Dynamic current-voltage characteristics of chalcogenide-glass thin-film diodes

The dynamic current-voltage characteristics are analyzed for a metal/chalcogenide glass/metal system in which the metal of one or both electrodes interacts with the glass.     

Investigation of the current-voltage characteristics of thin-film ZnSe-ZnTe heterojunction structures

This paper investigates the current-voltage characteristics of thin-film ZnSe-ZnTe heterojunction structures grown on zinc substrates. It is shown that the maximum rectification coefficient for such systems is observed when the condition d_1,2=d₀ is satisfied. On the basis of the general equation of the current-voltage characteristics of heterojunctions taking into account the boundary conditions, equations are derived which describe the behavior of the forward and back branches of the current-voltage characteristic of the heterojunction under consideration, and an explanation is given of the divergence between the theoretical and experimental results.     

Conductivity and barrier effects in thin-film PZT-based heterostructures, depending on the conditions of synthesis

Electrical conductivity and dielectric characteristics in Pt/Pb(Zr_0.54,Ti_0.46)O₃/Pt film structures synthesized at different temperatures are studied. Volt-ampere (I–V) and volt-farad (C–V) characteristics are obtained. Asymmetry of the I–V characteristics is revealed, indicating a difference in the potential barriers at the interfaces of the analyzed structures that varies depending on the synthesis conditions. The values of the potential barriers at the Pt/PZT interfaces were calculated from the C–V characteristics. Two key conductivity mechanisms, Ohmic and Poole-Frenkel emission, were noted.     

Crystallization behaviour of PZT in multilayer heterostructures

Microstructural and electrical properties of PZT (lead zirconate titanate) thin films prepared by sol-gel techniques at annealing temperatures in the range from 550°C to 900°C are studied. Perovskite (Pe) grain nucleation in PZT film starts but not completes at 550°C. Along with formation of round Pe (111) grains on the Pt (111) interface, the film contains small Pe and pyrochlore (Py) grains. Films annealed at the temperatures higher than 600°C demonstrate column structure of Pe grains, the amount of Py inclusions reduces with the annealing temperature and practically disappears at 700°C. An increase of annealing temperature leads to enhancement of (100) Pe orientation as a result of Ti diffusion on the Pt surface. Polarization decreases with the annealing temperature (maximum at 600°C), whereas permittivity increases up to the annealing temperature of 750°C.     

Structure of interfaces in thin-film metallic multilayer heterostructures

It is demonstrated that the structure of interfaces in thin-film metallic multilayers can be predicted from the phase diagrams of binary alloys of metals constituting the multilayers. Experimental data on the small-angle X-ray reflectivity and magnetization of the samples are used for characterizing the structure of the interfaces.     

Investigation of oxidation process and properties of indium and tin-based thin-film heterostructures

Solid-phase processes in thin films (～200 nm) based on tin and indium oxides (ITO structures) prepared by magnetron sputtering from a composite target (93 at % In and 7 at % Sn) and by layer-by-layer deposition of In/Sn/Si and Sn/In/Si structures from two magnetrons in a single vacuum cycle have been investigated in the work under their oxidation in an oxygen flow. Two ways of optically transparent semiconductor film formation have been compared using near-edge fundamental absorption spectroscopy, x-ray diffraction analysis, and electron microscopy and dynamics of the change in their optical and structure properties has been studied. In the case of oxidation of the layer-by-layer deposited structures, the heterogeneous phase composition of the film is confirmed both by the XRD data and by the optical results. Only wide-band-gap phases with an energy of direct transitions of 3.5–3.6 eV have been found in the films prepared by magnetron sputtering from a composite target after their oxidation. These wide-band-gap phases are associated with In₂O₃ oxide and a tin-doped indium oxide compound.     

Zero-field current-voltage characteristics in high-temperature superconductors

We have observed the anomalous magnetization of Bi₂Sr₂CaCu_2−xNi_xO₈ (x = 0 and 0.02) single crystals. Anisotropy decreases with iodine intercalation although it expands the space between CuO₂ layers. Iodine intercalation seems to suppress the magnetization anomaly for Ni = 1% crystals, but not for Ni = 1% substituted crystals. We have discussed these results in terms of the increase of anisotropy by Ni substitution and the dimensional crossover of flux lines. Effects of both oxygen concentration and substitution of a magnetic element for the Cu site on the anisotropy of Bi₂Sr₂CaCu₂O₈ crystals show the same tendency as the case of the YBa₂Cu₃O₇ superconductor.     

Auger spectroscopy and properties of Ir(Pt)/PZT(PZT/PT)/Ir nanosized thin-film structures

Studies of the elemental distribution profiles through the thickness of thin-film ferroelectric capacitor structures using Auger spectroscopy made it possible to establish the relation between the elemental and phase composition of the structures, on the one hand, and their electrophysical properties, on the other. Special features were observed in the behavior of the lead titanate underlayer both in the as-fabricated and aged structures. It is shown that the variation in the characteristics of the capacitor structures during aging is caused by diffusion of the elements at the interfaces and in the PZT film against a background of a significant increase in the oxygen concentration. As a result, interface-modifying oxide layers form and the trap density on the upper and lower interfaces decreases in all samples.     

Generation and evolution of partial misfit dislocations and stacking faults in thin-film heterostructures

An analysis is made of the specific features in the generation and evolution of partial misfit dislocations at the vertices of V-shaped configurations of stacking fault bands, which terminate in the bulk of the growing film at 90° partial Shockley dislocations. The critical thicknesses h _c of an epitaxial film, at which generation of such defect configurations becomes energetically favorable, are calculated. It is shown that at small misfits, the first to be generated are perfect misfit dislocations and at large misfits, partial ones, which are located at the vertices of V-shaped stacking-fault band configurations emerging onto the film surface. Possible further evolution of stacking-fault band configurations with increasing film thickness are studied.     

Static current-voltage characteristics of point-contact crystal rectifiers

An investigation of the current-voltage characteristics of a point-contact rectifier, taking account of the surface states, is described. Consideration is given to the influence of the forming of the rectifier point upon the current-voltage characteristic due to the change in the charge density in the surface state, caused by the redistribution of the charges on the contact periphery and in the bulk material.     

Properties and current-voltage characteristics of discharges in waveguide gas lasers

The paper deals with the properties andI-V characteristics of discharges in narrow capillaries used, for example, for He−Ne waveguide lasers. It has been observed that discharges in He−Ne waveguide lasers are unstable because of the strongly falling characteristic. A theory is presented which assumes that at low currents wall charges restrict the positive column to a narrow plasma channel and are the main reason for the observed falling characteristic. A numerical evaluation for helium gives results which agree well with experimental data.     

Crystallization kinetics of thin-film amorphous Cox(PZT)100 − x nanocomposites

Conductivity of thin-film heterogeneous Co_x(PZT)_{1 ? x} structures has been studied in a wide ranges of metallic phase concentrations and temperatures. The crystallization kinetics of amorphous samples of Co_x(PZT)_{100 ? x} nanocomposites has been investigated by analyzing the time dependences of their conductivity. The main parameters of the crystallization process have been determined.     

Zero-field current-voltage characteristics in high-Tc superconductors

Zero-field current-voltage (I–V) characteristics of various high-temperature superconductor samples are analyzed in the context of the current-temperature (I−T) phase diagram. After establishing the validity and relevance of the phase diagram to these materials, the anisotropy factor is extracted from the slope ofI _c ¹ (T) (the current defined by the onset of resistance). It is concluded that studying theI−V characteristics of amples in the context of theI−T phase diagram is a simple, useful tool for comparing samples. Work supported by the Office of Naval Research.     

Silicon diffused diodes with nearly ideal current-voltage characteristics

It is shown that nearly ideal current-voltage characteristics (I-V curves) can be obtained for small-area, shallow silicon diffused p-n junctions irradiated with ⁶⁰Co gamma rays in the dose range 10³–5×10⁵ Gy. In the irradiated diodes the current transfer mechanism is observed to shift from generation-recombination to diffusion. The nonideality factor on the forward branch of the I-V curve decreases from 1.68 in the unirradiated diode to 1.17 in a diode irradiated to a dose of 5×10⁵ Gy. A saturation current is observed on the reverse branch of the I-V curves of irradiated diodes at room temperature. Zh. Tekh. Fiz. 68, 131–132 (October 1998)     

Superlinearity of current-voltage characteristics of oxidized cholesterol bilayer membranes

Current-voltage characteristics of bilayer oxidized cholesterol membranes were measured in 0·1 M KCl solution. The ohmic conductance was (5±3) × 10^–4–1 m^–2. To explain the superlinearity of the characteristics, a model of the ion transport through transient pores was used. Alternative diffusion barrier models could also explain the nonlinearity, but the distribution coefficients of permeable ions between the membrane hydrocarbon phase and the aqueous phase had to be taken unreasonably high.     

Investigation of the current-voltage characteristics of superconducting film structures

The current-voltage characteristics (CVC) of sandwich structures consisting of superconducting Pb(S) and normalconducting Ag(N) in the combination SNS, NSN and SN have been investigated with the current flow parallel to the phase boundaries. We observed step structures in the CVCs and their dependence on an external magnetic field and on the layer thickness of Pb and Ag in the temperature range between 1.5 K and 4.2 K. The experimental results are compared qualitatively with the behaviour of the CVCs calculated by Hansack and Kümmel¹⁰.     

Cathode and scaling properties related to the shape of current-voltage characteristics

It is shown that — even if the initial velocities of the emitted electrons are negligible — the use of Child's equation in the evaluation of work function distributions from experimental current-voltage characteristics gives rise to erroneous results. This is done with the aid of scaling properties, experimental results and solution of Poisson's equation for a model system. Moreover, it is made clear that increases in perveance with decreasing accelerating potential are due to the influence of (axial) initial velocities.     

The current-voltage characteristics of field-effect transistors with short channels

The current-voltage characteristics of MOS field-effect transistors is investigated theoretically and experimentally in the region of extremely high drain electric fields E_D using the electron temperature concept in the classical three-dimensional theory. It is found that the drain field at which the drain current becomes non-ohmic on the basis of hot electron effects is related to the surface field E_zs by E_D～√E_zs. Other expressions for the field dependent mobility are also given which allow the construction of the current-voltage characteristics.