[en] Using three-crystal X-ray diffractometry angular dependences of intensity of pure diffractive X-ray scattering I(THETA) in Ge and Si monocrystals (with a natural oxide film on the surface) are investigated with the angles of crystal turn from the position of Bragg peak exceeding more than 500 times its half-width. I(THETA) dependence at such large angles of turn (ΔTHETA) possesses information on the change of statistical and dynamical Debye-Waller factors along the crystal depth with the resolution order of 1 nm. In the theory when condidering diffraction averaged according to large number of planes scattering characteristics are used due to weak interaction of X-rays with the crystal. Because of high resolution in the method of asymptotic Bragg diffraction the necessity of by-layer accounting for the variation of scattering characteristics (Debye-Waller factor) and for interplane distance occurred for the first time. General theoretical analysis of the problem is presented. Debye-Waller factors on the crystal-ocide film barrier are restored