Low-voltage field-emission scanning electron microscopy applications in nematology

Abstract

Conventional scanning electron microscopy (CSEM) has long been used to gain structural information on the taxonomy, morphology, host-parasite relationships and predators of plant parasitic nematodes. Although a significant amount of new information has accumulated during the past few years, further gains in structural detail will be hampered because CSEMs have resolutions of 40-70A, 5-20kV accelerating voltages are normally required to excite adequate secondary electrons, and current preparation techniques require specimen coatings of 200-300A.Recently a new SEM, the Hitachi S900, combined a condensor-objective lens system with a field emission electron source. This instrument, known as a field emission (FE) SEM, has a resolution of about 5A or 10 times greater than that of CSEMs, can be used to observe specimens with little or no coating and operates at accelerating voltages as low as 1 or 2 kV while producing electron densities nearly 1000 times brighter than those of CSEMs.