OPTICAL AND ELECTRICAL PROPERTIES OF METAL POLYMER NANOCOMPOSITES FABRICATED WITH SUPERSONIC CLUSTER BEAM IMPLANTATION

Abstract

Clusters are aggregates composed of a countable number of atoms or molecules, starting with the dimer and reaching, with a vaguely defined upper bound of several hundred thousand atoms, into that interesting size range. Clusters have properties that are different from both atoms and bulk materials as in these small aggregates the surface-to-volume ratio is very large and hence the surface atoms, play a dominant role compared to the bulk ones. By assembling preformed clusters, one can build nanostructured materials. These can be divided in two main categories: cluster assembled films and nanocomposites. In the former case nanoparticles are deposited on a substrate in the latter they are incorporated in a matrix, a polymer for instance. Nanostructured materials offer exciting pathway for the construction of macroscopic materials with designer-specified optical, electrical, and catalytic properties which reflect the ones of their building blocks. The object of this thesis is the study of the optical and electrical properties of metal-polymer nanocomposites (MPNs) in response to mechanical deformation. Reflectance of MPNs is also exploited to develop reflective and bendable diffracting gratings which can be adapted to concave surfaces in order to add focusing power to the diffracting one. A further study regards the evolution of the electrical resistance during the growing of the nanostructured materials on different substrates. Then, the electrical properties of the systems in response to a voltage applied are explored, to find if peculiar phenomena such as resistance switching could occur. Recipes to fabricate robust and reproducible devices which exhibit controllable resistance switching were developed, both for cluster-assembled thin films and MPNs; in this latter case the possibility of controlling the switching activity with mechanical bending is demonstrated as well.