Publications
358 results found
Deitz JI, Carnevale SD, De Graef M, et al., 2016, Characterization of encapsulated quantum dots via electron channeling contrast imaging, Applied Physics Letters, Vol: 109, ISSN: 0003-6951
A method for characterization of encapsulated epitaxial quantum dots (QD) in plan-view geometry using electron channeling contrast imaging (ECCI) is presented. The efficacy of the method, which requires minimal sample preparation, is demonstrated with proof-of-concept data from encapsulated (sub-surface) epitaxial InAs QDs within a GaAs matrix. Imaging of the QDs under multiple diffraction conditions is presented, establishing that ECCI can provide effectively identical visualization capabilities as conventional two-beam transmission electron microscopy. This method facilitates rapid, non-destructive characterization of sub-surface QDs giving immediate access to valuable nanostructural information.
Liu G, Wang Y, Zou B, et al., 2016, Probing the Electronic Structures of BaTiO3/SrTiO3 Multilayered Film with Spatially Resolved Electron Energy-Loss Spectroscopy, Journal of Physical Chemistry C, Vol: 120, Pages: 16681-16686, ISSN: 1932-7455
A multilayered film of BaTiO3/SrTiO3 was grown on a LaAlO3 substrate using dual-target pulsed laser deposition technique. High-resolution scanning transmission electron microscopy observations show that the nine unit-cell BaTiO3 layer and the three unit-cell SrTiO3 layer are alternatively arranged in the epitaxial film where a sharp interface exists between the BaTiO3 and SrTiO3 layers. Electron energy-loss spectroscopy analysis demonstrates that the O-K edge spectra of SrTiO3 and BaTiO3 layers are quite distinct; in particular, the energy-loss peak at 547 eV in the SrTiO3 spectrum splits into two peaks in the BaTiO3 spectrum. The multiple-scattering calculations of O-K edge spectra for BaTiO3 and SrTiO3 agree well with the experimental results. The low-energy region (<542 eV) of the O-K edge spectra for both BaTiO3 and SrTiO3 is mainly caused by the hybridization of the O 2p with Ti 3d orbitals. The splitting peaks between 542 and 552 eV in the O-K edge spectra of BaTiO3 are attributed to its complex crystal structure including two unequal oxygen sites and low site symmetry.
Ni N, Cooper SJ, Williams R, et al., 2016, Degradation of (La0.6Sr0.4)0.95(Co0.2Fe0.8)O3-δ Solid Oxide Fuel Cell Cathodes at the Nanometre Scale and Below, ACS Applied Materials & Interfaces, Vol: 8, Pages: 17360-17370, ISSN: 1944-8244
The degradation of intermediate temperature solid oxide fuel cell (ITSOFC) cathodes has been identified as a major issue limiting the development of ITSOFCs as high efficiency energy conversion devices. In this work, the effect of Cr poisoning on (La0.6Sr0.4)0.95(Co0.2Fe0.8)O3-δ (LSCF6428), a particularly promising ITSOFC cathode material, was investigated on symmetrical cells using electrochemical impedance spectroscopy and multi-scale structural/chemical analysis by advanced electron and ion microscopy. The systematic combination of bulk and high-resolution analysis on the same cells allows, for the first time, to directly correlate Cr induced performance degradation with subtle and localized structural/chemical changes of the cathode down to the atomic scale. Up to two orders of magnitude reduction in conductivity, oxygen surface exchange rate and diffusivity were observed in Cr poisoned LSCF6428 samples. These effects are associated with the formation of nanometer size SrCrO4; grain boundary segregation of Cr; enhanced B-site element exsolution (both Fe and Co); and reduction in the Fe valence, the latter two being related to Cr substitution in LSCF. The finding that significant degradation of the cathode happens before obvious microscale change points to new critical SOFC degradation mechanisms effective at the nanometer scale and below.
Sarwar ATMG, Yang F, Esser BD, et al., 2016, Self-assembled InN micro-mushrooms by upside-down pendeoepitaxy, JOURNAL OF CRYSTAL GROWTH, Vol: 443, Pages: 90-97, ISSN: 0022-0248
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- Citations: 7
Smith TM, Hooshmand MS, Esser SD, et al., 2016, Atomic-scale characterization and modeling of 60° dislocations in a high-entropy alloy, ACTA MATERIALIA, Vol: 110, Pages: 352-363, ISSN: 1359-6454
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- Citations: 143
Liberti E, Menzel R, Shaffer MS, et al., 2016, Probing the size dependence on the optical modes of anatase nanoplatelets using STEM-EELS, Nanoscale, Vol: 8, Pages: 9727-9735, ISSN: 2040-3372
Anatase titania nanoplatelets with predominantly exposed {001} facets have been reported to have enhanced catalytic properties in comparison with bulk anatase. To understand their unusual behaviour, it is essential to fully characterize their electronic and optical properties at the nanometer scale. One way of assessing these fundamental properties is to study the dielectric function. Valence electron energy-loss spectroscopy (EELS) performed using a scanning transmission electron microscope (STEM) is the only analytical method that can probe the complex dielectric function with both high energy (<100 meV) and high spatial (<1 nm) resolution. By correlating experimental STEM-EELS data with simulations based on semi-classical dielectric theory, the dielectric response of thin (<5 nm) anatase nanoplatelets was found to be largely dominated by characteristic (optical) surface modes, which are linked to surface plasmon modes of anatase. For platelets less than 10 nm thick, the frequency of these optical modes varies according to their thickness. This unique optical behaviour prompts the enhancement of light absorption in the ultraviolet regime. Finally, the effect of finite size on the dielectric signal is gradually lost by stacking consistently two or more platelets in a specific crystal orientation, and eventually suppressed for large stacks of platelets.
Goode AE, Porter AE, Kłosowski MM, et al., 2016, Analytical transmission electron microscopy at organic interfaces, Current Opinion in Solid State and Materials Science, Vol: 21, Pages: 55-67, ISSN: 1359-0286
Organic materials are ubiquitous in all aspects of our daily lives. Increasingly there is a need to understand interactions between different organic phases, or between organic and inorganic materials (hybrid interfaces), in order to gain fundamental knowledge about the origin of their structural and functional properties. In order to understand the complex structure–property–processing relationships in (and between) these materials, we need tools that combine high chemical sensitivity with high spatial resolution to allow detailed interfacial characterisation. Analytical transmission electron microscopy (TEM) is a powerful and versatile technique that can fulfil both criteria. However, the application of analytical TEM to organic systems presents some unique challenges, such as low contrast between phases, and electron beam sensitivity. In this review recent analytical TEM approaches to the nanoscale characterisation of two systems will be discussed: the hybrid collagen/mineral interface in bone, and the all-organic donor/acceptor interface in OPV devices.
Butcher DP, Wadams RC, Drummy L, et al., 2016, Controlled Dispersion of Polystyrene-Capped Au Nanoparticles in P3HT:PC<sub>61</sub>BM and Consequences upon Active Layer Nanostructure, JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS, Vol: 54, Pages: 709-720, ISSN: 0887-6266
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- Citations: 1
Gallagher JC, Esser BD, Morrow R, et al., 2016, Epitaxial growth of iridate pyrochlore Nd<sub>2</sub>Ir<sub>2</sub>O<sub>7</sub> films, SCIENTIFIC REPORTS, Vol: 6, ISSN: 2045-2322
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- Citations: 29
Li B, Luo X, Deng B, et al., 2016, Effects of local structural transformation of lipid-like compounds on delivery of messenger RNA, SCIENTIFIC REPORTS, Vol: 6, ISSN: 2045-2322
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- Citations: 32
Marsh JM, Davis MG, Lucas RL, et al., 2015, Preserving fibre health: reducing oxidative stress throughout the life of the hair fibre, INTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Vol: 37, Pages: 16-24, ISSN: 0142-5463
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- Citations: 8
Li B, Luo X, Deng B, et al., 2015, An Orthogonal Array Optimization of Lipid-like Nanoparticles for mRNA Delivery in Vivo, NANO LETTERS, Vol: 15, Pages: 8099-8107, ISSN: 1530-6984
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- Citations: 150
Chiu Y-H, Minutillo NG, Williams REA, et al., 2015, Photoluminescence evolution in GaAs/AlGaAs core/shell nanowires grown by MOCVD: Effects of core growth temperature and substrate orientation, JOURNAL OF CRYSTAL GROWTH, Vol: 429, Pages: 1-5, ISSN: 0022-0248
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- Citations: 1
Smith TM, Esser BD, Antolin N, et al., 2015, Segregation and η phase formation along stacking faults during creep at intermediate temperatures in a Ni-based superalloy, ACTA MATERIALIA, Vol: 100, Pages: 19-31, ISSN: 1359-6454
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- Citations: 104
Sarwar ATMG, Carnevale SD, Yang F, et al., 2015, Semiconductor Nanowire Light-Emitting Diodes Grown on Metal: A Direction Toward Large-Scale Fabrication of Nanowire Devices, SMALL, Vol: 11, Pages: 5402-5408, ISSN: 1613-6810
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- Citations: 93
Marsh JM, Davis MG, Flagler MJ, et al., 2015, Advanced hair damage model from ultra-violet radiation in the presence of copper, INTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Vol: 37, Pages: 532-541, ISSN: 0142-5463
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- Citations: 18
Sarwar ATMG, May BJ, Deitz JI, et al., 2015, Tunnel junction enhanced nanowire ultraviolet light emitting diodes, APPLIED PHYSICS LETTERS, Vol: 107, ISSN: 0003-6951
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- Citations: 50
Chen Y, Tellez H, Burriel M, et al., 2015, Segregated Chemistry and Structure on (001) and (100) Surfaces of (La<sub>1-<i>x</i></sub>Sr<i><sub>x</sub></i>)<sub>2</sub>CoO<sub>4</sub> Override the Crystal Anisotropy in Oxygen Exchange Kinetics, CHEMISTRY OF MATERIALS, Vol: 27, Pages: 5436-5450, ISSN: 0897-4756
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- Citations: 111
Kim D-G, Jeong Y-H, Kosel E, et al., 2015, Regional variation of bone tissue properties at the human mandibular condyle, BONE, Vol: 77, Pages: 98-106, ISSN: 8756-3282
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- Citations: 27
Deitz JI, Carnevale SD, Ringel SA, et al., 2015, Electron Channeling Contrast Imaging for Rapid III-V Heteroepitaxial Characterization, JOVE-JOURNAL OF VISUALIZED EXPERIMENTS, ISSN: 1940-087X
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- Citations: 16
Klosowski MM, Friederichs RJ, Nichol R, et al., 2015, Probing carbonate in bone forming minerals on the nanometre scale, Acta Biomaterialia, Vol: 20, Pages: 129-139, ISSN: 1878-7568
To devise new strategies to treat bone disease in an ageing society, a more detailed characterisation of the process by which bone mineralises is needed. In vitro studies have suggested that carbonated mineral might be a precursor for deposition of bone apatite. Increased carbonate content in bone may also have significant implications in altering the mechanical properties, for example in diseased bone. However, information about the chemistry and coordination environment of bone mineral, and their spatial distribution within healthy and diseased tissues, is lacking. Spatially resolved analytical transmission electron microscopy is the only method available to probe this information at the length scale of the collagen fibrils in bone. In this study, scanning transmission electron microscopy combined with electron energy-loss spectroscopy (STEM-EELS) was used to differentiate between calcium-containing biominerals (hydroxyapatite, carbonated hydroxyapatite, beta-tricalcium phosphate and calcite). A carbon K-edge peak at 290 eV is a direct marker of the presence of carbonate. We found that the oxygen K-edge structure changed most significantly between minerals allowing discrimination between calcium phosphates and calcium carbonates. The presence of carbonate in carbonated HA (CHA) was confirmed by the formation of peak at 533 eV in the oxygen K-edge. These observations were confirmed by simulations using density functional theory. Finally, we show that this method can be utilised to map carbonate from the crystallites in bone. We propose that our calibration library of EELS spectra could be extended to provide spatially resolved information about the coordination environment within bioceramic implants to stimulate the development of structural biomaterials.
Yazdi S, Kasama T, Beleggia M, et al., 2015, Towards quantitative electrostatic potential mapping of working semiconductor devices using off-axis electron holography, ULTRAMICROSCOPY, Vol: 152, Pages: 10-20, ISSN: 0304-3991
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- Citations: 29
Carnevale SD, Deitz JI, Carlin JA, et al., 2015, Applications of Electron Channeling Contrast Imaging for the Rapid Characterization of Extended Defects in III-V/Si Heterostructures, IEEE JOURNAL OF PHOTOVOLTAICS, Vol: 5, Pages: 676-682, ISSN: 2156-3381
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- Citations: 33
Wang D, Chen CW, Dalton JC, et al., 2015, "Colossal" interstitial supersaturation in delta ferrite in stainless steels I. Low-temperature carburization, ACTA MATERIALIA, Vol: 86, Pages: 193-207, ISSN: 1359-6454
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- Citations: 15
Sarwar ATMG, Carnevale SD, Kent TF, et al., 2015, Tuning the polarization-induced free hole density in nanowires graded from GaN to AlN, APPLIED PHYSICS LETTERS, Vol: 106, ISSN: 0003-6951
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- Citations: 19
Erhard N, Sarwar ATMG, Yang F, et al., 2015, Optical Control of Internal Electric Fields in Band Gap-Graded InGaN Nanowires, NANO LETTERS, Vol: 15, Pages: 332-338, ISSN: 1530-6984
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- Citations: 25
Deitz JI, Carnevale SD, Ringel SA, et al., 2015, Extending Characterization Applications of Electron Channeling Contrast Imaging, IEEE 42nd Photovoltaic Specialist Conference (PVSC), Publisher: IEEE, ISSN: 0160-8371
Goode AE, Porter AE, Ryan MP, et al., 2014, Correlative electron and X-ray microscopy: probing chemistry and bonding with high spatial resolution, Nanoscale, Vol: 7, Pages: 1534-1548, ISSN: 2040-3372
Two powerful and complementary techniques for chemical characterisation of nanoscale systems are electron energy-loss spectroscopy in the scanning transmission electron microscope, and X-ray absorption spectroscopy in the scanning transmission X-ray microscope. A correlative approach to spectro-microscopy may not only bridge the gaps in spatial and spectral resolution which exist between the two instruments, but also offer unique opportunities for nanoscale characterisation. This review will discuss the similarities of the two spectroscopy techniques and the state of the art for each microscope. Case studies have been selected to illustrate the benefits and limitations of correlative electron and X-ray microscopy techniques. In situ techniques and radiation damage are also discussed.
Fraser HL, McComb DW, Williams REA, 2014, Transmission Electron Microscopy for Physical Metallurgists, Physical Metallurgy: Fifth Edition, Pages: 1143-1226, ISBN: 9780444537706
The aim of this chapter is to provide the reader with an outline of the methods most commonly used to characterize samples, taken from studies involving physical metallurgy, using techniques allied with transmission electron microscopy. In the main, rather than provide full and comprehensive details on all methods including various imaging techniques, diffraction methods, and analytical spectroscopies, it is the attempt of the coauthors to outline techniques, and then provide ways in which difficulties in interpretation may be avoided.
Taub S, Williams REA, Wang X, et al., 2014, The effects of transition metal oxide doping on the sintering of cerium gadolinium oxide, ACTA MATERIALIA, Vol: 81, Pages: 128-140, ISSN: 1359-6454
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- Citations: 24
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