Metastable materials formation by ion beam assisted deposition: application to metal clusters in ceramic matrices

The collision cascade, the fundamental event in ion-solid interactions, is responsible for the beneficial effects on thin films deposited by low energy ion beam assisted deposition (IBAD) or by energetic ion assisted deposition processes in general. However, the fundamental implications of the marriage of collision cascades and film growth processes have yet to be fully realized. The first section of this paper reviews the effects of ion bombardment on film growth and reaches the conclusion that IBAD processing drives material synthesis parameter phase space into new regimes. Therefore, IBAD processing leads to microstructures far from equilibrium that are unattainable by other materials synthesis methods. The second part of this paper reviews an application of IBAD which tends to support the hypothesis that it is a distinct form of ion-solid interaction. It describes the production of unique metastable materials, demonstrated through deposition of metal nanoclusters in a dielectric matrix by means of beam assisted phase separation (BAPS), a term coined here to describe deposition of phase-separated multicomponent materials.