Halle/Saale, Germany

The Max Planck Institute of Microstructure Physics at Halle is a research institute in Germany in the field of material research. It was founded in 1992 as a follow up of the Academy of Science Institute of Solid State Physics and Electron Microscopy and moved into the new buildings between 1997 and 1999. It is one of 80 institutes in the Max Planck Society .The institute has three main departments:The Theory Department, headed by Prof. Eberhard Gross, mainly carries out theoretical research on the electronic, magnetic, optical, and electrical properties of micro- and nanostructured solid-state systems'.The Experimental Department 1, headed by Prof. Jürgen Kirschner, mainly deals with the magnetic properties of dimensionally reduced systems and their dependence on electronic structure, crystalline structure and morphology.The Experimental Department 2, headed by Prof. Ulrich Gösele, is focussed on the scientific understanding, design and fabrication of new materials for information, communication, engineering as well as bio-technological applications.↑ ↑ ↑ Wikipedia.

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News Article | April 17, 2017
Site: www.pressat.co.uk

Cutting-edge electronics research in the UK has received a huge boost, thanks to grants for the University of Warwick – totalling almost £1.75 million – from the Engineering and Physical Sciences Research Council (EPSRC). Professor Marin Alexe in the Department of Physics has been awarded grants for two research projects in the field of ferroelectricity – which may lead to breakthroughs in nanotechnology, and memory storage in everyday devices. One project, ‘Ferrotoroidic structures: polar flux-closure, vortices and skyrmions’, will develop a fundamental, new understanding of ferroelectrics systems – materials which are used in smart phones and TVs, watches, games consoles, and computers. The aim is to obtain and analyse the fundamental structural and functional properties of polar ferrotoroidic oxides based on the perovskite structure. The knowledge acquired from this project could be used to develop the next generation of memory devices and cognitive computing – revolutionising the fields of data processing and secure communications. Professor Alexe is the Principal Investigator on this project, with Dr Ana Sanchez as Co-Investigator. The EPSRC award for this project is is £998k. Another programme, ‘Ferroelectric, ferroelastic, and multiferroic domain walls: a new horizon in functional materials’, will focus on exploring the novel functionally of active ferroelectric, ferroelastic and multiferroic domain walls (DW). The project is highly important for the electronics industry – the research could unlock the potential of DW technology as a viable technology for microelectronics and progress the development of functional nanodevices. Working alongside Queen’s University Belfast, and the universities of Cambridge and St Andrews, Warwick receives £730k for this project. Prof Marin Alexe recently joined Warwick’s Department of Physics as Chair of Functional Materials, after spending 18 years at the Max Planck Institute of Microstructure Physics-Halle. His research interests include the physics and engineering of complex oxide thins films for information technology, and the integration of functional materials for oxide electronics. He is one of the pioneers of nano-ferroelectrics, with several contributions in high impact journals such as Science, Nature Materials and Communications. Prof Alexe was recently awarded the Wolfson Research Merit Award and the Theo Murphy Blue Sky Award of The Royal Society. He comments: “This represents an excellent opportunity to bring UK at the forefront of research in this exiting field of oxide functional materials and electronics.” Professor Pam Thomas is Warwick’s Pro Vice-Chancellor for Research, and Professor of Physics. She comments: "I'm very pleased to see this important area of materials research being funded in this way. “Through Professor Alexe's research together with Dr Sanchez and his other coinvestigators, Warwick's combination of expertise and excellent research infrastructure together with EPSRCs support, is poised to make a real difference in the world of electronic materials." The University of Warwick is one of the top 10 research environments in the UK for Physics, as assessed by REF 2014, with all aspects considered to be either world-leading or internationally excellent. 96% of the research papers submitted to REF 2014 were judged to be at least "internationally excellent" and a quarter "world leading" (4*). 'Energy' is one of the University of Warwick’s Global Research Priorities. The University is addressing global challenges through its world-class multi-disciplinary research.

Profeta G.,University of L'Aquila | Profeta G.,Max Planck Institute of Microstructure Physics | Calandra M.,French National Center for Scientific Research | Mauri F.,French National Center for Scientific Research
Nature Physics | Year: 2012

Graphene is the physical realization of many fundamental concepts and phenomena in solid-state physics. However, in the list of graphene's many remarkable properties, superconductivity is notably absent. If it were possible to find a way to induce superconductivity, it could improve the performance and enable more efficient integration of a variety of promising device concepts including nanoscale superconducting quantum interference devices, single-electron superconductor-quantum dot devices, nanometre-scale superconducting transistors and cryogenic solid-state coolers. To this end, we explore the possibility of inducing superconductivity in a graphene sheet by doping its surface with alkaline metal adatoms, in a manner analogous to which superconductivity is induced in graphite intercalated compounds (GICs). As for GICs, we find that the electrical characteristics of graphene are sensitive to the species of adatom used. However, contrary to what happens in GICs, Li-covered graphene is superconducting at a much higher temperature with respect to Ca-covered graphene. © 2012 Macmillan Publishers Limited. All rights reserved.

Schmidt V.,Max Planck Institute of Microstructure Physics | Wittemann J.V.,Max Planck Institute of Microstructure Physics | Gosele U.,Max Planck Institute of Microstructure Physics | Gosele U.,Duke University
Chemical Reviews | Year: 2010

Growth, thermodynamics, and electrical properties of silicon nanowires have been reported. The name vapor-liquid-solid (VLS) mechanism reflects the pathway of Si, which coming from the vapor phase diffuses through the liquid droplet and ends up as a solid Si wire. The VLS mechanism has numerous direct and indirect implications for Si wire growth. High temperature CVD Si wire growth experiments are often performed in tubular hot wall reactors. The VLS mechanism has several interesting implications for the thermodynamics of the wire growth. The diameter expansion at the wire base is one of these implications. a reduction of the ionization efficiency can be expected to have a major influence on the electric characteristics of the nanowires. The last major uncertainty for correlating resistivity with doping concentration is the charge carrier mobility. Charge carrier mobility depends on both dopant type and concentration.

Breitenstein O.,Max Planck Institute of Microstructure Physics
Solar Energy Materials and Solar Cells | Year: 2011

By evaluating dark lock-in thermography images taken at one reverse and three forward biases, images of all two-diode-parameters J01, J 02, n (ideality factor of J02), and Gp (the parallel Ohmic conductivity) of the dark currentvoltage characteristic are obtained. A local series resistance is explicitly considered and may be provided as a series resistance image, e.g. resulting from luminescence imaging. The results enable a separate investigation of factors influencing the depletion region recombination current and the diffusion current, which is governed by the bulk lifetime. Local IV characteristics of special sites may be simulated. © 2011 Elsevier B.V. All rights reserved.

Breitenstein O.,Max Planck Institute of Microstructure Physics
Solar Energy Materials and Solar Cells | Year: 2012

By evaluating four lock-in thermography images of a solar cell taken at four different biases and an independently measured series resistance image, images of all local two-diode parameters are obtained. Assuming the local validity of the two-diode model, this information enables the construction of local and global dark and illuminated characteristics and of realistic images of local solar cell parameters like efficiency, fill factor, and open circuit voltage with a good spatial resolution. Within this procedure, an injection-dependent lifetime may be regarded by assuming an ideality factor larger than unity for the diffusion current. The possibilities and limitations of this approach are discussed and selected results on a typical industrial multicrystalline cell are introduced. The proposed procedure is a valuable tool for judging which local defects are especially harmful for degrading the fill factor or the open circuit voltage, respectively, and extrapolating the properties of a cell where certain types of defects are excluded. A general limitation of this approach is that it assumes an individual but constant series resistance to each pixel, which neglects the distributed character of the series resistance. © 2012 Elsevier B.V. All rights reserved.

Zakeri K.,Max Planck Institute of Microstructure Physics
Physics Reports | Year: 2014

Elementary spin excitations (magnons) play a fundamental role in condensed matter physics, since many phenomena e.g.magnetic ordering, electrical (as well as heat) transport properties, ultrafast magnetization processes, and most importantly electron/spin dynamics can only be understood when these quasi-particles are taken into consideration. In addition to their fundamental importance, magnons may also be used for information processing in modern spintronics.Here the concept of spin excitations in ultrathin itinerant magnets is discussed and reviewed. Starting with a historical introduction, different classes of magnons are introduced. Different theoretical treatments of spin excitations in solids are outlined. Interaction of spin-polarized electrons with a magnetic surface is discussed. It is shown that, based on the quantum mechanical conservation rules, a magnon can only be excited when a minority electron is injected into the system. While the magnon creation process is forbidden by majority electrons, the magnon annihilation process is allowed instead. These fundamental quantum mechanical selection rules, together with the strong interaction of electrons with matter, make the spin-polarized electron spectroscopies as appropriate tools to excite and probe the elementary spin excitations in low-dimensional magnets e.g ultrathin films and nanostructures. The focus is put on the experimental results obtained by spin-polarized electron energy loss spectroscopy and spin-polarized inelastic tunneling spectroscopy. The magnon dispersion relation, lifetime, group and phase velocity measured using these approaches in various ultrathin magnets are discussed in detail. The differences and similarities with respect to the bulk excitations are addressed. The role of the temperature, atomic structure, number of atomic layers, lattice strain, electronic complexes and hybridization at the interfaces are outlined. A possibility of simultaneous probing of magnons and phonons in complex low-dimensional ferromagnetic oxide nanostructures is discussed. The influence of the relativistic spin-orbit coupling on high-energy magnons is addressed. It is shown how the spin-orbit coupling breaks the energy degeneracy of the magnons excited in an ultrathin ferromagnet, and how it influences their lifetime, amplitude, group and phase velocity. A potential application of these new effects in modern spintronics is outlined. It is illustrated how one can take advantage of collective nature of magnons and use these quasi-particles for probing the magnetic exchange interaction at buried interfaces. © 2014 Elsevier B.V.

Moutanabbir O.,Max Planck Institute of Microstructure Physics | Gosele U.,Max Planck Institute of Microstructure Physics
Annual Review of Materials Research | Year: 2010

The ability to tailor compound semiconductors and to integrate them onto foreign substrates can lead to superior or novel functionalities with a potential impact on various areas in electronics, optoelectronics, spintronics, biosensing, and photovoltaics. This review provides a brief description of different approaches to achieve this heterogeneous integration, with an emphasis on the ion-cut process, also known commercially as the Smart-Cut™ process. This process combines semiconductor wafer bonding and undercutting using defect engineering by light ion implantation. Bulk-quality heterostructures frequently unattainable by direct epitaxial growth can be produced, provided that a list of technical criteria is fulfilled, thus offering an additional degree of freedom in the design and fabrication of heterogeneous and flexible devices. Ion cutting is a generic process that can be employed to split and transfer fine monocrystalline layers from various crystals. Materials and engineering issues as well as our current understanding of the underlying physics involved in its application to cleaving thin layers from freestanding GaN, InP, and GaAs wafers are presented. © 2010 by Annual Reviews. All rights reserved.

Liu L.,Max Planck Institute of Microstructure Physics | Pippel E.,Max Planck Institute of Microstructure Physics
Angewandte Chemie - International Edition | Year: 2011

The title nanotubes were synthesized by template-assisted one-step electrodeposition and found to exhibit markedly enhanced electrocatalytic activity toward oxygen reduction, which can be attributed to a combination of several favorable factors: the multicomponent nature with which different elements work synergistically, the strain and electronic effects associated with surface dealloying, and their hollow and porous geometry. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pantel D.,Max Planck Institute of Microstructure Physics | Goetze S.,Max Planck Institute of Microstructure Physics | Hesse D.,Max Planck Institute of Microstructure Physics | Alexe M.,Max Planck Institute of Microstructure Physics
Nature Materials | Year: 2012

Spin-polarized transport in ferromagnetic tunnel junctions, characterized by tunnel magnetoresistance, has already been proven to have great potential for application in the field of spintronics and in magnetic random access memories. Until recently, in such a junction the insulating barrier played only a passive role, namely to facilitate electron tunnelling between the ferromagnetic electrodes. However, new possibilities emerged when ferroelectric materials were used for the insulating barrier, as these possess a permanent dielectric polarization switchable between two stable states. Adding to the two different magnetization alignments of the electrode, four non-volatile states are therefore possible in such multiferroic tunnel junctions. Here, we show that owing to the coupling between magnetization and ferroelectric polarization at the interface between the electrode and barrier of a multiferroic tunnel junction, the spin polarization of the tunnelling electrons can be reversibly and remanently inverted by switching the ferroelectric polarization of the barrier. Selecting the spin direction of the tunnelling electrons by short electric pulses in the nanosecond range rather than by an applied magnetic field enables new possibilities for spin control in spintronic devices. © 2012 Macmillan Publishers Limited. All rights reserved.

Carrier lifetime in photoelectric processes is the average time an excited carrier is free before recombining or trapping. Lifetime is directly related to defects and it is a key parameter in analyzing photovoltaic effects in semiconductors. We show here a scanning probe method combined with photoinduced current spectroscopy that allows mapping with nanoscale resolution of the generation and recombination lifetimes. Using this method we have analyzed the mechanism of the abnormal photovoltaic effect in multiferroic bismuth ferrite, BiFeO 3. We found that generation and recombination lifetimes in BiFeO 3 are large due to complex generation and recombination processes that involve shallow energy levels in the band gap. The domain walls do not play a major role in the photovoltaic mechanism. © 2012 American Chemical Society.

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