Analytical electron microscopic

The uniqueness and desirability of EELS is realized when it is combined with the power of a TEM or STEM to form an Analytical Electron Microscope (AEM). This combination allows the analyst to perform spatially resolved nondestructive analysis with high-resolution imaging (< 3 A). Thus, not oiJy can the analyst observe the microstructure of interest (see the TEM article) but, by virtue of the focusing ability of the incident beam in the electron microscope, he or she can simultaneously analyze a specific region of interest. Lateral spatial resolutions of regions as small as 10 A in diameter are achievable with appropriate specimens and probe-forming optics in the electron microscope. 

Figure 2. Signals generated in a thin specimen by a focused electron beam in an analytical electron microscope.

Approximate composition of individual hexaaluminate particles was measured by an analytical electron microscope to elucidate the correlation between hexaaluminate phases (Mn-rich and -poor) and Pr contents in the lattice (Figure 6). Although relative concentration of Sr to A1 was a constant at x=0, the composition of the particles in the sample was separated into two groups from their Sr/Al ratios and Mn contents. Pr ions are preferentially doped in the particles with small Mn/ A1 ratios at x=0.2. With an increase in Pr concentration, the number of Pr-poor particles decreased and their Mn/Al ratios approached to those of Pr-rich particles at x=0.4. The substitution of Mn for Al site compensates excess charge of Pr3+ in the hexaaluminate lattice and leads to an increase of Mn in the hexaaluminate particle. It is considered that ease of reduction-oxidation cycle was influenced by the compensation and gave rise to increase in catalytic activity for... 

C. Defosse, M. Hovalla, A. Lycourghoitis and B. Delmon, Joint analytical electron microscopic and XPS study of oxide and sulfide catalysts, in Perspectives in Catalysis, ed. R. Larsson, C. W. K. Gleerup, 1981. 

The analytical electron microscope (AEM) is fitted with a spectrometer for X-ray microanalysis and also for electron energy-loss analysis (q.v. pp. 185). 

IV. Chemical Composition Analysis with the Analytical Electron Microscope. 191... 

Transmission electron microscope (TEM) Scanning transmission electron microscope High-resolution electron microscope Analytical electron microscope... 

The discussion is restricted to energy-analyzing devices compatible with analytical electron microscopes. Generally, they are either electrostatic or... 

HRTEM images were obtained on a Jeol JEM2010 ultra high-resolution analytical electron microscope equipped with an emission cathode operated at 200KV in bright field mode. The samples were examined with a magnification of 400,000. The ex situ treated samples were supported holey carbon coated copper grids for the experiment. 

Bradley J. P., Brownlee D. E., and German M. S. (1989) Automated thin-film analyses of anhydrous interplanetary dust particles in the analytical electron microscope. Earth Planet. Sci. Lett. 93, 1-13. 

Linked with its qualities, assessed above, as an imaging and structural tool, the STEM assumes prime importance when considered as a microanalytical instrument. As pointed out in the introduction, the interaction of the fine probe in STEM with, potentially, only a small volume of the sample suggests the possibility of microanalysis on a scale hitherto unattainable. Two main areas will be considered here -the emission of characteristic A -rays by the sample, and the loss of energy from the primary beam in traversing the latter. Ideally, a fully equipped analytical electron microscope will utilize both techniques, since, as a result of the relative positions of A"-ray detector and the energy loss spectrometer in the electron optical column, simultaneous measurements are possible. However, for the sake of convenience we will consider the methods separately. 

Being a primary component of an analytical electron microscope, the choice of the electron source in STEM also has relevance to the performance of the... 

The morphology and composition of the specimens were examined using an AMRAY scanning electron microscope. The sections, of nominal thickness of 15 nm, were examined in a JEOL 200FX II transmission electron microscope. High resolution observation employed a Philips Tecnai 30 FEG analytical electron microscope equipped with EDX and EELS facilities. 

IMAGING AND MICROANALYSIS OF SUPPORTED METAL CATALYSTS IN THE ANALYTICAL ELECTRON MICROSCOPE... 

Scanning transmission electron microscopy gives essentially the same type of results and has the same type of difficulties as the conventional TEM. There are two types of instruments, the dedicated STEMs, which generally have a UHV column, and the TEM based instruments mostly known as AEMs (analytical electron microscopes). A detailed comparison of STEM and TEM was given in Section 2.4.1.3. There are some advantages in using the STEM on polymer samples in particular it seems that thicker samples can be used. However, the added complexity and cost, combined with lower resolution in the AEM STEM mode, make it unlikely that either kind of instrument would be purchased for polymer studies. 

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