Range, distribution, and stopping power of 800-keVN+14ions implanted in metals fromZ2=22toZ2=32

Concentration distributions of 800-keV ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}_{}^{+}{}_{}{}^{}$ ions implanted in metallic targets from titanium ($Z_2=22\mathrm{}$) through germanium ($Z_2=32\mathrm{}$) were determined from $\gamma$-ray-yield distributions using the ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}(p, \gamma ){}_{}{}^{15}{}_{}{}^{}\mathrm{O}$ resonance reaction at 1061.0 keV. Comparison of the first and second moments of these distributions with those predicted by the theory of Lindhard, Scharff, and Schiott (LSS) shows that the measured distributions are generally shallower and narrower. In addition, the measured distributions are strongly skewed such that their concentrations fall off more rapidly for deeper target layers. Values for the third moment of these distributions are also presented. We have attributed the discrepancies between the measured and predicted distributions to the behavior of the electronic stopping power, $S_e$. Values of $S_e$ for the targets studied here were determined by altering the LSS value of $S_e$ for each target by a multiplicative constant such that the predicted projected range is equal to the first moment of the measured distribution. With this adjustment, the predicted range straggling agrees closely with the measured second moments. The adjusted values of $S_e$ exhibit a $Z_2$ dependence which is not accounted for in either the LSS or Firsov pictures of electronic stopping power. Increases in the LSS values by as much as 60% are needed to describe the measured distributions. The $Z_2$ dependence of $S_e$ observed here suggests that there is an oscillatory behavior similar to the $Z_1$ dependence previously reported by Ormrod, MacDonald, and Duckworth, and by Hvelplund and Fastrup.