The quantitative analysis performance of carbon and nitrogen was investigated using stoichiometric θ-Fe3C (25 at% C) and γ′-Fe4N (~20 at% N) precipitates in pulsed voltage and pulsed laser atom probes. The dependencies of specimen temperature, pulse fraction, and laser pulse energy on the apparent concentrations of carbon and nitrogen were measured. Good coincidence with 25 at% carbon concentration in θ-Fe3C was obtained for the pulsed voltage atom probe by considering the mean number of carbon atoms per ion at 24 Da and the detection loss of iron, while better coincidence was obtained for the pulsed laser atom probe by considering only the mean number of carbon at 24 Da. On the other hand, a lack of nitrogen concentration in γ′-Fe4N was observed for the two atom probes. In particular, the pulsed laser atom probe showed a significant lack of nitrogen concentration. This implies that a large amount of 14N2+ was obscured by the main iron peak of 56Fe2+ at 28 Da in the mass-to-charge spectrum. Regarding preferential evaporation or retention, carbon in θ-Fe3C exhibited little of either, but nitrogen in γ′-Fe4N exhibited definite preferential retention. This result can be explained by the large difference in ionization energy between carbon and nitrogen.

中文翻译：

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原子探针断层扫描定量分析化学计量θ-Fe3C和γ′-Fe4N中碳和氮的研究

使用化学计量法研究碳和氮的定量分析性能θ-铁3C (25 at% C) 和γ′-铁4N (~20 at% N) 在脉冲电压和脉冲激光原子探针中沉淀。测量了样品温度、脉冲分数和激光脉冲能量对碳和氮表观浓度的依赖性。与 25 at% 的碳浓度吻合良好θ-铁3脉冲电压原子探针通过考虑 24 Da 时每个离子的平均碳原子数和铁的检测损失获得 C，而脉冲激光原子探针仅考虑 24 Da 的平均碳原子数获得更好的一致性大。另一方面，氮浓度不足γ′-铁4对两个原子探针观察到 N。特别是，脉冲激光原子探针显示出显着缺乏氮浓度。这意味着大量14ñ2+被主要的铁峰遮住了56铁2+在质荷谱中的 28 Da。关于优先蒸发或保留，碳θ-铁3C表现出很少的任何一种，但氮在γ′-铁4N 表现出明确的优先保留。这一结果可以用碳和氮之间电离能的巨大差异来解释。