During swift heavy ion irradiation of amorphous germanium a strong swelling, i.e. morphological changes, of the amorphous surface layer (thickness ~ 3.1 micrometer) accompanied by an enhanced plastic flow process was shown recently. To study the effect of high electronic energy deposition S_e on amorphous and crystalline Ge in more detail samples were irradiated with 89 and 185 MeV Au ions with different angles of incidence. Under these irradiation conditions S_e varies between 14.0 and 38.6 keV nm^-1. In order to quantify the swelling, one half of the sample was masked with an aperture to inhibit ion penetration and to enable the comparison of irradiated and unirradiated material.

We demonstrate for all used irradiation conditions that for amorphous Ge a strong swelling of the irradiated material can be observed, which depends linearly on the ion fluence as well as on S_e. Furthermore, for crystalline Ge only at high ion fluences the formation of a buried porous layer was determined. XSEM investigation revealed the formation of randomly distributed voids only in the initially amorphous Ge surface layer. With increasing ion fluence the voids grow in size and the layer transforms into a sponge-like porous structure with irregularly shaped voids, thus, establishing that swelling was a consequence of void formation. Moreover, an electronic energy deposition threshold has been estimated at which the swelling, i.e. the formation of voids, begins. This threshold value enables also an explanation of the buried porous layer formation observed in crystalline germanium. Work supported by BMBF and DAAD.

 

Tobias Steinbach*, Friedrich-Schiller-Universität Jena Institut für Festkörperphysik, Max-Wien-Platz 1, 07743 Jena, Germany, Germany
Werner Wesch, Friedrich-Schiller-Universität Jena Institut für Festkörperphysik, Max-Wien-Platz 1, 07743 Jena, Germany, Germany
Claudia S. Schnohr, Friedrich-Schiller-Universität Jena Institut für Festkörperphysik, Max-Wien-Platz 1, 07743 Jena, Germany, Germany
Raquel Giulian, Australian National University Research School of Physical Sciences and Engineering, Canberra 0200, Australia, Australia
Patrick Kluth, Australian National University Research School of Physical Sciences and Engineering, Canberra 0200, Australia, Australia
Leandro L. Araujo, Australian National University Research School of Physical Sciences and Engineering, Canberra 0200, Australia, Australia
David J. Sprouster, Australian National University Research School of Physical Sciences and Engineering, Canberra 0200, Australia, Australia
Aiden P. Byrne, Australian National University Research School of Physical Sciences and Engineering, Canberra 0200, Australia, Australia
Mark C. Ridgway, Australian National University Research School of Physical Sciences and Engineering, Canberra 0200, Australia, Australia

*presenting author