Dresden 2011 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 19: Silicon and Germanium

HL 19.2: Talk

Monday, March 14, 2011, 14:45–15:00, POT 251

Structural modifications of low energy heavy ion irradiated Ge — •Tobias Steinbach, Jan Wernecke, and Werner Wesch — Institute of Solid State Physics, Friedrich Schiller University Jena

During LEI irradiation of germanium extreme structural changes can be observed. To study the effects and the mechanism of porous layer formation in Ge in more detail samples were irradiated with different ion species, ion energy and angle of incidence. In order to increase the penetration depth, irradiations were performed with ion energies in the range of several MeV. We present ion induced morphological changes in Ge over a wide range of ion fluence N_I, beginning with the amorphization process of c-Ge followed by the formation of voids in the amorphous phase and its transformation into a porous structure at high N_I. Depending on N_I different regimes of porous layer formation are observed (SEM and TEM investigations) and we could demonstrate that the rate of the volume expansion depends only on nuclear energy deposition є_n. However, the formation depth of the voids as well as the shape and the dimension of the porous structure depend on the ion species (chemical properties of the irradiated ions) and irradiation temperature, respectively. In addition, for all perpendicular ion irradiations a formation of a microstructure at the surface occurs whereas for non-perpendicular ion irradiation a plastic deformation, i.e. a surface shift, without a microstructure formation was observed. The effect of plastic deformation will be discussed in detail and provides an explanation for the different surface structures observed for different ion incidence.