Near-field laser ablation for surface nano-analysis: modeling and experiments
Résumé
Near-field laser ablation of different metal and semiconductor samples was studied with nanosecond (Nd:YAG, 4 ns, 532 nm and 266 nm) and femtosecond (Ti-Sapphire, 100 fs, 400 nm) lasers. The method is based on a near-field enhancement effect obtained by the interaction of laser radiation with a diamond coated silicon tip of the Atomic Force Microscope disposed at a few nanometers above the sample surface. Craters of the order of 100 nm in diameter and a few nanometers in depth were obtained by a careful adjustment of the interaction parameters. Laser ablation efficiency and accuracy were affected by both the sample properties (thermal diffusivity, absorption coefficient, etc.) and the near-field parameters (wavelength, laser pulse duration, tips nature and dimension, etc.).
Two theoretical approaches (the analytical one and the Boundary Element Method - BEM) were applied for modeling the near-field spatial distribution and the enhancement factor. Laser ablation may be regarded as a result of the local near-field heating of a sample surface. Multi-parametric theoretical studies with two-temperature thermal model were performed to understand the effect of the interaction parameters (laser fluence, tip dimensions, near-field spatial distribution, tip-to-sample distance, sample and tip optical features, etc.) on the efficiency of the near-field laser heating and ablation. The results of the near-field numerical simulations, as well as the localized heating and ablation of the gold sample surface will be presented along with the corresponding experimental results. The properties of nanometer scale craters were in a good correlation with the model predictions.
Domaines
Chimie-Physique [physics.chem-ph]Origine | Fichiers produits par l'(les) auteur(s) |
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