Driving Forces of Surface Patterning and Nanocluster Tailoring with Ion and Laser Beams

Surface ripple formation as well as modification of nanocluster shapes and size distributions have been observed after irradiation with ion or laser beams. Both phenomena occur during far-from-equilibrium processing. In many cases, these effects can be attributed to an either temperature dependent or effective negative surface (interface) tension. Thus, the ripples found after laser irradiation in a PMMA layer are due to the surface temperature undulation caused by spatial-dependent energy dissipation of standing surface plasmon waves in the underlying gold film (thermocapillarity, see [1]). Thermocapillarity has been idendified to be also the main mechanism of swift-heavy-ion-induced shaping of gold nanoparticles in silica into gold rods or even wires [2]. On the other hand, an effective negative surface tension can be found under low-energy ion irradiation of surfaces [3] and ion beam mixing of interfaces [4]. This negative surface tension tends to increase the surface by surface patterning or inverse Ostwald ripening [4]. Here, these and other driving forces will be discussed in a systematic manner.
[1] L. Röntzsch, K.-H. Heinig, J. Schuller, M. Brongersma, Appl. Phys. Lett. 90 (2007) 044105.
[2] K.-H. Heinig and A. Vredenberg, IBMM2006 conference and in preparation.
[3] R. M. Bradley and J. M. E. Harper, J. Vac. Sci. Technol. A 6, 2390 (1988).
[4] K.-H. Heinig et al., Appl. Phys. A 77, 17 (2003).