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The aim of this work is to make progress towards the development of 3D reconstruction as a legitimate alternative to traditional 2D characterisation of soot. Time constraints are the greatest opposition to its implementation, as currently reconstruction of a single soot particle takes around 5-6 hours to complete. As such, the accuracy and detail gains are currently insufficient to challenge 2D characterisation of a representative sample (e.g. 200 particles). This work is a consideration of the optimisation of the steps included within the computational reconstruction and manual segmentation of soot particles. Our optimal process reduced the time required by over 70% in comparison to a typical procedure, whilst producing models with no appreciable decrease in quality.

The preparation of thinned lamellae from bulk samples for transmission electron microscopy (TEM) analysis has been possible in the focussed ion beam scanning electron microscope (FIB-SEM) for over 20 years via the in situ lift-out method. Lift-out offers a fast and site specific preparation method for TEM analysis, typically in the field of materials science. More recently it has been applied to a low-water content biological sample (Rubino 2012). This work presents the successful lift-out of high-water content lamellae, under cryogenic conditions (cryo-FIB lift-out) and using a nanomanipulator retaining its full range of motion, which are advances on the work previously done by Rubino (2012). Strategies are explored for maintaining cryogenic conditions, grid attachment using cryo-condensation of water and protection of the lamella when transferring to the TEM.

© 2014 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Room temperature electroluminescence from semiconductor junctions is demonstrated. The junctions are fabricated by the exfoliation and direct mechanical adhesion of InSe and GaSe van der Waals layered crystals. Homojunction diodes formed from layers of p- and n-type InSe exhibit electroluminescence at energies close to the bandgap energy of InSe (Eg = 1.26 eV). In contrast, heterojunction diodes formed by combining layers of p-type GaSe and n-type InSe emit photons at lower energies, which is attributed to the generation of spatially indirect excitons and a staggered valence band lineup for the holes at the GaSe/InSe interface. These results demonstrate the technological potential of mechanically formed heterojunctions and homojunctions of direct-bandgap layered GaSe and InSe compounds with an optical response over an extended wavelength range, from the near-infrared to the visible spectrum. Room temperature electroluminescence from van der Waals layered semiconductor junctions is demonstrated. The junctions are fabricated by exfoliation and direct mechanical adhesion. These heterostructures are based on direct-bandgap III-VI layered crystals and have atomically flat interfaces, a well-defined band lineup, and a broad optical response from the near-infrared to the visible spectral range.

Gallium (Ga) helps solubilize rare-earth ions in chalcogenide glasses, but has been found to form the dominant crystallizing selenide phase in bulk glass in our previous work. Here, the crystallization behavior is compared of as-annealed 0–3000 ppmw Dy3+-doped Ge–As–Ga–Se glasses with different Ga levels: Ge16.5As(19−x)GaxSe64.5 (at.%), for x = 3 and 10, named Ga3 and Ga10 glass series, respectively. X-ray diffraction and high-resolution transmission electron microscopy are employed to examine crystals in the bulk of the as-prepared glasses, and the crystalline phase is proved to be the same: Ge-modified, face centered cubic α-Ga2Se3. Light scattering of polished glass samples is monitored using Fourier transform spectroscopy. When Ga is decreased from 10 to 3 at.%, the bulk crystallization is dramatically reduced and the optical scattering loss decreases. Surface defects, with a rough topology observed for both series of as-prepared chalcogenide glasses, are demonstrated to comprise Dy, Si, and [O]. For the first time, evidence for the proposed nucleation agent Dy2O3 is found inside the bulk of as-prepared glass. This is an important result because rare-earth ions bound in a high phonon–energy oxide local environment are, as a consequence, inactive mid-infrared fluorophores because they undergo preferential nonradiative decay of excited states.

Interactions of free-standing gold nanoparticles and hollow graphitized nanofibers in colloidal suspension are investigated, revealing the first example of the controlled arrangement of nanoparticles inside nano-containers, as directed by their internal structure. The ordering is highly effective for small gold nanoparticles whose sizes are commensurate with the height of graphitic step-edges in the graphitized carbon nanofibers and is less effective for larger gold nanoparticles. Studies aimed at understanding the role of the organic-solvent surface tension, employed for the filling experiments, demonstrate that gold nanoparticles become preferentially anchored into the hollow graphitized carbon nanofibers under a mixture of pentane/CO 2 in supercritical conditions. It is shown that a three-step cleaning procedure enables effective removal of gold nanoparticles adsorbed on the exterior surface of graphitized carbon nanofibers, while ordered arrays of encapsulated nanoparticles are retained. Interactions of gold nanoparticles and hollow graphitized nanofibers reveal the first example of the controlled arrangement of nanoparticles inside carbon nano-containers. The ordering is directed by the graphitic step-edges in the nanofibers. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

We report the photovoltaic response of solid-state devices based on porous TiO 2 photosensitized with PbS nanocrystals. A photovoltaic response in the visible and near infrared wavelength range is obtained by exploiting the Schottky junction that forms at the interface between the PbS/TiO 2 film and a metallic contact. Spatial images of the photoluminescence and of the short circuit photocurrent signal reveal a non-homogeneous response, which we explain in terms of the electron transfer dynamics at the PbS/TiO 2 interface and the morphological properties of TiO 2. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The application of chemical microanalysis techniques to profile the reaction pathways of metallic diffusion couple ohmic contacts to AlGaN/GaN field effect transistors and to appraise the influence of As on the development of GaN heterostructures grown by plasma assisted molecular beam epitaxy is illustrated. 30 nm of Ti within AuPdAlTi contacts is necessary for TiN formation and contact activation following rapid thermal annealing at 950 °C, whilst the supply of excess Ti leads to over-development of the contact and consumption of the AlGaN layer. The presence of As during GaN growth leads to the development of a high density of cubic GaN stacking disorders. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

AuTiAlTi and AuPdAlTi contacts to AlGaN/GaN, rapid thermal annealed at temperatures ranging from 650 to 950 °C have been investigated using conventional and chemical TEM analysis. Ohmic behaviour was seen for AuTiAlTi contacts annealed at 750 °C or higher and in AuPdAlTi contacts annealed at 850 °C or higher. The formation of interfacial TiN after anneals at high temperatures is required to activate the contact. At anneals of 950 °C, the samples show a structure of TiN grains within an interfacial band, with TiN inclusions into the AlGaN preceded by an Al–Au diffusion front. The presence of these inclusions does not appear to have any effect on the resistivity of the contact. Neither Ti nor Pd diffusion barriers have prevented the interdiffusion of Au through the Al and Ti contact layers. The implication is that the presence of Au mediates the formation of TiN at the annealing temperatures used in these samples.

The use of boron nitride nanotubes as effective nanoscale containers for the confinement and thermal transformations of molecules of C60-fullerene has been demonstrated. The gas-phase insertion of fullerenes into the internal channel of boron nitride nanotubes yields quasi-one-dimensional arrays, with packing arrangements of the guest-fullerenes different to those in the bulk crystal and critically dependent on the internal diameter of the host-nanotube. Interestingly, the confined fullerene molecules (i) exhibit dynamic behaviour and temperature-dependant phase transitions analogous to that observed in the bulk crystal and (ii) can be effectively removed from within the internal channel of nanotubes by excessive sonication in organic solvent, indicating weak host-guest interactions. The thermal treatment of fullerenes confined within nanotubes at 1200 °C in argon triggers the polymerisation and coalescence of the guest-fullerenes into carbon nanotubes inside boron nitride nanotubes affording a hybrid nanostructure – the world’s smallest coaxial cable – on a preparative scale, as confirmed by high resolution bright field transmission electron microscopy (TEM) imaging and electron energy loss spectroscopy, energy filtered transmission electron microscopy (EELS, EFTEM) elemental mapping and UV-vis absorption spectroscopy.