Interactions and dynamics of benzene on Cu{111} at low temperature

Stranick, Stephan J.; Kamna, M. M.; Weiss, Paul S.

doi:10.1016/0039-6028(95)00529-3

Cited by 119 publications

(138 citation statements)

References 59 publications

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“…5). This can be compared with recent results for the Cu(111)/benzene system studied by Stranick et al [16,17]. They ascribe the formation of benzene islands close to steps to the interaction between benzene molecules and the modulated LDOS close to the step.…”

Section: Discussionmentioning

confidence: 60%

Long-range interaction between adatoms at the Cu(111) surface imaged by scanning tunnelling microscopy

Wahlström¹,

Ekvall²,

Olin³

et al. 1998

Applied Physics A: Materials Science & Processing

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We have used an ultra-high vacuum variable temperature scanning tunnelling microscope to study the Cu(111) surface at temperatures from 90 K to 300 K. After the sample is heated to 900 K, adatoms enriched at the surface. Around these adatoms ring-formed standing-wave features can be seen in the local density of states (LDOS). When more than one of the adatoms were imaged it became evident that the adatoms preferred lateral distances in which they shared LDOS standing-wave maximas. This means that adatoms were positioned at multiples of half the Fermi wavelength (15 Å) from each other. We ascribe the interaction that gave these results to the surface state electrons which form the LDOS standing waves. Furthermore the interaction was longranged (at least in the order of 80 Å), oscillatory with the pair distance, and present at high temperatures since the adatoms stick to the surface above room temperature.Interactions of adatoms at a surface are important as they take part in many processes such as diffusion, cluster formation, and film growth. The interaction between the adatoms can, at close distances, be of different types of direct forces: an overlap between the atoms, which gives an essentially chemical bond, a van der Waals attraction, or a dipole-dipole interaction if the atom-substrate bond is polar. This article will, however, be concerned with adatoms at longer distances where the interaction between adatoms has to be indirect, mediated by the substrate electrons. These long-range interactions at surfaces have been studied since 1967 when Grimley investigated the force between two adatoms mediated by the electrons of the conduction band; these electrons are shared by the adatoms [1]. Grimley found the interaction to be both oscillatory and long range. His results where later refined [2][3][4][5] and confirmed by field ion microscopy (FIM) experiments, where adatom pairs were imaged at a FIM tip [6,7]. A FIM suffers from the drawback of using singlecrystal tips instead of flat single-crystal surfaces. However, the same interactions can be investigated by a scanning tunnelling microscope (STM), which is known for its high lateral resolution. The use of a flat sample and an STM has many advantages compared to FIM: larger areas can be imaged, it is easy to obtain clear images of atoms, cluster formations, step edges and dislocations. This makes it possible to investigate interactions between adatoms and all these features. The main drawback of using an STM is that the system studied has to be selected so the adatoms do not move laterally when imaged, this means that they have to stick quite well to the surface.

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Section: Discussionmentioning

confidence: 60%

Long-range interaction between adatoms at the Cu(111) surface imaged by scanning tunnelling microscopy

Wahlström¹,

Ekvall²,

Olin³

et al. 1998

Applied Physics A: Materials Science & Processing

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“…This is what was found on Cu terraces at T =77 K. 16,17 Further, the finding that the location of Bz adsorbate to some extent decouple from the underlying copper lattice, leaves the stage open for other phenomena to dominate the interplay between molecules at higher coverages and determine the 2D surface assembly of the Bz adsorbates.…”

Section: Surface Assemblymentioning

confidence: 56%

“…[5][6][7][8][9][10] In a first attempt to understand the details of the adsorption and self-organization of acene derivatives, we here consider the simplest member of this family, the monocyclic aromatic ring benzene ͑Bz͒. Adsorption of Bz on Cu͑111͒ displays remarkable molecular-adsorption dynamics with observations [11][12][13][14][15][16][17] of high mobility of individual Bz molecules at low temperatures, as well as a possibility for the Bz adsorbates to condense into two coexisting adsorbate-overlayer phases, C1 and C2, characterized by hexagonal nets with lattice constants 10.24 Å and 6.74 Å, respectively. For Bz, as for AQ, the adsorption energy arises primarily from vdW interactions with conduction electrons on the Cu surface, with very small orbital changes and substrate-adsorbate charge transfers.…”

Section: Introductionmentioning

confidence: 99%

Rings sliding on a honeycomb network: Adsorption contours, interactions, and assembly of benzene on Cu(111)

2009

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Using a van der Waals density functional ͑vdW-DF͒ ͓Phys. Rev. Lett. 92, 246401 ͑2004͔͒, we perform ab initio calculations for the adsorption energy of benzene ͑Bz͒ on Cu͑111͒ as a function of lateral position and height. We find that the vdW-DF inclusion of nonlocal correlations ͑responsible for dispersive interactions͒ changes the relative stability of eight binding-position options and increases the binding energy by over an order of magnitude, achieving good agreement with experiment. The admolecules can move almost freely along a honeycomb web of "corridors" passing between fcc and hcp hollow sites via bridge sites. Our diffusion barriers ͑for dilute and two condensed adsorbate phases͒ are consistent with experimental observations. Further vdW-DF calculations suggest that the more compact ͑hexagonal͒ Bz-overlayer phase, with lattice constant a = 6.74 Å, is due to direct Bz-Bz vdW attraction, which extends to ϳ8 Å. We attribute the second, sparser hexagonal Bz phase, with a = 10.24 Å, to indirect electronic interactions mediated by the metallic surface state on Cu͑111͒. To support this claim, we use a formal Harris-functional approach to evaluate nonperturbationally the asymptotic form of this indirect interaction. Thus, we can account well for benzene self-organization on Cu͑111͒.

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“…This complex situation is in marked contrast with the close-packed Cu(111) surface, where the PES for the adsorbed Bz and Np is essentially flat and their ADD dynamics are well understood [13]. TPD studies of Bz/Cu(111) exhibit a single peak in the desorption spectrum, and STM investigations suggest that the Bz molecules are freely diffusing on the Cu(111) surface at a low temperature [28]. On the Cu(443) surface, the preferred adsorption on step edges can be explained by reactive dangling bonds, and therefore both Bz and Np are able to form weak chemical bonds with the Cu atoms there.…”

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confidence: 77%

Steps or Terraces? Dynamics of Aromatic Hydrocarbons Adsorbed at Vicinal Metal Surfaces

2015

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The study of how molecules adsorb, diffuse, interact, and desorb from imperfect surfaces is essential for a complete understanding of elementary surface processes under relevant pressure and temperature conditions. Here we use first-principles calculations to study the adsorption of benzene and naphthalene on a vicinal Cu(443) surface with the aim to gain insight into the behavior of aromatic hydrocarbons on realistic surfaces at a finite temperature. Upon strong adsorption at step edges at a low temperature, the molecules then migrate from the step to the (111) terraces, where they can freely diffuse parallel to the step edge. This migration happens at temperatures well below the onset of desorption, suggesting a more complex dynamical picture than previously proposed from temperature-programed desorption studies. The increase of the adsorption strength observed in experiments for Cu(443) when compared to Cu (111) is explained by a stronger long-range van der Waals attraction between the hydrocarbons and the step edges of the Cu(443) surface. Our calculations highlight the need for time-resolved experimental studies to fully understand the dynamics of molecular layers on surfaces.

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Interactions and dynamics of benzene on Cu{111} at low temperature

Cited by 119 publications

References 59 publications

Long-range interaction between adatoms at the Cu(111) surface imaged by scanning tunnelling microscopy

Long-range interaction between adatoms at the Cu(111) surface imaged by scanning tunnelling microscopy

Rings sliding on a honeycomb network: Adsorption contours, interactions, and assembly of benzene on Cu(111)

Steps or Terraces? Dynamics of Aromatic Hydrocarbons Adsorbed at Vicinal Metal Surfaces

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