Spontaneous growth of the polyhedral fullerene crystals in the supersaturated Ni−C60 composite

Transition metal (e.g., Ni, Co, Ti)–fullerene (C60) hybrid composites represent interesting materials which exhibit unusual properties, e.g., charged transfer, spontaneous self-organization, biocompatibility, etc. It is of basic interest to inspect the properties of the hybrid systems, including their structural integrity and relaxation proclivity.In this work, we report on a slow-paced transformation of the Ni + C60 thin film in ambient atmosphere at room temperature. The Ni + C60 system was synthesized on the Si(1 1 1) wafer as a supersaturated composite of two immiscible phases. Because of high internal stress, the Ni + C60 binary system was disposed to structural relaxation that resulted in a moderate alteration of its surface morphology. In the period of a year, several micrometer-large fullerene particles randomly evolved in a scattered array of about 200 objects per mm2. The particles acquired various polyhedral forms with typical hexagonal, icosahedral and other shapes. The spontaneous formation of fullerene crystals, as a result of stress relaxation of the fullerene-based hybrid system, is a newly observed phenomenon that posses an unusual constructive aspect. This aspect might be interesting for the design of highly-organized functional materials.In this paper the spontaneous transformation of the binary mixture and mechanism of fullerene polyhedra nucleation and growth is discussed.