A variable temperature scanning tunneling microscopy study of organizing C60 molecules on nanostructured gold surface

The nucleation and growth of C₆₀ molecular nanostructures on the Au (111) surface are studied under various conditions using variable temperature UHV STM. At room temperature, the C₆₀/Au interface exhibits rich features observed in the STM images, for instance the lifting of the reconstruction and the appearance of dim molecules in the close-packed C₆₀ overlayer. Furthermore, the structural changes at the interface result in different bonding configurations of the adsorbed C₆₀ molecules, of which the strong bonding configuration can retain individual C₆₀ molecules on the elbow sites even at room temperature. This further leads to C₆₀ island nucleation at unexpected location. C₆₀ molecules deposited at reduced temperatures, 47 K and 180 K, respectively, do not induce atomic rearrangement of the Au (111) surface. The C₆₀ molecules are bonded to the intact reconstructed surface. However, the nucleation site and the island growth mode are still determined by the reconstruction pattern of the substrate. By increasing the C₆₀ coverage step-by-step and comparing with the growth scenario observed at the two temperatures, the details of the intermolecular and molecule-substrate interactions are revealed. Temperature dependent processes for the C₆₀/Au (111) system are studied by gradually raising the sample temperature from 47 K to room temperature. Diffusion is activated at ~160 K leading to ripening of the C₆₀ molecular structures. At higher temperatures, when a large number of C₆₀ molecules are released from the elbow sites, C₆₀ clusters with a magic number of seven are formed. These clusters only diffuse within the FCC regions of the surface with their diffusing direction confined by the reconstruction ridges (the DLs). The ripening process is also studied at room temperature over a long timescale. A combination of Ostwald ripening and Smoluchowski ripening process is observed.

Name dc:type.qualificationname

d_ph

Level dc:type.qualificationlevel

d_ph

Grantor dc:publisher.institution

University of Birmingham

Year dc:date.issued

2010

Author dc:creator

• Zhang, Xin

• QC Physics