LASER-INDUCED FLUORESCENCE STUDY OF C₂ FROM LASER SPUTTERING OF GRAPHITE AND POLYMERS

Abstract
Pulsed laser irradiation of graphite surfaces has been known for some time to lead to the ejection of C, C₂, C₃, etc. neutrals as well as related ions. Since most relevant thermodynamic quantities are known, graphite represents an ideal system for further study. The objectives of this work are two-fold : (1) to compare graphite laser etching results to simple thermal vaporization concepts, and (2) to compare the UV etching of polymers to the results from graphite. We observe that surface morphology and etching rates for graphite indicate a peak surface temperature of ~ 4000K and, hence, can be viewed as a classical vaporization process. The first objective then becomes a question of understanding the energies of molecules, e.g. C₂, in the etch plume in terms of an ~ 4000K surface temperature. The second investigation addresses the question of the specific mechanism facilitating far UV etching of polymers. Both photochemical (electronic rearrangement) and thermal degradation have been suggested in various studies.