Symmetry reduction of metal phthalocyanines on metals

Chang, Shang‐Hung; Kück, S.; Brede, Jens; Lichtenstein, Leonid; Hoffmann, Germar; Wiesendanger, R.

doi:10.1103/physrevb.78.233409

Cited by 110 publications

(140 citation statements)

References 30 publications

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“…In contrast to the planar MPcs, the Ti and O atoms of TiOPc are located above the molecular plane. The aromatic Pc prefers to adopt a flat-lying configuration when adsorbed onto metal or graphite surfaces as reported in previous works [18]. The molecular configurations of non-planar TiOPc on surface could be O atom pointing to the vacuum (O-up with dipole pointing to the substrate) and the substrate (O-down with dipole pointing to the vacuum) as shown in Figure 1 (111) surface.…”

Section: Resultsmentioning

confidence: 99%

“…The observed LCPD shifts are in opposite direction and are consistent with the oppositely oriented permanent dipole induced by the TiOPc-pro and TiOPc-dep molecules, respectively. Similar to the CuPc/Cu(111) system [18], TiOPc molecules tend to cover the steps first, which indicates a weak interaction between the molecules and the substrate. We believe that the dipole induced by charge transfer between TiOPc molecules and the Cu(111) surface may play a minor role comparing to the large permanent dipole of the TiOPc molecules.…”

Section: Resultsmentioning

confidence: 99%

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Orientation of molecular interface dipole on metal surface investigated by noncontact atomic force microscopy

et al. 2013

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We investigated the orientations of interface dipole moments of individual non-planar titanyl phthalocyanine (TiOPc) molecules on Cu(111) and Cu(100) substrates using scanning tunneling microscope (STM) and noncontact atomic force microscope (NC-AFM). The dipole moment orientations corresponding to two different configurations of individual TiOPc molecules were determined unambiguously. The correlation between the actual molecular structures and the corresponding STM topographies is proposed based on the sub-molecular resolution imaging and local contact potential difference (LCPD) measurements. Comparing with the pristine substrate, the LCPD shift due to the adsorption of non-planar molecule is dependent on the permanent molecular dipole, the charge transfer between the surface and the molecule, and the molecular configurations. This work would shed light on tailoring interfacial electronic properties and controlling local physical properties via polar molecule adsorption. titanyl phthalocyanine, interface dipole, non-contact atomic force microscopy, scanning tunneling microscopy, Kelvin probe force microscopy Citation:Yuan B K, Chen P C, Zhang J, et al. Orientation of molecular interface dipole on metal surface investigated by noncontact atomic force microscopy. Chin Sci Bull, 2013Bull, , 58: 36303635, doi: 10.1007 Interface dipoles induced by self-assembly of organic molecules on metal surfaces play an important role in controlling the surface and/or interface properties, especially in the modification of work function of the metal substrate and the energy-level alignment of organic semiconductor with the metal Fermi level [1,2]. Interface dipole is strongly influenced by the permanent dipole of the organic molecule and the "bonding" dipole induced by the molecule-metal interaction [3][4][5][6]. To understand the energy-level alignment at the interface and design interfaces with desired properties, atomic level investigations on the molecular structures of organic adsorbates and interfacial electronic structures are highly required and challenging. Metal phthalocyanines (MPcs), together with their derivatives, have attracted great interest over the past years because of their unique optical and electrical properties [7]. Non-planar MPcs, such as titanyl phthalocyanine (TiOPc), tin phthalocyanine (SnPc) [8], vanadyl phthalocyanine (VOPc) [9,10], chloroaluminum phthalocyanine (ClAlPc) [5] and chlorogallium phthalocyanine (GaClPc) [3], may adsorb on metal surface with two opposite molecular orientations, which give rise to different dipole moments ( Figure 1(b)). Different adsorption configurations have significant influence on the functionalities of molecules and surface and/or interface properties. However, the studies on the effects of the non-planar molecular structure and interfacial electronic structure on interface dipole are still limited. It is thus important to investigate the charge redistribution across the molecule and the metal substrate and to determine the orientations of interface dipole mome...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Orientation of molecular interface dipole on metal surface investigated by noncontact atomic force microscopy

et al. 2013

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“…The observed molecular appearance is found to be mainly independent of the polarity and value of the bias voltage in the range of À1.0 V to +1.4 V. Therefore, it is reasonable to assume that the appearance of Ni-TTBPBP on Cu(111) in STM is dominated by the topography of the molecule and not by its electronic structure. 21,40,41 To facilitate the identification of intramolecular features, the STM image in Fig. 3c is superimposed with scaled models of Ni-TTBPBP.…”

Section: Resultsmentioning

confidence: 99%

Self-assembly and coverage dependent thermally induced conformational changes of Ni(ii)-meso-tetrakis (4-tert-butylphenyl) benzoporphyrin on Cu(111)

Zhang

Lepper

Stark

et al. 2015

Phys. Chem. Chem. Phys.

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A systematic scanning tunnelling microscopy investigation of the self-assembly and of thermally induced conformational changes of Ni(II)-meso-tetrakis (4-tert-butylphenyl) benzoporphyrin (Ni-TTBPBP) onCu (111) is presented. At room temperature, Ni-TTBPBPs diffuse on the surface and self-assemble into ordered islands with well-defined registry to the substrate, with two different azimuthal orientations. The formation of the characteristic supramolecular structure is attributed to van der Waals interactions between the tert-butyl groups. Upon moderate heating, the intramolecular conformation changes irreversibly due to a dehydrogenative intramolecular aryl-aryl coupling reaction. This reaction is coverage dependent, with a lower rate at higher initial coverage; this behaviour is attributed to a stabilization of Ni-TTBPBP in the ordered islands at higher coverage.

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“…At this coverage, CoPc molecules are well separated from one another. This might reflect a random distribution of CoPc on the surface produced by a gas-like phase existing at room temperature, but could also be related 14,15 or even for the tetrapyridyl-porphyrin molecule. 16 In the high-resolution image of Figure 1b acquired at -1 V, the molecules have a four-lobe pattern with an apparent width of 18 Å, consistent with the known structure of the molecule.…”

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confidence: 99%

Direct Observation of the Tunneling Channels of a Chemisorbed Molecule

Heinrich

Iacoviță

Brumme

et al. 2010

J. Phys. Chem. Lett.

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We exploit several scanning tunneling microscopy (STM) techniques, such as atom manipulated scans and constant-height scans, to atomically resolve the adsorption geometry of isolated cobalt-phthalocyanine (CoPc) molecules on a copper (111) surface and to obtain proper low-temperature maps of the molecular conductance. By comparing these crucial findings to density functional calculations, we then provide fresh insight into the CoPc-metal interface. This innovative STM study should be applicable to a wide variety of molecules relevant for molecular electronics.SECTION Surfaces, Interfaces, Catalysis U nderstanding electron transport in hybrid metalorganic devices is fundamental to the emerging technology of molecular electronics.1 Functional molecules are in fact bound to replace diodes, transistors, and switches to answer the multiple tasks of electronic circuits. Phthalocyanine (Pc) and porphyrin derivatives have been most studied in this context, also because of their potential interest for spin-dependent electronics, 2,3 and optoelectronics. 4 The contact between a conductor and a molecule is a decisive factor for the quality of these nanoscale devices since it modifies the properties of the molecule and therefore its functionalities. For this reason, the metal-molecule contact is one of the most urgent matters to address in molecular electronics. One way to study this is to focus on model playgrounds such as single molecules adsorbed on pristine metal surfaces. Recent scanning tunneling microscopy and spectroscopy (STM and STS) studies have evidenced how the adsorption site, 5,6 the close environment, 7-9 and conformational changes, 10-12 of molecules can influence their conductance and spin-polarization.In this letter we wish to go one step further and show how to gather crucial information on the metal-molecule interface that is usually inaccessible to STM. For this purpose we use low-temperature STM and STS to investigate a common dye molecule such as single cobalt-phthalocyanine (CoPc) on a copper (111) surface. Compared to previous studies, we exploit several innovative techniques in relation to single molecules, such as atom-manipulated scans and constant-height scans. In this way we are able to determine the adsorption site of a single CoPc and identify in a reliable way its major conductance channels with a high intramolecular resolution. By comparing these crucial parameters to density functional calculations, we are then in a favorable position to accurately describe, from a chemical viewpoint, the molecule-metal contact and to identify the origin of the conductance channels observed. This experiment may serve as an example for future investigations of single molecules at the atomic level.The measurements were carried out with a low-temperature STM operating below 5 Â 10 -11 mbar. After cleaning the Cu(111) surface by argon ion bombardment and annealing, CoPc was sublimated from a crucible containing a 99.5% pure powder heated to at least 400°C, resulting in an average coverage of 0.03 mon...

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Symmetry reduction of metal phthalocyanines on metals

Cited by 110 publications

References 30 publications

Orientation of molecular interface dipole on metal surface investigated by noncontact atomic force microscopy

Orientation of molecular interface dipole on metal surface investigated by noncontact atomic force microscopy

Self-assembly and coverage dependent thermally induced conformational changes of Ni(ii)-meso-tetrakis (4-tert-butylphenyl) benzoporphyrin on Cu(111)

Direct Observation of the Tunneling Channels of a Chemisorbed Molecule

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