ENERGY CALIBRATION OF X-RAY PHOTOELECTRON SPECTROMETERS - RESULTS OF AN INTERLABORATORY COMPARISON TO EVALUATE A PROPOSED CALIBRATION PROCEDURE

Results are reported of an interlaboratory comparison conducted to eva luate a proposed procedure for calibration of the binding energy (BE) scales on x-ray photoelectron spectrometers. The calibration was perfo rmed at two points on the BE scale (the Au 4f(7/2) and Cu 2p(3/2) line s) and checks were made of the assumption of BE-scale linearity from m easurements on other lines. It is shown here that small offsets (up to similar to 0.05 eV) can arise if peaks are located with assumed backg rounds of non-zero slope or if multipeak fits are made to Cu L(3)VV an d Ag M(4)VV Auger spectra. The two parameters in the linear calibratio n equation could vary with analyzer pass energy and choice of x-ray so urce on a particular instrument. Check measurements of the calibration s were performed with the Ag 3d(5/2) photoelectron line and the Cu L(3 )VV and Ag M(4)VV Auger lines; differences between the corrected posit ions of these lines and the corresponding reference data were satisfac torily small in most cases. For Auger lines excited by monochromatized aluminum x-rays, however, the differences were significant and were i nterpreted in terms of different average x-ray energies for the monoch romated and unmonochromated x-ray sources. The interlaboratory compari son was useful in testing the proposed calibration procedure and in pr oviding guidance for some improvements.