Abstract
Ferromagnetic Si 1-x Mn x was prepared by implanting B + and Mn + ions in sequence into p-type Si(100) at room temperature and post-annealing at 700-900 °C. Superparamagnetic nano-sized silicide precipitates, 10-27 at.% Mn, were found near the surface of all Si 1-x Mn x samples. Annealing at 800 °C or below leads to the formation of a thin Si(Mn) layer, with 1.1 at.% Mn, ∼180 nm beneath the surface, giving rise to ferromagnetism with a Curie temperature above 250 K. The high-temperature ferromagnetism is attributed to the indirect exchange mediated by localized carriers in the impurity states. The Mn content of 1-1.5 at.%, having been separately reported to show room-temperature ferromagnetism several times by different groups, seems meaningful for Si-based diluted magnetic semiconductors (DMS). Possible extensions of our work presented here are elucidated. © IOP Publishing Ltd.