Light interaction with nano-materials

Abstract: [i] "There is a crack in everything. That's how light gets in."[/i] With two simple sentences the famous poet Leonard Cohen describes his perception on how light interacts with matter. This thesis work will try to give a more precise and detailed description of the interaction between light and nano-materials that maybe is going to lose some of the magic that poetry has but this will be compensated by the magic of revealing how nature works through the physical phenomena. The system that is studied in the current thesis consists of vertical periodic arrays of core-shell nanowires and the objective of the thesis is to simulate how the light interacts with this structure. The way to simulate the light propagation inside the system is to solve a set of differential equations, the well-known Maxwell equations. By solving these equations it becomes possible to calculate very important physical properties of the nano-structure that are connected to the efficiency of two main applications: the photovoltaic devices and photo-detectors. Moreover, different geometrical properties of the nano-structure (such as the shape of the nanowires, the diameter and the length of the nanowires, the periodicity of the arrays etc.) can be altered and the system can be studied for each different case. The results of the simulations can give useful information in order to find the structure that presents higher efficiency for the applications, but also to obtain a better understanding of the physical phenomena that are connected with light interaction with nano-materials. It becomes obvious that simulations constitute a cost efficient method to investigate which structure has the potential to be used in a future application and to point the direction of a more extensive experimental research for these particular structures. In this way the experimental research becomes more effective and focused, with lower consumption of resources and time.