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

摘要

Graphical abstractDisplay OmittedHighlights•Thermal stability of CoPc layers on Ag(100).•Structures of monolayers of CoPc on Ag(100) after thermal treatment.•Thermal desorption of multilayer of CoPc from Ag(100).•Thermal desorption and dissociation of monolayer of CoPc above 680 K.AbstractBy 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 theΔWFwe were able to determine the desorption temperature from multilayer. Obtained dependences ofΔWFand 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 theΔWFat 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).