Impurity-Driven Cone Formation During Laser Sputtering of Graphite

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Science  12 Mar 1993:
Vol. 259, Issue 5101, pp. 1590-1592
DOI: 10.1126/science.259.5101.1590


Sputtering of highly oriented pyrolytic graphite (HOPG) by 248-nanometer laser radiation was studied. Neutral carbon atoms and small clusters were ejected with significantly higher translational energies than were expected from a simple model of thermal vaporization in the absence of a potential barrier. The HOPG also developed a remarkable surface morphology that consists of regular cones and domes. Cone formation appears to be initiated by trace metal impurities that serve as heat shunts in this highly anisotropic material.