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/cm(3), 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 x 10(14) to 1 x 10(17) ions/cm(2) at room temperature. SIMS was carried out, using Cs+ ions of 8.5 keV as primary ions. Secondary ions detected were C-12(+) and Na-23(+) ions. RES was carried out using 1.5 MeV He ions with a fluence of 10 mu C. 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 RES results were similar to those of SIMS. The correspondence between SIMS and RES profiles suggests that the atomic density of implanted layers increases from 1.5 to 2.2 g/cm(3) at intermediate doses and returns to 1.7 g/cm(3) at a high dose. It was concluded that Na implantation in GC causes the increase in atomic density of GC surface layers. (C) 2000 Elsevier Science S.A. All rights reserved.