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Structures of Self-Assembled n-Alkanethiols on Gold by Reflection High-Energy Electron Diffraction

preprint
submitted on 30.05.2020 and posted on 01.06.2020 by Mithun Ghosh, Ding-Shyue Yang
TThe structures of long-chain alkanethiols (C18H37SH) chemisorbed on an Au(111) single crystal were investigated using reflection high-energy electron diffraction (RHEED). The primary (√3x√3)R30° structure observed as a major species in the as-deposited films contains gold adatoms below the sulfur headgroups. Between the small ordered domains with the alkyl chains tilting toward six directions are azimuthally disorderly packed regions, with a similar average tilt of 30.2°. In contrast, a significant reduction in the coverage of gold adatoms is found in the thermally-induced (2√3x3)rect phase. This superlattice is shown to contain a mixture of two sulfur arrangements, both of which exhibit a small S‒S distance, and the pairing of the aliphatic chains. A microscopic picture is then given for the structural transition. These findings demonstrate how the RHEED technique may be used to resolve structures of nanometer-thick thin films with multiple orders at the interfaces.

History

Email Address of Submitting Author

yang@uh.edu

Institution

University of Houston

Country

United States

ORCID For Submitting Author

0000-0003-2713-9128

Declaration of Conflict of Interest

The authors declare no competing financial interests.

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