Dislocation image on x-ray topographs within kinematical theory

Abstract

X-ray topographs of perfect crystals and dislocated crystals have been calculated within kinematical theory. The dislocation image on a x-ray topograph is found to be a circle, a ridge, or a trench depending on the type of dislocation and diffraction condition. Its radius or width is comparable to the radius of the first Fresnel zone, r 1 = λx 0 , where λ is the wavelength of the x rays and x 0 is the distance from the crystal to the observation point. The Fresnel model is applied to the x-ray topograph of solid helium. r 1 is estimated to be 2.8 μm. The different contrast of the subboundaries appearing on the x-ray topographs of solid helium is explained in terms of the contrast of the dislocation images based on the calculation.