Detectors—The ongoing revolution in scanning transmission electron microscopy and why this important to material characterization

Abstract

Detectors are revolutionizing possibilities in scanning transmission electron microscopy because of the advent of direct electron detectors that record at a high quantum efficiency and with a high frame rate. This allows the whole back focal plane to be captured for each pixel in a scan and the dataset to be processed to reveal whichever features are of interest. There are many possible uses for this advance of direct relevance to understanding the nano- and atomic-scale structure of materials and heterostructures. This article gives our perspective of the current state of the field and some of the directions where it is likely to go next. First, a wider overview of the recent work in this area is given before two specific examples of its application are given: one is imaging strain in thin films and the other one is imaging changes in periodicity along the beam direction as a result of the formation of an ordered structure in an epitaxial thin film. This is followed by an outlook that presents future possible directions in this rapidly expanding field.

Probing Multiscale Disorder in Pyrochlore and Related Complex Oxides in the Transmission Electron Microscope: A Review

“…Over the past ∼20 years, sub-angstrom point-resolutions have become readily achievable in (S)TEM instruments, largely due to spherical ( Haider et al, 1998 ) and chromatic aberration-correction ( Batson et al, 2002 ) of electron lenses, and bolstered by improved electron sources as well as mechanical and electrical stability ( Zhu and Dürr, 2015 ). Simultaneously, improvements in electron ( MacLaren et al, 2020 ) and spectroscopic ( Nylese and Rafaelsen, 2017 ; D’Alfonso et al, 2010 ) signal detection technologies have gradually enabled more rapid, and high signal-to-noise data collection ( Hart et al, 2017 ). Paired with intelligent software design, multiple kinds of signals can be correlated to produce rich, multidimensional data cubes that can be flexibly analyzed.…”

Phase Object Reconstruction for 4D-STEM using Deep Learning

“…This is highly relevant especially for investigations of 2D nano structures and organic compounds. To overcome these limitations much effort has been devoted towards the development of fast pixelated electron detectors which can record an entire convergent beam electron diffraction pattern (CBED) in a reasonable amount of time (Tate et al, 2016;Ballabriga et al, 2011b;Ciston et al, 2019;MacLaren et al, 2020;Haas et al, 2021;Jannis et al, 2021). This enables a set of new imaging modalities, such as ptychography, the calculation of phase contrast (Lazić et al, 2016) and true center of mass imaging (Müller et al, 2014).…”

Flexible STEM with Simultaneous Phase and Depth Contrast

“…According to recent theory, tomographic scans acquired with an integrated Center of Mass (iCOM) detector is the most direct way to map the electro-optic refractive index in a sample (Bosch & Lazić, 2019). COM may be defined as the first moment of the projected intensity and is measured conveniently using a pixelated detector in 4D STEM (MacLaren et al, 2020). The refractive index is directly related to the local electric potential, which at sufficient resolution could reveal the atomic number and possibly molecular charge as long as intensity modulations within the primary diffraction disc are taken care of (MacLaren et al, 2015).…”