Local structure of AgOx thin layers generating optical near-field

Discovery of near-field generation by plasmons excited in thin AgO_x layers made them important components in advanced optical technologies such as Super-RENS (H. Fuji et al, Jpn. J. Appl. Phys., vol. 39, p. 980, 2000) and the purely optical photonic transistor (J. Tominaga et al, Appl. Phys. Lett., vol. 78, p. 2417, 2001). In order to unravel the nanometer-scale mechanism of the silver nanoparticle formation upon photo-induced decomposition of the AgO_x layer and its relationship with the plasmon generation efficiency, knowledge of the local structure of as-deposited AgO_x layers and its modification upon thermal annealing and optical initialization is of utmost importance. A unique technique which allows determination of the local structure with atomic selectivity in both crystalline and amorphous states is X-ray absorption fine structure (XAFS) spectroscopy. In this paper, we present the results of the first such study applied to AgO_x thin layers.