Several x-ray diffraction methods are presented to determine the local chemical composition of self-assembled islands and to discriminate them from strain gradients. Two different routes are followed: in the first approach, the scattered intensities are simulated using numerical fitting to a suitable structure model for the islands (indirect methods). In the second one, the structural data are directly derived from the experimental ones. This direct approach is based on the so-called iso-strain scattering method and/or on the anomalous diffraction technique, which uses the strong enhancement and suppression of the scattered intensity close to the absorption edge of one of the chemical elements in the island. We show that for Ge dome-shaped islands the different techniques give similar results.
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