Absorption in the visible region of LiNbO3 sequentially implanted with Ag and Cu ions

Ag and Cu ions were implanted sequentially into LiNbO3 at different ratios of Cu and Ag ions, and in two different energy regimes: kiloelectron volt a nd megaelectron volt. Optical absorption spectra were measured in the visib le region at each stage in the process of annealing the sample. For the sam ples implanted sequentially with Ag and Cu ions at the low energy of 20 keV , only one peak appeared between 430 and 630 nm, the position of which depe nded on the ratios of Ag and Cu ions. For the samples implanted at high ene rgies of 3 or 4.2 MeV, two large and distinct absorption peaks were observe d at 480 and 590 nm. When the samples were heated to high temperatures, the peak at 480 nm ascribed to colloids of Ag shifted gradually to longer wave lengths and reached 530 nm, whereas the red shift of the peak ascribed to c olloids of Cu was approximately 15 nm. Cu atoms diffuse out of the doubly i mplanted layer faster and at lower temperatures compared with Ag, even when Cu ions were implanted deeper than the Ag. (C) 2000 American Institute of Physics. [S0021-8979(00)09703-6].