Influence des interfaces rugueux sur la réflexion spéculaire des rayons X

The study of specular reflexion or scattering of soft X-rays from rough surfaces is greatly simplified if we suppose that X-rays are not perturbed inside the matter. This simplifying assumption appears to be valid in the higher range of grazing angles, such as θ>4θ_c where θ_c represents the critical angle of total reflexion. In this case, the Fresnel reflexion coefficient in the specular direction for a plane surface is proportional to 1/sin ⁴θ; moreover we can account for the roughness of the surface, in an equivalent way, either by using the well-known attenuation factor exp{−16π²/λ² 〈z ²〉 sin²θ} or by replacing the rough surface with a transition layer in which the variations of the refractive index agree with the error function. But, in the smaller-angle range, θ< θ_c, the second model seems to be more convenient. With models with one or two rough surface layers, an attempt is made to find an interpretation of the reflexion curve obtained with 1.5405 Å X-rays on a sample of germanium monocrystal.