Magnetic Electron Lenses II

Conventional magnetic electron lenses have evolved to their present highly developed state under the pressure of meeting the exacting requirements of high resolution electron microscopy. More recently, however, the desire to extract quantitative analytical information from the specimen has led to significant changes in the design of electron optical systems. The introduction of efficient lanthanum hexaboride cathodes and high beam current field-emission sources has strengthened this tendency. In addition, more complex lens systems than previously envisaged are now possible since microprocessors can be employed to assist in the rapid and reliable readjustment of the lens system, including the extensive alignment procedures. The use of high current density, e.g. superconducting coils, is also paving the way for new lens configurations. Furthermore, the increasing demands placed on the lens systems in electron beam lithography are bound to bring benefits to electron optical systems in general