Injeção de cargas em materiais dielétricos e produção de nanopartículas metálicas por técnicas de SPM.

Abstract

The present work can be divided in two parts, where the manipulation and modification capacities of Scanning Probe Microscopy (SPM) techniques are explored. In the first part, the idea of contact electrification aiming at the development of nano-scale data storage deviceshas been explored through a careful investigation of charge injection on insulating films (SiO2 and PMMA) via SPM techniques. A complete route for data storage, showing simple and effective ways to write (inject the charge with an Atomic Force Microscopy (AFM) tip), to read (detect the charge with Electric Force Microscopy (EFM)), to store (keep sample charge by changing ambient and surface conditions) and to erase the information (make the discharge process faster) is proposed and discussed. Results show that monitoring parameters such asambient relative humidity and surface hydrophobic/hydrophilic character enable the control of pattern size, lateral dispersion, and storage time. Models for charge quantification are also presented and discussed. Additionally, it is shown that when a proper bias is applied at the tipor at the substrate during the EFM image, a slow decreasing of the EFM signal is observed. Such effect is carefully investigated both experimentally and theoretically (via computer simulations). In the second part, an innovative process enabling both the controlled growthand positioning of metal nanoparticles (NPs) is reported. Using SPM techniques, metal NPs are directly grown in the region of interest via reduction of metallic ions in a polymer matrix induced by a properly biased SPM-tip. The metallic nature of these NPs is established via Xraydiffraction and UV-VIS spectroscopy experiments. Some initial applications of this process, such as enhanced of Raman spectrums (SERS Surface-Enhanced Raman Spectroscopy) and decoration of carbon nanotubes with metal NPs, are also briefly demonstrated and discussed.