This paper reports that the Schottky junctions between low work function metals (e.g. Al and In) and doped semiconducting polymer pellets (e.g. polyaniline (PANI) microsphere pellet and polypyrrole (PPy) nanotube pellet) have been prepared and studied. Since Ag is a high work function metal which can make an ohmic contact with polymer,silver paste was used to fabricate the electrodes. The Al/PANI/Ag heterojunction shows an obvious rectifying effect as shown in I V characteristic curves (rectifying ratio γ=5 at ±6 V bias at room temperature). As compared to the Al/PANI/Ag,the heterojunction between In and PANI (In/PANI/Ag) exhibits a lower rectifying ratio γ=1.6 at ±2 V bias at room temperature. In addition,rectifying effect was also observed in the heterojunctions Al/PPy/Ag (γ=3.2 at ±1.6 V bias) and In/PPy/Ag (γ=1.2 at ±3.0 V bias). The results were discussed in terms of thermoionic emission theory.
This paper reports that the multi-walled carbon nanotubes(MWCNT)/nylon-6(PA6) nanocomposites with different MWCNT loadings have been prepared by a simple melt-compounding method.The electrical,dielectric,and surface wetting properties of the CNT/PA6 composites have been studied.The temperature dependence of the con-ductivity of the CNT/PA6 composite with 10.0 wt% CNT loading(σRT-10-4 S/cm) are measured,and afterwards a charge-energy-limited tunnelling model(ln σ(T)-T-1/2) is found.With increasing CNT weight percentage from 0.0 to 10.0 wt%,the dielectric constant of the CNT/PA6 composites enhances and the dielectric loss tangent increases two orders of magnitude.In addition,water contact angles of the CNT/PA6 composites increase and the composites with CNT loading larger than 2.0 wt% even become hydrophobic.The obtained results indicate that the electrical and surface properties of the composites have been significantly enhanced by the embedded carbon nanotubes.
Poly(vinylpyrrolidone)/tetrabutyl titanate (PVP/ [CH3(CH2)3O]4Ti) composite nanofibres are prepared by elec- trospinning. After calcining parts of composite nanofibres in air at 700 C, petal-like TiO2 nanostructures are obtained. The characterizations of composite nanofibres and TiO2 nanostructures are carried out by a scanning electron micro- scope, an x-ray diffractometer, and an infrared spectrometer. Electrospun nanofibres are pressed into pellets under different pressures in order to explore their dielectric properties. It is found that the dielectric constants decrease with frequency increasing. The dielectric constant of the composite nanofibre pellet increases whereas its dielectric loss tangent decreases due to the doped titanium ions compared with those of pure PVP nanofibre pellets. In addition, it is observed that the dielectric constant of the composite nanofibre pellet decreases with the increase of the pressure applied in pelletization.
We report the current-voltage (I-V) characteristics of individual polypyrrole nanotubes and poly(3,4-ethylenedioxythiophene) (PEDOT) nanowires in a temperature range from 300 K to 2 K. Considering the complex structures of such quasi-one-dimensional systems with an array of ordered conductive regions separated by disordered barriers, we use the extended fluctuation-induced tunneling (FIT) and thermal excitation model (Kaiser expression) to fit the temperature and electric-field dependent I–V curves. It is found that the I–V data measured at higher temper-atures or higher voltages can be well fitted by the Kaiser expression. However, the low-temperature data around the zero bias clearly deviate from those obtained from this model. The deviation (or zero-bias conductance suppression) could be possibly ascribed to the occurrence of the Coulomb-gap in the density of states near the Femi level and/or the enhancement of electron-electron interaction resulting from nanosize effects, which have been revealed in the previous studies on low-temperature electronic transport in conducting polymer films, pellets and nanostructures. In addition, similar I-V characteristics and deviation are also observed in an isolated K0.27MnO2 nanowire.
An innovative heterojunction is fabricated between two sides of a freestanding thin film of HCl-doped polyaniline(PANI) derivative containing azobenzene side-chain,which is synthesized through an N-alkyl-substituted reaction.Of the film,the side with being irradiated by UV light during preparation is represented as 'A side';the other side without being irradiated is represented as 'N side'.The electrical properties of the heterojunction are measured and the rectifying effect is observed in the current-voltage characteristic curves with the values of rectifying ratio(γ) being 20 at ±0.06 V at T = 77 K and 4 at ±0.02 V at T = 300 K separately.
