Initial Growth of N,N′-Bis(1-ethylpropyl)perylene-3,4,9,10-tetracarboxdiimide Films on Cu(100)

Abstract

We have studied the initial stages of the adsorption of N,N′-bis(1ethylpropyl)-perylene-3,4,9,10-tetracarboxdiimide (EP-PTCDI) on Cu(100) using scanning tunnelling microscopy (STM), X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), and density functional theory (DFT) calculations. STM images show that the EP-PTCDI molecules initially absorb on the surface, forming ordered islands, without preferential nucleation at the step-edges of the terraces as is the case for adsorption of the same molecule on Ag(111). The 2D islands grow upon the completion of the surface with a single-molecular layer. The experimental and simulated LEED patterns show that the molecular arrangement within the islands can be explained by a commensurate superstructure and its four rotational equivalents. The electron spectroscopies show net charge transfer from the surface to the molecule and a decrease of about 0.7 eV in the work function (from 4.59 to 3.9 eV) after a single-layer adsorption. The DFT calculations for the adsorption of a single layer qualitatively reproduce the features observed in STM images and allow us to explain the observed charge exchange behavior together with the work function change.

Thermal Stability of N,N′-Bis(1-ethylpropyl)perylene-3,4,9,10-tetracarboxdiimide Films on Cu(100)

“…The O 1s peak slightly shifted (∼0.5 eV) to lower binding energies and the intensity decreased about 10%, suggesting a small change in its local electronic environment and a very small desorption of oxygen atoms from the surface. The N 1s peak broadens and seems to be formed by two components as it was observed previously for a monolayer adsorption shown in the experiments reported in ref . The shape of the N 1s peak before annealing looks similar to the others taken at a coverage slightly greater than a monolayer and after annealing to a coverage slightly lower than a monolayer.…”

“…The N 1s peak broadens and seems to be formed by two components as it was observed previously for a monolayer adsorption shown in the experiments reported in ref . The shape of the N 1s peak before annealing looks similar to the others taken at a coverage slightly greater than a monolayer and after annealing to a coverage slightly lower than a monolayer. The reduction of the O intensity by about 10% and the changes in shape of the N 1s peaks agree with the small change in coverage observed in STM images for the annealing of a monolayer.…”

“…In Figure a, we present the molecular arrangement observed after annealing the surface at 500 K. At this stage, the STM images showed that the coverage remained almost unchanged (a slight decrease of about 10%), while the arrangement of the molecules presented a different structure. Furthermore, the apparent STM height of the molecules is about 0.2 ± 0.1 nm, in agreement with an adsorption geometry in which the core of the molecules remains parallel with the substrate. , A close inspection of Figure a reveals a new molecular assembly in which the islands are oriented in four different crystallographic directions (different colors corresponds to different island orientations), with the same orientations that were observed before the annealing. In order to check for the symmetry of the molecular arrangement, we measured LEED patterns for different electron energies.…”

“…On the other hand, the C 1s spectrum also presents a shift of 0.5 eV to lower binding energies and a decrease of about 35% of the initial intensity (if normalized to a constant O intensity). It is important to highlight that the C 1s signal for the EP-PTCDI molecule comes from C atoms bonded to H atoms, either in the perylene core or in the EP end groups, to C atoms involved in the CCO bonds and to C atoms in the center of the perylene core, characterized by CC bonding. , These contributions are not resolved in the present experiments performed with an Al Kα X-ray anode without a monochromator, so part of the shift of the maximum can come from the variation of the relative contributions after annealing. However, the point that we want to make is the loss of intensity with almost no change of oxygen and nitrogen intensities, indicating that the molecules are dissociating, losing 35% of initial C atoms (and probably H, not seen by the current experimental techniques) but leaving O and N atoms on the surface.…”

Revealing the Adsorption and Decomposition of EP-PTCDI on a Cerium Oxide Surface

“…In order to investigate the catalytic behavior of Ce(III) in complicated systems, herein, functionalized perylene tetracarboxylic diimide, namely, N , N ′-bis(1-ethylpropyl)-perylene-3,4,9,10-tetracarboxdiimide (EP-PTCDI, C 34 H 30 N 2 O 4 ) has been chosen in this work, which comprises four C=O bonds and is shown in Scheme 1. As reported, this kind of molecules belonging to the class of perylene derivatives are versatile candidates toward organic optoelectronic applications due to their electronic, optical, and charge-transport properties, 16,17 as well as the commercial availability and low cost. In practice, decomposition of the EP-PTCDI molecule has been explored on various substrates in literature reports, and it was figured out that the ketone (C=O) group was directly cleaved from the EP-PTCDI molecule, 18,19 although the underlying mechanism has not been addressed yet.…”