The combination of electron microscope and x-ray spectrometer is a very powerful tool. Not only can one see a sample in great detail, but one can determine, and even map, the chemical elements, in Part 1, I discussed some of the basics of energy dispersive x-ray spectroscopy (EDS, EDX). In Part 2,1 went into detail about the construction of the detector, and discussed counting statistics. In this installment I will discuss the interaction between the x-ray and the detecting crystal, things that can go wrong in the process, and the phenomena which can make false peaks in a spectrum.

Microscopy training has always been labor intensive. As the need grew for electron microscopists so did the need for methods of training to maintain quality while increasing the quantity of people trained. Various trends in scientific research needs, development of various types of microscopies, environmental concerns and increasing computer sophistication brought about significant changes in microscopy training and service facilities.

In the 1960's TEM research flourished. Many single user facilities appeared with scopes provided by grant funds, especially in biology. There was a great need for people trained in EM. In the mid 1960's, commercial SEMs became available, and SEM research flourished.

Kent Christensen documents the values of glass photographic plates1 and also their demise. As a former user of glass plates for microscopy, radiography, autoradiographyandspectroscopy, I sympathize with Kent. Today there are substitute sheet and or roll films for most of the glass plate applications. For example, [ have found Kodak's "Trnax" films as sensitive as lantern plates for soft X-rays and nearly as good for resolution. Tmax is also a good general purpose emulsion for the laboratory, with the possibility of reversal development for slides and availability in a range of formats including 120 and four by five. Perhaps we should recognize the passing of the glass plate as part of current times and inscribe "RIP" over our hallowed collection of glass negatives. After all, many predict that electronic photography will eventually replace all forms of chemical photography.

Teaching a large number of students simultaneously to use a scanning electron microscope (SEM) has traditionally been difficult. A typical classroom scenario would be of one student seated in front of the SEM next to the instructor while the remaining students stand idly behind the operating student. The truth of the oft repeated sentiment expressed by microscopists, "There is nothing more boring than watching someone else do microscopy", would be proven time and time again in such training sessions as the uninvolved students would quickly lose interest and either fall asleep or talk among themselves.

With the complexity of polycrystalline materials, a number of techniques have evolved to assist in the resolution of the crystallography of these materials. Conventional methods provide partial information regarding grain size, and can produce estimated orientation distributions. However, these techniques have not been able to provide the spatial placement of lattice orientations, which is necessary for a complete picture of the microstructure of a materials sample. Furthermore, many materials characteristics, such as fracture and corrosion, are determined by site-specific, rather than average, crystal lographic features.

The following image is of a LaB6 crystal formation created at the FEI Company, Hillsboro, Oregon. The photograph was taken through a Bausch & Lomb Stereo Zoom 4 at 30X with a Polaroid MicraCam.

The single crystal LaB6 and CeB6 is grown and fabricated at FEI using a well-defined process known as "Inert Gas Arc Float Zone Refining." This process takes place in an inert gas atmosphere and utilizes an electrical arc to melt the hot, pressed powder sample of LaB6 or CeB6. This not only allows the growth of the crystal, but also hefps to purify the material. Through research and 20 years of experience in the growth of rare-earth boride single crystals, FEI can carefully control the material composition (e.g. stoichiometry of B/La) tor the highest possible ratio of electron emission to evaporation rate.

Some 350 years before the invention of photography, Leonardo DaVinci may very well have produced the first photograph - the Shroud of Turin. This extraordinary hypothesis attracted shroud experts Lynn Picknett and Clive Prince, and their efforts to prove or disprove this theory resulted in their recent book Turin Shroud. During their shroud investigations, the authors delved deeply into historical lore, piecing together diverse facts and opinions including those of such figures as the Knights of Templar, alchemists, secret societies, and even Pope innocent VIII. The authors provided convincing evidence that the shroud could have been produced using photograph i c -like techniques that were within the identified capabilities of DaVinci. Most importantly, the authors were able to recreate shroud "look-alike" images with materials and techniques believed to be available to, or devised by, Leonardo DaVinci in the creation of the Turin Shroud.

Scanning probe microscopes (SPMs) designed to fit into scanning elec- tron microscopes (SEMs) are now becoming commercially available and you might ask, "Why would I want to put an SPM in my SEM"? The primary reason is that the too forms of microscope are very complimentary. Each microscope extends the power of the other. The SEM can do things that are hard to do with an SPM, and vice versa.

Not long after the introduction of the STM and the AFM, a few re- searchers built custom SPMs and installed them in their SEMs. The reports of these projects to build hybrid microscopes and examples of the data they produced can be found in the scientific literature.

One way to improve upon the detection limits for digital images involves increasing the number of counts per pixel. Eight bits, or 1 byte (256 counts), per pixel is most commonly used for monochrome optical, electron and x-ray imaging. This number is well matched to the human eye which can discern approximately 128 gray values, while photographic and some laser printer outputs have the capability of displaying nearly 256 gray values. When the counts exceed 8 bits/pixel the recorded image file size will likely double to 16 bits/pixel. With the better imaging detection limits we are faced with the technical problem of how to view more than 256 gray levels.