Atomic and chemical structure of interfaces and defect cores in functional oxide nanostructures and films
Controlling interfacial and defect core structures at the atomic scale in epitaxial self-assembled oxide nanostructures and thin films constitutes a cornerstone to the realization of novel functionalities. We invite interested candidates to join our ongoing research, focusing on the correlation of the atomic and electronic structure of self-assembled nanostructures, thin films and interfaces with their functional properties. The successful candidate will exploit state of the art transmission electron microscopy and spectroscopy techniques. We offer an attractive interdisciplinary environment ideal to get introduced in all those aspects related with the generation, manipulation and evaluation of functional nanostructures.
Bioinspired Magnetic Nanodevices
Electronic devices based on digital processing have completely changed our lives. We have witnessed miniaturization and improving performances since the invention of the electronic transistor in the mid past century. However, this wonderful progress has physical restrictions in energy dissipation and emerging quantum phenomena. A suggestion for a paradigm change is the use of spintronics—that considers the intrinsic spin of electrons and the corresponding magnetic moment—as an alternative to conventional electronics. Recent developments in spintronics have shown that spin excitations (spin waves) such as skyrmions or vortices have topological properties that might lead to new applications.
This thesis project proposes to study spin excitations in materials and the implementation of computing strategies using nanostructures and metamaterials (materials that have been structures artificially). The aim is to develop functional magnetic nanodevices that work at low power by using electric fields (or strain) and light instead of currents and magnetic fields. Examples of the proposed functionalities include computing with waves and delays, pattern recognition based on synchronization, or memories based on phase differences among oscillators (phase coding).
Constriction of proteins and enzymes with electroactive surface binding metallacarboranes for bioelectronic materials
Proteins and enzymes have dimensions within the nanoscale. In the body, inside the cell, they perform in many cases as molecular electronic components. Performing as such in the body is possible because when they age which can be a matter of minutes or hours the body substitutes them. This is not possible "outside" the body because no mechanism will be available to refresh the spoiled protein. In this PhD work we propose to study the coating of the protein/enzyme with electroactive and aminoacid binding metallacarboranes through B-H•••H-N and C-H•••N interactions so to constrict the proteins in this protective coating for long performance as bioelectronic materials.
Detectores de radiación criogénicos para astrofísica
Los sensores de transición abrupta (TES) son termómetros superconductores ultrasensibles que operan a muy baja temperatura (T<100mK). Cuando se combinan con un absorbente adecuado, se convierten en detectores de radiación de sensibilidad extraordinaria, muy prometedores para muchas aplicaciones desde astronomía a industria.
Buscamos estudiantes muy motivados para realizar una tesis dedicada a la caracterización criogénica y el modelado electrotérmico de detectores TES de rayos X en el seno de un grupo que desarrolla un prototipo para ATHENA, el próximo telescopio de rayos X de la Agencia Europea del Espacio (ESA).
Dynamical modulation of electron spins with microwaves
At present, most of the digital information is stored in nonvolatile magnetic bits, e.g., in the hard disk drives of PCs and laptops, while data is processed in volatile memory units -e.g., in CPUs-. In order to extend the advantages of nonvolatility to processing units (i.e., adding to them the capability of permanent storage), efficient ways of manipulating the magnetism with electric currents are intensively researched, so that the information encoded in the magnetic bits (viz. with spins in up/down states) can be changed dynamically with electric pulses. In addition, over the past few years, the scientists have realized that some magnetic nanostructures (for instance, Pt/Co stacks) can host topological spin states (e.g. skyrmions), with a vast potential for new applications. With this foreground in view, we propose to modulate the magnetism of magnetic nanodevices using surface acoustic waves controlled by microwave (w) pulse fields, in the technological relevant range of the GHz, where most telecommunication applications work (e.g., cell phones, RFIDs, Wifi, etc.).
Engineering brain-like neurons and synapse with ferroelectrics
Emulating brain operation in advanced computing is currently a major axis of research. Key features of brain are learning and performing large scale computing. When trying to mimic this functioning using conventional memory element, involving two (and-only-two) well defied states, severe difficulties arise as this is not the way brain functions. Instead, brain circuitry is essentially adaptive, meaning that in-put and out-put parameters are not prefixed but can be modulated, among others, by previous actions. In brain this activity is performed by plastic synapses between neurons. It has been recently shown that ferroelectric tunnel devices, built to constitute ferroelectric memories, have the key ingredients for perform neuron-like functions and it has been claimed that memories can be built and designed to mimic some learning aspects on neuronal networks. In essence, this property results from the continuous multi-memory states than can be obtained in ferroelectric tunnel junctions by appropriate modulation of the amplitude (strength) of the writing signal (in-put signal) and the witting time (its duration) and the history (the starting state when writing. Within this project we aim at contributing to this challenging objective by grow and fabricate thin nanometric ferroelectric tunnel junctions and testing their functional/learning ability. We intend to develop suitable materials and methods for testing single junctions (neuron-like elements) as well study the mutual interaction among interconnected very simple memory ensembles.
Enhancing redox reactions in metal-air batteries
Metal-air batteries are being intensively studied to overcome the cost and energy limitations of current Li-ion batteries for large scale applications such as electric vehicles and grid storage.
This work aims to improve limitations in kinetics and reliability of these novel systems by the use of soluble catalytic molecules and particles. Tasks will include the preparation and characterization of electrodes and electrolyte additives, development of cells and study by multiple electrochemical techniques
Epitaxial ferroelectric oxide thin films with tailored lattice strain
Properties of ferroelectric oxide films, particularly the polarization, depend largely on the lattice strain. In the last years significant improvement has been achieved by growing the films on specific substrates that increased the strain of the films. However, this “strain engineering” presents important limitations due to the moderate strain level that can be achieved and the thickness restriction due to the plastic relaxation. The first objective of this thesis project is developing alternative methods to increase the strain level and the critical thickness in ferroelectric oxide films. For this purpose we will use epitaxial nanocomposite films containing a minority secondary oxide phase, either as ultrathin (in the nm range) 2D layers or as vertical 1D nanostructures, distributed in a ferroelectric BaTiO3 layer. The research of these methods, already proved very efficient for some functional oxides, is still incipient for ferroelectric materials.
On the other hand, ferroelectric polarization can be also increased by proper strain gradients. The effect, called flexoelectricity and initially considered very low, is today demonstrated to be very large for large permittivity materials under high lattice strain. Until now, the strain gradients occurring inherently in films partially relaxed, or around domain boundaries, have resulted in significant flexoelectric coefficients. But high ferroelectric polarization by flexoelectricity requires engineer high strain gradients in thin films. This is the second objective of the thesis: creating high strain gradients in ferroelectric BaTiO3 films. The films will be grown by pulsed laser deposition, a highly energetic technique that can cause high residual stress in the films. The strategy to create strain gradients, of high magnitude and distributed as designed, will be based on in situ changes of the growth kinetics during the pulsed laser deposition of BaTiO3 films.
Hybrid Magnetic-Superconducting devices for “green” Memory Applications
We are entering in the era of “Big data” with huge amount of information that needs to be stored and processed in unsustainable large-scale data centres and supercomputing systems. The challenge ahead is a revolution with energy-efficient technologies, able to reduce the related environmental and economic impacts. With this project we propose to explore a revolutionary concept of hybrid ferromagnetic-superconducting systems, which will be exploited in the production of “green” memory devices .
 Palau et al. Adv. Sci. (2016)
Icosahedral boron clusters: a perfect tool for the enhancement of polymer features
Developing Conducting Organic Polymers (COPs) of PPy, PEDOT and PPV doped with metallacarboranes either linked or free to the backbone polymer chain, with the aim to produce highly conducting and optically active materials particularly stable to the degradation by radical species.compounds to be investigated for diverse medicinal applications ranging from therapies to biomaterials and sensors/biosensors will be investigated during the PhD thesis. This thesis’ objectives are based on previous goals into the group that can be widespreaded in my recent review Chem. Soc. Rev., 2016, 45, 5147-5173. The candidate should be a talented chemist enjoying synthetic chemistry that will cooperate with biologists and physicians.
Laser synthesis of hybrid nanocarbon-based materials for energy and environmental applications
The student will join the Laser Processing Research group and will carry out the laser-induced chemical transformation of compounds based on carbon nanotubes, graphene and transition metal oxide nanostructures for the development of energy and environmental devices (supercapacitors, photocatalytic systems). The research will comprise the synthesis of different types of hybrid nanocarbon-based materials, their structural-compositional characterization and also the study of the materials’ functional properties.
Novel multiferroic oxides with enhanced coupling
PhD project in experimental condensed matter (appropriated profiles: chemistry, physics, nanoscience). The recent discovery of a new class of materials (type-II multiferroics) in which the magnetic and electric properties are strongly coupled is attracting very much interest because of the possibility to manipulate magnetism by electric fields and vice-versa, to magnetically control ferroelectric states. Along with its technological functionalities, multiferroics are also of great interest in fundamental research into strongly correlated oxides and quantum matter. This thesis project aims to synthesize, fabricate and characterize novel multiferroics and magnetoelectric transition metal oxides in the form of single crystals, thin films or powders. New crystal preparation facilities (based on optical furnaces) recently implemented at ICMAB will be used in addition to more typical methods of preparation (solid state reaction, pulsed-laser-deposition,..). Among other more conventional techniques of characterization, the new materials require and will be intensively investigated using synchrotron x-ray and neutron techniques in the best european sources. Our group is pioneer in applying new crystallographic methods of data analysis to tackle the study of the original magnetic, electronic and structural orders that govern the fascinating and exotic properties of this new class of materials, of importance for communications and energy nanotechnologies.
Perovskite oxynitrides with new electronic properties
The differences in polarizability, electronegativity and anion charge of nitrogen and oxygen induce changes in the properties of oxides by nitrogen introduction, and oxynitrides constitute an emerging group of new materials. In this project we aim to design, synthesize and characterize new transition metal perovskite oxynitrides to investigate the effect of nitride on the electrical and magnetic properties. The student will train in synthetic methods of solids, in the structural characterization by diffraction methods and in the study of physical properties of materials.
Porous Carborane-containing Metal Organic Frameworks for Energy and Environmental Applications
The PhD work will seek to correlate structural features with physical properties and to design synthetic methods to prepare porous and functional Metal-Organic Frameworks (MOF) and to tune their structures and properties. Unprecedented carborane-based building blocks will be synthesized and combined with suitable transition metals to provide MOFs and then use a wide variety of techniques to study their structure and properties with emphasis in energy and environmental applications.
Thermal rectification in semiconducting nanowires
The goal of this project is providing a theoretical framework aimed at understanding and controlling heat flux within semiconducting nanowires. The student will perform quantum numerical simulations in order to devise realistic approaches for the engineering of a nanoscale thermal diode, the fundamental building block of phononics. Nanowires present multiple advantages over bulk materials to achieve heat rectification, mostly due to their reduced dimensionality and to the flexibility given by the chemistry of growth to yield structures that appear to be suited for these applications.
Tuning of the electronic structure in High Temperature Superconducting films at nanometric scale
In this project we will study the reversible modulation of the carrier density induced in YBa2Cu3O7-δ (YBCO) films by means of electric field, “resistive switching (RS) effect”. We will evaluate new opportunities to induce switchable manipulation of flux quanta for novel devices in digital applications. The potentiality of nano-engineering the doping level in YBCO films will also be undertaken to investigate on novel concepts and devices minimizing energy consumption.
Two-dimensional organic hybrid structures for artificial photosynthesis
The emergence of nanomaterials as new building blocks to construct light energy harvesting assemblies has opened up new ways to utilize renewable energy sources. This project focuses on the exploration of novel two-dimensional heterostructures based on organic assemblies and graphene with potential application in photocatalysis and artificial photosynthesis. Scanning tunneling microscopy and frequency modulation atomic force microscopy (STM/nc-AFM) in ultra-high vacuum will be employed to investigate the atomic scale structure of the heterostructures
Use of supercritical fluid technology for the preparation of nanostructured metal organic frameworks
The project develops sustainable methods for the synthesis of highly microporous materials, constituted by a metal and an organic framework (MOF). The nanostructure is controlled through the experimental conditions achieved in high pressure reactors. Exclusively, the green supercritical CO2 is used as a solvent. ZIF-8 is the target microporous substrate. Aside, the objective is to developed nanoMOFs with similar structures, but with metal centers adequate in applications of magnetic resonance imaging for biomedical applications.
Using high pressure to unravel the physics of unconventional thermoelectric materials
The popular use of high pressure in material science arises from the fact that a variation of the lattice constant has large impact on structural, vibrational, electronic, and optical properties of the material. Thermoelectricity (TE) is being increasingly considered as renewable-energy alternative, particularly, for stand-alone, energy-harvesting applications. Hybrid halide perovskites and layered dichalcogenides (MoS2, WS2, etc.) are important in photovoltaics and spintronics, respectively, but their suitability for TE applications remains unexplored. The project aims at: 1) Use pressure to investigate the interplay between organic molecules and inorganic perovskite cage to boost TE properties by decoupling electron and heat transport in hybrid perovskites. 2) Tailor with pressure the electronic structure of few-layers dichalcogenides, to enhance our understanding of the Seebeck/Peltier effects in systems with the peculiar electronic structure of topological insulators, possibly leading to a new generation of nanoscale TE devices.