We performed a hybrid density functional theory calculation for the successive adsorption of nitrous oxide (N2O) on Si(1 0 0)-Si9H12Ox (x = 0 and 1) cluster surfaces to elucidate N2O decomposition and the subsequent surface oxidation processes. N2O decomposed into N-2 and O fragments, and the latter fragment inserted into either surface-dimer bonds or back-bonds with similar activation barriers on both the clean and partially oxidized Si surfaces. The Si9H12 cluster surface was eventually oxidized to five distinct structures of Si9H12O2. (C) 2008 Elsevier B.V. All rights reserved.