Abstract: Publication date: Available online 2 April 2019Source: Advances in Imaging and Electron PhysicsAuthor(s): Clifford M. KrowneAbstractWith the advent of the metal–insulator transition (MIT) as a tool for adjusting the properties of lower dimensions materials, with nanoscale dimensions in one or more of the coordinate directions, it is worthwhile to derive analytical formulas for the electronic energy in k-space, for a generic two-dimensional hexagonal lattice as a prelude for their use in nanoscopic transport devices (using the MIT) or other solid state devices. This is done in the tight binding (TB) approximation, since it allows a tractable analytical development, with some refinements possible. This lattice structure is applicable to many 2D materials like graphene, BN, MoS2, and many others. This chapter treats the governing equation when the onsite sublattice energies differ (Section 10.1), examines the Hamiltonian for the two atom system (Section 10.2), evaluates the normalized BB self-energy matrix element (Section 10.3), finds Hamiltonian and governing equation with pivoting element unity (Section 10.4), solves the governing equation for eigenvectors and eigenenergies (Section 10.5), determines the eigenenergy when extracted from its governing equation form (Section 10.6).

Abstract: Publication date: Available online 2 April 2019Source: Advances in Imaging and Electron PhysicsAuthor(s): Ian MacLaren, Rebecca B. Cummings, Fraser Gordon, Enrique Frutos-Myro, Sam McFadzean, Andrew P. Brown, Alan J. CravenAbstractAn overview of recent progress in high loss electron energy loss spectroscopy is presented. This covers the instrumental aspects of how to best set up a scanning transmission electron microscope and post-column spectrometer combination to provide best performance, a survey of a range of results that are possible in EELS with a good setup, and a brief investigation of the current limitations imposed by the current mainstream detector technology. In the first section, detailed consideration is given to the coupling optics between microscope and spectrometer, the effects on the EELS spectrum, the need for spectrometer refocusing, and the problems with gun anodes in some field emission gun designs. In the second section, a survey of the absolute cross sections for the L edges of 4d transition elements is set out, these are used for absolute quantification in two cases, and the extended energy loss fine structure beyond the Si–K edge is used for atomic structure investigation. The final section comprises an investigation of noise levels on the Rh L3 edge with a standard CCD detector in the spectrometer with a comparison to simulated shot noise, and shows that in this case, RMS noise was 7 times worse than the fundamental limit, illustrating clearly how much improvement would be possible with electron counting detectors.

Abstract: Publication date: Available online 2 April 2019Source: Advances in Imaging and Electron PhysicsAuthor(s): Clifford M. KrowneAbstractWith the advent of the metal–insulator transition (MIT) as a tool for adjusting the properties of lower dimensions materials, with nanoscale dimensions in one or more of the coordinate directions, it is worthwhile to derive analytical formulas for the electronic energy in k-space, for a generic two-dimensional hexagonal lattice as a prelude for their use in nanoscopic transport devices (using the MIT) or other solid state devices. This is done in the tight binding (TB) approximation, since it allows a tractable analytical development, with some refinements possible. This lattice structure is applicable to many 2D materials like graphene, BN, MoS2, and many others. This last chapter gives a summary of what the chapters in this series have covered. Besides the introduction (Chapter 1), those chapters included a determination of the reciprocal space lattice from knowledge of the direct space in 2D and 3D (Chapter 2), the tight-binding (TB) formulation of the electronic band structure for hexagonal crystals using an appropriate Hamiltonian (Chapter 3), evaluation of the matrix elements from the Hamiltonian in the TB method (Chapter 4), solving the secular equation of the system for eigenenergy (Chapter 5), properties of the eigenenergy as a function of k vector (Chapter 6), the Hamiltonian of the two atom sublattice system (Chapter 7), 2- and 4-spinor wavefunctions and Hamiltonians (Chapter 8), the relativistic Dirac equation and its attributes (Chapter 9), and solution of the system for differing onsite atom energies (Chapter 10).

Abstract: Publication date: Available online 2 April 2019Source: Advances in Imaging and Electron PhysicsAuthor(s): Clifford M. KrowneAbstractWith the advent of the metal–insulator transition (MIT) as a tool for adjusting the properties of lower dimensions materials, with nanoscale dimensions in one or more of the coordinate directions, it is worthwhile to derive analytical formulas for the electronic energy in k-space, for a generic two-dimensional hexagonal lattice as a prelude for their use in nanoscopic transport devices (using the MIT) or other solid state devices. This is done in the tight binding (TB) approximation, since it allows a tractable analytical development, with some refinements possible. This lattice structure is applicable to many 2D materials like graphene, BN, MoS2, and many others. This chapter treats the relativistic energy expression (Section 9.1), the Dirac conditions obtained from linear energy representation and its Hamiltonian (Section 9.2), the allowable αi and β Dirac matrices (Section 9.3), choosing specific αi and β sets and their satisfaction of the Dirac conditions (Section 9.4), the non-uniqueness of the Dirac matrices and their transformations (Section 9.5), the Dirac equation (Section 9.6), the plane wave form of the Dirac equation (Section 9.7), eigenvalues of the plane wave Dirac equation (Section 9.8), eigenvectors of the plane wave Dirac equation and comparison to graphene eigenvectors (Section 9.9), spinor eigenvectors with transverse momentum plane wave Dirac equation (Section 9.10), transforming from one Dirac matrix set to another (Section 9.11), and the transformed plane wave Dirac equation for transverse momentum (Section 9.12).

Abstract: Publication date: Available online 2 April 2019Source: Advances in Imaging and Electron PhysicsAuthor(s): Clifford M. KrowneAbstractWith the advent of the metal–insulator transition (MIT) as a tool for adjusting the properties of lower dimensions materials, with nanoscale dimensions in one or more of the coordinate directions, it is worthwhile to derive analytical formulas for the electronic energy in k-space, for a generic two-dimensional hexagonal lattice as a prelude for their use in nanoscopic transport devices (using the MIT) or other solid state devices. This is done in the tight binding (TB) approximation, since it allows a tractable analytical development, with some refinements possible. This lattice structure is applicable to many 2D materials like graphene, BN, MoS2, and many others. This chapter reviews 2-spinors (Section 8.1), builds 4-spinors using a reordered wavefunction and a restructured Hamiltonian (Section 8.2), looks at eigenenergies and eigenfunctions obtained using 4-spinors (Section 8.3), and obtains eigenenergies based on 4-spinors under an approximation (Section 8.4).

Abstract: Publication date: Available online 2 April 2019Source: Advances in Imaging and Electron PhysicsAuthor(s): Clifford M. KrowneAbstractWith the advent of the metal–insulator transition (MIT) as a tool for adjusting the properties of lower dimensions materials, with nanoscale dimensions in one or more of the coordinate directions, it is worthwhile to derive analytical formulas for the electronic energy in k-space, for a generic two-dimensional hexagonal lattice as a prelude for their use in nanoscopic transport devices (using the MIT) or other solid state devices. This is done in the tight binding (TB) approximation, since it allows a tractable analytical development, with some refinements possible. This lattice structure is applicable to many 2D materials like graphene, BN, MoS2, and many others. This chapter treats the reduced Hamiltonian of the system with identical atoms in the sublattices (Section 7.1), provides the general solution for the eigenenergy and the eigenvector (Section 7.2), the specialized solution obtained by dropping the next nearest neighbor hopping term (Section 7.3), the low energy, small momentum deviations about the Dirac points (Section 7.4), the phase factor used in the Hamiltonian and eigenfunction at the Dirac points (Section 7.5), the Hamiltonian and eigenenergy about the Dirac points (Section 7.6), band and Dirac point symmetry breaking due to second order q momentum effects (Section 7.7), the density of states near the Dirac points (Section 7.8), the density of states in the vicinity of the electron group velocity approaching zero (Section 7.9), the density of states in vicinity of the electron group velocity zero for finite k (Section 7.10), and the eigenenergy at 1BZ edge at the Van Hove singularity point (Section 7.11).

Abstract: Publication date: Available online 2 April 2019Source: Advances in Imaging and Electron PhysicsAuthor(s): Clifford M. KrowneAbstractWith the advent of the metal–insulator transition (MIT) as a tool for adjusting the properties of lower dimensions materials, with nanoscale dimensions in one or more of the coordinate directions, it is worthwhile to derive analytical formulas for the electronic energy in k-space, for a generic two-dimensional hexagonal lattice as a prelude for their use in nanoscopic transport devices (using the MIT) or other solid state devices. This is done in the tight binding (TB) approximation, since it allows a tractable analytical development, with some refinements possible. This lattice structure is applicable to many 2D materials like graphene, BN, MoS2, and many others. This chapter treats the determination of an arbitrary Hamiltonian and self-matrix elements (Section 4.1), obtaining the secular equation of the system using the Hamiltonian (Section 4.2), finding the nearest neighbor hopping and overlap integrals (Section 4.3), and next nearest neighbor hopping and overlap integrals (Section 4.4).

Abstract: Publication date: Available online 1 April 2019Source: Advances in Imaging and Electron PhysicsAuthor(s): Clifford M. KrowneAbstractWith the advent of the metal–insulator transition (MIT) as a tool for adjusting the properties of lower dimensions materials, with nanoscale dimensions in one or more of the coordinate directions, it is worthwhile to derive analytical formulas for the electronic energy in k-space, for a generic two-dimensional hexagonal lattice as a prelude for their use in nanoscopic transport devices (using the MIT) or other solid state devices. This is done in the tight binding (TB) approximation, since it allows a tractable analytical development, with some refinements possible. This lattice structure is applicable to many 2D materials like graphene, BN, MoS2, and many others. This chapter treats eigenenergy found as an explicit function of k vector (Section 6.1), examines the bands of graphene (Section 6.2), determines the Dirac reciprocal space k points (Section 6.3), and looks at the symmetry property of the eigenenergy (Section 6.4).

Abstract: Publication date: Available online 1 April 2019Source: Advances in Imaging and Electron PhysicsAuthor(s): Clifford M. KrowneAbstractWith the advent of the metal–insulator transition (MIT) as a tool for adjusting the properties of lower dimensions materials, with nanoscale dimensions in one or more of the coordinate directions, it is worthwhile to derive analytical formulas for the electronic energy in k-space, for a generic two-dimensional hexagonal lattice as a prelude for their use in nanoscopic transport devices (using the MIT) or other solid state devices. This is done in the tight binding (TB) approximation, since it allows a tractable analytical development, with some refinements possible. This lattice structure is applicable to many 2D materials like graphene, BN, MoS2, and many others. This chapter treats the exact solution based upon the Hamiltonian matrix elements (Section 5.1), an approximate solution viewing various parameters as possessing orders (Section 5.2), unnormalizing the parameters in eigenenergy (Section 5.3), and unnormalizing the eigenenergy (Section 5.4).

Abstract: Publication date: Available online 1 April 2019Source: Advances in Imaging and Electron PhysicsAuthor(s): Clifford M. KrowneAbstractWith the advent of the metal–insulator transition (MIT) as a tool for adjusting the properties of lower dimensions materials, with nanoscale dimensions in one or more of the coordinate directions, it is worthwhile to derive analytical formulas for the electronic energy in k-space, for a generic two-dimensional hexagonal lattice as a prelude for their use in nanoscopic transport devices (using the MIT) or other solid state devices. This is done in the tight binding (TB) approximation, since it allows a tractable analytical development, with some refinements possible. This lattice structure is applicable to many 2D materials like graphene, BN, MoS2, and many others. The work provided in this volume constitutes a series of eleven chapters, including this one (Chapter 1) followed by nine chapters covering various aspects of the theoretical development, with a closing chapter (Chapter 11) handling overall conclusions.

Abstract: Publication date: Available online 1 April 2019Source: Advances in Imaging and Electron PhysicsAuthor(s): Clifford M. KrowneAbstractWith the advent of the metal–insulator transition (MIT) as a tool for adjusting the properties of lower dimensions materials, with nanoscale dimensions in one or more of the coordinate directions, it is worthwhile to derive analytical formulas for the electronic energy in k-space, for a generic two-dimensional hexagonal lattice as a prelude for their use in nanoscopic transport devices (using the MIT) or other solid state devices. This is done in the tight binding (TB) approximation, since it allows a tractable analytical development, with some refinements possible. This lattice structure is applicable to many 2D materials like graphene, BN, MoS2, and many others. This chapter treats π and σ orbitals in graphene (Section 3.1), the relationship between atomic orbitals and the crystalline wavefunction (Section 3.2), an assessment of the overlap between atomic orbitals (Section 3.3), and the reduction of the spatially varying Schrödinger equation into a solvable system (Section 3.4).

Abstract: Publication date: Available online 1 April 2019Source: Advances in Imaging and Electron PhysicsAuthor(s): Clifford M. KrowneAbstractWith the advent of the metal–insulator transition (MIT) as a tool for adjusting the properties of lower dimensions materials, with nanoscale dimensions in one or more of the coordinate directions, it is worthwhile to derive analytical formulas for the electronic energy in k-space, for a generic two-dimensional hexagonal lattice as a prelude for their use in nanoscopic transport devices (using the MIT) or other solid state devices. This is done in the tight binding (TB) approximation, since it allows a tractable analytical development, with some refinements possible. This lattice structure is applicable to many 2D materials like graphene, BN, MoS2, and many others. This chapter treats 3D analysis of direct and indirect space vectors (Section 2.1), 2D analysis of direct and indirect space vectors (Section 2.2), 2D analysis of first Brillouin zone vertex points (Section 2.3), 2D analysis showing the uniqueness properties of crystallographic K points (Section 2.4), and 2D analysis of the closest atoms for the tight-binding method (Section 2.5).

Abstract: Publication date: 2019Source: Advances in Imaging and Electron Physics, Volume 209Author(s): Jan-Peter AdriaanseAbstractThis article describes the potential use of high temperature superconductors for magnetic lenses. At the time of discovery of these materials, in 1986, they seemed a good candidate for making physically very small lenses at high current densities, while cooling to liquid nitrogen temperatures would be sufficient. The article comprises brief introductions to superconductivity in general and, more specifically, high temperature superconductivity. Furthermore, earlier work on magnetic lenses constructed with “classical superconductors” is summarized. The article continues with an overview of experimental work, aiming at the fabrication of a small superconducting coil/lens from a high temperature superconducting thin film (YBa2Cu3O7−x). Several potential geometries are presented, together with a capacitive technique for alignment of the various elements with respect to each other. Apart from construction related issues, also theoretical optical properties of thin film electron lenses have been calculated. The article concludes with future expectations and suggestions for further research.

Abstract: Publication date: 2019Source: Advances in Imaging and Electron Physics, Volume 209Author(s): Alberto Eljarrat, Sònia Estradé, Francesca PeiróAbstractThe main goal of this work has been to develop quantitative methods for the analysis of materials from low-loss EELS data obtained at the highest spatial and energy resolution. In particular, it has been focused on theoretical and experimental works related to the low-loss EELS of group-III nitride and silicon-based structures. Theoretical work can be divided in two main branches. On one hand, a considerable amount of effort has been put into building a coherent synthesis of the existing formulation of inelastic scattering of electrons by material media. In this sense, the introductory sections of this work, Chapter 1 and also Chapter 2, will hopefully provide the reader with a useful review of the theoretical framework available for the analysis of low-loss EELS. On the other hand, original band structure simulations have been designed and performed using the Wien2k software package.Experimental work has been devoted to the analysis of hyperspectral HAADF-EELS data-sets, acquired on a probe-corrected, monochromated STEM. Data has been analyzed using advanced computational methods, including, to name the most relevant: Model-based analysis of low-loss EELS data, typically through non-linear fitting routines; Kramers–Kronig analysis (KKA) to obtain the complex dielectric function (CDF), and energy-loss function (ELF); calculation of parameters either from raw EELS data, such as the relative thickness (t/λ), or from the CDF, such as absolute thickness (t); and application of advanced multivariate analysis (MVA) algorithms for the factorization of hyperspectral low-loss EELS datasets. Most of these methods have been designed or adapted from the literature to the considered problem. The developed methodologies have been made available through careful descriptions in published works (derived from this work), so that calculations can be reproduced, typically using resources in Hyperspy. Hyperspy is an open-source software repository, designed specifically for EELS, to which a number of contributions have been made in the context of the present work. In the following lines, we summarize the most relevant results of simulations and data analysis of III–V and Si-based materials.

Abstract: Publication date: 2019Source: Advances in Imaging and Electron Physics, Volume 209Author(s): Alberto Eljarrat, Sònia Estradé, Francesca PeiróAbstractIn this chapter, we present a novel analytical strategy, useful in order to probe structural and electronic properties of single silicon nanocrystals (NCs) embedded in a dielectric matrix. We tested this strategy in three systems with different embedding dielectric matrices (SiO2, SiC, and Si3N4). Experiments were performed using a monochromated and aberration corrected Titan low-base microscope, operated at 80 kV to avoid sample damage and to reduce the impact of radiative losses. Then, a novel analysis approach allowed to disentangle the electronic features corresponding to pure Si-NCs from the spectral contribution of the surrounding dielectric materials, trough an appropriate computational treatment of hyperspectral datasets. First, the different materials were identified by measuring the plasmon energy. Notice that due to the overlapping of Si-NCs and dielectric matrix information, the variable shape and position of mixed plasmonic features increases the difficulty for non-linear fitting methods to identify and separate the components in the EELS signal. We managed to solve this problem for the silicon oxide and silicon nitride systems by applying multivariate analysis (MVA) methods that can factorize the hyperspectral datacubes in selected regions. By doing so, the EELS spectra are re-expressed as a function of abundance of Si-NC and dielectric signal components. EELS contributions from the embedded nanoparticles as well as their dielectric surroundings are thus separated, studied, and compared with the crystalline silicon from the substrate and with the dielectric material in the matrix.

Abstract: Publication date: 2019Source: Advances in Imaging and Electron Physics, Volume 209Author(s): Alberto Eljarrat, Sònia Estradé, Francesca PeiróAbstractIn this chapter (and the next one), we turn our attention to silicon-based electronic devices. In particular, we present here the characterization of an active layer stack for novel optoelectronic devices consisting of alternate thin layers of pure silica (SiO2) and silicon-rich silicon oxide (SRO, SiOx). Upon high temperature annealing the SRO sublayer segregates into a Si nanocluster (Si-nc) precipitate phase and a SiO2 matrix. Additionally, erbium (Er) ions were implanted and used as luminescent centers in order to obtain a narrow emission at 1.54 μm. By means of the combination of HAADF and EELS techniques, structural and chemical information from the embedded Si-ncs is revealed. The analyzed energy-loss spectra contain contributions from the Si-ncs and the surrounding SiO2. By performing a double plasmon fit, the spatial distribution of the Si-ncs and the SiO2 barriers is accurately determined in the multilayer. Additionally, the quality of the studied multilayer in terms of composition, roughness, and defects is analyzed and discussed. Er clusterization was not observed, neither by HAADF-EELS nor EDX. Blue-shifted plasmon and interband transition energies for silica are measured, in the presence of Er ions and sizable quantum confinement effects.

Abstract: Publication date: 2019Source: Advances in Imaging and Electron Physics, Volume 209Author(s): Alberto Eljarrat, Sònia Estradé, Francesca PeiróAbstractThis chapter presents a detailed examination of an InxGa1−xN multilayer structure, composed of alternating In-rich quantum wells (QWs) and In-deficient barriers. The nominal widths of these semiconductor layers are 1.5 nm and 6 nm, for the QW and barrier layers, respectively. This is, thus, a structure with features in the nanometer size range, smaller than the two structures examined in the preceding chapter. Again, our STEM examination consists in the simultaneous acquisition of HAADF images and spatially resolved low-loss EELS-SI, that are used in combination. However, this time, we also present a detailed analysis of high resolution HAADF images, that provides additional evidence of chemical and structural changes in the layers. Subtle changes in the valence properties of the materials, band gap energy, plasmon excitation, and also elemental transitions are monitored by low-loss EELS. Kramers–Kronig analysis (KKA) of the energy-loss spectrum is used to extend the dielectric characterization. In this sense, we apply a method for the experimental characterization of the plasmon excitation in the CDF based on our findings in Chapter 3, consisting in the determination of Ecut in the CDF. Apart from this, we compute spatially localized electron effective mass values from our CDFs, as we expect some contrast in the QW region. Finally, we examine the intensity of the Ga 3d transition in a previously normalized SSD. We show how this can be carried out after KKA, revealing the gallium concentration distribution with an excellent spatial resolution.

Abstract: Publication date: 2019Source: Advances in Imaging and Electron Physics, Volume 209Author(s): Alberto Eljarrat, Sònia Estradé, Francesca PeiróAbstractThis chapter presents the high resolution monochromated STEM-EELS characterization of two distributed Bragg reflector (DBR) multilayer heterostructures, composed of a periodic staking of III-nitride layers. These heterostructures were grown by the group of E. Calleja at the Instituto de Sistemas Optoelectrónicos y Microtecnología (ISOM), from Universidad Politécnica de Madrid. One of these DBR is composed of an alternate staking of AlN and GaN layers, and the other one, of InAlN lattice matched to GaN. EELS at sub-nanometric spatial resolution and

Abstract: Publication date: 2019Source: Advances in Imaging and Electron Physics, Volume 209Author(s): Alberto Eljarrat, Sònia Estradé, Francesca PeiróAbstractThis chapter describes DFT band structure calculations that were performed in order to simulate the dielectric response of III-nitride semiconductors. The aim of this study is to improve our understanding of the features in the low-loss electron energy-loss spectra of ternary alloys, but the results are also relevant to optical and UV spectroscopy results. For these DFT calculations, the standard tools found in Wien2k software were used. The novel modified Becke–Johnson (mBJ) exchange-correlation potential was also implemented, in order to improve the band structure description of these semiconductor compounds. The results from these calculations include band structure, density of states, and complex dielectric function for the whole compositional range. When compared with standard generalized gradient approximation (GGA), the predicted band gap energies for the novel potential were found to be larger and closer to experimental values. Additionally, the dependence of the most interesting features with composition was described by applying a Vegard law to band gap and plasmon energies. For this purpose, three wurtzite ternary alloys, from the combination of binaries AlN, GaN, and InN, were simulated through the whole compositional range (i.e., AlxGa1−xN, InxAl1−xN, and InxGa1−xN, with x=[0,1]). Moreover, a detailed analysis of the collective excitation mode in the dielectric response coefficients (CDF and ELF) was performed by model based analysis. This reveals their compositional dependence, which sometimes departs from a linear behavior. Finally, an advantageous method for measuring the plasmon energy dependence from these calculations was also developed.

Abstract: Publication date: 2019Source: Advances in Imaging and Electron Physics, Volume 209Author(s): Alberto Eljarrat, Sònia Estradé, Francesca PeiróAbstractIn this chapter, computational procedures for the analysis of materials properties in low-loss EELS are presented. The discussion is necessarily restricted to only some of these methods; of course, these are the tools that are used in the following chapters of this work. Hence, the stress is put into the signal processing, calculation, and simulation tools designed for STEM-EELS experiments in semiconductor materials. First, the common analytical tools for the analysis of the low-loss EELS spectra are explained. Following that, statistical tools conceived for the analysis of multidimensional datasets are separately presented. Those are most useful for our purposes, but are perhaps less known to the typical EELS analyst. Finally, the density functional theory tools (DFT) for the simulation of EELS are also presented.

Abstract: Publication date: 2019Source: Advances in Imaging and Electron Physics, Volume 209Author(s): Alberto Eljarrat, Sònia Estradé, Francesca PeiróAbstractIn this work, we aim to examine structures of interest in the semiconductor materials field that demand characterization solutions at the higher resolution available. The examined semiconductor materials are based on silicon or III–V nitrides, among the more important of their kind for industrial applications. The analyzed samples contain structures, from thin deposited layers to quantum well and dot structures, in the nanometer size range. Our tool of choice, the aberration-corrected and beam-monochromated scanning transmission electron microscope (STEM), gives us the opportunity to push the resolution barrier close to the atomic level. Our aim is to explore the analytical capabilities of the electron energy-loss spectroscopy (EELS) technique in these interesting materials and using the most advanced tools.The following sections in this chapter give an overview of the theoretical foundations of the EELS technique. The low-loss part of the EEL spectrum will be our main analysis tool, so a special focus is put on its main features; the link of the spectral features with theoretical properties of materials and the limitations of the technique. The following chapter describes the analytical and theoretical methods that are used to treat the experimental data and to simulate spectral shapes. After that several separate contributions present results obtained using these tools. Simulation results are first presented in the third chapter, and after that, several more chapters deal with different experimental works. These chapters serve to introduce the more specific techniques that have been developed for the preparation of this research work. These results are aimed at the better understanding of the EELS spectrum, overcoming some of the limitations of the technique, and revealing some interesting properties of the examined materials and structures.

Abstract: Publication date: 2018Source: Advances in Imaging and Electron Physics, Volume 208Author(s): John A. RouseAbstractA method has been developed for the analysis of three dimensional (3D) electron optical components using the finite difference method. Electrodes, dielectric materials (including any applied surface charge distributions), and ferromagnetic materials of quite general 3D shapes including the coil windings can all be analyzed in a unified way. The new finite difference equations have been derived in full mathematical detail.The method has been implemented in a suite of computer programs which have been developed and run on a desktop or laptop personal computer. This has necessitated making the software as fast and memory efficient as possible. The programs compute the 3D electric and magnetic field distributions, perform direct electron ray-tracing through the combined fields and provide graphical output of the fields and trajectories. The accuracy of the software has been established by various analytic tests and comparisons with existing software. Computed fields in round electron lenses compared favorably with those from rotationally symmetric finite element analyses. Tolerances for lens electrode machining errors agreed to within a few percent with the results of a perturbation analysis. Optical properties for electrostatic and magnetic lenses have been computed by direct ray-tracing using the 3D programs and the results compared with those from 2D programs using a paraxial ray-trace and aberration integrals. In all cases the agreement is good.Examples which highlight the effectiveness of the programs as a design tool have been presented. These include: 3D aspects of photomultiplier tube design, with specific examples in the photocathode region and the dynode stack; magnetic immersion lenses for a scanning electron microscope (SEM), which allow specimen access into the lenses via side slots; surface charging effects which occur during inspection of insulating specimens in the SEM and a simulation of the line scan; a Wien filter for monochromating an electron beam; and a combined electric and magnetic focussing and deflection system in the presence of stray 3D fields. It has been shown, therefore, that complicated 3D analyses of a variety of electron optical components can be performed to a high degree of accuracy on the new generation of small personal or portable microcomputers. This provides designers of electron beam equipment with a relatively cheap and convenient design tool.

Abstract: Publication date: 2018Source: Advances in Imaging and Electron Physics, Volume 208Author(s): John van Gorkom, Dirk van Delft, Ton van HelvoortAbstractThe German inventor and developer of the electron microscope, Ernst Ruska, characterised the period 1933 to 1937 as an incubation period for the commercial launch of the instrument by Siemens. Although it was only in this latter year that Ruska and his friend Bodo von Borries succeeded in finding a business ally, the brief interval saw remarkable developments in the visualisation of biological objects by means of an electron beam. Here this history is charted, in Europe and North America, for these critical years. The roles of the principal scientists involved are portrayed in detail. What emerges from this analysis is the separate development of the transmission electron microscopes and the instrument based on emission. This article extends van Gorkom's previous account in these Advances of the work of Ernst Ruska and others by relating how the instrument builders finally got backing from industry.

Abstract: Publication date: 2018Source: Advances in Imaging and Electron Physics, Volume 208Author(s): B.J. HoendersAbstractA comprehensive review of Ghost Imaging is given, presenting detailed analyses of its resolution, field of view, visibility, image contrast, and signal-to-noise ratio behavior, as well as analytic results, emphasizing the underlying physics of ghost imaging.Three different illumination modes are analyzed: thermal state (classical), biphoton state (quantum), and classical state phase sensitive light. The latter state is the classical Gaussian state that produces ghost images which most closely mimic those obtained from biphoton illumination.Furthermore, Ghost Imaging, in connection with turbulence, phase objects, spectral-temporal and spatial correlations as well as computational ghost imaging, is analyzed.