, K. H.
The authors have fabricated NaxCoO2 thin films via lateral diffusion of sodium into Co3O4 (111) epitaxial films (reactive solid-phase epitaxy [Ohta , Cryst. Growth Des. 5, 25 (2005)]). The environment of thermal diffusion is key to the control of the sodium content in thin films. From the results of x-ray diffraction and in-plane rho(ab), the epitaxial growth and the sodium contents of these films were identified. The thermoelectric measurements show a large thermoelectric power similar to that observed in single crystals. The quasiparticle scattering rate is found to approach zero at low temperatures, consistent with the small residual resistivity, indicating high quality of the NaxCoO2 thin films. (c) 2007 American Institute of Physics.
Fabrication and X-ray absorption NaxCoO2 spectroscopy in layered cobaltate thin films
(2007-03-01)
Chang, W. J.
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Lin, J.-Y.
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Chung, T. Y.
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Chen, J. M.
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Hsu, C.-H.
NaxCoO2 (x similar to 0.68) thin films were fabricated on sapphire (0 0 0 1) substrates via the lateral diffusion of sodium into Co3O4 (1 1 1) films, which were grown by pulsed-laser deposition. From the results of X-ray diffraction and in-plane resistivity rho(ab), the single phase and the metallic behaviors of these NaxCoO2 films can be identified. For the same sodium content x, rho(ab) is consistent with that of single crystals. In addition, the O 1s X-ray absorption near edge spectra of thin films are measured and compared with those of single crystals. (c) 2006 Elsevier B.V. All rights reserved.
Interface resistance and transparency in ferromagnet/superconductor Co/NbxTi1-x multilayers (x = 1, 0.6, and 0.4)
(2007-07-01)
Huang, S.-Y.
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Lee, S. F.
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Hsu, S. Y.
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Yao, Y. D.
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電子物理學系
The quantitative interface resistance between polycrystalline ferromagnetic Co and NbxTi1-x, with x=1, 0.6, and 0.4, is measured and analyzed at 4.2 K. Both the superconducting and normal states of NbxTi1-x, respectively, above and below the superconducting critical thickness, are studied with current flowing perpendicular to the interface. A one-band series-resistance model is used to analyze our data. The interface transparencies in terms of the ratio between interface resistance and various physical quantities are discussed.
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.
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Lin, L. K.
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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.
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Liang, J. J.
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Hsu, S. Y.
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Lin, L. K.
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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.
Magnetic vortex structures probed by magnetotransport in sub-micron permalloy disks
(2010)
Kuo, C. Y.
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Chung, T. Y.
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Hsu, S. Y.
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電子物理學系
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Department of Electrophysics
We have successfully used magneto-transport measurement to study magnetization reversal of domain structure in single sub-micron magnetic disks of various sizes, 300nm <= diameter <= 5 mu m and 36nm <= thickness <= 48nm. The magnetoresistance (MR) resulted from the anisotropic magnetoresistance effect can reveals the magnetization reversal of a single disk as confirmed by the magnetic force microscopic results. For a fixed thickness, the remanent domain state can transits from the multi-domain to vortex states by decreasing the disk diameter. Here, the nucleation and annihilation fields of vortex core are determined from disk's hysteretic MR and analytically described by the micromagnetic LLG calculation incorporated with the "rigid" vortex model developed by Guslienko et al. under the consideration of magnetostatic, exchange, and Zeeman energies
Magneto-transport flipping induced by surface oxidation in Co films
(2009)
Chung, T. Y.
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Hsu, S. Y.
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電子物理學系
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Department of Electrophysics
We have performed low temperature magnetoresistance (MR) and magnetization measurements for a series of thin Co films with different degrees of oxidation to investigate the role of surface oxidation on magnetic properties. For films with less oxidation, magneto-transport exhibits the typical anisotropic magnetoresistance behavior. However, magneto-transport flips completely in films with severe oxidation. The inverse MR is replaced by the normal MR when the applied magnetic field is a long the current. The normal MR is changed to the inverse MR when the applied magnetic field is perpendicular to the current. Since the disorder will enhance the spin-orbital interaction and electron-electron interaction in thin films, we suggest that both mechanisms may be responsible for the flipping in anisotropic MR induced by surface oxidation.
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.
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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.