Structural Phases of Ordered FePc-Nanochains Self-Assembled on Au(110)

Abstract

Iron-phthalocyanine molecules deposited on the Au(110) reconstructed channels assemble into one-dimensional molecular chains, whose spatial distribution evolves into different structural phases at increasing molecular density. The plasticity of the Au channels first induces an ordered phase with a 5×5 symmetry, followed by a second long-range ordered structure composed by denser chains with a 5×7 periodicity with respect to the bare Au surface, as observed in the low-energy electron-diffraction (LEED) and grazing incidence X-ray diffraction (GIXRD) patterns. The geometry of the FePc molecular assemblies in the Au nanorails is determined by scanning tunneling microscopy (STM). For the 5×7 phases, the GIXRD analysis identifies a "4-3" rows profile along the [001] direction in the Au surface and an on-top FePc adsorption site, further confirmed by density functional theory (DFT) calculations. The latter also reveals the electronic mixing of the interface states. The chain assembly is driven by the molecule-molecule interaction and the chains interact with the Au nanorails via the central metal atom, while the chain-chain distance in the different structural phases is primarily driven by the plasticity of the Au surface.

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

“…The chain structure is driven by the underlying Au structure with a ×7 periodicity, constituted by sequences of ×4-×3 Au chains, 18 such as to allocate the molecules into the widened gold channels. This adsorption geometry is comparable to that recently observed for FePc single-layer adsorbed on the Au(110) substrate, 18 where the parallel chains showed the same arrangement observed here. A row of bare Au atoms is directly lying below the topmost molecular chains, hence the MPc molecules are in direct contact with the gold substrate.…”

“…A row of bare Au atoms is directly lying below the topmost molecular chains, hence the MPc molecules are in direct contact with the gold substrate. 18 The XPS Fe-2p 3/2 core level spectra for the FePc molecules adsorbed onto the Au(110) surface kept at room temperature, as a function of FePc coverage up to the formation of a 20 nm thick film (TF), are shown in Fig. 2 (left panel).…”

“…Completion of first SL is achieved at a nominal coverage of about 3.4 Å, 6 and has been checked by LEED. 18 The Scanning Tunneling Microscopy (STM) images of the CoPc single-layer adsorbed on Au(110) were taken at the STM UHV apparatus connected to the ID08 (present ID32) beamline at the European Synchrotron Radiation Facility (ESRF).…”

“…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).…”

Examples of Molecular Self‐Assembly at Surfaces

“…Right: iron-phthalocyanine (FePc) molecules form chains whose alignment is determined by particular 'channels' on the gold surface. [ 15 ] Left-hand image reproduced with permission. [ 9 ] Copyright 2008, American Association for the Advancement of Science.…”