Advanced synthesis and characterization of quantum silicon nanowires

The great advances in technology observed in recent decades have only been possible thanks to the miniaturization of transistors, as foreseen by Moore's law. However, the device's miniaturization represents a necessary requirement for progress in general and not only in the electronic field, so much so that it has already affected every branch of science. As well known, this has made the nanoscience and nanotechnology sectors fields of great interest as well as subject of large financial resources by public and private entities. And this trend is constantly increasing. Although the most known and used nano objects are made of metals, silicon nano systems are very promising materials because they can show useful properties like metal particles. Furthermore, silicon until now has dominated the semiconductor industry and is expected to continue to do so in the next few years. This is due to its abundance on earth, its well-known electronic properties, stability, inertness, safety, and cost. About that, Silicon NanoWires (SiNWs) attract great interest due to their very useful electro-optical properties. NWs are elongated quasi one-dimensional (1D) nanostructures with a high aspect ratio (higher than 5:1) whose diameter is of the order of tens of nanometers. This geometry generates peculiar characteristics that significantly differ from the corresponding ones of bulk, making SiNWs promising building blocks for nanostructured devices spanning through several fields, going from microelectronics to photovoltaics, photonics, and sensors. They can be used for light harvesting, to obtain radial p-n junctions in transistors, to amplify SERS signals as nanoresonators and they have several other applications. The purpose of this thesis is to explore the most used synthesis method of SiNWs, observe their morphological and structural properties and study their electro-optical properties. In particular the investigation focuses on electronic phenomena, among which we find the plasmon resonance that these cylindrical-like structures exhibit in the energetic range between UV and Vis. The major scope is to experimentally 5 observe, distinguish and describe the plasmon's resonances through electron energy loss spectroscopy. The general theory is presented although there is no univocal analytical model at the state of the art for the description of the electronic phenomena observed in these nanostructures. The aim is to understand the several aspects not yet fully clear of SiNWs mainly clarifying how the geometry and medium variations influence the electronic features. To support the experimental observations, theoretical simulations based on the finite element method were also performed.