Interfacial wetting and percolation threshold in ultrathin Ni/C multilayerfilms

Magnetron sputtered Ni/C graded multilayers with bilayer periods between 3. 5 and 4.5 nm are investigated by cross-sectional transmission electron micr oscopy. The multilayers consist of amorphous C layers and close packed hexa gonal Ni layers. A percolation threshold of 2.0 nm at which Ni forms coales cent layers is observed for the given deposition conditions. This percolati on threshold can be explained by island growth of Ni on amorphous C owing t o the higher surface energy of Ni compared with C, explaining the sharp dec rease in X-ray reflectivity observed for periods below 4 nm.