Three-dimensional compositional analysis of quantum dots

A simulation program has been set up, which calculates the x-ray profiles of x-ray line scans taken across features of arbitrary structural and compositional geometries embedded in a matrix. The simulated scan intensities are compared to experimental scan intensities, obtained in an analytical scanning transmission electron microscope. The program is applied to calculate x-ray profiles of InAs quantum dots embedded in GaAs and to SiGe quantum dots embedded in Si in a thin foil in cross-sectional [011] projection. With the help of simulations of the indium L line scan intensities for the case of the InAs dots it is demonstrated how sensitively the x-ray profiles depend on the position of the dot in the thin foil. For the case of the SiGe dots, a full quantitative composition analysis is carried out by adjusting the model geometry and model composition distribution until the best match with the experimental germanium K line scan intensity profile is achieved.