Atomic-resolved high-resolution transmission

Figure 19.12 Atomic-resolved high-resolution transmission electron microscopy image of P-Mn02 nanorod, showing that the surface of single crystalline P-Mn02 nanorod is covered with a 2.5 nm-thin surface layer...

Transmission Electron Microscopy (TEM) is a standard laboratory technique. TEM is indispensable tool for high resolution observation of very fine structures on material smface. The resolution of TEM is abou one order of magnitude better than that of SEM. It corresponds to 1 nm. There exist also high resolution transmission microscopes (HRTEM) with a resolution down to 0.1 nm, capable to resolve individual atomic lattice planes. Samples must be stable enough to withstand the electron beam impact during their examination. This can be a problem for polymers. 

Figure 20 Left High-resolution transmission electron micrograph image of a single PtMo (3 1) nanoparticle on the edge of a carbon black primary particle (111) and (100) fades are clearly resolved. Right Distribution Pt (light) and Mo (dark) atoms in an fee cubo-octahedral particle containing 1806 Pt atoms and 600 Mo atoms from classical Monte Carlo simulation at 550 K.

Hansen PL, et al. Atom-resolved imaging of dynamic shape changes in supported copper nanocrystals. Science 2002 295 2053-5. http //dx.doi.org/10.1126/science.1069325. Imamov RM, Klechkovskaya VV, Suvorova El. High-resolution transmission electron microscopy for crystallographic study of nanomaterials. Crystallography Reports 2011 56 650-61. http //dx.doi.or l0.1134/s1063774511040079. 

Until recently the only satisfactory way to separate these molecular interferences has been on the basis of nuclear mass defects, i.e., the mass of molecules having the same mass number differs from that of the atoms of the same mass number. Figure 2 shows the resolution that is needed to resolve the molecular impurities present in the previous example. Clearly, an unambiguous identification can be made, and all molecular fragments can only be eliminated for an instrument with resolution M/AM approximately 20,000. Once again, the need for high resolution will cause the transmission efficiency to be low. 

The transmission electron microscope (TEM) is a choice instrument for the characterization of materials and devices at the nanoscale. Nanoparticles shape, and distribution can easily been determined by conventional TEM while the atomic resolution in real space capability offers the possibility to resolve their structure. In addition to this high intrinsic spatial resolution, TEM offers a number of signals which can be exploited to obtain chemical and stmctural information concerning the specimen (see, for example, Wang, 2000 ). Recent years have... 

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