Optical spectroscopy of copper(I)-doped sodium-.beta."-alumina

Abstract : The luminescence spectra of copper(+) doped sodium(+) Beta alumina single crystals reveal emission bands due to both Cu(+) monomers and Cu(+) - Cu(+) dimers. At low temperature two monomer emissions (410 nm and 440 nm) and two dimer emissions (515 nm and 540 nm) are observed. These bands are assigned to ions in specific sites within the Beta alumina conduction plane. The relative intensities of the emission bands are dependent on the sequence of irradiation and cooling. Changes in the relative intensities are caused by the photo- aggregation of the mobile Cu(+) ions to form dimers. These changes are an example of optical memory. The growth of the dimer emission band under ultraviolet excitation is a diffusion controlled process. The quenching of the monomer emission with increasing temperature correlates well with ionic hopping processes. The dynamics of ion motion which produce the green dimer emission band are quantified by a model based upon the thin film solution of Fick's second law.