Change in atomic density of glassy carbon by Na ion implantation

A study has been made of the change in atomic density of Na-implanted glassy carbon (GC) with a density of 1.5 g/cm3, comparing the depth profiles measured by secondary ion mass spectrometry (SIMS) and Rutherford backscattering spectrometry (RBS). Na ions of 50 keV were implanted in GC with doses ranging from 5×1014 to 1×1017 ions/cm2 at room temperature. SIMS was carried out, using Cs+ ions of 8.5 keV as primary ions. Secondary ions detected were 12C+ and 23Na+ ions. RBS was carried out using 1.5 MeV He ions with a fluence of 10 μC. SIMS results show that the Na depth profile is Gaussian for a low dose and a Gaussian-like distribution with a hump for intermediate doses. The profile for the highest dose shows Na enrichment at the surface and wide spreading. The RBS results were similar to those of SIMS. The correspondence between SIMS and RBS profiles suggests that the atomic density of implanted layers increases from 1.5 to 2.2 g/cm3 at intermediate doses and returns to 1.7 g/cm3 at a high dose. It was concluded that Na implantation in GC causes the increase in atomic density of GC surface layers.