Diffuse X-ray scattering of amorphous multilayers

We present a new method to measure the diffuse scattering of amorphous multilayers. In contrast to conventional scans, that all take place in the plane of reflection, in this out-of-plane scattering geometry the accessible range in parallel momentum transfer Q(parallel-to) is not limited by the sample surface. We can therefore record data continuously from very small Q(parallel-to) up to Q(parallel-to) congruent-to 2pi/lambda, holding Q(perpendicular-to) constant at the same time. We thereby obtain a scattering factor S(Q) of our sample, that can easily be attributed to diffuse scattering at rough interfaces or amorphous bulk, respectively. In the case of the W/C amorphous multilayer studied here, the data show that the contribution of amorphous scattering is less than 2% up to about Q(parallel-to) = 0.1 angstrom-1, and becomes dominant only in the wide angle region. This allows to draw the conclusion, that the Bragg sheets observed in the vicinity of the specular condition are mainly due to conformal roughness of the multilayer interfaces.