Structural phenomena in glassy carbon induced by cobalt ion implantation

Glassy carbon (GC) was implanted by 150 keV Co+ ions to the doses of 1×1016 (low dose) and 1×1017 ions/cm2 (high dose). The low dose implantation results in GC structure disordering with formation of amorphous carbon (a-C). Analysis of Rutherford backscattering (RBS) and Raman spectra has revealed 15 at.% of sp3-bonded C atoms in the a-C structure. The in-pane size of sp2 clusters was estimated to be 1.1 nm. On the contrary, the high dose ion implantation results in ordering of the a-C structure. Content of the sp3 atoms in a-C was reduced to about 5% and, respectively, the in-plane sp2 cluster size was increased up to 2.8 nm. Together with the a-C structure ordering the Raman spectra identifies formation of transpolyacetylene (TPA)-like chains after the high-dose Co+ implantation. In parallel, RBS suggests an enhanced diffusion of the implanted cobalt within the modified carbon layer. Correlation of the RBS and Raman results argues a driving role of cobalt diffusion in the TPA-like chains formation and a-C ordering. Great surface roughening observed after the high dose Co+ implantation suggests also the pronounced cobalt clustering causing large flux of “free volume” to the surface.