Charge transport in oxide-in-oxide nanostructured silica-based dielectrics

Nanostructured oxide-in-oxide glassceramics are a composite materials in which a nanocrystal phase is embedded in an amorphous matrix. These materials possess unique properties since they combine functional properties imparted by the nanocrystals with structural features dictated by matrix composition. Specifically, in photonics and optoelectronics applications the possibility of obtaining a wide-band gap nanocrystal phase homogenously dispersed in a transparent silica-based matrix is the ideal approach for achieving specific optical activities in a transparent glassy material. In this view, germanosilicate glasses embedding nanocrystals of gallium oxide have recently gained attention for their potential use as hosts for rare earth and transition metal ions for tailored optical emission and active window in solar-blind detection, in bulk, fiber and laser-written geometry. The opportunity of replicating such materials also in thin film geometry may pay the way to the design of new devices such as electroluminescent thin films, compact UV-detectors, and non-linear electrical components. In fact, the nanoparticle-mediated electrical conduction and charge trapping could, in principle, lead to unexpected results such as a resistance and/or capacitance behavior dependent on the history of applied currents. This effect can, in turn, be exploited for the production of solid state memories in which the 0/1 state can be written by appropriate current history and read by the resulting value of resistance or capacitance. Here we present a novel strategy for the preparation of such films based on magnetron sputtering of targets made of bulk glasses and the collected results concerning optical, morphological and electrical characterization.