Electron transmission

Transmission electron microscopy (TEM) can resolve features down to about 1 nm and allows the use of electron diffraction to characterize the structure. Since electrons must pass through the sample however, the technique is limited to thin films. One cryoelectron microscopic study of fatty-acid Langmuir films on vitrified water [13] showed faceted crystals. The application of TEM to Langmuir-Blodgett films is discussed in Chapter XV. 

Fig. Vni-3. (a) Atomic force microscope (AFM) and (b) transmission electron microscope (TEM) images of lead selenide particles grown under arachidic acid monolayers. (Pi Ref. 57.)...

Fig, XIV-12. Freeze-fracture transmission electron micrographs of a bicontinuous microemulsion consisting of 37.2% n-octane, 55.8% water, and the surfactant pentaethy-lene glycol dodecyl ether. In both cases 1 cm 2000 A (for purposes of microscopy, a system producing relatively coarse structures has been chosen), [(a) Courtesy of P. K. Vinson, W. G. Miller, L. E. Scriven, and H. T. Davis—see Ref. 110 (b) courtesy of R. Strey—see Ref. 111.]... 

Takayanagi K, Tanishiro Y, Takahashi M and Takahashi S 1985 Structural analysis of Si(111)-7 7 by UFIV-transmission electron diffraction and microscopy J. Vac. Sot Technol. A 3 1502... 

As noted earlier, most electron diffraction studies are perfonned in a mode of operation of a transmission electron microscope. The electrons are emitted themiionically from a hot cathode and accelerated by the electric field of a conventional electron gun. Because of the very strong interactions between electrons and matter, significant diffracted intensities can also be observed from the molecules of a gas. Again, the source of electrons is a conventional electron gun. 

Thomas G and Goringe M J 1981 Transmission Electron Microscopy of Materials (New York Wiiey)... 

The history of EM (for an overview see table Bl.17,1) can be interpreted as the development of two concepts the electron beam either illuminates a large area of tire sample ( flood-beam illumination , as in the typical transmission electron microscope (TEM) imaging using a spread-out beam) or just one point, i.e. focused to the smallest spot possible, which is then scaimed across the sample (scaiming transmission electron microscopy (STEM) or scaiming electron microscopy (SEM)). In both situations the electron beam is considered as a matter wave interacting with the sample and microscopy simply studies the interaction of the scattered electrons. 

Williams D B and Carter C B 1996 Transmission Electron Microscopy, A Textbook for Material Science (New York Plenum)... 

Reimer L 1993 Transmission Electron Microscopy (Berlin Springer)... 

Crewe A V, Wall J and Welter L M 1968 A high resolution scanning transmission electron microscope J. Appl. Phys. 39 5861-8... 

Light microscope Scanning electron microscope Transmission electron microscope Scanning probe microscope... 

One fiirther method for obtaining surface sensitivity in diffraction relies on the presence of two-dimensional superlattices on the surface. As we shall see fiirtlrer below, these correspond to periodicities that are different from those present in the bulk material. As a result, additional diffracted beams occur (often called fractional-order beams), which are uniquely created by and therefore sensitive to this kind of surface structure. XRD, in particular, makes frequent use of this property [4]. Transmission electron diffraction (TED) also has used this property, in conjunction with ultrathin samples to minimize bulk contributions [9]. 

Takayanagi K 1990 Surface structure analysis by transmission electron diffraction—effects of the phases of structure factors Acta. Crystalloger A 46 83-6... 

Blodgett films direct imaging by scanning tunneling microscopy and high-resolution transmission electron... 

The spatial arrangement of atoms in two-dimensional protein arrays can be detennined using high-resolution transmission electron microscopy [20]. The measurements have to be carried out in high vacuum, but since tire metliod is used above all for investigating membrane proteins, it may be supposed tliat tire presence of tire lipid bilayer ensures tliat tire protein remains essentially in its native configuration. 

Figure C2.17.1. Transmission electron micrograph of a Ti02 (anatase) nanocrystal. The mottled and unstmctured background is an amorjihous carbon support film. The nanocrystal is centred in die middle of die image. This microscopy allows for die direct imaging of die crystal stmcture, as well as the overall nanocrystal shape. This titania nanocrystal was syndiesized using die nonhydrolytic niediod outlined in [79].

Figure C2.17.2. Transmission electron micrograph of a gold nanoneedle. Inverse micelle environments allow for a great deal of control not only over particle size, but also particle shape. In this example, gold nanocrystals were prepared using a photolytic method in surfactant-rich solutions the surfactant interacts strongly with areas of low curvature, thus continued growth can occur only at the sharjD tips of nanocrystals, leading to the fonnation of high-aspect-ratio nanostmctures [52].

In many ways the nanocrystal characterization problem is an ideal one for transmission electron microscopy (TEM). Here, an electron beam is used to image a thin sample in transmission mode [119]. The resolution is a sensitive fimction of the beam voltage and electron optics a low-resolution microscope operating at 100 kV might... 

Figure C2.17.4. Transmission electron micrograph of a field of Zr02 (tetragonal) nanocrystals. Lower-resolution electron microscopy is useful for characterizing tire size distribution of a collection of nanocrystals. This image is an example of a typical particle field used for sizing puriDoses. Here, tire nanocrystalline zirconia has an average diameter of 3.6 nm witli a polydispersity of only 5% 1801.

Figure C2.17.5. Transmission electron micrograph of a field of anisotropic gold nanocrystals. In tliis example, a lower magnification image of gold nanocrystals reveals tlieir anisotropic shapes and faceted surfaces [36],...

Figure C2.17.6. Transmission electron micrograph and its Fourier transfonn for a TiC nanocrystal. High-resolution images of nanocrystals can be used to identify crystal stmctures. In tliis case, tire image of a nanocrystal of titanium carbide (right) was Fourier transfonned to produce tire pattern on tire left. From an analysis of tire spot geometry and spacing, one can detennine that tire nanocrystal is oriented witli its 11001 zone axis parallel to tire viewing direction [217].

Figures 4.1 la and b, respectively, are examples of dark-field and direct transmission electron micrographs of polyethylene crystals. The ability of dark-field imaging to distinguish between features of the object which differ in orientation is apparent in Fig. 4.11a. The effect of shadowing is evident in Fig. 4.11b, where those edges of the crystal which cast the shadows display sharper contrast.

L. Reimer, Transmission Electron Microscopy, Springer Series in Optical Sciences, Vol. 36, 2nd ed., Springer-Vedag Berlin, 1989. 

Fig. 1. Transmission electron micrograph of ABS produced by an emulsion process. Staining of the mbber bonds with osmium tetroxide provides contrast...

Fig. 2. Transmission electron micrograph of ABS produced by a mass process. The mbber domains are typically larger in size and contain higher...

The very high powers of magnification afforded by the electron microscope, either scanning electron microscopy (sem) or scanning transmission electron microscopy (stem), are used for identification of items such as wood species, in technological studies of ancient metals or ceramics, and especially in the study of deterioration processes taking place in various types of art objects. 

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