当前位置: X-MOL 学术Surf. Interface Anal. › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
High‐resolution peak analysis in TOF SIMS data
Surface and Interface Analysis ( IF 1.7 ) Pub Date : 2020-10-15 , DOI: 10.1002/sia.6872
Lev D. Gelb 1 , Negar Shahrokh Esfahani 2 , Amy V. Walker 1
Affiliation  

High mass resolution time‐of‐flight secondary ion mass spectrometry (TOF SIMS) can provide a wealth of chemical information about a sample, but the analysis of such data is complicated by detector dead‐time effects that lead to systematic shifts in peak shapes, positions, and intensities. We introduce a new maximum‐likelihood analysis that incorporates the detector behavior in the likelihood function, such that a parametric spectrum model can be fit directly to as‐measured data. In numerical testing, this approach is shown to be the most precise and lowest‐bias option when compared with both weighted and unweighted least‐squares fitting of data corrected for dead‐time effects. Unweighted least‐squares analysis is the next best, while weighted least‐squares suffers from significant bias when the number of pulses used is small. We also provide best‐case estimates of the achievable precision in fitting TOF SIMS peak positions and intensities and investigate the biases introduced by ignoring background intensity and by fitting to just the intense part of a peak. We apply the maximum‐likelihood method to fit two experimental data sets: a positive‐ion spectrum from a multilayer MoS2 sample and a positive‐ion spectrum from a TiZrNi bulk metallic glass sample. The precision of extracted isotope masses and relative abundances obtained is close to the best‐case predictions from the numerical simulations despite the use of inexact peak shape functions and other approximations. Implications for instrument calibration, incorporation of prior information about the sample, and extension of this approach to the analysis of imaging data are also discussed.

中文翻译:

TOF SIMS数据中的高分辨率峰分析

高质量的飞行时间二次离子质谱仪(TOF SIMS)可以提供有关样品的大量化学信息,但是由于检测器死区效应会导致峰形的系统变化,这些数据的分析变得很复杂,位置和强度。我们引入了一种新的最大似然分析,该分析将检测器的行为纳入似然函数中,从而可以将参数频谱模型直接拟合至所测数据。在数值测试中,与针对死区影响校正的数据的加权和非加权最小二乘拟合相比,该方法被证明是最精确,偏差最小的方法。次优的是非加权最小二乘法分析,而当使用的脉冲数较小时,加权的最小二乘法会遭受明显的偏差。我们还提供了最合适的TOF SIMS峰位置和强度拟合精度的最佳估计,并通过忽略背景强度或仅拟合峰的强烈部分来研究引入的偏差。我们应用最大似然法来拟合两个实验数据集:多层MoS的正离子光谱2个样品和TiZrNi大块金属玻璃样品的正离子光谱。尽管使用了不精确的峰形函数和其他近似值,但提取的同位素质量和相对丰度的精度仍接近于数值模拟中的最佳情况预测。还讨论了仪器校准,样品的先验信息的结合以及这种方法对成像数据分析的扩展。
更新日期:2020-12-08
down
wechat
bug