For biologic studies, atomic force microscopy (AFM) has been prevailing over scanning tunneling microscopy (STM) because it has the capability of imaging non-conducting biologic specimens. However, STM generally gives better resolution than AFM, and we're talking about resolution on the atomic scale. In a recent article, Franz Giessibl (Atomic resolution of the silicon (111)- (7X7) surface by atomic force microscopy, Science 267:68-71, 1995) has demonstrated that atoms can be imaged by AFM.

The use of x-ray spectrometry in electron microscopy has been a powerful market driver not only for electron microscopes but also for x-ray spectrometers. More x-ray spectrometers are sold with electron microscopes than in any other configuration. A general name for the combination is AEM, or analytical electron microscope, though in modern times AEM can include other instrumentation such as electron energy loss spectroscopy and visible light spectroscopy. In previous articies I have discussed energy dispersive spectrometers (EDS). These use semiconductor crystals to detect the x-rays and measure the energy deposited in the crystal. A second type of x-ray spectrometer measures the wavelength of the x-rays, and so is called "wavelength dispersive spectrometry" (WDS).

Each year we show hundreds of students and visitors magnified images of common objects in our SEM. the best samples to use in SEM demonstrations for children are those which have detail that can just barely be seen with the naked eye or with a light microscope. Ideally, the sample would be something with which the child is already familiar, and one which can be explored at several different magnifications.

The simplest specimen is a penny attached to a stub by carbon or silver dag. Mount the coin such that the back side, showing the Lincoln Memorial, faces upward As shown in Figure 1, the statue of Lincoln inside the memorial can be seen with the naked eye.

The ability to view thick material using accelerating voltages higher than 100 KeV has greatly expanded the usefulness of electron microscopy. At or above 300 KeV, intact cultured cells and tissue sections as thick as 5µm can be visualized. However, under normal viewing conditions this increased depth produces confusing superposition of structures located at different planes along the Z axis. In order to separate spatial information in different planes, specialized procedures such as stereo pairs or animated tilt series have been employed. Although rapid, these procedures do not allow quantitation of parameters such as size, volume, or circumference. Computed Tomography produces a computer generated 3-D reconstruction from which quantitative data can be easily extracted.

Teaching on-site courses for the McCrone Research Institute has enabled me to see a lot of the USA. The van and I have been to all of the states except Hawaii and Alaska besides all of the Canadian provinces except Newfoundland and the Northwest Territories. Some parts of the USA have become nearly as familiar to me (and van) as the Outer Drive in Chicago, Rte. 1 down the California coast, Rtes. 80 and 90 to New York and New England, 55 and 65 South, 40 Southeast to Los Angeles and 80 to Salt Lake City and San Francisco, in particular. The latter route across the Great Salt Lake Desert is one of my favorites. That route is always different because of the Great Salt Lake. It's a large lake under normal conditions but conditions are never normal.

With the new "L" brackets that are available for the Tripod Polisher™ (South Bay Technology, Inc.) which allow the sample to be easily backlit with room lights, it is relatively easy to grind away most of the material to be removed when polishing the second side of a sample. The following steps outline the procedure that I have been using for rapidly removing material and getting the samples very thin prior to starting the final wedge polishing. The samples that I have been preparing with this technique are approximately 1µm thick, pulsed laser deposited ZnO-WS2 films on SiC substrates.