Optical and mechanical performance of nanostructured cerium oxides for applications in optical devices

Nanostructured CeO_2−x films have been grown by electron beam evaporation (EBE) and ion beam assisted deposition (IBAD). The CeO_2−x consists of grains with size 9–28 nm and nanoscale voids enhancing the surface and quantum-size effects. We investigate the sizedependent electronic properties of nanostructured CeO_2−x films and we establish relations between them and the film structure, composition and morphology. We investigate how the structure and morphology variations affect the absolute values of the dielectric function at the UV-Vis and IR spectral regions. The nature of the fundamental gap E_g of CeO_2−x is also considered. In addition we study in detail the light absorption mechanisms in the UV spectral regions and we correlate them with the reported band structures of the pure CeO₂ and Ce₂O₃. We also employ nanoindentation testing to compare the mechanical response of CeO_2−x films grown by EBE and IBAD. Correlations between the mechanical properties of the films and the growth parameters have been made providing the possibility of tailoring films with good mechanical performance for optical device applications.