PEEM and LEED insights into the growth of ultrathin CoPc and F16CuPc films on Ag(100) surfaces

Description

Thin layers of metal phthalocyanines are studied due to their promising applications as active layers in optoelectronics devices. In this contribution, we will present a study on the physical vapor deposition of cobalt phthalocyanine (CoPc) and fluorinated copper phthalocyanine (F16CuPc) on silver (100) surfaces maintained at room temperature. The molecules have opposite effects on the work function of the substrate. Up to a coverage of about one monolayer (ML) CoPc decreases, whereas F16CuPc increases the work function of Ag(100).

Photoemission Electron Microscopy (PEEM) with a xenon (Xe) lamp was used to study the changes in electron yield (EY) during the deposition of monomolecular and bimolecular layers. For coverages ranging from 0 to 1 monolayer (ML), the adsorption of CoPc caused a significant increase in EY, while the adsorption of F16CuPc slightly decreased it. Starting with the completion of the first layer and, therefore, while filling molecules into the second layer, for both molecules, CoPc and F16CuPc, we observe a decreasing electron yield. This is consistent with the changes in work function measured using the Anderson method [1].

The bimolecular layer was formed by stepwise deposition. The EY was examined continuously. Each dose of CoPc applied increased the EY, while each dose of F16CuPc decreased it. Regardless of the order of dosing of the molecules - first CoPc and then F16CuPc or vice versa - the EY trend obtained for the growth of the bimolecular structure (with a 1:1 ratio of the two constituent molecules) corresponds qualitatively to the superposition of the EY trajectories obtained with the deposition of only one compound.

PEEM and low-energy electron diffraction data suggest in addition that if only one kind of molecules is deposited, a 2D molecules gas phase prevails up to almost 0.8 ML [2]. If the two molecules are deposited in small steps and alternating sequence, we observe an instantaneous condensation upon deposition of the second species.


[1] Thorsten Wagner et al. “Attenuation of Photoelectron Emission by a Single Organic Layer”. In: ACS
Appl Mater Interfaces 14.20 (2022), pp. 23983–23989. DOI: 10.1021/acsami.2c02996
[2] Grazyna Antczak et al. “Identification of CoPc + F16CuPc Chiral Domains by LEEM with the Molec-
ular Structure Factor”. In: The Journal of Physical Chemistry C 128.12 (2024), pp. 5338–5344. DOI:
10.1021/acs.jpcc.4c00386

Period	03 Jun 2025
Event title	ECSCD16/ICSOS14
Event type	Conference
Location	Wien, AustriaShow on map
Degree of Recognition	International