Abstract
A phase retrieval method for noncrystalline surface layers that involves intensity modulation of the specular reflection under the excitation of a Bragg reflection was applied to a Si(001) single crystal covered with a native oxide layer of a few nanometers thickness. The phases and moduli of the amplitudes of the scatterings from the native oxide layer were uniquely retrieved at three points on the specular truncation rod. The phases and moduli obtained experimentally were consistently explained by a model of a Si(001) single crystal covered with a uniform oxide layer with a rough surface.