Force Field Analysis Suggests a Lowering of Diffusion Barriers in Atomic Manipulation Due to Presence of STM Tip

Emmrich, Matthias; Schneiderbauer, Maximilian; Huber, Fritz; Weymouth, Alfred J.; Okabayashi, Norio; Giessibl, Franz J.

doi:10.1103/physrevlett.114.146101

Cited by 39 publications

(31 citation statements)

References 41 publications

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“…Next, another sharp change in the conductances occurs, while ∂ G (x) /∂x < 0, and afterwards the adatoms are imaged in their new lateral positions (see blue section 2 for monoatomic metal tip and orange section 2 for CO tip, respectively). Hence, the adatoms are laterally manipulated, after the tip has passed the center of the iron 30,38 . The scale bars in panels (a) and (b) correspond to 300 pm.…”

Section: (B)mentioning

confidence: 99%

“…Figure 3(a) shows the COFI image (∆f (x, y)) of the monoatomic metal tip. The image reveals a tilt of the tip whose direction can be determined by investigating the bright sickle in the top part of the image 30,38 . This sickle is present because the tilted part of the tip at these (x, y)-positions is closer to the CO molecule and the interaction is already in the repulsive regime compared to the positions mirrored at the center of the CO molecule.…”

Section: (B)mentioning

confidence: 99%

“…Hence, by considering a negative charge on the oxygen atom on the surface, the analytical model describes the asymmetric lateral force curves observed in Ref. 38 with a monoatomic metal tip on CO/Cu(111).…”

Section: Co Tip Ofmentioning

confidence: 99%

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Lateral manipulation of single iron adatoms by means of combined atomic force and scanning tunneling microscopy using CO-terminated tips

et al. 2018

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CO-terminated tips currently provide the best spatial resolution obtainable in atomic force microscopy. Due to their chemical inertness, they allow to probe interactions dominated by Pauli repulsion. The small size and inertness of the oxygen front atom yields unprecedented resolution of organic molecules, metal clusters and surfaces. We study the capability of CO-terminated tips to laterally manipulate single iron adatoms on the Cu(111) surface with combined atomic force and scanning tunneling microscopy at 7 K. Furthermore, we find that even a slight asymmetry of the tip results in a distortion of the lateral force field. In addition, the influence of the tilt of the CO tip on the lateral force field is inverted compared to the use of a monoatomic metal tip which we can attribute to the inverted dipole moment of a CO tip with respect to a metal tip. Moreover, we demonstrate atom-by-atom assembly of iron clusters with CO tips while using the high-resolution capability of the CO tips in between to determine the arrangement of the individual iron atoms within the cluster. Additionally, we were able to laterally manipulate single copper and silicon adatoms without changing or losing the CO from the tip's apex. arXiv:1804.04382v3 [cond-mat.mes-hall]

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Section: (B)mentioning

confidence: 99%

Section: (B)mentioning

confidence: 99%

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Lateral manipulation of single iron adatoms by means of combined atomic force and scanning tunneling microscopy using CO-terminated tips

et al. 2018

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“…Throughout the whole paper, the IET signal is normalized by the differential conductance, i.e., IETS = (d 2 I/dV 2 )/(dI/dV ) [10,14,18,20]. The tip is formed from an etched tungsten wire, cleaned by field evaporation and repeatedly poked into the Cu substrate to prepare various tip apexes [23,24,30]. The repeated poking processes probably cover the tip apex with Cu atoms.…”

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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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“…In addition to images of atomic arrangements, detailed measurements can be made of molecular orbitals [1,2], electronic structure, vibrational [3] and magnetic excitations [4]. With atomic force microscoscopy (AFM), the interaction between tip and sample is characterized, which allows for examination of the tip-apex structure [5][6][7][8]. The tip-apex structure may strongly influence the tunneling process, both when making a quantitative comparison between experimental and theoretical STM images [9], and when investigating the inelastic tunneling signal from an adsorbate species [10].…”

Section: Introductionmentioning

confidence: 99%

STM contrast of a CO dimer on a Cu(1 1 1) surface: a wave-function analysis

Gustafsson¹,

Paulsson²

2017

J. Phys.: Condens. Matter

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We present a method used to intuitively interpret the STM contrast by investigating individual wave functions originating from the substrate and tip side. We use localized basis orbital density functional theory, and propagate the wave functions into the vacuum region at a real-space grid, including averaging over the lateral reciprocal space. Optimization by means of the method of Lagrange multipliers is implemented to perform a unitary transformation of the wave functions in the middle of the vacuum region. The method enables (i) reduction of the number of contributing tip-substrate wave function combinations used in the corresponding transmission matrix, and (ii) to bundle up wave functions with similar symmetry in the lateral plane, so that (iii) an intuitive understanding of the STM contrast can be achieved. The theory is applied to a CO dimer adsorbed on a Cu(111) surface scanned by a single-atom Cu tip, whose STM image is discussed in detail by the outlined method.

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Force Field Analysis Suggests a Lowering of Diffusion Barriers in Atomic Manipulation Due to Presence of STM Tip

Cited by 39 publications

References 41 publications

Lateral manipulation of single iron adatoms by means of combined atomic force and scanning tunneling microscopy using CO-terminated tips

Lateral manipulation of single iron adatoms by means of combined atomic force and scanning tunneling microscopy using CO-terminated tips

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

STM contrast of a CO dimer on a Cu(1 1 1) surface: a wave-function analysis

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