Static SIMS inter-laboratory study

An inter-laboratory study involving 18 respondees, with 21 static SIMS instruments, has been conducted with a wide variety of spectrometer types. These include quadrupole, magnetic sector and three time-of-flight mass analyser designs, representing an essential cross-section of the main laboratories using static SIMS. This study involved the static SIMS analysis of three reference samples provided by the NPL: poly(tetrafluoroethene), poly(ethene terephthalate) and a thin layer of Irganox 1010 on silver. Respondees recorded data for both positive and negative secondary ions in the static mode and, if time permitted, as a function of the ion fluence. The results of this study show that static SIMS instruments can have excellent repeatabilities of better than 1%. A relative instrument spectral response (RISR) is calculated for each instrument with an average reproducibility of 14%, for the different reference materials and for both ion polarities. The RISR facilitates the transferability and equivalence of data from laboratory to laboratory. This means that spectra have a reproducibility, after correction using the RISR, of ×/÷1.14 compared with a value four times worse with no correction. Problems that lead to variability are the sample handling and sample contamination, the energy band pass of the spectrometer and the mass transmission function of the analyser. However, dominating all of these, at the present time, seems to be the local procedures for set-up and use of each instrument. It is believed that, if these can be improved, static SIMS can be a reliable measurement method.