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Activating the strong C–C σ-bond is a central problem in organic synthesis. Directly generating activated C centers by metalation of structures containing strained four-membered rings is one maneuver often employed in multistep syntheses. This usually requires high temperatures and/or precious transition metals. In this paper, we report an unprecedented C–C σ-bond activation at room temperature on Cu(111). By using bond-resolving scanning probe microscopy, we show the breaking of one of the C–C σ-bonds of a biphenylene derivative, followed by insertion of Cu from the substrate. Chemical characterization of the generated species was complemented by X-ray photoemission spectroscopy, and their reactivity was explained by density functional theory calculations. To gain further insight into this unique reactivity on other coinage metals, the reaction pathway on Ag(111) was also investigated and the results were compared with those on Cu(111). This study offers new synthetic routes that may be employed in the in situ generation of activated species for the on-surface synthesis of novel C-based nanostructures., The authors acknowledge financial support from MCIN/AEI/10.13039/501100011033 (Grants PID2019-107338RB-C62, PID2019-107338RB-C63, PID2019-109555GB-I00, and TED2021-132388B-C43), the Basque Government (IT1591-22 and PIBA19-0004), the Spanish Research Council (ILINKC20002), the European Union’s Horizon 2020 research and innovation program (Grant 863098 and Marie Skłodowska-Curie Actions Individual Fellowship 101022150), and the Xunta de Galicia (Centro Singular de Investigación de Galicia, 2019-2022, Grant ED431G2019/03). A.P.P. thanks the UAEU for an internal start-up grant (31S410).

One-dimensional (1D) metal–organic (MO) nanowires are captivating from fundamental and technological perspectives due to their distinctive magnetic and electronic properties. The solvent-free synthesis of such nanomaterials on catalytic surfaces provides a unique approach for fabricating low-dimensional single-layer materials with atomic precision and low amount of defects. A detailed understanding of the electronic structure of MO polymers such as band gap and dispersive bands is critical for their prospective implementation into nanodevices such as spin sensors or field-effect transistors. Here, we have performed the on-surface reaction of quinoidal ligands with single cobalt atoms (Co-QDI) on a vicinal Au(788) surface in ultra-high vacuum. This procedure promotes the growth and uniaxial alignment of Co-QDI MO chains along the surface atomic steps, while permitting the mapping of their electronic properties with space-averaging angle-resolved photoemission spectroscopy. In the direction parallel to the principal chain axis, a well-defined 1D band structure with weakly dispersive and dispersive bands is observed, confirming a pronounced electron delocalization. Low-temperature scanning tunneling microscopy/spectroscopy delves into the atomically precise structure of the nanowires and elucidates their narrow bandgap. These findings are supported with GW0 band structure calculations showing that the observed electronic bands emanate from the efficient hybridization of Co(3d) and molecular orbitals. Our work paves the way towards a systematic search of similar 1D π–d hybridized MO chains with tunable electronic and magnetic properties defined by the transition or rare earth metal atom of choice., Financial support was provided from the Spanish Research Council CSIC through I-LINK C20002; grants PID2019-107338RB-C63, PID2019-103910GB-100 and PID2020-116093RB-C44 funded by MCIN/AEI/10.13039/501100011033. We further thank support from the Basque Government, grants IT-1591-22, IT-1527-22, IT-1246-19 and IT-1260-19 as well as Universidad del País Vasco grant GIU18/138.

Steps at metal surfaces may influence energetics and kinetics of catalytic reactions in unexpected ways. Here, we report a significant reduction of the CO saturation coverage in Pd vicinal surfaces, which in turn is relevant for the light-off of the CO oxidation reaction. The study is based on a systematic investigation of CO adsorption on vicinal Pd(111) surfaces making use of a curved Pd crystal. A combined X-ray Photoelectron Spectroscopy and DFT analysis allows us to demonstrate that an entire row of atomic sites under Pd steps remains free of CO upon saturation at 300 K, leading to a step-density-dependent reduction of CO coverage that correlates with the observed decrease of the light-off temperature during CO oxidation in vicinal Pd surfaces., We acknowledge financial support from the Spanish Ministry of Science and Innovation (Grants MAT-2017-88374-P, PID2019-107338RB-C63, PID2020-116093RB-C44), the Basque Government (Grants IT-1255-19), the Knut and Alice Wallenberg foundation (DNR KAW 2015.0058 ”Atomistic Design of new Catalysts”), and the Swedish Research Council (DNR 349-2011-6491 “Catalysis on the Atomic Scale”). Financial support is acknowledged from the Swedish Research Council (2016-5234). The DFT calculations were performed at C3SE (Göteborg) via a SNIC grant. We acknowledge MAX IV Laboratory support, in particular Alexei Preobrajenski, for their help in synchrotron experiments, which were carried out at the FlexPES beamline under Proposal 20190717. Research conducted at MAX IV, a Swedish national user facility, is supported by the Swedish Research council under contract 2018-07152, the Swedish Governmental Agency for Innovation Systems under contract 2018-04969, and Formas under contract 2019-02496. Moreover, the research leading to this result has been supported by the project CALIPSOplus under the Grant Agreement 730872 from the EU Framework Programme for Research and Innovation HORIZON 2020.

Curved crystals are a simple but powerful approach to bridge the gap between single crystal surfaces and nanoparticle catalysts, by allowing a rational assessment of the role of active step sites in gas-surface reactions. Using a curved Rh(111) crystal, here, we investigate the effect of A-type (square geometry) and B-type (triangular geometry) atomic packing of steps on the catalytic CO oxidation on Rh at millibar pressures. Imaging the crystal during reaction ignition with laser-induced CO2 fluorescence demonstrates a two-step process, where B-steps ignite at lower temperature than A-steps. Such fundamental dissimilarity is explained in ambient pressure X-ray photoemission (AP-XPS) experiments, which reveal partial CO desorption and oxygen buildup only at B-steps. AP-XPS also proves that A-B step asymmetries extend to the active stage: at A-steps, low-active O–Rh–O trilayers buildup immediately after ignition, while highly active chemisorbed O is the dominant species on B-type steps. We conclude that B-steps are more efficient than A-steps for the CO oxidation., We acknowledge financial support from Grant Nos. PID2020-116093RB-C44 and PID2019-107338RB-C6-3, funded by the Spanish MCIN/AEI/10.13039/501100011033 and by “ERDF A way of making Europe”, the Basque Government (Grant No. IT-1591-22), Knut and Alice Wallenberg (KAW) project “Atomistic design of new catalysts” (Project No. KAW2015.0058), the Swedish Research Council (Project No. 2018-03434), the Swedish Foundation for Strategic Research (Project No. ITM17-0045), the Å Forsk Foundation, and the Crafoord Foundation. This research used resources of the 23-ID-2 (IOS) beamline of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory, under Contract No. DE-SC0012704. Part of these experiments were performed at Circe beamline at ALBA Synchrotron with the collaboration of ALBA staff., Open Access funding is provided by the University of the Basque Country.

Curved crystal surfaces enable the systematic and accurate comparison of physical and chemical processes for a full set of vicinal crystal planes, which are probed in the very same environment. Here, we examine the early stages of the CO chemisorption on vicinal Rh(111) surfaces using a curved Rh crystal that exposes a smoothly variable density of {100} (A-type) and {111} (B-type) steps. We readily identify and quantify step and terrace species by resolving their respective core-level lines using X-ray photoelectron spectroscopy at different locations on the curved surface. Uptake experiments show similar sticking probabilities at all surface planes, subtle asymmetries between A- and B-type steps, and significantly lower saturation coverage at densely stepped surfaces as compared to the (111) plane. The analysis of the C 1s intensity variation across the curved sample allows us to discuss the adsorption geometry around the step edge., We acknowledge financial support from the Spanish Ministry of Economy (Grants MAT-2016-78293-C6, MAT-2017- 88374-P), Basque Government (Grant IT-1255-19), the VR funded Röntgen−Angström collaboration “Catalysis on the atomic scale” project number 349-2011-6491, and the Knut and Alice Wallenberg (KAW) funded project “Atomistic design of new catalysts” project number KAW 2015.0058.

Carbon nanostructures with zigzag edges exhibit unique properties—such as localized electronic states and spins—with exciting potential applications. Such nanostructures however are generally synthesized under vacuum because their zigzag edges are unstable under ambient conditions: a barrier that must be surmounted to achieve their scalable integration into devices for practical purposes. Here we show two chemical protection/deprotection strategies, demonstrated on labile, air-sensitive chiral graphene nanoribbons. Upon hydrogenation, the chiral graphene nanoribbons survive exposure to air, after which they are easily converted back to their original structure by annealing. We also approach the problem from another angle by synthesizing a form of the chiral graphene nanoribbons that is functionalized with ketone side groups. This oxidized form is chemically stable and can be converted to the pristine hydrocarbon form by hydrogenation and annealing. In both cases, the deprotected chiral graphene nanoribbons regain electronic properties similar to those of the pristine nanoribbons. We believe both approaches may be extended to other graphene nanoribbons and carbon-based nanostructures., Research was supported by MCIN/AEI/10.13039/501100011033 (grant nos PID2019-107338RB-C62 (D.P.), PID2019-107338RB-C63 (M.C. and D.G.d.O.) and FJC2019-041202-I (F.S.)); the European Union’s Horizon 2020 programme (grant nos 863098 (D.P.) and 635919 (D.G.d.O.), and Marie Skłodowska-Curie Actions Individual Fellowship no. 101022150 (T.W.)); the Gobierno Vasco (grant no. PIBA_2020_1_0036 (D.G.d.O.)); the Xunta de Galicia (Centro Singular de Investigación de Galicia, 2019–2022, grant no. ED431G2019/03 (D.P.)); the European Regional Development Fund; the Praemium Academie of the Academy of Science of the Czech Republic (GACR project no. 20-13692X (P.J.)); the Czech Nanolab Research Infrastructure supported by MEYS CR (project no. LM2018110 (P.J.)); and the Operational Programme for Research, Development and Education of the European Regional Development Fund (project no. CZ.02.1.01/0.0/0.0/16_019/0000754 (P.J.)).

Boron Nitride Nanostripes In article number 2101455, Khadiza Ali, J. Enrique Ortega, Frederik Schiller, and co‐workers explore a novel approach to nanopatterning a material with practical technological impact, namely growing hexagonal boron nitride (hBN) mono‐layers on vicinal surfaces. hBN forms a continuous atomically‐thin carpet on a curved rhodium (Rh) crystal, revealing a transformation from 2D to 1D electronic band structure at the Rh(337) orientation through electron scattering at N‐step‐Rh interface bonding points. [Image: see text]

Monolayer hexagonal boron nitride (hBN) is attracting considerable attention because of its potential applications in areas such as nano- and opto-electronics, quantum optics and nanomagnetism. However, the implementation of such functional hBN demands precise lateral nanostructuration and integration with other two-dimensional materials, and hence, novel routes of synthesis beyond exfoliation. Here, a disruptive approach is demonstrated, namely, imprinting the lateral pattern of an atomically stepped one-dimensional template into a hBN monolayer. Specifically, hBN is epitaxially grown on vicinal Rhodium (Rh) surfaces using a Rh curved crystal for a systematic exploration, which produces a periodically textured, nanostriped hBN carpet that coats Rh(111)-oriented terraces and lattice-matched Rh(337) facets with tunable width. The electronic structure reveals a nanoscale periodic modulation of the hBN atomic potential that leads to an effective lateral semiconductor multi-stripe. The potential of such atomically thin hBN heterostructure for future applications is discussed., The authors acknowledge financial support from the Spanish Ministry of Science and Innovation (Grants MAT-2017-88374-P, PID2019-107338RB-C63, MAT2017-88492-R, and Severo Ochoa CEX2019-000910-S), the CSIC (Grant 2020AEP178), the Basque Government (Grant IT-1255-19), the Marie Sklodowska-Curie European Union's Horizon 2020 program (grant MagicFACE 797109), the European Research Council (Advanced Grant 789104-eNANO), and Elettra Sincrotrone Trieste for providing access to its synchrotron radiation facilities. I.P. and F.B. acknowledge funding from EUROFEL, and D.U. from the Ministry of Science and Higher Education of the Russian Federation [Grant No. 075-15-2020-797 (13.1902.21.0024)]. A.A.M. acknowledges the German Ministry for Education and Research (Grant 05K19KER).

When doped into a certain range of charge carrier concentrations, MoS2 departs from its pristine semiconducting character to become a strongly correlated material characterized by exotic phenomena such as charge density waves or superconductivity. However, the required doping levels are typically achieved using ionic-liquid gating or air-sensitive alkali-ion intercalation, which are not compatible with standard device fabrication processes. Here, the emergence of superconductivity and a charge density wave phase in air-stable organic cation intercalated MoS2 crystals are reported. By selecting two different molecular guests, it is shown that these correlated electronic phases depend dramatically on the intercalated cation, demonstrating the potential of organic ion intercalation to finely tune the properties of 2D materials. Moreover, it is found that a fully developed zero-resistance state is not reached in few-nm-thick flakes, indicating the presence of 3D superconductive paths that are severed by the mechanical exfoliation. This behavior is ascribed to an inhomogeneous charge carrier distribution, which is probed at the nanoscale using scanning near-field optical microscopy. The results establish organic-ion intercalated MoS2 as a platform to study the emergence and modulation of correlated electronic phases., This work was supported by “la Caixa” Foundation (ID 100010434), under the agreement LCF/BQ/PI19/11690017, by the Spanish Ministerio de Ciencia e Innovación under Projects PID2019-108153GA-I00, PID2021-128004NB-C21, PID2021-123949OB-I00, PID2021-122511OB-I00. This work was also supported by the FLAG-ERA grant MULTISPIN, by the Spanish MCIN/AEI with grant number PCI2021-122038-2A. B.M.-G. thanks Gipuzkoa Council (Spain) in the frame of the Gipuzkoa Fellows Program. This work was supported by CEX2020-001038-M/AEI/10.13039/501100011033 under the Maria de Maeztu Units of Excellence Program. I.N. acknowledges financial support by the German Research Foundation (DFG) under project no. 467576442. The authors also thank SGIker Medidas Magneticas Gipuzkoa (UPV/EHU/ERDF, EU) for the technical and human support.

Graphene growth and doping are well studied on flat surfaces of various materials. To further advance the technological implementation of graphene-based systems, fundamental studies need more appropriate model templates, whose surfaces would mimic substrates with non-trivial topography. Here, using electron and photoelectron diffraction and photoemission spectroscopy as well, we demonstrate how a curved tungsten crystal covered by a thin nickel film can properly be used as such platform, allowing the fabrication and comprehensive characterization of nitrogen-doped graphene. We show the way in which nitrogen impurities prefer to embed into the graphene matrix at different areas of the curved metallic surface with variable density of atomic steps. In particular, at atomically flat regions with a strong graphene-metal interaction, pyridinic configuration is the most abundant form of dopants, while graphitic nitrogen strongly dominates in places with a weak coupling of graphene to the substrate, i.e., in the vicinity of the surface irregularities. We recognize single crystals with curvilinear surfaces as versatile platforms for the studies of not only low-dimensional materials, but also molecular adsorption, chemical reactions and catalysis on surfaces with complex structure., The authors acknowledge RFBR for research Grants No. 18-29-19178 and No. 19-32-90013, and SPbU Grant No. 73028629. A. M. acknowledges BMBF Grant No. 05K19KER. F. S., D. V. V. and J. E. O. acknowledge the Spanish Ministry of Science and Innovation (Grants MAT-2017-88374-P), Consejo Superior de Investigaciones Cientificas (Grant 2020AEP178) and the Basque Government (Grant IT-1255-19). The authors thank the Helmholtz-Zentrum Berlin für Materialien und Energie for support within the bilateral Russian-German Laboratory program. This work was supported by the German-Russian Interdisciplinary Science Center (G-RISC: M-2019b-13_r) funded by the German Federal Foreign Office via the German Academic Exchange Service (DAAD).

The question on whether there exists a unique photoelectron reference plane for a stepped solid surface is discussed on the basis of angle-resolved photoelectron spectroscopy data for Ag films grown on Pt(997). Different step morphologies at the surface and interface, revealed by low-energy electron diffraction measurements, result in distinctly different band dispersions of the sp-like quantum well states and of the Shockley surface state. Quantum well standing waves form between the parallel optical surface and interface planes, while the surface state follows the orientation of a local plane tilted with respect to the optical surface. These findings show the connection of the photoelectron reference plane with the local morphology of a solid surface and the spatial extent of the electron wave functions., This work has been partially funded through the project EUROFEL-ROADMAP ESFRI and by the Spanish Ministry of Science and Innovation (Grant No. MAT-2017-88374-P) and the Basque Government (Grant No. IT-1255-19)

Vicinal surfaces exhibiting arrays of atomic steps are frequently investigated due to their diverse physical-chemical properties and their use as growth templates. However, surfaces featuring steps with a large number of low-coordinated kink-atoms have been widely ignored, despite their higher potential for chemistry and catalysis. Here, the equilibrium structure and the electronic states of vicinal Ag(111) surfaces with densely kinked steps are investigated in a systematic way using a curved crystal. With scanning tunneling microscopy we observe an exceptional structural homogeneity of this class of vicinals, reflected in the smooth probability distribution of terrace sizes at all vicinal angles. This allows us to observe, first, a subtle evolution of the terrace-size distribution as a function of the terrace-width that challenges statistical models of step lattices, and second, lattice fluctuations around resonant modes of surface states. As shown in angle resolved photoemission experiments, surface states undergo stronger scattering by fully-kinked step-edges, which triggers the full depletion of the two-dimensional band at surfaces with relatively small vicinal angles., We acknowledge the financial support from the Spanish Ministry of Economy, Industry and Competitiveness (MINECO, Grant No. MAT2016-78293-C6 and Severo Ochoa No. SEV-2013-0295), the Basque Government (Grant No. IT-621-13), the regional Government of Aragon (RASMIA project), the CERCA Programme/Generalitat de Catalunya, and the European Regional Development Fund (ERDF) under the program Interreg V-A España-Francia-Andorra (Contract No. EFA194/16 TNSI).

The catalytic oxidation of CO on transition metals, such as Pt, is commonly viewed as a sharp transition from the CO-inhibited surface to the active metal, covered with O. However, we find that minor amounts of O are present in the CO-poisoned layer that explain why, surprisingly, CO desorbs at stepped and flat Pt crystal planes at once, regardless of the reaction conditions. Using near-ambient pressure X-ray photoemission and a curved Pt(111) crystal we probe the chemical composition at surfaces with variable step density during the CO oxidation reaction. Analysis of C and O core levels across the curved crystal reveals that, right before light-off, subsurface O builds up within (111) terraces. This is key to trigger the simultaneous ignition of the catalytic reaction at different Pt surfaces: a CO-Pt-O complex is formed that equals the CO chemisorption energy at terraces and steps, leading to the abrupt desorption of poisoning CO from all crystal facets at the same temperature., We acknowledge financial support from the Spanish Ministry of Science and Innovation (Grants MAT-2017-88374-P, PID2019-107338RB-C63, PID2019-107338RB-C66), the Basque Government (Grants IT-1255-19, IT-1246-19), the Knut and Alice Wallenberg foundation (DNR KAW 2015.0058 „Atomistic Design of new Catalysts“) and the Swedish Research Council (DNR 349-2011-6491 „Catalysis on the atomic scale“).

One-atom-thick rare-earth/noble metal (RE-NM) compounds are attractive materials to investigate two-dimensional magnetism, since they are easy to synthesize into a common RE-NM2 structure with high crystal perfection. Here we perform a comparative study of the GdAu2, HoAu2, and YbAu2 monolayer compounds grown on Au(111). We find the same atomic lattice quality and moiré superlattice periodicity in the three cases, but different electronic properties and magnetism. The YbAu2 monolayer reveals the characteristic electronic signatures of a mixed-valence configuration in the Yb atom. In contrast, GdAu2 and HoAu2 show the trivalent character of the rare-earth and ferromagnetic transitions below 22 K. Yet, the GdAu2 monolayer has an in-plane magnetic easy-axis, versus the out-of-plane one in HoAu2. The electronic bands of the two trivalent compounds are very similar, while the divalent YbAu2 monolayer exhibits different band features. In the latter, a strong 4f–5d hybridization is manifested in neatly resolved avoided crossings near the Fermi level. First principles theory points to a residual presence of empty 4f states, explaining the fluctuating valence of Yb in the YbAu2 monolayer., This work was supported in part by the Spanish MINECO (MAT-2017-88374-P, MAT2016-78293-C6, FIS2016-75862-P, PGC2018-098613-B-C21, SEV-2017-0706 and SEV-2016-0686), the Spanish Research Agency (PID2019-107338RB-C65), Basque Government Project IT-1255-19, and University of the Basque Country (UPV/EHU) grant GIU18/138 and the European Regional Development Fund (ERDF) under the program Interreg V-A España-Francia-Andorra (Contract No. EFA 194/16 TNSI). The experiments at Elettra were supported by the EU Calipso project and computational resources were provided by the DIPC computing center. L. F. acknowledges financial support from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement MagicFACE No 797109. A. K. K., M. J., P. M. S. and P. M. acknowledge the project EUROFEL-ROADMAP ESFRI.

Vicinal surfaces are crystal planes oriented a few degrees off from a high symmetry direction. Such a small deviation (called miscut) from a high symmetry axis leads to a characteristic periodic roughness at the nanoscale, namely atom-height step arrays that separate atomically-flat terraces. The alternating series of “terraces” and “steps” makes electronic properties of vicinal surfaces very peculiar, distinct from those of atomically-flat surfaces. On the one hand, terraces and steps feature atoms with distinct coordination and complex and varied elastic relaxations, influencing their core-level energies. We show how core levels at a vicinal surface exhibit a miscut-dependent stress release, as well as fine structural relaxations, such as faceting. On the other hand, atomic steps create a periodic modulation of the crystal potential, affecting two-dimensional (2-D) surface states of metals. This leads to Bloch scattering of surface electrons by the step lattice, and eventually, to one-dimensional (1-D) quantization by confinement at terraces or step edges. We discuss the occurrence and observation of superlattice scattering and 1"​ D confinement at a vicinal surface, the importance of the atomic nature of the surface state wave function, the dependence on the lattice constant of the step array, and the rich scattering phenomenon that arises in faceted structures and spin-textured bands.

We study the effect of thermal oxygen exposure on a monolayer of h-BN grown on vicinal Ni surfaces by scanning tunneling microscopy, X-ray absorption, and photoemission spectroscopies. Using a curved Ni crystal, we carry out a systematic exploration of the h-BN monolayer interfacing a full variety of vicinal orientations around the (111) high-symmetry direction. We demonstrate the occurrence of two processes upon oxygen exposure: oxygen intercalation underneath the h-BN layer, which leads to decoupling of the h-BN from the substrate, and oxidation of h-BN itself, which proceeds via substitution of nitrogen atoms. Oxygen intercalation appears to be substrate orientation dependent, while oxidation of h-BN is rather uniform over the different vicinal planes. These findings will be of importance for future applications of BN-based devices and materials under ambient conditions., We are grateful to the Interdisciplinary Resource Center for Nanotechnology of the Research Park of Saint Petersburg State University for performing SEM measurements. A.A.M., C.L., and D.A.S. acknowledge DFG (Grant No. LA655-19/1) and BMBF (Grant No. 05K12OD2). L.F. and A.F. acknowledge financial support within the joint project of the Russian Science Foundation (Project 16-42-01093) and DFG (Grant LA655-17/1). K.A.B. and D.Yu.U. acknowledge Saint Petersburg State University for research Grant 11.65.42.2017 and RFBR (Grant 17-02-00427). We acknowledge financial support from the Spanish Ministry of Economy (Grants MAT-2016-78293-C6 and MAT-2017-88374-P) and Basque Government (Grant IT-1255-19). We acknowledge Helmholtz-Zentrum Berlin für Materialien und Energie for support within the bilateral Russian–German Laboratory program.

Understanding how specific atom sites on metal surfaces lower the energy barrier for chemical reactions is vital in catalysis. Studies on simplified model systems have shown that atoms arranged as steps on the surface play an important role in catalytic reactions, but a direct comparison of how the light-off temperature is affected by the atom orientation on the step has not yet been possible due to methodological constraints. Here we report in situ spatially resolved measurements of the CO production over a cylindrical-shaped Pd catalyst and show that the light-off temperature at different parts of the crystal depends on the step orientation of the two types of steps (named A and B). Our finding is supported by density functional theory calculations, revealing that the steps, in contrast to what has been previously reported in the literature, are not directly involved in the reaction onset but have the role of releasing stress., The authors thank the Knut and Alice Wallenberg Foundation, the Swedish Research Council, the Swedish Foundation for Strategic Research, and the Crafoord Foundation. Support by the MAX IV staff is gratefully acknowledged. The calculations were performed at C3SE through a SNIC grant. J.E.O. acknowledges support from the Spanish Ministry of Economy (MAT2013-46593-C6-4-P) and the Basque Government (IT621-13).

et al., Materials that exhibit ferromagnetism, interfacial stability, and tunability are highly desired for the realization of emerging magnetoelectronic phenomena in heterostructures. Here we present the GdAg monolayer alloy, which possesses all such qualities. By combining X-ray absorption, Kerr effect, and angle-resolved photoemission with ab initio calculations, we have investigated the ferromagnetic nature of this class of Gd-based alloys. The Curie temperature can increase from 19 K in GdAu to a remarkably high 85 K in GdAg. We find that the exchange coupling between Gd atoms is barely affected by their full coordination with noble metal atoms, and instead, magnetic coupling is effectively mediated by noble metal-Gd hybrid s,p-d bands. The direct comparison between isostructural GdAu and GdAg monolayers explains how the higher degree of surface confinement and electron occupation of such hybrid s,p-d bands promote the high Curie temperature in the latter. Finally, the chemical composition and structural robustness of the GdAg alloy has been demonstrated by interfacing them with organic semiconductors or magnetic nanodots. These results encourage systematic investigations of rare-earth/noble metal surface alloys and interfaces, in order to exploit them in magnetoelectronic applications., This work was supported by the Spanish Government (MAT2013-46593-C6-4-P, MAT2013-46593-C6-5-P, FIS2013-48286-C02-02-P, FIS2013-48286-C02-01-P), the Basque Government (IT621-13,IT627-13,IT756-13), the Diputación de Gipuzkoa (RF-0061/2015), and the Deutsche Forschungsgemeinschaft (SFB 1083 “Structure and Dynamics of Internal Interfaces”). A.Mu., M.A.V., and M.G. acknowledge the Severo Ochoa program SEV-2013-0295. B.X. and M.J.V. acknowledge two A.R.C. grants (TheMoTherm 10/15-03 and AIMED 15/19-09) from the Communauté Francaise de ̧ Belgique. Computer time was made available by PRACE-2IP and 3IP (EU FP7 Grant No. RI-283493 and RI-312763), CECI, SEGI-ULg, and the DIPC.

The structural and electronic properties of hexagonal boron nitride (hBN) grown on stepped Ni surfaces are systematically investigated using a cylindrical Ni crystal as a tunable substrate. Our experiments reveal homogeneous hBN monolayer coating of the entire Ni curved surface, which in turn undergoes an overall faceting. The faceted system is defined by step-free hBN/Ni(1 1 1) terraces alternating with strongly tilted hBN/Ni(1 1 5) or hBN/Ni(1 1 0) nanostripes, depending on whether we have A-type or B-type vicinal surfaces, respectively. Such deep substrate self-organization is explained by both the rigidity of the hBN lattice and the lack of registry with Ni crystal planes in the vicinity of the (1 1 1) surface. The analysis of the electronic properties by photoemission and absorption spectroscopies reveal a weaker hBN/Ni interaction in (1 1 0)- and (1 1 5)-oriented facets, as well as an upward shift of the valence band with respect to the band position at the hBN/Ni(1 1 1) terrace., We acknowledge financial support from the Deutsches Forschungsgemein chaft DFG (Grants LA655-17/1 and LA655-19/1), the Spanish Ministry of Economy (Grants MAT-2016-78293-C6, MAT-2017-88374-P), the Basque Government (Grant IT-1255-19), the Helmholtz-Zentrum Berlin für Materialien und Energie for support within the bilateral RussianGerman Laboratory program as well as from the joint project of the Russian Science Foundation (project 16-42-01093) and DFG (Grant No. LA655-17/1). DYuU acknowledges St. Petersburg State University for research Grant No. 11.65.42.2017 and Russian Foundation for Basic Research RFBR (Project No. 17-02-00427).

Understanding nanoparticle catalysis requires novel approaches in which adjoining crystal orientations can be studied under the same reactive conditions. Here we use a curved palladium crystal and near-ambient pressure X-ray photoemission spectroscopy to characterize chemical species during the catalytic oxidation of CO in a whole set of surfaces vicinal to the (111) direction simultaneously. By stabilizing the reaction at fixed temperatures around the ignition point, we observe a strong variation of the catalytic activity across the curved surface. Such spatial modulation of the reaction stage is straightforwardly mapped through the photoemission signal from active oxygen species and poisoning CO, which are shown to coexist in a transient regime that depends on the vicinal angle. Line-shape analysis and direct comparison with ultrahigh vacuum experiments help identifying and quantifying all such surface species, allowing us to reveal the presence of surface oxides during reaction ignition and cooling-off., We acknowledge financial support from the Spanish Ministry of Economy (Grants MAT-2012-38567-C02-02, MAT-2016-78293-C6, MAT-2017-88374-P) and Basque Government (Grant IT-1255-19).

We have investigated the electronic structures of axially oxo functionalized titanylphthalocyanine (TiOPc) on Ag(111) by X-ray and ultraviolet photoelectron spectroscopies, two-photon photoemission, X-ray absorption spectroscopy, and X-ray magnetic circular dichroism. Furthermore, we use complementary data of TiOPc on graphite and planar copper phthalocyanine (CuPc) on Ag(111) for a comparative analysis. Both molecules adsorb on Ag(111) in a parallel orientation to the surface, for TiOPc with an oxygen-up configuration. The interaction of nitrogen and carbon atoms with the substrate is similar for both molecules, while the bonding of the titanium atom to Ag(111) in the monolayer is found to be slightly more pronounced than in the CuPc case. Ultraviolet photoemission spectroscopy reveals an occupation of the lowest unoccupied molecular orbital (LUMO) level in monolayer thick TiOPc on Ag(111) related to the interaction of the molecules and the silver substrate. This molecule-metal interaction also causes an upward shift of the Ag(111) Shockley state that is transformed into an unoccupied interface state with energies of 0.23 and 0.33 eV for the TiOPc monolayer and bilayer, respectively, at the Brillouin zone center., The authors acknowledge financial support from the Deutsche Forschungsgemeinschaft through SFB 1083 “Structure and Dynamics of Internal Interfaces”, the Spanish CSIC I-Link programm, the Spanish Ministry of Economy and Competitiveness, MINECO (under Contract No. MAT2016-78293-C6-2-R, and Severo Ochoa No. SEV-2013-0295.), and by the Secretariat for Universities and Research, Knowledge Department of the Generalitat de Catalunya (2014 SGR 715). M. Paradinas thanks the Spanish Government for financial support through PTA2014-09788-I fellowships. ICN2 is funded by the CERCA Programme/Generalitat de Catalunya.

A trigon structure formed by submonolayer gadolinium deposition onto Au(111) is revealed as a robust growth template for cobalt nanodot arrays by Frederik Schiller and co‐workers in article 1600187. The cobalt nanoislands behave as independent magnetic entities with an out‐of‐plane easy axis of anisotropy and enhanced magnetic anisotropy values, as compared to other self‐organized cobalt nanodot superlattices.

A trigon structure formed by submonolayer gadolinium deposition onto Au(111) is revealed as a robust growth template for Co nanodot arrays. Scanning Tunneling Microscopy and X‐Ray Magnetic Circular Dichroism measurements evidence that the Co nanoislands behave as independent magnetic entities with an out‐of‐plane easy axis of anisotropy and enhanced magnetic anisotropy values, as compared to other self‐organized Co nanodot superlattices. The large strain induced by the lattice mismatch at the interface between Co and trigons is discussed as the main reason for the increased magnetic anisotropy of the nanoislands.

et al., A vicinal rutile TiO(110) crystal with a smooth variation of atomic steps parallel to the [1-10] direction was analyzed locally with STM and ARPES. The step edge morphology changes across the samples, from [1-11] zigzag faceting to straight [1-10] steps. A step-bunching phase is attributed to an optimal (110) terrace width, where all bridge-bonded O atom vacancies (O vacs) vanish. The [1-10] steps terminate with a pair of 2-fold coordinated O atoms, which give rise to bright, triangular protrusions (S) in STM. The intensity of the Ti 3d-derived gap state correlates with the sum of O vacs plus S protrusions at steps, suggesting that both O vacs and steps contribute a similar effective charge to sample doping. The binding energy of the gap state shifts when going from the flat (110) surface toward densely stepped planes, pointing to differences in the Ti polaron near steps and at terraces., We acknowledge financial support from the Spanish Ministry of Economy (Grants MAT2013-46593-C6-4-P and MAT2013-46593-C6-2-P) and the Basque Government (Grant IT621-13 and IT756-13). M.S. and U.D. acknowledge support from the ERC Advanced Grant “OxideSurfaces”. D.S.P. and M.M. acknowledge support from the Marie Curie ITN “THINFACE” and financial support by the Deutsche Forschungsgemeinschaft. through SFB 1083 “Structure and Dynamics of Internal Interfaces”.

This work is licensed under a Creative Commons Attribution 4.0 International License.-- et al., Surface chemistry and catalysis studies could significantly gain from the systematic variation of surface active sites, tested under the very same conditions. Curved crystals are excellent platforms to perform such systematics, which may in turn allow to better resolve fundamental properties and reveal new phenomena. This is demonstrated here for the carbon monoxide/platinum system. We curve a platinum crystal around the high-symmetry (111) direction and carry out photoemission scans on top. This renders the spatial core-level imaging of carbon monoxide adsorbed on a 'tunable' vicinal surface, allowing a straightforward visualization of the rich chemisorption phenomenology at steps and terraces. Through such photoemission images we probe a characteristic elastic strain variation at stepped surfaces, and unveil subtle stress-release effects on clean and covered vicinal surfaces. These results offer the prospect of applying the curved surface approach to rationally investigate the chemical activity of surfaces under real pressure conditions., We acknowledge financial support from the Spanish Ministry of Economy (Grants MAT2013-46593-C6-4-P and MAT2013-46593-C6-2-P ), Basque Government (Grants IT621-13 and IT756-13). A.L.W. acknowledges support from the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-SC0012704. AXBR acknowledges support from the Basque Departamento de Educación and the UPV/EHU through the Zabalduz program. AXBR, PCS and DSP acknowledge the Deutsche Forschungsgemeinschaft through the Sonderforschungsbereich 1083.

We present a comprehensive study of the magnetism and morphology of an ultrahigh density array of Co nanoclusters self-assembled on the single atomic layer GdAu2 on Au(111) template surface. Combining scanning tunneling microscopy, x-ray magnetic circular dichroism, and magneto-optical Kerr effect measurements, we reveal a significant enhancement of the perpendicular magnetic anisotropy energy for noncoalesced single atomic layer nanoclusters compared to Co/Au(111). For coverages well beyond the onset of coalescence, we observe room-temperature in-plane magnetic remanence.

Results of an angle-resolved photoemission study of the 0.5 monolayer c (2 × 2) manganese superstructure on fcc-(001) surfaces of Fe, Co, Ni, and Cu are presented. In order to stabilize an fcc structure of Fe and Co, thin films of these ferromagnetic metals were grown pseudomorphically on Cu(001). For comparison, linear muffin-tin orbital band structure calculations were carried out to identify the contributions of the atoms of the surface compound to the density of states. For Mn on Cu(001) and Ni(001) the position of the manganese 3d majority spin band at the -point of the second surface Brillouin zone is found at 3.0 eV, while for Mn on Fe/Cu(001), Co/Cu(001), and Ni/Cu(001) the band position is shifted to 3.5 eV binding energy. The identical binding energy position on all ferromagnetic thin films substrates is attributed to the negligible hybridization of the Mn 3d majority spin band while on Cu(001) Mn bands can hybridize with copper derived states, resulting in a slightly different energy position. Furthermore, a decrease of the lattice constant results in a decrease in binding energy consistent with the picture of local magnetic Mn 3d moments.

Controlling anisotropy and exchange coupling in patterned magnetic nanostructures is the key for developing advanced magnetic storage and spintronic devices. We report on the antiferromagnetic interaction between a Co nanodot array and its supporting GdAu2 nanotemplate that induces large anisotropy values in individual Co nanodots. In clear contrast with nonmagnetic Au substrates, GdAu2 triggers an earlier switch from out-of-plane anisotropy in monatomic high dots to in-plane when the dot height becomes biatomic. © 2014 American Chemical Society., The authors acknowledge financial support from the Gipuzkoako Foru Aldundia (L.F. and M.B.-R.), the European Commission through Project No. FP7-PEOPLE-2010- RG276921 (M.B.-R.), the European Social Fund within the program JAE-Doc, the Spanish MINECO (MAT2013-46593-C6-4-P, FIS 2010-19609-C02-02), the Basque Government (IT-621-13, IT-627-13, IT366-07), SAIOTEK (SPEI2UN095), and ETORTEK (NANOIKER No. IE11-304). The MBE chamber on DEIMOS was funded by the Agence National de la Recherche, Grant ANR-05-NANO-073.

Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence., Quantum well states of Ag films grown on stepped Au(111) surfaces are shown to undergo lateral scattering, in analogy with surface states of vicinal Ag(111). Applying angle resolved photoemission spectroscopy we observe quantum well bands with zone-folding and gap openings driven by surface/interface step lattice scattering. Experiments performed on a curved Au(111) substrate allow us to determine a subtle terrace-size effect, i.e., a fine step-density-dependent upward shift of quantum well bands. This energy shift is explained as mainly due to the periodically stepped crystal potential offset at the interface side of the film. Finally, the surface state of the stepped Ag film is analyzed with both photoemission and scanning tunneling microscopy. We observe that the stepped film interface also affects the surface state energy, which exhibits a larger terrace-size effect compared to surface states of bulk vicinal Ag(111)crystals., This work was supported in part by the Spanish Ministry of Economy (MINECO) through grants MAT2013–46593-C6–2-P, MAT2013–46593-C6–4-P, MAT2013–46593-C6–5-P, and FIS2010–19609-C02–02, by the German Sonderforschungsbereich SFB 1083, and by the Basque Government through Projects IT-621–13 and IT-756–13. ICN2 acknowledges support from the Severo Orchoa Program (MINECO, Grant SEV-2013-0295).

Angle-resolved photoemission studies of c(2×2)MnCu/Cu(0 0 1) and pgg(4×2)Mn/Cu(0 0 1) prepared by in situ deposition of Mn on Cu(0 0 1) are reported. For the c(2×2) superstructure, the Mn 3d-derived band is found at 3.0 eV binding energy at the Γ c (2×2) of the second surface Brillouin zone. An identical energy position is observed for the pgg(4×2) structure indicating the presence of the same high-spin ground state as in the c(2×2).

We have studied the growth of copper on the c(2×2)MnCu/Cu(001) ordered surface phase by using X-ray photoelectron diffraction (XPED) in the forward-scattering regime and low-energy electron diffraction (LEED). The magnetic behaviour of the grown multilayer system was monitored by soft X-ray absorption (SXA) of the Mn L 2,3 edge. The local environment of manganese atoms seems quite similar to that of fcc copper, and epitaxial copper layers could be grown on the c(2×2)MnCu/Cu(001) surface alloy. The copper overlayers do not modify the magnetism of the underlying magnetic surface alloy, which remains in a high-spin ground state as measured by X-ray absorption of the Mn L 2,3 doublet.

We report on the crystal structure and electronic bands of LaAu${}_{2}$ and CeAu${}_{2}$ surface intermetallic compounds grown by high-temperature deposition on Au(111). By scanning-tunneling microscopy we study the formation of different alloy phases as a function of growth temperature and lanthanide coverage. We determine the specific growth conditions to achieve monolayers and bilayers of LaAu${}_{2}$ and CeAu${}_{2}$ with high crystalline quality. Due to lattice mismatch with the underlying Au substrate, both LaAu${}_{2}$ and CeAu${}_{2}$ exhibit long-range moir\'e patterns, which can serve as templates for further nanostructure growth. By angle-resolved photoemission we map the two-dimensional band structure of these surface alloys, discussing the nature of the different spectral features in the light of first-principles calculations.

We investigate the scattering of electrons belonging to Shockley states of (111)-oriented noble metal surfaces using angle-resolved photoemission (ARPES) and scanning tunneling microscopy (STM). Both ARPES and STM indicate that monatomic steps on a noble metal surface may act either as strongly repulsive or highly transmissive barriers for surface electrons, depending on the coherence of the step lattice, and irrespectively of the average step spacing. By measuring curved crystal surfaces with terrace length ranging from 30 to 180 Å, we show that vicinal surfaces of Au and Ag with periodic step arrays exhibit a remarkable wave function coherence beyond 100 Å step spacings, well beyond the Fermi wavelength limit and independently of the projection of the bulk band gap on the vicinal plane. In contrast, the analysis of transmission resonances investigated by STM shows that a pair of isolated parallel steps defining a 58 Å wide terrace confines and decouples the surface state of the small terrace from that of the (111) surface. We conclude that the formation of laterally confined quantum well states in vicinal surfaces as opposed to propagating superlattice states depends on the loss of coherence driven by imperfection in the superlattice order. © 2013 American Physical Society., This work was supported in part by the Spanish MICINN (MAT2007-63083 and MAT2010-15659), the Basque Government (IT-257-07), and the Agència de Gestió d’Ajuts Universitaris i de Recerca (2009 SGR 695). The SRC is funded by the National Science Foundation (Award No. DMR-0084402). A.M. and J.L.-C. acknowledge funding from the Ramon y Cajal Fellowship program.

The deposition of submonolayer amounts of Au onto Cu(111) results in a Au-Cu surface alloy with temperature- and thickness-dependent stoichiometry. Upon alloying, the characteristic Shockley state of Cu(111) is modified, shifting to 0.53 eV binding energy for a particular surface Au2Cu concentration, which is a very high binding energy for a noble-metal surface. Based on a phase accumulation model analysis, we discuss how this unusually large shift is likely reflecting an effective increase in the topmost layer thickness of the order of, but smaller than, the value expected from the moiré undulation. © 2012 American Physical Society., This work was supported in part by the Spanish MINECO (Grants No. MAT2010-21156-C03-01 and No. MAT2010-21156-C03-03), and the Basque Government (Grant No. IT-257-07). The SRC is funded by the National Science Foundation (Award No. DMR-0084402).

The two-dimensional, free-electron-like band structure of noble metal surfaces can be radically transformed by appropriate nanostructuration. A case example is the triangular dislocation network that characterizes the epitaxial $\mathrm{Ag}/\mathrm{Cu}(111)$ system, which exhibits a highly featured band topology with a full band gap above ${E}_{F}$ and a hole-pocket-like Fermi surface. Here we show that controlled doping of the $\mathrm{Ag}/\mathrm{Cu}(111)$ interface with Au allows one to observe a complete Lifshitz transition at 300 K; i.e., the hole pockets fill up, the band gap entirely shifts across ${E}_{F}$, and the Fermi surface becomes electron-pocket-like.

9 páginas, 3 figuras.-- et al., The inhibition in wave propagation at band gap energies plays a central role in many areas of technology such as electronics (electron gaps), nanophotonics (light gaps) and phononics (acoustic gaps), among others. Here we demonstrate that metal surfaces featuring free-electron-like bands may become semiconducting by periodic nanostructuration. We combine scanning tunneling spectroscopy and angle-resolved photoemisssion to accurately determine the energy-dependent local density of states and band structure of the Ag/Cu(111) noble metal interface patterned with an array of triangular dislocations, demonstrating the existence of a 25 meV band gap that extends over the entire surface Brillouin zone. We prove that this gap is a general consequence of symmetry reduction in close-packed metallic overlayers; in particular, we show that the gap opening is due to the symmetry lowering of the wave vector group at the K point from C3v to C3., This work was supported in part by the Spanish MICINN (MAT2007-66050, MAT2007-63083 and Consolider NanoLight.es), the EU (NMP4-SL-2008-213669-ENSEMBLE), the Basque Government (IT-257-07) and the Centre National de la Recherche Scientifique (CNRS).

Atomic staircases in noble-metal surfaces are model one-dimensional superlattices, where free-electron-like surface states transform into superlattice bands with sizable quantum size shifts and gaps. At critical step spacings d=n×(λF/2), such superlattice gaps lie at the Fermi energy, affecting the electronic energy and hence the structural stability of the step lattice, which is held by weak elastic interactions. We use Cu, Ag, and Au curved crystals to smoothly tune the superlattice constant d in angle-resolved photoemission (ARPES) and scanning tunneling microscopy (STM) experiments. With ARPES we accurately quantify terrace-size effects and determine the superlattice potential, which increases from Ag to Cu and to Au. With STM we analyze the d-dependent terrace width distribution for Cu and Ag, and observe nonlinear variations in Cu. On the grounds of simple electronic and elastic models, we conclude that terrace width distribution instabilities and electronic energy variations at d=n×(λF/2) have the same order of magnitude for Cu. In contrast, the weak superlattice potential in Ag, i.e., its smoother band-structure modulation, is not sufficient to alter the step lattice., This work was supported in part by the Spanish MICINN (MAT2007-63083), and the Basque Government (IT-257-07). The SRC is funded by the National Science Foundation (Grant No. DMR-0084402).

4 páginas, 4 figuras.-- PACS numbers: 68.55.-a, 68.35.-p, 73.61.At, 81.05.Bx.-- et al., Surface alloying is a powerful way of varying physical and chemical properties of metals, for a number of applications from catalysis to nuclear and green technologies. Surfaces offer many degrees of freedom, giving rise to new phases that do not have a bulk counterpart. However, the atomic characterization of distinct surface compounds is a major task, which demands powerful experimental and theoretical tools. Here we illustrate the process for the case of a GdAu2 surface phase of extraordinary crystallinity. The combined use of surface-sensitive techniques and state-of-the-art ab initio calculations disentangles its atomic and electronic properties. In particular, the stacking of the surface layers allows for gadolinium’s natural ferromagnetic state, at variance with the bulk phase, where frustration leads to antiferromagnetic interlayer coupling., We acknowledge support from the Belgian FNRS, EU FP7 project ‘‘THEMA’’ (G.A. 228539), ACI-Promociona (ACI2009-1036), iNanogune ETORTEK, and the EU FP7 ‘‘ETSF I3’’ project (G.A. 211956). This work was supported in part by the Spanish MICINN (FIS2007-65702-C02-01 and MAT2007-63083) and the Basque Government (IT-257-07 and T-319-07). The SRC is supported by the NSF under Grant No. DMR-0537588.

3 páginas, 4 figuras., We report the self-organized growth of cobalt nanodot arrays using a Gd-Au Moiré superlattice as a template. After analyzing the influence of the Co flux and the substrate temperature, we obtain the suitable parameters to maximize nanodot density, homogeneity, and individual size. Depending on the growth conditions an areal density of up to 54 Teradots/inch2 can be achieved. Below the limit of lateral coalescence, independent nanodots made of ∼ 1000 Co atoms exhibit room temperature remanent magnetization., This work was financed by the Basque Government (Nanotron, Grant No. IT-257-07), the Spanish MCyI (Grant No. MAT2007-63083), and the Acciones Integradas program.

9 paginas, 8 figuras, A new class of nanostructured templates is obtained by submitting Au(111) films to high-temperature vapor deposition of Gd in ultrahigh vacuum. In a low coverage regime, Gd atoms are embedded in the topmost Au layer, inducing a structural transformation of the herringbone reconstruction to create a network of trigons. At higher dose, the reactive deposition of Gd leads to the formation of an atomically perfect GdAu2 surface compound characterized by a long-range periodic Moiré pattern. Both the trigon and Moiré lattices are highly ordered nanostructures, which turned out to be robust templates to grow metal nanodots. As a test example, Co was deposited at room temperature, forming uniform dots that faithfully arrange by following the underlying trigons or Moiré periodicity. For the latter, one can achieve nanodot arrays that exhibit record areal density., This work was financed by the Basque Government (Nanotron, IT-257-07), the Spanish Ministry of Science and Innovation (MAT2007-63083). The Synchrotron Radiation Center is funded by the National Science Foundation (Award No. DMR-0084402).

Vicinal Au(111) surfaces exhibit periodic faceting within a wide range of miscut angles. There, the system segregates two alternating phases with different step lattice constants dw and dn. Using a curved crystal surface that allows a smooth variation of the surface orientation, we have studied, as a function of the miscut angle, the evolution of Au(111) faceted structures by scanning tunneling microscopy, and their electronic surface states by angle-resolved photoemission. We observe that surface bands reflect the two-phase character of the faceted system, i.e. we find dw- and dn-like states that evolve accordingly to the faceted structure. Using a photoemission calculation we prove that the apparently complex topology hides relatively simple physics, i.e. the same free-electron-like dispersion and repulsive step scattering that feature surface bands in stepped noble metal surfaces. On the grounds of such simulations, we discuss the possible interference of the electronic energy in the delicate free energy balance that determines the critical size of reconstructed (dw) and unreconstructed (dn) terraces during Au faceting., The work is supported through projects of the Basque Government (IT257-07) and the Spanish Ministerio de Educacion y Ciencia (MAT2007-63083). The SRC is funded by the National Science Foundation (award no. DMR-0084402).

The interface reflectivity in the Mg/W(110) metallic quantum well is determined from line-shape analysis of high-resolution photoemission spectra. Moreover, a quick reflectivity drop is found away from projected band gaps of the appropriate symmetry near EF, such that the interface reflectivity overcomes the bulklike quasiparticle lifetime as the dominant line broadening mechanism at the Fermi energy. A nearly-free-electron model calculation for the W(110) substrate band structure demonstrates that coherent wave-function scattering is the relevant mechanism that determines the interface reflectivity in the resonator., The work was supported through projects of the University of the Basque Country -Grant No. GIU06/27 and the Spanish Ministerio de Educacion y Ciencia -Grant No. MAT2007-63083

The potassium monolayer on Cu(111) defines the simplest metallic quantum well that confines a single $s$-like discrete level. The analysis of the metallization onset in such a K adlayer reveals, however, a subtle electronic structure. The metallic monolayer condensate is actually characterized by a pair of two-dimensional states that lie below the Fermi energy, namely, a quantum well state and a resonant band reminiscent of the Cu(111) surface state. All quantum well states, resonances, and Cu substrate bulk bands exhibit smooth K coverage dependence, suggesting that changes in the crystal potential upon K adsorption extend from the surface and/or interface inside the Cu substrate.

2 páginas, 1 figura.-- et al., Schiessling and Brühwiler question the validity of the results by Schiller et al. and suggested that the throughput correction and the Fermi level placement are erroneous. Below, we rule out both scenarios.