Developments in space exploration, microelectronics, and other high-tech
industries have promoted cleanroom technology and increased the need to
identify particles sometimes too small to handle with the polarizing light
microscope. Light microscopy has traditionally been the most commonly used
technique for small particle identification and many microscopists are very
proficient in identifying particles using a polarizing light microscope as
the principal investigative tool. The polarizing light microscope, in the
hands of a good microscopist, is an extremely efficient instrument for
particles down to a few micrometers in size. However, in the size range
below 5 pm, an instrumental approach to small particle identification is
essential. The development of electron microbeam instruments in the early
'60s and 70s introduced a new dimension to small particle identification. In
these instruments, particles of 1 urn and smaller can be chemically
identified when chemical characterization of particles is combined with
cathodoluminesence and a relatively simple optical characterization in the
instrument itself.