Modeling the interaction of light with single-molecule junctions

In the last years, scaling down of conventional CMOS technology slowed down due to several reasons such as increase of power density and appearance of non-idealities. Molecular electronics is one emerging nanotechnology that attracted the attention of the scientific community because molecules represent the ultimate limit of miniaturization and molecular devices are potentially faster than CMOS transistors. However, a crucial problem of this technology is the too low ON current and the great process variability that affects conduction properties. The undeniable potential of molecular electronics pushed a lot of researchers to bet on this field and one of the most theoretically studied topic is the interaction between light and molecular junctions. Studying illuminated junctions is of particular interest for several reasons: using light is possible to characterize process variability, retrieving also additional information on vibrational activity of the junction; light can potentially control transport mechanisms, enhancing or suppressing determined conduction channels; in the optical frequency range Localized Surface Plasmons (LSPs) can be excited in the electrodes, thus adding complexity to the system, but giving also the possibility to exploit other physical phenomena. The purpose of this thesis is to review the literature on this topic, in order to provide to future readers an exhaustive introduction, but also to write in \MATLAB a simulator that implements most used models to describe photo-assisted tunneling (PAT), which are then validated on experimental results and compared with more sophisticated available commercial tools. This simulator derives from EE-BESD, an efficient and effective model for nanocomputing design, that has been modified to implement photo-assisted tunneling. In this way is possible to evaluate photocurrent in molecular junctions allowing a possible fast prototyping of optoelectronic molecular devices. Moreover, the modified EE-BESD, here named EE-BESD-PAT, has the potential to be embedded in a circuit level simulator, thus paving the way to photonic circuits in which some component can be a molecular device.