ENERGY CALIBRATION OF X-RAY PHOTOELECTRON SPECTROMETERS - PART III - LOCATION OF THE ZERO-POINT ON THE BINDING-ENERGY SCALE

Calibration of the binding energy scale in x-ray photoelectron spectro scopy (XPS) requires location of the zero point. This zero point has p reviously been identified with the inflection point in the Fermi-edge region of a valence-band photoemission spectrum of nickel. Comparison of photoemission spectra of nickel and silver measured with monochroma ted x-rays shows that the inflection points near the Fermi edge differ by 45 +/- 5 meV (where the stated uncertainty indicates the standard uncertainty) at an instrumental energy resolution of 0.30 eV, This dif ference is due to differences in the valence-band densities of states (DOS) of the two metals. Simulations of the Ni photoemission spectrum have been performed based on the DOS calculated by Eckhardt and Fritsc he, and the simulated spectrum agrees well with the measured spectrum in the near-edge region. Additional simulations of the Ni photoemissio n spectrum have been carried out with both monochromated Al x-rays and unmonochromated Mg and Al characteristic x-rays to determine how the Ni near-edge inflection point varies with the energy resolution of the electron energy analyzer in XPS. (C) 1998 John Wiley & Sons, Ltd.