Swift heavy ion shaping of oxide-structures at (sub)-micrometer scales

100 nm thin NiO-films on oxidized Si-substrates were pre-structured into small platelets of 100-5000 nm side-lengths utilizing the focused ion beam technique. The development of the individual platelets under grazing angle swift heavy ion irradiation was monitored using our "High Resolution In Situ Scanning Electron Microscope" installed in the beam line of the UNILAC ion accelerator at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt/Germany. This instrument allows us to in situ investigate the structural and compositional development of individual objects in the μm- and nm-range under swift heavy ion bombardment, from the very first ion impact up to fluences of some 1015 ions/cm-2. The sample is irradiated in small fluence steps and in between SEM-images (and EDX-scans) of one-and-the-same surface area are taken. Swift heavy ion irradiation at grazing incidence (tilt angle ≥80°) and continuous azimuthal sample rotation results in lateral shrinking and vertical growth of the platelets. At intermediate fluences additional rounding of edges and corners can be observed. At high fluences the deformation finally saturates. The deformation of the platelets is accompanied by huge sputtering of the exposed SiO2-layer, which due to the retracting edges of the platelets results in a pyramidal-like base underneath of the NiO-structures. In our presentation we will illustrate and discuss the reshaping mechanisms and underlying driving forces.