Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

In a previous paper [1] we have reported on the shaping of rectangular NiO-platelets (thickness: 100 nm , side-lengths: 100 – 5000 nm) on oxidized Si-substrate (250 nm SiO2) by swift heavy ion (SHI) irradiation under grazing (5o – 10o) and azimuthally rotating incidence. At low fluences ion hammering resulting in lateral shrinkage and vertical growth dominated the reshaping process. At higher fluences (the earlier the smaller the initial lateral size of the platelet) curving of edges and corners and finally saturation of deformation occurs due to the influence of surface tension. The deformation of the NiO is accompanied by huge sputtering and creeping of the exposed SiO2-layer. Especially the latter affects the NiO deformation in the interfacial region.
In the present report we will compare those results with similar experiments on thin ZnO- and TiO2-platelets on oxidized Si. As in case of NiO also here pre-structuring of the thin oxide-films was done with the focused ion beam (FIB) technique. The development of the platelets under 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 [2]. This instrument allows us to in-situ monitor the morphological and compositional modification of individual objects in the micro- to nanometer-range under swift heavy ion bombardment, from the very first ion impact up to fluences of some 1015 cm-2. The irradiation can be carried out at any incidence angle between 0o and 90o and under stepwise or continuous azimuthal rotation of the sample.
In contrast to NiO the deformation rate of ZnO and TiO2 is smaller by more than a factor of 5. While in case of ZnO similar objects are formed compared to our previous study on NiO, the TiO2 also shrinks laterally, but remains as an almost flat layer on the underlying pyramidal basis formed by sputtering of SiO2. The results will be discussed regarding the mechanical, thermal and electrical properties of the materials.
Acknowledgement
We thankfully acknowledge the help of D. Severin, M. Bender and C. Trautmann from GSI during the experiments and "Deutsches Bundesministerium für Bildung und Forschung" for project funding.
References
1. R. Ferhati,S. Amirthapandian, M. Fritzsche, L. Bischoff, W. Bolse, REI 19, Nucl. Instr. Meth. B, (2018) in press. 2. S. Amirthapandian, F. Schuchart, and W. Bolse, Rev. Sci. Instrum. 81, (2010) 33702.