Engineering supramolecular architectures on insulting and metal surfaces studied by scanning tunneling microscopy

Promotie: mw. X. Sun, 16.15 uur, Academiegebouw, Broerstraat 5, Groningen

Proefschrift: Engineering supramolecular architectures on insulting and metal surfaces studied by scanning tunneling microscopy

Promotor(s): prof.dr. P. Rudolf

Faculteit: Wiskunde en Natuurwetenschappen

Contact: Xiaonan Sun, tel. 050-363 83906, e-mail: x.n.sun@rug.nl

Engineering supramolecular architectures on insulting and metal surfaces studied by scanning tunneling microscopy

Investigation of supramolecular assembly on various surfaces is motivated by the potential of future organic electronics

Three PTCDA-melamine supramolecular networks on Au(111)- (22 × √3) have been achieved. Different chiral supramolecular having a PTCDA: melamine ratio of 3:2, 1:2, 1:4 networks were formed by tuning the ratio of the molecules deposited on the surface at room temperature. I also investigated the influence of the temperature on PTCDA-melamine self-assembly. PTCDA and melamine molecules form a 3:2 chiral supramolecular network at room temperature and annealing at 80°C switches the ordering into a completely different 1:2 row-like supramolecular network. PTCDA-Adenine architecture on Au(111) have been studied as well. A very complex supramolecular network was observed using STM. This network with a large unit cell which includes 14 molecules is chiral and has a molecular ratio of 5:2 (PTCDA: adenine).

To control and fabricate organic layers on insulating thin films is important to develop organic devices such as OFET. In this part of the work, I described my study of the formation of PTCDA (3,4,9,10-perylene-tetracarboxylic-dianhydride) nanostrutures on Au(111) covered with NaCl islands. STM images show that NaCl(100) layers are crystalline films. My STM measurements reveal that different NaCl(100) layers can selectively be imaged by changing the tunneling parameters, I then deposited PTCDA molecules on an Au surface covered with NaCl(100). I observed that PTCDA molecules preferred to form 2D domains on bare Au(111) surface and 3D clusters along the step edges of the NaCl(100) domains.