GRAZING INCIDENCE X-RAY DIFFUSE SCATTERING FROM SURFACES AND INTERFACES. B. K. Tanner, I. Pape, T. P. A. Hase and M. Wormington*, Physics Department, Durham University, Durham DH1 3LE, U.K., *Bede Scientific, Lindsey Park, Bowburn, Durham, DH6 5PF, U.K.

Grazing incidence specular and diffuse X-ray scattering measurements from surfaces and interfaces are described. Conventional source and synchrotron radiation techniques are contrasted and the application of anomalous dispersion to highlight interfaces between materials close in the periodic table is described. The data are interpreted using novel computer simulation code, running on a PC, based on the distorted wave Born approximation theory of scattering from fractal interfaces.

Analysis of the scatter from polished surfaces of the glass ceramic Zerodur shows that the diffuse scatter is much less than that predicted from the surface roughness deduced from the specular reflectivity. Inclusion of a gradient in electron density at the surface gives excellent agreement between simulated and experimental data for all scattering vectors used. Studies of surfaces of GaAs polished using different chemical and mechanical techniques showed similar surface composition grading, with significant electron density variation over a period of months after polishing. Roughness , lateral correlation length and fractal parameter h of the interfaces in Co-Cu multilayers have been measured and correlated with giant magnetoresistance (GMR) data. A linear fall in correlated roughness with GMR is found in multilayers grown on sapphire by MBE. Multilayers grown on copper silicide buffers on silicon show large values and stepped interfaces which result in characteristic diffuse scatter. Simulation and experiment are in excellent agreement over a wide range of X-ray optical conditions. Sputtered multilayers grown on silicon show markedly less conformality in the roughness than MBE-grown layers.