Optical changes in silica by sequential ion implantation of Au and Ag

抄録

In this work we have studied changes in the optical properties of silica after high dose spot-by-spot implantation of 1.450 MeV Au, 0.785 MeV Ag, and high temperature annealing, and the effect of the sequence of annealing and implantation. Using a 2 mm diameter aperture, each spot was implanted to desired dose before moving the spot by 0.5 mm increments laterally across the sample so that a 1 cm² area was uniformly implanted. Total implantation fluences of Au, Ag, and (sequentially) Au + Ag were varied from 1.5 x 10¹⁶ /cm² to 1.4 x 10¹⁷ /cm², and the implanted area was studied before and after annealing using optical absorption photospectrometry and by Rutherford backscattering spectrometry (RBS). We found that a secondary implantation by Ag ions (after Au implantation & nanoparticle formation) facilitates substrate healing upon a second annealing step, returning the index of refraction to the value near to that of a pristine substrate, and Au nanoparticle absorption to that predicted by Mie theory. Changing the processing order of annealing (annealing after both Au and Ag implantations were completed, rather than between the Au and Ag implantations) eliminated Ag nanocluster formation, returned the substrate index of refraction to its pristine value, and caused Au nanocluster formation to initiate at lower annealing temperatures.