EFFECT OF SURFACE-ROUGHNESS AND SUBSURFACE DAMAGE ON GRAZING-INCIDENCE X-RAY-SCATTERING AND SPECULAR REFLECTANCE

Grazing-incidence specular reflectance and near-specular scattering we re measured at AI-K, (1.486-keV, 8.34-Angstrom) radiation an uncoated dielectric substrates whose surface topography had been measured with a scanning probe microscope and a mechanical profiler. Grazing-inciden ce specular reflectance was also measured on selected substrates at th e Cu-K-alpha (8.047-keV, 1.54-Angstrom) wavelength. Substrates include d superpolished and conventionally polished fused silica; SiO2 wafers; superpolished and precision-ground Zerodur; conventionally polished, float-polished, and precision-ground BK-7 glass; and superpolished and precision-ground silicon carbide. Roughnesses derived from x-ray spec ular reflectance and scattering measurements mere in good agreement wi th topographic roughness values measured with a scanning probe microsc ope (atomic force microscope) and a mechanical profiler that included similar ranges of surface spatial wavelengths. The specular reflectanc e was also found to be sensitive to the density of polished surface la yers and subsurface damage down to the penetration depth of the x rays . Density gradients and subsurface damage were found in the superpolis hed fused-silica and precision-ground Zerodur samples. These results s uggest that one can nondestructively evaluate subsurface damage in tra nsparent materials using grazing-incidence x-ray specular reflectance in the 1.5-8-keV range. (C) 1998 Optical Society of America.