Investigations on anisotropic surface roughness of thin films using X-ray specular reflection topography

Abstract

Optically flat Pd/Nb and Pd thin films, grown by the ordinary DC magnetron sputtering, are examined using a specular total reflection X-ray technique. Microfocus laboratory sources and synchrotron radiation are employed. X-ray reflection images show a directional dependence of surface roughness, when the sample position relative to the incident X-ray beam is subject to an azimuthal rotation around the crystal surface normal. The origin of this surface anisotropy is found to be closely related to the motion of the substrates during the crystal growth. The variation on the surface roughness due to hydrogen absorption is also investigated. It is shown that this specular reflection technique turns out to be a simple non-destructive method to display with ease the direct vision of anisotropy of surface roughness for thin films.