A new high-resolution Electron Energy-Loss Spectroscopy microscope

Boersch, Geiger and coworkers constructed high resolution electron energy-loss spectroscopy (EELS) instruments. These had a very high energy resolution of approximately 3meV, but were operated at a relatively low accelerating voltage of about 30kV and could only obtain spectra from specimen areas greater than about 10µm in diameter.We have been developing a new EELS instrument to investigate detailed electronic structures and thermal vibrations by taking spectra from specified small specimen areas and specified small reciprocal space areas. Our EELS microscope is composed of a thermal-type field emission gun, a Wien-filter monochrometer, the basic part of a JEM-1200EX microscope, a Wien-filter analyzer and a CCD detection system (Fig.1). Figure 2 schematically shows an xy-section of the Wien filter. The filter was designed to produce the Wien condition E=vxB (E:electric field, B:magnetic field, v:velocity of electrons) not only in the filter but also in the fringing field regions and to produce the stigmatic focus. The length of the filter was chosen to be 4cm.