Alicia Serfaty

Errata: Properties of step-edge Pb-Si-Pb Josephson junctions

Journal of Low Temperature Physics, May 1, 1987

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Linear and sublinear photoresponse of CdS photodetector: A reevaluation

Journal of Physics and Chemistry of Solids, 1991

... Comparison between Fig. la and Ib shows excellent agreement between the experimentally obtain... more

A new method to resolve transient photoresponse involving the sum of exponential terms

Physics Letters, Jul 1, 1989

The analysis of a signal consisting of multi-exponential terms is a well known problem in examini... more The analysis of a signal consisting of multi-exponential terms is a well known problem in examining the transient behaviour of photoresponse. Here, a method is proposed to analyze such signals with the help of the fast Fourier transform technique, which permits one to determine time constants uniquely with high accuracy. The method was verified for a commercially available CdS photodetector.

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A Computer Assisted Study of Chaotic Behavior in Intrinsic Photoconductors

MRS Proceedings, 1992

ABSTRACTThe present work confirms thee possibility of chaotic behavior in intrinsic photoconducto... more

Detectivity of the photosensors: A reevaluation

International Journal of Infrared and Millimeter Waves, Sep 1, 1989

Important parameters of the photosensors such as Noise Equivalent Power (NEP) and detectivity dep... more Important parameters of the photosensors such as Noise Equivalent Power (NEP) and detectivity depend upon the magnitude of the signal to noise ratio. Recent improvements in the techniques of measurement indigitized form permit to process noise statistically with a suitable procedure and increase the detection capability more than expected from the conventional definition.

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Local stability regions in dynamics of photoconductors

Chaos Solitons & Fractals, Jul 1, 1996

The stability analysis for the set of non-linear differential equations involved in the kinetics ... more The stability analysis for the set of non-linear differential equations involved in the kinetics of the photoconductors has been carried out by examining the eigenvalues of the Jacobian matrix. We have assumed that the photoconductor is illuminated with high intensity radiation. It has been found that these eigenvalues critically depend upon the parameters of the traps and. for a certain set of values of the parameters, the system becomes unstable and reveals the possibility of chaos. We have determined the critical regions for different parameters where the system shows transitions from stable to unstable behavior.

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Detection of the onset of numerical chaotic instabilities by lyapunov exponents

Discrete Dynamics in Nature and Society, 2001

It is commonly found in the fixed-step numerical integration of nonlinear differential equations ... more It is commonly found in the fixed-step numerical integration of nonlinear differential equations that the size of the integration step is opposite related to the numerical stability of the scheme and to the speed of computation. We present a procedure that establishes a criterion to select the largest possible step size before the onset of chaotic numerical instabilities, based upon the observation that computational chaos does not occur in a smooth, continuous way, but rather abruptly, as detected by examining the largest Lyapunov exponent as a function of the step size. For completeness, examination of the bifurcation diagrams with the step reveals the complexity imposed by the algorithmic discretization, showing the robustness of a scheme to numerical instabilities, illustrated here for explicit and implicit Euler schemes. An example of numerical suppression of chaos is also provided.

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Fourier-transform analysis of multiexponential curves observed in photoconductivity studies

Physical review, Apr 15, 1990

A method is proposed to analyze multiexponential and delayed components in the relaxation curves ... more A method is proposed to analyze multiexponential and delayed components in the relaxation curves observed in photoconductivity processes. The amplitudes, time constants, and delayed time (escape time from the traps) have been determined from the real or imaginary parts of the fast Fourier transform of the recorded data. This technique permits us to analyze uniquely the complete form of the transient response without ambiguity, in contrast to numerical, graphical, or curvefitting approaches. The above method has general applicability in other fields dealing with multiexponential transient phenomena. On this basis, a commercially available CdS photodetector was examined and time constants were determined precisely. The obtained values are in close agreement with earlier reported values from other techniques.

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Detection of attractors and chaos in intrinsic photoconductors

Physical review, Feb 15, 1993

The set of nonlinear differential equations describing the intrinsic photoconductivity process is... more The set of nonlinear differential equations describing the intrinsic photoconductivity process is examined by numerical methods for realistic values of the parameters of the traps in the presence of high-intensity radiation. For a given set of initial conditions, the presence of a fixed-point attractor was observed. The position of the center of the attractor in phase space was determined by searching for a stable point of the nonlinear system of differential equations. The phase diagram also shows a Ro&Dot;ssler-like attractor. The power spectrum reveals that the system shifts from a Ro&Dot;ssler-like attractor to a fixed-point attractor in a chaotic manner. As expected, it is found that the system is very sensitive to the initial conditions.

Properties of step-edge Pb-Si-Pb Josephson junctions

Journal of Low Temperature Physics, Apr 1, 1986

A description is given of the properties and fabrication of a superconductor-semiconductor-superc... more A description is given of the properties and fabrication of a superconductor-semiconductor-superconductor Josephson device based on a novel step-edge technique. This technique allows for careful control of device lengths down to 100 nm. The fabricated devices exhibit high normal-state resistances and surprisingly strong Josephson coupling. The temperature dependence of the measured critical currents suggests that the coherence length in silicon

Properties of step-edge Pb-Si-Pb Josephson junctions

Journal of Low Temperature Physics, 1986

A description is given of the properties and fabrication of a superconductor-semiconductor-superc... more A description is given of the properties and fabrication of a superconductor-semiconductor-superconductor Josephson device based on a novel step-edge technique. This technique allows for careful control of device lengths down to 100 nm. The fabricated devices exhibit high normal-state resistances and surprisingly strong Josephson coupling. The temperature dependence of the measured critical currents suggests that the coherence length in silicon

Errata: Properties of step-edge Pb-Si-Pb Josephson junctions

Journal of Low Temperature Physics, 1987

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Fourier-transform analysis of multiexponential curves observed in photoconductivity studies

Physical Review B, 1990

A method is proposed to analyze multiexponential and delayed components in the relaxation curves ... more A method is proposed to analyze multiexponential and delayed components in the relaxation curves observed in photoconductivity processes. The amplitudes, time constants, and delayed time (escape time from the traps) have been determined from the real or imaginary parts of the fast Fourier transform of the recorded data. This technique permits us to analyze uniquely the complete form of the transient response without ambiguity, in contrast to numerical, graphical, or curvefitting approaches. The above method has general applicability in other fields dealing with multiexponential transient phenomena. On this basis, a commercially available CdS photodetector was examined and time constants were determined precisely. The obtained values are in close agreement with earlier reported values from other techniques.

Download

A Computer Assisted Study of Chaotic Behavior in Intrinsic Photoconductors

MRS Proceedings, 1992

ABSTRACTThe present work confirms thee possibility of chaotic behavior in intrinsic photoconducto... more

Linear and sublinear photoresponse of CdS photodetector: A reevaluation

Journal of Physics and Chemistry of Solids, 1991

... Comparison between Fig. la and Ib shows excellent agreement between the experimentally obtain... more

Detectivity of the photosensors: A reevaluation

International Journal of Infrared and Millimeter Waves, 1989

Important parameters of the photosensors such as Noise Equivalent Power (NEP) and detectivity dep... more Important parameters of the photosensors such as Noise Equivalent Power (NEP) and detectivity depend upon the magnitude of the signal to noise ratio. Recent improvements in the techniques of measurement indigitized form permit to process noise statistically with a suitable procedure and increase the detection capability more than expected from the conventional definition.

Download

Detection of the onset of numerical chaotic instabilities by lyapunov exponents

Discrete Dynamics in Nature and Society, 2001

It is commonly found in the fixed-step numerical integration of nonlinear differential equations ... more It is commonly found in the fixed-step numerical integration of nonlinear differential equations that the size of the integration step is opposite related to the numerical stability of the scheme and to the speed of computation. We present a procedure that establishes a criterion to select the largest possible step size before the onset of chaotic numerical instabilities, based upon the observation that computational chaos does not occur in a smooth, continuous way, but rather abruptly, as detected by examining the largest Lyapunov exponent as a function of the step size. For completeness, examination of the bifurcation diagrams with the step reveals the complexity imposed by the algorithmic discretization, showing the robustness of a scheme to numerical instabilities, illustrated here for explicit and implicit Euler schemes. An example of numerical suppression of chaos is also provided.

Download

Local stability regions in dynamics of photoconductors

Chaos, Solitons & Fractals, 1996

The stability analysis for the set of non-linear differential equations involved in the kinetics ... more The stability analysis for the set of non-linear differential equations involved in the kinetics of the photoconductors has been carried out by examining the eigenvalues of the Jacobian matrix. We have assumed that the photoconductor is illuminated with high intensity radiation. It has been found that these eigenvalues critically depend upon the parameters of the traps and. for a certain set of values of the parameters, the system becomes unstable and reveals the possibility of chaos. We have determined the critical regions for different parameters where the system shows transitions from stable to unstable behavior.

$Fig. 5. As the capture cross section for electrons is increased to c; = 1.5 x 10° sec”. the fraction of electrons that goes to the traps is reduced and. therefore, stability is expected.$

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A new method to resolve transient photoresponse involving the sum of exponential terms

Physics Letters A, 1989

The analysis of a signal consisting of multi-exponential terms is a well known problem in examini... more The analysis of a signal consisting of multi-exponential terms is a well known problem in examining the transient behaviour of photoresponse. Here, a method is proposed to analyze such signals with the help of the fast Fourier transform technique, which permits one to determine time constants uniquely with high accuracy. The method was verified for a commercially available CdS photodetector.

Download

Detection of attractors and chaos in intrinsic photoconductors

Physical Review B, 1993

The set of nonlinear differential equations describing the intrinsic photoconductivity process is... more The set of nonlinear differential equations describing the intrinsic photoconductivity process is examined by numerical methods for realistic values of the parameters of the traps in the presence of high-intensity radiation. For a given set of initial conditions, the presence of a fixed-point attractor was observed. The position of the center of the attractor in phase space was determined by searching for a stable point of the nonlinear system of differential equations. The phase diagram also shows a Ro&Dot;ssler-like attractor. The power spectrum reveals that the system shifts from a Ro&Dot;ssler-like attractor to a fixed-point attractor in a chaotic manner. As expected, it is found that the system is very sensitive to the initial conditions.

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