Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

Ion irradiation of solids can result in self-organization of very regular surface morphologies and in shaping of particles embedded in a solid matrix. Regular chains of nanoparticles can be formed by the decay of nanowires which were synthesized using focused ion beams. This presentation consists of three parts: (i) The self-organization of pattern on elemental semiconductor surfaces under irradiation with ions of 100 eV to a few tens of keV will be reported. It will be proven by comparisons of atomistic computer simulations with experiments that the driving force for this pattern formation is not sputtering, as it was claimed in most published papers so far, but ion impact induced mass drift. Only a minority of former studies came to the same conclusion (see, e.g. [1, 2]), whereas very recently this understanding is more and more convincingly proven [3,4]. (ii) Our progress of shaping of metal and semiconductor nanospheres embedded in silica using swift heavy ions will be reported. Metal spheres can be shaped into rods and quadruples, whereas germanium nanospheres have been shaped into disks. It will be proven that electronic stopping power melts the nanoparticles, and that the volume change upon melting causes the shaping. (iii) Nanowires have been synthesized by FIB implantation, e.g. CoSi2 wires in silicon. By subsequent thermal treatment, nanocluster chains have been formed by a controlled decay of these wires. Computer experiments will show that rather complex nanostructures can be fabricated by this technique.
[1] G. Carter, V. Vishnyakov PRB 54 (1996) 17647.
[2] M. Moseler et al., Science 309 (2005)
[3] S.A. Norris et al., Nature Comm., 2011, Apr12, DOI: 10.1038/ncomms1280
[4] C.S. Madi et al., PRL 106, 066101 (2011)