Silicon ripple structures produced by Xe+ irradiation at medium energies

Silicon ripple structures produced by Xe+ irradiation at medium energies

Grenzer, J.; Hanisch, A.; Facsko, S.; Mücklich, A.; Biermanns, A.; Pietsch, U.

We report on the evolution of wave-like nanopatterns induced by Xe+ ion irradiation at high fluences in an energy range between 5 keV and 70 keV. By means of atomic force microscopy a statistical analysis of the ripple amplitude and wavelength was carried out showing that the periodicity and the amplitude of the rippled structures follow a linear dependence on the energy.
However, the evolution of the rippled patterns clearly differs for the lower and higher ion energies. For energies below 25 keV we observed almost no fluence dependence of the wavelength and amplitude in the investigated range of 1...8·1017 cm-2. But for energies above 25 keV and fluences above 1·1017 cm-2 coarsening was found. At energies larger than 50 keV Xe the ripple structures display a saturation regime for fluences higher than 5·1017 cm-2.
Investigations with cross-sectional high resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy revealed the appearance of Xe filled inclusions at ion energies above 25 keV. This result correlates with an almost stable ratio of the ripple wavelength to the ripple amplitude of about 30 occurring above a threshold fluence of 2·1017 cm-2 and above 25 keV.
These results indicate that there is a certain threshold energy and fluence above which a stable form of the investigated wave-like structure is build up. This is possibly caused by the formation of noble gas inclusions at higher ion energies.

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Publ.-Id: 16458