Gabriella Zappalà

Nanoscale Electrical Investigation of Layer‐by‐Layer Grown Molecular Wires

Nanoscopic metal-molecule-metal junctions consisting of Fe-bis(terpyridine)-based ordered nanostructures are grown in layer-by-layer fashion on a solid support. Hopping is demonstrated as the main charge-transport mechanism both experimentally and theoretically.

Nitric oxide assisted C60 secondary ion mass spectrometry for molecular depth profiling of polyelectrolyte multilayers

RATIONALE Secondary ion mass spectrometry (SIMS) with polyatomic primary ions provides a successful tool for molecular depth profiling of polymer systems, relevant in many technological applications. Widespread C60 sources, however, cause in some polymers extensive damage with loss of molecular information along depth. We study a method, based on the use of a radical scavenger, for inhibiting ion-beam-induced reactions causing sample damage. METHODS Layered polystyrene sulfonate and polyacrylic acid based polyelectrolyte films, behaving differently towards C60 beam-induced damage, were selected and prepared as model systems. They were depth profiled by means of time-of-flight (TOF)-SIMS in dual beam mode, using fullerene ions for sputtering. Nitric oxide was introduced into the analysis chamber as a radical scavenger. The effect of sample cooling combined with NO-dosing on the quality of depth profiles was explored. RESULTS NO-dosing during C60-SIMS depth profiling of >1 micrometer-thick multilayered polyelectrolytes allows detection, along depth, of characteristic fragments from systems otherwise damaged by C60 bombardment, and increases sputtering yield by more than one order of magnitude. By contrast, NO has little influence on those layers that are well profiled with C60 alone. Such leveling effect, more pronounced at low temperature, leads to a dramatic improvement of profile quality, with a clear definition of interfaces. CONCLUSIONS NO-dosing provides a tool for extending the applicability, in SIMS depth profiling, of the widely spread fullerene ion sources. In view of the acceptable erosion rates on inorganics, obtainable with C60, the method could be of relevance also in connection with the 3D-imaging of hybrid polymer/inorganic systems.

Improving the electrical performance of solution processed oligothiophene thin-film transistors via structural similarity blending

Here we show that the blending of structurally similar oligothiophene molecules is an effective approach to improve the field-effect mobility and Ion/Ioff as compared to single component based transistors. The effect of addition of each component is studied extensively using a wide array of methods such as X-ray diffraction, ToF-SIMS, and ambient UPS correlated with the electrical characterization.

SIMS characterization of surface-modified nanostructured titania electrodes for solar energy conversion devices

This paper deals with the investigation of a stepwise surface priming strategy based on zirconium phosphate-phosphonate chemistry (ZP priming), which was applied for the first time to nanostructured, micrometer-thick titanium dioxide electrodes. Through the extensive use of secondary ion mass spectrometry (SIMS) depth profiling technique, it was possible to monitor the composition of the titania samples after every single reaction step of the priming. In particular, the impregnation of the surface with zirconium was found to be the determining step of the whole treatment. SIMS data allowed for the identification of the diffusion mechanism that governs the uptake of zirconium from an aqueous Zr(IV)-containing solution. Furthermore, from the depth profiling results, it was possible to optimize the priming experimental conditions in order to achieve the desired uniform surface modification along the entire nanostructured TiO2 layer. ZP-priming of nanostructured titania electrodes could be exploited within th...