The origin of ferromagnetism in 57Fe ion-implanted semiconducting 6H-polytype silicon carbide

• Published in: Journal of physics. Condensed matter Vol. 18; no. 43; pp. 9881 - 9900
• Main Authors: Stromberg, F, Keune, W, Chen, X, Bedanta, S, Reuther, H, Mücklich, A
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.11.2006; Institute of Physics
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Domain effects, magnetization curves, and hysteresis; Exact sciences and technology; Magnetic properties and materials; Magnetic resonances and relaxations in condensed matter, mössbauer effect; Magnetic semiconductors; Magnetization curves, magnetization reversal, hysteresis, barkhausen and related effects; Mössbauer effect; other γ-ray spectroscopy; Physics; Studies of specific magnetic materials; Moessbauer effect; Ion implantation; Magnetization; Impurity density; Polytypism; Ferromagnetic materials; Silicon carbides; Magnetic hysteresis; XRD; Semimagnetic semiconductors; Conversion electron spectra; Nanoparticles; Rapid thermal annealing; Monocrystals; Transmission electron microscopy; Ferromagnetism; Iron additions; Depth profiles
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/18/43/010

Semiconducting (mostly p-doped) single crystals of the 6H-polytype of D*a-SiC(0001) were implanted with 57Fe ions with a nominal dose of 1.0 X 1016, 2.0 X 1016, 3.0 X 1016 or 2.0 X 1017 cm-2 (high-dose sample p-hd) at 100 or 200 keV ion energy in order to produce diluted magnetic semiconductors (DMSs). After implantation all samples (except p-hd) were subject to rapid thermal annealing at 1000 deg C for 2 min. The structure was investigated by x-ray diffraction, high-resolution cross-sectional transmission electron microscopy and sputter-Auger depth profiling. The magnetic properties were obtained from superconducting quantum interference device (SQUID) magnetometry and 57Fe conversion electron Mossbauer spectroscopy (CEMS) at room temperature (RT) and 4.2 K. Our combined results obtained by several techniques prove unambiguously that ferromagnetism in 57Fe-implanted SiC for Fe concentrations above 3% originates mostly from epitaxial superparamagnetic Fe3Si (and possibly a small fraction of Fe nanoparticles) in the SiC matrix. We find a wide range of blocking temperatures, TB, which start from 400 K for a dose of 2.0 X 1016 cm-2, and shift downwards to ~220 K for 3.0 X 1016 cm-2. For the lowest dose of 1.0 X 1016 cm-2 at 200 keV, we find evidence of ferromagnetism below 20 K via weak magnetic hyperfine interaction. Our measurements suggest that for a maximum Fe concentration in the range of 1-3%, which corresponds to this lowest Fe dose, the possibility exists to obtain a DMS in Fe-implanted SiC, prepared at lower or equal implantation doses.