A MICROSCANNING ELECTRON-MICROSCOPE IN ULTRAHIGH-VACUUM FOR SURFACE MICROANALYSIS

A microscanning electron microscope (SEM) column has been constructed as an attachment of an ultrahigh-vacuum chamber with a 70 mm diam flange to observe microstructures on a solid surface. The micro-SEM column is 26 mm diam and 140 mm long and operated in an energy range from 100 eV to 3 keV. It consists of a thermal-field-emission (TFE) gun and two magnetic lenses. The excitation of the objective lens for 3 kV electrons is 250 A T at a working distance of 10 mm. The saturated temperature of the objective lens at the excitation of 250 A T is approximately 50 degrees C and the vacuum of the chamber is 2X10(-10) Ton. The electron probe is adjustable against a specimen position from the outside of the vacuum by movement of the SEM column with screws. The spot size of the electron probe is 100 Angstrom at 3 kV and 3000 Angstrom at 300 eV in conditions of a working distance of 10 mm and a probe current of 3x10(-11) A.