Vibrational spectroscopy and theory of alkali metal adsorption and co-adsorption on single-crystal surfaces

Politano, Antonio; Chiarello, G.; Benedek, G.; Chulkov, Eugene V.; Echenique, Pedro M.

doi:10.1016/j.surfrep.2013.07.001

Cited by 59 publications

(40 citation statements)

References 742 publications

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“…Although rhodium is an outstanding catalyst in several reactions, for example ring opening of methylcyclopentane, hydrogenation of benzene and CO and is widely used in automobile catalytic converters, its efficiency needs to be enhanced by different additives, like alkali metals [1] or early transition-metal oxides, such as different molybdenum oxides [2]. Mo containing additives are known to increase the catalytic activity of Rh nanoparticles in the hydroformylation reaction of ethylene and propylene [3].…”

Section: Introductionmentioning

confidence: 99%

Enhanced dispersion and the reactivity of atomically thin Rh layers supported by molybdenum oxide films

Szenti

Bugyi

2015

Surface Science

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Section: Introductionmentioning

confidence: 99%

Enhanced dispersion and the reactivity of atomically thin Rh layers supported by molybdenum oxide films

Szenti

Bugyi

2015

Surface Science

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“…where E loss is the energy loss and α s is the electron scattering angle [23]. Accordingly, the integration window in reciprocal space is [24] Δq…”

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confidence: 99%

Interplay of Surface and Dirac Plasmons in Topological Insulators: The Case ofBi2Se3

et al. 2015

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We have investigated plasmonic excitations at the surface of Bi 2 Se 3 ð0001Þ via high-resolution electron energy loss spectroscopy. For low parallel momentum transfer q ∥ , the loss spectrum shows a distinctive feature peaked at 104 meV. This mode varies weakly with q ∥ . The behavior of its intensity as a function of primary energy and scattering angle indicates that it is a surface plasmon. At larger momenta (q ∥ ∼ 0.04 Å −1 ), an additional peak, attributed to the Dirac plasmon, becomes clearly defined in the loss spectrum. Momentum-resolved loss spectra provide evidence of the mutual interaction between the surface plasmon and the [4][5][6] have promising capabilities in regard to engineering high-speed plasmonic and optoelectronic devices [7,8].The growth of TI samples belonging to the class of chalcogenides inherently involves the presence of vacancies. Thus, in most cases, the Fermi level is shifted from the bulk band gap and pinned by the bulk states occupied by doping electrons or holes. These bulk carriers give rise to their own three-dimensional electron gas (3DEG), which is well known to have plasmonic excitations characterized by the bulk plasmon energy ω p . In this matter, the frequency of the surface plasmon ω sp is related to the bulk plasmon energy ω p (for a simple planar interface ω sp ¼ ω p = ffiffiffiffiffiffiffiffiffiffiffiffi ffi 1 þ ε b p , where ε b is the dielectric constant of the background medium of the 3DEG) [9]. In turn, the value of ω p is determined by the bulk concentration of charge carriers [10]. From the reported values of the carrier concentration, the respective values of ω p , and the dielectric screening by the surrounding medium [11,12], one could expect that ω sp is in the ∼100 meV energy range and it should coexist with the collective excitation of the two-dimensional electron gas (2DEG) arising from electrons of topological surface states (the so-called Dirac plasmon) [13,14]. As a result, the intriguing interplay of the surfaceplasmon and Dirac-plasmon modes as functions of in-plane momentum q ∥ arises.Recently, optical techniques have been used [12,15,16] to investigate plasmon modes of thin films and microribbons of Bi 2 Se 3 . The Dirac plasmon has been observed in Bi 2 Se 3 microribbons [15], while the bulk plasmon has been reported in thin films [11,17,18]. However, optical techniques are not suited to the investigation of the momentum dependence of plasmonic excitations and, thus, the nature and the dispersion of low-energy collective excitations in TIs in a finite momentum range is hitherto unexplored.Here, we examine the surface collective electronic excitations in Bi 2 Se 3 by means of HREELS, which allows probing of an extended momentum range. Our HREELS measurements provide direct evidence for the coexistence of two low-energy collective modes: the surface plasmon, whose origin is due to a nonzero density of 3D doping electrons, and the Dirac plasmon of the 2DEG formed by electrons residing in a topological surface-state band. The surface plasmon, whose...

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“…Vibrational spectroscopy is a powerful tool for identifying chemisorbed species at surfaces and, moreover, the species generated by surface reactions [29]. In particular, highresolution electron energy loss spectroscopy (HREELS) is particularly suitable for such aims for its surface sensitivity and its high energy resolution [30].…”

Section: Resultsmentioning

confidence: 99%

Probing growth dynamics of graphene/Ru(0001) and the effects of air exposure by means of helium atom scattering

Politano

2015

Surface Science

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Vibrational spectroscopy and theory of alkali metal adsorption and co-adsorption on single-crystal surfaces

Cited by 59 publications

References 742 publications

Enhanced dispersion and the reactivity of atomically thin Rh layers supported by molybdenum oxide films

Enhanced dispersion and the reactivity of atomically thin Rh layers supported by molybdenum oxide films

Interplay of Surface and Dirac Plasmons in Topological Insulators: The Case ofBi2Se3

Probing growth dynamics of graphene/Ru(0001) and the effects of air exposure by means of helium atom scattering

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