Nanoscale assembly, morphology and screening effects in nanorods of newly synthesized substituted pentacenes

Abstract

We report our investigation on the nanorods of two newly synthesized substituted pentacenes, d 4 -substituted (2,3-X 2 -9,10-Y 2 ) pentacene with X = Y = methoxy group (MOP) and X = F, Y = methoxy (MOPF), by using X-ray photoemission spectroscopy (XPS), near edge X-ray absorption fine structure (NEXAFS), and atomic force microscopy (AFM). The nanorods were deposited on Au(111) single crystals. Energy dependent photoemission spectra show complex features, including a rich satellite structure that we have analyzed in detail by using a bestfit procedure applying constraints based on stoichiometry, electronegativity, and bond strength. This analysis reveals the presence of surface core level shifts due to the high electronegativity of the fluorine atoms. The distinctive features of growth and morphology of the nanorods are subjected to a template effect by the substrate lattice geometry, leading to morphological well-organized assemblies. Fluorine atoms play an important role not only in the electronic structure but also in the morphology of the nanorod assemblies.

Chemisorption, Morphology, and Structure of a n‐Type Perylene Diimide Derivative at the Interface with Gold: Influence on Devices from Thin Films to Single Molecules

“…The broad feature at higher binding energy is due to signals coming from photoelectrons emitted from carbon atoms of the alkyl chain (CH chain ) and from those bound to nitrogen atoms (CN), whereas the peak at 288.55 eV is related to photoelectrons from the carbon atoms of the carbonyl group (CO). The assignments are in agreement with the values reported in the literature for analogous spectroscopic lines 21–25. We observe that the C 1s core level spectrum of the thinnest film looks very different in comparison with the one of the thickest film.…”

Fingerprint of Fractional Charge Transfer at the Metal/Organic Interface

“…[31,32] Likewise, a non-rigid shift is reported in the literature for other physisorbed organic molecules like 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA), [33] cobalt phtalocyanine, [34] and magnesium phthalocyanine. [35] This behaviour is present irrespective of the specific orientation of the molecules on the substrate that ranges from flat lying (PTCDA [33] and phtalocyanine [34,35]) to recumbent (substituted pentacenes [31,32]). Note that polarization dependent NEXAFS experiments show that that first layer of F4PEN molecules at the interface with gold are flat-lying (see Electronic Supporting Information).…”

“…We consider 0.75 electrons as the upper limit of the transferred charge since in this quantification we accumulate also contributions due to other possible sources of (rigid) corelevel shifts: These are changes in the molecular orientation, [41] different charge redistribution, due to the strong electronegativity of the fluorine atoms [31] when comparing surface and bulk environment of the molecules (surface core level shift [36,42]) and imagecharge screening effects due to the capability of the substrate to screen the core-hole generated in the photoemission event. [7] The experimental finding that no appreciable change in the HOMO takes place upon charge transfer (compare the UPS spectra of the thick and thin assemblies in Figure 1) is also supported by our calculations.…”

Island shape and electronic structure in diindenoperylene thin films deposited on Au(110) single crystals

“…26 These results are also in good agreement with investigations performed on PTCDA, 3,35,36 on needles of parahexaphenyl and sexithiophene grown on muscovite and phlogopite mica, 37,38 and on nanorods of substituted pentacenes. [32][33][34] Au(110) has different surface energies and different atom densities than Au(100) and Au(111). 30,[39][40][41] A more open surface may cause a stronger bonding.…”

“…44,45 However, we observed clear SCLS in nanorods of substituted pentacenes contacting electronegative atoms. [32][33][34] The SCLS observed in the substituted pentacenes can be explained, as in classical semiconductors, to be due to the redistribution of the charge on the surface atoms in the ground state because of the effect of electronegativity. In fact, this model has been successfully used, for example, for SCLS in III-V semiconductors, where the levels of the group III atoms at the surface show larger binding energies while those of the group V atoms are shifted to smaller binding energies because of the deviation of the charge distribution at the surface in comparison with the bulk.…”