Table of contents

It has once again been my pleasure to act as editor for these proceedings, and I must thank all those who have acted as reviewers. I am always struck by the scientific quality of the oral and poster contributions and the vibrant discussions that occur both in the formal sessions and in the exhibition space at EMAG. I am convinced that a crucial part of maintaining that scientific quality is the opportunity that is offered of having a paper fully reviewed by two internationally selected referees and published in the Journal of Physics: Conference Series. For many students, this is the first fully reviewed paper they publish. I hope that, like me, you will be struck by the scientific quality of the 80 papers that follow, and that you will find them interesting and informative.

I must also personally thank all the organisers of EMAG2013 for arranging such an excellent meeting. Ian MacLaren, as Chair of the EMAG Group and of the meeting itself, has contributed a foreword to these proceedings describing the meeting in more detail. A particular highlight of the conference was the special symposium in honour of Professor Archie Howie. We all enjoyed a wonderful speech from Archie at the conference dinner, along with some of his electron microscopy-related poetry. I have great pleasure in publishing the conference dinner poems in this proceedings.

I hope you will find these proceedings to be an interesting read and an invaluable resource.

Pete Nellist

Conference chair: Dr I MacLaren Programme organiser: Dr C Ducati Proceedings editor: Prof P D Nellist Trade exhibition organiser: C Hockey (CEM Group) Local organisers: Professor E Boyes, Professor P Gai, Dr R Kröger, Dr V Lazarov, Dr P O'Toole, Dr S Tear and Professor J Yuan Advanced school organisers: Dr S Haigh, Dr A Brown Other committee members: Mr K Meade, Mr O Heyning, Dr M Crawford, Mr M Dixon and Dr Z Li

EMAG2013 was certainly the biggest EMAG conference I can remember in my twenty years of going to EMAG conferences. We had a total of about 180 scientific delegates, not including exhibitors. The conference also benefited from the York conference centre allowing us to integrate the scientific sessions, refreshments and exhibition in one building. This all made for a very vibrant and focused conference. The quality of the presentations was again very high and judging by many of the student talks given, there is plenty of hope for an excellent future for electron microscopy in the UK.

A unique feature of this conference was a chance to organise a session to commemorate the 80th year of one of the pioneers of electron microscopy in the UK, Professor Archie Howie. An excellent symposium was organised in his honour by one of his former students, Professor Pratibha Gai of the University of York. This was dedicated to one field that he made some important initial contributions to: in-situ microscopy. The symposium gave a depth and breadth of overview to this field unusual at an EMAG conference, with speakers from the UK, Europe, Japan and the USA and gave a real taste of some of the possibilities in the latest instruments to observe real materials at work at nanometre or even atomic resolution.

Professor Howie himself gave a highly entertaining retrospective of his time working in microscopy from the 1950s until the present in his talk after the conference dinner on the Thursday evening at the excellent York National Railway Museum. We also had excellent plenary lectures from Professor Wolfgang Baumeister on a topic perhaps novel to many at EMAG, TEM in Structural Biology; from Professor Prathibha Gai on atomic resolution in-situ studies of chemical reactions in the TEM; and Professor Archie Howie discussing some of the important current open questions in TEM and STEM.

This proceedings therefore presents a snapshot of a broad cross-section of the exciting work going on in electron microscopy in 2013. As always, the papers are ordered thematically according to the sessions organised at the conference. As ever, I have a great debt of gratitude to my fellow EMAG committee members who chaired the various sessions and who, together with the programme chair, Dr Cate Ducati of the University of Cambridge helped to put together such an excellent programme. I also gratefully acknowledge the many hours invested by Professor Pete Nellist of the University of Oxford who then edited this proceedings and ensured that the peer review and revision process ran as smoothly as possible. Finally, I hope that you enjoy reading the contributions made by many to this excellent conference.

Dr Ian MacLaren, Chair of the Electron Microscopy and Analysis Group

Archie Howie's poems are available in the PDF

All papers published in this volume of Journal of Physics: Conference Series have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

Recent experiments prompt rethinking of the basics of elastic and inelastic electron scattering in electron microscopy. Standard approximations of elastic scattering largely based Bragg's law seem less clearly relevant when individual columns or even single atoms are probed. Phase shift analysis of atomic scattering can provide some checks and insights. The dielectric theory of aloof beam interactions is severely tested by observations of nanoparticle recoil but may be capable of explaining de-coherence effects induced by thermal fluctuations.

Observing reacting single atoms on the solid catalyst surfaces under controlled reaction conditions is a key goal in understanding and controlling heterogeneous catalytic reactions. In-situ real time aberration corrected environmental (scanning) transmission electron microscopy (E(S)TEM permit the direct imaging of dynamic surface and sub-surface structures of reacting catalysts. In this paper in-situ AC ETEM and AC ESTEM studies under controlled reaction environments of oxide catalysts and supported metal nanocatalysts important in chemical industry are presented. They provide the direct evidence of dynamic processes at the oxide catalyst surface at the atomic scale and single atom dynamics in catalytic reactions. The ESTEM studies of single atom dynamics in controlled reaction environments show that nanoparticles act as reservoirs of ad-atoms. The results have important implications in catalysis and nanoparticle studies.

Today's biomolecular electron microscopy uses essentially three different imaging modalities: (i) electron crystallography, (ii) single particle analysis and (iii) electron tomography. Ideally, these imaging modalities are applied to frozen-hydrated samples to ensure an optimum preservation of the structures under scrutiny. Electron crystallography requires the existence of two-dimensional crystals. In principle, electron crystallography is a high-resolution technique and it has indeed been demonstrated in a number of cases that near-atomic resolution can be attained. Single-particle analysis is particularly suited for structural studies of large macromolecular complexes. The amount of material needed is minute and some degree of heterogeneity is tolerable since image classification can be used for further 'purification in silico'. In principle, single particle analysis can attain high-resolution but, in practice, this often remains an elusive goal. However, since medium resolution structures can be obtained relatively easily, it often provides an excellent basis for hybrid approaches in which high-resolution structures of components are integrated into the medium resolution structures of the holocomplexes. Electron tomography can be applied to non-repetitive structures. Most supramolecuar structures inside cells fall into this category. In order to obtain three-dimensional structures of objects with unique topologies it is necessary to obtain different views by physical tilting. The challenge is to obtain large numbers of projection images covering as wide a tilt range as possible and, at the same time, to minimize the cumulative electron dose. Cryoelectron tomography provides medium resolution three-dimensional images of a wide range of biological structures from isolated supramolecular assemblies to organelles and cells. It allows the visualization of molecular machines in their functional environment (in situ) and the mapping of entire molecular landscapes.

Environmental scanning transmission electron microscopy (ESTEM) with aberration correction (AC) has recently been added to the capabilities of the more established ETEM for analysis of heterogeneous nanoparticle based catalysts. It has helped to reveal the importance and potentially unique properties of individual atoms as active sites in their own right as well as pathways between established nanoparticles. A new capability is introduced for dynamic in-situ experiments under controlled conditions of specimen temperature and gas environment related to real world conditions pertinent to a range of industrial and societal priorities for new and improved chemical processes, materials, fuels, pharmaceutical products and processes, and in control or remediation of environmental emissions.

A sub-50pm resolution electron microscope was applied for in-situ studies of ion transport in lithium ion battery and CO-oxidation catalyst. Lithium ions in LiM₂O₄ electrodes (M: transition metals) and titanium ions in Au/TiO₂ catalyst were enabled us to observe individually by ABF-STEM and TEM. Transport of lithium ions was seen, after in-situ observations, to induce structural transformation of the electrode materials that causes irreversible cycle of the battery reaction. Transport of the interstitial titanium ions results, due to oxygen gas for CO-oxidation, in modification of Au/TiO₂ interface structure. In-situ studies, thus, revealed materials' transformation induced locally by ion/electron transport of the battery/catalyst system at high resolution and high contrast.

Interest in nanotechnology is driven by unprecedented means to tailor the physical behaviour via structure and composition. Unlike bulk materials, minute changes in size and shape can affect the optical properties of nanoparticles. Characterization, understanding, and prediction of such structure-function relationships is crucial to the development of novel applications such as plasmonic sensors, devices, and drug delivery systems. Such knowledge has been recently vastly expanded through systematic, high throughput correlated measurements, where the localized surface plasmon resonance (LSPR) is probed optically and the particle shape investigated with electron microscopy. This paper will address some of the recent experimental advances in single particle studies that provide new insight not only on the effects of size, composition, and shape on plasmonic properties but also their interrelation. Plasmon resonance frequency and decay, substrate effects, size, shape, and composition will be explored for a variety of plasmonic systems.

There have been reports of challenges in designing platinum carbon (Pt/C) electrode catalysts for PEMFC. Pt/C electrode catalysts deactivate much faster on the cathode (in moisturized O₂) than on the anode (in H₂). To understand influences of moisture and oxygen on the deactivation of the Pt/C catalysts in proton-exchange-membrane fuel cells (PEMFCs), spherical-aberration-corrected environmental transmission electron microscopy (AC-ETEM) was applied with a high-speed CCD camera. Structural changes of the Pt/C electrode catalysts were dynamically recorded in moisturized nitrogen, oxygen and hydrogen. The mass spectrometry confirmed the moisture content (between 5 to 30 %) of nitrogen driving gas through a humidifier. Coalescence of platinum nanoparticles (D = 3.24 nm) was carefully evaluated in pure N₂ and moisturized N₂ atmosphere. The Pt/C showed considerable structural weakness in a moisturized N2 atmosphere. Comparable results obtained by AC-ETEM in different gas atmospheres also suggested ways to improve the oxygen reduction reaction (ORR). In this paper, the deactivation process due to moisture (hydroxylation) of carbon supports is discussed using for comparison the movement of platinum nanoparticles measured in moisturized nitrogen and pure nitrogen atmospheres.

Environmental transmission electron microscopy has recently emerged as topics of great interest as well as ultra-high resolution electron microscopy using aberration correctors. Current research in this area has been focusing on dynamic observation with atomic resolution under gaseous atmospheres and in liquids. Nagoya University has been developing a new 1-MV high voltage (scanning) transmission electron microscope, which can be used to observe nano-materials under conditions that include the presence of gases, liquids and illuminating lights, and it can be also used to perform mechanical operations to nm-sized areas as well as electron tomography and elemental analysis by electron energy loss spectroscopy.

We present an in-situ study of the reduction of Co₃O₄ to CoO. Co based catalysts are promising for Fischer Tropsch process reactions in which heavy fuels such as diesel are synthesised from CO₂ and H₂. Co₃O₄ is the precursor and must be reduced by H₂ to Co. Although there have been many studied of this process, both ex-situ and in-situ, there is no consensus on how Co₃O₄ transforms to CoO including how defects influence the transformation mechanism. Our results show that dislocations are formed between Co₃O₄ and CoO regions and a fuse-wire like transformation is observed in crystals above 15 nm diameter.

Environmental transmission electron microscopy (ETEM) studies MgO nanorod growth from Au catalyst nanoparticles in a controlled gas atmosphere have been performed, in order to elucidate the mobility of Au surface atoms and the configuration of the Au/MgO interface. MgO nanorod growth is driven by the electron beam and found to be strongly dependent on the gaseous environment in the microscope and electron beam current density.

With the advent of in-situ heating stages that can fit into SEM's and the combination with EBSD, it is now possible to directly observe phenomenon such as phase transformations and recrystallisation at high spatial resolution and to link these processes to microstructural parameters.

This presentation will report some results from preliminary in-situ EBSD heating experiments conducted in an SEM on the transformation of ausenite to ferrite in a plain carbon steel and recrystallisation in bronze alloy strip cast on a steel substrate. The microstructural changes observed during these experiments will be reported in terms of EBSD maps, grains size and crystallographic texture that evolves during a) a heating cycle from ferrite to austenite and cooling to ferrite and b) the recrystallisation microstructure for bronze and steel during isochronal heating.

In 1975 the Scanning Transmission Electron Microscope promised to deliver point-by-point information, both structural and chemical, relating to problems of grain boundary segregation, nanostructured phases, glassy materials, and heterogeneous catalysts. Diffraction contrast, so important in TEM, for a while continued to play an important role. But the full utilisation of Crewe's ADF technique, developed for single atoms, but now applied to crystals, required the elimination so far as possible of diffraction contrast. Archie Howie recognised that elimination of Bragg scattered beams, whilst retaining incoherently scattered electrons at larger angles, could be achieved by modifying Crewe's annular detector. High Angle Annular Dark Field, HAADF, is now the most widely used imaging mode in STEM. 'HAADF' might with justification stand for 'Howie's Adaptation of Annular Dark Field'!

In this paper we describe a methodology developed at the University of Cadiz (Spain) in the past few years for the extraction of quantitative information from electron microscopy images at the atomic level. This work is based on a coordinated and synergic activity of several research groups that have been working together over the last decade in two different and complementary fields: Materials Science and Computer Science. The aim of our joint research has been to develop innovative high-performance computing techniques and simulation methods in order to address computationally challenging problems in the analysis, modelling and simulation of materials at the atomic scale, providing significant advances with respect to existing techniques. The methodology involves several fundamental areas of research including the analysis of high resolution electron microscopy images, materials modelling, image simulation and 3D reconstruction using quantitative information from experimental images. These techniques for the analysis, modelling and simulation allow optimizing the control and functionality of devices developed using materials under study, and have been tested using data obtained from experimental samples.

The impact of graphitisation-type processes on the carbon K-edge ELNES is explored for model systems using the CASTEP density functional theory code. For c lattice direction expansion, contraction of spectral peaks occurs between 20 and 27 eV above the edge onset, for a/b lattice dimension expansion spectral peaks are heavily compressed in terms of energy separation and are shifted towards the edge-onset, consistent with a 1/a² relationship. For a nanotube model system, it is shown that for higher curvature, an additional feature was observed in the spectrum ~5 eV, arguably consistent with 'fullerene'-type character.

In high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) the data is generally interpreted as the convolution of the sample's sharply-peaked object function with the intensity of the real-valued point-spread function (PSF) of the illumination. As a single image is itself necessarily two-dimensional (2D) it is typically assumed that the object function and PSF can also be accurately described as 2D; this is the so-called 2D-object imaging assumption. Here the validity of these two-assumptions is evaluated using experimental HAADF STEM focal-series. It is found that the contrast contained in each image of the focal-series is accurately described by the convolution of a focus-invariant 2D object with a 2D optical-transfer function (OTF) which describes the illumination at the focus value used for imaging.

Annular bright field (ABF) detectors have been developed in the last few years allowing the direct imaging of low-Z atoms from oxygen down to hydrogen. These types of detectors are now available as standard attachments for the latest generation of top-end electron microscopes. However these systems cannot always be installed in previous generation microscopes. In this paper we report the preliminary results of an in-house implementation of a ABF detection system on a CEOS aberration corrected JEOL 2200FS STEM. This has been obtained by exploiting the standard BF detector coupled with a high vacuum compatible, X-ray tight and retractable shadowing mechanism. This results in the acquisition of near zero-angle scattered electrons with inner collection semi-angle from 2.0 mrad to 23 mrad and outer semi-angle in the range from 3.0 mrad to 35 mrad. The characteristics and performances of this ABF detection system are discussed.

We present a practical approach to quantify the annular dark field (ADF) detector in scanning transmission electron microscope (STEM). The non-uniform response of the detector as a function of the beam current is investigated. The brightness and contrast of the preamplifier have been taken into account to find the black level of the detector. The efficiency map is obtained.

Recording HAADF STEM data on an absolute scale for image quantification is becoming increasingly common. A particular challenge with this method is that most image simulation programs model the detector as being circularly symmetric and exhibiting uniform detection sensitivity across its entire active region. For a real detector this is rarely the case; it then becomes vital to understand how far one's detector deviates from the ideal. Here we investigate a collection of detector maps recorded using hardware from each of the current major manufacturers. Using these maps we compare their different asymmetries and any non-uniformities in their sensitivity. To facilitate this we define the parameters; 'flatness', 'roundness', 'smoothness' and 'ellipticity', evaluate each hardware with respect to these and rank them.

We describe an algorithm to reconstruct the electron exit wave of a weak-phase object from single diffraction pattern. The algorithm uses analytic formulations describing the diffraction intensities through a representation of the object exit wave in a Gaussian basis. The reconstruction is achieved by solving an overdetermined system of non-linear equations using an easily parallelisable global multi-start search with Levenberg-Marquard optimisation and analytic derivatives.

We have developed a high resolution STEM imaging method using accelerating beam voltages of 30 kV and less. In this study, we examined and determined the low accelerating voltage parameters necessary for obtaining lattice resolution in STEM images, using the cold field emission scanning electron microscope (CFE-SEM), Hitachi SU9000. We also investigated and optimized the objective lens conditions for optimum lattice fringe imaging. The STEM images and associated Fourier transform image obtained at 30 kV show the Si (222) lattice fringes and reflection spots, corresponding to the d-lattice spacing of 0.157 nm. The STEM images and associated Fourier transform image at 15 kV show the Si (111) lattice fringes and reflection spot, corresponding to the d-lattice spacing of 0.314 nm.

Electron tomography (ET) is an increasingly important technique for examining the three-dimensional morphologies of nanostructures. ET involves the acquisition of a set of 2D projection images to be reconstructed into a volumetric image by solving an inverse problem. However, due to limitations in the acquisition process this inverse problem is considered ill-posed (i.e., no unique solution exists). Furthermore reconstruction usually suffers from missing wedge artifacts (e.g., star, fan, blurring, and elongation artifacts). Compressed sensing (CS) has recently been applied to ET and showed promising results for reducing missing wedge artifacts caused by limited angle sampling. CS uses a nonlinear reconstruction algorithm that employs image sparsity as a priori knowledge to improve the accuracy of density reconstruction from a relatively small number of projections compared to other reconstruction techniques. However, The performance of CS recovery depends heavily on the degree of sparsity of the reconstructed image in the selected transform domain. Prespecified transformations such as spatial gradients provide sparse image representation, while synthesising the sparsifying transform based on the properties of the particular specimen may give even sparser results and can extend the application of CS to specimens that can not be sparsely represented with other transforms such as Total variation (TV). In this work, we show that CS reconstruction in ET can be significantly improved by tailoring the sparsity representation using a sparse dictionary learning principle.

Transmission electron microscopy images of insulin-producing beta cells in the islets of Langerhans contain many complex structures, making it difficult to accurately segment insulin granules. Furthermore the appearance of the granules and surrounding halo and limiting membrane can vary enormously depending on the methods used for sample preparation. An automated method has been developed using active contours to segment the insulin core initially and then expand to segment the halos [1]. The method has been validated against manual measurements and also yields higher accuracy than other automated methods [2]. It has then been extended to three dimensions to analyse a tomographic reconstruction from a thick section of the same material. The final step has been to produce a GUI and use the automated process to compare a number of different electron microscopy preparation protocols including chemical fixation (where many of halos are often distended) and to explore the many subtleties of high pressure freezing (where the halos are often minimal, [3]).

A monochromator we have introduced is improving the attainable energy resolution of electron energy loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM) by more than 2x relative to what has been available until recently. Here we briefly review the design and the performance attained so far. We then investigate the ultimate resolution limits of our system and show that it should be able to reach an energy resolution of <10 meV.

Electron microscopy was applied to the study of 1 billion-year-old microfossils from northwest Scotland in order to investigate their 3D morphology and mode of fossilization. 3D-FIB-SEM revealed high quality preservation of organic cell walls with only minor amounts of post-mortem decomposition, followed by variable degrees of morphological alteration (folding and compression of cell walls) during sediment compaction. EFTEM mapping plus SAED revealed a diverse fossilizing mineral assemblage including K-rich clay, Fe-Mg-rich clay and calcium phosphate, with each mineral occupying specific microenvironments in proximity to carbonaceous microfossil cell walls.

We have investigated the use of x-ray energy dispersive spectroscopy during tomographic hyperspectral imaging experiments in the scanning transmission electron microscope. In this work, we have found that for an analytical system employing a commercial high-tilt tomography holder the measured x-ray signal is limited by shadowing caused by the penumbra of the holder relative to the x-ray detector system. This limits the ability to perform quantitative, elemental tomographic analysis.

For researchers in metallurgy, energy storage or functional nanomaterials, where elemental distribution is crucial to performance, full characterization is more difficult by decreasing feature sizes and increasingly complex architectures. Two-dimensional imaging and analytical techniques often cannot characterize nanostructures completely. A new three-dimensional (3D) tomography technique for STEM XEDS, namely ChemiSTEM^TM Technology [1], reveals the true microstructure of materials offering high X-ray collection efficiency via its windowless detector design, and fast XEDS mapping with tilt response at all angles. ChemiSTEM features the X-FEG and Super X, containing four symmetric detectors for 3D chemical imaging at 0 degree tilt, with significant EDX signal collected under all tilt conditions. The EDS signal of STEM XEDS image tilt series can be processed like normal z-contrast images, because of the monotonic relationship between the EDS signal and the thickness of the TEM foil. Four symmetrically arranged silicon drift detectors (SDD) provide extreme high output count rates (300 kcps) required for acquisition of EDX maps of thick samples, especially on 3 mm disk samples for 3D tomography studies. Examples of 3D chemical mapping using XEDS are given on (InGa)N Nanopyramid LEDs, Ni based super alloy material for turbine blades, dielectric transistor, and catalytic particles. In lithium ion batteries, the elemental segregation of manganese and nickel, which is responsible for the aging of electrode materials made from lithium-nickel-manganese oxide layered nanoparticles was analyzed in 3D XEDS mapping [2].

It is generally regarded as impossible to carry out Auger Electron Spectroscopy (AES) analysis in a scanning electron microscope (SEM) due to the high ambient gas pressure in an SEM. This is because standard electron energy analysers such as the Concentric Hemispherical Analyser (CHA) or Cylindrical Mirror Analyser (CMA) are devices that acquire data in a serial manner that can last up to few minutes. This is considered too slow for high vacuum (10⁻⁶mbar) and a previously cleaned surface would be re-contaminated before a spectrum could be completed. This has led to AES being traditionally carried out under ultrahigh vacuum (UHV) environment. We report on two devices for fast acquisition of AES data characterising nanoscale objects by the use of AES in an SEM.

Oxide dispersion strengthened steels owe part of their high temperature stability to the nano-scale oxides they contain. These yttrium-titanium oxides are notoriously difficult to characterise since they are embedded in a magnetic-ferritic matrix and often <10 nm across. This study uses correlated transmission electron microscopy and atom probe tomography on the same material to explore the kind of information that can be gained on the character of the oxide particles.

The influence of chromium in these alloys is of interest, therefore two model ODS steels Fe-(14Cr)-0.2Ti-0.3Y₂O₃ are compared. TEM is shown to accurately measure the size of the oxide particles and atom probe tomography is necessary to observe the smallest sub-1.5 nm particles. Larger Y₂Ti₂O₇ and Y₂TiO₅ structured particles were identified by high-resolution transmission electron microscopy, but the smallest oxides remain difficult to index. Chemical data from energy-filtered TEM agreed qualitatively with the atom probe findings. It was found that the majority of the oxide particles exhibit an unoxidised chromium shell which may be responsible for reducing the ultimate size of the oxide particles.

A planar shock wave with a peak pressure of 6.2 GPa and duration of 1.7 μs followed by a lateral release wave generates profuse dislocations in single crystalline tantalum. Three orientations [100], [110], [111] were tested to examine the orientation dependence of the dislocation generation. The dislocations were characterised by transmission electron microscopy. The Burgers vectors and morphology of the primary dislocations in the specimens with different orientations showed a distinct orientation dependence and will be discussed in light of the model of slip behaviour in one-dimensional strain of C.S. Smith [1].

Precipitates in Al-Mg-Si alloys with Cu addition (~0.1 wt%) and Zn addition (~1 wt%) were investigated by aberration corrected high angle annular dark field scanning transmission electron microscopy (HAADF-STEM). Most precipitates had no overall unit cell but contained ordered network of Si atomic columns for both the Cu and the Zn containing precipitates. It was found that both Cu and Zn atomic columns are located at specific sites and producing characteristic local configurations on the Si atomic columns.

To achieve optimal mechanical properties in high manganese steels, the precipitation of nanoprecipitates of vanadium and niobium carbides is under investigation. It is shown that under controlled heat treatments between 850°C and 950°C following hot deformation, few-nanometre precipitates of either carbide can be produced in test steels with suitable contents of vanadium or niobium. The structure and chemistry of these precipitates are examined in detail with a spatial resolution down to better than 1 nm using a newly commissioned scanning transmission electron microscope. In particular, it is shown that the nucleation of vanadium carbide precipitates often occurs at pre-existing titanium carbide precipitates which formed from titanium impurities in the bulk steel. This work will also highlight the links between the nanocharacterisation and changes in the bulk properties on annealing.

Oxide Dispersion Strengthened (ODS) reduced activation ferritic steels are promising candidate materials for structural components of both nuclear fission and fusion reactors. However, when irradiated with energetic particles, they may suffer changes on their microstructures that degrade their mechanical performance. In-situ transmission electron microscopy studies on ion-irradiated ODS steels can give remarkable insights into fundamental aspects of radiation damage allowing dynamic observations of defect formation, mobilities, and interactions during irradiation. In this investigation, a commercially available PM2000 ODS steel was in-situ irradiated with 150 KeV Fe⁺ at room temperature and 700°C. These experiments showed that the oxide nanoparticles in these steels remain stable up to the higher irradiation dose (~ 1.5 dpa), and that these particles seem to be effective sinks for irradiation induced defects.

Mg-Zn-Y is a high performance magnesium ternary alloy with high specific strength. A second rare earth element Gd with different content was added into Mg-4.2Zn-0.8Y (at.%) alloys to investigate the effect of Gd addition on the microstructure and mechanical properties. In the as cast alloys, the following phases have been identified: in the Gd-free alloy, an H phase (hcp, a=0.918nm, c=0.95nm), W phase (fcc, a=0.682nm) and icosahedral quasicrystalline phases (i-phase). With 0.5at.% Gd and 1 at.% Gd, W phase, long-period stacking ordered phase (LPSO phase) and i-phase were observed. The coexistence of i-phase and LPSO phase was observed after Gd addition. As the content of Gd increased, the grain size decreased, the volume fractions of second phases increased, and the hardness of the as-cast alloys increased.

Steels for high temperature applications require good creep resistance which is controlled by the chemistry and microstructure of the materials. This paper focuses on the microstructural characterisation of a creep resistant steel using electron microscopy. The existence of various primary carbides, e.g. NbC, M₇C₃ and M₂₃C₆ was confirmed by electron diffraction. The primary chromium carbides transformed from M₇C₃ to M₂₃C₆ during creep while the niobium carbides were nearly unaltered. In addition, secondary precipitates (M₂₃C₆) were observed within the matrix after creep. The size and distribution of the secondary carbides were analysed by a 80 mm² windowless X-Max^N SDD at 3 kV on an SEM. Scanning transmission electron microscopy (STEM) observations showed the appearance of fine NbC, G phase (Ni₁₆Nb₆Si₇) and (Nb, Ti)(C, N) particles.

The microstructure of an X70 alloy and its dislocation development during one cycle of compression/tension strain has been analysed. The microstructure of the as received material and the dislocation arrangements before, during and after the Bauschinger test have been characterised. Results for this particular alloy show no evidence of grain boundary dislocation pile-ups or of precipitates pinning dislocations. A comparison between the dislocation arrangement in the as received, compressed and compressed-tensioned samples shows the formation of small dislocation cells, implying that the conception of the Bauschinger effect comes from dislocation-dislocation interactions.

We observe twin defects on both the (111) and (11-2) planes of thin film Fe₃O₄ using atomically resolved high angle annular dark field (HAADF) STEM imaging. These defects are significant for understanding the previously reported anomalous properties of Fe₃O₄ films as they generate non-bulk bonding configurations leading to non-bulk superexchange interactions in these regions.

Mixed-type [a+c] dislocations can be identified in atomic-resolution high-angle annular dark-field scanning transmission electron microscope images of GaN viewed along [0001] by use of a Burgers loop analysis and by observation of the depth-dependent displacements associated with the Eshelby twist. These dislocations are found to be able to dissociate resulting in a fault that lies perpendicular to the dislocation glide plane. Consideration of the bonding that occurs in such a fault allows the dissociation reaction to be proposed, and the proposed fault agrees with the experimental images when kinks are incorporated into the model.

Despite the significant progress in the area, III-nitride LEDs still suffer from reduced efficiency due to a high dislocation density associated with a lack of suitable growth substrates and strong polarisation fields along the c-axis, the predominant growth direction, resulting in the quantum confined stark effect (QCSE). The novel materials studied here have been developed with the aim of reducing both of these effects and consist of a series of GaN and InGaN layers deposited by chemical vapour deposition on the non-polar, m-plane facets of core structures prepared from c-axis GaN thin films. A dual-beam FIB has been used to prepare a and c-plane sections through these novel structures in order to characterise the defects in the core and non-polar junction using, both diffraction contrast and high resolution, TEM and STEM. The dislocations in the c-axis GaN were generally observed to be confined to this region but the non-polar layers had a high density of defects. The latter include unusual flag type defects which are shown to be comprised of pyramidal dislocations and basal-plane stacking faults, with the Burgers vectors determined via g·b analysis.

Iron-rhodium (FeRh) nanoislands of equiatomic composition have been analysed using scanning transmission electron microscopy (STEM) electron energy loss spec-troscopy(EELS) and high angle annular dark field (HAADF) techniques. Previous magne-tometry results have lead to a hypothesis that at room temperature the core of the islands are antiferromagnetic while the shell has a small ferromagnetic signal. The causes of this effect are most likely to be a difference in composition at the edges or a strain on the island that stretches the lattice and forces the ferromagnetic transition. The results find, at the film-substrate interface, an iron-rich layer ~ 5 Å thick that could play a key role in affecting the magnetostructural transition around the interfacial region and account for the room temperature ferromagnetism.

Nano-structured alloyed materials have been demonstrated with a large improvement of their thermoelectric properties. These improvements have been obtained by tailoring a reduction in the material thermal conductivity. However, such improvements have not yet been demonstrated for bulk materials. Recently, a new approach based on phonon scattering theory has been successfully applied to bulk materials. In this approach, nanoparticles are embedded in a hosting matrix and act as multi-scale phonon scattering centres providing a reduction in the material thermal conductivity. In this work, {CoSi₂ (nanoparticle): SiGe (host)} nanocomposite thermoelectric materials and their precursors for the synthesis were investigated. The purpose of the investigation is to understand the inherent interactions of the nanoparticles with the support material.

Vacuum deposited polymer-nanocomposites (PNCs) comprising alternate layers of metal (Al/Ag) (filler) and polymer (nylon-6) (matrix) have been investigated using chemical, impedance spectroscopy and microstructural characterisation techniques. Electron microscopy investigations revealed the morphology, nanostructure and phases of nano-scale core (metal)-shell (oxide) particles and metallic nano-islands in Al and Ag based PNCs respectively. Evaporation of Al yielded islands of angular core-shell nanoparticles in an Al-oxide/nylon-6 matrix whereas Ag yielded rounded, discrete nanoparticles in nylon-6 matrix. The high particle surface area and an affinity for oxygen formed oxide shells in Al nanoparticles and was critical to charge accumulation and enhanced dielectric behaviour; in contrast, Ag showed little oxidation and less charge accumulation. With an increase in the thickness of the deposited metal layer, Al formed a continuous film of particles whereas Ag condensed to form interconnected nano-islands. This microstructural study is useful in conceptualising better dielectrics based on PNCs.

Rubber composite materials have many applications, one example being tyre manufacture. The presence of a filler material in the composite (such as carbon black or silica) causes its mechanical properties to differ in several ways when compared to pure rubber such as viscoelastic behaviour (the Payne effect), increased tensile strength and improved wear resistance. To fully understand these properties, it is necessary to characterise how the filler material is organised on the nanoscale. Using composite materials representative of those found in tyres, this work illustrates the use of electron tomography and machine learning methods as tools to describe the percolation behaviour of the filler; in this case, we focus on the largest proportion of particles absorbed into one single object as a function of particle spacing.

Ion-beam sputtered amorphous heavy metal oxides, such as Ta₂O₅, are widely used as the high refractive index layer of highly reflective dielectric coatings. Such coatings are used in the ground based Laser Interferometer Gravitational-wave Observatory (LIGO), in which mechanical loss, directly related to Brownian thermal noise, from the coatings forms an important limit to the sensitivity of the LIGO detector. It has previously been shown that heat-treatment and TiO₂ doping of amorphous Ta₂O₅ coatings causes significant changes to the levels of mechanical loss measured and is thought to result from changes in the atomic structure. This work aims to find ways to reduce the levels of mechanical loss in the coatings by understanding the atomic structure properties that are responsible for it, and thus helping to increase the LIGO detector sensitivity. Using a combination of Reduced Density Functions (RDFs) from electron diffraction and Fluctuation Electron Microscopy (FEM), we probe the medium range order (in the 2-3 nm range) of these amorphous coatings.

When examining thin films using transmission electron microscopy (TEM), it is usually necessary to image a cross-section of the film (i.e. parallel to the film). However sometimes it is favourable to image thin films in plan-view (i.e. perpendicular to the film). This is the case for Co-doped FeSi thin films, which possess chiral symmetry along certain zone axes. In order to view these zone axes it is necessary to prepare the films in plan-view. There exist various ways to produce plan-view TEM specimens of thin films, such as back etching, ion milling and mechanical polishing. Here, a method using focused ion beam (FIB) is described in detail. Benefits of using FIB are that it is a quick process, there are no limitations in terms of substrate material, and samples can be produced from sections of substrate/film that may be too small to prepare any other way. The effectiveness of the preparation technique is also discussed here, with some preliminary energy dispersive X-ray (EDX) mapping data.

Resistive switching devices, also called memristors, have attracted much attention due to their potential memory, logic and even neuromorphic applications. Multiple physical mechanisms underpin the non-volatile switching process and are ultimately believed to give rise to the formation and dissolution of a discrete conductive filament within the active layer. However, a detailed nanoscopic analysis that fully explains all the contributory events remains to be presented. Here, we present aspects of the switching events that are correlated back to tunable details of the device fabrication process. Transmission electron microscopy and atomically resolved electron energy loss spectroscopy (EELS) studies of electrically stressed devices will then be presented, with a view to understanding the driving forces behind filament formation and dissolution.

There is interest in improving the detectors used to capture images in transmission electron microscopy. Detectors with an improved modulation transfer function at high spatial frequencies allow for higher resolution in images at lower magnification, which leads to an increased effective field of view. Detectors with improved detective quantum efficiency are important for low dose applications. One way in which these performance enhancements can be achieved is through direct detection, where primary electrons are converted directly into suitable electrical signals by the detector rather than relying on an indirect electron to photon conversion before detection. In this paper we present the characterisation of detector performance for a number of different direct detection technologies, and compare these technologies to traditional indirect detectors. Overall our results show that direct detection enables a significant improvement in all aspects of detector performance.

The maximum out-of-plane field that some thin-film cobalt rings resisted while remaining in the vortex state was found experimentally to be lower than expected from simulation, possibly due to tilt. Analysis of a Zernike phase plate shows that the observed bright outlines around large objects result from the low-spatial-frequency limit of correction imposed by the beam hole. The maximum size of phase object that can be imaged accurately with a Zernike plate can be raised by increasing the effective focal length of the objective lens.

We demonstrate that it is possible to observe depth-dependent atomic displacements in a GaN crystal due to the sufficiently small depth of field achievable in the aberration-corrected scanning transmission electron microscope. The depth-dependent displacements associated with the Eshelby twist of screw dislocations in GaN viewed end on are directly imaged, and makes possible the determination of the sign of the Burgers vector of the dislocation. The experimental results are in good agreement with theoretical images.

Both scanning electron microscopes (SEM) and helium ion microscopes (HeIM) are based on the same principle of a charged particle beam scanning across the surface and generating secondary electrons (SEs) to form images. However, there is a pronounced difference in the energy spectra of the emitted secondary electrons emitted as result of electron or helium ion impact. We have previously presented evidence that this also translates to differences in the information depth through the analysis of dopant contrast in doped silicon structures in both SEM and HeIM. Here, it is now shown how secondary electron emission spectra (SES) and their relation to depth of origin of SE can be experimentally exploited through the use of energy filtering (EF) in low voltage SEM (LV-SEM) to access bulk information from surfaces covered by damage or contamination layers. From the current understanding of the SES in HeIM it is not expected that EF will be as effective in HeIM but an alternative that can be used for some materials to access bulk information is presented.

We experimentally evaluated the signal intensity produced by an electron on three types of scintillators. A powder scintillator showed high efficiency at a low accelerating voltage, whereas a single crystal scintillator showed high efficiency at higher accelerating voltages. On the basis of these characteristics, for a dark-field (DF) scanning transmission electron microscope (STEM), we have developed a new hybrid type scintillator, which consisted of a powder deposited on a single crystal substrate. The luminescent quantum efficiency of the hybrid scintillator was measured to be twice as large as that of the single crystal type detector at 60 kV and was about 8 times higher than that of the powder type detector at 300 kV. The developed detector has advantages of powder and single crystal type detectors, and covers the observation at the accelerating voltages from low to high voltages. Especially, it is useful for low voltage observations of carbon-based materials consisted of few atomic layers that produces weak scattering of electron.

Radiation damage in nuclear grade graphite has been investigated using transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). Changes in the structure on the atomic scale and chemical bonding, and the relationship between each were of particular interest. TEM was used to study damage in nuclear grade graphite on the atomic scale following 1.92×10⁸ electrons nm⁻² of electron beam exposure. During these experiments EELS spectra were also collected periodically to record changes in chemical bonding and structural disorder, by analysing the changes of the carbon K-edge. Image analysis software from the 'PyroMaN' research group provides further information, based on (002) fringe analysis. The software was applied to the micrographs of electron irradiated virgin 'Pile Grade A' (PGA) graphite to quantify the extent of damage from electron beam exposure.

We report exit wave reconstruction using a focal series of low-dose images for ZSM-5, a zeolite which has a wide range of industrial applications. The exit wave phase was successfully reconstructed showing the structure of ZSM-5 at a near-atomic resolution even though the dose in the individual images in the focal series was as low as 26 electrons/Ų. This implementation shows the method's potential for application to other radiation-sensitive materials.

In this contribution, we examine the influence of emitter conditioning for a <111> tungsten cold field emission gun on the emission and beam characteristics of a double aberration corrected electron microscope. By varying the post flash build-up parameters we can control the effective emitter tip radius. A sharp emitter yields an energy resolution of 0.31eV but relatively low beam current whereas an increased tip radius results in a reduction in energy resolution to 0.4eV but much higher potential beam current. Consequently, careful control of the build-up parameters can be used as a means of tailoring the emission to suit specific instrumental requirements.

The LaB₆ cathode has been the brightest thermionic source used in microprobe applications requiring longer lifetime [1-2]. It is x100 lower in brightness than thermal field emitters (TFE) ca Zr/W (100) [3]. There are attractive similarities between these cathodes in terms of work function and operating temperature that are worth considering. Major differences include their respective source sizes (>10μm vs 30nm) and energy spread of 1-2 eV vs 0.6-0.7eV for the LaB₆ and TFE, respectively [4,3].

We report here on the experimental measurement of the energy spread of a LaB₆ cathode operated in the virtual source mode. The cathode used has an end-form measuring 15μm. Total energy spread values obtained using a dedicated electron energy analyser shows values of 0.4eV-0.7eV, significantly lower than typical values in the thermionic mode of 1-2eV.

There are an increasing number of potential applications for nanoparticles in clinical medicine, including targeted drug delivery and contrast agents for biomedical imaging. Current in vitro studies are concerned with the biological impact of nanoparticles, with electron microscopy commonly employed to image their intracellular location. It is critical to quantify the absolute nanoparticle dose internalized by cells in a given exposure, and to understand the factors which affect this. In this work we are aiming to develop a full quantitative description of quantum dot uptake by an in vitro cell line. Transmission electron microscopy of thin cell sections provides the location and number of cellular vesicles per 2-D cell slice plus the number of quantum dots per vesicle. These results can then be correlated to other techniques to quantify the internalized nanoparticle dose distribution for whole cells.

Recent analysis of the bioweathering of minerals has highlighted the challenges for investigating the interface between fungi or bacteria and the surface of the mineral that they live on. Transmission electron microscopy (TEM) with its ability to gather imaging information and collect elemental data at high spatial resolution is the ideal technique to analyse such interfaces. Further to this, a dual beam scanning electron and focused ion beam (FIB) microscope is an ideal instrument to prepare specimens for TEM because of its ability to simultaneously cut through hard and soft materials from specific sites of interest. There are however precautions that must be taken when analysing such mineral systems. The electron beam sensitive nature of most sheet silicate minerals means that consideration has to be made as to whether the structure and/or chemistry of the material is being altered during (S)TEM analysis. Here, results from a study of cyanobacteria grown on the surface of biotite are discussed. Particular reference is given to the methods used to determine an electron beam intensity threshold, below which STEM-EDX analysis could be performed without detrimental alteration to the mineral.

Nanoparticles are used in industry for personal care products and the preparation of food. In the latter application, their functions include the prevention of microbes' growth, increase of the foods nutritional value and sensory quality. EU regulations require a risk assessment of the nanoparticles used in foods and food contact materials before the products can reach the market. However, availability of validated analytical methodologies for detection and characterisation of the nanoparticles in food hampers appropriate risk assessment. As part of a research on the evaluation of the methods for screening and quantification of Ag nanoparticles in meat we have tested a new TEM sample preparation alternative to resin embedding and cryo-sectioning. Energy filtered TEM analysis was applied to evaluate thickness and the uniformity of thin meat layers acquired at increasing input of the sample demonstrating that the protocols used ensured good stability under the electron beam, reliable sample concentration and reproducibility.

Biomedical application of engineered nanoparticles (NPs) is a growing area of research and development. Uncertainty remains as to the mode of action of many NP types and TEM is a tool capable of addressing this if used in conjunction with standard cellular response assays. We will demonstrate imaging of thin sections of fixed, plastic embedded cells by analytical TEM to identify: superparamagnetic iron oxide NP translocation into cell compartments such as endosomes; amorphous silica NP penetration through a cell membrane without membrane encapsulation and zinc oxide NP degradation in cell compartments. We will then discuss how the in vitro cellular responses to a dose of NPs exposed to cell lines can be correlated to the internalized dose per cell section noting however that quantification of the latter requires random sampling procedures or correlation to higher throughout techniques to measure a population of whole cells. Similarly, analytical TEM measures of NP degradation within intracellular compartments will require a more appropriate sample preparation such as cryo-fixation.

CoCrMo alloys are utilised as the main material in hip prostheses. The link between this type of hip prosthesis and chronic pain remains unclear. Studies suggest that wear debris generated in-vivo may be related to post-operative complications such as inflammation. These alloys can contain different amounts of carbon, which improves the mechanical properties of the alloy. However, the formation of carbides could become sites that initiate corrosion, releasing ions and/or particles into the human body. This study analysed the mechanical milling of alloys containing both high and low carbon levels in relevant biological media, as an alternative route to generate wear debris. The results show that low carbon alloys produce significantly more nanoparticles than high carbon alloys. During the milling process, strain induces an fcc to hcp phase transformation. Evidence for cobalt and molybdenum dissolution in the presence of serum was confirmed by ICP-MS and TEM EDX techniques.

We report the use of the electron energy loss spectroscopy (EELS) for providing light element chemical composition information from organic, crystalline pharmaceutical materials including theophylline and paracetamol and discuss how this type of data can complement transmission electron microscopy (TEM) imaging and electron diffraction when investigating polymorphism. We also discuss the potential for the extraction of bonding information using electron loss near-edge structure (ELNES).

A new method of quantifying the HAADF STEM signal on absolute scale, building on the z-contrast nature of the technique, has been developed to address the problem of characterising nanoparticles to an atomic scale. Experimental images are scaled to a fraction of the incident beam intensity from a detector map. The integrated intensity of each individual atomic column is multiplied by the pixel area yielding a more imaging-parameter robust quantity, termed a scattering cross-section. Using this cross-section approach, and simulated reference data we show how it is possible to count the number of atoms in individual columns, in order to compare against theoretical 3-dimensional structures. All this is with the aim of trying to obtain as much information as possible from a single image of these beam sensitive samples.

The hydrothermal synthesis of Fe₃O₄ nanoparticles (NPs) (< 50 nm) from mixed FeCl₃ / FeCl₂ precursor solution at pH ~ 12 has been confirmed using complementary characterisation techniques of transmission electron microscopy and X-ray diffractometry. Off-axis electron holography allowed for visualisation of their single domain (SD) nature, as well as inter-particle interactions, with the latter attributed to explain the pseudo-SD/multi-domain behaviour demonstrated by bulk magnetic measurements.

The development of efficient thin film solar cells requires a deep knowledge of the nanoscale morphology of the active layers. While conventional investigation is usually limited to 2D information, here we use electron tomography to unravel a complex particle network in a non-ambiguous, 3D reconstruction. We present our study of a dye sensitised solar cell, based on a nanostructured TiO₂ photoanode produced by pulsed laser deposition (PLD) and displaying a hierarchical, quasi-1D arrangement. We prepare the sample for electron tomography using focused ion beam (FIB) milling to obtain a micro-pillar, instead of a conventional TEM lamella. This approach has the advantage of allowing higher quality tomographic reconstructions of complex morphologies due to the increased tilt range available and the constant thickness of the section. We analyse the resulting reconstruction to quantitatively investigate the geometry of the TiO₂ network. We compare the findings with a photoanode based on a conventional TiO₂ paste, determining the anisotropy of the PLD-grown film. To complement our nanoscale TEM characterization, we also employ FIB tomography, to obtain a complete structural characterisation of the photoanode at different length scales.

In recent years, the information retrieval of three-dimensional (3D) intensity distribution in reciprocal space has attracted much attention in nanometrology research. However, the development of 3D analysis of electron diffraction intensity including crystal structural identification and morphology determination of nanocrystals have so far focused on single crystalline nano-objects. Using boron carbide five-fold twinned nanowires as a model system for nanostructured nano-objects, we demonstrated that such method can also identify the internal structure of cyclic twinned nanostructures. Here, the methodology of the 3D mapping of electron diffraction from such nanowires will be presented and the approach is compared with the conventional method of axial rotation electron diffraction analysis to demonstrate its comprehensive, quantitative and non-destructive nature. We believe that such approach can be easily extended to the investigation of internal structures of other polycrystalline nanostructures.

Whilst the use of microscopic techniques to determine the size distributions of nanoparticle samples is now well established, their characterisation challenges extend well beyond this. Here it is shown how high resolution electron microscopy can help meet these challenges. One of the key parameters is the determination of particle shape and structure in three dimensions. Here two approaches to determining nanoparticle structure are described and demonstrated. In the first scanning transmission electron microscopy combined with high angle annular dark field imaging (HAADF-STEM) is used to image homogenous nanoparticles, where the contrast is directly related to the thickness of the material in the electron beam. It is shown that this can be related to the three dimensional shape of the nano-object. High resolution TEM imaging, combined with fast Fourier transform (FFT) analysis, can determine the crystalline structure and orientation of nanoparticles as well as the presence of any defects. This combined approach allows the physical structure of a significant number of nano-objects to be characterised, relatively quickly.

Microwave-irradiation (MW) synthesis of nanostructured materials provides for the synthesis of metal nanoparticles, using fast and uniform heating rates. This procedure affords better control of the shape and size of the nanoparticles when compared to conventional methods. In this work, microwave-irradiation was used to produce platinum-cobalt (Pt-Co) and platinum-nickel (Pt-Ni) nanoparticles for use as electrocatalysts in the methanol oxidation reaction. High resolution TEM imaging and EELS studies revealed that these bimetallic nanoparticles form islands or hetero-structures.

A new form of carbon is described, which consists of hollow, three-dimensional shells bounded by bilayer graphene. The new carbon is produced very simply, by passing a current through graphite rods in a commercial arc-evaporation unit. Characterisation of the carbon using high resolution transmission electron microscopy is described, and the possible formation mechanism discussed.

Nano-beam electron diffraction (NBD) has been used in addition to HAADF-STEM and HRTEM analyses of Pd-Al₂O₃ and Pt-Al₂O₃ catalysts. NBD and its STEM nanodiffraction counterpart are not widely used for nanoparticle catalysts but the more common SAD method does not offer the same level of structural information for individual ultrafine (< 10 nm) nanoparticles, even with aberration correction. Here, NBD has been applied to commercially relevant catalysts for added information and to investigate defect structures in sintered particles.

A greater understanding of multiple exciton generation in heterostructured colloidal quantum dots can be achieved through detailed modelling, and used to optimise their design for solar cell applications. However, such modelling requires an accurate knowledge of the physical structure of the quantum dots. Here we report the use of high angle annular dark field (HAADF) scanning transmission electron microscope (STEM) imaging to study the size and shape of CdSe/CdTe/CdS type II quantum dots at each of the three stages of their synthesis.

Hexagonal Boron Nitride (h-BN) is a promising insulating material to complement and enable graphene electronics. Given the good lattice match to graphite, graphene/h-BN heterostructures may be grown with negligible amounts of strain and defect states, resulting in high carrier mobilities approaching values for suspended graphene. Chemical vapour deposition (CVD) has emerged as one of the preferred routes for the synthesis of 2D materials for electronic applications. Here we report on the growth of h-BN by low pressure CVD, using borazine as a precursor. Electron backscattered diffraction (EBSD) in conjunction with topographic imaging in the scanning electron microscope are used to investigate the change in crystal structure and orientation of three metallic catalyst substrates: Co, Ni and Cu, by high temperature processing and the growth of nanoscale h-BN domains. The behaviour of the metal foils is interpreted in light of the prevalent growth models. EBSD and imaging conditions are optimized to allow efficient acquisitions for these composite and nanostructured specimens.

Hybrid solar cells based on 1,2 methanofullerene (C₆₁) capped CdSe and poly (3-hexylthiophene) (P3HT) were been investigated through a range of techniques. High resolution transmission electron microscopy (HRTEM) was used to characterize size, morphology and crystal structure of as-grown and C₆₁-capped CdSe quantum dots. Cross sectional lamellar specimens were prepared from full photovoltaic devices using a focused ion beam milling approach. The sections were analysed by high angle annular dark field imaging in scanning TEM mode to determine the morphology of the device, in particular the intermixing of P3HT and capped quantum dots.

Over time, the performance of lubricating oil in a diesel engine is affected by the build-up of carbon soot produced by the combustion process. TEM and HRTEM are commonly used to investigate the characteristics of individual and agglomerated particles from diesel exhaust, to understand the structure and distribution of the carbon sheets in the primary particles and the nanostructure morphology. However, high resolution imaging of soot-in-oil is more challenging, as mineral oil is a contaminant for the electron microscope and leads to instability under the electron beam. In this work we compare solvent extraction and centrifugation techniques for removing the mineral oil contaminant, and the effect on particle size distribution.

A series of thermally mediated dynamic (in situ) experiments in the transmission electron microscope (TEM) have been performed, in order to obtain improved understanding and control of the ripening and migration processes of gold nanoparticles on multi-wall carbon nanotubes (MWNTs). In particular, post-heating tomography was used to appraise the resultant dispersion of the nanoparticles within these three-dimensional (3D) composite structures.

This project is concerned with enhancing photocatalytic activity by preparing a mixed phase of nano-sized TiO₂. TiO₂ thin films were synthesized by using Low Pressure Chemical Vapour Deposition (LPCVD). Titanium isopropoxide and N₂ gas were used as the precursor and carrier gas respectively. The effects of reaction temperature, carrier gas flow rate and deposited area were studied. TiO₂ thin films with nano-sized TiO₂ particles were obtained under suitable conditions and SEM, TEM, powder XRD and Raman spectroscopy were employed to characterize the phase and physical appearance of synthesized materials. Preliminary results show that a dual phase (TiO₂(B) and anatase) thin film nanopowder was successfully prepared by LPCVD with needle- and polygonal plate-shape crystallites respectively. This thin film deposit produced a preferred orientation of TiO₂(B) needles in the [001] direction of average crystallite size 50-80 nm in length and 5-10 nm in width, whilst the crystallite size of anatase polygonal-plates was around 200 nm. The optimal LPCVD condition for preparing this mixed phase of TiO₂ was 600°C with a 1 mL/s N₂ flow rate.

Aligned ZnO nanorods were grown on titanium (Ti) substrate by simple and facile thermal evaporation process using high purity metallic zinc powder in the presence of oxygen. The grown nanorods were studied in terms of their morphological, structural and field emission properties by using different analytical tools such as field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The field emission properties of the as-grown aligned ZnO nanorods were also investigated which resulted in a turn-on field of ~2.65 kV. This research demonstrates that simply prepared ZnO nanorods can be used for field emission device applications.

This paper reports on the direct growth of In-doped ZnO nanopencils on Si substrate by facile thermal evaporation process using metallic zinc and In powders in the presence of oxygen. The as-grown nanostructures were examined in detail in terms of their morphological, structure and field emission properties. The morphological studies, carried out by FESEM, exhibited that the grown structures possess homogeneous morphologies with pointed tips similar to pencils. The typical tip diameters of as-synthesized nanopencils are in the range of ~13 ± 3 nm which reflects that these nanopencils could be a promising candidate for field emission applications. The detailed structural properties revealed that the prepared nanopencils are well-crystalline and possessing wurtzite hexagonal phase. For application view point, the field emission properties of as-grown In-doped ZnO nanopencils were examined which exhibited a very low turn-on voltage of 1.3 kV.

Two-dimensional (2D) materials, graphene, hexagonal boron nitride (h-BN) and transition metal dichalcogenides (TMD) have been investigated by means of Scanning Transmission Electron Microscopy (STEM), in particular via High Angle Annular Dark Field (HAADF) imaging technique. They are compared in terms of their structure and durability under intense electron beams.

Palladium atoms have been deposited onto graphene where they catalyse etching processes in conjunction with the e-beam, during/after which they reside at the edges of the holes, which have formed in the graphene. Energy filtered imaging reveals that the low loss feature at 2-4 eV constituting the shoulder of the graphene n-plasmon, is up to 10 times enhanced at Pd-decorated graphene edges compared to clean monolayer graphene, rendering it a useful feature for electric field enhancement applications in the optical regime

High Angle Annular Dark Field Scanning Transmission Electron Microscope (HAADF-STEM) has been employed for the study of thermal effects of structural transformation of AuPd nanoparticles produced by physical vapour deposition. Depending on the duration of annealing at a temperature of 500 K, atomic resolved imaging analysis reveals the formation of various structure morphologies from the ordered L1₂ superlattice to the core-shell structure. The effects of Pd-oxides are also discussed.

A method for probing the electrical and structural characteristics of individual as-grown III-V nanowires was studied. In-situ electrical characterization was performed in a focused ion beam / scanning electron microscopy system by using a fine nano-manipulator and ion beam assisted deposition. Transmission electron microscopy specimens of probed nanowires are prepared afterwards. This method would potentially allow the correlation of electrical and structural characteristics (e.g. crystal faults such as twinning) of the nanowire-substrate system. The challenge is in contacting the nanowires so that the electrical characteristics of the nanowire-substrate system can be extracted correctly.