Imperfect oriented attachment: Direct activation of high-temperature ferromagnetism in diluted magnetic semiconductor nanocrystals

We report on a simple nonequilibrium solvothermal synthesis of Co-doped ZnO diluted magnetic semiconductor (DMS) nanocrystals. The crystal growth mechanism of imperfect three-dimensionally oriented attachment was revealed by the high-resolution transmission electron microscopy. The shallow donorlike defects as the legacy of aggregation-based growth were responsible for the observed high-temperature ferromagnetism (FM), further verifying the recent proposal. The solvothermal-treated strategy may not only offer an independent approach to directly tailor magnetic properties of advanced materials and devices at the nanoscale but also contribute to the sound understanding of the microscopic mechanism behind FM in DMSs. (c) 2006 American Institute of Physics.