TEM measurements were carried out to investigate the microstructure of both the reference and irradiated samples, revealing that the reference films are highly defected with a high density of dislocations and loops, as shown in
Fig. 1. Cross-sectional TEM samples were prepared from the deposited Fe films by the focused ion beam (FIB) lift-out method. The lift-outs were created with a FEI Quanta 3D FEG Dual Beam SEM/FIB, with a Ga ion source capable of energies up to 30 kV. Final thinning was done at 2 keV to reduce the Ga beam damage before examination in the TEM. After preparation, the TEM samples were imaged using both a JEOL JEM-ARM200CF and FEI
Talos F200X G2 analytical for the unirradiated samples. For the irradiated samples, the JEOL ARM200CF was used in TEM mode to measure the defect distribution, with images taken using a Gatan
Orius SC200D camera and the Gatan Microscopy Suite v3.3. TEM BF images were acquired at under- and over-focused conditions with a defocus value of 2.36 μm to observe the cavities present in the samples. The under-focused images were selected to measure the size and density of the cavities. In the under-focused TEM images, cavities appear predominantly as white circles encircled by a darker Fresnel fringe. The cavity size was measured as the inner diameter of the dark fringe surrounding the white dots (
39 ).
Agarwal S., Liedke M.O., Jones A.C., Reed E., Kohnert A.A., Uberuaga B.P., Wang Y.Q., Cooper J., Kaoumi D., Li N., Auguste R., Hosemann P., Capolungo L., Edwards D.J., Butterling M., Hirschmann E., Wagner A, & Selim F.A. (2020). A new mechanism for void-cascade interaction from nondestructive depth-resolved atomic-scale measurements of ion irradiation–induced defects in Fe. Science Advances, 6(31), eaba8437.