Fine tuning an aberration corrected ADF-STEM.

Aberration correctors offer greatly enhanced resolution in electron microscopes, however can require dramatically more complicated adjustments. A method of computer adjustment of a probe forming aberration corrector in a Scanning Transmission Electron Microscope (STEM) is proposed and analyzed using image simulation. This method works directly with the image and should work well with crystalline specimens.

Computation in electron microscopy.

Some uses of the computer and computation in high-resolution transmission electron microscopy are reviewed. The theory of image calculation using Bloch wave and multislice methods with and without aberration correction is reviewed and some applications are discussed. The inverse problem of reconstructing the specimen structure from an experimentally measured electron microscope image is discussed.

On the optimum probe in aberration corrected ADF-STEM.

New aberration correctors present new challenges in optimizing (minimizing) the probe size in the STEM (Scanning Transmission Electron Microscope). A small probe is important for high resolution imaging and analytical microscopy. Some effects of aperture size, corrector accuracy, and higher order aberrations on probe size and image artifacts are calculated.

Some effects of electron channeling on electron energy loss spectroscopy.

As an electron beam (of order 100 keV) travels through a crystalline solid it can be channeled down a zone axis of the crystal to form a channeling peak centered on the atomic columns. The channeling peak can be similar in size to the outer atomic orbitals. Electron energy loss spectroscopy (EELS) measures the losses that the electron experiences as it passes through the solid yielding information about the unoccupied density of states in the solid.