Research

Friday, 15 January 2016

Severo Ochoa Program

ICN2 Severo Ochoa Award: Nanodevices for Social Challenges

The research developed at ICN2 has a big impact on fields such as life sciences (medicine, health, and environment), energy and information and communication technologies. This is for sure one of the reasons why the Spanish Ministry of Economy and Competitiveness acknowledged the Institute in 2014 as a Severo Ochoa Excellence Center. This Program recognizes the excellence of the scientific contributions of centers, their potential industrial and social impact and their potential for talent attraction. In the last five years, only 21 research centers have been awarded.

The funding provided by the Severo Ochoa award, one million € per year during four years, will focus in the ICN2 Program on "Nanodevices for Social Challenges". This award is largely devoted to the recruitment of staff and the procurement of equipment to support the development of research projects.

Cross-Disciplinary Approaches

The ICN2 Program on "Nanodevices for Social Challenges" is based on four transversal methodological approaches:

  • Growth and synthesis of nanomaterials
    Expertise in growth of thin films, PLD, CVD, ALD, etc. with a broad range of materials, including graphene, metal and multiple component oxides.
  • Nanofabrication
    Expertise in both bottom-up and top-down fabrication, including self-assembly, nanoparticle synthesis, corrosive etching, supramolecular chemistry, screenprinting, nanoimprint lithography, roll-to-roll lithography on flexible substrates, inkjet printing, and rapid prototyping.
  • Characterisation and metrology
    World-class expertise in a very broad range of characterization techniques, some of them developed by ICN2 researchers. Experience in nanometrology includes two patent applications, and the plan to establish a dedicated industrial Nanometrology centre with private partners.
  • Theory and simulation
    Expertise includes pioneering developments of tools for atomistic simulations of matter, including electronic and thermal processes in nanodevices, and the structure and properties of nanomaterials.

Research Areas

The Severo Ochoa program research will produce specific applications and devices which are able to reach the market, providing new solutions to major social challenges in the following areas:

  • Biosystems
    Expertise in optical and electrochemical biosensing, biofunctionalised inorganic nanoparticles, supramolecular chemistry, water-surface interactions and characterisation. Related activities include EU projects in point-of-care devices and biosensors, ERC in nanomaterials for diagnostics & therapy, commercialisation with numerous licensed patents and two spin-off companies (biosensing and drug delivery).
  • Energy
    Expertise in materials, capacitors and energy transfer, phononics and photonics, photovoltaics, piezoelectrics, nanofabrication of flexible substrates and thin-film materials, spectroscopy and characterisation, leadership positions in EU projects and platforms (Graphene Flagship, Photonics platform, ERC in piezoelectrics), collaborative prototyping with industry in next generation photovoltaics, roll-to-roll lithography, and inks for active layers.
  • Information technology and telecommunications
    Expertise in materials, spintronics, magnetism, graphene, topological isolators, photonics, phononics and heat transfer, nanodevice fabrication and characterisation.

In 2009, the EU identified KETs for their potential impact in strengthening Europe's industrial and innovation capacity. Six KETs were highlighted as key for European sustainable growth: Nanotechnology; Micro- and Nano-electronics; Advanced Materials; Photonics; Industrial Biotechnology; and, Advanced Manufacturing. In this context the relevance of the ICN2 Program on "Nanodevices for Social Challenges" is evident, as it involves virtually all the six KETs.

Beyond research

In addition to the scientific cross-disciplinary goals, ICN2 will carry out a comprehensive recruiting and training programme aimed at attracting and developing the professional careers of talented senior and junior researchers associated with the Severo Ochoa Programme (PhD programme; Postdoctoral programme; Visitors programme; ICN2- User Programme Training; Academia Intern Programme; and workshops and seminars). It also includes other ambitious actions such as the creation of a specific Gender action plan and international knowledge dissemination and outreach activities.

An external Scientific and Industrial Advisory Committee (SIAC), appointed by the Director with the advice of the ICN2 Scientific Advisory Board, advises on strategic directions and the progress of the project. The work plan is divided into seven Work Packages, one per Application Area and Cross-Disciplinary Activity. Overall management is carried out by the Project Management Committee, which is formed by one representative of each WP, plus two additional members to follow up dissemination and technology transfer activities.

The Severo Ochoa Community

This award is the highest recognition of centers of excellence in Spain, and it is granted after international scientific committees carry out a rigorous evaluation of project proposals submitted by Spanish research centers.

The following institutes have received the Severo Ochoa Excellence award:

Sunday, 20 September 2015

Theory and Simulation Group

Main Research Lines

  • Development of theoretical methods, numerical algorithms and simulation tools
  • Codes: SIESTA and TRANSIESTA
  • First-principles simulations at the nanoscale
  • Novel physical properties in 2D materials

Most of the research carried out by the group in 2016 has gravitated around the MaX Centre (www.max-centre.eu), one of the eight European Centres of Excellence in HPC Applications supported by the EU under its 2105 H2020 e-infrastructure funding programme. 

MaX supports developers and end users of advanced applications for materials simulations, design and discovery, and works at the frontiers of current and future high performance computing (HPC) technologies. It brings together leading developers and users of materials applications, together with top experts in HPC. It is based on the collaboration of 13 teams, including five research groups, like the ICN2 Theory and Simulation Group, which will focus on enhancing the capabilities of the SIESTA package and develop new methodologies for industrial applications of simulation tools in materials science.

Considerable effort has been devoted to improve the modularity and efficiency of the SIESTA and TRANSIESTA codes. The first release of the SIESTA code under a GPL license at the beginning of the year  was an important milestone in 2016, as was the TranSiesta/TBTrans School organised at the ICN2, which was a great opportunity to present some major recent developments in the tools developed by the group. The release of the spin-orbit implementation and a first operative version of the Density Functional Perturbation Theory within the code are also among the group’s achievements in 2016.

The group has continued its participation in NFFAEurope (www.nffa.eu), a project funded under the H2020-INFRAIA-2014-2015 call “Integrating and opening existing national and regional research infrastructures of European interest”. The NFFA (Nanoscience Foundries and Fine Analysis) is a platform for interdisciplinary research at the nanoscale, in which the Theory and Simulation Group participates as an “installation” offering access to computational support for experimental user projects.

On the science side of things, in 2016 we made progress along two new important research lines:

Thermal transport at the nanoscale: Taking advantage of the expertise of visiting Professor Colombo on thermal transport at the nanoscale, and coordinated with theoretical and experimental collaborators, the group has moved forward in this exciting topic, developing new tools and methodologies. In particular, we are exploring the thermal transport properties of 2D materials, which have revealed unusual behaviours (as compared to bulk systems), leading to unexpected intriguing features with significant potential for various front-edge and emerging nanotechnologies (e.g. heat management in nanodevices, thermoelectric energy conversion or the manipulation of lattice heat to engineer phononic devices). Within the MaX Centre, and in the context of an industrial collaboration, we have also focused on techniques to study thermal properties in nanofluids, which potential impact on energy storage.

Magnetic properties at the nanoscale, with new developments in SIESTA that make the study of systems with strong spin-orbit effects (including topological insulators) possible, as well as the study of magnetic anisotropies in thin films and other nanostructured materials. We have used the working versions in our study of hybrid organic-inorganic perovskites, layered graphene-based magnetic nanostructures and topological insulators. These materials are very promising in the development of spin-based applications, which are of great interest at the ICN2 as a whole. 

With respect to the existing research lines, we have made strong advances on:

Understanding the properties of 2D materials: Vertical stacks of transition metal dichalcogenides; grain boundaries and 1D polar discontinuities; graphene-based devices for DNA sequencing; and insights in the superconducting transition from STM experiments are all examples of our activities in 2D materials during 2016. 

Understanding nanostructured oxides: In collaboration with experimental colleagues in Argentina, we studied the mechanisms contributing to oxygen reduction reactions in manganites (La(1-x)SrxMnO3), identifying an increased oxygen vacancy concentration close to the surfaces that causes significant ionic conduction and enables the use of these nanostructured materials in solid oxide fuel cells in the “intermediate” temperature range. In addition to this collaboration, and motivated by the MaX Centre, we have established a new research collaboration with industry to advance oxygen diffusion in materials for sensor applications, which will run over the coming years.

 

Wednesday, 09 September 2015

Research

ICN2 is a renowned research centre. Its research lines focus on the newly discovered physical and chemical properties that arise from the fascinating behaviour of matter at the nanoscale. Recent discoveries in nanoscience may lead to a change of paradigm in important areas such as medicine, energy, or microelectronics. The frontier research developed at ICN2 has enormous potential to change everyday life.

Nanoimprint Lithography Platform

Sunday, 20 September 2015

Theoretical and Computational Nanoscience Group

Main Research Lines

  • Leading-edge theoretical research on quantum transport phenomena in graphene
  • Spin dynamics in Dirac matter (graphene, topological insulators)
  • Thermal properties and thermoelectricity in 2D materials
  • Predictive modelling and multiscale numerical simulation of complex nanomaterials and quantum nanodevices

1) Spin Manipulation in Graphene by Chemically-Induced Sublattice Pseudospin Polarisation

Spin manipulation is one of the most critical challenges to realising spin-based logic devices and spintronic circuits. Graphene has been heralded as an ideal material to achieve spin manipulation, but so far new paradigms and demonstrators are limited. We have shown that certain impurities such as fluorine ad-atoms, which locally break sublattice symmetry without the formation of strong magnetic moments, could result in a remarkable variability of spin transport characteristics.

In 2014 our group discovered a novel spin relaxation mechanism in non-magnetic graphene samples connected to the unique spin-pseudospin entanglement occurring near the Dirac point. Such a finding has inspired new directions towards the control of the spin degree of freedom modifying the pseudospin or vice versa. In 2016 we have shown how a chemical functionalisation of graphene with certain types of ad-atoms such as fluorine, by breaking the sublattice symmetry and by inducing a SOC without the formation of strong magnetic moment, could provide an innovative technique to monitor spin transport properties for spintronic applications. Our theory also allows current experimental controversies to be revisited and brings an enabling building block for graphene spintronics.

2) Spin Hall effect in decorated graphene

Although graphene has attractive properties in spintronics, such as long room temperature spin diffusion length, it is inactive for the spin Hall effect (SHE), a spin transport phenomenon mediated by strong spin-orbit coupling in which opposite spins are deviated in contrary directions while propagating inside a channel. Several experiments reporting an unexpectedly large SHE in graphene decorated with ad-atoms, locally enhancing the spin-orbit coupling effects in graphene, have raised fierce controversy. Indeed to date, measured values for the spin Hall angle range from 0.0001  in semiconductors to 0.3 in some metals, which are finding important applications in the magnetic memory market. The measurements on decorated graphene indicate a spin Hall angle of about 0.2, which would make modified graphene technologically relevant.

We developed a fully quantum simulation of this phenomenon to analyse such intriguing experimental results and found that multiple background contributions to non-local resistance, which was argued to be the smoking gun of SHE, could resolve these controversies. A novel device geometry to suppress these contributions and quantify the upper limit for the SHE in 2-dimensional materials has been also proposed. Such results are opening new directions for experiments in this field and give some hope for the efficient engineering of the spin Hall effect in graphene-based materials.

3) Simulation CVD graphene devices 

Major roadblocks towards high-performance graphene devices are the nanoscale variations of graphene polycrystalline morphologies (grain boundaries, grain sizes), which strongly impact on all macroscopic physical properties (mechanical, electrical and thermal). The requirements in terms of device quality and uniformity are very demanding, and major roadblocks to the high-performance of many graphene devices stem from the complex structural morphologies of large-scale graphene (CVD, reduced graphene oxides, etc.), which are detrimental to their optimal macroscopic properties. 

We have clarified the impact of edges and grain boundaries on a large spectrum of properties, including charge mobility, Seebeck coefficient thermal conductivity and the thermoelectric figure of merit of CVD graphene. In particular we have reported on the scaling properties of polycrystalline graphene and hybrid graphene/hBN heterostructures, providing guidance for the optimisation of materials for a desired application.

4 Spin lifetime in ultraclean graphene devices 

We have clarified theoretically the fundamental properties of spin dynamics in ultraclean spin-orbit-coupled materials, by considering the quasiballistic limit, and introducing small broadening of electronic states due to thermal effects or electrical bias. In the ballistic limit, the spin lifetime was demonstrated to be dictated by dephasing effects arising from energy broadening plus a non-uniform spin precession, which is very unique to Dirac materials such as graphene and topological insulators. For the case of clean graphene, we find a strong anisotropy with spin lifetimes that can be short even for modest energy scales, on the order of a few nanoseconds. These results offer deeper insight into the nature of spin dynamics in graphene, and are also applicable to the investigation of other systems where spin-orbit coupling plays an important role.