Hysteretic Current-voltage Research Articles

Modeling current-voltage and hysteretic current-voltage characteristics with two resonant tunneling diodes connected in series

The current-voltage ( I- V) and extrinsic hysteresis phenomena in a series combination of two resonant tunneling diodes with identical and different electrical parameters are analyzed and simulated. The derived I- V characteristic of the series circuit can be applied to the design and estimation of multipeak I- V characteristic before the circuit accomplishment. Some equations are derived to facilitate the circuit design.

Numerical Investigation and Model Approximation for the Hysteretic Current-Voltage Characteristics of Josephson Junctions with Nonlinear Quasiparticle Resistance

We present a model analysis for the current-voltage (I-V) characteristics of Josephson junctions having superconductor-insulator-superconductor (SIS) structure. The numerical result for the V m value, which is the product of the maximum supercurrent and the observed subgap resistance, shows a marked decrease with increasing junction critical current density (J c). The marked decrease is independent of leak current. Increasing J c reduces the junction capacitance C J and enlarges the amplitude of the junction voltage oscillation. Nonlinearity of the quasiparticle resistance restricts the voltage oscillation amplitude to the gap voltage, which results in the rapid decrease of the V m value. In this paper, we introduce a sinusoidal oscillation model for the junction voltage, and derive the approximated expressions for the V m value. The model approximation results agree well with the numerical results.

Properties of cadmium sulphide films grown by single-source metalorganic chemical vapour deposition with dithiocarbamate precursors

CdS films were grown by MOCVD using dialkyldithiocarbamate precursors. A novel precursor Cd(S 2CNMe nBu) 2, more volatile than the simpler diethyldithiocarbamate was employed in most growth experiments, much earlier work being re-investigated in this study. CdS films were characterised by optical spectrophotometry, thickness determinations, X-ray diffraction, scanning electron microscopy, and electrical measurements. Both precursors gave similar results in film growth on glass substrates over 2 h at 450 and 500°C. Films deposited on glass at 500°C have mean thicknesses in the range 150–700 nm, columnar microstructures, and consist of hexagonal CdS with very pronounced, uniaxial (0001)-orientation. Electrical properties are consistent with trap-dominated behaviour, as evidenced by small photo-induced conductivity enhancements and hysteretic current-voltage characteristics. Typical resistivities at 40°C are ∼ 4 × 10 4 Ω · cm in the dark and ∼ 6 × 10 3 Ω · cm under illumination. Epitaxial CdS film growth on InP substrates was examined, using Cd(S 2CNMe nBu) 2 as the precursor. A film grown on InP (111)P at 500°C was characterised using a three-axis X-ray diffractometer. These measurements indicated triaxial orientation described by the relationships CdS (0001)‖InP (111) and CdS [101̄0]‖InP [112̄].

Spatially resolved observation of the resistive transition in superconducting wire networks

We obtained spatially resolved images of the resistive transition of current-biased two-dimensional Nb wire networks in zero external magnetic field by applying low-temperature scanning electron microscopy. At temperatures well below the superconducting transition temperature these networks show a hysteretic steplike current-voltage characteristic. We present two-dimensional images of the resistive areas of the networks at various bias points and of the spatial distribution of the supercurrent below the critical current, showing the Meissner effect. Above the critical current, the voltage is localized at single rows of the network, oriented perpendicular to the transport current. By increasing the bias current, we always observe adjacent rows switching into the resistive state. The observed dynamics of the networks can be explained by the creation of localized phase-slip centers in the wires of the network. At temperatures close to the transition temperature the steps in the current-voltage characteristic disappear and the networks show a resistive behavior typical for wide superconducting bridges. We interpret the transition between the two temperature regimes as a transition from a quasi-one-dimensional to a two-dimensional behavior. \textcopyright{} 1996 The American Physical Society.

Hysteretic current-voltage characteristics of platelet boundaries in melt-textured bulk Ag-doped YBa 2Cu 3O 7,δ and heating effects

The current-voltage characteristics (CVCs) of isolated platelet boundaries in melt-textured bulk Ag-doped YBa 2Cu 3O 7,δ have been measured. The CVCs showed pronounced hysteresis. However, the critical current did not show any field dependence. Such hysteresis can be explained by a self-heating model.

Intrinsically damped multilayered (stacked) Nb/Al-AlNx/Nb superconducting tunnel junctions

Abstract Single and stacked Nb/Al-AlNx/Nb superconducting tunnel junctions with both hysteretic (underdamped) and non-hysteretic (overdamped) current-voltage relationships have been produced utilizing reactively sputtered aluminum nitride tunnel barriers. Standard multilayer deposition and lithographic processing techniques, compatible with existing Nb/Al-AlOx/Nb fabrication techniques, are used in fabrication. The degree of damping in the junctions is controlled through the deposition parameters. Critical current dependence on applied magnetic field indicates that the overdamped junctions have a distributed Josephson coupling and are not simple microshorts. The shorter deposition time to grow reactively sputtered AlNx barriers makes this system a promising alternative to fabricate stacked Josephson junctions.

Nonlinear energy relaxation oscillations and chaotic dynamics of hot carriers

It is shown that recently observed complex chaotic behavior associated with low temperature impurity breakdown can be understood by introducing the mean energy per carrier E as an additional dynamic variable besides the carrier densities. A set of coupled nonlinear evolution equations for the carrier density and mean energy is derived by a moment expansion of the Boltzmann equation including, in particular, impact ionization. This process leads to a novel, strongly nonlinear relaxation term in the dynamic energy balance equation. The simplest, spatially homogeneous version of the model yields hysteretic or non-hysteretic static current-voltage characteristics, and spontaneous self-sustained current oscillations. It can also be used to explain the coupling of the oscillations in two spatially separated hot carrier subsystems via energy exchange.

NbN<inf>x</inf>-NbO<inf>y</inf>-PbIn<inf>z</inf>Josephson junctions with R.F. oxidised tunneling barriers

We report the fabrication of high quality Josephson tunnel junctions made by the r.f. sputter-deposition method. The characteristics of these junctions were determined at 4.2°K as a function of the following fabrication parameters: the substrate temperature, the sputtering power during base electrode deposition, and the r.f. oxidation time for the barrier. We have obtained critical current densities from 90 to 800 Amperes/cm2which depended exponentially on the barrier formation time, a gap energy of 3.3meV, and hysteretic current-voltage characteristics. Thermal cycling of a few junctions resulted in small changes in the current-voltage curves. Auger Electron Spectroscopy and ESCA of the films show that x=1.02, z=0.25, and that the niobium oxide is a mixture of Nb 2 O 5 and the lower oxides, NbO and NbO 2 , that are present at the oxide-base electrode interface.

A paradox in the crossover of the mechanisms causing the hysteresis in long, thin-film superconductors

We point out an apparent paradox encountered in the region where the temperature of a voltage-sustaining film at the upper critical current crosses its T/sub c/ concerning the crossover of the two dominant heating mechanisms currently used to account for the lower critical currents observed on the hysteretic current-voltage characteristics of long, thin-film superconductors at varying high power levels. We explore a possible solution of this paradox by carefully examining the relevant heating models and available experimental observations.

Nonequilibrium Dynamics in a Superconducting Thin-Film Microbridge

First measurements of the time for the recovery of the critical current at a phaseslip site have been made by studying the frequency dependence of the hysteretic rf current-voltage characteristics in the low-power limit. The data are incompatible with recent hot-spot models but can be expalined by a model relating a nonequilibrium length to the critical current.