Röntgenreflektometrie

RöntgenReflektometrie, often abbreviated as XRR, is an analytical technique used to study thin films and interfaces. It utilizes the phenomenon of X-ray reflection at small angles. When X-rays strike a surface at a very shallow angle, they can be reflected. The intensity of this reflected X-ray beam is measured as a function of the angle of incidence.

The resulting XRR spectrum exhibits oscillations, known as Kiessig fringes. These fringes arise from the interference between X-rays reflected from the top surface of the film and those reflected from the interface between the film and the substrate. The spacing of these fringes is inversely proportional to the film's thickness. The overall decay of the reflectivity with increasing angle is related to the roughness of the surfaces and interfaces.

By analyzing the positions and intensities of the Kiessig fringes, along with the reflectivity decay, detailed information about the film's properties can be extracted. This includes the film thickness, surface and interface roughness, and the electron density profile perpendicular to the surface. The electron density profile can further reveal the composition and density of the film.

XRR is a non-destructive technique and is widely applied in various fields, including semiconductor manufacturing, materials science, and nanotechnology. It is particularly valuable for characterizing ultrathin films, multilayers, and layered structures where precise knowledge of layer thickness and interface quality is crucial for device performance. The technique requires relatively simple sample preparation and can be performed using standard X-ray diffractometers equipped with appropriate optics.