A MODEL FOR TRAPPING AND REEMISSION AT HYDROGEN-ION IMPLANTATION

A simple two-parameter model for re-emission at hydrogen ion implantat ion is proposed. The model takes into account diffusion, molecular des orption and hydrogen-defect interaction. Comparison of the model with experiments on hydrogen and deuterium re-emission from stainless steel , molybdenum, tungsten, boron nitride, carbon and pyrocarbon demonstra tes a good agreement. Two fitting parameters are used in the model: (1 ) the recycling factor R = D/K where D is the diffusion coefficient an d K the surface recombination coefficient and (2) the defect factor PH I(d) equal to the maximum areal concentration of hydrogen being able t o be trapped in defects. At high temperature R(T) and PHI(d)(T) follow exponential dependences in accordance to thermal activation of the pr ocesses involved. At low temperatures R(T) and PHI(d)(T) functions dev iate from the exponents, presumably due to domination of some radiatio n enhanced processes. Comparison of our R and PHI(d) values with those available from other experiments shows that the fitting parameters in our model have reasonable values.