Multislice simulation of transmission electron microscopy imaging of helium bubbles in Fe

Journal Article · Thu Oct 04 04:00:00 EDT 2012 · Journal of Electron Microscopy, 61(6):393-400

DOI:https://doi.org/10.1093/jmicro/dfs065· OSTI ID:1060661

Yao, Bo; Edwards, Danny J; Kurtz, Richard J; Odette, George R; Yamamoto, Takuya

Formation of nanoscale helium (He) bubbles in reduced activation ferritic/martensitic steels may lead to degradation of mechanical properties of materials. Transmission electron microscopy (TEM) has been commonly used to image the Fresnel contrast of He bubbles using a defocus of 0.5 µm ~ 1 µm. This paper presents our study of multislice simulation of the size correlation between imaged Fresnel rings and the actual He bubbles. It was found that for bubbles equal to or larger than 3 nm in diameter, the imaged bubble size, represented by its inner diameter of the first dark Fresnel ring (Din) in under-focused imaging conditions, increases with increasing electron-beam incoherency, but decreases with increasing defocus. The electron-beam accelerating voltage, bubble size, bubble position, and TEM sample thickness were found to have no significant influence on the deviation of Din from the actual bubble size (D0). For bubbles equal to or smaller than 2 nm, however, Din/Do increases dramatically with increasing defocus when it is above a threshold defocus. It was also suggested by this study that He bubbles can be differentiated from argon (Ar) bubbles by contrast differences.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1060661
• Report Number(s): PNNL-SA-87416; AT6020100
• Journal Information: Journal of Electron Microscopy, 61(6):393-400, Journal Name: Journal of Electron Microscopy, 61(6):393-400
• Country of Publication: United States
• Language: English