Origin of the contrast inversion in the STM image of CO on Cu(1 1 1)

Tiwari, Ravi K.; Otalvaro, Diana M.; Joachim, Christian; Saeys, Mark

doi:10.1016/j.susc.2009.09.017

Cited by 9 publications

(7 citation statements)

References 23 publications

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“…). For both tips we see the dip in the current image at the position of the CO molecule [35,36], where the current on top of the CO molecule is larger for the four-atom tip than for the single-atom tip owing to the larger tip area from which electrons can tunnel. Fig.…”

Section: (E))mentioning

confidence: 94%

“…The IETS calculations are then performed at the point. [35,36], where the current on top of the CO molecule is larger for the four-atom tip than for the single-atom tip owing to the larger tip area from which electrons can tunnel. Figure 1(e) shows the IETS for CO molecules obtained with the singleatom tip [37] and the four-atom tip, where identical current set points are used for both tips.…”

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confidence: 99%

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Influence of atomic tip structure on the intensity of inelastic tunneling spectroscopy data analyzed by combined scanning tunneling spectroscopy, force microscopy, and density functional theory

et al. 2016

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Achieving a high intensity in inelastic scanning tunneling spectroscopy (IETS) is important for precise measurements. The intensity of the IETS signal can vary by up to a factor of 3 for various tips without an apparent reason accessible by scanning tunneling microscopy (STM) alone. Here, we show that combining STM and IETS with atomic force microscopy enables carbon monoxide front-atom identification, revealing that high IETS intensities for CO/Cu(111) are obtained for single-atom tips, while the intensity drops sharply for multiatom tips. Adsorption of the CO molecule on a Cu adatom [CO/Cu/Cu(111)] such that the molecule is elevated over the substrate strongly diminishes the tip dependence of IETS intensity, showing that an elevated position channels most of the tunneling current through the CO molecule even for multiatom tips, while a large fraction of the tunneling current bypasses the CO molecule in the case of CO/Cu(111). DOI: 10.1103/PhysRevB.93.165415 Inelastic electron tunneling spectroscopy (IETS) with scanning tunneling microscopy (STM) is an effective method to analyze the vibrational modes of a single adsorbed molecule with subnanometer lateral resolution [1,2]. The vibrational energy of a molecule on a substrate strongly depends on the surrounding environment, such as the substrate structure and composition [3]. By studying these subtle changes of the vibrational energy using STM-IETS with a molecularfunctionalized tip, it has been demonstrated that STM-IETS can provide information on the inner structure of a molecule [4,5] similarly to atomic force microscopy (AFM) [6]. These advantages of STM-IETS have accelerated research in related fields [7][8][9][10][11][12][13][14][15][16]. Owing to recent progress in the theoretical description of IETS [17][18][19][20][21][22], the qualitative understanding has been improved considerably: the symmetry of the wave functions of a tip and a molecule on a substrate and a vibrational mode of the molecule are predicted to influence the efficiency of the inelastic process (γ inel ) for the tunneling current involving the molecule. In order to discuss γ inel on the basis of the intensity of IETS, we have to consider that IETS intensity is described by the multiplication of two factors: (1) the ratio of the tunneling current passing through a molecule to the total tunneling current (I molecule /I total ) and (2) the efficiency of the inelastic process (γ inel ). These factors should in principle be affected by the geometrical structure of the substrate and of the tip.The geometrical structure of a metal tip apex can be determined by using carbon monoxide (CO) front-atom identification (COFI) provided by AFM [23,24], where the tip apex of a force sensor is probed by a CO molecule that stands upright on a metal surface [inset of Fig. 1(e)]. The metallic tip apex atom has a dipole moment induced by the Smoluchowski effect [25], whose direction is the same as that of the CO molecule adsorbed on the surface [26]. Thus in the distance regime where the electrostatic int...

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Section: (E))mentioning

confidence: 94%

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confidence: 99%

Influence of atomic tip structure on the intensity of inelastic tunneling spectroscopy data analyzed by combined scanning tunneling spectroscopy, force microscopy, and density functional theory

et al. 2016

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“…This is similar to CO on Cu(111) where the molecule reduces the conductance and leads to a depression in constant-current STM images over a range of bias voltages. 53,54 Similarly, bonding of H to the Mn center of MnPc was observed to cause a depression in experimental and calculated STM images. 55…”

Section: T H Imentioning

confidence: 85%

Surface cis Effect: Influence of an Axial Ligand on Molecular Self-Assembly

Knaak

Gopakumar²,

Schwager

et al. 2016

J. Am. Chem. Soc.

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Adding ligands to molecules can have drastic and unforeseen consequences in the final products of a reaction. Recently a surface trans effect due to the weakening of a molecule-surface bond was reported. Here, we show a surface cis effect where an axial ligand at adsorbed transition-metal complexes enables lateral bonding among the molecules. In the absence of this ligand, the intermolecular interaction is repulsive and supramolecular patterns are not observed. Fe-tetramethyl-tetraazaannulene on Au(111) was investigated using low-temperature scanning tunneling microscopy and spectroscopy along with density functional theory calculations. At low coverages, the molecules remain isolated. Exposure to CO leads to axial CO bonding and induces reordering into extended clusters of chiral molecular trimers. The changed self-assembly pattern is due to a CO-induced modification of the molecular structure and the corresponding charge transfer between the molecule and the substrate, which in turn changes the lateral intermolecular forces.

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“…When CO is adsorbed on the Cu (111) surface, it was only observed as a dark depression, 97 which has been recently considered as a result of DOS depletion near the E F due to strong coupling between the 5s molecular orbital of CO and 4p z surface state of the Cu surface. 98 Similarly, an anti-bonding state between 1e 1g molecular orbital (HOMO) of benzene and Pd 4d orbitals was observed in the adsorption system of Pd(110)-c(4 Â 2)benzene. 99 Although simple situations of the molecular orbitals and bonding mechanisms of small molecules such as CO make them appropriate as prototypes for scientific exploration, the strong molecule-substrate interactions often bring many difficulties in inspecting their molecular orbitals.…”

Section: Molecule-substrate Interaction Characterizationmentioning

confidence: 92%

STM studies of single molecules: molecular orbital aspects

Yang

et al. 2011

Chem. Commun.

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As a fundamental and frequently referred concept in modern chemistry, the molecular orbital plays a vital role in the science of single molecules, which has become an active field in recent years. For the study of single molecules, scanning tunneling microscopy (STM) has been proven to be a powerful scientific technique. Utilizing specific distribution of the molecular orbitals at spatial, energy, and spin scales, STM can explore many properties of single molecule systems, such as geometrical configuration, electronic structure, magnetic polarization, and so on. Various interactions between the substrate and adsorbed molecules are also understood in terms of the molecular orbitals. Molecular engineering methods, such as mode-selective chemistry based on the molecular orbitals, and resonance tunneling between the molecular orbitals of the molecular sample and STM tip, have stimulated new advances of single molecule science.

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Origin of the contrast inversion in the STM image of CO on Cu(1 1 1)

Cited by 9 publications

References 23 publications

Influence of atomic tip structure on the intensity of inelastic tunneling spectroscopy data analyzed by combined scanning tunneling spectroscopy, force microscopy, and density functional theory

Influence of atomic tip structure on the intensity of inelastic tunneling spectroscopy data analyzed by combined scanning tunneling spectroscopy, force microscopy, and density functional theory

Surface cis Effect: Influence of an Axial Ligand on Molecular Self-Assembly

STM studies of single molecules: molecular orbital aspects

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