Ion-guided microstructure evolution of carbon-nickel nanocomposite films during ion beam assisted deposition: 3D sculpting at the nanoscale

Ion assistance during film growth provides unique opportunities to influence the microstructure due to energy transfer and imposed directionality. During nanocomposite film growth at low temperatures (RT to 300°C), phase separation occurs at the growing film surface. A systematic study of ion irradiation as a pure energy and momentum transfer agent in the context of surface diffusion assisted phase separations is, however, lacking. Here the influence of low energy (50-140 eV) assisting Ar+ ion irradiation on the morphology of C:Ni (~ 5 at.% Ni to ~ 50 at.% Ni) thin films will be reported. Two types of ordered nanostructures, - tilted columns and self-organized 3D patterns with well-defined surface periodicity - are identified and characterized. For a given composition of the depositing flux, the transition from the column to the self-organized 3D pattern formation regime as a function of the assisting ion energy is demonstrated. Tilt angle and diameter of the nanocolumns are controlled by the deposition parameters. Complex secondary structures like chevrons with partially epitaxial junctions are grown by sequential deposition. The effects of the metal content and the assisting ion current on the self-organized 3D patterns and surface periodicity are studied. Mechanical and tribological properties of both types of nanostructures will be reported.

Acknowledgement: The work is funded by the European Union, LEI Folgeprojekt D1, "C-basierte Funktionsschichten für tribologische Anwendungen (CarboFunctCoat)", No. 7310000211.