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Slice thickness optimization for the focused ion beam-scanning electron microscopy 3D tomography of hierarchical nanoporous gold
Citation Link: https://doi.org/10.15480/882.4272
Publikationstyp
Journal Article
Date Issued
2022
Sprache
English
TORE-DOI
Journal
Volume
5
Issue
2
Start Page
112
End Page
118
Citation
Nanomanufacturing and Metrology 5 (2): 112–118 (2022)
Publisher DOI
Scopus ID
Publisher
Springer Singapore
The combination of focused ion beam (FIB) with scanning electron microscopy (SEM), also known as FIB-SEM tomog raphy, has become a powerful 3D imaging technique at the nanometer scale. This method uses an ion beam to mill away a thin slice of material, which is then block-face imaged using an electron beam. With consecutive slicing along the z-axis and subsequent imaging, a volume of interest can be reconstructed from the images and further analyzed. Hierarchical nanoporous gold (HNPG) exhibits unique structural properties and has a ligament size of 15–110 nm and pore size of 5–20 nm. Accurate reconstruction of its image is crucial in determining its mechanical and other properties. Slice thickness is one of the most critical and uncertain parameters in FIB-SEM tomography. For HNPG, the slice thickness should be at least half as thin as the pore size and, in our approach, should not exceed 10 nm. Variations in slice thickness are caused by various microscope and sample parameters, e.g., converged ion milling beam shape, charging efects, beam drift, or sample surface roughness.
Determining and optimizing the actual slice thickness variation appear challenging. In this work, we examine the infuence of ion beam scan resolution and the dwell time on the mean and standard deviation of slice thickness. After optimizing the resolution and dwell time to achieve the target slice thickness and lowest possible standard deviation, we apply these parameters to analyze an actual HNPG sample. Our approach can determine the thickness of each slice along the z-axis and estimate the deviation of the milling process along the y-axis (slow imaging axis). For this function, we create a multi-ruler structure integrated with the HNPG sample.
Determining and optimizing the actual slice thickness variation appear challenging. In this work, we examine the infuence of ion beam scan resolution and the dwell time on the mean and standard deviation of slice thickness. After optimizing the resolution and dwell time to achieve the target slice thickness and lowest possible standard deviation, we apply these parameters to analyze an actual HNPG sample. Our approach can determine the thickness of each slice along the z-axis and estimate the deviation of the milling process along the y-axis (slow imaging axis). For this function, we create a multi-ruler structure integrated with the HNPG sample.
Subjects
Focused ion beam
Scanning electron microscopy
Tomography
Hierarchical nanoporous gold
DDC Class
540: Chemie
600: Technik
620: Ingenieurwissenschaften
Funding Organisations
More Funding Information
This work was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Founda tion) - Project SFB 986 -Tailor-Made Multiscale Materials Systems, subproject B9 - Microstructure-based classifcation and mechanical analysis of nanoporous metals by machine learning.
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