Influence of surface pre-treatments on the growth of InAs nanowires on Si substrates: experiments and ab-initio simulations

This thesis reports about the influence of silicon surface pre-treatment on the nucleation and growth of indium arsenide nanowires. Several processes are applied on a silicon(111) substrate before nanowires growth takes place through a solid state Molecular Beam Epitaxy system. In particular, the influence of hydrofluoric cleaning, thermal annealing and hydrogen plasma treatment is investigated. The key point in the experimental procedure is that the growth is performed without an external catalyst, so by self assisted and/or selective area epitaxy. Thus, in this framework it is expected that the surface conditions are more relevant then in an catalyst assisted growth. Scanning Electron Microscope and Transmission Electron Microscope are used as main characterization tools for fully grown samples, while Ellipsometry and Atomic Force Microscope are used to analyze surface treatments effects. At the same time, a simulation activity has been carried out: even if several physical models have been elaborated on nanowires nucleation, none of them goes entirely thorough the physical phenomena happening. With this uncertain theoretical background, a first principles approach has been used to better understand how $As$ and $In$ interact on simple possible surface configurations. The aim is to acquire sufficient information to elaborate a kinetic Monte Carlo simulation about the nucleation stage