Complex evaporation behavior of a transition metal carbo-nitride (Hf(C,N)) studied by atom probe tomography.

The use of pulsed lasers in atom probe tomography has enabled the analysis of lower conductivity materials such as hafnium carbo-nitrides. The variability of experimental parameters can have a profound effect on field evaporation behavior, data quality and compositional accuracy. This is especially challenging for materials such as hafnium carbo-nitride, where a mixture of covalent, ionic and metallic bonding types is present. Here we study the influence of laser pulse energy on how the field evaporation evolves in a hafnium carbo-nitride and how that impacts data quality and compositional accuracy. Changing the laser pulse energy, while keeping other parameters constant, alters the resulting composition. A gain in Hf concentration is observed for higher laser pulse energies while at the same time the N concentration decreases. At lower laser pulse energies, the obtained composition is in good agreement with the reference bulk composition of the material. Furthermore, our results demonstrate that assessing the quality of an APT experiment or dataset merely based on commonly used metrics such as quality of mass spectrum, hit distribution on the detector, hit multiplicity and mass resolving power, can be misleading and is not enough to ensure the most accurate compositional data. Moreover, it is shown that the complex evaporation behavior of transition metal carbo-nitrides and potential ion loss mechanisms are not well enough understood yet and further work is required to fully comprehend these complex behaviors in these types of ceramics.