Photoluminescence from Au ion-implanted nanoporous single-crystal 12CaO•7Al2O3

Implantation of Au+ ions into a single crystalline 12CaO center dot 7Al(2)O(3) (C12A7) was performed at high temperatures with fluences from 1x10(14) to 3x10(16) cm(-2). This material is composed of positively charged sub-nanometer-sized cages compensated by extra-framework negatively charged species. The depth profile of concentrations of Au species was analyzed using Rutherford backscattering spectrometry. The measured optical spectra and ab initio embedded cluster calculations show that the implanted Au species are stabilized in the form of negative Au- ions below the fluences of similar to 1x10(16) cm(-2) (Au volume concentration of similar to 2x10(21)cm(-3)). These ions are trapped in the cages and exhibit photoluminescence (PL) bands peaking at 3.05 and 2.34 eV at temperatures below 150 K. At fluences exceeding similar to 3x10(16) cm(-2), the implanted Au atoms form nano-sized clusters. This is manifested in quenching of the PL bands and creation of an optical absorption band at 2.43 eV due to the surface plasmon of free carriers in the cluster. The PL bands are attributed to the charge transfer transitions(Au-0+e(-)-> Au-) due to recombination of photo-excited electrons (e(-)), transiently transferred by ultraviolet excitation into a nearby cages, with Au-0 atoms.