Carbon nitride (CN_x) is a promising compound thin film material for a variety of applications. The nano-structured fullerene-like allotrope in particular exhibits outstanding mechanical proper ties. such as extreme elasticity and toughness. due to a unique microstructure of curved and crosslinked basal planes. Relations between growth. film microstructure and properties of fullerene-like CN_x thin solid films have been studied. The material was synthesised by dual. w1balanced. reactive. direct current. magnetron sputtering at a substrate temperature of 450 °C, to provide for sufficient ad-atom mobility. while the total pressure of an argon and nitrogen mixture was kept constant at 0.4 Pa. to avoid gas-phase reactions. In order to study the effect of ionised species bombarding the growing film, the gas composition was varied from a

N2-fraction of 0 to L while ion energy was set either to 25 or 40 eV. The deposition process was extensively characterised regarding the type and energy of ionised species arriving at the substrate by plasma probe based techniques and energy selective mass spectrometry. It is shown that the ion flux consists predominantly of multi-atomic C_xN_y

(2 ≥ x, y) species and that their total number scales with the N₂-fraction. Elastic recoil detection revealed a nitrogen concentration in the different films of approximately 14 to 18 at%. The nitrngen content exhibits only a minor dependence on the ion energy and gas composition. due to the effect of temperature enhanced chemical desorption of volatile. mainly nitrogen-containing. species from the growth surface. This points towards a rather complicated growth process. where besides the preferential etching by chemical desorption. the structural orientation of multi-atomic species upon incorporation might provide the key for a better understanding of the fullerene-like structure evolution. The material consist of predominantly sp²-coordinated carbon basal planes. which curve and cross-link upon nitrogen incorporation. The radius of curvature and alignment of planes. as well as the crosslinking between them can be controlled by the deposition parameters and define the mechanical properties. as determined by nanoindentation. Fullerene-like CN_x in general deforms predominantly elastic by buckling of sheets. bond deflection and rotation rather than breaking. due to the large inter-planar lattice spacing and the strength of the carbon sp² bond. Fullerene-like CN_x exhibits an extremely low tendency to plastic deformation. usually connected to high­hardness materials. Yet. it has a low to moderate resistance to penetration. which results in a compliant and fracture-to ugh material.