Practical Electron Microscopy and Database

In Electron Energy Loss Spectroscopy (EELS), the quantification of elemental species is fundamentally based on the relationship between the element-specific core-loss signal and the areal density of atoms. The areal density N_k​ of a given element k​ is directly proportional to the core-loss signal I_k​, given by:

-------------------------------------------- [4757a]

where,

I_t​ represents the total spectrum intensity.
σ_k denotes the core-loss edge cross-section for inelastic scattering.

Accurate extraction of I_t​​ from the EELS spectrum requires careful background subtraction, typically achieved through conventional extrapolation techniques to remove the power-law background signal. Alternatively, multiple linear least-squares (MLLS) fitting can be employed to decompose the EELS spectrum into its component signals, allowing for precise quantification even in the presence of overlapping edges.

Figure 4757 shows the N_k as a function of I_t and σ_k. N_k​ is inversely proportional to both I_t​ and σ_k, which reflects the fact that as the total spectrum intensity increases or the cross-section for inelastic scattering becomes larger, fewer atoms are needed to produce the same core-loss signal. The contour plot visually represents this relationship: higher values of N_k​ occur when both I_t​ and σ_k​ are low, while N_k​ decreases as either I_t​ or σ_k​ increases

Figure 4757. Areal density N_k as a function of I_t and σ_k.