Effect of hydrogen atom recombination on the characteristics of hydrogen ion implantation

Mechanism of backrelease of hydrogen ions, implantated in crystal solid bodies due to their recombination at the target surface, is investigated generally. Dependences of implantation coefficients η on irradiation dose Φ for 30 keV H1+ ions in W, crystal and polycrystal Ti targets at temperature of 78 K are determined on the basis of the computer numerical solution of the obtained equations. Comparison of the obtained curves with experimental data is conducted. It is pointed out, that calculated dependence η(Φ) for titanium plotted with regard to heterogeneity of H1+ ions intensity distribution over beam cross section agrees well with the experimental one, if we assume, that diffusion mobility of the excessive hydrogen in target near-the-surface layer during irradiation is lower, than outside of this layer. Concentration of excessive hydrogen at titanium surface is small. Recombination energy of excessive hydrogen is E=0.03 eV, activation energy of radiation-stimulated diffusion is Ed=0.09 eV. η value for H1+ ions in W at high irradiation doses (Φ>1018 cm-2) monotonically reduces practically up to zero