Resolving mass spectral overlaps in atom probe tomography by isotopic substitutions – case of TiSi15N

Abstract

Mass spectral overlaps in atom probe tomography (APT) analyses of complex compounds typically limit the identification of elements and microstructural analysis of a material. This study concerns the TiSiN system, chosen because of severe mass-to-charge-state ratio overlaps of the N and Si peaks as well as the N and Si peaks. By substituting N withN, mass spectrum peaks generated by ions composed of one or more N atoms will be shifted toward higher mass-to-charge-state ratios, thereby enabling the separation of N from the predominant Si isotope. We thus resolve thermodynamically driven Si segregation on the nanometer scale in cubic phase TiSiN thin films for Si contents 0.08 ≤ x ≤ 0.19 by APT, as corroborated by transmission electron microscopy. The APT analysis yields a composition determination that is in good agreement with energy dispersive X-ray spectroscopy and elastic recoil detection analyses. Additionally, a method for determining good voxel sizes for visualizing small-scale fluctuations is presented and demonstrated for the TiSiN system.

Atom probe tomography field evaporation characteristics and compositional corrections of ZrB2

“…The percentage of multiple events was lower than expected from previous experiences with ceramics, 29.5% for ZrB2.5, and 26.5% for ZrB2.0 for the entire analyses, while ~40 % or more is common in transition metal nitrides [54][55][56][57][58][59], carbides [60,61], carbonitrides [62], and boron carbides [63]. As can be seen in the bar chart Fig.…”

“…The sampling parameters were investigated in accordance with the method described in [54]. The pole region of the stoichiometric ZrB2 specimens influenced the results of the sampling parameter analysis to such an extent that the parameters identified for the B-rich specimens were used for specimens of both films, namely a voxel size of 1.0 nm 3 and an isotropic delocalization 3 -value of 2.0 nm.…”

Development of an Energy-Sensitive Detector for the Atom Probe Tomography

“…Indeed, it can be noticed that the composition of some analyzed materials may involve the evaporation of elements having almost equal mass-to-charge ratios. That is the case, for instance, for nitrogen and silicon in TiSiN systems (Engberg et al, 2018) and in field-effect transistors (Martin et al, 2018), or titanium and carbon in cemented carbide materials (Thuvander et al, 2011). To overcome this limitation, it is necessary to couple the TOF-MS with a new spectroscopy technique that would be able to resolve those interferences, called mass peak overlaps (MPOs).…”

“…It should be noted that a significant part of MPOs concerns elements having both different charge states and different masses (Thuvander et al, 2011; Kirchhofer et al, 2014; La Fontaine et al, 2016; Engberg et al, 2018). Consequently, it can be deduced that a significant number of ions involved in MPOs could be indirectly resolved through the measurement of their kinetic energy [equations (1) and (2)].…”