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Comparing the short and ultrashort pulsed laser ablation of LiF

Henley, SJ, Fuge, GM and Ashfold, MNR (2005) Comparing the short and ultrashort pulsed laser ablation of LiF JOURNAL OF APPLIED PHYSICS, 97 (2). ? - ?. ISSN 0021-8979

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Abstract

Pulsed laser ablation of LiF was studied using both nanosecond (ns) and femtosecond (fs) pulses at 248 nm. Optical emission from electronically excited Li and F atoms in the plume of ejected material was investigated by wavelength, time and spatially resolved imaging methods. Careful analysis of images of species selected optical emission yielded estimates of the mean velocities of the Li+ ions arising in both excitation schemes (similar to11 and similar to13 km/s, respectively), and highlighted the dramatic effects of radiation trapping, most notably by the reabsorption of Li(2p-->2s) emission by ground state Li atoms in the ns ablation studies. Plumes formed by fs excitation are found to contain a higher fraction of energetic/electrically excited components, including excited F atoms and ions, indicative of an explosive boiling mechanism, whereas the ablation plume resulting from ns ablation is deduced to arise primarily from thermal evaporation of the transiently heated target surface. The amount of target material removed per shot is significantly less in the case of fs excitation. The density (and size) of unwanted droplets in films grown by fs ablation is much smaller than in the case of ns ablation, especially on substrates mounted in an off-axis ablation geometry, implying that hydrodynamic sputtering is much reduced by the use of short pulses and that fs ablation must be the preferred route to forming very thin LiF coatings.

Item Type: Article
Uncontrolled Keywords: Science & Technology, Physical Sciences, Physics, Applied, Physics, SODIUM-CHLORIDE, 248 NM, SINGLE-CRYSTALS, IONIC-CRYSTALS, COLOR-CENTERS, POSITIVE-IONS, FLUORIDE, FEMTOSECOND, IRRADIATION, DESORPTION
Related URLs:
Divisions: Faculty of Engineering and Physical Sciences > Electronic Engineering > Advanced Technology Institute > Nano-Electronics Centre
Depositing User: Mr Adam Field
Date Deposited: 27 May 2010 14:06
Last Modified: 23 Sep 2013 18:26
URI: http://epubs.surrey.ac.uk/id/eprint/191

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