Energy calibration adventitious carbon

For insulating materials, on the contrary, the Fermi level lies in the gap, so that it is not detected on the photoelectron spectra. A possible calibration method stems from the gold decoration technique the binding energies can then be referred to the Au 4f doublet. This leads, however, to a poor reproducibility of the calibration Neither is the 1 s line of adventitious carbon a better energy standard. 

Seah et al. [20,32] have addressed the calibration of the intensity/energy response function for valid analytical measurements with electron spectrometers used in XPS and AES. Both techniques have matured to a sufficient level that calibration systems are now available which allow spectral intensities to be related from instrument to instrument. The KE axis is usually calibrated with reference to a signal belonging to an internal calibrant, e.g. the Cl - level of adventitious carbon due to pump oil or the Au4/7/2 level of gold vacuum-deposited on the sample. 

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