Browsing by Author "Liang, C. T."

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Effect of nitrogen contents on the temperature dependence of photoluminescence in InGaAsN/GaAs single quantum wells
(2006-07-01)
Lai, Fang-I
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Kuo, S. Y.
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Wang, J. S.
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Kuo, H. C.
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Wang, S. C.
A series of InGaAsN/GaAs single-quantum wells (SQWs) with N contents varied from 0% to 5.3% were grown by molecular-beam epitaxy using a solid As and a nitrogen plasma sources. The impact of nitrogen concentration on the optical properties, as determined by the temperature dependence of photoluminescence (PL), of a 6 nm SQW was investigated. In the low-temperature region, a pronounced temperature-dependent S-shaped peak position was observed in PL spectra while increasing the nitrogen concentration. Quenching behavior reveals that the defect-related nonradiative processes might be enhanced in the highly nitrogen incorporated samples and thus influence the recombination dynamics. In addition, the evolution of the peak position of the InGaAsN/GaAs samples was in agreement with the empirical Varshni model in the high-temperature region. A significant reduction in the temperature dependence of the emission peak position is analyzed as well, and further confirms the prediction of proposed band anticrossing model of the electronic structure of III-N-V alloys. (c) 2006 American Vacuum Society.
Effect of the electromagnetic environment on the dynamics of charge and phase particles in one-dimensional arrays of small Josephson junctions
(2011-11-01)
Ho, I. L.
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Kuo, W.
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Lin, S. D.
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Lee, C. P.
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Liang, C. T.
The effect of the electromagnetic environment on the dynamics of quasi-particles, Cooper pairs and phase particles in one-dimensional arrays of small Josephson junctions is investigated experimentally and theoretically. It is found that the environment enhances the phase ordering and thus suppresses quasi-particle tunneling at high temperature and localization of Cooper pairs at low temperature. The dynamics is studied in the context of phase-charge duality, and the experimental results are quantitatively analyzed in both charge-ordered and phase-ordered regimes. Based on these analyses, a low-temperature phase diagram as well as a finite-temperature crossover phase diagram are constructed and compared to the experimental diagrams. Copyright (C) EPLA, 2011
Microwave-induced DC currents in mesoscopic structures
(2010-02-01)
Li, L. C.
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Sung, Y. T.
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Chang, C. W.
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Suen, Y. W.
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Chen, K. Y.
We report the power (P) dependence of microwave (MW)-induced current (I(ph)) of a 1-mu m sized mesoscopic structure fabricated from two-dimensional electron gas in the GaAs/AlGaAs heterostructure at temperature of 1.4 K. MW signals were fed onto the sample through a loop antenna nearby and I(ph) is measured from a pair of ohmic contacts. We found that I(ph) is proportional to P at low-P limit; this dependence has been predicted for diffusion-limited electron transport in mesoscopic systems. By contrast, for large P. the dependence is extremely non-monotonous and complicated; even though its physical origin is still not clear so far, our data suggest it is related to the scattering processes from boundaries and impurities in the mesoscopic structure. We also investigated the symmetry properties against reversal of magnetic field (B) and found that the field-symmetric part of I(ph)(B) is consistent with the variation of magnetoresistance; there exists also an anti-symmetric part, which should be related to time-reversal-symmetry-breaking scattering mechanisms in the channel. (C) 2009 Elsevier B.V. All rights reserved.
Nonadditive interactions in protein folding: The Zipper model of cytochrome c
(2007-08-01)
Morozov, A. N.
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Shiu, Y. J.
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Liang, C. T.
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Tsai, M. Y.
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Lin, S. H.
Hydrogen exchange experiments (Krishna et al. in J. Mol. Biol. 359:1410, 2006) reveal that folding-unfolding of cytochrome c occurs along a defined pathway in a sequential, stepwise manner. The simplified zipper-like model involving nonadditive coupling is proposed to describe the classical "on pathway" folding-unfolding behavior of cytochrome c. Using free energy factors extracted from HX experiments, the model can predict and explain cytochrome c behavior in spectroscopy studies looking at folding equilibria and kinetics. The implications of the proposed model are discussed for such problems as classical pathway vs. energy landscape conceptions, structure and function of a native fold, and interplay of secondary and tertiary interactions.