Abstract
The physical properties of interfaces between organic semiconductors and metal surfaces crucially influence the performance of organic electronic devices. In order to enable the tailoring of such metal–organic hybrid interfaces we study the adsorption of heteromolecular thin films containing the prototypical molecules copper-II-phthalocyanine (CuPc) and 3,4,9,10-perylene-tetra-carboxylic-dianhydride (PTCDA) on the Ag(111) surface. Here, we demonstrate how the lateral order can be tuned by changing the relative coverage of both adsorbates on the surface. The layer growth has been studied in real time with low energy electron microscopy, and—for different stoichiometries—the geometric properties of three heteromolecular submonolayer phases have been investigated using high resolution low energy electron diffraction and low temperature scanning tunneling microscopy. Furthermore, we have used a theoretical approach based on van der Waals and electrostatic potentials in order to reveal the influence of the intermolecular and the molecule–substrate interactions on the lateral order of heteromolecular films.
Highlights
One crucial issue for the success of organic materials in electronic devices is the ability to design the interfaces between different active layers according to their functional purpose
On the way towards realization of such tailor-made systems, the first studies on the lateral order in heteromolecular adsorbate films have been reported recently [25,26,27,28]. They already demonstrated that the lateral periodicity can be influenced by the stoichiometry of the components and that the arrangement of the molecules in the heteromolecular films is mainly determined by intermolecular interactions. In addition to these findings, we recently revealed the importance of the molecule–substrate interaction for the properties of heteromolecular-metal hybrid interfaces formed by coadsorption of copper-II-phthalocyanine (CuPc) and PTCDA on Ag(111) [29]
The local arrangement of containing the prototypical molecules copper-II-phthalocyanine (CuPc) and PTCDA in heteromolecular monolayer structures on Ag(111) is the result of an optimization of the interface energy involving intermolecular interactions between both types of molecules as well as the bonding of the individual molecules to the substrate. This leads to similar orientations of both molecules in all heteromolecular phases: while the CuPc molecules are always almost precisely oriented with their long symmetry axis along rows of silver atoms ([1 ̄10]-direction), the long axis of the PTCDA molecules is rotated by 30°–40° with respect to this direction
Summary
Organic hybrid interfaces we study the adsorption of heteromolecular thin films containing the prototypical molecules copper-II-phthalocyanine (CuPc) and 3,4,9,10-perylene-tetra-carboxylic-dianhydride (PTCDA) on the Ag(111) surface. We demonstrate how the lateral order can be tuned by changing the relative coverage of both adsorbates on the surface. We have used a theoretical approach based on van der Waals and electrostatic potentials in order to reveal the influence of the intermolecular and the molecule–substrate interactions on the lateral order of heteromolecular films
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