Abstract: Publication date: Available online 25 June 2018Source: Advances in Imaging and Electron PhysicsAuthor(s): Arnaud Arbouet, Giuseppe M. Caruso, Florent Houdellier Transmission Electron Microscopes (TEM) have allowed giant steps in chemistry, biology or physics. Many of these achievements were nourished by key instrumental developments such as aberration correctors, high brightness sources, detectors, etc. Despite spectacular advances, investigations using TEM have long been restricted to systems either static or evolving on timescales compatible with the frame rate of CCD cameras. Time-resolved Transmission Electron Microscopy aims at overcoming this limitation and exploring the dynamics of nanoscale systems. Since the pioneering work of the group of O. Bostanjoglo at the TU Berlin, spectacular progress has been made to provide time-resolved TEM with a constantly improving spatio-temporal resolution. These advances rely mostly, although not exclusively, on ultrafast lasers and are largely inspired from time-resolved optical spectroscopy techniques.In this review, we provide an introduction to the field of time-resolved TEM, describe the major instrumental developments, and give examples of applications in different fields. In Section 5, we discuss the possibility of performing time-resolved electron holography with new high brightness UTEMs.

Abstract: Publication date: Available online 7 May 2018Source: Advances in Imaging and Electron PhysicsAuthor(s): Karl-Joseph Hanszen The theory of image formation in the electron microscope is explained in terms of amplitude and phase contrast-transfer functions in great detail. The notion of transparency is described and strong and weak objects are defined. The effects of spherical aberration and defocus are presented at length. The experimental verification of the theory by Friedrich Thon is reproduced. Phase plates and absorption plates are discussed in connection with zone plates and phase-changing devices. Resolution is considered in the light of the contrast-transfer functions. The effect of partial coherence of the illumination is examined.

Abstract: Publication date: 2018Source: Advances in Imaging and Electron Physics, Volume 206Author(s): Axel Lubk In the summary we wrap up the main results pertaining to the reconstruction of physical, e.g., electric or magnetic, fields in 3D by Electron Holographic Tomography. We elaborate on how to further extend the scope of holographic tomography towards a larger class of fields, such as strain, and quantum states, e.g., of inelastically scattered electrons, including a discussion of required instrumental advances and developments.

Abstract: Publication date: 2018Source: Advances in Imaging and Electron Physics, Volume 206Author(s): Axel Lubk This chapter contains case studies, which exemplify how the previous considerations lead to working experimental procedures and finally materials properties in terms of three-dimensional physical fields. We mainly focus on off-axis Electron Holographic Tomography. We first discuss its experimental implementation, including recording, alignment, preprocessing, and reconstruction of the tilt series. We demonstrate the reconstruction of electric fields down to nanometer resolution and show how to extend the technique to the retrieval of magnetic, strain, and attenuation fields.

Abstract: Publication date: 2018Source: Advances in Imaging and Electron Physics, Volume 206Author(s): Axel Lubk In this chapter, we will separately consider the holographic reconstruction of mixed (quantum) states and pure states (wave), employing a variety of holographic setups in TEM, namely Off-Axis Holography, Transport of Intensity Reconstruction, Focal Series Inline Holography, Differential Phase Contrast, and Ptychography. Each holographic technique is in the first place considered as a general mixed quantum state reconstruction scheme, and the conventional wave (pure state) reconstruction is treated as a special case of the former. This practice permits a comprehensive discussion of the ramifications of partial coherence on conventional wave reconstructions as well as a generalization toward partially coherent or incoherent signals such as resulting from inelastic scattering.

Abstract: Publication date: 2018Source: Advances in Imaging and Electron Physics, Volume 206Author(s): Axel Lubk In this chapter a description of the transfer of the paraxial quantum state through the optical system of a Transmission Electron Microscopy is provided. We begin with a short recapitulation of classical electron optics, which contains an introduction to geometric aberrations, playing a fundamental role in the imaging process. Subsequently, Miller's semiclassical algebra is used to construct the electron's wave function and its transfer properties. In a final step, the wave function transfer is generalized to that of the Wigner function, i.e., the partially coherent quantum state. The close correspondence between Wigner function and classical phase space density will become particularly obvious in the way aberrations affect the Wigner function, where one can distinguish between a classical deformation and an integral transformation of purely quantum mechanical origin.

Abstract: Publication date: 2018Source: Advances in Imaging and Electron Physics, Volume 206Author(s): Axel Lubk This chapter contains the main principles of tomography as required in Chapters 5 and 6. First, a brief introduction to general projection transformations, including the geometrical setting typically used when combining Electron Holography and Tomography, is given. Subsequently, the two-dimensional Radon transformation, providing the mathematical theory behind the tomographic reconstructions used in this work, is introduced. Based on these foundations, the discrete Radon transformation, providing the framework for tomographic reconstruction algorithms, is discussed. Two separate subsections are devoted to sampling and regularization, which are substantial for a thorough understanding of tomographic reconstructions from experimental data. Finally, three reconstruction algorithms, heavily used in the remainder of this work, are presented in detail.

Abstract: Publication date: 2018Source: Advances in Imaging and Electron Physics, Volume 206Author(s): Axel Lubk This chapter provides the foundations of paraxial quantum mechanics as valid for relativistic electrons traveling along the optical axis of a Transmission Electron Microscope. Starting point is a derivation of relativistic paraxial wave dynamics from first principles. This description is subsequently generalized to the concepts of the density operator and the quantum mechanical phase space, including their paraxial dynamics. Quantum mechanical phase space is represented by the Wigner function, simultaneously describing the properties of the electron beam in position and diffraction (Fourier) space. The phase space representation of the imaging process and the unified description of different holographic schemes discussed in Chapters 4 and 5 are founded in these principles.

Abstract: Publication date: 2018Source: Advances in Imaging and Electron Physics, Volume 206Author(s): Axel Lubk This chapter gives a brief introduction into the history of holography and tomography as well as transmission electron microscopy. It is shown that all three concepts are closely linked and cross-fertilized each other in their development. Going one step further, the introduction provides a red ribbon on how holography and tomography may be combined in the transmission electron microscope to facilitate the 3D reconstruction of physical fields as well as quantum states as discussed in this volume.

Abstract: Publication date: 2018Source: Advances in Imaging and Electron Physics, Volume 205Author(s): Erich Plies The review starts with some historic remarks on the scanning electron microscope (SEM) and early attempts to improve the resolution of the SEM in the low-voltage regime. Today there are many SEM-like instruments, as the e-beam tester and the e-beam inspection system, which are used in the semiconductor industry and are operated at a low voltage of about 1 kV. For such a low voltage the probe diameter (resolution) of the electron-optical column is limited mainly by chromatic aberration and additional Coulomb interaction in the case of a high probe current, which is necessary for high throughput. To build a dedicated electron-optical column providing a required performance a preceding simulation of all elements (gun, lenses, deflectors, compound elements, …) and the complete system is indispensable.Existing simulation tools, analytical as well as numerical methods, are reviewed in this article. After the design of an electron-optical element (geometry, voltages of electrodes, currents of magnetic coils) the computation of electrostatic and/or magnetic fields is the first simulation step. After presenting some helpful analytical field calculation examples, the numerical methods, mainly FDM (finite difference method), FEM (finite element method), CDM (surface charge density method) and CSM (charge simulation method), are discussed together with their advantages and disadvantages. The next simulation step is the computation of the electron trajectories using the classical perturbation theory (first-order rays, cardinal elements and aberrations) or ray tracing, i.e. numerical integration of the equation of motion or an exact trajectory equation. Both methods may be used for the primary electrons, but ray tracing is necessary in the case of the secondary electrons to determine the collection efficiency or the performance of the secondary electron analyzer used in an e-beam tester to measure IC-internal voltages.Different approaches to optimize electron lenses and compound scanning systems are reviewed. Since the Coulomb interaction (Boersch effect and trajectory displacement effect) has a limiting influence in e-beam testing and electron optical inspection its simulation is treated together with means of reducing this interaction. The last topic of this review is the undesirable specimen charging. Approaches to simulate and to avoid this phenomenon have been collected.

Abstract: Publication date: 2018Source: Advances in Imaging and Electron Physics, Volume 205Author(s): John van Gorkom, Dirk van Delft, Ton van Helvoort Developments during the early years of the electron microscope, essentially the first four years of the 1930s, are recapitulated in careful detail, the publications by the main actors are analysed and the numerous patents are examined. The roles of Siemens and AEG are described and attention is drawn to related work in Belgium, France, the USA and England. The late impact of de Broglie's work is commented on.