Microscopy STEM

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. 

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. 

Scanning thermal microscopy, 3 332-333 Scanning transmission electron microscopy (STEM), 24 74... 

Substrate Characterization. Test coupons and panels of 7075-T6 aluminum, an alloy used extensively for aircraft structures, were degreased In a commercial alkaline cleaning solution and rinsed In distilled, deionized water. The samples were then subjected to either a standard Forest Products Laboratories (FPL) treatment ( 0 or to a sulfuric acid anodization (SAA) process (10% H2SO4, v/v 15V 20 min), two methods used for surface preparation of aircraft structural components. The metal surfaces were examined by scanning transmission electron microscopy (STEM) In the SEM mode and by X-ray photoelectron spectroscopy (XPS). 

To find the distribution of iron within the nanotube walls an energy dispersive x-ray spectroscopy (EDS) line scan was performed via scanning transmission electron microscopy (STEM), see Fig. 5. 55. The intensity of both the TiK and FeKa lines are maximum at the center of the wall due to its torus shape. Despite the presence of isolated hematite crystallites, a more or less uniform distribution of iron relative to the titanium can be seen across the wall. STEM line scans were performed across a number of walls, and while the average relative intensity of the TiK and FeKa lines varied from wall to wall the relative distribution across a single wall remained uniform. It appears that some of the iron goes into the titanium lattice substituting titanium ions, and the rest either forms hematite crystallites or remains in the amorphous state. 

Transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) are recognized as powerful and versatile tools for the characterization of supported metal catalysts, because real-space images of catalysts with spatial resolution down to 0.1 nm can be recorded and combined with high-spatially resolved spectroscopic information. However, TEM has been used mainly for ex situ characterization, for example, of catalysts after gas treatments. 

Fig. 7.7 Scanning transmission electron microscopy (STEM) images of supported gold catalysts, along with particle diameter distributions, double-logarithmic plots showing how particle volume (proportional to intensity) depends on particle size, and geometric distributions of truncated octahedrons with certain edge lengths and thickness, as indicated in Figure 7.8. (Adapted from [18]).

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