EVOLUTION OF LATERAL ORDER AND MOLECULAR REORIENTATION IN THE BENZOATE/Cu(110) SYSTEM

Abstract

Coverage-dependent adsorption studies of benzoic acid on a Cu(110) single crystal surface resulted in a sequence of novel, large periodicity structures containing differently oriented benzoate species, as shown by LEED, STM and FTIR. At low coverage, only flat-lying benzoate species are present and faceting of step edges is observed. The favorable mobility of flat-lying species results in formation of large, single domain islands with a [Formula: see text] periodicity containing four molecules per unit cell. Additional adsorption produces island growth, with single domains typically covering entire terraces and, simultaneously, addition of a fifth benzoate species per unit cell oriented perpendicular to the surface. This structure, denoted as the “α phase,” corresponds to a local coverage of θ=0.21 ML. Then, the periodicity changes to a [Formula: see text] structure with single and paired rows of upright species, retaining the dominant <4, 3> direction and large single domain sizes, in addition to six flat-lying species. The second structure, referred to as the “β phase,” corresponds to a local coverage of θ= 0.23 ML. The saturation coverage, c(8×2) structure, at θ=0.25 ML, grows in from step edges and contains only upright benzoate species. The results are interpreted in terms of the interplay between molecular orientation, site-specificity, diffusion and the intermolecular interactions favoring long range, two-dimensional order.

Electronic Mapping of Molecular Orbitals at the Molecule-Metal Interface

“…Images were obtained in constant-current mode, while spectroscopy data are current-voltage characteristics with the voltage referred to the sample. Our STM and DFT investigations on the structure show that the bonding mechanism of PyDCAH 2 is similar to that of other carboxylic acids on Cu(110) [16,[20][21][22]. The molecules bind chemically under deprotonation of one carboxyl group with each of the oxygen atoms chemisorbed on short bridge sites of the outermost copper layer, forming rows in the ½001 direction of the substrate.…”

Role of the van der Waals interactions on the bonding mechanism of pyridine on Cu(110) and Ag(110) surface: First-principles study

“…Less investigated are systems where the binding atom between the molecules and surfaces is not a sulfur or an oxygen atom ͑as a part, for instance, of a carboxylate anchoring group [14][15][16] ͒. Therefore, in the present study we focus on the bonding mechanism of a single pyridine molecule adsorbed via its nitrogen atom on Ag͑110͒ and Cu͑110͒ surfaces.…”

Adsorption and Organization of the Organic Radical 3-Carboxyproxyl on a Cu(110) Surface: A Combined STM, RAIRS, and DFT Study

“…Such dehydrogenation of a carboxylic acid group has been observed for a range of species on Cu(110). [25][26][27][28][29][30][31][32][33] In order to obtain information on the orientation, the adsorption site, and the molecule-metal bonds, we performed periodic DFT calculations using the VASP code. 37 Our calculations explored a number of adsorption sites and orientations as presented in Scheme 2, investigating the preferred adsorption site for bonding via the carboxylate or the NO group.…”

“…24 Second, the carboxyl (COOH) functionality of the 3CP molecule enjoys a strong bonding interaction with copper, thus offering a means of anchoring the molecule robustly to the surface as has been shown in previous studies for different molecules involving such a functional group. [25][26][27][28][29][30][31][32][33] Surface bonding via the carboxylic acid group reduces the possibility of a significant interaction between the N-O group and the surface and thus provides a good chance of preserving the unpaired spin. Importantly, the spin on the nitroxide is further stabilized by the presence of methyl groups attached to the ring.…”