Ion-beam mixing of Fe/Si bilayers

Abstract

The present study focuses on the changes in the structural and magnetic properties in Fe/Si bilayers induced by heavy-ion irradiation (14N, 40Ar, 84Kr, 132Xe, 197Au). With respect to previous work, in which mainly noble-gas ions of low charge state and several hundred keV energy were investigated, several "non-standard" implantation conditions were considered: (1) The use of chemically active ions such as nitrogen demonstrated the competition between nitride formation and ion beam mixing at the interface. During implantation only iron nitrides were formed; even at the highest nitrogen fluence no silicides were formed. (2) For several noble-gas ions, the effects of ion charge and low-energy Ar+ pre-implantation into the Si wafers were studied. While the interface mixing rate does not depend on the ion charge, pre-amorphization of the Si wafer enhances the mixing rate by a factor 2. (3) Finally, experiments were conducted for swift 350 MeV 197Au26+ ions to measure the mixing rate and the magnetic anisotropy in the regime of electronic stopping. A very high mixing rate of 55(5) nm4 was found and attributed to thermal spikes due to the very high energy density of about 40 keV/nm deposited in the Fe/Si couple.

Die vorliegende Arbeit beschreibt Veränderungen der strukturellen und magnetischen Eigenschaften von Fe/Si-Doppelschichten nach dem Beschuss mit schweren Ionen (14N, 40Ar, 84Kr, 132Xe, 197Au). Im Vergleich zu anderen Arbeiten, die sich hauptsächlich mit dem Beschuss durch niedrig geladene Edelgasionen bei einigen 100 keV beschäftigen, werden hier verschiedene Nicht-Standard -Implantationsbedingungen betrachtet. Diese sind: (1)der Beschuss mit chemisch aktiven Ionen (i.e. Stickstoff), der zur Bildung von Eisennitridphasen führt. (2)Beobachtungen zum Einfluss der Ionenladung bei Edelgasen und zum Einfluss der Vorimplantation von Ar+-Ionen niedriger Energie. (3)Experimente mit schnellen und schweren Ionen am Beispiel von 350 MeV 197Au26+-Ionen.