LOW-ENERGY ELECTRON-MICROSCOPE OF NOVEL DESIGN

We describe the design of an electron emission microscope capable of imaging a sample surface with low-energy electrons reflected from it or with UV photoelectrons. In the primary beam column provision is made to compensate the energy dispersion of the beam-separating magnet and to be able to choose different primary and secondary beam energies for Auger analysis. The secondary beam column comprises a spherical condenser sector field as energy filter. In order to avoid image aberrations caused by the two sector fields, linked imaging is provided so that intermediate surface images are formed in the deflection centers of the sector fields, while the energy selection is done at pupil positions. The emission lens is an electrostatic tetrode. The electrodes are shaped so as to accommodate an optical Schwarzchild-type mirror objective for visual in-situ observation or UV irradiation of the sample surface. A lateral resolution of about 10 nm is expected with UV photoemission microscopy and somewhat better with reflected electron microscopy.