Thermal desorption and stability of cobalt phthalocyanine on Ag(100)

Abstract

By performing work function change (ΔWF) measurements, we characterized thermal stability and desorption of cobalt phthalocyanine (CoPc) molecules on the Ag(100) surface from sub-monolayer to multilayer coverages. Based on the temperature dependence of the ΔWF we were able to determine the desorption temperature from multilayer. Obtained dependences of ΔWF and a low-energy electron reflectivity (R) for sub- and monolayer reveal that layers with contact with Ag(100) have higher thermal stability and their desorption is accompanied by decomposition of CoPc molecule. Exploring the time evolutions of the ΔWF at various temperatures allowed us to establish effective activation energies and effective frequency prefactors for processes occurring at various temperatures. The effective activation energies remain almost the same, from sub-monolayer to multilayer (2.97 eV – 2.62 eV), whereas the frequency prefactors vary from 1013 s−1 (monolayer) to 1024 s−1 (multilayer). For multilayer only desorption occurs, whereas for layers in contact with reactive Ag(100) surface (monolayer) the decomposition occurs at the same temperature range as desorption. Low-energy electron diffraction was used to describe CoPc molecular arrangements. To the best of our knowledge, we are the first who have observed (5 × 5)R ± 37° structure for CoPc on Ag(100).