Frequency dependent smoothing of rough surfaces by laser deposition of ZrO2

Abstract

The development of the surface roughness of amorphous ZrO2 layers with different thicknesses, which were laser deposited on nanocrystalline Ag surfaces, was analyzed by atomic force microscopy. With increasing ZrO 2 layer thickness first the surface slightly roughens due to island growth, but above a layer thickness of about 30 nm it continuously smoothens. From the power spectral densities it is clear that the smoothing processes are frequency dependent. First the high-frequency surface features vanish before lower roughness frequencies are decreased. Although the starting roughness is only 1 nm, a ZrO2 layer thickness of about 4 μm is necessary to smooth the long-wavelength surface features. From the decrease of the roughness with ZrO2 layer thickness and the observed final spectral densities, the dominant smoothing mechanisms were identified as downhill currents, probably induced by the energetic ions impinging on the substrate surface during deposition. © 2008 The Author(s).