STM Study Of The Adsorption And Assembly Of Truxenone And Fullerene Molecules On Surfaces

It is important to investigate the adsorption and assembly of organic functional molecules on surfaces for our understanding of the physical, chemical, molecular electronics and nonlinear optical properties as well as the "bottom-up" approach for nano functional devices. Scanning tunneling microscope (STM) is a powerful tool for characterization of the molecules adsorbed on the metal surface due to its high resolution ability. This thesis focuses on the adsorption and assembly of two types of functional molecules on a gold surface. Main content is as follows:i) Endohedral fullerene N@C6o was produced by ion implantation method. The enrichment was obtained by high performance liquid chromatography in a concentration of90%, which can be used for further characterization on the molecular scale.ii) The adsorption and molecular orientation of Dy@C82on Au(111) has been investigated using UHV STM at80K. At low coverages, the Dy@C82molecules tend to grow along the step edges of Au(111), forming small clusters and molecular chains. Adsorption of Dy@C82on the edges is dominated by the fullerene-substrate interaction and presents various molecular orientations. At higher coverages, the Dy@C82is found to form ordered islands consisting of small domains of equally oriented molecules. The Dy@C82molecules in the islands prefer the adsorption configurations with the major C2axis approximately parallel to the surface of the substrate. These observations are attributed to the interplay of the fullerene-substrate interaction and dipole-dipole interaction between the metallofullerenes.iii) We have studied the2D supramolecular structures in different domains of the truxenone monolayers on Au (111) surface. The truxenone assembly exhibits ordered structures of the hexagonal close-packed domain, the hexagonal honeycomb domain with the edge-to-edge arrangement, and the domain with the displaced edge-to-edge arrangement. Based on our DFT calculations, the intermolecular interaction and the molecule-substrate interaction have been analyzed energetically at the molecular level. The occurrence of the different supramolecular structures can be attributed to the slight difference of the interaction energies among these structures.