Jun 1, 2015

Mn fraction substitutional site and defects induced magnetism in Mn-implanted 6H-SiC


Shallow Mn-implanted 6H-SiC crystal.
Correlation between Mn-substitutional site concentration and magnetism.
Correlation between defects nature surrounding Mn site and magnetism.
Correlation of magnetism in Mn-doped SiC to Mn at Si sites and vacancy-related defect.


n-type 6H-SiC (0 0 0 1) single crystal substrates were implanted with three fluences of manganese (Mn+) ions: 5 × 1015, 1 × 1016 and 5 × 1016 cm−2 with implantation energy of 80 keV at 365 °C to stimulate dynamic annealing. The samples were characterized using Rutherford backscattering channeling spectroscopy (RBS/C), high-resolution X-ray diffraction technique (HRXRD), and Superconducting Quantum Interference Device (SQUID) techniques. Two main defect regions have been identified using RBS/C spectra fitted with the McChasy code combined to SRIM simulations. Intermediate defects depth region is associated with vacancies (DV) and deeper defect (DN) essentially related to the Si and C interstitial defects. The defect concentration and the maximum perpendicular strain exhibit similar increasing trend with the Mn+ fluence. Furthermore, the amount of Mn atoms at Si substitutional sites and the corresponding magnetic moment per Mn atom were found to increase with increasing Mn fluence from 0.7 μB to 1.7 μB and then collapsing to 0.2 μB. Moreover, a strong correlation has been found between the magnetic moment and the combination of both large DV/DN ratio and high Mn at Si sites. These results are corroborated by our ab initio calculations considering the most stable configurations showing that besides the amount of Mn substituting Si sites, local vacancy-rich environment is playing a crucial role in enhancing the magnetism.


1 comment:

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