Transformation of the Ag(111) surface state due to molecule-surface interaction with ordered organic molecular monolayers

Abstract

We present a detailed study of 3,4,9,10-perylene-and 1,4,5,8-naphthalene-tetracarboxylic acid dianhydride monolayers adsorbed on Ag(111) film. The study is based on density functional theory with the use of a periodic slab model. The slab is chosen to contain an organic molecular monolayer on a silver thin film of different thicknesses (6, 9, and 12 layers) with the (111) orientation. We show that in both cases there is a similarity in formation of an unoccupied interface state from a surface state of the bare Ag(111) film due to the adsorbate-substrate interaction. The energy difference between the initial surface state and the resulting interface state varies with the film thickness, the adsorption distance, and the molecule size and geometry, whereas the effective mass of the state remains practically unchanged. Also, we demonstrate that the interface-state charge distribution preserves its localization in the interface region at different wave vectors k and in the vicinity of the molecular plane resembles lowest unoccupied orbitals of free molecules.

Electronic Structure of Titanylphthalocyanine Layers on Ag(111)

“…59,60 This interpretation was subsequently confirmed by density-functional theory (DFT) calculations. [61][62][63][64][65][66] In the meantime, additional molecules, e.g., NTCDA, 63 H 2 Pc and FePc 48 grown on Ag(111) and other substrates have been investigated, [67][68][69][70][71][72][73][74][75][76][77][78][79] which confirm the rather general phenomenon of the existence of interface states. Such a state can be successfully described by a model potential combining the metal substrate and a flat π-conjugated molecular layer.…”

Model potential for the description of metal/organic interface states

“…The reallocation of the probability density from the metal surface into the interface and the vacuum region is even stronger as compared to d C = 4.00 Å and the penetration into the metal further decreases to p = 64.70%. The blue solid line shows for comparison the laterally averaged result of a DFT calculation that has been performed for PTCDA on a nine-layer thick Ag(111) slab 24 . The agreement between our results for the one-dimensional model potential and the DFT-result is remarkably good, in particular within in metal and between the metal and the carbon plane.…”

“…The large size of the organic molecules does not only require a large supercell within a slab model in the lateral direction. A reasonable description of the intrinsic Shockley surface state of the metal makes it necessary to consider also a large number of metal layers 24 . Both make such calculations very time-consuming.…”

Multi‐Component Organic Layers on Metal Substrates

“…Their existence has in fact been demonstrated for the PTCDA/Ag(111) system, for which LUMO‐Shockley hybrid interface states develop above the Fermi energy . Nonetheless, interface states of Shockley nature may vary considerably in energy among distinct molecular species . This is particularly attractive, because it may provide substantially different hybridization scenarios both with HOMO and LUMO derived states.…”