Structural changes in thin films of yttria-stabilized zirconia irradiated with uranium ions in the electronic stopping regime

Poly-crystalline, partially monoclinic, yttria partially stabilized zirconia (Y-PSZ) was deposited on a 25 nm thick Au-covered (1 0 0) Si substrate by means of UV pulsed laser ablation. The 400 nm thick films were irradiated with single ionized swift heavy uranium (238U) ions of about 1300 MeV, applying ion fluences from 5 to 20 x 1011 cm-2. The samples were characterized before and after irradiation using X-ray diffraction (XRD), micro-Raman spectroscopy, and transmission electron microscopy (TEM). With increasing ion fluence there is a progressive change from monoclinic to tetragonal/cubic polymorphs. TEM of selected samples indicates formation of Au islands on the Si substrate and the development of a defective microstructure under irradiation. The nature, distribution and aggregation of ion-beam induced defects are mainly associated with oxygen migration to the film surface and are probably responsible for the structure changes under irradiation.