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Potential energy threshold for nano-hillock formation by impact of slow highly charged ions on a CaF$_2$(111) surface

A. S. El-Said·W. Meissl·M. C. Simon·J. R. Crespo López-Urrutia·C. Lemell·J. Burgdörfer·I. C. Gebeshuber·HP. Winter·J. Ullrich·C. Trautmann·M. Toulemonde·F. Aumayr
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Abstract

We investigate the formation of nano-sized hillocks on the (111) surface of CaF$_2$ single crystals by impact of slow highly charged ions. Atomic force microscopy reveals a surprisingly sharp and well-defined threshold of potential energy carried into the collision of about 14 keV for hillock formation. Estimates of the energy density deposited suggest that the threshold is linked to a solid-liquid phase transition (``melting'') on the nanoscale. With increasing potential energy, both the basal diameter and the height of the hillocks increase. The present results reveal a remarkable similarity between the present predominantly potential-energy driven process and track formation by the thermal spike of swift ($\sim$ GeV) heavy ions.

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A. S. El-Said, W. Meissl, M. C. Simon, J. R. Crespo López-Urrutia, C. Lemell, J. Burgdörfer, I. C. Gebeshuber, HP. Winter, J. Ullrich, C. Trautmann, M. Toulemonde, F. Aumayr. 2006-09-11. Potential energy threshold for nano-hillock formation by impact of slow highly charged ions on a CaF$_2$(111) surface. https://doi.org/10.1016/j.nimb.2006.12.142

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