Laser-assisted atom probe tomography of 15N-enriched nitride thin films for analysis of nitrogen distribution in silicon-based structure

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

“…However, by replacing 14 N with 15 N, most overlaps in the mass spectrum can be avoided without making any significant change to the chemistry of the material. A similar study on FeN enriched in 15 N by Sha et al [26], and more recent studies of isotopic enrichment in SiO2 and SiN using 18 O and 15 N by Kinno et al [27,28], have been conducted. In this paper, we show that the most abundant isotopes of Si and N can be separated in the APT mass spectrum using TiSi 15 N thin solid films produced by cathodic arc deposition.…”

“…2 (a). Peaks of particular interest, such as 15 N + , 15 N 2 + , 15 N 2 2+ , 28 Si + , 28 Si 2+ , and 28 Si 15 N 2 2+ , as well as the isotopic signature of Ti 2+ , Ti 3+ , and Ti 15 N 2+ , have been tagged. The Ti and TiN isotopic signatures consist of five visible peaks each, where the center peak is significantly larger than the surrounding four.…”

“…These overlaps cannot be avoided without also substituting nat Si with 28 Si, but as the natural abundance of 28 Si is 92.2 at. % and that of 30 Si is 3.1 at.…”

“…The composition sensitivity and high spatial resolution of APT make it an excellent analytical instrument for the task outlined above. However, due to the severe mass spectral overlaps of the 14 N and 28 Si peaks, few attempts to study TiSiN using APT have hitherto been made, and these yielded inconclusive results [21,24]. The peaks of 14 N + and 28 Si 2+ are only separated by 0.0145 Da, making them practically impossible to separate with commercially available atom probes at present, even though they can be partly resolved under favorable conditions [25].…”

“…However, due to the severe mass spectral overlaps of the 14 N and 28 Si peaks, few attempts to study TiSiN using APT have hitherto been made, and these yielded inconclusive results [21,24]. The peaks of 14 N + and 28 Si 2+ are only separated by 0.0145 Da, making them practically impossible to separate with commercially available atom probes at present, even though they can be partly resolved under favorable conditions [25]. However, by replacing 14 N with 15 N, most overlaps in the mass spectrum can be avoided without making any significant change to the chemistry of the material.…”