Nanopatterning on H‑Terminated Si(111) Explained as Dynamic Equilibrium of the Chemical Reaction with Methanol

  • chair:

    Thissen, P. / Fuchs, E. / Roodenko, K. / Peixoto, T. / Batchelor, B. / Smith, D. / Schmidt, W., G. / Chabal, Y. (2015)

  • place:

    Journal of physical chemistry C, 119, (2015), 29, 16947-16953

  • Date: Juli 2015


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.