INTERACTION OF F-N-CENTERS WITH GOLD NANOCRYSTALS PRODUCED BY GOLD ION-IMPLANTATION IN MGO SINGLE-CRYSTALS

Gold ions were implanted at an energy of 1.1 MeV into (1 0 0) oriented MgO single crystals. In order to form gold colloids from the as-impla nted samples, the samples were annealed in three different kinds of at mospheres: (1) Ar only, (2) 10% H-2 + 90% Ar, and (3) 10% O-2 + 90% Ar . Annealing over 1200 degrees C enhanced the gold colloid formation as is evident from the appearance of the surface plasmon resonance band of gold. The surface plasmon bands of samples annealed in three kinds of atmospheres were found to be at 560 nm (Ar only), 524 nm (H-2 + Ar) , and 560 nm (O-2 + Ar). The band positions of surface plasmon can be reversibly changed by an additional annealing. Fe3+ impurities in the MgO samples are utilized to monitor the degree of reduction or oxidati on of the samples due to annealing. From the absorption measurements o f Fe3+ band, the diffusion constants of F-centers were obtained, We fo und that the shifts of the surface plasmon bands are correlated with t he F-center concentration and that the F-n-center (aggregates of F-cen ters) is responsible for the shifting of the surface plasmon bands. We propose a model to explain the shift of surface plasmon band. (C) 199 8 Published by Elsevier Science B.V. All rights reserved.