Anomalous ranges of ions implanted into carbon

The range and distribution of ions in matter is of major importance in the modification of materials by implantation. In this investigation the metal vapor vacuum arc (MEVVA) ion source was used as a versatile means of generating beams of metallic ions to implant 26 different species into carbon targets to a dose of 1016 ions cm-2. Vitreous carbon was chosen as the target in order to provide an electrically conducting low Z value material in which no channeling can occur and redistribution of implanted atoms by diffusion is very unlikely. Range distributions were determined by Rutherford backscattering spectroscopy. The charge state distribution for each ion species was monitored and used in conjunction with PRAL and TRIM code calculations to arrive at the theoretically predicted ion ranges. Mean ion energies were between 78 and 192 keV. The results show significant anomalies in range which are not inconsistent with an oscillatory Z1 dependence. For ion species in the region around Z1=75, the ratio of measured to calculated ranges can rise as high as 1.28±0.08, while around Z1=41 this ratio is significantly lower than 1.0. These findings are discussed in relation to other experimental observations and current theoretical ideas. (orig.)