Ion beam synthesis of Fe nanoparticles in MgO

MgO(001) single crystals were irradiated with 57Fe at an energy of 100 keV and an ion fluence of 6x1016cm-2 at implantation temperatures between 25°C(RT) and 1000°C.
Analysis was carried out by means of CEMS, XRD, RBS and TEM. We found that the implantation temperature plays the important role for the formation of Fe nanoparticles. The fraction of metallic Fe (CEMS Fe0 signal) increases from 28% for RT implantation to 60% for 800°C implantation, while the Fe profile remains unchanged (Rp ¡Ö 50 nm). The nanoparticles formed after 800°C implantation are about 5 nm in size and exhibit fcc-structure with an orientation relationship of Fe(111)/MgO(111) and Fe(220)/MgO(220). The nanoparticles exhibit paramagnetism at room temperature.
At an implantation temperature of 1000°C the Fe implantation profile smears out completely and 92% of the Fe atoms are found in the Fe3+
oxidation state.