Electroless Ru depositions on Si substrates undergoing surface pretreatments such as hydrogen fluoride (HF) etching, HF etching and activation, as well as HF etching, sensitization, and activation are explored. The plating bath contains K2RuCl5 center dot xH(2)O, NaClO, NaOH, and NaNO2 at appropriate ratios. Continuous electroless Ru film is unable to obtain on the as-received Si wafer because the native oxide inhibits the process of nucleation and growth. In contrast, after surface pretreatments, dense and continuous Ru films are observed at reasonable growth rates. Contact angle measurements indicate a relatively hydrophilic surface after sensitization and activation, which leads to faster Ru film growths and larger surface roughness as compared to the HF-etched sample. X-ray photoelectron spectra confirm the formation of Sn and Pd nuclei and their presence promotes the heterogeneous growth of Ru films as evidenced by images from scanning electron microscope. In addition, depth profiling from Auger electron spectrometer suggests a uniform composition across the film thickness despite part of the Ru exists in an oxidized form. (C) 2012 Elsevier B.V. All rights reserved.