S-shaped current–voltage characteristics of polymer composite films containing graphene and graphene oxide particles

The resistive switching effects in composite films containing polyfunctional polymers, such as derivatives of carbazole (PVK), fluorene (PFD), and polyvinyl chloride (PVC), and also graphene particles (Gr) and graphene oxide (GO), the concentration of which in the polymer matrices varied in the range from 1 to 3 wt % corresponding to the percolation threshold in such systems, have been studied. The analysis of the elemental composition of the investigated composites by means of X-ray photoelectron spectroscopy have shown that the oxidation degree of Gr in GO is about 9 to 10%. It has been established that a sharp conductivity jump characterized by S-shaped current-voltage curves and the presence of their hysteresis occurs upon applying a voltage pulse to the Au/PVK (PFD; PVC): Gr (GO)/ITO/PET structures, where ITO is indium tin oxide, and PET is poly(ethylene terephthalate), with the switching time, t, in the range from 1 to 30 μs. The observed effects are attributed to the influence of redox reactions taking place on the Gr and GO particles enclosed in the polymer matrix, and the additional influence of thermomechanical properties of the polymer constituent of the matrix.

     

Kinetic constants of abnormal grain growth in nanocrystalline nickel

The grain growth in nanocrystalline nickel with a purity of 99.5 at % during non-isothermal annealing was experimentally investigated using differential scanning calorimetry and transmission electron microscopy. Nanocrystalline nickel was prepared by electrodeposition and had an average grain size of approximately 20 nm. It was shown that, at a temperature corresponding to the calorimetric signal peak, abnormal grain growth occurs with the formation of a bimodal grain microstructure. Calorimeters signals were processed within the Johnson–Mehl–Avrami formalism. This made it possible to determine the exponent of the corresponding equation, the frequency factor, and the activation energy of the grain growth, which was found to be equal to the activation energy of the vacancy migration. The reasons for the abnormal grain growth in nanocrystalline nickel were discussed.     

Composite Films Based on Carbon Quantum Dots in a Matrix of PEDOT:PSS Conductive Polymer

Physics of the Solid State - Carbon quantum dots (CQDs), as well as their composites with the PEDOT:PSS conductive polymer, are hydrothermally synthesized from glucose, and their electrical...     

Anisotropy of a Terahertz Electromagnetic Response of Filament Microstructures of a Composite Based on Polypropylene with Carbon Nanofibers

JETP Letters - Linear dichroism and birefringence are detected in composite microfilaments consisting of polypropylene with carbon nanofibers in the terahertz spectral range. The magnitude of...     

Electrical and optical properties of light-emitting field-effect transistors based on MEH-PPV polymer composite films with ZnO nanoparticles

The optical and electrical properties of light-emitting field-effect transistor structures with an active layer based on nanocomposite films containing zinc oxide (ZnO) nanoparticles dispersed in the matrix of the soluble conjugated polymer MEH-PPV have been investigated. It has been found that the current-voltage characteristics of the field-effect transistor based on MEH-PPV: ZnO films with a composite component ratio of 2: 1 have an ambipolar character, and the mobilities of electrons and holes in these structures at a temperature of 300 K reach high values up to ～1.2 and ～1.4 cm²/V s, respectively, which are close to the mobilities in fieldeffect transistors based on ZnO films. It has been shown that the ambipolar field-effect transistor based on MEH-PPV: ZnO films emits light at both positive and negative gate bias voltages. The mechanisms of injection, charge carrier transport, and radiative recombination in the studied structures have been discussed.     

Charge carrier transport in conducting polymers on the metal side of the metal-insulator transition: A review

The advances achieved in the field of the synthesis of conducting polymer films and the results of experimental investigations of the mechanism of charge carrier transport in heavily doped conducting polymer films on the metal side of the metal-insulator transition have been considered. The samples studied belong to the last generation of conducting polymers with a low degree of structural disorder, which makes it possible to dope samples to a highly conducting state characterized by an increased stability. Apart from the study of the morphology, structure, and doping conditions, the mechanism of low-temperature transport in these polymers has been investigated in detail. The results of investigations of the transport at low temperatures (T < 1 K) have been described, and a phenomenological model of charge carrier transfer in these systems has been proposed. The polymers under investigation have been widely used as injecting and accumulating layers in light-emitting organic diodes and solar cells.     

Terahertz Vibrational Modes in CH3NH3PbI3 and CsPbI3 Perovskite Films

JETP Letters - Films of CH3NH3PbI3 organometallic perovskite, which is currently considered as a promising basic material for new-generation solar cells, as well as films containing CsPbI3...     

Electrical Properties of Organometallic Perovskite Films

Physics of the Solid State - The electrical properties of the films of organometallic perovskites CH3NH3PbBr3 and CH3NH3PbI3 were studied. Current–voltage characteristics for the CH3NH3PbBr3...