Estimation of the atomic density of amorphous carbon using ion implantation, SIMS and RBS

The atomic density of amorphous carbon thin films, called diamond-like carbon (DLC), has been estimated using the depth distribution of implanted ions as a marker. Ne- or Na-ion implantation was carried out with doses ranging from 5×1014 to 1×1017 ions cm−2 at 50, 100 and 150 keV at ambient temperature. The depth distributions of implanted atoms were measured by means of secondary ion mass spectrometry (SIMS) and Rutherford backscattering spectrometry (RBS). The atomic density of amorphous carbon was estimated from the peak position in the depth distribution of implanted ions using three methods. The first is the difference in the peak positions of implanted ions for the amorphous carbon and glassy carbon with the atomic density of 1.5 g cm−3. The second is comparison of the peak positions obtained by SIMS and RBS measurements. The third is comparison between the empirical depth distribution and the theoretical distribution calculated by the trim code. We conclude that the atomic density of amorphous carbon is 2.0–2.3 g cm−3, and that the combination of ion implantation with a low dose, SIMS measurements and trim calculation is useful in determining the atomic density of amorphous carbon.