Trapping of nitrogen in Mo due to defects generated by 50-400-keVH+andHe+ions

Abstract

The trapping property of nitrogen diffusing in polycrystalline molybdenum has been used to study the distribution of defects generated by 50-400-keV ${\mathrm{H}}^{+}$ and ${\mathrm{He}}^{+}$ bombardment. The nitrogen-implanted samples were annealed at $T=600 \mathrm{and} 750\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$. The defect concentrations were studied with different ${\mathrm{H}}^{+}$ and ${\mathrm{He}}^{+}$ doses ranging from ${10}^{14}$ to ${10}^{18}$ ions/${\mathrm{cm}}^{2}$. Increasing the ${\mathrm{H}}^{+}$ and ${\mathrm{He}}^{+}$ prebombardment doses led to a strong increase in the trapping of nitrogen and to the rapid migration of nitrogen atoms to the damaged region before trapping. The nitrogen defect trapping was observed to be very steady. The depth distributions of trapped nitrogen were measured with the ($p,\ensuremath{\gamma}$) resonance-broadening method. The theoretical defect distributions were calculated using Monte Carlo calculations along with the tabulated electronic stopping-power values and good agreement was found between the theoretical and experimental defect profiles. The modal ranges of the 50-400-keV ${\mathrm{H}}^{+}$ and ${\mathrm{He}}^{+}$ ions in Mo derived as indirect by-products of the defect measurements agree with the values obtained through the Monte Carlo calculations, where the tabulated data for electronic stopping is employed, but are 20-40% shorter than those where the electronic stopping according to the theory of Lindhard, Scharff, and Schi\o{}tt is used.