定量交错脉冲采集扩展ToF-SIMS中同位素比测量的范围

中文摘要 AI 辅助

同位素比是氧化物、电池材料和生物系统中示踪研究的基础，然而飞行时间二次离子质谱（ToF-SIMS）难以量化强度相差数个数量级的同位素比：用于精确计数次要同位素的主离子脉冲若足够长，可能使主要同位素饱和，而用于保持主要同位素线性的短脉冲则导致次要同位素计数过少。我们证明，当在每个弹坑内测量的剂量因子将各阶段联系起来，且每种同位素仅取自其保持线性的阶段时，多脉冲宽度采集能够产生定量的同位素比；我们将此称为定量重建交错脉冲采集。脉冲宽度根据实测的传递曲线和峰形进行选择。在热氧化硅上，经过调谐的（6，35）纳秒脉冲对实现了与短脉冲采集相同的逐层精度，同时分析帧数减少了13倍。在18O富集的WOx薄膜上，交错采集将低丰度端的可量化范围扩展了约14倍。在跨越约1:500至1:1的同位素比范围内，交错重建与相应的线性参考测量结果一致，未显示由交错引入的可测量偏差，并且氧、锶和钛的自然丰度比在几个百分点内得到重现。该方法无需添加硬件，并能够在单个弹坑内实现宽范围内的深度分辨同位素比测量。

英文摘要

Isotope ratios underpin tracer studies of transport in oxides, battery materials, and biological systems, yet time-of-flight secondary ion mass spectrometry (ToF-SIMS) struggles to quantify ratios whose members differ in intensity by orders of magnitude: a primary-ion pulse long enough to count the minor isotope precisely can saturate the major isotope, whereas a pulse short enough to keep the major isotope linear yields too few minor-isotope counts. We show that multi-pulse-width acquisition yields quantitative isotope ratios when a dose factor measured within each crater links the phases and each isotope is taken only from phases in which it remains linear; we call this quantitative reconstruction interleaved-pulse acquisition. Pulse widths are selected from measured transfer curves and peak shapes. On thermal SiO2, a tuned (6, 35) ns pair achieves the same per-layer precision as short-pulse acquisition with a 13-fold reduction in the number of analysis frames. On 18O-enriched WOx films, interleaving extends the quantifiable range at the low-fraction end by about 14-fold. Across isotope ratios spanning approximately 1:500 to 1:1, the interleaved reconstruction agrees with the corresponding linear reference measurements, showing no measurable bias introduced by interleaving, and natural-abundance ratios of oxygen, strontium and titanium are reproduced within several percent. The method requires no hardware additions and enables depth-resolved isotope-ratio measurements over a wide range within a single crater.

发表机构

• Center for Nanophase Materials Sciences, Oak Ridge National Laboratory（橡树岭国家实验室纳米材料科学中心）

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