Soft x-ray scattering from rough surfaces: experimental and theoretical analysis.

Specularly reflected and scattered radiation was measured at lambda = 50, 100, 200 A from artificially roughened flat mirrors and from thick vacuum evaporated Au samples. The results of the roughened samples are in reasonable agreement with Beckmann's scalar theory using an exponential autocorrelation function. The angle-dependent scattering distributions at different angles of incidence and different wavelengths are described with a unique mean roughness and autocorrelation length. Some small discrepancies remain because the scalar theory does not take into account the optical constants of the scattering surface. The use of vector theory in its simplest analytical form is not successful; however, it provides a means to qualitatively correct the scalar theory for the influence of the actual optical constants in agreement with our experiments. The thick Au films are roughened by surface crystallization and yield completely different scattering distributions. These results could not be fitted to scalar theory, either with an exponential or a Gaussian autocorrelation function.