Some Observations on the Interference Fringes Formed by X Rays Scattered from Thin Films

Abstract

Several aspects of x-ray scattering from thin films have been studied. A relation is presented which correctly gives the positions of the interference maxima in the scattered radiation and is shown to reduce to the Kiessig (specular) interference equation under the appropriate conditions. In particular, it is shown experimentally that the phase shift suffered by the x-ray beam upon scattering in the nonspecular directions is the same as the phase shift suffered in the specular scattering. The observed low-angle cutoff of the scattered interference fringe pattern is also predicted. A previously reported variation in the shape of the specularly reflected beam is discussed and evidence is presented which indicates that this variation is a result of the angular divergence of the incident x-ray beam.