It has been already pointed out that the medium voltage microscopes of 300kV to 400kV have some advantages in the analytical capabilities of EDS and EELS as compared to those of 200kV). The P/B ratios and the spatial resolution for the analysis will be improved with the increase of the accelerating voltages as well as lattice resolution. In order to improve the spatial resolution of inelastic filtered images, we have recently developed a new 300 kV omega-filter electron microscope with a field emission gun. In the paper, some characteristic features of the new microscope and its application results are described.
The new microscope have a 300kV field emission gun, an omega-filter, EDS, digital STEM, a slow-scan CCD, an imaging plate and TV camera. Some characteristic features of the new microscope are summarized in Table 1. Based on a calculation of probe diameter as a function of probe current at 300kV in a Shottkey type gun with a brightness of 7xl08A/cm2sr and Cs of 0.6mm, a minimum probe size (FWHM) is estimated to be about 0.2nm (Fig. 1).