In the search to develop tools that are able to modify surfaces on the nanometre scale, the use of heavy ions with energies of several tens of MeV is becoming more attractive. Low-energy ions are mostly stopped by nuclei, which causes the energy to be dissipated over a large volume. In the high-energy regime, however, the ions are stopped by electronic excitations, and the extremely local (approximately 10 nm3) nature of the energy deposition leads to the creation of nanosized 'hillocks' or nanodots under normal incidence. Usually, each nanodot results from the impact of a single ion, and the dots are randomly distributed. Here we demonstrate that multiple, equally spaced dots, each separated by a few tens of nanometres, can be created if a single high-energy xenon ion strikes the surface at a grazing angle. By varying this angle, the number of dots, as well as their spacing, can be controlled.

The irradiation of SrTiO 3 single crystals with swift heavy ions leads to modifications of the surface. The details of the morphology of these modifications depends strongly on the angle of incidence and can be characterized by atomic force microscopy. At glancing angles, discontinuous chains of nanosized hillocks appear on the surface. The latent track radius can be determined from the variation of the length of the chains with the angle of incidence. This radius is material specific and allows the calculation of the electron-phonon-coupling constant for SrTiO 3 . We show that a theoretical description of the nanodot creation is possible within a twotemperature model if the spatial electron density is taken into account. The appearance of discontinuous features can be explained easily within this model, but it turns out that the electronic excitation dissipates on a femtosecond time scale and thus too rapidly to feed sufficient energy into the phonon system in order to induce a thermal melting process. We demonstrate that this can be solved if the temperature dependent diffusion coefficient is introduced into the model.

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We have investigated the yields and emission velocity distributions of neutral In atoms and In 2 dimers sputtered from a pure indium surface under bombardment with Au m − ͑m =1,2,3͒ projectile ions. It is shown that 5-keV Au 1 bombardment leads to results in full compliance with linear cascade sputtering theory. All polyatomic projectiles are found to generate an additional low-energy contribution to the sputtered flux, which increases with increasing projectile nuclearity and energy and completely dominates the spectra under 10-keV Au 3 bombardment. Analysis shows that this contribution cannot be explained in terms of thermal spike sputtering models. Instead, the results indicate a spike emission mechanism, which closely resembles a free expansion of a supercritically heated subsurface volume.