The first man-made optical instruments were the looking glass, the magnifying glass and the burning glass. These were known by the fifth century BC. The next advance was eighteen centuries later when similar positive lenses were used to correct presbyopia. As lens making technology advanced to fulfill this demand, negative lenses were invented and used to improve the vision of near sighted people. Soon there were spectacle shops dotting Europe, and it was inevitable that people would start to play with combinations of lenses. This all came together at the end of the sixteenth century when the microscope and the telescope were invented in several places independently.

Methods and results reported to our scientific, technical or law enforcement clients and/or presented in a court of law demand the assurance that all work can be duplicated precisely in every detail. The preparation of technical reports that meet high standards for accuracy and completeness are an ethical responsibility and professional obligation for managers of analytical laboratories.

As the extent or complexity of work increases, more methods and techniques may be employed, producing an array of results. The preparation of reports which accurately describe what was done, how it was done, and what was produced can become a significant challenge. The collection, handling, and analysis of physical evidence can seriously impact the search for the truth, as the O.J. Simpson trial has clearly illustrated.

Microscopy remains the primary tool for the analysis and quantification of asbestos in occupational and environmental studies. The American Society for Testing and Materials (ASTM) has recently approved two new Standard Methods for the analysis of asbestos in settled dust. Both methods require the use of a transmission electron microscope (TEM) equipped with an energy dispersive x-ray analysis system. Other methods curently in use require the use of a polarized light microscope {PLM) or phase contrast microscope (PCM).

Over the last several years the long-awaited revolution in direct-digital readout systems has begun, with the introduction of efficient slow-scan CCD cameras. Earlier, the introduction of video cameras to electron microscopes had brought a quantum leap in the speed and efficiency of carrying out a host of operations. The high sensitivity of the video cameras provided the ability to see the image in much more detail and at a lower beam intensity than had been previously possible by viewing the fluorescent screen. The ability to assess, on line, characteristics such as specimen quality and image focus, even qualitatively, gave feedback to the operator that previously took hours to obtain. Due to the low resolution of these video systems, however, they were rarely useful for data recording.

Ion millers are a pain in the neck! They are designed to remove material from the sample. This means: a) that they always remove material from other places too and b) that the material gets deposited somewhere else. The result of this is that ion millers are inevitably high-maintenance instruments.

Therefore it is important to make the most of them when they are in operation. To aid in this quest, two things can be helpful: to get the beam well aligned and to know the milling rate.

An ion gun, however powerful the beam it produces, is of no use if the beam misses the sample. A means of checking the alignment is therefore of great importance.

A good scanning electron microscope is not measured only by its ultimate resolution but often by its flexibility as well. In the real world not many samples require their surface to be examined at 100,000X to 300,000X. Other real considerations are its analytical capabilities, such as EDS and WDS for chemical analyses and its flexibility to handle odd samples or odd applications, such as STEM imaging, electron channeling, cathodoluminescence, etc.

Have you ever wished that the lowest magnification of your SEM wasn't 10X or 20X, but rather 5X or 2X or 1X or even lower? This can be especially useful in a forensic application where large samples are common and cutting them or using other destructive techniques would render the sample useless in court.

The use of infrared microspectroscopy for examining polymer systems has been well known for some time. Fibers, inclusions in polymers and multilayered films have been examined by this technique. One limitation of the technique is the difficulty of sample preparation. A variety of methods have been proposed to prepare the sample including excising an inclusion, microtoming and the use of diamond cells to squeeze the sample into an appropriate thickness. Spectra-Tech purveys a diamond Micro Plane to prepare thin sections of polymers as well as an ATR objective to avoid the necessity of preparing thin sections. Ing Shaw et al. have proposed the use of a fiber microtome to prepare samples and claims that this technique is faster and easier than conventional microtoming.

In the water bucket analogy (Figure 1), the water level in a bucket represents the Fermi level - the highest occupied energy level in the cathode material. The work function is the energy required to get the “water droplets” (electrons) from the top of the liquid out of the bucket and ever the side (i.e., the distance equivalent to the potential energy barrier).

In photoemission, the energy of a photon can remove an electron at the Fermi level from the cathode material and can impart enough kinetic energy of travel to allow it to escape from the bucket (Figure 1a). In thermionic emission, heat provides the energy to boil the electrons off and out of the bucket (Figure 1b). Finally, in field emission, a high electric field can thin the side of the bucket enough so that the electrons can tunnel right through it (Figure 1c). There are two types of field emission: cold field emission (CFE) and Schottky emission (SE).