Sub-Ångstrom electric field measurements on a universal detector in a scanning transmission electron microscope

Abstract

Scanning transmission electron microscopy (STEM) excels in accessing atomic-scale structure and chemistry. Enhancing our ability to directly image the functionalities of local features in materials has become one of the most important topics in the future development of STEM. Recently, differential phase contrast (DPC) imaging has been utilized to map the internal electric and magnetic fields in materials from nanoscale features such as p–n junctions, skyrmions, and even from individual atoms. Here, we use an ultra-low noise SCMOS detector in as the diffraction plane camera to collect four-dimensional (4D) datasets. The high angular resolution, efficient high-SNR acquisition, and modifiability of the camera allow it to function as a universal detector, where STEM imaging configurations, such as DPC, bright field, annular bright field, and annular dark field can all be reconstructed from a single 4D dataset. By examining a distorted perovskite, DyScO3, which possesses projected lattice spacings as small as 0.83 Å, we demonstrate DPC spatial resolution almost reaching the information limit of a 100 keV electron beam. In addition, the perovskite has ordered O-coordinations with alternating octahedral tilts, which can be quantitatively measured with single degree accuracy by taking advantage of DPC’s sensitivity to light atoms. The results, acquired on a standard Ronchigram camera as opposed to a specialized DPC detector, open up new opportunities to understand and design functional materials and devices that involve lattice and charge coupling at nano- and atomic-scales.

Four-Dimensional Scanning Transmission Electron Microscopy (4D-STEM): From Scanning Nanodiffraction to Ptychography and Beyond

“…Figure 7d shows a 4D-STEM DPC measurement of a multilayer BiFeO 3 /SrRuO 3 /DyScO 3 stack performed by Tate et al (2016). Hachtel et al (2018) measured octahedral tilts in the distorted perovskite DyScO 3 , which are plotted in Figure 7e. These and other literature examples such as Krajnak et al (2016), Nord et al (2016), and Müller-Caspary et al (2018a) show that 4D-STEM DPC is becoming a widespread tool for easy phase contrast measurements in STEM over a large range of length scales.…”

“…d: Simultaneous measurements of ADF image, DPC signal from segments, and COM DPC signal from a multilayer stack, adapted from Tate et al (2016). e: DPC measurements of octahedral tilts in DyScO 3 , from Hachtel et al (2018). and we expect it to find widespread use once dedicated "hollow" pixelated STEM detectors are widely available.…”

Sub-100 nanosecond temporally resolved imaging with the Medipix3 direct electron detector

“…A further implication from our study relates to STEM imaging. Pixelated detectors have become recently employed as "universal" detectors [35,36,37,38] in STEM mode. We propose that our results show potential for the application of hybrid pixel detectors to achieve ultimate sensitivity in STEM imaging of beam sensitive materials with the lowest possible electron doses.…”

Probing local order in multiferroics by transmission electron microscopy

“…Additionally, the sub-Ångström resolving power achievable thanks to the new generation of aberration-corrected microscopes [42] these investigations at atomic resolution. Up to date, DPC in the Lorentz STEM mode has been successfully employed to probe magnetic [15,[43][44][45][46][47] and electric fields [48][49][50] at the nanoscale, whereas DPC STEM at high-resolution has been employed to map electric fields at atomic resolution [51][52][53][54]. The DPC-STEM technique makes use of the deflection of the focused electron probe by a field in the sample to locally map this field.…”

“…This approach is commonly called 4D-STEM since it involves the acquisition of a two-dimensional (2D) diffraction image for each position of the raster scan -performed over a 2D grid of scan points across the region of interest CoM of the specimen. The acquisition of the entire Ronchigram also allows a posteriori integration of the scattered signal over different angular ranges of the CBED pattern to generate different signals, like e. g. bright-field (BF), annular bright-field (ABF), annular dark-field (ADF) [54,[62][63][64]. This very powerful feature makes 4D-STEM the most promising approach to combine differential phase-contrast and other imaging techniques in STEM mode, at the expense of a remarkable increase in the volume of generated data [65,66].…”