Physisorption of CO on Ag(111): investigation of the monolayer and the multilayer through HREELS, ARUPS, and TDS

Hansen, Wilford N.; Bertolo, M.; Jacobi, K.

doi:10.1016/0039-6028(91)90576-e

Cited by 78 publications

(54 citation statements)

References 39 publications

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“…On the basis of ARUPS and HREELS, a disordered overlayer was suggested, where the CO molecules are adsorbed with a random orientation. 9 LEED experiments indicated a well-ordered, incommensurate overlayer 10 with intermolecular distances varying with the backgound pressure. The angle between the CO monolayer and the Ag͑111͒ lattice was pinned at 9°, which agrees with the angle we determined from the STM images.…”

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confidence: 99%

“…This finding is based on HREELS studies, revealing a CO streching frequency of 266 meV, which is typical for an on-top adsorption. 9 However, the CO is only weakly adsorbed on Ag͑111͒ with an adsorption energy of −0.28 eV, 7 and recent density functional theory calculations suggest that the adsorption energy for different sites is almost degenerate on Ag͑111͒. 4 Furthermore, the adsorption site can depend on the coverage as shown for the CO on Ni͑111͒.…”

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confidence: 99%

“…So far, studies have focused on CO-overlayer structures, which have been analyzed with a variety of techniques, such as angle-resolved ultraviolet photoemission spectroscopy ͑ARUPS͒, high-resolution electron-energy loss spectroscopy ͑HREELS͒, and low-energy electron diffraction ͑LEED͒. [8][9][10] However, it has been difficult to unravel the structure, and indeed, a widely accepted structural model is still lacking. The main difficulty related to the above mentioned methods is their nonlocal nature, which means that they provide information averaged over all surface species.…”

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confidence: 99%

“…It is therefore difficult to distinguish between signals arising from a CO monolayer ͑ML͒ and signals from CO multilayers which are supposed to have different structures on Ag͑111͒. 9,10 Hence, knowledge of the exact adsorbate coverage is a crucial point for structure determination with nonlocal methods. This problem can be avoided using scanning tunneling microscopy ͑STM͒ which probes the local density of states of a surface and thus reflects its local electronic and topographic structure.…”

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STM studies of ordered(31×31)R9°CO islands on Ag(111)

et al. 2005

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The adsorption behavior of CO on Ag͑111͒ is studied using low-temperature scanning tunneling microscopy. At submonolayer coverage, only single CO molecules are observed upon adsorption at 5 K. A further dosage leads to the formation of islands with various shapes and sizes. In addition, clusters with a diameter of about 11 Å are found that are mobile on the surface at 5 K. Though the position of the CO molecules within these clusters cannot be resolved, their size points to CO hexamers or heptamers. Well-ordered CO islands are observed only after heating the sample to 17 K, whereby two rotational domains with hexagonal ͑ ͱ 31 ϫ ͱ 31͒R9°structure are formed. A structural model is proposed in which CO hexamers represent the fundamental building blocks. The existence of two domains is explained with the alternate CO adsorption on the fcc and hcp places within the hexamers. The ͑ ͱ 31ϫ ͱ 31͒R9°superlattice is the only well-ordered CO structure found in the temperature range between 5 K and 35 K. The interaction of carbon monoxide with transition metals has attracted much interest during the past decades. One reason is certainly the importance of CO in catalytically relevant processes, where transition metals often play a crucial role. Though the fundamental binding mechanism between CO and these substrates was described already in 1964, 1 the large number of recent experimental and theoretical investigations demonstrates the actuality of this subject. [2][3][4] The central questions concern, for instance, binding sites, diffusion processes, and overlayer structures that are also important for the understanding of the CO-CO interaction. 5,6 Among the late-transition and noble-metal ͑111͒ surfaces, silver shows the weakest interaction with CO, with an adsorption energy of −0.28 eV. 4,7 Therefore, the investigation of the CO adsorption on Ag͑111͒ has proven to be very challenging. So far, studies have focused on CO-overlayer structures, which have been analyzed with a variety of techniques, such as angle-resolved ultraviolet photoemission spectroscopy ͑ARUPS͒, high-resolution electron-energy loss spectroscopy ͑HREELS͒, and low-energy electron diffraction ͑LEED͒.8-10 However, it has been difficult to unravel the structure, and indeed, a widely accepted structural model is still lacking. The main difficulty related to the above mentioned methods is their nonlocal nature, which means that they provide information averaged over all surface species. It is therefore difficult to distinguish between signals arising from a CO monolayer ͑ML͒ and signals from CO multilayers which are supposed to have different structures on Ag͑111͒.9,10 Hence, knowledge of the exact adsorbate coverage is a crucial point for structure determination with nonlocal methods. This problem can be avoided using scanning tunneling microscopy ͑STM͒ which probes the local density of states of a surface and thus reflects its local electronic and topographic structure.In the present study, STM is used to investigate the adsorption behavior of CO on Ag͑111͒ f...

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STM studies of ordered(31×31)R9°CO islands on Ag(111)

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“…have shown that CO forms a stable, physisorbed monolayer on Ag(ll1) with a desorption temperature of -50 K. [17] The observation of the CO stretch vibration (265 meV) in HREELS spectrum indicated that at least some of the physisorbed CO molecules have orientations perpendicular (or nearly so) to the surface. The latter are required for the observation of the dipole-excited energy loss peak which would otherwise be absent for CO molecules lying parallel to the surface.…”

Section: Co Binding On Ag(ll1)mentioning

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<title>State-resolved dynamics of infrared photodesorption of CO from Ag(111)</title>

et al. 1995

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1, INTRODUCTIONCurrent understanding of the dynamics of photon stimulated desorption (PSD) of molecules from surfaces has been derived in large part from state-and energy-resolved probes of the desorbed molecules in the gas-phase.'B2 Analogous to studies of gas-phase photodissociation, information concerning the electronic interactions and nuclear motions on the dissociative potential surface are inferred from the energy, internal state and angular distributions of the photoproducts. Of particular interest is the use of state-resolved methods to ellucidate the photodesorption mechanism which can involve substrate and/or absorbate excitations followed by facile energy transfer between the electronic and nuclear degrees of freedom. The primary concern of this work is desorption induced by photon energies well below the work function (5 1 -2 eV) which is nominally assumed to occur via a thermally activated process. From a dynamical standpoint, laser-induced surface heating results from the rapid thermalization of initially photoexcited electron-hole pairs which relax through inelastic e--e' scattering and energy transfer to lattice modes of the substrate. Desorption results from random silrface atom displacements which deposit vibrational energy in the absorbatemetal bond in excess of the b i d i n g energy.The desorption rate is highest at the maximum surface temperature (Tmz) induced by the laser pulse which can be determined with reasonable accuracy from a classical heat-diffusion model.3 -' As a result, "thermally" desorbed molecules are expected to have internal and translational energy distributions characteristic of Tmoz.State-resolved measurements performed by Buntin, et aL6 for NO/Pt(lll) at a number of photon energies between 0.65 eV and 3.49 eV have identified two desorption channels, with the "slow" velocity component exhibiting near Boltzmann rotational and translational distributions. Although the measured angular distribution, photon energy dependence and translational energiei of the slow channel are consistent with thermally activated desorption, the translational energies did not show a dependence on laser fluence as expected from the classical heat-diffusion model, i.e. Tmz cc Io. In addition, the rotational temperature (-100 K) was found to be significantly smaller than the expected surface temperature rise (Tmz = 227 K). In a related study, Prybyla, et al. observed a Boltzmann rotational state distribution for NO desorbed from Pd(ll1) at 2.33 eV (532 nm), however, the derived rotational temperature was approximately half that of the surface temperature? Such 'rotational cooling" has been attributed to strong coupling between rotation and translation induced by the molecule-surface potential and its anisotropy with respect to molecular orientation?j8In this work, we present state-resolved measurements for E t . (1.17 eV, 1064 nm) photodesorption of CO physisorbed on a Ag(ll1) surface. In contrast to NO, there-has been very little

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Chemical Reactivity and Variation in Electronic Properties of Graphene on Ni(111) and Reduced Graphene Oxide

Celasco

2019

Handbook of Graphene

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Physisorption of CO on Ag(111): investigation of the monolayer and the multilayer through HREELS, ARUPS, and TDS

Cited by 78 publications

References 39 publications

STM studies of ordered(31×31)R9°CO islands on Ag(111)

STM studies of ordered(31×31)R9°CO islands on Ag(111)

<title>State-resolved dynamics of infrared photodesorption of CO from Ag(111)</title>

Chemical Reactivity and Variation in Electronic Properties of Graphene on Ni(111) and Reduced Graphene Oxide

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