XPS: Energy calibration of electron spectrometers. 2—Results of an interlaboratory comparison

An interlaboratory test of the NPL calibration values and methodology for the energy scale of XPS instruments, given in Part 1, has been completed. The NPL calibration values are given for the Cu 3p, Au 4f 7/2 , Ag 3d 5/2 , Cu LMM, Cu 2p 3/2 , and Ag MNN peaks for A1 and Mg Kα radiations to an accuracy of 20 me V. Thirteen participants reported with their values for these peaks from seven instrument models representative of four manufacturers. These results are analysed in terms of random errors, voltage scaling errors and zero offset errors. The random errors are the smallest of these errors and amount to 30 me V, showing that instrument users can assign peak positions with very high precision. However, the voltage scaling and zero errors range up to 700 ppm and 1363 me V respectively showing that the weakest link in the commercial measurement chains is in the electronics. It is not clear if this is mainly due to drift in the electronics after the manufacturer's installation or inadequte calibration at that time. A detailed analysis of the measurements confirms the linearity of each of the instrument energy scales to within the accuracy of their random errors.