Coating techniques imaging

FFTEM samples can also be prepared [29] by a double-replica freeze-fracture technique, in which a drop of sample is deposited on a metal disk. A second disk is then placed on top, and the two disks are centered. A further drop is placed in the central bore of the specimen sandwich, any excess sample being removed with filter paper. The sample is plunged into liquid cryogen and transferred to the cleavage unit of the microscope, also maintained under cold conditions. The sample is subsequently cleaved, etched, coated, and imaged. 

The resulting crystalline film of matrix is fairly homogeneous (Fig. 17.4b) and allows imaging by MALDI MS with spatial resolutions as small as 30 p,m (13). Further, because of its simplicity, this matrix coating technique is easily applicable to larger whole-body tissue sections. Since matrix is applied dried on the section, this eliminates any risks of analyte delocalization. 

Gd converter can be used. Both techniques were studied and compared with the common direct neutron imaging with Gd metal converter (0.1mm thick) and single coated fine grained radiographic film, exposed in a vacuum cassette. The unprotected IP ( TR type ) in combination with the Gd metal converter were also exposed in a vacuum cassette. Our experience can summarized as follows ... 

In contrast to the older techniques, a newer method is to use a scanning tuimeling electron microscope to deposit metal coatings in microscopic images as small as 0.001 pm. The ultimate surface metallization techniques allow deposition of metals atom by atom in controlled three-dimensional arrays. 

Today dynamic SIMS is a standard technique for measurement of trace elements in semiconductors, high performance materials, coatings, and minerals. The main advantages of the method are excellent sensitivity (detection limit below 1 pmol mol ) for all elements, the isotopic sensitivity, the inherent possibility of measuring depth profiles, and the capability of fast direct imaging and 3D species distribution. 

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