Coakley Kevin J, Sanford Norman A
National Institute of Standards and Technology, 325 Broadway, Boulder CO 80305, USA.
Ultramicroscopy. 2022 Jul;237:113521. doi: 10.1016/j.ultramic.2022.113521. Epub 2022 Apr 2.
In laser-assisted atom probe tomography, an important goal is to reconstruct the mass-to-charge ratio, (m/z), spectrum due to various ion species. In general, the probability mass function (pmf) associated with the time-of-flight (TOF) spectrum produced by each ion species is unknown and varies from species-to-species. Moreover, measuring pmfs for distinct ion species in calibration experiments is not practical. Here, we present a mixture model method to determine TOF pmfs that can vary from peak-to-peak. In this approach, we determine weights of candidate pmfs with a maximum likelihood method. In a proof-of-principle study, we apply our method to a TOF spectrum acquired from a silicon sample and determine intensity estimates of singly charged isotopes of silicon.
在激光辅助原子探针层析成像中，一个重要目标是重建由于各种离子种类产生的质荷比（m/z）谱。一般来说，与每种离子种类产生的飞行时间（TOF）谱相关的概率质量函数（pmf）是未知的，并且因离子种类而异。此外，在校准实验中测量不同离子种类的pmf并不实际。在此，我们提出一种混合模型方法来确定可能逐峰变化的TOF pmf。在这种方法中，我们用最大似然法确定候选pmf的权重。在一项原理验证研究中，我们将我们的方法应用于从硅样品获取的TOF谱，并确定硅的单电荷同位素的强度估计值。
