Browsing by Author "GOU, YS"

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A COMMENT ON THE CHAOTIC BEHAVIOR OF VANDERPOL EQUATIONS WITH AN EXTERNAL PERIODIC EXCITATION
(1989-02-01)
STEEB, WH
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HUANG, JC
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GOU, YS
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電子物理學系
;
電控工程研究所
A SIMPLE EXPERIMENT OF SIMULATING OPTICAL BISTABILITY WITH AN OSCILLOSCOPE AND PHOTODIODES
(1991-12-01)
WANG, CS
;
LAU, CS
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SHY, JT
;
GOU, YS
;
電子物理學系
This paper presents a novel and simple hybrid optical bistable system which is composed of an oscilloscope and photodiodes. It allows us to easily control its parameters, including transmission function, feedback amplification, and time of delay feedback. Here, we will present the features of bistability, multistability and self-oscillation in this system and also the dynamical behaviors induced by the effect of the delay in the feedback loop of this optical bistable system.
A SIMPLE EXPERIMENT OF SIMULATING OPTICAL FLIP-FLOP OPERATOR WITH 2 OSCILLOSCOPES AND PHOTODIODES
(1993-06-01)
WANG, CS
;
CHEN, NP
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SHY, JT
;
GOU, YS
;
光電工程學系
A coupled hybrid optical bistable device composed of two oscilloscopes and two photodiode detectors has been constructed. This device is used to experimentally simulate the basic feature of the flip-flop operator proposed by Otsuka [Opt. Lett. 14 (1989) 72]. Most importantly, it allows us to model the system easily, and hence the condition of an occurrence of the flip-flop operation is accordingly predicted by the linear stability analysis. Furthermore, the influences of symmetry property of the optical system upon the flip-flop operation have been discussed as well.
BIFURCATION STRUCTURE OF THE DUFFING OSCILLATOR WITH ASYMMETRICAL POTENTIAL WELL
(1989-03-27)
HUANG, JC
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KAO, YH
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WANG, CS
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GOU, YS
;
電子物理學系
CRITICAL-CURRENT ANISOTROPY AND FLUX-PINNING IN YBCO(001) AND YBCO(110) SUPERCONDUCTING THIN-FILMS PREPARED BY KRF PULSED-LASER ABLATION
(1993)
JUANG, JY
;
WU, KH
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WANG, SJ
;
LAI, TC
;
KAO, RT
CRUCIAL FORMULA FOR DETERMINATION OF THE OCCURRENCE OF THE NONCHAOTIC STATES IN RF-BIASED NONLINEAR OSCILLATORS
(1995-06-01)
YANG, TH
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WANG, CS
;
HUANG, JC
;
GOU, YS
;
電子物理學系
EFFECT OF SN ON THE SUPERCONDUCTIVITY OF THE DYBA2CU3O7-DELTA SYSTEM
(1989-12-01)
WANG, C
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CHEN, LT
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CHANG, HL
;
CHU, ML
;
HSU, FW
EFFECTS OF ANNEALING CONDITIONS ON THE PHASE-STABILITY AND SUPERCONDUCTING PROPERTIES OF DC SPUTTERING TLBACACUO THIN-FILMS
(1993-12-01)
LIN, HC
;
LI, MH
;
LI, JJ
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JANG, FI
;
FU, CM
We have studied the influence of heat treatment on the properties of the superconducting transition and critical current on the TiBaCaCuO thin films prepared by DC sputtering. The superconducting transition temperature is increasing as the maximum annealing temperature is raised. The XRD analysis reveals the evolution of the major phase of the films from 2212 phase to 2223 phase, when the films were annealed at maximum temperature varied from 895-degrees-C to 922-degrees-C. The surface morphology of the sample reveals the formation of the intergrowth of grains by partial melting, which may associated with the evolution of cntical current for the annealed films.
EFFECTS OF MAGNETIC-FIELD AND TEMPERATURE ON THE CRITICAL CURRENT HYSTERESIS IN TL-CA-BA-CU-O THIN-FILMS
(1990-11-01)
CHANG, HL
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JUANG, JY
;
LIOU, SH
;
UEN, TM
;
GOU, YS
EFFECTS OF SUBSTRATE TREATMENTS ON THE GROWTH OF YBCO SUPERCONDUCTING THIN-FILMS ON MGO BY PULSED-LASER ABLATION
(1993-12-01)
WU, KH
;
LI, MH
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JUANG, JY
;
UEN, TM
;
GOU, YS
Different treatments on single crystalline MgO(100) substrates have been performed to study the effects of the substrate conditions on the growth mechanisms and superconducting properties of YBCO thin films deposited in-situ by pulsed laser ablation process. The nucleation and growth of YBCO thin films on these substrates during deposition have been studied by using the in-situ resistance measurement method. The characteristics of as-deposited films have also been investigated by X-ray diffraction analysis (XRD), temperature dependent resitivity measurement (R - T), temperature dependent critical current density measurement (J(c) - T), scanning electron mircoscopy (SEM), and scanning tunneling mircoscopy (STM). It has been found that, while the zero-resistance transition temperature (T(co)) and the overall crystallographic orientation of the films are only affected slightly, the surface morphology and grain structure of the films have shown strong dependencies on the substrate conditions. Recognizing that for YBCO grown on MgO, due to the large lattice mismatch between the film and substrate, the film growth is semicoherent in nature, the observed results are consistently explained by attributing to the interplays between nucleation and grain coalescence processes. The dramatic differences in superconducting transport properties exhibited by films obtained with the conditions studied are also reported to reinforce the arguments proposed.
EFFECTS OF ZRO2 ON THE TEXTURING AND PROPERTIES OF MELT-PROCESSED Y1BA2CU3O7-DELTA
(1994-04-25)
JUANG, JY
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WU, CL
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WANG, SJ
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CHU, ML
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WU, KH
The addition of ZrO2 is found to be very effective as the nucleation sites to promote the oriented growth of Y1Ba2Cu3O7-delta (YBCO) during peritectic solidification. Extended regions of well-textured YBCO grains with superior superconducting properties of the YBCO bulk are readily obtained by a single-step melt process at much lower process temperatures. At 77 K, the platelike Josephson weak-link behaviors observed in pure melt-processed YBCO have been effectively eliminated, indicating that the coherency between the spherulitic superconducting YBCO grains may have been greatly improved by ZrO2 additions.
ENHANCEMENT OF CRITICAL-CURRENT AND MAGNETIC-FIELD IN A DEFECTED JOSEPHSON TUNNELING JUNCTION
(1995-04-01)
CHOW, TC
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CHOU, H
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LAI, HG
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LIU, CC
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GOU, YS
A Josephson junction with a length of 10 times the Josephson penetration depth (lambda(J)) and a defect size of 0.5 lambda(J) to 2 lambda(J) in different positions has been studied by a mechanical simulation. It was found that the defect modulated the current distribution tremendously when it was near the edge of the junction. A surprising enhancement of the critical current under the field was observed when the defect was located at 0.5 lambda(J) and had a size from 0.5 lambda(J) to 2 lambda(J), which was much larger than the conventional pinning size: the coherent length xi. This effect could be attributed to a self-field, which was either generated by the current itself or by the applied magnetic field, penetrating into the defect smoothly and being pinned at the defect. A repulsive interaction between the self-field and the external field kept any further flux from abruptly penetrating into the junction. The increment in the critical current under the applied field was up to 125% of the original defect-free one. By fitting two defects of the same size of 2 lambda(J) and positioning them at 0.5 lambda(J) to both edges of the junction, the zero field critical current and the critical magnetic field were enhanced up to 150% of a defect-free junction.
ENHANCEMENT OF CRITICAL-CURRENT DENSITY IN DIRECT-CURRENT-SPUTTERED TLBA2CA2CU3O9-/+DELTA SUPERCONDUCTING THIN-FILMS
(1995-02-13)
JUANG, JY
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HORNG, JH
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CHEN, SP
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FU, CM
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WU, KH
FABRICATION AND PROPERTIES OF DC-SPUTTERED TL-1223 SUPERCONDUCTING THIN-FILMS
(1995-06-01)
JUANG, JY
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HORNG, JH
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LIN, HC
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WANG, SJ
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FU, CM
A multi-step deposition and post annealing scheme has been developed for preparing nearly single phase, c-axis oriented TlBa2Ca2Cu3O9 (Tl-1223) superconducting thin films by dc-sputtering. The effects of the compensates used during post annealing on final phase formation suggest the crucial role played by thermodynamic conditions and further validates the viability of the present process scheme. In particular, films obtained by the present process have shown, for the first time in this system, a critical current density (Jc) above 10(6) A/cm(2) at 17 K with a zero- resistance transition temperature (Tco) above 110 K. The results are attributed to the improvement of film morphology, specifically a decreased density of weak-linking.
FLUX LINE DYNAMICS CROSSOVER IN THE TL-BA-CA-CU-O THIN-FILM
(1990-11-01)
WANG, CY
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CHANG, HL
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CHU, ML
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JUANG, JY
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GOU, YS
By extending the observation of the current-voltage characteristics to a much higher dissipative state, the flux-line motion experiences at least two stages of crossover, namely, from glassy hopping to creep-dominating, and finally an abrupt transition into the flow regime.
GROWTH AND PROPERTIES OF SUBMILLIMETER SINGLE GRAIN TL2BA2CA2CU3O10+X SUPERCONDUCTING THIN-FILMS
(1995-10-02)
LIN, HC
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UEN, TM
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LIU, CK
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JUANG, JY
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WU, KH
Distinct crystalline superconducting grains of Tl2Ba2Ca2Cu3O10+x(Tl-2223) with sizes up to 150 mu mx150 mu mX1 mu m were prepared by a single target dc-sputtering process followed by proper postannealing at temperatures around 910 degrees C. A reactive ion etching process was developed to pattern an similar to 10 mu m wide bridge with four contact leads directly on a single grain to study its superconducting transport properties. The etching process was found to have only minimal effect on the superconducting transition temperature T-c, which was typically around 110 K. Grains grown on MgO(100) and LaAlO3(100) substrates, although, displaying somewhat different in-plane orientations, all had critical current densities J(c), well above 10(6) A/cm2 at 77 K. The existence of only one grain boundary, however, can reduce the J(c) by orders of magnitude. (C) 1995 American Institute of Physics.
GROWTH AND PROPERTIES OF SUBMILLIMETER SINGLE GRAIN TL2BA2CA2CU3O10+X SUPERCONDUCTING THIN-FILMS
(1995-10-02)
LIN, HC
;
UEN, TM
;
LIU, CK
;
JUANG, JY
;
WU, KH
Distinct crystalline superconducting grains of Tl2Ba2Ca2Cu3O10+x(Tl-2223) with sizes up to 150 mu mx150 mu mX1 mu m were prepared by a single target dc-sputtering process followed by proper postannealing at temperatures around 910 degrees C. A reactive ion etching process was developed to pattern an similar to 10 mu m wide bridge with four contact leads directly on a single grain to study its superconducting transport properties. The etching process was found to have only minimal effect on the superconducting transition temperature T-c, which was typically around 110 K. Grains grown on MgO(100) and LaAlO3(100) substrates, although, displaying somewhat different in-plane orientations, all had critical current densities J(c), well above 10(6) A/cm2 at 77 K. The existence of only one grain boundary, however, can reduce the J(c) by orders of magnitude. (C) 1995 American Institute of Physics.
GROWTH OF PULSED-LASER DEPOSITED YBCO THIN-FILMS ON YSZ AND YSZ/SI SUBSTRATES
(1994-02-01)
JUANG, JY
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KAO, RT
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HSIEH, MC
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LI, MH
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CHU, ML
The growth mechanism of superconducting YBCO thin films deposited in - situ on both single crystalline YSZ and YSZ-buffered Si substrates as revealed by scanning tunneling microscopy (STM) are found to be very different. The results are attributed to the initial surface condition of the substrates.
INSITU DEPOSITION OF SUPERCONDUCTING YBCO FILMS ON SI WITH CERAMIC BUFFER LAYERS
(1993-03-01)
JUANG, JY
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WU, KH
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LAI, TC
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LEE, MH
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HSEIH, MC
Systematic studies on the optimization of depositing superconducting YBCO thin films on Si substrates with YSZ buffer layers by pulsed laser ablation have been carried out. Nearly c-axis oriented YBCO films with T(co) almost-equal-to 85 K were obtained routinely on Si(100) substrates with in-situ deposition of YSZ layers on top. Preliminary measurements on the critical current density Jc of these films showed Jc > 2.0 x 10(4) A/cm2 at 77K and Jc > 1.4 x 10(6) A/CM2 at 20K. The significant improvements on Jc are attributed to the great reduction of microcracks and the crystallinity of YSZ layer, achieved by the in-situ annealing of the buffer layer prior to the YBCO deposition. The effects of oxygen partial pressure and substrate temperature during YSZ deposition on the crystallinity of YSZ layer as well as on the quality of subsequently deposited YBCO films will be discussed. In our most recent attempt the microcracks has been sucessfully eliminated by a process combining the in-situ annealing and slow cooling process.
INSITU GROWTH OF Y1BA2CU3O7-X SUPERCONDUCTING THIN-FILMS USING A PULSED NEODYMIUM YTTRIUM-ALUMINUM-GARNET LASER WITH CO2-LASER HEATED SUBSTRATES
(1991-03-11)
WU, KH
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LEE, CL
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JUANG, JY
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UEN, TM
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GOU, YS
By replacing the resistive heater with a CO2 laser to heat the substrates together with concentered oxygen stream blowing onto the substrate during deposition, high quality Y1Ba2Cu3O7-x thin films with nearly perfect c-axis orientation and T(c0) = 87 K were grown in situ without subsequent slow cooling in oxygen atmosphere or any further heat treatment. The rapid quenching, from typically 600-degrees-C to room temperature in less than 50 s of the as-deposited films, excludes the possibility of further oxygen incorporation during the cooling process and indicates that the in situ growth may have completed during deposition under proper deposition conditions.