Energy-loss- and thickness-dependent contrast in atomic-scale electron energy-loss spectroscopy
- Univ. de Toulouse, Cedex (France); National Institute of Standards and Technology, Gaithersburg, MD (United States)
- Monash Univ., Melbourne, VIC (Australia)
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, and Peter Grunberg Institute, Julich (Germany)
- Brookhaven National Lab. (BNL), Upton, NY (United States)
Atomic-scale elemental maps of materials acquired by core-loss inelastic electron scattering often exhibit an undesirable sensitivity to the unavoidable elastic scattering, making the maps counter-intuitive to interpret. Here, we present a systematic study that scrutinizes the energy-loss and sample-thickness dependence of atomic-scale elemental maps acquired using 100 keV incident electrons in a scanning transmission electron microscope. For single-crystal silicon, the balance between elastic and inelastic scattering means that maps generated from the near-threshold Si-L signal (energy loss of 99 eV) show no discernible contrast for a thickness of 0.5λ (λ is the electron mean-free path, here approximately 110 nm). At greater thicknesses we observe a counter-intuitive “negative” contrast. Only at much higher energy losses is an intuitive “positive” contrast gradually restored. Our quantitative analysis shows that the energy-loss at which a positive contrast is restored depends linearly on the sample thickness. This behavior is in very good agreement with our double-channeling inelastic scattering calculations. We test a recently-proposed experimental method to correct the core-loss inelastic scattering and restore an intuitive “positive” chemical contrast. The method is demonstrated to be reliable over a large range of energy losses and sample thicknesses. The corrected contrast for near-threshold maps is demonstrated to be (desirably) inversely proportional to sample thickness. As a result, implications for the interpretation of atomic-scale elemental maps are discussed.
- Research Organization:
- Energy Frontier Research Centers (EFRC) (United States). Energy Materials Center at Cornell (EMC2); Brookhaven National Lab. (BNL), Upton, NY (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- SC00112704; AC02-98CH10886; DESC0001086
- OSTI ID:
- 1182480
- Alternate ID(s):
- OSTI ID: 1180507
- Report Number(s):
- BNL-107273-2014-JA; PRBMDO; R&D Project: 16060; KC0403020
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Vol. 90, Issue 21; ISSN 1098-0121
- Publisher:
- American Physical Society (APS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
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