Density gradient of a mirror-polished rutile (110) surface: X-ray reflectivity evaluation

A realistic rutile (110) surface was studied by means of grazing-incidence X-ray reflectivity measurement using 16.0 keV monochromatic synchrotron radiation. The data were analyzed by considering the density gradient, rather than employing conventional models based on the assumption of uniform layers. It was demonstrated that the low-density layer of approximately 4 nm has several parts, i.e., a Gaussian-like gradient part, an almost linear gradient part and a transition region. The effect of annealing on the density profile is also discussed.