Atomic layer deposition of iridium thin films and their application in gold electrodeposition

Advances in the deposition of metallic thin films are discussed. The ALD growth of ultrathin Ir films is analyzed by transmission electron microscopy, energy dispersive X-ray spectroscopy, atomic force microscopy, and optical and electrical measurements. The morphology of iridium metallic layers is assessed based on Ir/ Al2O3 nanolaminate films. High resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy measurements show sharp interfaces and pure Ir layers in the nanolaminates. The iridium films as polycrystalline. Excellent thickness control, high uniformity and low roughness of ALD films are demonstrated. Four point probe measurements of the resistivity of Ir coatings with various thicknesses have been performed and proved conductive layers with an Ir film thickness of ca. 10 nm. The optical properties of the Ir films deposited by ALD are similar to those of the bulk Ir. Thin iridum layers deposited on high aspect ratio linear gratings have been successfully used as electrodes in the electrochemical deposition of gold nanoparticles and gold layers. The gold deposition evolves through the formation of gold islands with ca. 40 nm diameters that coalesce after ca. 60 seconds deposition. The density of the gold islands within the grating pattern is much lower than on the flat region of the substrate. The combination of ALD with electrochemical deposition allows the diversification of conductive layers on complex nanostructured surfaces.