Nanoscale Origin of Defects at Metal/Molecule Engineered Interfaces

Nirmalraj, Peter N.; Schmid, Heinz; Gotsmann, Bernd; Riel, Heike

doi:10.1021/la3046109

Cited by 12 publications

(21 citation statements)

References 42 publications

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“…Our data and analysis complements recent STM studies of molecule-induced rearrangements and adatom migration on gold, 14,[28][29][30][31][32][33] which investigate the effect of surface features including grain boundaries and pores. 20,34 We calculate a barrier of 3 eV for complete gold atom unbinding, consistent with the upper bound of literature values that range from approx. 1 eV to 3 eV, [35][36][37] depending on the method used to estimate binding strengths.…”

Section: Introductionsupporting

confidence: 86%

Formation Mechanism of Metal–Molecule–Metal Junctions: Molecule-Assisted Migration on Metal Defects

et al. 2015

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Activation energies E a measured from molecular exchange experiments are combined with atomic-scale calculations to describe the migration of bare Au atoms and Au-alkanethiolate species on gold nanoparticle surfaces during ligand exchange for the creation of metal-molecule-metal junctions. It is well known that Au atoms and alkanethiol-Au species can diffuse on gold with sub-1 eV barriers, and surface restructuring is crucial for self-assembled monolayer (SAM) formation, for interlinking nanoparticles and in contacting nanoparticles to electrodes. In the present work, computer simulations reveal that naturally occurring ridges and adlayers on Au(111) are etched and resculpted by migration of alkanethiolate-Au species towards high coordination kink sites at surface step edges. The calculated energy barrier E b for diffusion via step edges is 0.4-0.7 eV, close to the experimentally-measured E a of 0.5-0.7 eV. By contrast, putative migration from isolated nine-coordinated terrace sites and complete Au unbinding from the surface incur significantly larger barriers of +1 and +3 eV, respectively. Molecular van der Waals's packing energies are calculated to have negligible effect on migration barriers for typically-used molecules (length < 2.5nm), indicating that migration inside SAMs does not change the size of the migration barrier. We use the computational methodology to propose a means of creating Au nanoparticle arrays via selective replacement of citrate protector molecules by thiocyanate linker molecules on surface step sites. This work also outlines the possibility of using Au/Pt alloys as possible candidates for creation of contacts that are well-formed and long-lived, due to the superior stability of Pt interfaces against atomic migration.

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Section: Introductionsupporting

confidence: 86%

Formation Mechanism of Metal–Molecule–Metal Junctions: Molecule-Assisted Migration on Metal Defects

et al. 2015

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“…1h) reduces the computed mobility of the C 60 on both spacer-coated and bare gold (for details see Supplementary Section 8.5). The in situ STM observations and molecular dynamics simulations of C 60 dynamics on bare and spacer-coated gold and previous reports of C 60 dynamics on gold in low-density liquids 13,24 confirm that silicone oil plays a dominant role in reducing molecular motion.…”

Section: Tracking C 60 Dynamics On Solid Surfaces In Silicone Oilsupporting

confidence: 76%

“…n-C 30 H 62 (solubilized in 1-phenyloctane) spray-deposited on Au(111) (Methods) at room temperature 24 forms close-packed two-dimensional lamellar structures 25,26 . The formation of ordered alkyl-organic layers and their lower dielectric constant (∼2) in comparison with inorganic spacers (NaCl, ε:∼6) make them excellent electronic decoupling platforms.…”

Section: Organic Spacer/gold Interaction In Liquidsmentioning

confidence: 99%

“…The geometry, intermolecular mechanics and electronic structure of C 60 molecular ensembles directly coupled to noble metals in low-density liquids have been discussed at length 13,24,29 . Here, we focus on the structure, dynamics and energetics of single C 60 molecules adsorbed on spacer-coated Au(111) in the high-density liquid silicone oil.…”

Section: Tracking C 60 Dynamics On Solid Surfaces In Silicone Oilmentioning

confidence: 99%

“…The structure of the C 60 molecules remains unchanged but a comparable drop in mobility was observed that contradicts previous in situ STM observations of C 60 dynamics on defect-free Au(111) (ref. 24) in low-density solvents (n-tetradecane) 13 , where the molecules exhibited high mobility at room temperature. To resolve this puzzling finding of reduced molecular mobility in silicone oil, we rely on molecular dynamics simulations of neat silicone oil (described in detail in Supplementary Section 8.3) that highlight the rigidity of the silicone oil, with a low root mean square fluctuation of (1.2 ± 0.3) Å, computed in the atomic positions, and a large favourable intermolecular packing energy of (−125.6 ± 4.3) kcal mol −1 .…”

Section: Tracking C 60 Dynamics On Solid Surfaces In Silicone Oilmentioning

confidence: 99%

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Nanoelectrical analysis of single molecules and atomic-scale materials at the solid/liquid interface

et al. 2014

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Evaluating the built-in functionality of nanomaterials under practical conditions is central for their proposed integration as active components in next-generation electronics. Low-dimensional materials from single atoms to molecules have been consistently resolved and manipulated under ultrahigh vacuum at low temperatures. At room temperature, atomic-scale imaging has also been performed by probing materials at the solid/liquid interface. We exploit this electrical interface to develop a robust electronic decoupling platform that provides precise information on molecular energy levels recorded using in situ scanning tunnelling microscopy/spectroscopy with high spatial and energy resolution in a high-density liquid environment. Our experimental findings, supported by ab initio electronic structure calculations and atomic-scale molecular dynamics simulations, reveal direct mapping of single-molecule structure and resonance states at the solid/liquid interface. We further extend this approach to resolve the electronic structure of graphene monolayers at atomic length scales under standard room-temperature operating conditions.T he elemental properties of carbon nanostructures are environment dependent. Interpreting the synergism between electronically active nanomaterials and their local chemical domain is pivotal to both scientific and technological interests. Scanning probe microscopy operated at cryogenic conditions with functionalized metal tips 1,2 in combination with inorganic decoupling platforms 3,4 is a widely adopted technique to examine the intramolecular structure of organic materials. In addition to probing matter under ultrahigh-vacuum conditions, scanning tunnelling microscopy (STM) operated at the solid/liquid interface 5-11 has previously been demonstrated to record real-time molecular dynamics 7,12-14 , register ultrafast chemical reactions 8,15 , probe the structure of supra-molecular architectures [16][17][18] and chemical-fieldeffect transistors 19 , and perform spectral analysis of molecules 6,13,20 and real-space visualization of biomolecules 5 at room temperature. It would be highly attractive to capitalize on principal findings from these two research disciplines to probe the precise electronic states in liquids and quantitatively describe the functionality of single molecules and two-dimensional nanostructures. The experimental challenge lies in addressing the electrochemical congestion present at the solid/liquid electrical interface at room temperature, which stems from the high mobility of organic molecules on metals, the dynamics of the solvent that serves as a liquid sheath and the detrimental effects of the metallic platform due to mixing of metal bands with discrete molecular electronic states 21 . A potential strategy is to employ nonpolar, highly viscous liquid sheaths with low affinity towards the substrate and to engineer a spacer layer 3,22,23 that electrically disconnects the organic material of interest from metal-induced perturbations. The bottom-up construction of the spac...

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Anomalous two-step repair mechanism of Al–Cu alloy regulated by the surroundings during E-beam irradiation

Xia,

Wang,

et al. 2024

Journal of Materials Research and Technology

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Nanoscale Origin of Defects at Metal/Molecule Engineered Interfaces

Cited by 12 publications

References 42 publications

Formation Mechanism of Metal–Molecule–Metal Junctions: Molecule-Assisted Migration on Metal Defects

Formation Mechanism of Metal–Molecule–Metal Junctions: Molecule-Assisted Migration on Metal Defects

Nanoelectrical analysis of single molecules and atomic-scale materials at the solid/liquid interface

Anomalous two-step repair mechanism of Al–Cu alloy regulated by the surroundings during E-beam irradiation

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