Absorción y Emisión de Ondas Electromagnéticas en Nanoestructuras de Silicio y Germanio

Abstract

In recent years the nanoscience and nanotechnology development has increased thanks to actual investigations that seek to explain the origin of physical phenomena. In this context, nanostructured materials offer new features and properties that had previously not been discovered, these studies covering thermal conductivity, electron transport, vibrational networks, photoluminescence and others. On the other hand, the increasing human need for technological tools that can provide a better quality of life, makes possible to carry out these studies and apply the obtained knowledge in the development of new technologies such as solid luminescent devices, more efficient solar cells, biochemical sensors, sunscreens. Nanostructured materials such as nanowires, porous structures, nanotubes, quantum dots, thin films, among others, have awakened the interest of scientists which currently conducting researches works to understanding the causes that make possible the presence of new properties which previously was difficult to imagine. In the electronics and communications field semiconductors play a key role, in particular Silicon and Germanium nanostructures because offers interesting properties that promise a significant change in the development of future technologies. This thesis work is a theoretical part research that seeks to help in the clarification of the origin of luminescence in Silicon and Germanium nanowires and porous structures, studying phononic properties (vibrational) during electromagnetic absorption and emission phenomenon in such materials. In this analysis was used the phononic band structure because it provides information of optical and acoustic vibrational processes in nanostructures, and modeling Raman spectrum associated with vibrational excitation during emission and absorption of electromagnetic wave (light) leads to obtain information about structure, size and amorphous contribution in the structure. Using Born model for interatomic potentials, the supercell model and displacement Green's functions to modeling of the phononic band structure and Raman spectrum of Silicon and Germanium nanowires and porous structures, this thesis try to clarify the origin of luminescence in these materials. Results of this study were compared with experimental data obtained by other research groups, founding that results from the model proposed to calculate the phononic band structure and Raman spectrum in this thesis, are quantitative acceptable with experimental data.