Physical Principles of Electron Microscopy: An Introduction to TEM ...

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120 Chapter 4 At this stage it is convenient to cut a 3-mm-diameter disk out of the slice. For reasonably soft metals (e.g., aluminum, copper), a mechanical punch may be used. For harder materials, an ultrasonic drill is necessary; it consists of a thin-walled tube (internal diameter = 3 mm) attached to a piezoelectric crystal that changes slightly in length when a voltage is applied between electrodes on its surfaces; see Fig. 4-20a. The tube is lowered onto the slice, which has been bonded to a solid support using by heat-setting wax and its top surface pre-coated with a silicon-carbide slurry (SiC powder mixed with water). Upon applying a high-frequency ac voltage, the tube oscillates vertically thousands of times per second, driving SiC particles against the sample and cutting an annular groove in the slice. When the slice has been cut through completely, the wax is melted and the 3-mm disk is retrieved with tweezers. The disk is then thinned further by polishing with abrasive paper (coated with diamond or silicon carbide particles) or by using a dimple grinder. In the latter case (Fig. 4-20b), a metal wheel rotates rapidly against the surface (covered with a SiC slurry or diamond paste) while the specimen disk is rotated slowly about a vertical axis. The result is a dimpled specimen whose thickness is 10 � 50 �m at the center but greater (100 � 400 �m) at the outside, which provides the mechanical strength needed for easy handling. In the case of biological tissue, a common procedure is to use an ultramicrotome to directly cut slices � 100 nm or more in thickness. The tissue block is lowered onto a glass or diamond knife that cleaves the material apart (Fig. 4-20c). The ultramicrotome can also be used to cut thin slices of the softer metals, such as aluminum. Some inorganic materials (e.g., graphite, mica) have a layered structure, with weak forces between sheets of atoms, and are readily cleaved apart by inserting the tip of a knife blade. Repeated cleavage, achieved by attaching adhesive tape to each surface and pulling apart, can reduce the thickness to below 1 �m. After dissolving the adhesive, thin flakes are mounted on 3-mm TEM grids. Other materials, such as silicon, can sometimes be persuaded to cleave along a plane cut at a small angle relative to a natural (crystallographic) cleavage plane. If so, a second cleavage along a crystallographic plane results in a wedge of material whose thin end is transparent to electrons. Mechanical cleavage is also involved when a material is ground into a fine powder, using a pestle and mortar, for example (Fig. 4-20d). The result is a fine powder, whose particles or flakes may be thin enough for electron transmission. They are dispersed onto a 3-mm TEM grid covered with a thin carbon film (sometimes containing small holes so that some particles are supported only at their edges).
TEM Specimens and Images 121 (a) (b) + piezo crystal wax (c) tissue (d) water trough (e) (f) + - (g) (h) Ar block vacuum ~ SiC slurry specimen jet specimen microtome arm + + + film Ar gas grinding wheel mortar wax - pestle specimen cathode electrolysis solution substrate boat specimen + powder vacuum chamber current Figure 4-20. Procedures used in making TEM specimens: (a) disk cutting by ultrasonic drill, (b) dimple grinding, (c) ultramicrotomy, (d) grinding to a powder, (e) chemical jet thinning, (f) electrochemical thinning, (g) ion-beam thinning, and (h) vacuum deposition of a thin film. Methods (a) � (d) are mechanical, (e) and (f) are chemical, (g) and (h) are vacuum techniques.
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Physical Principles of Electron Mic
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Ray F. Egerton Department of Physic
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Contents Preface xi 1. An Introduct
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Contents ix 7. Recent Developments
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xii Preface textbooks, such as Will
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2 1.1 Limitations of the Human Eye
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4 Chapter 1 parallel beam of light
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6 Chapter 1 Figure 1-3. One of the
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8 Chapter 1 Figure 1-5. Light-micro
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10 Chapter 1 Figure 1-7. Scanning t
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12 Chapter 1 Figure 1-8. Early phot
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14 Chapter 1 Figure 1-10. JEOL tran
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16 Chapter 1 hydrated. But high-ene
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18 Chapter 1 Figure 1-14. Scanning
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20 Chapter 1 Figure 1-16. Photograp
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22 Chapter 1 visible-light photons
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24 Chapter 1 Typically, the STM hea
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Chapter 2 ELECTRON OPTICS Chapter 1
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Electron Optics 29 a c b object len
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Electron Optics 31 � a n 2 ~1.5
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Electron Optics 33 We can define im
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Electron Optics 35 electron source
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Electron Optics 37 symmetry and use
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Electron Optics 39 As we said earli
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Electron Optics 41 2.4 Focusing Pro
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Electron Optics 43 � = [e/(8mE0)
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Electron Optics 45 image plane. Whe
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Electron Optics 47 procedure that i
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Electron Optics 49 The basic physic
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Electron Optics 51 From Eq. (2.7),
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Electron Optics 53 y +V 1 +V 2 -V 2
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Electron Optics 55 point from the o
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58 Chapter 3 3.1 The Electron Gun T
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60 Chapter 3 The rate of electron e
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62 Chapter 3 electron emission curr
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64 Chapter 3 As seen from the right
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66 Chapter 3 � r r s r � (a) (b
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68 Chapter 3 Table 3-2. Speed v and
Page 78 and 79: 70 Chapter 3 where G is a large amp
Page 80 and 81: 72 Chapter 3 The second condenser (
Page 82 and 83: 74 Chapter 3 Figure 3-9 summarizes
Page 84 and 85: 76 Chapter 3 resolution (especially
Page 86 and 87: 78 Chapter 3 The major advantage of
Page 88 and 89: 80 Chapter 3 contrast (for a given
Page 90 and 91: 82 Chapter 3 A more correct procedu
Page 92 and 93: 84 Chapter 3 diffraction pattern (s
Page 94 and 95: 86 Chapter 3 Nowadays, photographic
Page 96 and 97: 88 Chapter 3 A related concept is d
Page 98 and 99: 90 Chapter 3 molecules, imparting a
Page 100 and 101: 92 Chapter 3 Frequently, liquid nit
Page 102 and 103: 94 Chapter 4 -e -e -e -e +Ze Figure
Page 104 and 105: 96 Chapter 4 � (a) elastic z x m
Page 106 and 107: 98 Chapter 4 � b a (a) (b) Figure
Page 108 and 109: 100 Chapter 4 fraction of electrons
Page 110 and 111: 102 Chapter 4 whose composition or
Page 112 and 113: 104 Chapter 4 replica crystallites
Page 114 and 115: 106 Chapter 4 4.5 Diffraction Contr
Page 116 and 117: 108 Chapter 4 remain undiffracted (
Page 118 and 119: 110 Chapter 4 Close examination of
Page 120 and 121: 112 Chapter 4 Unfortunately, the va
Page 122 and 123: 114 Chapter 4 Crystals can also con
Page 124 and 125: 116 Chapter 4 A simple example of p
Page 126 and 127: 118 Chapter 4 High-magnification ph
Page 130 and 131: 122 Chapter 4 All of the above meth
Page 132 and 133: 124 Chapter 4 The procedures outlin
Page 134 and 135: 126 Chapter 5 specimen scan coils o
Page 136 and 137: 128 Chapter 5 functions with m and
Page 138 and 139: 130 Chapter 5 inelastic collisions
Page 140 and 141: 132 Chapter 5 Figure 5-5. Dependenc
Page 142 and 143: 134 Chapter 5 Figure 5-7. (a) Secon
Page 144 and 145: 136 Chapter 5 Because each secondar
Page 146 and 147: 138 Chapter 5 Backscattered electro
Page 148 and 149: 140 Chapter 5 Whereas Ip remains co
Page 150 and 151: 142 Chapter 5 Figure 5-14. Red, gre
Page 152 and 153: 144 Chapter 5 the SE2 and SE3 compo
Page 154 and 155: 146 Chapter 5 just-observable loss
Page 156 and 157: 148 Chapter 5 Section 4-10. Films o
Page 158 and 159: 150 Chapter 5 A backscattered-elect
Page 160 and 161: 152 Chapter 5 One example of this p
Page 162 and 163: Chapter 6 ANALYTICAL ELECTRON MICRO
Page 164 and 165: Analytical Electron Microscopy 157
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Analytical Electron Microscopy 171
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178 Chapter 7 Figure 7-1. Modified
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180 Chapter 7 7.2 Aberration Correc
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182 Chapter 7 Besides decreasing th
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184 Chapter 7 7.4 Electron Holograp
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186 Chapter 7 There are now many al
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188 Chapter 7 holography could ther
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Appendix MATHEMATICAL DERIVATIONS A
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Mathematical Derivations 193 A.2 Im
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REFERENCES Binnig, G., Rohrer, H.,
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INDEX Aberrations, 3, 28 axial, 44
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Index 199 EELS, 172 Electromagnetic
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Index 201 Principal plane, 32, 80 P
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