ADSORPTION KINETICS AND THERMAL STABILITY OF EP-PTCDI FILMS GROWN ON AG(111) STUDIED BY AFM, STM AND DFT

LAURA N. SERKOVIC LOLI, J. ESTEBAN GAYONE, M. LUZ MARTIARENA, ESTEBAN A. SÁNCHEZ, OSCAR GRIZZI, AND VLADIMIR A. ESAULOV

Congreso; 10th Inter-American Congress of Electron Microscopy; 2009

The adsorption and the thermal stability of N,N’-bis(1-ethylpropyl)-perylene-3,4,9,10-tetracarboxdiimide (EP-PTCDI) grown on Ag (111) under UHV conditions has been studied by means of Atomic Force Microscopy (AFM), Scanning Tunneling Microscopy (STM), and Density Function Theory (DFT).We have observed that the molecules start to adsorb on the Ag(111) step edges forming islands that grow to fully cover the surface with an ordered monolayer. Further exposures resulted in the formation of 3D islands keeping the molecular order for the early layers, and without a completely coalescence even for films of 20 nm thickness.After growing a multilayer film at room temperature, its stability has been checked as a function of the sample temperature. The results showed the desorption of a multilayer at about 150ºC, leaving a monolayer of molecules that dissociate for temperatures greater than 200ºC. At 400ºC a monolayer of other molecules, presumably the perylene core of the EP-PTCDI, still remain forming large ordered regions.DFT calculations were performed to obtain information on the geometrical configuration and the electronic properties of a isolated single molecule of EP-PTCDI and of the monolayer adsorbed on the Ag(111) surface. The calculated partial density of states gives some insights to interpret the STM images.