EXAFS Analyses on Local Structure of Gallium in Amorphous Selenide Optical Materials Doped with Rare Earths
Ga K-edge EXAFS spectra have been analyzed to elucidate the local coordination structure of Ga in two representative selenide Ge-As-Se and Ge-Sb-Se glasses all doped with Pr. Gallium turned out to be coordinated with 4 Se atoms in its first neighboring shell. This implies that Ga does not follow the 8-N rule associated with the short-range order structures of typical covalent glasses, further indicating there being more ionic-bond nature in the Ga-Se bonds compared to other heteropolar chemical bonds in the selenide glasses. This is decisive for the Pr3+ ions to be incorporated in the selenide glasses. In this case, the GaSe4 units can be electrically neutralized by the doped Pr3+ ions that act as a charge compensator. As such, inside the selenide glasses, distributions of Pr3+ ions and the Ga tetrahedral units are closely correlated. Spectroscopic properties of rare earths embedded in these Ga-containing selenide glasses thus can be explained in connection with the proposed role of Ga.
Byung Tae Ahn, Hyeongtag Jeon, Bo Young Hur, Kibae Kim and Jong Wan Park
Y. G. Choi "EXAFS Analyses on Local Structure of Gallium in Amorphous Selenide Optical Materials Doped with Rare Earths", Solid State Phenomena, Vols. 124-126, pp. 1665-1668, 2007