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 evaluate a proposed procedure for calibration of the binding energy (BE) scales on x-ray photoelectron spectrometers. The calibration was performed at two points on the BE scale (the Au 4f(7/2) and Cu 2p(3/2) lines) and checks were made of the assumption of BE-scale linearity from measurements 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 backgrounds of non-zero slope or if multipeak fits are made to Cu L(3)VV and Ag M(4)VV Auger spectra. The two parameters in the linear calibration equation could vary with analyzer pass energy and choice of x-ray source on a particular instrument. Check measurements of the calibrations 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 positions of these lines and the corresponding reference data were satisfactorily small in most cases. For Auger lines excited by monochromatized aluminum x-rays, however, the differences were significant and were interpreted in terms of different average x-ray energies for the monochromated and unmonochromated x-ray sources. The interlaboratory comparison was useful in testing the proposed calibration procedure and in providing guidance for some improvements.