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The bottom-up synthesis of carbon based nanomaterials directly on semiconductor surfaces allows to decouple their electronic and magnetic properties from the substrates. However, the lack of reactivity on these non-metallic surfaces hinders or reduces significantly the yield of these reactions. Such hurdles practically precludes transferring bottom-up synthesis strategies onto semiconducting and insulating surfaces. Here, we achieve a high polymerization yield of terphenyl molecules on the semiconductor TiO$_2$(110) surface by incorporating cobalt atoms as catalysts in the Ullmann coupling reaction. Cobalt atoms trigger the debromination of 4,4-dibromo-p-terphenyl (DBTP) molecules on TiO$_2$(110) and the formation of an intermediate organometallic phase already at room-temperature (RT). As the debromination temperature is drastically reduced, the homo-coupling temperature is also significantly lowered, preventing the desorption of DBTP molecules from the TiO$_2$(110) surface and leading to a radical improvement on the poly-para-phenylene (PPP) polymerization yield. The universality of this mechanism is demonstrated with an iodinated terphenyl derivative (DITP), which shows analogous dehalogenation and polymerization temperatures with a very similar reaction yield. Consequently, we propose to use minute amounts of metal catalyst to drive forward generic bottom-up synthesis strategies on non-metallic surfaces.

Ferromagnetism (FM) is the cornerstone of permanent magnets, data storage and other technologies that directly impact our everyday life by their implementation in standard applications and devices. When downscaling bulk materials into their two-dimensional (2D) magnetic isotropic form, the Mermin-Wagner theorem precludes this collective state mediated by short-range exchange interactions at finite temperatures. Interestingly, this prediction fails when significant magnetic anisotropy is present in the material, as recently demonstrated in single layered van der Waals crystals. Before the latter, single layer metal-organic frameworks (MOFs) grown on metallic supports were one of the earliest candidates for achieving 2D-FM. Such high expectations were based on the chemical and spacing control of the 2D-MOF magnetic centers, the tunability of the organic linkers and the rich self-assembled architectures displayed. However, despite many attempts, extended FM in 2D-MOFs has been experimentally elusive. In this work, we demonstrate that extended, cooperative FM takes place in an atom thick 2D-MOF consisting of 9,10-dicyanoanthracene (DCA) molecules and Fe adatoms grown on Au(111). We show this by means of an experimental multitechnique approach that is endorsed by state-of-the art first-principles calculations. Particularly, this 2D ferromagnet follows a first order transition with TC ~ 35 K, which is driven by exchange interactions mainly through the molecular linkers (J=2 meV) and exhibits an out-of-plane square-like hysteresis loop. The strict periodicity of our 2D-MOF allows us to envision the fabrication of ultra-dense single atom magnetic memories and opens the way to explore periodic magnetic 2D-models that could considerably increase the fundamental superparamagnetic limit., Comment: Main text 18 pages containing 3 figures. Supplementary material 18 pages containing 8 figures

Trabajo presentado al Encuentro de la Red Temática FunMolSys: "Ciencia Molecular sobre superficies: Síntesis y Funcionalidad, celebrado en la Universidad de Granada entre los días 1 y 3 de junio 2022., Financiado por la Agencia Estatal de Investigación bajo referencia RED2018-102833-T.

Trabajo presentado al International Workshop on Spintronics, celebrado en San Carlos de Bariloche, Río Negro (Argentina) del 6 al 11 de noviembre de 2022., Topological insulators are a recently discovered class of materials exhibiting interesting properties for applications such as quantum computation devices. Recently, metal-organic frameworks (MOF) have been theoretically proposed as the organic counterpart of topological insulators. Despite the experimental achievement of several of the proposed MOFs, their edge state visualization, which is the fingerprint of 2D topological insulator, remains elusive. We have formed these proposed MOFs with expected topological insulator character using 9,10-dicyanoanthracene molecules and Cu, Fe and Co adatoms on a the three (111) noble metal substrates. The lattices generally extend throughout the surface as single-domain and exhibit an almost perfect order. By means of scanning tunneling spectroscopy and angle-resolved photoemission spectroscopy we studied their electronic structure, and commonly find total absence of an edge state despite the excellent network order. Functionalized tip measurements and tight-binding calculations suggest that structural asymmetries drive the networks into a topologically trivial case that destroys its edge state. However, we observe an edge state emerging when the SOC of the coordination atom is significantly increased. Thus, we present the first experimental evidence compatible with the Organic Topological Insulator prediction., PID2019-107338RB-C64, RED2018-102833-T, financiado porMCIN/AEI /10.13039/501100011033 Regional Government of Aragon (E12-20R). European Research Council under European Union’s Horizon 2020 research and innovation programme of Marie Skłodowska-Curie grant agreementULTIMATE-I Nº 101007825 Access to STM instruments: LMA-University of Zaragoza

Resumen del trabajo presentado al Joint European Magnetic Symposia (JEMS), celebrado en Warsaw (Poland) del 24 al 29 de julio de 2022.

Este trabajo trata de la preparación de polímeros metal-orgánicos y covalentes en forma de anillos y de cadenas zigzag mediante el método de síntesis en superficie (on-surface synthesis,OSS). Dicho método es una aproximación de crecimiento de abajo-arriba (bottom-up approach) para sintetizar nanoestructuras a partir de precursores moleculares simples. Estudiamos el papel de la temperatura y del sustrato sobre los productos obtenidos por síntesis en condiciones de ultra-alto-vacío (UHV). Las estructuras obtenidas se caracterizan mediante un Microscopio de Efecto Túnel (STM) a 4K sobre Ag y Au terminados en el plano (111). Se concluye que la sínteis funciona en ambos sustratos, aunque las estructuras que se forman y la temperatura a la que lo hacen dependen de éste. Así mismo se encuentran intermedios metal-orgánicos en el sustrato de Ag(111).

Resumen del trabajo presentado al International Workshop On-Surface Synthesis (OSS), celebrado en Sant Feliu de Guixols (Spain), del 25 al 30 de septiembre de 2022.

Funding Information: We acknowledge financial support from the Spanish Agencia Estatal de Investigación (AEI) and the European Regional Development Fund (FEDER) (Grants Nos. PID2019-107338RB-C63 and PID2019-107338RB-C64) and the Academy of Finland (project numbers 311012 and 314882). We acknowledge the Paul Scherrer Institut, Villingen, Switzerland, for provision of synchrotron radiation beamtime at PEARL Beamline of the SLS and would like to thank N. P. M. Bachellier and M. Muntwiller for assistance. We thank R. Fasel and R. Widmer for provision of substrate and a sample holder for the synchrotron experiments. The authors thank the generous allocation of computer time at the computing center of DIPC. Publisher Copyright: © 2021 American Chemical Society. The advent of on-surface chemistry under vacuum has vastly increased our capabilities to synthesize carbon nanomaterials with atomic precision. Among the types of target structures that have been synthesized by these means, graphene nanoribbons (GNRs) have probably attracted the most attention. In this context, the vast majority of GNRs have been synthesized from the same chemical reaction: Ullmann coupling followed by cyclodehydrogenation. Here, we provide a detailed study of the growth process of five-atom-wide armchair GNRs starting from dibromoperylene. Combining scanning probe microscopy with temperature-dependent XPS measurements and theoretical calculations, we show that the GNR growth departs from the conventional reaction scenario. Instead, precursor molecules couple by means of a concerted mechanism whereby two covalent bonds are formed simultaneously, along with a concomitant dehydrogenation. Indeed, this alternative reaction path is responsible for the straight GNR growth in spite of the initial mixture of reactant isomers with irregular metal-organic intermediates that we find. The provided insight will not only help understanding the reaction mechanisms of other reactants but also serve as a guide for the design of other precursor molecules.

Surfaces are at the frontier of every known solid. They provide versatile supports for functional nanostructures and mediate essential physicochemical processes. Being intimately related with 2D materials, interfaces and atomically thin films often feature distinct electronic states with respect to the bulk, which are key for many relevant properties, such as catalytic activity, interfacial charge-transfer, or crystal growth mechanisms. Of particular interest is reducing the surface electrons' dimensionality and spread with atomic precision, to induce novel quantum properties via lateral scattering and confinement. Both atomic manipulation and supramolecular principles provide access to custom-designed molecular superlattices, which tailor the surface electronic landscape and influence fundamental chemical and physical properties at the nanoscale. Herein, we review the confinement of surface state electrons focusing on their interaction with molecule-based scaffolds created by molecular manipulation and self-assembly protocols under ultrahigh vacuum conditions. Starting from the quasi-free 2D electron gas present at the (111)-terminated surface planes of noble metals, we illustrate the enhanced molecule-based structural complexity and versatility compared to simple atoms. We survey low-dimensional confining structures in the form of artificial lattices, molecular nanogratings or quantum dot arrays, which are constructed upon appropriate choice of their building constituents. Whenever the realized (metal-)organic networks exhibit long-range order, modified surface band structures with characteristic features emerge, revealing intriguing physical properties, such as discretization, quantum coupling or energy and effective mass renormalization. Such collective electronic states can be additionally modified by positioning guest species at the voids of open nanoarchitectures [...]., Comment: Review with 31 pages and 28 Figures

El invento del microscopio de efecto túnel y el desarrollo de protocolos supramoleculares en superficies han promovido la investigación en el campo de sistemas bidimensionales. Ambos son esenciales para descubrir y estudiar nanoestructuras orgánicas que sean nanodispositivos flexibles debido a sus morfologías modificables. Entre ellos, los ensamblajes metal-orgánicos destacan porque pueden generar enlaces fuertes y reversibles. Estas fuerzas de intensidad intermedias permiten el crecimiento de estructuras ordenadas a largo alcance casi sin defectos. Además, la elección de los componentes y del sustrato puede guiar el crecimiento de redes en geometrías con distintas funcionalidades.Existen estudios teóricos que dicen que las redes metal-orgánicas que contienen subredes de kagome y panal de abeja son aislantes topológicos orgánicos. Esto implica alojar estados de borde topológicamente protegidos, sin embargo, dichos estados nunca han sido observados experimentalmente. Aquí, se presentan 8 redes distintas que consisten en subredes mixtas de kagome y panal de abeja con morfología idéntica variando sus átomos de coordinación y el sustrato que lo soporta. En los capítulos 3 y 4 se presenta un estudio detallado de sus propiedades electrónicas. Se presenta la primera demostración experimental de una banda electrónica en una red metal-orgánica bidimensional, la cual está condicionada por el sustrato que la soporta. En ningún caso aparecieron los estados de borde, ni siquiera en las redes que tienen una interacción mínima con el sustrato. Atribuimos esta ausencia de estados de borde a pequeñas distorsiones estructurales que rompen las simetrías de espejo e inversión.Cuando las redes bidimensionales incorporan átomos de coordinación magnéticos aparecen fenómenos interesantes debido a la baja coordinación del metal y sus estados electrónicos colectivos. En el capítulo 5, el magnetismo de las redes se estudia a través de técnicas de rayos X en instalaciones de sincrotrón. Una de ellas, Fe+DCA/Au(111), es la primera red bidimensional metal-orgánica ferromagnética y que se comporta como el modelo de Ising.Finalmente, en el capítulo 6 se prueba la capacidad de estas redes como plantilla para el crecimiento nanoestructurado de metales 3d y 4f. La periodicidad y tamaño de estas estructuras se puede controlar en cierta manera por una adecuada elección de los métodos de preparación.

Trabajo presentado en 20th Trends in Nanotechnology International Conference (2019), celebrada en San Sebastián (España), del 30 de septiembre al 4 de octubre de 2019, In the early 1900’s Fritz Ullmann first reported the synthesis of biaryls from aryl halides mediated by a fine copper powder1 , demonstrating with this the aromatic nucleophilic substitution mediated by copper, now known as Ullmann condensation reaction. More than hundred years after, this reaction is routinely used in numerous industrial applications and, nowadays it becomes widely used for the synthesis on metal surfaces of atomically precise graphene nanoribbons2 The next step to move toward device applications requires performing the synthesis directly on suitable substrates such as semiconducting, insulating or magnetic substrates. Whit in this context, in the present work we explore the Ullmann based synthesis of polymers on magnetic and insulating substrates. In particular we demonstrate the aryl homocoupling synthesis of 4,4-Dibromo (or diiodo)-p-terphenyl precursor into molecular poly-p-phenylene wires on the semiconductor TiO2 surface3 and on the bimetallic (and ferromagnetic) GdAu2 surface alloy4 . Moreover, we propose a reaction pathway during the polymerization. To monitor the chemical reaction complementary microscopic and spectroscopic surface science techniques (, scanning tunneling microscopy, X-ray photoemission spectroscopy, angle-resolved Photoemission spectroscopy) are used.

Trabajo presentado en el X Iberian Conference on Tribology y XI Iberian Vacuum Conference (IBERTRIVA) celebrada en Sevilla (España), del 26 al 28 de junio de 2019, In the early 1900’s Fritz Ullmann first reported the synthesis of biaryls from aryl halides mediated by a fine copper powder , demonstrating with this the aromatic nucleophilic substitution mediated by copper, now known as Ullmann condensation reaction. More than hundred years after, this reaction is routinely used in numerous industrial applications and, nowadays it becomes widely used for the synthesis on metal surfaces of atomically precise graphene nanoribbons The next step to move toward device applications requires performing the synthesis directly on suitable substrates such as semiconducting, insulating or magnetic substrates. Whit in this context, in the present work we explore the Ullmann based synthesis of polymers on magnetic and insulating substrates. In particular we demonstrate the aryl homocoupling synthesis of 4,4- Dibromo (or diiodo)-p-terphenyl precursor into molecular poly-p-phenylene wires on the semiconductor TiO2 surface3 and on the bimetallic (and ferromagnetic) GdAu2 surface alloy4 . Moreover, we propose a reaction pathway during the polymerization. To monitor the chemical reaction complementary microscopic and spectroscopic surface science techniques (, scanning tunneling microscopy, X-ray photoemission spectroscopy, angle-resolved Photoemission spectroscopy) are used.

Conventional spin-degenerated surface electrons have been effectively manipulated by using organic and inorganic self-assembled nanoarrays as resonators. Step superlattices naturally assembled in vicinal surfaces are a particularly interesting case since they represent simple one-dimensional (1D) models for fundamental studies, and can imprint strong anisotropies in surface electron transport in real devices. Here we present the first realization of periodic resonator arrays on the BiAg2 atom-thick surface alloy with unprecedented atomic precision, and demonstrate their potential ability for tuning helical Rashba states. By employing curved crystals to select local vicinal planes we achieve tunable arrays of monoatomic steps with different morphology and orientation. Scanning the ultraviolet light beam on the curved surface during angle-resolved photoemission experiments allows one to unveil the scattering behavior of spin-textured helical states. In this way, we find coherent scattering of helical Rashba states from the step arrays, as well as step-density-dependent Rashba band shifts and spin-orbit splitting compared to the extended BiAg2 plane., 13 pages, 4 figures, 4 supplementary figures

Trabajo presentado al IX AUSE Congress and IV ALBA User's Meeting, celebrados en Barcelona (España) del 8 al 11 de octubre de 2019., MINECO MAT2016-78293-C6; EFA 194/16 (TNSI, (FEDER, EU).

Resumen del trabajo presentado a la 64th Annual Conference on Magnetism and Magnetic Materials (MMM), celebrada en Las Vegas (USA) del 4 al 8 de noviembre de 2019.

Quantum dot arrays in the form of molecular nanoporous networks are renown for modifying the electronic surface properties through quantum confinement. Here we show that, compared to the pristine surface state, the fundamental energy of the confined states can exhibit downward shifts accompanied by a lowering of the effective masses simultaneous to the appearance of tiny gaps at the Brillouin zone boundaries. We observed these effects by angle resolved photoemission for two self-assembled homothetic (scalable) Co-coordinated metal-organic networks. Complementary scanning tunneling spectroscopy measurements confirmed these findings. Electron plane wave expansion simulations and density functional theory calculations provide insight into the nature of this phenomenon, which we assign to metal-organic overlayer-substrate interactions in the form of adatom-substrate hybridization. The absence to date of the experimental band structure resulting from single adatom metal-coordinated nanoporous networks has precluded the observation of the significant surface state renormalization reported here, which we infer are general of low interacting and well-defined adatom arrays., Comment: 3 figures and main text SI missing

Resumen del trabajo presentado a la Trends in Nanotechnology (TNT) International Conference, celebrada en San Sebastian (España) del 30 de septiembre al 4 de octubre de 2019., Organic nanoporous networks grown on (111) noble metal surfaces are highly successful model systems to study scattering electron phenomena. On such surfaces, the 2D molecular scaffolds are able to confine the surface state electrons and are commonly named “quantum dot arrays”. The resulting confined states result in sizable energy shifts of the Shockley states and the formation of shallow bands, as a results from the repulsive scattering at the molecular walls and partial quantum confinement within each pore. We have studied 6 extended 2D nanoporous networks grown on noble metal surfaces which yield single domain structures. Our findings show that depending on the geometry and building units it is possible to tune the energy shifts in opposite directions (towards and away from the Fermi energy), independently of the substrate. The nature of this effect is related to metal-organic overlayer-substrate interactions in the form of adatom-surface state hybridizations. The electronic structure in all cases is determined by two state-of-theart, highly complementary techniques (STM and ARPES), and supported by first principles and model calculations.

Resumen del trabajo presentado a la XXXVII Reunión Bienal de la Real Sociedad Española de Física celebrada en Zaragoza del 15 al 19 de julio de 2019., The achievement of single atom arrays is key to new fundamental properties that lead to exciting physical properties, like for instance single-atom magnets. However, the resulting position of these atoms has a strong dependence on the supporting substrate and the system temperature. Liquid helium temperatures are required to freeze the atoms, which are often found random sites. A way to generate precise arrays of single atoms stable up to room temperature is the growth of self-assembled metalorganic coordination networks (MOCN) using organic molecules as spacers. Here, by means of STM/STS we probe the electronic properties of different single coordinating atoms embedded in an array di-cyano anthracene (DCA) molecules formed upon the three (111) noble metal surfaces. We have achieved these spontaneously formed MOCN using Fe, Co or Cu (see Fig. 1). We observe distinct spectroscopic fingerprints in the LDOS that leads to shifts of the molecular LUMO levels and relevant surface state pore confinements. We will discuss the effect that the different chemical species and the substrate have on the overall electronic properties of the system.

Resumen del trabajo presentado a la 8th International Conference on Scanning Probe Spectroscopy (SPS), celebrada en Hamburgo (Alemania) del 17 al 20 de junio de 2019., On-surface synthesized Graphene nanoribbons (GNRs) and oligophenylene chains provide a vast playground for developing organic semiconductors with distinct electronic properties. Studies on aligned poly-(paraphenylene) and armchair-GNRs resulted in highly dispersive electronic bands with large HOMO-LUMO gap. However, generating non-straight atomically precise and per fectly aligned chains allows us to go beyond the use of local techniques (STS) and complement it with averaging techniques (ARPES). Combining on-surface synthesis processes and the use of vicinal Ag(111) surfaces we achieved the formation of a monolayer of poly-(metaphenylene) (PMP) zigzag chains for the first time. We use STS and ARPES techniques to unraveled the band structure and HOMO-LUMO gap of zigzag chains. We find that the electronic structure presents weakly dispersive bands with an increase of its gap that is compatible with 1D electron confinement within straight sections. Both magnitudes are observed to vary with the straight section length following a 1/N tendency. These results, supported with DFT calculations, suggest a strong tunability of the polymer’s electronic properties that can be correlated to its topology.

Resumen del trabajo presentado a la XXXVII Reunión Bienal de la Real Sociedad Española de Física celebrada en Zaragoza del 15 al 19 de julio de 2019., Nanostructured Fe clusters whose atoms have a low average coordination number are expected to present enhanced orbital magnetic moment and anisotropy. Metal-organic interactions exhibit custom reversibility in bond formation that may result in large and extended self-assembled structures. Under ultra-high vacuum conditions, we use a Cu(111) monocrystal as substrate and generate an extended metalorganic network that fully covers its surface, which is stable at room temperature. When Fe is evaporated onto this molecular array, instead of the usual triangular bi-layer islands, single atomic height nanoclusters are formed (Fig. 1). The obtained structures are characterized as a function of coverage and temperature by means of Scanning Tunneling Microscopy. We find that both parameters affect the resulting nanodot sizes implying that a certain control can be exerted on its fabrication. Moreover, X-ray Magnetic Circular Dichroism experiments onto these samples show that the Fe nanostructures, which are stable at room temperature, significantly change the magnetic anisotropy compared to the case when the molecular layer is missing.

Resumen del póster presentado a la 7th European Conference on Molecular Magnetism (ECMM), celebrada en Florencia (Italia) del 15 al 18 de septiembre de 2019., Molecular overlayers on solid substrates have a broad field of application in catalysis, sensing, molecular electronics, light-to-energy conversion, etc. In particular, iron-phtalocyanines (FePc) are being investigated as viable substitutes for precious metals in catalysis of the Oxygen Reduction. Recent studies of FePc on Ag(110) have shown that sub-monolayer phases are catalitically active; remarkably, in oxygen-dosed phases O2 intercalates between the molecules and the surface, thereby substantially changing the Fe magnetic moment. Reversible switching of the Fe magnetic moment in some low-density (LD-R1/R2) FePc phases upon an oxygenation-annealing cycle has been demonstrated. In this contribution, we report on the oxygenation capabilities and associated magneto-structural changes of higher-density FePc/Ag(110) phases, the oblique (OB) and square (SQ)/quasi-squared (R3) high-density single monolayer phases, investigated by combining highresolution Scanning Tunneling Microscopy (STM), Scanning Tunneling Spectroscopy (STS), Density Functional Theory (DFT) simulations and x-ray magnetic circular dichroism (XMCD) at the Fe L2,3, edge. The STM images reveal the steric impediments of high-density phases to allocate O2 between the FePc and the substrate, which result in less efficient oxygenation / deoxydation processes compared to previously reported LD phases. In the SQ/R3 squared phases, only a fraction of the molecules are able to oxygenate, rotating and suffering a displacement. For the OB oblique phase, the oxygenation efficiency is smaller; and among the oxygenated molecules, only a minor fraction do rotate, while the majority allocate O2 without rotation. The XMCD spectra of the oxygenated phases reflect the different distribution of non-oxygenated, oxygenated-rotated and non-rotated species in the samples.

Trabajo presentado al 32nd Symposium on Surface Science (3S'19), celebrado en Baqueira Beret, Lleida (España) del 10 al 16 de marzo de 2019., Support by the Spanish Ministry of Economy, Industry and Competitiveness (MINECO, Grant No. MAT2016-78293-C6-6-R) from the regional Government of Aragón (RASMIA project) and from the European Regional Development Fund (ERDF) under the program Interreg V-A España-Francia-Andorra (Contract No. EFA 194/16 TNSI) is thankfully acknowledged.

Trabajo presentado a la X Iberian Conference on Tribology y a la XI Iberian Vacuum Conference (IBERTRIVA), celebradas en Sevilla (España) del 26 al 28 de junio de 2019.

Trabajo presentado a la XXXVII Reunión Bienal de la Real Sociedad Española de Física celebrada en Zaragoza del 15 al 19 de julio de 2019., Organic nanoporous networks grown on (111) noble metal surfaces, also referred to as quantum dot arrays since they can confine surface state electrons, are highly successful model systems to study scattering phenomena. On such surfaces, the 2D molecular scaffolds, commonly exhibit an upward energy shift of the Shockley state and the formation of shallow bands, which results from the repulsive scattering at the molecular walls and partial quantum confinement within each nanodot. In this work, we present experimental evidence of a tunable downward energy shift through scalable metalorganic nanoporous networks grown on Au(111). The electronic structure is determined by two state-ofthe- art, highly complementary techniques (STM and ARPES), and supported by first principles and model calculation. Notably, the counterintuitive downshift is gradual with decreasing pore size and increasing adatom density, something that cannot be explained through standard quantum confinement in the molecular cavity. Therefore we assign the origin of this effect to metal-organic overlayer-substrate interactions in the form of adatom-surface state hybridizations. This local coupling keeps the Shockley state nature, but renormalizes it, thereby changing its fundamental energy and effective mass. The absence to date of the experimental band structure resulting from single adatom metal-coordinated nanoporous networks has precluded the observation of the significant surface state renormalization we have observed.

Póster presentado a la XXXVII Reunión Bienal de la Real Sociedad Española de Física celebrada en Zaragoza del 15 al 19 de julio de 2019., Molecular overlayers on ordered substrates have a broad field of application in catalysis, sensing, molecular electronics, etc. Recent studies of FePc on Ag(110) have shown that sub-monolayer phases are catalitically active: in oxygen-dosed phases, O2 intercalates between the molecules and the surface, substantially changing the Fe magnetic moment. Reversible switching of this moment in low-density FePc phases upon an oxygenation - annealing cycle has been demonstrated. A continuous FePc monolayer on Ag(110) displays several phases, with different FePc density as a function of the molecular coverage. At low coverage, two degenerate but structurally distinct low-density superstructures simultaneously appear after a - 450 K annealing, namely a c(10x4) and a p(10x4)-phase. At higher coverages, a denser oblique phase O(1±4,4-+3) is stablished after annealing. At even higher coverage, denser phases do form, namely a >quasi-square> phase (R3) and a square phase (SQ). The different FePc phases have been oxygen-dosed (10-100 L). Remarkably, in oxygen-dosed phases O2 dissociates and intercalates between the molecules and the surface substantially changing the Fe magnetic moment. X-ray absorption combined with STM images allow us to determine the effectivity of the oxygenation procedure, as a function of the 20 structural phase, and to correlate it with the average magnetic moment as measured by XMCD at the Fe L2,3-edges. Sum rule analysis yield the spin and orbital magnetic moments for each sample. lt is concluded that all characterised phases display planar anisotropy, and the values of meff are about one order of magnitude larger than mL in clear contrast to the FePc molecule in bulk or in multilayer, wich shows a larger orbital moment. Our work shows how oxidation and therefore magnetic moment switching depends on the steric facility for the molecules to form the Ag(110)-0xygen-FePc ensemble, which is geometrically hampered in high density phases.

Resumen del trabajo presentado al Joint Meeting of the DPG and EPS Condensed Matter Divisions (CMD27), celebrado en Berlin (Alemania) del 11 al 16 de marzo de 2018., Quantum dot (QD) arrays on surfaces, in the form of nanoporous networks, are candidates for studying fundamental physical phenomena such as 2DEG confinement. Tunability has been accomplished by varying the pore size, geometrical shape and molecule substrate interactions. Moreover, inter-dot coupling is validated by photoemission through the generation of new dispersive bands and modulated through thermodynamics and the condensation of guest elements. Here, we validate the 2DEGs’ modification through inter-dot barrier width by STM/STS/AFM, ARPES and extended model calculations. We engineer the inter-dot barrier width by substitution of a single atom in a haloaromatic compound and tune the confinement properties at each nanopore, affecting the degree of QD intercoupling both on bulk and thin Ag films alike.

Resumen del póster presentado a la Conferencia bienal Fuerzas y Túnel, celebrada en Jaca (España) del 27 al 29 de junio de 2018., One of the key prerequisite for the optimal performance of organic opto-electronic devices is an efficient charge-carrier transport into and out of the organic semiconductor material. Carrier injection in turn strongly depends on the molecular level alignment of the organic semiconductor material against the fermi level of the conducting electrodes. In a recent work we studied the evolution of molecular levels of Fe-phthalocyanine with increasing layer thickness on a gold (111) surface. By means of STM and STS we found that beyond the strong hybridization of the electronic states of the 1st molecular monolayer with the metallic substrate, the gap between the frontier orbitals is still strongly influenced at the 5th mono layer away from the surface. This sequential decrease of the HOMO-LUMO gap towards the metallic electrode should strongly support the charge-carrier injection for this kind of materials. Accordingly, such a layer- wise STM/STS investigation can give a detailed atomistic insight into electronic processes at metal/organic interfaces towards the bulk material and might help to improve the design of organic opto-electronic devices.

Póster presentado a la Conferencia bienal Fuerzas y Túnel, celebrada en Jaca (España) del 27 al 29 de junio de 2018., Quantum dot (QD) arrays on surfaces, generated through molecular self-assembly processes, have so far provided researchers with a vast playground to study the electronic properties of new and exotic 2D materials in ultra-high-vacuum (UHV) conditions. By selecting the proper molecular constituents (tectons) and substrate, long-range ordered, periodic and robust nanoporous networks have been achieved, ranging from hydrogen-bonded to metal-organic structures. These are candidates for studying fundamental physical phenomena such as confinement through the scattering of two-dimensional electron gases (2DEGs). Indeed, confinement tunability has already been accomplished by varying the pore (i.e. quantum dot) dimensions, geometrical shape and molecule substrate interactions. In addition, inter-dot coupling has been shown by photoemission that can be modulated through thermodynamics and the condensation of guest elements (Xe atoms). To date, 2DEGs' modification through inter-dot barrier width variations has not been experimentally demonstrated. Herein, sustained upon a combination of local scanning probes (STM/STS/AFM), angle resolved photoemission spectroscopy (ARPES) and extended model calculations, we show that we can precisely engineer the inter-dot barrier width by substitution of a single atom in a haloaromatic compound. As a result, we tune the confinement properties at each nanopore affecting the degree of QD intercoupling both on bulk and thin Ag films alike. Our findings complete the toolbox for tuning surface electronic properties, which started in the 90's with the quantum corrals.

Resumen del trabajo presentado al Symposium on Surface Science (3S), celebrado en St. Christoph am Arlberg (Austria) del 25 de febrero al 10 de marzo de 2018., The challenge of synthesizing graphene nanoribbons (GNRs) with atomic precision is currently being pursued along a one-way road, based on the synthesis of adequate molecular precursors that react in predefined ways and form GNRs through self-assembly processes. Adding a new direction to this readily successful approach, the synthetic options for GNRs are expected to multiply, especially if both approaches can be combined. We show here how, still based on self-assembly to maintain the atomic precision not yet achievable with top-down methods, selectivity in the GNR synthesis can be guided, instead of by designed reactants, by an adequately nanotemplated substrate. This new strategy´s proof-of-concept compares experiments using 4,4´´-dibromo-para-terphenyl as molecular precursor on flat Au(111) and stepped Au(322) substrates. On Au(111), the reactant first polymerizes into poly-para-phenylene (PPP) at moderate temperatures below 200 ºC. Annealing to higher temperatures drives the lateral fusion of PPP chains through cyclo-dehydrogenation, ending up with graphene nanoribbons of varying width depending on the number of polymers involved. The resulting samples are thus interesting to study width-dependent properties and phenomena in GNRs. We have used such samples to characterize the width-dependent band gap of GNRs and, most importantly, the associated evolution of the energy level alignment of frontier bands. Doing so, a Fermi level pinning scenario of the valence band has been found for GNRs displaying band gaps below ~1.7 eV.[1] However, from the synthetic point of view, selectivity towards particular GNRs is completely missing. A completely different scenario is found on Au(322). The polymerization and cyclodehydrogenation reactions occur in a similar way. However, the periodic steps of Au(322) limits the number of fusing polymers to two, resulting in the selective synthesis of 6 atomwide armchair GNRs (6-aGNRs). In addition, all GNRs being uniaxially aligned along the substrate´s steps, we have been able to characterize the sample´s valence band properties by angle resolved photoemission spectroscopy. Complemented with scanning tunneling spectroscopy measurements and density functional theory calculations, we end up with a fully coherent and complete picture of the electronic properties of 6-aGNRs., Support by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 635919), from the Spanish Ministry of Economy, Industry and Competitiveness (MINECO, Grant No. MAT2016-78293-C6), and from the Basque Government (Grant No. IT-621-13) is gratefully acknowledged.

Resumen del trabajo presentado a la Conferencia bienal Fuerzas y Túnel, celebrada en Jaca (España) del 27 al 29 de junio de 2018., Carbon based low-dimensional nanostructures such as on-surface synthesized Graphene nanoribbons (GNRs) and oligophenylene chains provide a vast playground for developing organic semiconductors with specific electronic properties. For instance, recent ARPES and STM/STS band structure studies on macroscopically aligned poly (para-phenylene) (PPP) and armchair-GNRs resulted in highly dispersive electronic bands with a large HOMO-LUMO gap. Analogously, we generate atomically precise, wellaligned and covalently bonded zigzag polymers on a curved vicinal Ag(111) surface. With the use of ARPES, we unravel its band structure for the first time and find weakly dispersive bands with considerably increased HOMO LUMO gap. These results, supported with DFT calculations, suggest a strong tunability of the polymer’s electronic properties, which can be correlated to its topology.

Trabajo presentado al X Meeting de GEFES (División de Física de la Materia Condensada de la Real Sociedad Española de Física), celebrado en Valencia del 24 al 26 de enero de 2018., This work focuses on the growth and characterization of three different transition metals (Mn, Fe and Co) upon selected molecular networks under ultra-high vacuum conditions. The resulting self-assembled structures are characterized by means of Scanning Tunneling Microscopy (STM) and Low Energy Electron Diffraction (LEED). We use a Cu(111) monocrystal as substrate and generate two well-characterized and extended molecular networks that are partially covered or disrupted by the addition of the transition metals. From the highly resolved STM study we can study their mutual interaction and we detect structures that vary from regular nanodots to one dimensional chains.

Resumen del trabajo presentado a la 21st International Conference on Magnetism (ICM), celebrada en San Francisco (US) del 15 al 20 de julio de 2018., Molecular overlayers on ordered substrates have a broad field of application in catalysis, sensing, molecular electronics, etc. Recent studies of FePc on Ag(110) have shown that sub-monolayer phases are catalitically active: in oxygen-dosed phases, O2 intercalates between the molecules and the surface, substantially changing the Fe magnetic moment. Reversible switching of this moment in low-density FePc phases upon an oxygenation - annealing cycle has been demonstrated. A continuous FePc monolayer on Ag(110) displays several phases, with different FePc density as a function of the molecular coverage. At low coverage, two degenerate but structurally distinct low-density superstructures simultaneously appear after a ~ 450 K annealing, namely a c(10×4)- and a p(10×4)-phase. At higher coverages, a denser oblique phase O(1±4,4-+3) is stablished after annealing. At even higher coverage, denser phases do form, namely a “quasi-square” phase (R3) and a square phase (SQ). The different FePc phases have been oxygen-dosed (10-100 L). Remarkably, in oxygen-dosed phases O2 dissociates and intercalates between the molecules and the surface substantially changing the Fe magnetic moment. X-ray absorption combined with STM images allow us to determine the effectivity of the oxygenation procedure, as a function of the 2D structural phase, and to correlate it with the average magnetic moment as measured by XMCD at the Fe L2,3–edges. Sum rule analysis yield the spin and orbital magnetic moments for each sample. It is concluded that all characterised phases display planar anisotropy, and the values of mseff are about one order of magnitude larger than mL in clear contrast to the FePc molecule in bulk or in multilayer, wich shows a much larger orbital moment. Our work shows how oxidation and therefore magnetic moment switching depends on the steric facility for the molecules to form the Ag(110)-Oxygen-FePc ensemble, which is geometrically hampered in high density phases.

Resumen del trabajo presentado a la International Conference on Nanoscience + Technology (ICN+T), celebrada en Brno (Czech Republic) del 22 al 27 de julio de 2018., The tunable electronic structure of Graphene Nanoribbons (GNRs) with different edge types has provoked great interest due to potential applications in electronic devices as molecular diodes or transistors. Thanks to the on-surface synthesis of chemically customized molecular precursors, nanoribbons with atomically defined structure can be grown. This high precision in their bottom-up growth allows to tune their electronic structure via width control or chemical doping. Here we use two different strategies to chemically modify 7-armchair GNRs (7-AGNRs) to clarify how the chemical modifications on the nanoribbons’ structure affect their electronic properties. By means of Scanning Tunneling Spectroscopy we tackle with atomic precision this issue on 7-AGNRs with substitutional nitrile functional groups at the ribbons’ edges and on 7-AGNRs with substitutional boron atoms within the ribbons’ backbone. We find that in the first case the CN groups lead to an efficient n-like doping of the ribbon, while in the second case B atoms induce the formation of a new acceptor band and bandgap renormalization.

Resumen del trabajo presentado al 2nd ELECMI International Workshop celebrado en Zaragoza (España) del 11 al 13 de junio de 2018., In the early 1900's Fritz Ullmann first reported the synthesis of biaryls from aryl halides mediated by a fine copper powder, demonstrating with this the aromatic nucleophilic substitution mediated by copper, now known as Ullmann condensation reaction. More than hundred years after, this reaction is routinely used in numerous industrial applications and, nowadays it becomes widely used for the synthesis on metal surfaces of atomically precise graphene nanoribbons. The next step to move toward device applications requires performing the synthesis directly on suitable substrates such as semiconducting, insulating or magnetic substrates. Whit in this context, in the present work we explore the Ullmann based synthesis of polymers on magnetic and insulating substrates. In particular we demonstrate the aryl homocoupling synthesis of 4,4-Dibromo (or diiodo)-p-terphenyl precursor into molecular poly-p-phenylene wires on the semiconductor TiO2 surface and on the bimetallic (and ferromagnetic) GdAu2 surface alloy. Moreover, we propose a reaction pathway during the polymerization. To monitor the chemical reaction complementary microscopic and spectroscopic surface science techniques (scanning tunneling microscopy, X-ray photoemission spectroscopy, angle-resolved Photoemission spectroscopy) are used.

Resumen del trabajo presentado a la 21st International Conference on Magnetism (ICM), celebrada en San Francisco (US) del 15 al 20 de julio de 2018., Metal-organic interactions are weaker than the covalent ones, allowing the bond formation and breaking necessary to self-assemble, but are stronger than the purely intermolecular interactions. This is why metalorganic networks own so interesting properties. In this work, we grow and characterize Fe upon a selected molecular network under ultra-high vacuum conditions. The resulting self-assembled structures are characterized by means of Scanning Tunnelling Microscopy and Low Energy Electron Diffraction. We use a Cu(111) monocrystal as substrate and generate a self-assembled, extended metalorganic network which is stable at room temperature. It will be shown that depending on the molecular coverage the porous network evolves into a compact structure detectable by LEED. Once the porous network is formed, Fe atoms are evaporated on the surface. Instead of he usual bi-layer islands, the Fe forms single atomic height nanoclusters. We have performed a STM study of the Fe nanostructures as a function of coverage and deposition temperature. In addition, X-ray Magnetic Circular Dichroism experiments at the European Synchrotron Radiation Facility show that the Fe nanostructures (stable also at room temperature) significantly change their magnetic anisotropy compared to the case when the molecular layer is missing.

Resumen del trabajo presentado al International workshop On-Surface Synthesis (OSS), celebrado en Sant Feliu de Guíxol (España) del 23 al 28 de septiembre de 2018., Carbon based low-dimensional nanostructures such as on-surface synthesized Graphene nanoribbons (GNRs) and oligophenylene chains provide a vast playground for developing organic semiconductors with distinct electronic properties.

Graphene is a material of great versatility. For instance, the sp2 covalent bonds linking the C atoms in extensive 2D sheets confers great mechanical strength3. Moreover, it exhibits huge electronic mobility and sensitivity of conductivity to external parameters, which makes it interesting towards microelectronics, as well as in the energy sector and data storage. All these properties add to the prospect of numerous applications in the field of materials science. Notably, the electronic properties of graphene are tunable8. When graphene shrinks in one of its dimensions to form ribbons, its conductivity decreases and transforms from metallic to semiconductor below a critical width9, while still preserving the appealing properties of its extended form. Thus, it is of interest to the field of molecular electronics in order to build nanotransistors. The conductivity dependence of graphene nanoribbons on the width has a characteristic length scale in the range of Angstroms8. Therefore, an extremely precise manufacturing method is required. On Surface synthesis is a bottom-up approach that allows graphene manufacturing with atomic precision featuring exact width and edge geometry10. This is nowadays far better than the top-down methods, whose size limit is currently on the scale of tens of nanometers11 and are prone to produce spurious effects due to sample damage. Nanotechnology with such precision requires cutting-edge experimental infrastructures. Based on state of the art Scanning Tunnelling Microscope (STM) of the Laboratorio de Microscopías Avanzadas (LMA), the electronic structure of the different parts of the nanoribbons has been locally studied, facilitating a deeper comprehension of the quantum nature responsible for their superior properties. The aim of this work seeks the experimental accomplishment of these points: - Synthesize chiral (3,1)-GNR from the selected precursor on Au(111). - Study their morphology and electronic structure, focusing on the identification of expected edge states. - To develop new methods to decouple the GNRs from the substrate by addition of NaCl and determine its effectiveness. Decoupling the molecular structures would be used both to study the ribbons with higher resolution, and to release them from the substrate. A new type of chiral nanoribbon, the (3,1)-cGNR, has been successfully synthesised from dBQA precursors. This molecular precursors, the subsequent polimerization steps and the nanoribbons were structurally confirmed by topographic STM images. Specifically, the period and internal structures have been confirmed using topography imaging with normal metallic tips and functionalized ones, which verified to match the theoretical calculations. Furthermore, its electronic properties have been successfully studied, and the higher part of its valence ban, as well as the presence of edge states in the vicinity of the Fermi level have been confirmed. In addition, the NaCl growth and response to temperature after deposition onto Au(111) showed different density agglomeration into islands. This effect, in presence of cGNR caused a generalized displacement of the molecular structures, affecting its orientation with respect to the substrate and causing some of them to stack on top of other cGNRs. This resulted in an effective ribbon decoupling from the metallic substrate, which increased the energy and spatial resolution when studying the ribbons, both on the STM images and the STS spectra. This allowed us to investigate its internal electronic structure without the need for functionalising the tip. Indeed, the performance of a regular metal tip on stacked ribbons parallels the one of functionalized tips on a metal surface, making the burdensome process of tip functionalization unnecessary. In the STS spectra, the decoupling caused a sharpening of the bands that allows its proper identification. As outlook, we propose to use this decoupling method as a simple technique to study the electronic structure of the edge states in cGNR, or as a tool to spontaneously detach the ribbons from the substrate for a possible transferring method to Si-based substrates GNRs on a larger scale, bridging the gap between on-surface synthesis and electronic applications

Resumen del trabajo presentado a la Conferencia bienal Fuerzas y Túnel, celebrada en Jaca (España) del 27 al 29 de junio de 2018., Metal-organic interactions are weaker than covalent ones, allowing the bond breaking and formation necessary to generate large and extended self-assembled structures. Under ultra-high vacuum conditions, we grow and characterize Fe clusters using a selected metalorganic network as a buffer layer. The resulting self-assembled structures are characterized by means of Scanning Tunnelling Microscopy and Low Energy Electron Diffraction. We use a Cu(111) monocrystal as substrate and generate an extended metalorganic network, which is stable at room temperature. It will be shown that depending on the molecular coverage the porous network evolves into a compact structure detectable by LEED. Once the porous network is formed, Fe atoms are evaporated on the surface. Instead of the usual bi-layer islands, the Fe forms single atomic height nanoclusters. We have performed a STM study of such Fe nanostructures as a function of coverage and deposition temperature. In addition, X-ray Magnetic Circular Dichroism (XMCD) experiments at the ESRF show that the Fe nanostructures (stable at room temperature) significantly change the magnetic anisotropy compared to the case when the molecular layer is missing.

Resumen del trabajo presentado al Symposium on Surface Science (3S), celebrado en St. Christoph am Arlberg (Austria) del 25 de febrero al 10 de marzo de 2018., Vicinal surfaces with arrays of atomic steps have important applications in catalysis, nanostructure growth, or electronic band engineering, since steps are active sites for chemical reactions, as well as nucleation and electron scattering centers. Given the infinite possibilities for the orientation of a vicinal surface, it is important to perform systematic investigations, in order to identify optimal substrates for specific functions. Using macroscopically curved crystal samples one can systematically probe entire families of vicinal planes with standard surface science techniques. This is done here for vicinal Ag(111) surfaces featuring the so-called fully- or 100%-kinked steps. Fully-kinked monatomic steps (height h=2.35 Å) run parallel to the [112̅] direction and have six-fold atomic coordination, as compared with the seven-fold coordinated close-packed steps, which are oriented along the [11̅0] direction. In such fully-kinked Ag(111) vicinals we investigate electronic and structural properties with STM, LEED and Angle-Resolved Photoemission (ARPES), and test both the growth of BiAg2 alloys and the on-surface synthesis of zig-zag polymers. The sample is a Ag single crystal curved around the (645) direction, such that the vicinal angle α can be tuned from the Ag(111) plane, beyond the Ag(423) surface, up to α=18º. As done in previous works on close-packed Ag(111), Cu(111) and Au(111) vicinals, we study the probability distribution of the terrace size d as a function of the vicinal angle from STM images, and probe the scattering of the Shockley state at the fully-kinked step by ARPES. We find that fully-kinked vicinals exhibit exceptional ordering, allowing one to visualize the universal, structural transformation of vicinal metal surfaces with unprecedented precision. This opens the way to a fine test of statistical models of step-lattices largely debated in the past. As shown in the Figure, the Shockley state analysis reveals a much stronger scattering strength at the fully-kinked step when compared to the closed-packed, leading to a dramatic decrease of the surface electron density in vicinal surfaces, that is, to a complete electron depletion of Ag(111) terraces with d, We acknowledge financial support from the Spanish Ministry of Economy (grant MAT2017-88374-P) and the Basque Government (grant IT621-13).

Resumen del póster presentado al International workshop On-Surface Synthesis (OSS), celebrado en Sant Feliu de Guíxol (España) del 23 al 28 de septiembre de 2018., 2D Periodic arrays of quantum well states arise from the interaction of organic on-surface networks with free electron like Shockley states in the substrate. The spatially periodic interaction of the network backbone with the surface state leads to detectable, localized and delocalized electronic states, ultimately a coherent Bloch wave. We investigate the electronic imprint left in this complex surface electronic system by the adsorption of octa-ethyl-porphyrin (OEP) in the pores of the network. By combining non-local ARPES and local STS experiments we find that the electronic states in the porous network are strongly modified by the OEP guest molecules. These effects are visualized locally as they affect the neighbouring confined states and mesoscopically as band changes upon the quantum dot band structure (Bloch states). The ‘pillow effect’ originating from Pauli repulsion can be systematically investigated by assembling different guest molecules into the 2D quantum well array.

Resumen del trabajo presentado al 2nd ELECMI International Workshop, celebrado en Zaragoza (España) del 11 al 13 de junio de 2018.

Resumen del trabajo presentado a la QMol Conference: Operating Quantum States in Atoms and Molecular at Surfaces, celebrada en Ascona (Suiza) del 10 al 14 de septiembre de 2017., Quantum dot (QD) arrays on surfaces, generated through molecular self-assembly processes, have so far provided researchers with a vast playground to study the electronic properties of new and exotic 20 materials in ultra-high-vacuum (UHV) conditions. By selecting the proper molecular constituents (tectons) and substrate, long-range ordered, periodic and robust nanoporous networks have been achieved, ranging from hydrogen-bonded to metal-organic structures. Not only do they stand out as ideal templates for nanopatterning, but also as adequate candidates for studying fundamental physical phenomena such as confinement through the scattering of two-dimensional electron gases (2DEGs). lndeed, confinement tunability has already been accomplished by varying the pore (i.e. quantum dot) dimensions, geometrical shape and molecule substrate interactions. In addition, inter-dot coupling has been shown by photoemission through the generation of new dispersive bands that can be modulated through thermodynamics [S) and the condensation of guest elements (Xe atoms). To date, the modification of 2DEGs through inter-dot barrier width variations has not been experimentally demonstrated. Herein, sustained upon a combination of local scanning probes (STM/STS/AFM), angle resolved photoemission spectroscopy (ARPES) and extended model calculations, we show that we can precisely engineer the inter-dot barrier width by substitution of a single atom in a haloaromatic compound. As a result, we tune the confinement properties at each nanopore affecting the degree of QD intercoupling both on bulk and thin Ag films alike. These findings pave the way to reach full control over 2DEGs with the prospect of becoming key for future electronic devices.

Resumen del trabajo presentado a la 13th European Conference on Surface Crystallography and Dynamics, celebrada en Donostia-San Sebastián (España) del 19 al 21 de junio de 2017., Crystal surfaces with a small deviation from a high symmetry plane have enormous potential for surface science research and applications. Such "vicinal" planes, characterized by arrays of atomic steps, exhibit distinct chemical and electronic properties, and are useful templates to achieve uniaxial symmetry and single azimuthal domains in epitaxial layers, or to drive self-organized nanostructure growth. A way of systematically studying step-related phenomena is to use curved crystals. The beauty of these special substrates is that they integrate all vicinal directions, which are accessible by scanning the source beam or tip along the curvature of the crystal. In this way, the sample provides a smooth variation of the step density that is directly related to a terrace width variation from sub-micron to the nanometer range. These samples has allowed us to revisit old and to explore new surface science problems. I will discuss step-lattice interactions, scattering of surface states and growth. Our experiments demonstrate the immense power of the curved surface approach, which allows one to directly image fine physical-chemical properties of surface systems, such as to settle controversial issues and to unveil new phenomena.

Resumen del trabajo presentado a la 13th European Conference on Surface Crystallography and Dynamics, celebrada en Donostia-San Sebastián (España) del 19 al 21 de junio de 2017., The thermal excitation of step-edge atoms into "kinks" (e-εkT) is the essence of the step dynamics on a crystalsurface. At a vicinal surface with high step densities, kinks also influence the equilibrium shape at finite temperature. At T=0, the density of kinks strongly depends on the in-plane orientation of the surface.

Resumen del trabajo presentado a la QMol Conference: Operating Quantum States in Atoms and Molecular at Surfaces, celebrada en Ascona (Suiza) del 10 al 14 de septiembre de 2017., Supramolecular chemistry provides the means to generate larger structures than their original building blocks. A wealth of different structures coordinated through all existing intramolecular and substrate mediated interactions have been found to develop at the surface of coinage metals. Often the substrate acts as a surface catalyzer for the molecules, defining the final structure of the system. This is the case of a Perylene derivative (OPOI) which upon thermal activation on Cu(111) it undergoes a triple dehydrogenation process (3deh-OPOI), triggering the formation of a highlyordered metal-organic nanoporous network. 20 organic networks have been shown to scatter surface electrons, leading to their partial localization within its pores. By means of angle-resolved photoelectron spectroscopy (ARPES), we study the temperature dependence of the partially localized electronic band and corroborate that it mirrors the behavior of the Shockley state. In addition, the partially confined state can be modified by the presence of Xe guests. We follow such changes with the use of ARPES and observe an overall energy shift simultaneous to the appearance of the Xe core levels in the spectra. These results provide insight into the very nature of the electronic effects and their evolution in the presence of guests within these porous networks.

On surface síntesis de estructuras covalentes para aplicaciones en magnetoelectronica. Estudio de su estructura mediante STM en ultra alto vacío y en condiciones criogénicas.

This work focuses on the growth and characterization of three different transition metals (Mn, Fe and Co) upon selected molecular networks under ultra-high vacuum conditions. The resulting self-assembled structures are characterized by means of Scanning Tunnelling Microscopy and Low Energy Electron Diffraction. We use a Cu(111) monocrystal as substrate and generate two well-characterized and extended molecular networks that are partially covered or disrupted by the addition of the transition metals. From the highly resolved STM images we can study their mutual interaction and we detect structures that vary from regular nanodots to one dimensional chains.

Resumen del trabajo presentado a la 13th European Conference on Surface Crystallography and Dynamics, celebrada en Donostia-San Sebastián (España) del 19 al 21 de junio de 2017., Graphene nanoribbons are an interesting class of carbon materials that on one side, exhibit some superlative properties of graphene, while on the other side possess high tunability of their electronic and structural properties.

Surface confined dehalogenation reactions are versatile bottom-up approaches for the synthesis of carbon-based nanostructures with predefined chemical properties. However, for devices generally requiring low conductivity substrates, potential applications are so far severely hampered by the necessity of a metallic surface to catalyze the reactions. In this work we report the synthesis of ordered arrays of poly(p-phenylene) chains on the surface of semiconducting TiO2(110) via a dehalogenative homocoupling of 4,4"-dibromoterphenyl precursors. The supramolecular phase is clearly distinguished from the polymeric one using low energy electron diffraction and scanning tunneling microscopy as the substrate temperature used for deposition is varied. X ray photoelectron spectroscopy of C 1s and Br 3d core levels traces the temperature of the onset of dehalogenation to around 475 K. Moreover, angle-resolved photoemission spectroscopy and tight-binding calculations identify a highly dispersive band characteristic of a substantial overlap between the precursor's �� states along the polymer, considered as the fingerprint of a successful polymerization. Thus, these results establish the first spectroscopic evidence that atomically precise carbon based nanostructures can readily be synthesized on top of a transition-metal oxide surface, opening the prospect for the bottom-up production of novel molecule-semiconductor devices.

Resumen del póster presentado a la 10th Conferencia Fuerzas y Túnel, celebrada en Girona (España) del 5 al 7 de septiembre de 2016., Generally, two types of graphene-metal interfaces are distinguished: in a strongly interacting regime the characteristic Dirac cone of graphene is heavily obscured while in the weakly interacting regime it is shifted away from the Fermi edge of the metal. Although many examples for both scenarios have been studied both experimentally and theoretically, a precise quanti cation as to the nature of the transition between the two regimes, i.e., whether it is continuous or abrupt in nature, has so far not been reached. Here, we present a combined STM, XPS, ARPES, and DFT study of graphene on Ir(111) where we ne-tune the graphenesubstrate interaction through Fe-Ir alloying below the graphene layer. At a critical concentration of Ir in the Fe layer of around 0.2-0.3, the Dirac cone is restored and can thereafter be continuously tuned across the Fermi level by further increasing the Ir content. Indeed, our study reveals an abrupt transition between a chemisorbed phase at large Fe concentrations and a physisorbed phase beyond the critical concentration which is highly reminiscent of the Gr on the clean Ir(111) surface case.