Protection of silicon surface toward oxidation represents a relevant issue in view of many microelectronic applications. In 2000, it has been shown how molecular grafting with methyl groups could efficiently passivate atomically flat Si(1 1 1). However, neither data are currently available on (0 0 1) surfaces nor systematic analyses of the role played by the organic fragment on the protection efficiency have been reported yet. The aim of this paper is to present data on the passivation of (0 0 1) silicon surface by different aryl fragments self-assembled onto it. Protection was carried out using nucleophilic organic species that were self-assembled on a previously brominated Si surface. Specifically, five differently substituted phenyl groups were considered. These samples were characterized by specular reflection infrared spectroscopy to detect the presence of arylic-terminating groups. The kinetics of the re-oxidation reaction was then monitored over a time period of 2 months. We found qualitatively different mechanisms of re-oxidation, depending on the structure of the organic fragment. The first mechanism is compatible with a model where the aryl group simply hinders the surface Si sites, disabling the access of oxidizing species to the surface itself. The second process appears to be more complex, with the aryl group interacting with the oxidizing species. (C) 2003 Elsevier Science B.V. All rights reserved.