Investigation of structural and morphological properties of high energy ion irradiated KNN films

Abstract

Abstract The transfer of high localized energy density to target matrix via swift heavy ion provides a domain to engineer the properties of materials in a systematic and controlled mode. The present study describes the influence of ion irradiation on structural properties and surface morphology of (K,Na)NbO3 (KNN) films of thickness 650–750 nm irradiated with 100 MeV Ni ions at different fluences varying from 1 × 1012 to 1 × 1013 ions cm−2. Multiple ion impact induced reduction in crystalline behavior of KNN perovskite is observed as an effect of ion fluence. The films show partially amorphized nature with ion fluence, and are remained in crystalline perovskite phase after irradiation with decreased peak intensities. Quantitative surface roughness and surface scaling study via power spectral density (PSD) analysis were carried out using atomic force microscopy (AFM) micrographs. The root mean square roughness decreased at 1 × 1012 ions cm−2 and thereafter, increased monotonously with increasing ion fluence. The adatoms mobility and coalescence effect might have caused the variation in roughness. From the PSD results, modification of surface morphology of films irradiated at 1 × 1012 ions cm−2 is attributed to the competing mechanisms of viscous flow and evaporation-recondensation processes. At higher fluence, the evolution mechanism of morphology is turned out to be the combined effect of evaporation-recondensation and diffusion processes. The microstructures obtained using scanning electron microscopy are correlated with the AFM results. The dominating processes of irradiation induced modification in the morphology of KNN films are studied in detail, and this study will be useful from both fundamental and applied perspectives.