Efficient linear phase contrast in scanning transmission electron microscopy with matched illumination and detector interferometry

Abstract

The ability to image light elements in soft matter at atomic resolution enables unprecedented insight into the structure and properties of molecular heterostructures and beam-sensitive nanomaterials. In this study, we introduce a scanning transmission electron microscopy technique combining a pre-specimen phase plate designed to produce a probe with structured phase with a high-speed direct electron detector to generate nearly linear contrast images with high efficiency. We demonstrate this method by using both experiment and simulation to simultaneously image the atomic-scale structure of weakly scattering amorphous carbon and strongly scattering gold nanoparticles. Our method demonstrates strong contrast for both materials, making it a promising candidate for structural determination of heterogeneous soft/hard matter samples even at low electron doses comparable to traditional phase-contrast transmission electron microscopy. Simulated images demonstrate the extension of this technique to the challenging problem of structural determination of biological material at the surface of inorganic crystals.

Roadmap on structured light

“…Not only can this lead to new selection rules in electron-atom interactions, but it can also be used for magnetic dichroism at atomic length scales [205][206][207][208][209]. Structured electrons have also recently been used to enhance phase contrast intransmission electron microscopy (TEM), providing the ability to image electron-transparent objects at small beam doses and improved spatial resolution [210].…”

Electron Microscopy with Structured Electrons

“…For example, diffraction holograms can be used in a scanning transmission electron microscope to remove aberrations [1], implement new types of interferometric phase contrast [2,3], and produce electron probes with phase vortices and quantized angular momentum [4,5].We are currently investigating the use of nanoscale gratings for off-axis STEM interferometry ( Figure 1). We have used a single grating in a scanning transmission electron microscope (STEM) to form a pathseparated electron interferometer [6].…”

“…Nanostructured electron optics also can be used to implement new types of on-axis interferometric phase contrast in STEM (Figure 2). For example, in Matched Illumination-Detector Interferometry STEM (MIDI-STEM), a transverse phase modulation is introduced to a STEM probe using a nanostructured phase plate in the probe-defining condenser aperture [2,3]. The diffraction plane of the probe is imaged at each probe position.…”

“…For example, diffraction holograms can be used in a scanning transmission electron microscope to remove aberrations [1], implement new types of interferometric phase contrast [2,3], and produce electron probes with phase vortices and quantized angular momentum [4,5].…”

A Next Generation Electron Microscopy Detector Aimed at Enabling New Scanning Diffraction Techniques and Online Data Reconstruction

“…After data reduction, complete data sets will be handed to a HDF5 file writer and will also be available for online analysis routines. Our goal is to have prompt feedback from more complex analyses, like phase contrast imaging methods such as Matched Illumination and Detector Interferometry (MIDI) [4] and ptychography [5,6]. …”