Analytical Tem

The STEM instrument itself can produce highly focused high-intensity beams down to 2 A if a field-emission source is used. Such an instrument provides a higher spatial resolution compositional analysis than any other widely used technique, but to capitalize on this requires very thin samples, as stated above. EELS and EDS are the two composition techniques usually found on a STEM, but CL, and even AES are sometimes incorporated. In addition simultaneous crystallographic information can be provided by diffraction, as in the TEM, but with 100 times better spatial resolution. The combination of diffraction techniques and analysis techniques in a TEM or STEM is termed Analytical Electron Microscopy, AEM. A well-equipped analytical TEM or STEM costs well over 1,000,000. 

EELS spectra can also be employed to map the distribution of selected elements present in a sample, in the same way that X-ray elemental can be exhibited in analytical TEM experiments. 

The strength of analytical TEM is that compositional information, images, and diffraction data can be simultaneously acquired from the same area of the specimen with a spatial resolution of < 1-2 nm. 

Gu, H., (2004), Evolution of intergranular boundaries and phases in SiC and Si3N4 ceramics under high temperature deformation case studies by analytical TEM , Zeitschrift fur Metallkunde, 95 (4), 271-274. 

Macro refers to macroscopic, large area TEM experiments, micro to microscopic, same area, sequential TKM ejqieriments, while ED refers to analytical TEM using electron diffraction MOss refers to Mdssbauer spectroscopy. 

Akita T, Taniguchi A, Mackawa J, Siroma Z, Tanaka K, Kohyama M, Yasuda K (2006) Analytical TEM study of Pt particle deposition in the proton-exchange membrane of a membrane-electrode-assembly. J Power Sources 159 461 167... 

In summary, to produce a useful probe of subnanometer size, a high-brightness gun is essential together with optimised use of the probe-forming aperture to limit the aberration effects. Among the choice of the various electron sources, the field emission gun stands out. The penalty to be paid for a field emission source is the necessity to use ultra-high vacuum techniques. Such instruments were usually restricted to the dedicated STEM , but nowadays field emission sources are also popular in analytical TEMs. The improvement in the latter has blurred the distinction between dedicated STEM and TEM-STEM . 

The level of chemical information that can be gleaned from XPS and ToF-SIMS is potentially much greater than with analytical TEM but at the expense of spatial resolution. Rather than using a metallographic cross-section one must adopt a plan view specimen orientation, or something close to this geometry. One approach that has been used with a degree of success is to remove the metal sub-... 

Y (2004) Analytical TEM study of CdTe layer electrodeposited from basic ammoniacal aqueous electrolyte. J Electrochem Soc 15EC712... 

Akita T, Okumura M, Tanaka K, Tsubota S, Haruta M (2003) Analytical TEM observation of Au and Ir deposited on rutile TiOj. J Electron Microsc 52 119-124... 

Akita T, TaniguchiA, Maekawa J, SiromaZ, TanakaK eta/. (2006), Analytical TEM study of R particle deposition in the proton-exchange membrane of a membrane-electrodeassembly , J. Power Sources, 159,461-467. D01 10.1016/j.jpowsour.2005.10.111. 

An analytical TEM often has analytical spectrometers like an energy-dispersive X-ray spectrometer (EDS) near objective pole-piece and an electron energy-loss spectrometer (EELS) at the bottom of the microscope. 

Energy dispersive systems are more likely to be incorporated with a TEM or SEM, and wavelength systems, or crystal spectrometers, are more conunonly the basis for an analytical TEM. 

Electron energy-loss spectroscopy analysis of PETP was performed in the analytical TEM to evaluate the possibility of chemical analysis of the polymer at submicrometre scale. Due to irradiation damage, it was necessary to work at the lowest possible electron dose, and with the specimen cooled to liquid nitrogen temperature. In the acquired spectra, an identification of... 

Schumann E, Yang J C, RUhle M and Graham M J (1996), High resolution SIMS and analytical TEM evaluation of alumina scales on NiAl containing Zr or Y , Oxid... 

An elemental composition analysis is also feasible in an analytical TEM based on the physics of chromatic aberration of electrons when they pass through the thin sample. The interactions between the passing electrons and the constituent elements result in various levels of energy loss. An electron energy loss spectroscopy then forms an image showing a characteristic elemental map of the sample based on the atomic absorption of these interactions. 

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