Advances in Imaging and Electron Physics

1. Auflage 2014
ISBN: 978-0-12-800307-7
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: Adobe DRM (»Systemvoraussetzungen)

E-Book, Englisch, Band Volume 186, 182 Seiten

Reihe: Advances in Imaging and Electron Physics

Advances in Imaging & Electron Physics merges two long-running serials-Advances in Electronics & Electron Physics and Advances in Optical & Electron Microscopy. The series features extended articles on the physics of electron devices (especially semiconductor devices), particle optics at high and low energies, microlithography, image science and digital image processing, electromagnetic wave propagation, electron microscopy, and the computing methods used in all these domains. - Contributions from leading authorities - Informs and updates on all the latest developments in the field

Autoren/Hrsg.

Inhaltsverzeichnis

1;Front
Cover;1
2;EDITOR-IN-CHIEF;3
3;Advances in Imaging and Electron Physics;4
4;Copyright;5
5;CONTENTS;6
6;PREFACE;8
7;FUTURE CONTRIBUTIONS;10
8;CONTRIBUTORS;14
9;CHAPTER ONE -
Practical Aspects of Transmission Electron Microscopy in Liquid;16
9.1;1. INTRODUCTION;17
9.2;2. MOST FREQUENTLY USED SYSTEMS FOR ELECTRON MICROSCOPY OF LIQUID SPECIMENS;18
9.3;3. SYSTEM DESIGN SPECIFICATIONS;21
9.4;4. PRACTICAL ASPECTS OF ELECTRON MICROSCOPY IN LIQUID;30
9.5;5. CONCLUSIONS;46
9.6;ACKNOWLEDGMENTS;47
9.7;REFERENCES;48
10;CHAPTER TWO -
Linear Canonical Transform;54
10.1;1. INTRODUCTION;55
10.2;2. DEFINITIONS OF THE LINEAR CANONICAL TRANSFORM;57
10.3;3. PROPERTIES AND PHYSICAL MEANINGS OF THE LINEAR CANONICAL TRANSFORM;61
10.4;4. OPERATIONS CLOSELY RELATED TO THE LINEAR CANONICAL TRANSFORM;73
10.5;5. DIGITAL IMPLEMENTATION AND DISCRETE VERSIONS OF THE LINEAR CANONICAL TRANSFORM;82
10.6;6. APPLICATIONS OF THE LINEAR CANONICAL TRANSFORM IN SIGNAL PROCESSING;86
10.7;7. LINEAR CANONICAL TRANSFORM FOR ELECTROMAGNETIC WAVE PROPAGATION ANALYSIS;97
10.8;8. TWO-DIMENSIONAL VERSIONS OF THE LINEAR CANONICAL TRANSFORM;106
10.9;9. CONCLUSION;109
10.10;REFERENCES;109
11;CHAPTER THREE -
Mechanical, Electrostatic, and Electromagnetic Manipulation of Microobjects and Nanoobjects in Electron Microscopes;116
11.1;1. INTRODUCTION;116
11.2;2. OVERVIEW OF FORCES ACTING ON A PARTICLE IN AN ELECTRON MICROSCOPE;119
11.3;3. MECHANICAL MANIPULATION;129
11.4;4. ELECTROSTATIC MANIPULATION;139
11.5;5. ELECTROMAGNETIC MANIPULATION;146
11.6;6. CONCLUSION;150
11.7;ACKNOWLEDGMENTS;151
11.8;REFERENCES;151
12;CONTENTS OF VOLUMES 151–185;156
13;INDEX;164
14;Color Plate;170

Leseproben

Chapter One

Practical Aspects of Transmission Electron Microscopy in Liquid

Niels de Jongea,b,c, Marina Pfaffa and Diana B. Peckysa     aINM—Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany     bDepartment of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, 2215 Garland Ave, Nashville, TN 37232-0615     cDepartment of Physics, University of Saarland, Campus A5 1, 66123 Saarbrücken, Germany

Abstract

Ever since the invention of electron microscopy, there has been the desire to image biological samples and other samples, such as colloids, in their native liquid environment (as one can do with light microscopy), and various approaches have been developed throughout the years. The usage of microchip technology to produce micrometer-sized liquid enclosures with electron transparent silicon nitride (SiN) windows has spurred the research area of transmission electron microscopy (TEM) in liquid over the past decade. Solid material can be studied in situ in liquid layers of up to several hundreds of nanometers using liquid-cell TEM. Much thicker samples of up to 10 micrometers (µm) are available for the imaging of materials with a high atomic number (Z) in low-Z liquids using scanning transmission electron microscopy (STEM). In this chapter, a detailed discussion is presented of the practical aspects of the three most frequently used technical approaches for electron microscopy of liquid specimens: (1) environmental SEM (ESEM), (2) TEM and STEM of closed liquid cells, and (3) TEM and STEM of liquid flow devices. Details about the required equipment are also included. Liquid electron microscopy experiments need to be carried out carefully, and various factors need to be optimized. Nevertheless, user-friendly systems are now available, and exciting, novel scientific breakthroughs can be expected to result from the new capabilities to view images in liquid at a (sub-)nanoscale resolution.

Keywords

STEM; TEM; Liquid cell; Liquid STEM; Liquid-cell TEM; ESEM; ESEM-STEM; Wet-STEM; Nano particle; Cell; Resolution; Silicon nitride membrane

1. Introduction

Electron microscopy traditionally provides subnanometer resolution on solid specimens in vacuum. Because many research questions involve specimens in a liquid environment, it has been a goal to image liquid specimens with electron microscopy ever since the invention of the electron microscope (von Ardenne, 1941; Ruska, 1942; Parsons et al., 1974). Triggered by the availability of electron transparent thin membranes of high stability (Williamson et al., 2003; Thiberge et al., 2004), electron microscopy of liquid specimens has experienced an upsurge of interest in the recent years (de Jonge & Ross, 2011; de Jonge, 2014) with several applications in in biology (de Jonge et al., 2009), material science, and chemistry (Zheng et al., 2009). The advantage of liquid electron microscopy for the investigation of biological systems is that whole cells can be imaged in their native liquid environment (de Jonge et al., 2009; Nishiyama et al., 2010; Peckys & de Jonge, 2014a), while such samples would otherwise have to be dehydrated and embedded in plastic or frozen, and mostly also thin-sectioned (Kourkoutis, Plitzko, & Baumeister, 2012). It is also possible to image protein complexes in liquid (Matricardi, Moretz, & Parsons, 1972; Mirsaidov et al., 2012; Dukes et al., 2014), so that attempts can be made in the near future to study the structure of proteins in their native liquid surroundings. It seems possible to image dynamic processes in certain biological systems (Sugi et al., 1997), but the inevitable severe effect of electron beam irradiation needs to be considered. Most applications of liquid scanning transmission electron microscopy (STEM) are currently found for the imaging of inorganic samples. The movement of nanoparticles in liquid has been studied by various researchers (Zheng et al., 2009; Ring & de Jonge, 2010; Chen & Wen, 2012; Ring & de Jonge, 2012; White et al., 2012; Dukes et al., 2013; Liu et al., 2013). The growth processes of nanoparticles (Evans et al., 2011; Xin & Zheng, 2012; Yuk et al., 2012; Liao & Zheng, 2013; Niu et al., 2013; Nielsen et al., 2014), nanorods (Liao et al., 2012), dendrites (White et al., 2012; Kraus & de Jonge, 2013), and clusters (Williamson et al., 2003; Radisic et al., 2006; Li et al., 2012) are important topics of study. Chemical reactions such as the formation of hollow particles by the Kirkendall effect (Niu et al., 2013) or corrosion of aluminum films (Chee et al., 2014) have been imaged with liquid (S)TEM. The most complex application is probably the imaging of dynamic processes in functional microdevices (Sacci et al., 2014; Zeng et al., 2014), such as what occurs during the investigation of Li-ion batteries (Holtz et al., 2014; Mehdi et al., 2014; Sacci et al., 2014). By exploiting the interaction of the incident electrons with a liquid precursor, defined patterns can be created on a substrate (Liu et al., 2012; Grogan et al., 2013; den Heijer et al., 2014).

In this chapter, we will discuss the principles of the two most frequently used technical approaches for electron microscopy of liquid specimens: (1) open systems using environmental scanning electron microscopy (ESEM) and environmental scanning electron microscopy (ETEM), and (2) scanning transmission electron microscopy (STEM) of specimens enclosed between SiN windows. We will describe the involved equipment and include detailed design requirements of one particular liquid flow system as an example of the considerations that need to be involved. The chapter also contains many practical details for carrying out such experiments.

2. Most Frequently Used Systems for Electron Microscopy of Liquid Specimens

Basically, two different approaches exist to study liquid specimens (de Jonge & Ross 2011).

2.1. Open Systems

Open systems expose the liquid to the vacuum (see Figure 1.1). The vacuum level and the temperature are adjusted to the vapor pressure of the liquid to achieve equilibrium between liquid and vapor. The vacuum level in the specimen chamber can be adjusted with pump-limiting apertures in the electron optical column. This apparatus was invented in the 1940s (Ruska 1942) for TEM (Figure 1.1a) and is now mostly used to study specimens in a gaseous environment (Helveg et al., 2004). A pressure of up to 1 bar can be realized in such environmental chambers (Gai, 2002). A variation of this concept is the usage of ionic liquids, which have such a low vapor pressure that the specimens can be directly imaged in a high vacuum (Huang et al., 2010). A similar approach was used for SEM (Danilatos & Robinson, 1979) in the 1970s and has found widespread use as variable pressure SEM or ESEM (Stokes, 2003, 2008). A resolution of a few nanometers can be achieved on nanoparticles using the STEM detector (Bogner et al., 2005; Peckys et al., 2013); see Figure 1.1b. The ESEM is now widely used to image specimens in liquid (Peckys et al.,, 2013; Barkay, 2014; Bresin et al., 2014; Jansson et al., 2014; Novotny et al., 2014), and is available commercially. In the next sections, we will describe practical aspects of imaging wet samples with ESEM and a STEM detector. Other open systems are not described here for practical reasons.

Figure 1.1 Principles for open systems. (a) Schematic drawing of the sample region of ETEM with a differentially pumped environmental chamber containing vapor. (b) The design and working principle of an ESEM with an STEM detector and a gaseous secondary electron detector (GSED). The dimensions are not to scale.

2.2. Closed Systems

Closed systems protect the liquid from a vacuum by means of thin-membrane windows that are transparent for the electron beam (see Figure 1.2). The crucial aspect of such a system is the material of the membrane. It needs to be made of a light element and as thin as possible to minimize interaction of the electron beam with the membrane, while it must be sufficiently strong to allow practical experiments. Carbon (Daulton et al., 2001; Nishijima et al., 2004) and polymer (Thiberge et al., 2004) foils have been extensively tested, but films of SiN are preferred in practice (Williamson et al., 2003; de Jonge et al., 2009). Delicate sample preparation techniques, developed in recent years, allowed graphene to be used to enclose a small droplet of saline (Mohanty...