An indium-oxide electrode with discontinuous Au layers for plasmonic devices

In this contribution we report on a low cost plasmonic electrode for light-sensing applications. The electrode combines a conducting nonstoichiometric indium oxide (InO_x) layer with an ultrathin (∼5 nm) discontinuous Au layer. The InO_x and Au layers were deposited on glass substrates by plasma enhanced reactive thermal evaporation and thermal evaporation, respectively. Several device configurations with one or two Au layer(s) sandwiched between InO_x layers were fabricated and characterized. The morphological and structural properties of both Au and InO_x layers were analyzed using AFM and XRD techniques. In particular, the effect of thermal annealing (673 K, 15 min) on the surface morphology of Au layers grown on bare glass and InO_x-coated substrate was investigated. It has been also found that the oxide film grown above an underlying nanostructured Au layer is amorphous, while a reference InO_x film on glass is nanocrystalline with a smooth surface. The electrical properties of InO_x grown on the Au surface are worsened due to Au-induced structural disorder. The observed difference in transmission spectra of the glass/InO_x/Au and glass/Au/InO_x structures indicates the difference in the morphology of the metal layer. Thus, the optical and morphological properties of the InO_xelectrode can be varied in a wide range by incorporating several Au layers.