Electron Beam-Induced Damage of Alkanethiolate Self-Assembled Monolayers Adsorbed on GaAs (001): A Static SIMS Investigation

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We have investigated the reaction pathways involved in the electron-beam-induced damage of −CH3, −OH, and −COOH terminated alkanethiolate self-assembled monolayers (SAMs) adsorbed on GaAs (001) using time-of-flight secondary ion mass spectrometry. Upon electron beam exposure, the monolayers dehydrogenate, leading to the formation of C═C bonds, cross-links, and polycyclic aromatic hydrocarbons (PAHs). We also observe C−S bond scission. The data suggest that the electron beam damage is not uniform along the alkanethiol backbone. Upon electron beam exposure, we observe the loss of CO2 and H2O from the −COOH and −OH terminated SAMs, respectively, indicating that the terminal groups decompose. Although the SAM degradation mechanism is similar to that previously reported for alkanethiolate SAMs adsorbed on metals, there are some important differences. First, the electron dose required to form C═C bonds and PAHs is much smaller than for SAMs adsorbed on metals. Second, although we observe C−S bond scission, we d...