Apparatus for analysis of a sample includes a radiation source, which is adapted to direct a converging beam of X-rays toward a surface of the sample. At least one detector array is arranged to sense the X-rays scattered from the sample as a function of elevation angle over a range of elevation angles simultaneously, and to generate output signals responsively to the scattered X-rays. The detector array has a first configuration in which the detector array senses the X-rays that are reflected from the surface of the sample at a grazing angle, and a second configuration in which the detector array senses the X-rays that are diffracted from the surface in a vicinity of a Bragg angle of the sample. A signal processor processes the output signals so as to determine a characteristic of the surface layer of the sample.