Optical characterization of thin and ultrathin chromium films

Thin and ultrathin chromium films were grown on glass by thermal evaporatio n in vacuum of the order of 10(-4) Pa with the purpose of studying the char acteristics of these layers used as adhesion promoters in a number of appli cations. Ellipsometry is used to obtain the optical properties of chromium and chromium oxide as well as the equivalent ultrathin layer for films with thickness from a fraction to a few nanometers. Experimental measurements a nd theoretical modeling showed that the ultrathin films essentially consist of chromium/chromium oxide clusters with heights of the order of the measu red thickness as determined by a quartz microbalance indicating a Vollmer-W eber growth mechanism. Percolation was found for thickness above 30 nm.