How It Works: SuperSTEM
The SuperSTEM facility and our very own Dr Demie Kepaptsoglou feature in the November issue (118) of the How it works magazine in a special on Small Science.
Revolutionising magnetic device and sensor technology: the discovery of a new exchange bias formation mechanism controllable at the nano-scale
Most magnetic devices in everyday electronics, including sensors, hard drive read-heads or magnetic random access memories (MRAMs) rely on the exchange bias effect, a magnetic interaction that couples a ferromagnetic and an antiferromagnetic material, resulting in a unidirectional displacement of the ferromagnetic hysteresis loop by an amount called the ‘exchange bias field’. In a breakthrough study, published in the journal Nature Materials, researchers from the Technical University of Madrid and the University of York have uncovered in collaboration with SuperSTEM a ground-breaking alternative process for the generation of the exchange bias field. This spontaneous process involves the direct control of minute structural defects in the antiferromagnetic part of the device, whose observation was only possible thanks to the capabilities of the SuperSTEM instruments. Uncovering this microscopic mechanism for establishing and controlling the exchange bias opens new pathways for the design of future magnetic devices.
Full paper: A. Migliorini, B. Kuerbanjiang, T. Huminiuc et al., “Spontaneous exchange bias formation driven by a structural phase transition in the antiferromagnetic material”, Nature Materials, 17, pp. 28–35 (2018).
For more details: https://doi.org/10.1038/nmat5030
Electron microscopy reveals fundamental properties of a technologically essential class of materials
The pyrochlore crystallographic structure is ubiquitous across materials domains, being studied in connection with everything from quantum magnetism, ferroelectricity, luminescence and catalysis to radioactive waste disposal. In each of these subfields, there have been for decades a set of “mysteries”: why is the observed magnetism so sensitive to changes in composition? Why are some compositions not ferroelectric?, etc… A wide-ranging collaboration involving researchers at the National Institute of Standards and Technology (NIST, Maryland, USA), Johns Hopkins University (Maryland, USA) and SuperSTEM reported in the journal Nature Communications how these mysteries have finally been solved, revealing the existence of a previously unappreciated structural flexibility in the pyrochlore structure, which leads to local complexity even in chemically perfect materials. By confirming the universality of these geometric effects and further demonstrating how the magniture of this local disortder can be controlled chemically, this ground-breaking research not only solves long-standing technological puzzles, but also opens new avenues for the chemical design of advanced materials.
Full paper: B.A. Trump, S.M. Koohpayeh, K.J.T. Livi et al., “Universal geometric frustration in pyrochlores”, Nature Communications, 9, 2619 (2018).
For more details: https://doi.org/10.1038/s41467-018-05033-7
Thank you all for a very successful Summer School!
Our 7th biennial Summer School on Advanced Topics on Electron Microscopy: Theory meets experiment, was held at the Sci-Tech Daresbury Campus between 28 June and 4 July 2018.
This year's event was co-organised with the Scientific Computing Department of the Science & Technology Facilities Council and CCP9, the Collaborative Computational Project for the Study of the Electronic Structure of Condensed Matter.
We were fortunate to host world renowned scientists, who delivered exciting & insightful lectures to a new generation of electron microscopy experts. In addition to the lectures, the participants had the opportunity to learn how to operate our instruments and try their hands on some advanced computational tools during 6 days of a densely packed scientific programme.
Our guests came from 21 different countries, including visitors from as far afield as Australia, Japan and Korea. We would like to thank ERSRC for their continuing support of the SuperSTEM facility, as well as their support to our events through our core funding and funding of CCP9.
The SuperSTEM Summer School was made possible in part through the generous support of the RMS, EMS, Nion Co. , Hitachi, Bruker, and STFC .
Science Advances: Exploring phonons in momentum space at the nanometer scale
Acoustic and optical phonons affect fundamental physical properties such as the conduction of sound and heat. A SuperSTEM-led team with invaluable contributions from collaborators at the University of Oxford, Royal Holloway University of London, RMIT University and Nion Company, has developed a novel momentum-resolved electron energy loss spectroscopy approach that makes it possible to study the dispersion of phonons in volumes of material up to 20 orders of magnitude smaller than was possible with other experimental techniques.
This could provide a way to understand how phonon propagation is affected by atomic-scale point or line defects, or even single atom dopants!
F.S. Hage, R.J. Nicholls, J.R. Yates et al. , Nanoscale momentum-resolved vibrational spectroscopy, Science Advances 4, eaar7495 (2018).
For more details: https://doi.org/10.1126/sciadv.aar7495
Last Call for Applications for the SuperSTEM Summer School 2018!
The preliminary program with details of the talks and speakers has been uploaded to the summer school's webpage! Note: There are now only a few places remaining for the 7th SuperSTEM Summer School 2018.
As the original closing date falls into the Easter break we decided to extend the application period until 9/4/2018.
29/6 - 4/7/2018
Application for the 7th SuperSTEM Summer School is open! Read more....
Launching in-situ heating & biasing experiments
We are excited to announce the commissioning of our Protochips Fusion holder for in-situ heating and biasing experiments in our SST3 Nion UltraSTEM instrument. The holder is available for user access via the usual process.
Special Issue of Micron on “The study of biological specimens, nanomaterials, and their dynamics using liquid-phase electron microscopy”
Professor Niels de Jonge (IMN in Saarbrücken – Germany) and SuperSTEM scientist Patricia Abellan are serving as the guest editors of an upcoming Special Issue of Micron on “The study of biological specimens, nanomaterials, and their dynamics using liquid-phase electron microscopy”.
This Special Issue of Micron aims to cover the present state of liquid-phase EM, and will examine the current challenges as well as future directions of the field. The manuscripts will cover both experimental- and theoretical efforts to enhance our understanding of all factors involved with electron microscopy in liquids.
A detailed description of this Special Issue and submission details can be found at the following website:
Unravelling the structure and chemistry of high capacity Li-battery materials
Modern society’s increasing demands for cleaner, safer, cheaper, and longer-lasting energy storage solutions are driving many industries to develop new and improved battery materials. This is particularly true in the automotive sector, where the electrochemical shortcomings that currently plague the implementation of high capacity materials s LMRTMOs as a viable long-term choice of lithium-ion battery cathode must be addressed urgently. One promising avenue consists in deviating from the widely studied high lithium/transition metal (Li/TM) ratio chemistries. However, almost no information is available on the effect of composition on the complex structure of the pristine, uncycled LMRTMOs.
Researchers from Lawrence Berkeley National Laboratory, in collaboration with Envia Systems and SuperSTEM address this long-standing issue in a recent publication in RSC Energy & Environmental Science.
A.K. Shukla, Q. M. Ramasse, C. Ophus, et al., Effect of composition on the structure of lithium- and manganese-rich transition metal oxides, RSC Energy and Environmental Science (2018)
For more details: https://dx.doi.org/10.1039/C7EE02443F
Managing dose-, damage- and data-rates in multi-frame spectrum-imaging
As an instrument, the scanning transmission electron microscope is unique in being able to simultaneously explore both local structural and chemical variations in materials at the atomic scale. This is made possible as both types of data are acquired serially, originating simultaneously from sample interactions with a sharply focused electron probe. Unfortunately, such scanned data can be distorted by environmental factors, though recently fast-scanned multi-frame imaging approaches have been shown to mitigate these effects.
In a recently published paper, result of a collaborative effort between the Universities of Oxford, Warwick, Manchester and SuperSTEM the same same approach is demonstrated for spectroscopic data.
L. Jones, A. Varambhia, R. Beanland, et al. , Managing dose-, damage- and data-rates in multi-frame spectrum-imaging, Microscopy (2018)
For more details: https://doi.org/10.1093/jmicro/dfx125
Understanding heterointerfaces in semiconductor nanowire devices
The functionality of nano-scaled electronic devices, based on III-V heterostructure nanowires, is extremely sensitive to the quality of the interfaces at the atomic scale. In a material system such as GaSb-InAs nanowires, where GaSb and InAs are intrinsic p-type and n-type semiconductors, respectively, the heterointerfaces act as p-n junctions in which atomic arrangement plays a crucial role. In the recently published paper, researchers from the University of Lund in collaboration with SuperSTEM investigate the radial and axial heterointerfaces of the GaSb-InAs nanowire system which is used as tunneling field-effect transistors (TFETs). We reveal the abruptness of the material transition at the radial heterointerface, in contrast to the axial one were interdiffusion occurs. This is of high importance in charge transport properties of the system. This work has been conducted in collaboration with NanoLund (Lund, Sweden), one of the worldwide leading consortia in the field of semiconductor nanowires. Cover art is accepted for the March 2018 issue of Nano Letters, which is one of the top-ranked journals in the field.
R. Zamani, F.S. Hage, S. Lehmann†, et al., Atomic-Resolution Spectrum Imaging of Semiconductor Nanowires, Nano Letters (2017)
For more details: https://dx.doi.org/10.1021/acs.nanolett.7b03929
SuperSTEM took to its soapbox to showcase science using art
SuperSTEM’s proposed topic “Below the surface of matter” was selected to be part of the first Soapbox Art & Science Leeds 2017 project, which took place on Friday 6th October. The engagement event was part of the annual free multi-arts and light festival Light Night Leeds 2017 in the University Quarter. SuperSTEM scientist Dr. Patricia Abellan took to her soapbox to showcase the relevance of plasmonics nanostructures in everyday life and the role of electron microscopy and of SuperSTEM within the scientific community. In order to bring the concepts of plasmonics and of nanotechnology to the general public, we worked together with visual artist and Doctor of Art History, Dr. Tatiana Abellan, from the Fine Arts Faculty at the University of Murcia, Spain. She created a set of lighted bottled coloured solutions and a series of videos that were projected inspired on the colloidal chemistry of plasmonic nanoparticles and a selection of SuperSTEM works on graphene and metallic structures. The Soapbox Art & Science project is supported by the Science and Technology Facilities Council and got great feedback and enthusiasm form audience members.
Soapbox Art & Science Leeds 2017: http://soapboxscience.org/2017-2/soapbox-art-science-leeds-2017/
Light Night Leeds 2017: https://whatson.leeds.gov.uk/lightnight
Meet our visual artist, Dr. Tatiana Abellan (University of Murcia, Spain): https://tatianaabellan.com/
New mechanism of spontaneous exchange bias formation revealed
Most of the magnetic devices in advanced electronics rely on the exchange bias effect, a magnetic interaction that couples aferromagnetic and an antiferromagnetic material, resulting in a unidirectional displacement of the ferromagnetic hysteresis loop by an amount called the ‘exchange bias field’. Setting and optimizing exchange bias involves cooling through the Néel temperature of the antiferromagnetic material in the presence of a magnetic field. In a recently published paper in Nature Materials, researchers from the Universidad Politécnica de Madrid, Universidad Autónoma de Madrid and the University of York in collaboration with SuperSTEM demonstrate an alternative process for the generation of exchange bias in IrMn/FeCo bilayers. The physical process for the generation of exchange bias is based on a room temperature spontaneous crystallization of the antiferomagnetic IrMn layer and is proposed as an alternative mechanism to standard thermal annealing. The possibility of controlling the direction of the exchange microscopically, and the large average grain size of the crystallized IrMn, are also interesting features for devices based on these structures or for further research on the microscopic behavior of the exchange bias.
A. Migliorini, B. Kuerbanjiang, T. Huminiuc, et al. Spontaneous exchange bias formation driven by a structural phase transition in the antiferromagnetic material, Nature Materials
More details: http://dx.doi.org/10.1038/NMAT5030
Breakthrough for nano-design of catalysts to combat air pollution
In the latest edition of the Nature Communications journal, long-standing SuperSTEM collaborator Stig Helveg shares scientific evidence that nano-designed titanium crystals can improve catalysts that reduce air pollution. The optimized titanium oxide crystals boost the reactivity of vanadium oxide in their vicinity. This discovery was made by the Haldor Topsoe-led team, including lead author Martin Ek, in collaboration with SuperSTEM’s Quentin Ramasse. This research is crucially important, because vanadium SCR catalysts remove nitrogen oxides (NOx) from engine exhaust gases, power plants, and industrial emissions. If NOx is allowed into the atmosphere, it forms smog, acid rain, and a wide variety of other toxic products. Future vanadium catalysts based on nano-designed titanium crystals will most probably be significantly better at reducing these health hazards. People in mega-cities around the world will be able to breathe much cleaner air and live healthier lives. And companies will be able to live up to increasingly strict environmental regulation
C.M. Ek, Q.M. Ramasse, L. Anarson et al., Visualizing atomic-scale redox dynamics in vanadium oxide-based catalysts, Nature Communications 8, 305 (2017).
For more details: https://dx.doi.org/10.1038/s41467-017-00385-y
Towards atomically precise manipulation of 2D nanostructures in the electron microscope
Despite decades of research, the ultimate goal of nanotechnologytop-down manipulation of individual atomshas been directly achieved with only one technique: scanning probe microscopy. In a new topical review published in IOP 2D Materials, scientists from the University of Vienna in collaboration with scientists from SupersTEM and the National Institute of Advanced Industrial Science and Technology (AIST) inTsukuba Japan demonstrate that scanning transmission electron microscopy (STEM) is emerging as an alternative method for the direct assembly of nanostructures, with possible applications in plasmonics, quantum technologies, and materials science.
Using density functional theory molecular dynamics the authors provide a comprehensive reanalysis of available experimental data on beam-driven dynamics in light of the state-of-the-art in simulations, and identify important targets for improvement. Overall, the modern electron microscope has great potential to become an atom-scale fabrication platform, especially for covalently bonded 2D nanostructures.
Toma Susi, D.M. Kepaptsoglou et al. 2017 2D Mater. 4 042004
For more details: https://dx.doi.org/10.1088/2053-1583/aa878f
SuperSTEM from the Skies
When the in-flight movie entertainment doesn't quite cut it the modern researcher can usefully while away the hours with a remote session on the newest of SuperSTEM's instruments.
Robust core-loss EELS modeling of doped graphene
Electron energy loss spectroscopy (EELS) in a STEM microscope is possibly the most powerful analytical tool for understanding the chemical and electronic structure of materials down to the atomic level. However, direct interpretation of the spectra is more than often not trivial. The ability of accurately and quantitatively modelling the EELS response is essential in undertanding experimental results.
In a paper, recently published in the Journal of Physics: Condensed Matter members of SuperSTEM in collaboration with the University of Leeds explore some of the challenges in theoretical density functional theory (DFT) calculations of 1s core-level EEL K-edge spectra of pure, B-doped and N-doped graphene are explored. The ground state approximation is found in this specific system to perform consistently better than the commonly used frozen core-hole approximation. The impact of including or excluding a core-hole on the resultant theoretical band structures, densities of states, electron densities and EEL spectra were all thoroughly examined and compared. It is concluded that the frozen core-hole approximation exaggerates the effects of the core-hole in graphene and should be discarded in favour of the ground state approximation. These results are interpreted as an indicator of the overriding need for theorists to embrace many-body effects in the pursuit of accuracy in theoretical spectroscopy instead of a system-tailored approach whose approximations are selected empirically.
T.P. Hardcastle et al., Robust theoretical modelling of core ionisation edges for quantitative electron energy loss spectroscopy of B- and N-doped graphene, J. Phys.: Condens. Matter 29 (2017) 225303
More details: https://doi.org/10.1088/1361-648X/aa6c4f
Understanding the origin of reduced magnetization in magnetite nanoparticles
Magnetite nanoparticles are partiularly sought after for many technological such as magnetic sensors,
magnetic storage media, MR imaging, but also biomedical applications such as magnetic resonance imaging, targeted drug delvely and cancer treatment. The functionality of the nanoparticles for applications depends crucially on the magnetic properties. Researchers from the Universities of York and Carnegie Mellon Univeristy in collaboration wth SuperSTEM, demonstate how the presence of structural defects such as antiphase boundaries in small magnetite nanoparticles lead to signficantly reduced magnetization, relative to the bulk. Atomistic magnetic modelling of nanoparticles with and without these defects reveals the origin of the reduced moment. Strong antiferromagnetic interactions across antiphase boundaries support multiple magnetic domains even in particles as small as 12-14 nm.
The results appeared in Scientific Reports.
Z. Nedelkoski, D. Kepaptsoglou, et-al., Origin of reduced magnetization and domain formation in small magnetite nanoparticles, Scientific Reports 7 (2017) 45997
More details: http://dx.doi.org/10.1038/srep45997
Unravelling the functionality of high performance thermoelectric oxides in Chemistry of Materials
In the search for clean and renewable energy, thermoelectric oxides emerge as dependable and cheap sources of producing electricity from waste heat. Sr doped Bismuth Cobaltate (BSCO) is one of the best p-type thermoelectric oxides but its structural and electronic properties are still poorly understood. By combining experimental and computational approachs researchers from the Universities of Bath and Manchester in collaboration with SuperSTEM, shed light into the electronic transport mechanism of BSCO. The study shows that level of Bi deficiency in the rock-salt layers,leads to a band gap opening and increases p-type electronic conductivity due to the formation of Co4+ species that serve as itinerant holes within the predominantly Co3+ framework of the CoO2 layer. These atomicscale structural and electronic structure modifications are in turn responsible for the high positive Seebeck coefficient of the material measured experimentally. This provides another step in understanding this fascinating material, which should be of great benefit in future design of oxide thermoelectric materials that are composed of inexpensive and abundant elements.
The results were published in Chemistry of Materials earlier this month.
J.D. Baran, D. Kepaptsoglou, M. Molinari, et al, Role of Structure and Defect Chemistry in High-Performance Thermoelectric Bismuth Strontium Cobalt Oxides, Chemistry of Materials 28 (2016) 74707478
More details: http://dx.doi.org/10.1021/acs.chemmater.6b03200
Advanced techniques for visualising plasmons and understanding their interaction with molecular systems reviewed.
SuperSTEM staff members Patricia Abellan, Fredrik Hage, Quentin Ramasse and former SuperSTEM staff Ruth Chantry contributed to 2 invited reviews in the emerging investigator issue of Analyst and in Advances in Physics: X, in collaboration with Patrick El-Khoury and a research team from Pacific Northwest National Laboratory (PNNL). These two reviews highlight different techniques employed to visualize the enhanced electric fields associated with surface plasmons, and to probe various aspects of the immediate local environments surrounding individual molecules. Through select practical examples from the two laboratories, the team discussed how localized and propagating surface plasmons can be visualized at the ultimate space, time and energy limits using various techniques powered by photons, photoelectrons, and electrons. The prospects of characterizing either bare or chemically functionalized plasmonic nanostructures through a combination of the various described techniques are discussed in the two references provided below.
P. Z. El-Khoury, P. Abellan, Y. Gong, F. S. Hage, J. Cottom, A. G. Joly, R. Brydson, Q. M. Ramasse and W. P. Hess, Visualizing surface plasmons with photons, photoelectrons, and electrons, Analyst, DOI: 10.1039/C6AN00308G (2016)
P.Z. El-Khoury, P. Abellan, R.L. Chantry, Y. Gong, A.G. Joly, I. V. Novikova, J. E. Evans, E. Aprà, D. Hu, Q. M. Ramasse & W.P. Hess, The information content in single-molecule Raman nanoscopy, Advances in Physics X (2016) DOI: 10.1080/23746149.2016.1140010 .
SuperSTEM welcomed schools and families during the Daresbury Open Week
SuperSTEM opened the doors to visitors on 7th July and 9th July. Thursday’s event was dedicated to Key Stages 4 and 5 students and included talks and demonstrations in SuperSTEM 2. During the busiest day of the Daresbury Open Week, the public day on Saturday 9 July, the Science & Technology Facilities Council (STFC) estimates that more than 7,500 people came to Sci-Tech Daresbury. General public, families and members of different laboratories at Sci-Tech Daresbury were welcome to tour SuperSTEM, which included a visit to the newest monochromated instrument, life demonstration in SuperSTEM 2, outdoors posters, an interactive virtual microscope demonstrations and videos for the youngest ones and an introduction about SuperSTEM scope and its role within the scientific community.
Towards direct badgap Ge1-xSnx nanowires: non-equilibrium grown process reported in Nature Communications.
The development of non-equilibrium group IV nanoscale alloys is critical to achieving new functionalities, such as the formation of a direct bandgap in a conventional indirect bandgap elemental semiconductor. Subhakit Biswas, Jessica Doherty and their co-workers from Prof. Justin Holmes’ group at University College Cork describe the fabrication of uniform diameter, direct bandgap Ge1-xSnx alloy nanowires with a Sn incorporation far in excess of the equilibrium solubility of Sn in bulk Ge, through a conventional catalytic bottom-up growth paradigm using noble metal and metal alloy catalysts. STEM-EELS mapping carried out on SuperSTEM 2 in collaboration with SuperSTEM’s Quentin Ramasse was instrumental in determining the distribution of Ge and Sn within the wires, as well as the quality of the interface with the metal seed particles, both essential to the physical properties of the heterostructure wire. The results were published in Nature Communications earlier this month.
S. Biswas, J. Doherty, D. Saladhukha et al., Non-equilibrium induction of tin in germanium: towards direct bandgap Ge1-xSnx semi-conductors, Nature Communications 7, 11405 (2016). DOI: 10.1038/ncomms11405
Breakthrough in controlling the removal of structural defects in chalcogenides absorber thin films for high efficiency solar cells reported in Energy and Environmental Science.
The development of thin-film solar cells has been a success story in recent years in terms of record efficiencies in the lab. Single junction solar cells based on compound semiconductor films have reached higher energy-conversion efficiencies than polycrystalline silicon. Despite this success and the prospects of novel applications such as flexible, lightweight solar panels, the market share of thin-film solar modules is stagnating. A major problem of compound thin-film solar cells, such as Cu(In,Ga)Se2, is the large gap between lab efficiencies and commercial module efficiencies. A large process parameter space makes trial-and-error optimization a time-consuming and expensive task. Therefore, understanding the underlying atomic-scale physics and chemistry is essential to identify the potential origins of efficiency losses in the transfer from lab- to large-scale fabrication. In this contribution results from an international collaboration including the SuperSTEM Laboratory provide direct insight into defect formation and annihilation during the fabrication of Cu(In,Ga)Se2 films. Consequences for process optimization and design are proposed. The presented approach can also be applied to understand other thin-film fabrication processes.
R. Mainz, E. Simsek Sanli, H. Strange et al., Annihilation of structural defects in chalcogenide absorber films for high-efficiency solar cells, Energy and Environmental Science (2016). DOI:10.1039/c6ee00402d
Solvents to Slow Down In Situ Synthesis: A method for creating net molecular hydrogen environment to form homogeneous metal particles in the STEM discussed in Langmuir
By synthesizing nanomaterials of uniform shape and size, the novel properties of metals arising at the nanoscale can be accessed and the fundamental investigation of their structure-property relationships enabled. SuperSTEM’s Patricia Abellan and a team of scientists from Pacific Northwest National Laboratory in collaboration with Virginia Polytechnic Institute and State University, the University of California-San Diego and Florida State University have presented a new approach to synthesize Pd nanoparticles with homogeneous sub-3nm size by molecular hydrogen in the liquid cell. Molecular hydrogen is a widely used reductant in the synthesis of supported metal catalysts. Creating such suitable environment for in situ synthesis in the electron microscope was achieved by using toluene as the solvent and avoiding exposure of the solution to moisture. This work also aimed at finding new methods for reducing the production of radicals upon electron irradiation. Until now, this challenge has been addressed by lowering the amount of imaging electrons delivered to the liquid sample. This research looks at the problem from a different perspective and proposes the possibility of finding a suitable solvent, such as an aromatic hydrocarbon, which is inherently resistant to high energy electron irradiation, to reduce the overall production of radicals for the same electron dose applied.
P. Abellan, L.R. Parent, N. Al-Hasan, C. Park, I. Arslan, A.M. Karim, J.E. Evans and N.D. Browning, Langmuir, 2016, 32, pp 1468–1477
New Paper in Scientific Reports: Atomic and electronic structure of twin growth defects in magnetite
In magnetic oxides any disturbance to the crystal structure is liable to significantly alter properties such as conductivity and magnetic ordering. The overall properties in those materials are strongly dependent on the local atomic co-ordination and structure due to the local nature of electron hopping mechanisms and super exchange interactions.
A team if scientists from the University of York in collaboration with the Tokyo Institute for Technology and SuperSTEM investigate the impact of stable twin defect in the magnetic properties Fe3O4 thin films. By using aberration corrected scanning transmission electron microscopy and spectroscopy and first principles calculations the sciestist look into the effect of the local atomic structural configuration of the twin boundary on the superexchange interactions between the two Fe sublattices across the twin grain boundary.
New Material Increases the Lifetime of Solar-Powered Electrons :Atom-by-atom control leads to an interface that sustains an internal electric field, an innovative property with promise in the energy conversion and storage
Storing sunlight as fuel that can be later used to drive fuel cells requires new materials. A team of scientist from Pacific Nothwest National Laboratories in collaboration with scientists from SuperSTEM and the Univesity of Oxford has demonstrated that by careful desing interfaces between the oxide materials absorb visible light, producing electrons and holes that might be useful for catalyzing reactions, such as producing hydrogen fuel. If there is nothing to pull those electrons and holes apart, however, they will quickly destroy one another without doing anything useful. By synthesizing this material as a series of alternating layers, the team created a built-in electric field to separate the excited electrons and holes openi ng new possibilities for better catalytic performance.
Read more at http://www.pnnl.gov/science/highlights/highlight.asp?id=4208
Battery mystery solved: SuperSTEM scientists unravel structural ambiguities in lithium- and manganese-rich transition metal oxides in Nature Communications
Using complementary microscopy and spectroscopy techniques, SuperSTEM Associate (and long-term visitor from LBNL) Alpesh Shukla reports in Nature Communications how he and colleagues, including SuperSTEM’s Quentin Ramasse and Fredrik Hage, solved the structure of lithium- and manganese-rich transition metal oxides, a potentially game-changing battery material and the subject of intense debate in the decade since it was discovered. This material is important because the battery capacity can potentially be doubled compared to the most commonly used Li-ion batteries today due to the extra lithium in the structure. Until today, however, scientists had been divided on whether the material structure is single trigonal phase, double phase, or defected single monoclinic phase. The new results give very strong support for the defected single-phase monoclinic model and appear to rule out the two-phase model.
A. Shukla, Q.M. Ramasse, C. Ophus, H. Duncan, F. Hage and G. Chen, Unravelling structural ambiguities in lithium- and manganese-rich transition metal oxides, Nature Communications 6, 8711 (2015).
The new graphene? Liquid-exfoliated black phosphorus in Nature Communications
SuperSTEM collaborators at Trinity College Dublin have demonstrated the successful chemical exfoliation of few-layers solvent-stabilized black phosphorus, a new two-dimensional material which is of great interest for applications, mainly in electronics. Thanks to the use of specific solvents during the exfoliation, Damien Hanlon and co-workers were able to mitigate the normally very rapid structural deterioration of this material, enabling its visualization with atomic resolution using SuperSTEM’s microscropes. The study, published in Nature Communications, also demonstrates that liquid-exfoliated BP nanosheets are potentially useful in a range of applications from ultrafast saturable absorbers to gas sensors to fillers for composite reinforcement.
D. Hanlon, C. Backes, E. Doherty, C.S. Cucinotta, N.C. Berner, C. Boland, K. Lee, A. Harvey, P. Lynch, Z. Gholamvand, S. Zhang, K. Wang, G. Moynihan, A. Pokle, Q.M. Ramasse, N. McEvoy, W.J. Blau, J. Wang, G. Abellan, F. Hauke, A. Hirsch, S. Sanvito, D.D. O’Regan, G.S. Duesberg, V. Nicolosi and J.N. Coleman, Liquid exfoliation of solvent-stabilized few-layer black phosphorus for applications beyond electronics, Nature Communications 6, 8563 (2015).
Spectroscopic signature of doping in graphene
SuperSTEM researchers in collaboration with researchers from the Universities of Leeds, Manchester and Gottingen investigate the electronic structure modifications incurred by free-standing graphene through two types of single-atom doping. Trough careful comparison with density functional theory calculations the researchers show that EELS spectra acquired from single B or N dopants can be used as direct fingerprints of the expected p- and n-type behaviour of doped graphene.
D.M. Kepaptsoglou, T.P. Hardcastle, C.R. Seabourne, U. Bangert, R. Zan, J.A. Amani, H. Hofsass, R.J. Nicholls, R. Brydson, A.J. Scott and Q.M. Ramasse, Electronic structure modification of ion-implanted graphene: the scpectroscopic signatures of p- and n-type doping, ACS Nano, Articles ASAP (2015).
Atoms in close-up: SuperSTEM features in Cosmos Magazine
Australia's renowed Cosmos magazine features SuperSTEM research in its look at the building blocks of matter:
What nanoparticulate dispersions look like: review article in Journal of Microscopy
Prof. Rik Brydson and researchers from the University of Leeds were invited by the editors of Journal of Microscopy to review the most common methods for determining the dispersion state of nanoparticulate samples, particularly in liquid media. The team and their collaborators, including SuperSTEM staff Patricia Abellan focused on the determination of particle sizes and shapes as well as particle structure and chemistry, key parameters for understanding their behaviour applied across a very wide range of technologies and industry sectors. The review highlights the potential contributions of scanning probe and electron microscopies and also includes an extensive table summarising the major non-microscopy techniques employed to analyse particulate dispersions.
R. Brydson, A. Brown, C. Hodges, P. Abellan and N. Hondow, Microscopy of Nanoparticulate Dispersions, Journal of Microscopy, Journal of Microscopy, Articles ASAP, doi: 10.1111/jmi.12290 (2015).
New paper in Nano Letters: electrical nature of nano-contacts
A recent paper in Nano Letters by Alex Lord and co-workers from the University of Swansea explores the electrical behaviour of nanocontacts between free-standing ZnO nanowires and the catalytic Au particles used for their growth, showing how the nature of the contact can switch from Schottky to Ohmic depending on the size of the particles in relation to the cross-sectional width of the nanowires. Instrumental to this study were results obtained in collaboration with SuperSTEM staff Quentin Ramasse and Demie Kepaptsoglou.
A.M. Lord, T.G. Maffeis, O. Kryvchenkova, R.J. Cobley, K. Kalna, D.M. Kepaptsoglou, Q.M. Ramasse, A.S. Walton, M.B. Ward, J. Köble and S.P. Wilks, Controlling the electrical transport properties of nanocontacts to nanowires, Nano Letters, Articles ASAP, doi: 10.1021/nl503743t (2015).
Farewell to Mervyn Shannon
After more than 12 years on the SuperSTEM team as Industrial Director, co-Director and on-site Director, Professor Mervyn Shannon recently announced his decision to take an early retirement. An avid traveler and rambler, Mervyn will no doubt spend a fair amount of his extra free time hiking here and abroad, using the high-tech walking poles (graphene re-inforced!) the team bought him as part of his farewell present. But his association with SuperSTEM will not end so abruptly: as honorary Visiting Professor at the University of Liverpool, he will still be coming to the lab very regularly to keep up with new projects and to work on his own research, as a hobby. We wish him all the best!
Pictures from the farewell party at our favourite curry house in Stockton Heath, with special guests Ondrej Krivanek and Niklas Dellby.
New paper in Nature Communications: magnetic phase gradients at complex oxides interfaces
New research highlight! SuperSTEM user Steven Spurgeon uses atomic-resolution STEM-EELS results obtained in collaboration with on-site staff Demie Kepaptsoglou and Quentin Ramasse to show how a magnetic asymmetry observed at the La0.7Sr0.3MnO3 (LSMO)/PbZr0.2Ti0.8O3 (PZT) interface depends on the local PZT polarization and gives rise to gradients in local magnetic moments. The full details have just been published in Nature Communications.
S.R. Spurgeon, P.V. Balachandran, D.M. Kepaptsoglou, A.R. Damodaran, C.L. Johnson, J. Karthik, S. Nejati, L. Jones, H. Ambaye, V. Lauter, Q.M. Ramasse, K.S. Lau, J.M. Rondinelli, L.W. Martin and M.L. Taheri, Polarization screening-induced magnetic phase gradients at complex oxide interfaces, Nature Communications 6, 6735 (2015).
SuperSTEM looks back at a successful SuperSTEM 3 inauguration
Over 120 guests joined the SuperSTEM team and EPSRC to celebrate the installation on STFC's Daresbury Scientific Campus of the facility's new state-of-the-art monochromated Nion Hermes microscope during a hugely successful two-day international workshop.
World-renowned speakers delivered inspiring scientific lectures and provided their views and hopes for what scientists might be able to achieve with this new generation of electron microscope. The "excitement of the unknown", prospects for "mapping phonons and other low energy excitations" were systematic topics of discussion during the lectures, over coffee and late into the night after the gala dinner. These are exciting times for electron microscopy, and with the unprecedented <15meV resolution this instrument already achieves a mere 3 weeks after its arrival on site (in boxes), Prof. Archie Howie's hope to "lure physicists back into electron microscopy to tackle the experimental and theoretical challenges posed by such capabilities" may soon come true.
Read more on our events page.
The installation of the new SuperSTEM 3 is in full swing - and it's big!
Proud to announce the delivery of our new SSTEM3 microscope!!!
A very cold (the outside temperature is barely reaching 0 deg C) but very exciting day for SuperSTEM. The much anticipated Nion UtraSTEM100MC ("HERMES") microscope is finally delivered on site!
A late Christmas present: new microscope shipping from the factory!
Happy New year to all our SuperSTEM users and collaborators: and what better way to start the New Year than with a late Christmas present? Our new microscope, a Nion UltraSTEM100MC ("HERMES") is now on its way from the factory and will be installed and commissioned over the next few weeks in its new custom-designed room at SuperSTEM.
Stay tuned for more news of the installation!! For now, here is a picture of the crates (without wrapping paper or a little bow :( ) waiting to be picked up for shipment outside Nion Co. (photo courtesy of Nion scientist Tracy Lovejoy).
Summary of SuperSTEM User Survey
Thanks to everyone who took the time to complete the survey. Generally you were very supportive of our work to date and of the additional aspects regarding sample preparation, data processing and modelling that we asked about.
Your views were briefly summarised and included in the Statement of Need we submitted to EPSRC on 15 October for the continuation of a Mid-Range Facility for Aberration-Corrected STEM from 2016 - 2021.
A detailed summary of the survey can be found here.