EELS Detection Limited by Radiation Damage
/Damage Cross Section in EELS Measurements
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It was proposed [1] that the EELS ionization cross sections are within 5% for most K-edges and 15% for most L-edges, and the accuracy for other edges is significantly uncertain.

In some cases, the damage cross section d) is larger than the K-shel EELS ionization crossK) section, resulting in that the radiation damage prevents the detection of a single atom by K-shel EELS. If σd < σK, single atom detection is possible in principle.

Figure 4403 shows the comparison of the extracted EELS spectra of the N K-edge at 401 eV from a same region with the electron beam current of 150 pA and 850 pA, respectively, and from a crystalline TiN standard sample. Table 4403 shows the comparison of π* pre-peaks of the three cases in Figure 4403. This split is caused by the excitation of an N 1s electron in unoccupied t2g and eg orbitals formed by the hybridization of N 2p and Ti 3d electrons. [2] The high electron beam flux of 850 pA used for the data acquisition changed the chemistry and morphology in the analyzed region.

Extracted EELS spectra of TiN: (a) With the electron beam current of 150 pA, (b) With the electron beam current of 850 pA and (c) from a crystalline TiN standard sample.

Figure 4403. Extracted EELS spectra of TiN: (a) With an electron beam current of 150 pA, (b) With an electron beam current of 850 pA and (c) from a crystalline TiN standard sample. [2]

Table 4403. π* pre-peak of the three cases in Figure 4403.

  π* pre-peak
With an electron beam current of 150 pA Appears to be weaker and no split
With an electron beam current of 850 pA Appears to be much stronger and more defined and is split by 2 eV
From a crystalline TiN standard sample

 

 

 

 


 

 

 

 

 

 

 

 

 

[1] Egerton, R. F. (1993) Oscillator-strength parameterization of inner-shell cross sections. Ultramicroscopy 50, 13–28. 
[2] P. Longo, H. Zhang and R.D. Twesten, Simultaneous DualEELS and EDS Analysis Across the Ohmic Contact Region in FinFET Electronic Devices – Exploring the Effects of Electron Beam Damage, Microsc. Microanal. 22 (Suppl 3), 2016.

 

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