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ToF‐SIMS investigations of the degeneration processes of self‐assembled monolayers of alkanethiols on gold

Time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) has been used to study the degeneration process of self‐assembled monolayers (SAMs) of alkanethiols on gold upon ambient air exposure. Alkanethiol SAMs with varying alkyl chain length n ranging from n = 1 to n = 17 were prepared simultaneously and analysed after being stored at ambient air for specific time periods. Static SIMS spectra show a range of mass signals characteristic for non‐degenerated SAMs, like gold‐alkanethiolate clusters, on the one hand, and for degenerated SAMs, like alkanesulfonates, on the other. These characteristic mass signals enable the observation of degeneration processes. We found that the rate of degeneration increases rapidly with decreasing alkyl chain length. Furthermore, for short‐chain alkanethiol SAMs with n ≤ 3, a randomly initialized degeneration plays a major role, whereas for long‐chain alkanethiol SAMs, the degeneration starts at domain boundaries and defects, propagating into intact domains. Copyright © 2004 John Wiley & Sons, Ltd.