Glancing-angle extended x-ray-absorption fine structure and reflectivity studies of interfacial regions

Abstract

Glancing-angle extended x-ray-absorption fine structure (EXAFS) and x-ray reflectivity measurements have been made for a Au surface and several Cu/Al interfaces. The Cu/Al samples consisted of 1000 Å Al on Cu, and the measurements demonstrate the potential of these techniques for determining interface structure and morphology. In particular, distinct differences were observed in both the reflectivity and interface EXAFS signals for Cu/Al samples prepared under different conditions. The information obtained on these samples is compared with information obtained by transmission electron microscopy, Rutherford backscattering, and Auger sputter profiling, and excellent agreement is found. The glancing-angle measurements are distorted by anomalous dispersion effects and a simple analytic correction scheme is presented. This correction has been tested on the Au data and found to work well for the entire range of incident angles. For the Cu/Al interfaces the corrections allowed quantitative analysis of the Cu-Al bonding at the interface, and a substantial difference is found for samples prepared under UHV and non-UHV (${10}^{\mathrm{-}6}$ Torr) conditions. These glancing-angle techniques offer some unique characteristics and are compared to more standard interface studies.