scholarly journals Flexible STEM with Simultaneous Phase and Depth Contrast

2021 ◽  
pp. 1-12
Author(s):  
Shahar Seifer ◽  
Lothar Houben ◽  
Michael Elbaum
Keyword(s):  
System Integration ◽  
Scanning Transmission Electron Microscopy ◽  
Phase Contrast ◽  
Wide Field ◽  
Analog To Digital ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Differential Phase Contrast ◽  
Flexible Stem ◽  
Contrast Image

Recent advances in scanning transmission electron microscopy (STEM) have rekindled interest in multi-channel detectors and prompted the exploration of unconventional scan patterns. These emerging needs are not yet addressed by standard commercial hardware. The system described here incorporates a flexible scan generator that enables exploration of low-acceleration scan patterns, while data are recorded by a scalable eight-channel array of nonmultiplexed analog-to-digital converters. System integration with SerialEM provides a flexible route for automated acquisition protocols including tomography. Using a solid-state quadrant detector with additional annular rings, we explore the generation and detection of various STEM contrast modes. Through-focus bright-field scans relate to phase contrast, similarly to wide-field TEM. More strikingly, comparing images acquired from different off-axis detector elements reveals lateral shifts dependent on defocus. Compensation of this parallax effect leads to decomposition of integrated differential phase contrast (iDPC) to separable contributions relating to projected electric potential and to defocus. Thus, a single scan provides both a computationally refocused phase contrast image and a second image in which the signed intensity, bright or dark, represents the degree of defocus.

Electrostatic potential imaging of phase-separated structures in organic materials via differential phase contrast scanning transmission electron microscopy

Microscopy ◽  
2020 ◽  
Vol 69 (5) ◽  
pp. 304-311
Author(s):  
Shin Inamoto ◽  
Satoru Shimomura ◽  
Yuji Otsuka
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electrostatic Potential ◽  
Scanning Transmission Electron Microscopy ◽  
Phase Contrast ◽  
Organic Materials ◽  
Differential Phase ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Differential Phase Contrast

Abstract Electron staining is generally performed prior to observing organic materials via transmission electron microscopy (TEM) to enhance image contrast. However, electron staining can deteriorate organic materials. Here, we demonstrate electrostatic potential imaging of organic materials via differential phase contrast (DPC) scanning transmission electron microscopy (STEM) without electron staining. Electrostatic potential imaging drastically increases the contrast between different materials. Phase-separated structures in a poly (3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend that are impossible to observe using conventional STEM are clearly visualized. Furthermore, annealing behavior of the phase-separated structures is directly observed. The morphological transformations in the samples are consistent with their physical parameters, including their glass transition and melting temperatures. Our results indicate that electrostatic potential imaging is highly effective for observing organic materials.

scholarly journals Toward quantitative electromagnetic field imaging by differential-phase-contrast scanning transmission electron microscopy

Microscopy ◽  
2020 ◽  
Author(s):  
Takehito Seki ◽  
Yuichi Ikuhara ◽  
Naoya Shibata
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Electromagnetic Field ◽  
Scanning Transmission Electron Microscopy ◽  
Phase Contrast ◽  
Differential Phase ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Differential Phase Contrast ◽  
Field Imaging

Abstract Differential-phase-contrast scanning transmission electron microscopy (DPC STEM) is a technique to directly visualize local electromagnetic field distribution inside materials and devices at very high spatial resolution. Owing to the recent progress in the development of high-speed segmented and pixelated detectors, DPC STEM now constitutes one of the major imaging modes in modern aberration-corrected STEM. While qualitative imaging of electromagnetic fields by DPC STEM is readily possible, quantitative imaging by DPC STEM is still under development because of the several fundamental issues inherent in the technique. In this report, we review the current status and future prospects of DPC STEM for quantitative electromagnetic field imaging from atomic scale to mesoscopic scale.

Magnetic-structure imaging in polycrystalline materials by specimen-tilt series averaged DPC STEM

Microscopy ◽  
2020 ◽  
Vol 69 (5) ◽  
pp. 312-320 ◽  
Author(s):  
Yoshiki O Murakami ◽  
Takehito Seki ◽  
Akihito Kinoshita ◽  
Tetsuya Shoji ◽  
Yuichi Ikuhara ◽  
...  
Keyword(s):  
Magnetic Structure ◽  
Scanning Transmission Electron Microscopy ◽  
Phase Contrast ◽  
Averaging Method ◽  
Polycrystalline Materials ◽  
Diffraction Contrast ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Differential Phase Contrast ◽  
Tilt Series

Abstract Differential phase contrast (DPC) imaging in scanning transmission electron microscopy is a technique to visualize electromagnetic field distribution inside specimens at high spatial resolution. However, diffraction contrast strongly hampers electromagnetic contrast in DPC images especially in polycrystalline samples. In this paper, we develop an imaging technique to effectively suppress diffraction contrast in DPC images. It is shown that a magnetic structure in a Nd–Fe–B permanent magnet was clearly visualized by averaging 64 DPC images with various specimen-tilt conditions. This is because the diffraction contrast in DPC images sensitively and randomly varies with crystal orientation and thus almost vanishes by averaging specimen-tilt image series. We further investigated two types of residual diffraction contrast in the tilt-series averaged DPC images: weak contrast inside grains and strong contrast at grain boundaries. We found that the former can be suppressed by averaging more DPC images, whereas the latter can be suppressed by the tilt-series averaging with wider range of specimen tilt. The tilt-series averaging method enables DPC to visualize electromagnetic structures even inside polycrystalline materials.

Sign in / Sign up

Export Citation Format

Share Document