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Interaction ions-surfaces : étude de la pulvérisation du fluorure de lithium LiF par technique d'imagerie XY-TOF-SIMS

Abstract : The deposition of energy lost by a fast ionic projectile in the target leads to the ejection of material in the form of atoms or clusters ("sputtering"). The measurements of yields, energy and angular distributions of sputtered particles contribute to the understanding of the initial microscopic processes of damage and defect creation in materials. A new UHV system (AODO) allows measuring the mass distributions and the velocity vectors of each emitted secondary ion by means of time-of-flight and imaging techniques XY-TOF-SIMS ("Secondary Ion Mass Spectroscopy") with well prepared target surfaces. Here, we focus on the sputtering of lithium fluoride (an ionic crystal, a large band gap insulator ≈ 14 eV) by fast heavy ions (≈ 10 MeV/u). As a function of the electronic stopping power Se, two regimes for the evolution of secondary ions yield Y with Se are observed. At low Se (< 8 keV/nm), weak perturbation regime, Y ~ Se^ 2. At high Se (> 8 keV/nm), strong perturbation regime, a saturation (Y = constant) is observed. The experimental data permit also to test the theoretical models existing in the literature (shock wave model, thermal spike, Coulomb explosion ...). It appears that none of these models can correctly describe the ensemble of the experimental observations. However, the Maxwell-Boltzmann distribution describes the energy distributions of the emitted ions. This gives us a possible indication that the processes generating the sputtering could be mainly of thermal origin.
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Submitted on : Friday, October 21, 2011 - 3:11:01 PM
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  • HAL Id : tel-00634553, version 1

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Hussein Hijazi. Interaction ions-surfaces : étude de la pulvérisation du fluorure de lithium LiF par technique d'imagerie XY-TOF-SIMS. Physique [physics]. Université de Caen, 2011. Français. ⟨tel-00634553⟩

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