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DS: Dünne Schichten

DS 16: Ion beam solid interaction I

DS 16.4: Vortrag

Donnerstag, 30. März 2006, 10:45–11:00, GER 37

Ion-beam induced effects at 15 K in α-Al₂O₃ of different orientation — •W. Wesch¹, C.S. Schnohr¹, E. Wendler¹, K. Gaertner¹, and K. Ellmer² — ¹FSU Jena, Institut für Festkörperphysik — ²HMI Berlin

In order to study the primary effects of ion-beam induced damage formation in sapphire, both implantation and subsequent damage analysis by Rutherford backscattering spectrometry (RBS) were performed at 15 K. We used Ar⁺, K⁺ or Na⁺ ions to investigate the amorphisation of α-Al₂O₃ with either the c-axis (0001), the a-axis (1120) or the r-axis (0112) being perpendicular to the surface. Defect annealing was observed during the RBS measurements with 1.4 MeV He⁺ ions. It can be understood in terms of the electronic energy loss of the He ions which may cause changes in the charge state of the defects thus enhancing their mobility. This results in actual damage recovery or the alignment of the defect structures. The He beam induced defect annealing is taken into account to obtain the undisturbed curves of damage accumulation. The analysis of these curves yields three stages of defect formation. In the first stage isolated point defects are formed. Recombination of point defects is observed when the collision cascades start to overlap. Above a critical concentration these point defects are altered into a second type of defects called clusters. With further increasing ion fluence these clusters exhibit a stimulated growth. A third stage occurs by a saturation of the clusters and their gradual transformation into amorphous material. For the various orientations investigated differences were found, which seem to be caused by a different visibility of the created defects.