Description
Transmission electron microscope(TEM) has achieved sub-Å spatial resolution owing to the breakthrough of spherical aberration correction technology. Accurate determination of spherical aberration coefficient (𝐶30) is a necessary condition for correction of spherical aberration corrector. An improved method proposed here is to traverse the focal plane while varying the position of a small condenser aperture. The probe and corresponding scanning image have relative displacement due to the almost linear phase shift within the aperture. The local phase gradient is reconstructed by the image displacements, and the 𝐶30 on the focal plane of the lens is successfully recovered.
