Depth sectioning with the aberration-corrected scanning transmission electron microscope

The ability to correct the aberrations of the probe-forming lens in the scanning transmission electron microscope provides not only a significant improvement in transverse resolution but in addition brings depth resolution at the nanometer scale. Aberration correction therefore opens up the possibility of 3D imaging by optical sectioning. Here we develop a definition for the depth resolution for scanning transmission electron microscope depth sectioning and present initial results from this method. Objects such as catalytic metal clusters and single atoms on various support materials are imaged in three dimensions with a resolution of several nanometers. Effective focal depth is determined by statistical analysis and the contributing factors are discussed. Finally, current challenges and future capabilities available through new instruments are discussed.

An expanded approach to noise reduction from high-resolution STEM images based on the maximum entropy method

An expanded use of the maximum entropy method (MEM) is suggested to reduce noise from an experimental high-angle annular dark-field (HAADF) scanning transmission electron microscope (STEM) image. The MEM is combined with an estimate of the standard deviation of noise from an experimental HAADF STEM image and low-pass filtering using the information limit for an incoherent STEM image. Consequently, the present method has just one parameter of a Lagrange multiplier. It is demonstrated that the present method can reduce noise efficiently in high-resolution HAADF STEM images.

The spatial resolution of imaging using core-loss spectroscopy in the scanning transmission electron microscope

The 'delocalization' of inelastic scattering is an important issue for the ultimate spatial resolution of core-loss spectroscopy in the electron microscope. This paper investigates the resolution of scanning transmission electron microscopy images for single, isolated atoms. Images are simulated from first principles using a nonlocal model for electron core-loss spectroscopy. The role of the width of the probe relative to the delocalization of the underlying ionization interaction is considered.