Orientationally ordered (7x7) superstructure of C60 on AU(111)

Area of Science:

• Surface Science
• Materials Science
• Condensed Matter Physics

Background:

• Fullerenes, specifically C60, are important in materials science.
• Understanding molecular ordering on surfaces is crucial for developing new electronic and optical devices.
• Gold surfaces, like Au(111), are common substrates for studying molecular self-assembly.

Purpose of the Study:

• To investigate the long-range orientational order of C60 molecules on a Au(111) surface.
• To elucidate the structural characteristics of the C60 monolayer superlattice.
• To propose a model explaining the substrate-induced ordering and stabilization mechanisms.

Main Methods:

• Low-temperature scanning tunneling microscopy (LT-STM) was employed to visualize the molecular arrangement.
• Structural analysis of the observed unit cell and molecular orientations.
• Development of a theoretical model to explain the observed phenomena.

Main Results:

• Observation of long-range orientational order in C60 monolayers on Au(111).
• Identification of a unit cell containing 49 C60 molecules with 11 distinct orientations.
• The unit cell exhibits a faulted and unfaulted half, analogous to Si(111) reconstruction.
• A Moiré-like effect induced by the substrate causes subtle changes in C60 molecular orientation.

Conclusions:

• The substrate significantly influences the orientational order of C60 molecules through a Moiré-like effect.
• Intermolecular interactions are critical for stabilizing the observed superlattice structure.
• The findings provide insights into the self-assembly of molecular monolayers on metal surfaces.