Seminarium Fizyki Politechniki Wrocławskiej
Sala 322, budynek A1, PWr
Identification of chirality of the organic molecular domains in the reciprocal space
dr hab. Grażyna Antczak
Instytut Fizyki Doświadczalnej, Uniwersytet Wrocławski
The properties of the molecule-substrate interface are important for the performance of devices with an active layer of organic molecules. By co-adsorption of different organic molecules, so called bimolecular or binary monolayers are formed, which have interesting properties such as modulation of charges at the interface on the nm scale. In our study, we focus on the molecular layer composed of phthalocyanines adsorbed on the metallic surface. Phthalocyanine (Pc) molecules are a group of molecules that have been intensively studied due to their interesting properties for applications in optoelectronics. We study the combination of phthalocyanines by mixing molecules on the surface with opposite influence on the work function of the substrate. For this we use low energy electron microscopy (LEEM). The subject of this talk are the bimolecular domains composed of cobalt phthalocyanine (CoPc) and perfluorinated copper phthalocyanine (F16CuPc) adsorbed on Ag(100) surfaces at room temperature and subsequently annealed at 470 K. The CoPc up to monolayer coverage decreases the work function of the silver surface while F16CuPc increases it. Due to the electrostatic interaction between the partially negatively charged fluorine atoms of F16CuPc and the partially positively charged hydrogen atoms of the CoPc, the first monolayer of the mixed phase in a 1:1 ratio is arranged in a checkerboard-like superstructure [1]. The individual phthalocyanine (Pc) molecules are adsorbed in this molecular structure in such a way that their molecular axis is rotated by 27o with respect to the <011> directions of the substrate [2, 3]. This leads to the development of two mirror domains with opposite chirality. In this talk we will show that the structure factor of the constituent molecules allows the identification of these domains using the micro-diffraction mode (µLEED) of the LEEM apparatus. Furthermore, when the µLEED mode is applied to the dilute 2D molecular gas formed by about 0.5 ML of F16CuPc on the surface, it allows a direct imaging of the molecular structure factor and, hence, the identification of the adsorption geometry of the molecule.
The authors gratefully acknowledge the financial support from program `Excellence initiative research university' for years 2020-2026 for University of Wrocław.
[1] A.Sabik, P. Mazur, F. Gołek, A. Trembulowicz, G. Antczak, J. Chem. Phys. 2018, 149, 144702.
[2] A, Mugarza, R. Robles, C. Krull, R. Korytár, N. Lorente, P. Gambardella, Phys. Rev. B 2012, 85, 155437.
[3] G. Antczak, W. Kaminski, A. Sabik, C. Zaum, K. Morgenstern, J. Am. Chem. Soc. 2015, 137, 14920
