Maria Carmen Asensio

• Professor
• Professor (Full) at Materials Science Institute of Madrid

Ionic liquids (ILs) have been explored as a way of improving the performance of ZnO-based optoelectronic devices; however, there are few fundamental studies of the IL/ZnO interface. Here, the adsorption of the IL 1-octyl-3-methylimidazolium tetrafluoroborate [C8C1Im][BF4] on ZnO (0001) and ZnO (101¯0) has been studied using synchrotron-based soft X...

Spatially controlling the Fermi level of topological insulators and keeping its electronic states stable are indispensable processes to put this material into practical use for semiconductor spintronics devices. So far, however, such a method has not been established yet. Here we show a novel method for doping hole into n-type topological insulator...

Perovskite materials have demonstrated great potential for a wide range of optoelectronic applications due to their exceptional electronic and optical properties. However, synthesising high-quality perovskite films remains a significant challenge, often hindered by batch-wise processes that suffer from limited control over reaction conditions, scal...

Two-dimensional (2D) van der Waals nanomaterials have attracted considerable attention for potential use in photonic and light–matter applications at the nanoscale. Thanks to their excitonic properties, 2D perovskites are also promising active materials to be included in devices working at room temperature. In this work, we study the presence of ve...

: Sputtering of silicon in a Helium magnetron discharge (MS) has been reported as a bottom-up procedure to obtain He-charged silicon films (i.e. He nanobubbles encapsulated in a silicon matrix). The incorporation of heavier noble gases is demonstrated in this work with a synergistic effect producing increased Ne and Ar incorporations when using He-...

Temperature dependent X-ray photoemission spectroscopy (XPS) has been employed to examine the spin-crossover (SCO) transition in the nanocrystals of 3D Hoffman-like {Fe(pz)[Pt(CN)4]}. Consistent with the existing literature, the temperature-dependent variations in the Fe 2p core-level spectrum provide unambiguous evidence of the spin-state transiti...

We have performed micro-/nanofocused angle-resolved photoemission spectroscopy (ARPES) on cleaved single-crystal surfaces of bismuth to clarify the spatially resolved electronic states. While the dominant area of the cleaved surface was found to display the well-known Rashba-spin-split surface state with the (111)-surface origin, the steplike regio...

Temperature dependent X-ray photoemission spectroscopy (XPS) has been employed to examine the Fe 2p and N 1s core levels of the studied Fe(II) spin crossover (SCO) complexes of interest, namely: Fe(phen)2(NCS)2, [Fe(3-Fpy)2{Ni(CN)4}], and [Fe(3-Fpy)2{Pt(CN)4}]. The changes in the Fe 2p core-level spectra with temperature indicate spin state transit...

A significant step forward in Lithium-ion batteries (LIBs) developments can only be achieved by proposing mold-breaking research based on selecting the best materials for the cell components, optimizing cell manufacture, anticipating the degradation mechanisms of the LIBs, and consolidating the regeneration processes of damaged batteries. LIBs with...

The presence of in-plane chiral effects, hence spin-orbit coupling, is evident in the changes in the photocurrent produced in a TiS3(001) field-effect phototransistor with left versus right circularly polarized light. The direction of the photocurrent is protected by the presence of strong spin-orbit coupling and the anisotropy of the band structur...

The elemental contributions to the conduction bands of the transition-metal trichalcogenides TiS3 and ZrS3 were examined using X-ray absorption spectroscopy, at the Ti and S 2p edges and the Zr 3p edges. A comparative study of these two compounds shows that the bottom of the conduction band, for both TiS3 and ZrS3, is comprised mainly of hybridized...

Two-dimensional (2D) van der Waals nanomaterials have attracted considerable attention for potential use in photonic and optoelectronic applications in the nanoscale, due to their outstanding electrical and optical properties, differing from their bulk state. Currently, 2D perovskite belonging to this group of nanomaterials is widely studied for a...

Our experimental results indicate the formation of extended ordered S–Ti–Se layers (Janus layers) in the Ti(Se1–xSx)2 system. The presence of these layers is observed as a folding of the typical Fermi surface of TiS2 and TiSe2. High-resolution transmission electron microscopy (HRTEM) allows us to observe these layers by a typical rotation of the mo...

The strain in hybrid van der Waals heterostructures, made of two distinct two-dimensional van der Waals materials, offers an interesting handle on their corresponding electronic band structure. Such strain can be engineered by changing the relative crystallographic orientation between the constitutive monolayers, notably, the angular misorientation...

https://www.youtube.com/watch?v=95vTysCQ4LE

Phase separation in the nanometer- to micrometer-scale is characteristic for correlated materials, for example, high temperature superconductors, colossal magnetoresistance manganites, Mott insulators, etc. Resolving the electronic structure with spatially-resolved information is critical for revealing the fundamental physics of such inhomogeneous...

Phase separation in the nanometer- to micrometer-scale is characteristic for correlated materials, for example, high temperature superconductors, colossal magnetoresistance manganites, Mott insulators, etc. Resolving the electronic structure with spatially-resolved information is critical for revealing the fundamental physics of such inhomogeneous...

The elusive crystal structure of the so-called ‘antimonic acid’ has been investigated by means of robust and state-of-the-art techniques. The synergic results of solid-state magic-angle spinning nuclear magnetic resonance spectroscopy and a combined Rietveld refinement from synchrotron X-ray and neutron powder diffraction data reveal that this comp...

New angle-resolved photoelectron spectroscopy (ARPES) data, recorded at several different photon energies from the Si(111)(7 × 7) surface, show that the well-known S1 and S2 surface states that lie in the bulk band gap are localised at specific (adatom and rest atom) sites on the reconstructed surface. The variations in the photoemission intensity...

We study the valence band structure of ReSe2 crystals with varying thickness down to a single layer using nanoscale angle-resolved photoemission spectroscopy and density functional theory. The width of the top valence band in the direction perpendicular to the rhenium chains decreases with decreasing number of layers, from ∼200 meV for the bulk to...

The elusive crystal structure of the socalled “antimonic acid” has been investigated by means of robust and state-of-the-art techniques. The synergic results of solidstate magicangle spinning nuclear magnetic resonance spectroscopy and a combined Rietveld refinement from synchrotron X-ray and neutron powder diffraction data reveal that this compoun...

LiNi0.5Mn1.5O4 (LNMO) is a promising 5V-class electrode for Li-ion batteries but suffers from manganese dissolution and electrolyte decomposition owing to the high working potential. An attractive solution to stabilize the surface chemistry consists in mastering the interface between the LNMO electrode and the liquid electrolyte with a surface prot...

One primary concern in diluted magnetic semiconductors (DMSs) is how to establish a long-range magnetic order with low magnetic doping concentration to maintain the gate tunability of the host semiconductor, as well as to increase Curie temperature. Several van der Waals semiconductors have been investigated recently to demonstrate the magnetic ord...

A Correction to this paper has been published: https://doi.org/10.1038/s41565-020-00821-z.

We study the valence band structure of ReSe$_{2}$ crystals with varying thickness down to a single layer using nanoscale angle-resolved photoemission spectroscopy and density functional theory. The width of the top valence band in the direction perpendicular to the rhenium chains decreases with decreasing number of layers, from 280 meV for the bulk...

The crystal structure of the Sb6O13 oxide, exhibiting a defect pyrochlore crystal structure with atomic vacancies, has been studied using a complete set of state-of-the-art techniques. The degree of antimony disproportionation in Sb3+ and Sb5+ valence states has been directly determined around 36% and 64%, respectively, using X-ray absorption near...

Multilayer graphene and its stacking order provide both fundamentally intriguing properties and technological engineering applications. Several approaches to control the stacking order have been demonstrated, but a method of precisely controlling the number of layers with desired stacking sequences is still lacking. Here, we propose an approach for...

Photocurrent production in the quasi-one-dimensional transition metal trichalcogenides, TiS3(001) and ZrS3(001), was exam-ined using polarization dependent scanning photocurrent microscopy. The photocurrent intensity was strongest when the excitation source was polarized along the 1D chains with dichroic ratios of 4:1 and 1.2:1 for ZrS3 and TiS3, r...

The band structure of the quasi-one-dimensional transition metal trichalcogenide ZrS3(001) was investigated using nanospot angle resolved photoemission spectroscopy (nanoARPES) and shown to have many similarities with the band structure of TiS3(001). We find that ZrS3, like TiS3, is strongly n-type with the top of the valence band ~1.9 eV below the...

The properties of van der Waals (vdW) materials often vary dramatically with the atomic stacking order between layers, but this order can be difficult to control. Trilayer graphene (TLG) stacks in either a semimetallic ABA or a semiconducting ABC configuration with a gate-tunable band gap, but the latter has only been produced by exfoliation. Here...

The combination of monolayers of different two-dimensional (2D) materials into van der Waals hetero-bilayer structures creates unprecedented physical phenomena, acting as a powerful tool for future devices. Understanding and exploiting these phenomena hinge on knowing the electronic structure and the hybridization of hetero-bilayer structures. Here...

Exotic ordered ground states driven by electronic correlations are expected to be induced in monolayer graphene when doped to the Van Hove singularity. Such doping levels are reached by intercalating Gd in graphene on SiC(0001), resulting in a strong homogeneity and stability. The electronic spectrum now exhibits severe renormalizations. Flat bands...

Exotic ordered ground states driven by electronic correlations are expected to be induced in monolayer graphene when doped to the Van Hove singularity. Such doping levels are reached by intercalating Gd in graphene on SiC(0001), resulting in a strong homogeneity and stability. The electronic spectrum now exhibits severe renormalizations. Flat bands...

For quasi-freestanding 2H-TaS2 in monolayer thickness grown by in situ molecular beam epitaxy on graphene on Ir(111) we find unambiguous evidence for a charge density wave close to a 3 × 3 periodicity. Using scanning tunneling spectroscopy we determine the magnitude of the partial charge density wave gap. Angle resolved photoemission spectroscopy,...

Germanene, with Ge atoms packed in a honeycomb lattice, like graphene and silicene, is expected to be a promising material with significant theoretical and practical repercussions. Simulations show that Ge monoatomic sheets have as graphene semi-metallic electronic structure character by a linear dispersion around the Dirac point and charge carrier...

We clarify that the chemisorption of oxygen atoms at the edges is a key contributor to the frequently observed edge enhancement and spatial nonuniformities of photoluminescence (PL) in WS2 monolayer. Here we have investigated with momentum- and real- space nano-imaging of the chemical and electronic density inhomogeneity of WS2 flake. Our finding f...

Ferromagnetic ordering of monolayer vanadium dichalcogenides (VSe2, VS2) has been predicted by density functional theory (DFT) and suggestive experimental evidence for magnetic ordering in VSe2 monolayers has been reported. However, such ferromagnetic ordering would be in stark contradiction to known paramagnetic nature of the bulk VSe2. Herein, we...

We have performed scanning angle-resolved photoemission spectroscopy with a nanometer-sized beam spot (nano-ARPES) on the cleaved surface of Pb5Bi24Se41, which is a member of the (PbSe)5(Bi2Se3)3m homologous series (PSBS) with m = 4 consisting of alternate stacking of the topologically-trivial insulator PbSe bilayer and four quintuple layers (QLs)...

We have performed scanning angle-resolved photoemission spectroscopy with a nanometer-sized beam spot (nano-ARPES) on the cleaved surface of Pb₅Bi₂₄Se₄₁, which is a member of the (PbSe)₅(Bi₂Se₃)_{3 m} homologous series (PSBS) with m = 4 consisting of alternate stacking of th...

Hexagonal boron nitride (hBN) is the supporting substrate of choice for two-dimensional material devices because it is atomically flat and chemically inert. However, due to the small size of mechanically exfoliated hBN flakes, electronic structure studies of 2D materials supported by hBN using angle-resolved photoemission spectroscopy (ARPES) are c...

Hexagonal boron nitride (hBN) is the supporting substrate of choice for two-dimensional material devices because it is atomically flat and chemically inert. However, due to the small size of mechanically exfoliated hBN flakes, electronic structure studies of two-dimensional materials supported by hBN using angle-resolved photoemission spectroscopy...

Electrostatic gating is pervasive in materials science, yet its effects on the electronic band structure of materials has never been revealed directly by angle-resolved photoemission spectroscopy (ARPES), the technique of choice to non-invasively probe the electronic band structure of a material. By means of a state-of-the-art ARPES setup with sub-...

Electrostatic gating is pervasive in materials science, yet its effects on the electronic band structure of materials has never been revealed directly by angle-resolved photoemission spectroscopy (ARPES), the technique of choice to non-invasively probe the electronic band structure of a material. By means of a state-of-the-art ARPES setup with sub-...

Graphene-based materials are widely studied to enable significant improvements in electroanalytical devices requiring new generations of robust, sensitive and low-cost electrodes. In this paper, we present a direct one-step route to synthetize a functional nitrogen-doped graphene film onto a Ni-covered silicon electrode substrate heated at high tem...

In materials with nearly commensurate band filling the electron liquid may spontaneously separate into components with distinct properties, yielding complex intra-and interunit cell ordering patterns and a reduced dimensionality. Polarization-dependent angle-resolved photoemission data with submicron spatial resolution demonstrate such an electroni...

We explore the electrical characteristics of TiS3 nanowire field-effect transistor (FETs), over the wide temperature range from 3 – 350 K. These nanomaterials have a quasi-one-dimensional (1D) crystal structure and exhibit a gate-controlled metal-insulator transition (MIT) in their transfer curves. Their room-temperature mobility is 20 – 30 cm²/Vs,...

Tin sulfide (SnS) is a promising thermoelectric material with advantages of non-toxicity, abundant resources and low cost of its components. However, its figure of merit (ZT) is lower than that of its analogue SnSe, which was recently revealed to have an unprecedentedly high ZT value. Here, we demonstrate the differences of electronic structures be...

Les Très Grandes Infrastructures de Recherche (TGIR) jouent un rôle essentiel dans la recherche fondamentale et appliquée dans un grand nombre de disciplines. Dernièrement, la recherche fondée sur le rayonnement synchrotron de SOLEIL a fourni aussi des avancées inégalées pour l'industrie, en développant une politique d'ouverture vers l'accès des PM...

The authors unanimously wish to retract this Article due to their concerns about the interpretation of the low-energy electron microscopy (LEEM) and diffraction (LEED) patterns reported in the manuscript. In this study, the authors used spatial and angle-resolved photoemission spectroscopy (ARPES) to characterize graphene monolayers grown on copper...

In article number 1801900, Mónica Giménez‐Marqués, Patricia Horcajada, and co‐workers discuss GraftFast, a general grafting method that allows the successful and highly selective attachment of biopolymers on the outer surface of nanometric metal‐organic frameworks, leading to superior chemical and colloidal stability and tuned cell recognition and...

Two-dimensional monochalcogenides (MX) have been identified as a unique and promising class of layered materials in recent years. The valence band of single-layer MX, as predicted by theory, is inverted into a bow-shaped (often referred to as an inverted sombrero) and relatively flat dispersion, which is expected to give rise to strongly correlated...

Controlling the outer surface of nanometric metal–organic frameworks (nanoMOFs) and further understanding the in vivo effect of the coated material are crucial for the convenient biomedical applications of MOFs. However, in most studies, the surface modification protocol is often associated with significant toxicity and/or lack of selectivity. As a...

All-inorganic halide perovskite nanowires (NWs) exhibit improved thermal and hydrolysis stability and could thus play a vital role in nanoscale optoelectronics. Among them, blue-light based devices are extremely limited due to the lack of facile method to obtain high-purity CsPbCl3 NWs. Herein, we report a direct and facile method for the synthesis...

We investigate the electronic and vibrational properties of bottom-up synthesized aligned armchair graphene nanoribbons of N=7 carbon atoms width periodically doped by substitutional boron atoms (B-7AGNRs). Using angle-resolved photoemission spectroscopy (ARPES), we find that the dopant-derived valence and conduction band states are notably hybridi...

Transition metal dichalcogenides exhibit strong quantum confinement effects and the electronic structure is strongly dependent on the number of layers. Resolving the thickness-dependent electronic structure is important. While the electronic structure of atomically thin 2H-MoSe2 or 2H-MoS2 have been explored, experimental electronic structure of 2H...

In recent years there has been growing interest in the electronic properties of 'few layer' graphene films. Twisted layers, different stacking and register with the substrate result in remarkable unconventional couplings. These distinctive electronic behaviours have been attributed to structural differences, even if only a few structural determinat...

The crystallographic stacking order in multilayer graphene plays an important role in determining its electronic properties. It has been predicted that a rhombohedral (ABC) stacking displays a conducting surface state with flat electronic dispersion. In such a flat band, the role of electron-electron correlation is enhanced, possibly resulting in h...

2D layered materials have emerged in recent years as a new platform to host novel electronic, optical, or excitonic physics and develop unprecedented nanoelectronic and energy applications. By definition, these materials are strongly anisotropic between the basal plane and cross the plane. The structural and property anisotropies inside their basal...

Variations of the lattice parameter can significantly change the properties of a material, and, in particular, its electronic behaviour. In the case of graphene, however, variations of the lattice constant with respect to graphite have been limited to less than 2.5% due to its well-established high in-plane stiffness. Here, through systematic elect...

Two-dimensional (2D) layered materials emerge in recent years as a new platform to host novel electronic, optical or excitonic physics and develop unprecedented nanoelectronic and energy applications. By definition, these materials are strongly anisotropic between within the basal plane and cross the plane. The structural and property anisotropies...

Nanometer-sized structures, surfaces and sub-surface phenomena have played an enormous role in science and technological applications and represent a driving-force of current interdisciplinary science. Recent developments include the atomic-scale characterization of nanoparticles, molecular reactions at surfaces, magnetism at the atomic scale, phot...

We propose a novel growth technique, in which graphene is synthesized on capped Cu thin films deposited on c-plane sapphire. The cap is another sapphire plate which is just laid upon the Cu thin film, in direct contact with it. Thanks to this 'contact cap', Cu evaporation can be suppressed at high temperature and the 400 nm-thick Cu films can be an...

Significance Interlayer interaction in van der Waals heterostructures could induce many exotic phenomena. Unlike commensurate heterostructures, incommensurate ones have often been neglected, due to the rarity in nature and the assumption of suppressed coherent interlayer movement of electrons. How the interlayer interaction affects the electronic s...

The interlayer coupling can be used to engineer the electronic structure of van der Waals heterostructures (superlattices) to obtain properties that are not possible in a single material. So far research in heterostructures has been focused on commensurate superlattices with a long-ranged Moir\'e period. Incommensurate heterostructures with rotatio...

Growing additional TiO2 thin films on TiO2 substrates in ultrahigh vacuum (UHV)-compatible chambers have many applications for sample preparation, such as smoothing surface morphologies, templating, and covering impurities. However, there has been little study into how to control the morphology of TiO2 films deposited onto TiO2 substrates, especial...

Recently, commercially available copper foil has become an efficient and inexpensive catalytic substrate for scalable growth of large-area graphene films for fundamental research and applications. Interestingly, despite its hexagonal honeycomb lattice, graphene can be grown into large aligned square-shaped sheets on copper foils. Here, by applying...

WSe2 thin films grown by chemical vapor deposition on graphene on SiC(0001) are investigated using photoelectron spectro-microscopy and electron diffraction. By tuning the growth conditions, micron-sized single or multilayer WSe2 crystalline islands preferentially aligned with the main crystallographic directions of the substrate are obtained. Our...

Stannous selenide is a layered semiconductor that is a polar analogue of black phosphorus, and of great interest as a thermoelectric material. Unusually, hole doped SnSe supports a large Seebeck coefficient at high conductivity, which has not been explained to date. Angle resolved photo-emission spectroscopy, optical reflection spectroscopy and mag...

New synthesis routes to tailor graphene properties by controlling the concentration and chemical configuration of dopants show great promise. Herein we report the direct reproducible synthesis of 2-3% nitrogen-doped 'few-layer' graphene from a solid state nitrogen carbide a-C:N source synthesized by femtosecond pulsed laser ablation. Analytical inv...

The experimental mapping of the band structure of TiS3(001), by momentum resolution nanospot angle resolved photoemission, is presented. The experimental band structure, derived from angle-resolved photoemission, confirms that the top of the valence band is at the center of the Brillouin zone. This trichalcogenide has a rectangular surface Brilloui...

Stannous selenide is a layered semiconductor that is a polar analog of black phosphorus and of great interest as a thermoelectric material. Unusually, hole doped SnSe supports a large Seebeck coefficient at high conductivity, which has not been explained to date. Angle-resolved photoemission spectroscopy, optical reflection spectroscopy, and magnet...

The topology of Weyl semimetals requires the existence of unique surface states. Surface states have been visualized in spectroscopy measurements, but their connection to the topological character of the material remains largely unexplored. 1T'-MoTe2, presents a unique opportunity to study this connection. This material undergoes a phase transition...

Van der Waals heterostructures—vertical stacks of layered materials—offer new opportunities for novel quantum phenomena which are absent in their constituent components. Here we report the emergence of polaron quasiparticles at the interface of graphene/hexagonal boron nitride (h-BN) heterostructures. Using nanospot angle-resolved photoemission spe...

The topology of Weyl semimetals requires the existence of unique surface states. Surface states have been visualized in spectroscopy measurements, but their connection to the topological character of the material remains largely unexplored. 1T'-MoTe2, presents a unique opportunity to study this connection. This material undergoes a phase transition...

Dans le cadre de ses missions de centre national de production et d’exploitation de lumière synchrotron au service de la recherche et de l’industrie, le Synchrotron SOLEIL a progressivement développé depuis son début d’activité en janvier 2008 une offre complète d’équipements, de compétences et de services en direction des industriels du secteur co...

Precise safety testing and assessment of cosmetic ingredients in particular nanoparticles has remained a challenge in regard to development of alternative more efficient trial methods. In effect, validating alternative non-conventional methods is still an active undergoing field particularly in the area of the skin and eye irritation. After long in...

Application of a protective coating is the most widely used conservation treatment for outdoor bronzes (cast Cu-Sn-Zn-Pb-Sb alloys). However, improving coating protectiveness requires detailed knowledge of the coating/substrate chemical bonding. This is particularly the case for 3-mercapto-propyl-trimethoxy-silane (PropS-SH) applied on bronze, exhi...

Indeed, this summer the activity of the ANTARES beamline of SOLEIL on the field of the Angle Resolved Photoemission Spectroscopy with nanometric lateral resolution (nanoARPES) will be presented as an invited talk at the Symposium «Carbonhagen 2017», the 8th symposium on two-dimensional materials, at Copenhague, on August 16 to 17 this year. This sy...

Attempts to induce a clean and stabilized gap in the excitation spectrum of graphene, or a robust magnetism preserving a high carrier mobility have not been successful yet. An alternative procedure to achieve an optical gap and a magnetic state in graphene is to explore correlated states in flat electronic bands hosted by multilayer graphene with r...