Surface Modifications with Highly Charged Ions
The deposition of potential energy into solid surfaces induces modifications in the morphology and/or in the electronic structure of the irradiated surface. These surface modifications depend strongly on the electronic excitation induced by the highly charged ion and depends strongly on the charge state of the ion.
The knowledge about the amount of deposited potential energy can be used to precisely modify surfaces with highly charged ions. Surface modification in this case is the creation of an electronic or topographic surface structure with a size in the nano-meter range. The electronic and structural properties of such a structure depend on the amount of deposited energy as well as on the characteristic properties of the sample material. For metallic surfaces no nano-structures due to HCI impact have been reported, whereas insulating materials can efficiently be structured. This is due to the localization of the electronic excitations upon HCI impact and the so-called electron-phonon-coupling, which is assumed to be strong in many insulators. The different channels for energy dissipation and conversion into crystal lattice vibrations (phonons) in different target materials are the reason for the large differences in the size, shape and properties of HCI induced nano-structures.
Examples of surface modifications induced by the impact of single highly charged ions:
|Graphite||CaF2 (111)||etched structures in CaF2 (111)||KBr||Carbon nano membranes|
STM image of a HOPG surface bombarded with Ar8+ ions. A nano-structure with a size of about 5nm is shown.
Atomic force microscopy image of a CaF2(111) surface after bombardment with highly charged ions. The potential energy exceeds 20keV, i.e. nano-hillocks are formed due to single ion impacts.
Atomic force microscopy image of a CaF2(111) surface after bombardment with Xe15+ ions. Only after wet chemical etching the triangular shaped pit structures can be observed at the ion impact sites.
Atomic force microscopy image of a KBr(001) surface after irradiation with highly charged ions. The black dots are pits with a depth of exactly one monolayer.
Helium ion microscopy image of a 1nm thin carbon nanomembrane after irradiation with Xe40+ ions. The bright stripes are due to a thicker support mesh. The dark spots are ion-induced pores.
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- R. A. Wilhelm, E. Gruber, R. Ritter, R. Heller, A. Beyer, A. Turchanin, N. Klingner, R. Hübner, M. Stöger-Pollach, H. Vieker, G. Hlawacek, A. Gölzhäuser, S. Facsko, and F. Aumayr, Threshold and efficiency for perforation of 1 nm thick carbon nanomembranes with slow highly charged ions, 2D Mater. 2, 1 (2015).
- Ritter, R., Wilhelm, R.A., Stöger-Pollach, M., Heller, R., Mücklich, A., Werner, U., Vieker, H., Beyer, A., Facsko, S., Gölzhäuser, A., Aumayr, F., Fabrication of nanopores in 1nm thick carbon nanomembranes with slow highly charged ions, Applied Physics Letters, 102, 063112 (2013).
- Ritter, R., Shen, Q., Wilhelm, R.A., Heller, R., Ginzel, R., López-Urrutia, J.R. Crespo, Facsko, S., Teichert, C., Aumayr, F., Novel aspects on the irradiation of HOPG surfaces with slow highly charged ions, Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 315, 252 (2013).
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- El-Said, A.S., Heller, R., Meissl, W., Ritter, R., Facsko, S., Lemell, C., Solleder, B., Gebeshuber, I.C., Betz C., Toulemonde, M., Möller, W., Burgdörfer, J., Aumayr, F., Creation of nanohillocks on CaF2 surfaces by single slow highly charged ions, Physical Review Letters, 100, 237601 (2008).
- Facsko, S., Heller, R., El-Said, A.S., Meissl, W., Aumayr, F., Surface nanostructures by single highly charged ions, Journal of Physics D: Condensed Matter, 21, 224012 (2009).
- Heller, R., Facsko, S., Wilhelm, R.A., Möller, W., Defect mediated desorption of the KBr(001) surface induced by single highly charged ion impact, Physical Review Letters, 101, 096102 (2008).