Quantitative APT analysis of Ti(C,N)

A specially produced Ti(C,N) standard material, with a known nominal composition, was investigated with laser assisted atom probe tomography. The occurrence of molecular ions and single/multiple events was found to be influenced by the laser pulse energy, and especially C related events were affected. Primarily two issues were considered when the composition of Ti(C,N) was determined. The first one is connected to detector efficiency, due to the detector dead-time. The second one is connected to peak overlap in the mass spectrum. A method is proposed for quantification of the C content in order to establish the C/N ratio. A correction was made to the major C peaks, C at 6 and 12 Da, with the 13C isotopes, at 6.5 and 13 Da, according to the known natural abundance. In addition, a correction of the peak at 24 Da, where C and Ti overlap, is proposed based on the occurrence of single/multiple events for respective element. The results were compared to the results from other techniques such as electron energy loss spectroscopy, chemical analysis and X-ray diffraction. After applying the corrections, atom probe tomography results were satisfactory. Furthermore, the content of dissolved O in Ti(C,N) was successfully quantified.

Research highlights
► We quantify a Ti(C,N) standard material with a specific stoichiometry.
► We evaluate the impact of different laser energies on the mass spectrum.
► A correction method is presented to solve problems with overlap and losses of counts in major peaks.
► APT analysis as a quantitative tool was compared with other techniques such as EELS, X-ray diffraction (XRD) and chemical analysis.