Effects of ion energy control on production of nitrogen-C₆₀ compounds by ion implantation

Nitrogen-C₆₀ compounds such as azafullerene (C₅₉N) and nitrogen-atom-encapsulated fullerene (N@C₆₀) are produced by implanting nitrogen ions into C₆₀ thin films on a substrate immersed in an electron cyclotron resonance plasma under a mirror magnetic field. Each compound is found to be synthesized, depending on the ion energy provided by the potential difference between the substrate and the plasma. The optimum energy for C₅₉N synthesis is approximately 40-50 eV, and the amount of C₅₉N decreases in an ion energy range larger than 50eV. In contrast, an ion energy larger than 2OeV is required for N@C₆₀ synthesis.