Weak-beam scanning transmission electron microscopy for quantitative dislocation density measurement in steels

• Published in: Microscopy 2017-04, Vol.66 (2), p.120-130
• Main Authors: Yoshida, Kenta, Shimodaira, Masaki, Toyama, Takeshi, Shimizu, Yasuo, Inoue, Koji, Yoshiie, Toshimasa, Milan, Konstantinovic J, Gerard, Robert, Nagai, Yasuyoshi
• Format: Article
• Language: English
• ISSN: 2050-5698; 2050-5701
• DOI: 10.1093/jmicro/dfw111

To evaluate dislocations induced by neutron irradiation, we developed a weak-beam scanning transmission electron microscopy (WB-STEM) system by installing a novel beam selector, an annular detector, a high-speed CCD camera and an imaging filter in the camera chamber of a spherical aberration-corrected transmission electron microscope. The capabilities of the WB-STEM with respect to wide-view imaging, real-time diffraction monitoring and multi-contrast imaging are demonstrated using typical reactor pressure vessel steel that had been used in an European nuclear reactor for 30 years as a surveillance test piece with a fluence of 1.09 × 1020 neutrons cm-2. The quantitatively measured size distribution (average loop size = 3.6 ± 2.1 nm), number density of the dislocation loops (3.6 × 1022 m-3) and dislocation density (7.8 × 1013 m m-3) were carefully compared with the values obtained via conventional weak-beam transmission electron microscopy studies. In addition, cluster analysis using atom probe tomography (APT) further demonstrated the potential of the WB-STEM for correlative electron tomography/APT experiments.