Application of cylindrical correlation functions to anisotropic scattering from amorphous films

Abstract
The cylindrical pair correlation function has been utilized as a structural tool in the study of anisotropic phase separation in magnetron sputtered amorphous Fe_xGe_100-x films. Anomalous small-angle x-ray scattering (ASAXS) measurements have been performed with the scattering vector both in and oblique to the plane of the films, to search for anisotropy. The cylindrical correlation function has been calculated from these measurements and indicates that there exist well-defined regions of electron density that are elongated (7Å by 12Å) in the direction of film growth. In addition, for a composition of x=6, these regions are well-correlated on a length scale of 27Å for those correlation vectors oriented in the plane of the film surface, whereas the correlations are far weaker and longer in length for those vectors aligned in the direction of growth. These results are in agreement with a previous qualitative mode1 of packed, prolate ellipsoids oriented in the direction of growth.