The flux of atomic oxygen generated in an electron cyclotron resonance microwave plasma source was quantified by two different methods The commonly applied approach of monitoring the frequency change of a silver-coated quartz crystal microbalance (QCM) deposition rate monitor as the silver is oxidized was found to underestimate the atomic oxygen flux by an order of magnitude compared to a more direct deposition approach In the mixed-phase Ag/Ag2O deposition method silver films were deposited in the presence of atomic oxygen such that the films were partially oxidized to Ag2O X-ray photoelectron spectroscopy was utilized for quantification of the oxidized fraction The inaccuracy of the QCM oxidation method was tentatively attributed to efficient catalytic recombination of O atoms on the silver surface (C) 2010 Elsevier B V All rights reserved