A study on the bonding structure and mechanical properties of magnetron sputtered CN_x thin films

摘要

Carbon nitride (CN_x) films have been deposited by reactive (RF) magnetron sputtering, in order to investigate the effect of the energetic ion bombardment during deposition (IBD), in terms of applied V_b, on their bonding structure. Fourier Transform IR Ellipsometry (FTIRE) and X-ray photoelectron spectroscopy (XPS) were used for the investigation of the films bonding structure, while their mechanical properties were evaluated by nanoindentation measurements. At films grown with low negative V_b, (low energy IBD) the N atoms are distributed homogeneously in substitutional sites in graphitic rings through both sp~2 and sp~3 bonds and in linear chains, through sp~2 bonds. In contrast, the high negative V_b (high energy IBD) has been suggested to promote the non-homogeneous N distribution at localized regions in the films where the formation of sp~3 C-N bonds is favored. This behavior was also evidenced by the Cls and Nls XPS peak components, assigned to the sp~3 and sp~2 carbon-nitrogen bonds. Also, high energy IBD films revealed increased values of hardness and elasticity, while hardness values up to 45 GPa were measured at localized regions.