English abstract
Abstract
The effect of structural and chemical disorder on magnetism of Mn-implanted single 3C-SIC(100) and polycrystalline 3C-SiC(111) is investigated experimentally using Rutherford backscattering channeling spectroscopy (RBS/C), X-ray diffraction (XRD), micro-Raman spectroscopy (URS) and magnetometry; and theoretically using ab-initio calculations. Single 3C-Siç epilayer on Si(001) was implanted at room temperature with Mn ions at 80 keV at a dose of 5x1018 cm?. RBS data shows the formation of a highly disordered implanted layer of ~45 nm with a peak Mn atomic concentration of ~1.8% randomly distributed, in agreement with SRIM simulation. The experimental results of magnetic moment per Mn are interpreted by assuming that the implanted layer consists of two respective main regions C-rich and Si-rich as reflected by the presence of a graphitic phase, in which the local atomic environements of Mn is essentially C. Annealing seems to favor Mn substitution into Si sites indicated by the substantial expansion of the lattice constant due to larger covalent Mn radius and high local tensile strain as observed by XRD and URS, respectively. The temperature dependence of magnetization shows an insulating-like character for the as-implanted film and metallic-like for the annealed-implanted film with Curie temperature above room temperature. In addition, the magnetic moment per Mn increases strongly with annealing from 0.23 to 0.65ub. For the polycrsyalline film, different trends have been observed for the implantation and annealing-induced diffusion process. By contrast to single film, the graphitic phase in the as-implanted poly film was found to grow larger and the magnetism was also reduced due to annealing. The experimental interpretation is supported by our ab-initio calculations showing that magnetism in Mn-doped 3C-SiC can be enhanced by carefully growing a structure with Mn in Si sites using C-deficient single SiC host, possibly resulting in localized magnetic interactions.
