Characterization of Electrolessly Deposited Copper and Nickel Nanofilms on Modified Si(100) Surface

Abstract

Ultrathin Cu and Ni films, with thicknesses on the orders of 40 nm (nanofilms) and 200 nm, were electrolessly deposited on the hydrogen-terminated Si(100) surface modified by coupling with vinylimidazole (VIDz). Transmission electron microscopy (TEM) images and X-ray diffraction (XRD) patterns revealed that the electrolessly deposited Cu films were nanostructured, with grain sizes smaller than 65 nm. On the other hand, the Ni films were partially crystalline, with grain sizes on the order of 10 nm or less. The electrolessly deposited Cu and Ni nanofilms had physical properties rather different from those of the thicker films. Atomic force microscopy (AFM) images revealed that the Cu and Ni nanofilms had a higher density of defects and smaller metal clusters in the surface region. The Cu and Ni nanofilms also exhibited a substantially higher electrical resistivity. X-ray photoelectron spectroscopy (XPS) results suggested that the chemical composition and the state of the as-deposited Ni and Cu films were independent of the film thickness. However, the as-deposited Ni and Cu nanofilms oxidized at a much faster rate than their 200-nm-thick counterparts, when subjected to a direct current (DC) loading of about 1.0 × 109 A/m2 in air. The higher oxidation rate was attributed to the higher density of defects, higher electrical resistivity, and larger surface area to bulk volume ratio of the nanofilms.