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ETUDE DES PHENOMENES DE CHARGE DES MATERIAUX ISOLANTS SOUS FAISCEAU D'ELECTRONS DE BASSE ENERGIE (200 eV - 30 keV)

Abstract : Charging phenomena of insulating materials were studied thanks to a scanning electron microscope which allows the injection of few electrons doses in a large domain of energies and the measurements of the secondary electron emission and the induced current created in the sample holder by the charges generated in the sample. The results shown that the secondary electron emission yield is a very sensitive parameter to characterise the charging state of an insulator and they allowed to class these materials in two groups relatively to their ability to relax the generated charges : · The "trapping insulators", presenting high resistivities, in which the charges are trapped in a stable way during several months. · The "conductive insulators", presenting lower resistivities than the "trapping" ones, in which the charges relaxation occurs more or less rapidly depending on the density and the mobility of intrinsic charges of the material. The results shown that the fundamental parameter controlling the charging kinetic is the current density J0. For "trapping insulators", different regimes (self-regulated, ageing, degradation) function of current density J0 and the domain of energy considered were observed. The study of "conductive insulators" revealed that a permanent current exist in these materials which is characterised by a steady state yield which fix the maximum value of J0 withstanding by a "conductive" without charge accumulation beneath itssurface. These results allowed to define what kind of materials should be used from an electrical angle to reduce indeed to cancel the deviation of electrons due to spacers in field emission displays, and also to introduce a new characterisation process of the internal field created by thermal poling in glasses samples. We also developed a new exploration way of spatial and time evolution of trapped charges in "trapping insulators" thanks to an electrostatic force microscope. Firsts results show the very high stability of trapped charges in these materials.
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Submitted on : Tuesday, January 27, 2004 - 4:00:22 PM
Last modification on : Wednesday, October 14, 2020 - 4:00:11 AM
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Delfin Braga. ETUDE DES PHENOMENES DE CHARGE DES MATERIAUX ISOLANTS SOUS FAISCEAU D'ELECTRONS DE BASSE ENERGIE (200 eV - 30 keV). Matériaux. Université Paris Sud - Paris XI, 2003. Français. ⟨tel-00004341⟩

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