Electronic Properties of LiMo3Se3-Nanowires and Mo3Se3-Nanowire-Networks for Nanoscale Electronic Devices

Nanowires and nanotubes have attracted much interest as potential building blocks for nanotechnology. This interest can be traced to the novel structural and electronic properties of these nanomaterials. Here we describe a study that measures the electronic properties of bare LiMo3Se3-nanowires, together with wires that have been stabilized by alkylammonium- and pyridinium-ligands. The bare LiMo3Se3-nanowires consist of individual wire bundles whereas the stabilized wires form networks with an inter-wire spacing determined by the ligand. The bare wires are shown to be metallic but susceptible to electrical degradation (oxidation) in air. However, conductivity measurements at different temperature and oxidation times show that conduction in the wire networks occurs via a percolation mechanism and is activated. Moreover, the corrosion rate of the Mo3Se3-nanowires is dramatically reduced when the wires are stabilized, demonstrating that the ligands form a protective semi-insulating coating.

Microgalvanics: locally resolved concentration measurements with ion-selective microelectrodes and chronoamperometric microelectrodes

Localized electrochemical analysis in the micrometer-range is useful for the in situ investigation of galvanic plating processes. Two techniques are presented, a potentiometric and a chronoamperometric one, using xyz-positionable microelectrodes for practical concentration measurements in microstructures during cathodic metal deposition. Locally measured concentration data c(xy) are related to local current density i(xy), which is not obtainable by other means in a system containing excess supporting electrolyte.

Low energy ion implantation in polybithiophene: microstructuring and microanalysis

Low energy ion implantation in polybithiophene (thickness 200 nm) forms a 20 nm thin modified surface layer. Combining surface analysis and electrochemical methods a non destructive depth resolved investigation of the properties of the implanted layer was performed. The composition of the modified layer is dependent on the implanted species: N causes doping, O has a sputtering effect. The modified layer acts as an electronic and ionic barrier as shown by cyclic voltammetry and electron transfer reactions. The effectivity of barrier formation is dependent on the sample pretreatment and the redox state. For reduced samples the redox charge increases for repeated voltammograms (regeneration effect). The according dose dependent band scheme shows an increasing surface resistivity for low doses. At high doses the surface resistivity decreases again due to graphitization. By application of a microstructured mask the polybithiophene was structured within a microm range. Laterally high resolving methods revealed sharp interfaces between implanted and pristine surface ranges. The doping pattern and the electronic properties are localized and do not alter even in an electrolyte. So conducting polymers can be microstructured to give stable structures with changed composition and modified electronic and ionic properties as required for microtechnological applications.