TEM-characterization of magnetic samarium- and cobalt-rich-nanocrystals formed in hexagonal SiC

Using analytical transmission electron microscopy techniques, nanocrystals embedded in 4H–SiC are studied which formed after high dose samarium (Sm), cobalt (Co), and Sm-and-Co-ion implantations and annealing. SmSi2, Sm5C2, Co2Si and SmCo-rich nanocrystals have been identified in terms of their crystallography, shape, strain, size, and orientation relationship to the matrix. It is shown, moreover, that cluster creations of foreign atoms (nanocrystals) and of vacancies (voids) are connected and their sizes increase with implantation dose. Carbon onions surrounding the nanocrystals have been found and this carbon excess has been interpreted as a consequence of preferred formation of foreign atom-silicide nanocrystals. For the case of Co implanted 4H–SiC, Lorentz microscopy has been applied revealing both non-magnetic and single-domain ferromagnetic nanocrystals. r 2004 Elsevier B.V. All rights reserved. PACS: 36.40.Cg; 75.75.+a; 68.37.Lp