TY  - JOUR
AU  - Tan, Haiyan
AU  - Zhu, Ye
AU  - Dwyer, Christian
AU  - Xin, Huolin
TI  - Energy-loss-and thickness-dependent contrast in atomic-scale electron energy-loss spectroscopy
JO  - Physical review / B
VL  - 90
IS  - 21
SN  - 1098-0121
CY  - College Park, Md.
PB  - APS
M1  - FZJ-2015-01058
SP  - 214305
PY  - 2014
AB  - 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 counterintuitive 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 counterintuitive “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. Implications for the interpretation of atomic-scale elemental maps are discussed.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000349891100002
DO  - DOI:10.1103/PhysRevB.90.214305
UR  - https://juser.fz-juelich.de/record/187387
ER  -