Ar ion effect on mechanical properties of carbon nitride films prepared by ion-beam-assisted deposition

Carbon nitride (CN) films have been prepared by ion-beam-assisted deposition. Carbon was evaporated by electron beam and N and Ar ions were bombarded simultaneously from one ion source. To clarify the role of Ar ion bombardment, CN films were prepared on Si(001) Substrates. The Ar/N-2 ratio wits varied between 0 and 2. Mechanical properties were measured in terms of hardness, friction coefficient and wear. The films prepared under Ar/N-2 ratio of I showed the highest hardness and best wear resistance. The XPS analysis of the CN films showed two distinct bond components that correspond to C-N sp(2), and C-N sp(3) bond. CN films with Ar/N-2 ratio of 1.0 mainly consisted of C-N sp(2) bond structure. TEM observation, shows that the simultaneous bombardment of Ar ion promotes two-dimensional network of C-N chemical bonds that are formed similar to stacked graphite-like sheets with a columnar alignment perpendicular to the substrate surface (nanotube-like structure). This is advantageous from the mechanical strength point of view, however, excess bombardment of Ar ion prevents the formation of nanotube-like structure. The variation of the mechanical properties is due to the structural change obtained by simultaneous bombardment of Ar ions.