Development and applications of monochromator in transmission electron microscope
ZHOU Yu-sheng, WANG Rong-ming~, SHANG Guang-yi, YAO Jun-en(School of Science, Beihang University, Beijing 100191, China)
With the rapid advances in science and technology, conventional transmission electron microscopes (TEM) with field emission gun operated at 200 kV has achieved point resolution of 0.19～0.25 nm and energy resolution of 0.7～1.0 eV. The resolution is confined by the spherical aberration of objective lens and energy spread of electron source. With the invention of spherical aberration corrector, point resolution of 0.1 nm (1 ) has been obtained. Therefore, the reduction of chromatic aberration becomes the most important factor to improve the information limit and energy resolution. Monochromator in TEM can effectively diminish energy spread of the incident electron beam, consequently reducing the limitation on TEM's performances by chromatic aberration. This paper introduced the principle, construction, performance and applications of several types of Monochromators including Wien type, Ω type and Mandoline type energy filters.