High resolution specimen preparation

By way of example. Fig. 6.13 shows prepared MID microsections. A great deal of work is involved in this method of testing, because embedding and grinding are generally manual or only partly automated at best and only a very small part of the test specimen can be examined, but on the upside even ultra-fine structures can be studied under suitable high-resolution microscopes. Prepared sections can also be subjected to processes from materials analysis, such as energy-dispersive X-ray spectroscopy (EDX), in order to determine the distribution of individual elements in the solder joint. 

Interpretable high-resolution structural infomiation (e.g. preservation of dimensions, or correlation of the stmctiiral detail with a physiologically or biochemically controlled state) is therefore obtained exclusively from samples in which life has been stopped very quickly and with a sufficiently high time resolution for the cellular dynamics [19]. Modem concepts for specimen preparation therefore try to avoid traditional, chemical... 

Fig. 33. High resolution C(ls) XPS spectra obtained from (A) silver and (B) polymer fracture surfaces of specimens prepared by curing the polyamic acid of PMDA/4-BDAF against polished silver substrates. Reproduced hy permission of the American Chemical Society from Ref. [391.

They employed a FIB of 30 keV Ga ions which as focused to a spot with a diameter which could be varied between 0.05 and 1 pm. The beam current varied with focus size between 13 pA and 1.2 nA, and sputter rate typically increased with beam current from 0.005 to 0.5pm3s 1. The beam control was automated, so that the major part of the specimen preparation was performed automatically, only the final high-resolution operations being carried out by manual adjustment of the milling area. Their preparation scheme was as follows ... 

Specimen preparation. Most HRTEM investigations have used specimens in the form of crushed fracture fragments supported on a holey carbon film attached to a standard copper grid. Specimens thinned by ion (or atom) bombardment are also used, but the amorphous film which tends to form on the surfaces of foils prepared in this way is sometimes too thick for successful high-resolution imaging. See also Section 2.7. 

The details of the structural characteristics of individual constituents in the various carbon deposits were obtained by examination of a number of specimens from each experiment in a JEOL 100 CX transmission electron microscope that was fitted with a high resolution pole piece, capable of 0.18 nm lattice resolution. Suitable transmission specimens were prepared by applying a drop of an ultrasonic dispersion of the deposit in iso-butanol to a carbon support film. In many cases the solid carbon product was found to consist entirely of filamentous structures. Variations in the width of the filaments as a function of both catalyst composition and growth conditions were determined from the measurements of over 300 such structures in each specimen. In certain samples evidence was found for the existence of another type of ca naceous solid, a shell-like deposit in which metal particles appeared to be encapsulated by graphitic platelet structures. Selected area electron diffraction studies were performed to ascertain the overall crystalline order of the carbon filaments and the shell-like materials produced from the various catalyst systems. 

K. R. Peters, Penning Sputtering of Ultra Thin Metal Films for High Resolution Electron Microscopy, in Preparation of Biological Specimens for Scanning Electron Microscopy (eds. J. A. Murphy and G. M. Roomans), SEM, Chicago, 1980, pp. 173-184. 

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