Study of carbon nitride compounds synthesised by co-implantation of ¹³C and ¹⁴N in copper at different temperatures

Carbon nitride compounds have been synthesised in copper by simultaneous high fluence (10¹⁸ at. cm^-2) implantation of ¹³C and ¹⁴N ions. During the implantation process, the substrate temperature was maintained at 25, 250, 350 or 450 °C. Depth profiles of ¹³C and ¹⁴N were determined using the non-resonant nuclear reactions (NRA) induced by a 1.05 MeV deuteron beam. The retained doses were deduced from NRA measurements and compared to the implanted fluence. The chemical bonds between carbon and nitrogen were studied as a function of depth and temperature by X-ray photoelectron spectroscopy (XPS). The curve fitting of C 1s and N 1s core level photoelectron spectra reveal different types of C-N bonds and show the signature of N₂ molecules. The presence of nitrogen gas bubbles in copper was highlighted by mass spectroscopy. The structure of carbon nitride compounds was characterised by transmission electron microscopy (TEM). For that purpose, cross-sectional samples were prepared using a focused ion beam (FIB) system. TEM observations showed the presence of small amorphous carbon nitride "nano-capsules" and large gas bubbles in copper. Based on our observations, we propose a model for the growth of these nano-objects. Finally, the mechanical properties of the implanted samples were investigated by nano-indentation.