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Phenomenology and applications of three-dimensional plasma-sheath-lenses (PLASMA-SHEATH-LENS)
Date du début: 1 août 2007, Date de fin: 31 juil. 2009 PROJET  TERMINÉ 

Plasma processing technologies are based on radial-assisted ion-induced surface modifications where positive or negative ions accumulate energy within the sheath then strike the surface with certain energies and incidence angles. Due to the limited size of the treated electrodes the sheath is a two or three- dimensional structure. We have demonstrated very recently that the sheath forming to conducting electrodes that interface insulators exhibit very interesting focusing properties including the formation by discrete focusing of a passive surface (no charge impact) and the existence of some modal lines (modal focusing).This charge kinetics is very attractive because the passive surface correlates the asymptotic distribution of the potential with a step function for the ion flux. The modal focusing effect is very sensitive to small changes in the sheath structure so it can be used to investigate sheath modifications by addition of electronegative gases, dust particles, etc. The aim of this project is to further investigate the phenomenology and propose new applications related to the plasma-sheath-lens focusing effects.The central idea is that one can get on a small surface a unique pattern resulted by competition between sputtering (and/or) deposition, pattern that can be used as a fingerprint of the entire plasma-sheath-surface system. Our goal is to investigate in detail, by simulation and experiment, using a three- dimensional approach, both the sheath structure and charge-induced surface modifications.The main aspects targeted include negative ion detection, improvement of ion dose uniformity in plasma immersed ion implantation, estimation of etching yields, ion beam extraction, plasma monitoring, negative sheath and Bohm criterion in multiple ion spices plasmas. We expect to be able to simulate and then realize customized plasma-sheath-lenses that address particular needs related to applications and basic understanding.