Molecule-Driven Substrate Reconstruction in the Two-Dimensional Self-Organization of Fe-Phthalocyanines on Au(110)

Abstract

The structural patterns formed by molecular self-assembly at surfaces are usually controlled by the relative strengths of the intermolecular and molecule–substrate interactions. An additional steering effect is present when the substrate can easily reconstruct upon molecular adsorption, which therefore drives a self-templating effect on the metal support. This is here demonstrated for the model case of Fe-phthalocyanine molecules adsorbed on the Au(110) surface. Scanning tunneling microscopy shows that molecular adsorption promotes a local (1 × 5) surface reconstruction, which drives the assembly of molecular chains along the [11̅0] direction. The order and periodicity of the molecular assemblies are determined with low energy electron diffraction patterns. Density functional theory calculations reveal the energetic origins of the molecule-driven substrate reconstruction. Since the function of molecular overlayers at surfaces is strongly correlated to their structure, these results have implications in the design of new metal/molecular interfaces.

Metal-phthalocyanine ordered layers on Au(110): Metal-dependent adsorption energy

“…Indeed, two opposite phenylene rings bend up and the perpendicular ones bend down with respect to the surface, causing a breaking of the fourfold molecular symmetry. 16 This angular deformation has been previously observed for MPcs on semiconductor surfaces, 39,[45][46][47] where the molecular distortion induced by the substrate covalent bondings is more pronounced. This slight molecular distortion can explain the energy shift between the benzene and pyrrole components of the C 1s core-levels when the central metal atoms of FePc and CoPc interact with Au.…”

“…This slight distortion is compatible with the STM observation of CoPc and FePc molecules adsorbed on Au(110) in the SL coverage stage, being the central metal atom directly adsorbed onto a Au row. 16 In particular, ab initio calculations brought to light a distortion of the molecules in contact with the Au atomic rows, associated to the macrocycle bending. Indeed, two opposite phenylene rings bend up and the perpendicular ones bend down with respect to the surface, causing a breaking of the fourfold molecular symmetry.…”

“…13,14 MPc adsorption on Au(110)-(1×2) leads to the formation of ordered chains along the [110] direction, with the MPc molecular plane oriented parallel to the surface. 15,16 The planar orientation, in particular for the first single-layer (SL), is due to an interaction between the metal-phthalocyanine orbitals and the Au electronic levels. [16][17][18][19] Transition metal phthalocyanines with an open shell structure of the central ion molecular orbitals, strongly interact with the metal substrates, affecting the electronic, optical, and magnetic properties of the organic/metal interface, thus influencing the performances of the molecular device.…”

“…15,16 The planar orientation, in particular for the first single-layer (SL), is due to an interaction between the metal-phthalocyanine orbitals and the Au electronic levels. [16][17][18][19] Transition metal phthalocyanines with an open shell structure of the central ion molecular orbitals, strongly interact with the metal substrates, affecting the electronic, optical, and magnetic properties of the organic/metal interface, thus influencing the performances of the molecular device. 10,20,21 In this paper, we determine the adsorption energy of FePc and CoPc adsorbed on Au(110), with respect to CuPc/Au(110), as estimated by Temperature Programmed Desorption (TPD).…”

Surface chemistry of porphyrins and phthalocyanines

“…Similar structures were formed by FePc, NiPc and ZnPc on this substrate [257] and for FePc an adsorbate-driven local (1 Â 5) reconstruction of the Au substrate was reported [258]. On the vicinal Au (7 8 8) surface, CoPc was found to preferentially occupy step edges by bridging adjacent terraces, resulting in a tilted molecular plane.…”