AC impedance studies on metal/nanoporous silicon/p-silicon structures

Alternating current (AC) impedance measurements have been performed on 10−15 thick porous silicon layers on a (100) p-type silicon (p(+)Si) substrate with the aluminium (Al) top electrode in a sandwich configuration in the range of 20 Hz to 1 Hz and in the temperature ranging between 152 K−292 K. The ac conductivity sac was found to increase with frequency f according to the universal power low: sAf=acs where the exponent s is a frequency and temperature dependent quantity. Hopping process is found to be dominant at low temperatures and high frequencies while a thermally activated free band process is responsible for conduction at higher temperatures. Capacitance is found to decrease with frequency but increase with temperature. Frequency dependence of loss tangent is observed with a temperature dependent minimum value

The morphology, electrical conductivity and vapour sensing ability of inkjet-printed thin films of single-wall carbon nanotubes

Thin films containing single-wall carbon nanotubes (SWCNTs) have been prepared using the inkjet printing (IJP) technique. Atomic force microscopy (AFM) has been used to investigate the morphology of these layers. The inkjet printed films consisted of small, randomly-oriented islands of nanotubes, the topography of which was dependent on the nature of the substrate surface. The in-plane electrical characteristics of the films were measured at room temperature. The current versus voltage data exhibited non-linear behaviour, which could be fitted to the theoretical model for Poole-Frenkel conductivity. Preliminary measurements are also reported on the use of the thin layers to detect alcohol vapour

Charge Storage in Pentacene/Polymethylmethacrylate Memory Devices

The electrical behavior of organic metal-insulator-semiconductor (MIS) structures incorporating a layer of self-assembled metallic nanoparticles is described. These have been based on thermally evaporated pentacene (semiconductor) and spin-coated polymethylmethacrylate (insulator). The MIS devices containing the nanoparticles exhibited significant hysteresis in their capacitance-versus-voltage and conductance-versus-voltage characteristics, which was attributed to the charging and discharging of the nanoparticles. The memory structure reported here offers a useful advance in the development of flexible organic memory structures

Memory effects in hybrid silicon-metallic nanoparticle-organic thin film structures

We report on the electrical behaviour of metal-insulator-semiconductor (MIS) structures fabricated on silicon substrates and using organic thin films as the dielectric layers. These insulating thin films were produced by different methods, including spin-coating (polymethylmethacrylate), thermal evaporation (pentacene) and Langmuir-Blodgett deposition (cadmium arachidate). Gold nanoparticles, deposited at room temperature by chemical self-assembly, were used as charge storage elements. In all cases, the MIS devices containing the nanoparticles exhibited hysteresis in their capacitance versus voltage characteristics, with a memory window depending on the range of the voltage sweep. This hysteresis was attributed to the charging and discharging of the nanoparticles from the gate electrode. A maximum memory window of 2.5 V was achieved by scanning the applied voltage of an Al/pentacene/Au nanoparticle/SiO2/P-Si structure between 9 and -9 V. (C) 2008 Elsevier B.V. All rights reserved