Demonstration of atomic resolution Z-contrast imaging by a JEOL JEM-2010F scanning transmission electron microscope

The collection of atomic resolution Z-contrast images, using an annular darkfield detector, has until recently been exclusively performed using the dedicated scanning transmission electron microscope (STEM). Here, preliminary results demonstrate the capability of performing this technique with a 200 kV FEGTEM, featuring a Schottky-emission electron gun. As in the dedicated STEM, the microscope's spatial resolution limit, for both Z-contrast imaging and chemical micro-analysis experiments, depends on the objective lens spherical aberration and the source brightness. Images from a number of materials indicate sub-2 Å Z-contrast resolution. In addition, the instrument exhibits probe stability sufficient to observe 1.6 Å lattice fringes in coherent convergent beam electron diffraction (CBED) patterns. Using an electron Ronchigram, a spherical aberration coefficient of 0.5 mm has been measured in STEM alignment for one particular pole-piece. Therefore, higher spatial resolution than that observed here may be possible with a further optimized instrument.