Abstract

Here the microscopic mechanism that leads to the surprising formation of a nanopattern upon methanol reacting with a H-terminated Si(111) surface [Michalak et al., Nat. Mater. 2010, 9, 266−271] is reinvestigated from both theory and experiment.

First-principles calculations determine the fully OCH3-terminated Si(111) surface as the thermodynamic
ground state in the presence of methanol, seemingly in contrast to the experimentally found nanopattern. At 65 °C the presence of H2 initiates desorption of the methoxy groups and thereby leads to a dynamic equilibrium of the reaction of methanol with the H-terminated Si(111) surface, which is a 1/3 OCH3-terminated and 2/3 H-terminated Si(111)
surface, with all OCH3 groups standing as NNNs, corresponding to the nanopattern observed earlier.

Investigating fluorine group termination of Si(111) as a test system the present study demonstrates that the combination of theoretical and experimental techniques used here is in fact sufficiently sensitive to resolve complex molecular systems even with lateral resolution.

Download