Monte Carlo Simulations of Electron Transport in 3D Solids and Molecular Dynamics Simulations of the Mechanics of 2D materials

The aim of this thesis is the study of electronic transport and mechanical properties of materials using computer simulations. In particular, we dealt with the charge transport in semiconduc- tor and metallic samples and with the peeling of a graphene layer from bulk graphite. The computational methods used to investigate the samples are (i) the Monte Carlo (MC) statis- tical method to simulate the transport of electrons in solids and (ii) the molecular dynamic (MD) approach to study the mechanical characteristics. A relevant part of this thesis is focused on carbon-based material, such as diamond and graphite, and the stable two-dimensional al- lotrope, graphene. The response of diamond and graphite to external electromagnetic pertur- bations, due to e.g. an impinging electron beam, was investigated by calculating reflection electron energy loss (REEL) spectra with MC simulations. By comparing the calculated spec- tra, obtained using different dielectric models, and in-house recorded experimental results, the most effective dielectric model better describing the plasma losses was identified. Moreover, an extension to these models to describe the anisotropic response of graphite to an external electromagnetic perturbation was developed and included in the MC approach. Owing to the central role of carbon for future electronic and technological applications, also its mechanical properties were investigated by means of MD simulations. In particular, the peeling process of a layer of graphene from a bulk of graphite was investigated. This process is exploitable for graphene production and for adhesive applications of this material. Moreover, the MC approach, employed for calculating REEL spectra, was tested and compared to other com- putational techniques based on the solution of the Ambartsumian-Chandrasekhar equations. This consistency test was realized by considering three metals (copper, silver and gold) as tar- get materials. Further studies were carried out on these materials by calculating secondary electron emission yields as a function of the electron beam energy. A remarkable good agreement with experimental data was obtained. The MC approach was also used to investigate the growth of particles in a W(CO)6 layer deposited on a SiO2 substrate upon irradiations by an electron beam in the context of the focused electron beam induced deposition technique. In particular, by applying the MC method, the radial distribution of emitted secondary electrons was calculated and then utilized as input data for further MD simulations. Moreover, the study of electron transport in an organic polymer (P3HT) was performed in order to understand how the molecular ordering affects the secondary electron emission. This aspect is of paramount importance to construct efficient organic electronic devices.