Tailoring metal–organic hybrid interfaces: heteromolecular structures with varying stoichiometry on Ag(111)

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.

Submonolayer and multilayer growth of titaniumoxide-phthalocyanine on Ag(111)

“…Our approach considers electrostatic as well as van-der-Waals interaction. It was successfully applied to describe the intermolecular interactions and lateral structure formation of systems exhibiting weak adsorbate-substrate interactions, as, e.g., tetracene/ Ag(111) [8], PTCDA/Au(111) and CuPc/Au(111) [63], as well as for the heteromolecular adsorbate systems F 16 CuPc/CuPc/Ag(111) [64] and PTCDA+CuPc/Ag(111) [65]. The interaction between the two TiOPc layers for the system under study should therefore be well described by this approach.…”

Heteromolecular metal–organic interfaces: Electronic and structural fingerprints of chemical bonding

“…For the MZZ structure the suggested model is adapted from the results of the other phases and from pair potential calculations [63] which enable insight in energetically preferred relative orientation of the molecules with respect to each other, for details see Ref. [42]. When the coverage of both molecules deposited on the surface does not match with the stoichiometry of the heteromolecular structures, the excessive species forms homomolecular domains in separated areas on the surface.…”

“…Several groups have started to investigate such systems, and, for obvious reasons, prototypical molecules, the homomolecular adsorption of which is well understood, were combined to heteromolecular adsorbate systems in first instance [26][27][28][29][30][31][32][33][34][35][36][37][38][39]. Our group has concentrated on the molecules named above, PTCDA, NTCDA and MePcs, and investigated both laterally mixed structures (i.e., two molecules in different stoichiometries combined in one layer) [40][41][42] and heteromolecular stacks of layers whereby each individual layer contains only one species [43][44][45][46].…”

“…In this review paper we present an overview over the activities of our group regarding laterally mixed structures [40][41][42]. We combine investigations of geometric and electronic structure and focus on the interplay of the bonding heights of the molecules and the energy level alignment at the heteromolecular interface.…”

Towards functionalization of graphene:in situstudy of the nucleation of copper-phtalocyanine on graphene

“…The influence of substrate defects, e.g., steps or point defects, on the growth process becomes immediately apparent. This makes LEEM a powerful tool to investigate the growth of molecular thin films [5,[27][28][29][30][31][32][33][34][35][36].…”