Keywords: nanostructures, quantum dots, Ge islands, anomalous X-ray diffraction, chemical composition, strain distribution, nanotechnology, self-assembly, grazing incidence diffraction, elastic energy, Si(100)
X-ray analysis of strain, composition and elastic energy in Ge islands on Si(001)
X-ray diffraction techniques have been extensively employed to study several structural and chemical properties of self-assembled islands. In this review we discuss recent results on Ge islands grown on Si(001). Grazing incidence diffraction is used to map the strain distribution of Ge pyramids and domes. By tuning the X-ray energy near the Ge K edge – to perform anomalous diffraction measurements – the chemical compositions of both types of islands were obtained. The data allow for direct evaluation of the elastic energy that is one of the crucial components for morphological evolution in this system. We then present a method to map out three-dimensional chemical and structural parameters in Ge domes. Finally, we discuss how such results can be combined to give new insights on growth mechanisms.