I have some silica samples that were implanted with aluminium and bismuth and annealed at 500C. They show emission that I'm fairly sure is silicon dislocation loop emission and I believe the implanted aluminium has created the dislocation loops. However a larger dose of aluminium is not showing a larger intensity in this emission for a 500C anneal. Higher temperature anneals do show an increased intensity for an increase in dose. Does anyone know of any reason why this should be?
Dear Lady, I don`t know the precice values but I guess that the implantation dose is higher than the solubility in dependence on the temperature. This means the excess forms defects. Dislocations can act as cores that collect metal impurities, right? Wkr, M. Herms.
Dear Lady, to the best of my knowledges, dislocation loops formation always takes place during ion implantation in silicon, photoluminescence being observed even for as-implanted samples because of the heating under ion irradiation. The only way to avoid dislocation formation is to do it while substrate is keeping at the -100 degrees by centigrade following by annealing (one-step or two-step: rapid thermal + furnace). So, the observed luminescence always correlates with D1-D4 lines. But together with the formation of the dislocations it often takes plase presence of the another Si defects, such as crystal twins, Si divacancies, vacansion clusters and etc. This defects act as non-radiative centers in Si, quenching luminescence, so increase in the implantation dosage results in increase of the defect density, as a result D1-D4 emission becomes weaker. Higher temperature annealing ~ about 800-900 degrees by centigrade results in recrystallization of Si, decreasing defect density either non-radiative recombination rate.
P.S. If it is not a secret, what is the aim of imlanting silicon with Al or Bi?
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