Convergent beam electron diffraction interferometry using an electron biprism (CBED+EBI)

Abstract

Recently, a new method of interferometry has been realized which is capable of providing important information of crystals, crystal defects and electron-optical information of the microscope such as its spherical aberration surface. The method produces interferograms by using an electron biprism to interfere diffracted beams produced from a small convergent beam probe of ∼10 nm. The electron biprism uses an applied voltage of ∼15 to 100 V to deflect and compensate for the diffracted beam(s) of 2θB (typically ∼5 mrad) (Fig. 1). The biprism ∼0.3 μm dia) is inserted in between and perpendicular to the diffracted beam(s). Two biprism positions were successfully used. An “upper” biprism is placed in the selected area aperture position which is between the objective lens and 1st intermediate lens. A “lower” biprism is further down the optic axis and is placed between the 1st and 2nd intermediate lenses. In Fig. 1, the virtual image of a biprism is shown with respect to the specimen plane.