The main goal in the information technology is to have the possibility of integrating low-dimensional structures showing appropriate optoelectronic properties with the well established and highly advanced silicon microelectronics present technology. Therefore, after the initial impulse given by the work of Canham on visible luminescence from porous Si, nanostructured Si has received extensive attention both from experimental and theoretical point of view during the last ten years. This activity is mainly centered on the possibility of getting relevant optoelectronic properties from nanocrystalline Si, which in the bulk crystalline form is an indirect band gap semiconductor, with very inefficient light emission in the infrared. Although some controversial interpretations of the visible light emission from low-dimensional Si structures still exist, it is generally accepted that the quantum confinement, caused by the restricted size, and the surface passivation are essential for this phenomenon.Here we will review our activity in the field of the theoretical determination of the structural, electronic and optical properties of Si nanocrystals (Si-nc). The present work aims at answer a very important question related to the origin of the enhanced photoluminescence in Si-nc embedded in SiO2. In fact, optical gain has been recently observed in ion implanted Si-nc and in Si-nc formed by plasma enhanced chemical vapour deposition and annealing treatments. We propose, here, an analysis of the experimental findings based on an effective rate equation model for a four level system; moreover looking at our theoretical results for the optical properties of Si-nc we search for structural model that can be linked to the four level scheme. As final outcome, due to the results for the optoelectronic properties of Si-nc in different interface bond configurations, we demonstrate that in order to account for the striking photoluminescence properties of Si-nc it is necessary to take carefully into account not only the role of quantum confinement, but also the role of the interface region surrounding the Si-nc.
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|Data di pubblicazione:||2002|
|Titolo:||Gain theory and models in silicon nanostructures|
|Autori:||Ossicini S.; ARCANGELI C; BISI O.; DEGOLI E.; LUPPI M.; MAGRI R.; DAL NEGRO L.; PAVESI L.|
|Autori interni:||OSSICINI, Stefano |
|Nome editore:||Kluwer Academic Publisher|
|Appare nelle tipologie:||Monografia/Trattato scientifico|
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