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Gold sponges consisting of bicontinuous, 3D networks of branched nanowires and tortuous pores are prepared by anodic dissolution of silver from Ag 75 Au 25 alloy sheets in 1 mol L -1 HClO 4 , an electrochemical process occurring under mixed charge transfer and mass transport control. Samples resulting from dissolution are characterized by SEM, which reveals different surface and bulk morphologies, and EIS that allows an estimate of the Au sponge surface area through the measurement of its double layer capacity. This capacity depends linearly on the dissolution charge and attains values of 3-10 F g -1 of gold, increasing for increasing dissolution potentials in the explored range. The relation between typical size of the nanostructures and measured capacity is discussed by reference to a simple geometrical model of the internal wire-like structure. Aging causes some capacity decay, to be attributed to slow coarsening processes.

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Si 3 N 4 ∕ SiO 2 waveguides have been fabricated by low pressure chemical vapor deposition within a complementary metal–oxide–semiconductor fabrication pilot line. Propagation losses for different waveguide geometries (channel and rib loaded) have been measured in the near infrared as a function of polarization, waveguide width, and light wavelength. A maximum thickness of single Si3N4 of 250 nm is allowed by the large stress between Si3N4 and SiO2. This small thickness turns into significant propagation losses at 1544 nm of about 4.5dB∕cm because of the poor optical mode confinement factor. Strain release and control is possible by using multilayer waveguides by alternating Si3N4 and SiO2 layers. In this way, propagation losses of about 1.5dB∕cm have been demonstrated thanks to an improved optical mode confinement factor and the good quality of the interfaces in the waveguide.

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