Master Thesis - Monte Carlo simulation
Due to the ongoing miniaturization of modern semiconductor devices towards low dimensionality and nanometric size, the determination of the structure and chemical composition with a spatial resolution of up to 1 nm3 at a simultaneous investigation volume in the 1 μm3 range is of enormous importance. Modern electron tomography methods are able to provide accurate three-dimensional (3D) measurement of individual basic building blocks as well as their arrangement in space.
We have recently succeeded in comprehensively analyzing the 3D structure of interfaces in a quantum cascade laser regarding morphological nanometric roughness and chemical intermixing. For this purpose, a tilt series of STEM images of the object under investigation was created, which determine the 3D structure through computer- aided reconstruction algorithms. However, the spatial resolution of this 3D reconstruction is not a universal quantity, but is directly related to the transmitted material thickness, including the interface, via electron broadening effects, and further depends on the nature of the material, i.e., electron-matter interaction. Predictions of resolution limits based on simulations of the 3D reconstruction are of enormous importance for the optimization of the experiment and for the accurate interpretation of the results.
The master thesis should address the comparison between interface tomography results and Monte Carlo simulations of the STEM images of variable sample geometry and microscope settings for the subsequent reconstruction. The CASINO software is to be used for this kind of simulation. The results should contribute to a deeper understanding of the resolution limits of tomography, as well as to the identification of suitable experimental conditions, depending on the particular scale of the objects under investigation.
