ON-LINE Masters Defense: Tobias Særkjær

Morphologies of Selective Area Grown Nanowires

Simulations of materials with properties interesting for applications in quantum computing has so far been mostly focused on understanding the electronic structures and associated phenomena in the presence of interfaces. While this is indeed of utmost importance, the strict requirements for uniformity in nanowire (NW) structures emphasizes the importance of understanding and control of morphological parameters in NW systems.
This thesis shows modelling of nanowire morphologies from selective area growth (SAG) in two different "domains". First, the overall distribution of crystal volume is examined by way of coupled diffusion equations describing the steady state adatom density during growth, including incoming beam flux, incorporation and desorption. The model reliably reproduces the trends from analyses of final mass distribution in experiments. Second, the shaping of crystal volumes is modelled by way of constrained Wulff shaping (CWS), equilibrium shapes minimizing the surface energy under constraints imposed by the chosen SAG lithography. Finally, in the last section we examine the changes in chemical potentials associated with growth of crystal volume for a generalized shape, setting up the framework for dynamic modelling of crystal growth.