The electron microscope: the materials characterization tool of the millennium Original Research Article

Transmission and scanning electron microscopes (TEM and SEM) together offer the most complete tool available for the characterization of materials. This combination of TEM and SEM provides surface and internal imaging of all solid materials over a magnification range from 20 000 000× down to 1×, with routine atomic resolution available at the high end and extraordinary depth of focus at the low end. The availability of X-ray spectrometry on both instruments and electron spectrometry on TEMs gives quantitative analysis capabilities covering the whole periodic table [above atomic number (Z)=2], at spatial resolutions from the micrometer to the nanometer scale and analytical sensitivities close to the single-atom level. Complementary electron-diffraction techniques for crystallographic measurements are standard on both instruments. For more than 40 years, since the development of thin-foil preparation techniques, the TEM has grown in versatility and power to the point where it is an indispensable part of a materials research laboratory. Since its commercialization in the mid-1960s the SEM has revolutionized the study of fracture surfaces and, more recently, made crucial contributions to the science and engineering of microelectronic devices to the point where it is an essential presence on commercial fabrication lines. Using references to papers in Acta Metallurgica/Materialia where possible, some of the major contributions of the TEM and SEM to our understanding of materials are looked back at and a few speculations on where electron microscopy of materials is going in the future are ventured.