Ion-assisted deposition of carbon-transition metal nanocomposite thin films

Ion assistance during film growth provides unique opportunities (i) toinfluence the film microstructure due to energy transfer and (ii) impose the directionality due to momentum transfer effects. Ion induced displacements occur in a thin surface layer of the growing film where they increase the atomic mobility. Therefore the ion assistance can be used to control the phase separation occurring during co-deposition of materials with low miscibility, and hence the resulting nanocomposite morphology. As the structure at the nanoscale determines the properties at the macroscale, the control over the microstructure is a key issue in nanomaterials science. In this contribution, a comparison of the growth-structure relationship of carbon-transition metal (Ni, Cu) nanocomposite films grown by ion beam assisted deposition (IBAD) and pulsed filtered cathodic vacuum arc (PFCVA) is reported. The formation of elongated nickel nanoparticles is strongly promoted by temperature and ion beam assistance. Moreover, the metal nanocolumns no longer align with the advancing surface, as in the case without ion assistance, but with the incoming ions. Although the energy in PFCVA is carried by film forming ions themselves while for IBAD it is delivered by a separate ion beam, both deposition techniques show a window of deposition conditions where the ion assistance leads to the formation of regular nanopatterns. As the dominating factors (ion induced ballistic effects) are of physical origin, this approach might be applicable to other materials systems with limited solubility.
Acknowledgements: Funding by the European Union, ECEMP-Project D1, "Nanoskalige Funktionsschichten auf Kohlenstoffbasis", Projektnummer 13857 / 2379, and by DEEWR, Australia, in the framework of Endeavour Research Fellowship (Contract No. 837_2008), is gratefully acknowledged.