The advantages using specially designed X‐ray‐polycapillary microlenses with spot sizes of 50 μm to 200 μm in a commercially available BRUKER D8 DISCOVER GADDS XRD2‐microdiffractometer with a standard sealed X‐ray tube instead of a microfocus source are shown and compared to commercially available pin hole collimators or monocapillary optics. The application of a focusing X‐ray microlens instead of a monocapillary optic with similar spot size leads to an increase of the primary beam flux by a factor of approximately 10 to larger than 100 depending on the additional pinhole used at the exit of the microlens. This additional pinhole can be used to optimize the beam geometry for a better peak profile without additional changes on the setup. Therefore the use of a focusing X‐ray microlens instead of a mono capillary optic reduces the measurement time by at least a factor of 10. A factor up to 200 is possible by simple changing the diameter of the exit pinhole – for the price of a wider peak profile. Due to the similar housing the focusing X‐ray microlens fits in the standard collimator support enabling switching between collimators, mono‐capillaries and the microlens without realignment. This is why no time consuming modification of the microdiffractometer is needed.

Several samples of a-Si02/c-Si(100) with different oxide layer rhicknesses and different silicon surface qualities were examined by x-ray diffraction. The layer thickness as well as the surface roughness and the interface roughness were studied by measuring the reflectivity of the samples near total external reflection. A separate and detailed determination of the interface roughness is obtained by analysing the intensity near the Si(400) reciprocal lattice point. There is a pronounced diffuse scattering parallel to the normal of the interface, the frequently called crystal truncation rods. Both the reflectivity and the isointensitycontours around the (400) reflection demonstrate the presence of an intermediate layer between a-Si02 and c-Si in a crystalline state.

A high-resolution study of X-ray scattering from a laterally structured surface is reported. Total external reflection displays a distinct dip in the reflectivity for incident angles & < 6, (critical angle) and around a Bragg peak a system of truncation rods is found. Generalized Fresnel equations in conjunction with a kinematical theory provide a quantitative explanation of both findings. The method is well suited for characterising modulations on a mesoscopic length scale.

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