Inelastic mean free path measurement by STEM-EELS technique using needle-shaped specimen.
Ultramicroscopy 2020;
212:112955. [PMID:
32086184 DOI:
10.1016/j.ultramic.2020.112955]
[Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Revised: 12/17/2019] [Accepted: 02/02/2020] [Indexed: 11/30/2022]
Abstract
Inelastic mean free path (IMFP) was determined by electron energy loss spectroscopy (EELS) to estimate the accurate thickness of TEM thin foil using needle-shaped specimen. From EELS measurements performed for 99.99% Al, Si wafer and 99.99% Fe, linear relationships were confirmed between the thickness of the TEM thin foil and the ratio of the total intensity of EELS spectrum to the total intensity of zero-loss spectrum for all samples. By weighted least-square fitting, the IMFP was estimated to be 143-150 nm for Al, 159-165 nm for Si with amorphous layer, and 92-94 nm for Fe with the collection semi-angle β = 11.9 - 35.7 mrad, and accelerated voltage of 200 kV. Thus, the dependence of IMFP on β is not dominant. The accuracy depends on the roundness of the cross-section of the needle-shaped specimen, and is observed to be low in terms of percentage in this work.
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