AES Instrumentation: AES Data Display Algorithms

Displaying Auger spectra as differentials enhances the sharp Auger peaks and deemphasizes the relatively intense and structureless background. Strong interfering signals accompany the Auger electrons in all regions of the Auger spectrum. The interference includes contributions from secondary and backscattered electrons, and from Auger electrons that have lost energy as they escape from beneath the sample surface. The first figure shows a typical AES spectrum (of iron) plotted as total electron signal, N(E), versus electron energy. The Auger peaks are obscure even after expanding the vertical scale.

Plotting the spectrum as the differential of the electron signal, dN(E)/dE, clarifies some of the spectral details.

Both of the first two plots under emphasize the high energy end of the spectrum. Multiplying the total electron signal by the electron energy, E x N(E), accentuates the high energies as shown in the next figure.

Finally, plotting the differential, d[E x N(E)]/dE, of the above function provides for clear display of the features in an Auger electron spectrum. This d[E x N(E)]/dE format is the most common mode for presenting Auger data.

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