Crouzier Loïc, Delvallée Alexandra, Devoille Laurent, Artous Sébastien, Saint-Antonin François, Feltin Nicolas
Laboratoire national de métrologie et d'essais (LNE), 29 avenue Roger Hennequin, 78197 Trappes Cedex, France.
Laboratoire national de métrologie et d'essais (LNE), 29 avenue Roger Hennequin, 78197 Trappes Cedex, France.
Ultramicroscopy. 2021 Jul;226:113300. doi: 10.1016/j.ultramic.2021.113300. Epub 2021 May 4.
Scanning Electron Microscopy (SEM) technique is widely used to characterize nanoparticle (NP) size. The landing energy (LE) of the primary electron beam is considered to be a key parameter related to the ability of electrons to penetrate the sample. However, few studies have been carried out so far on the influence of this parameter on the measurement of NP size by SEM. The increasing needs for reference materials consisting of size-controlled NP suspension for microscope calibration induce new issues. This paper focuses on the effect of electron landing energy on the measurement of the equivalent diameter of several NP populations by SEM. To evaluate the influence of LE, particles of different sizes and chemical compositions were analyzed. The results showed the variation of the measured diameter as a function of LE. SEM secondary electron (SE) yield modeling by the Monte Carlo method allowed us to relate this variation to the information volume in the material. Finally, the use of reference particles and transmission electron microscopy (TEM) allowed us to determine an optimal value of LE to be applied, depending on the chemical composition and particle size to limit the bias in the SEM measurement. We showed that this operating point can be simply determined without reference nanomaterials by scanning an LE range.
扫描电子显微镜（SEM）技术被广泛用于表征纳米颗粒（NP）的尺寸。一次电子束的着陆能量（LE）被认为是与电子穿透样品能力相关的关键参数。然而，到目前为止，关于该参数对通过SEM测量NP尺寸的影响的研究很少。对用于显微镜校准的由尺寸可控的NP悬浮液组成的参考材料的需求不断增加引发了新问题。本文重点研究电子着陆能量对通过SEM测量几种NP群体等效直径的影响。为了评估LE的影响，分析了不同尺寸和化学成分的颗粒。结果显示了测量直径随LE的变化。通过蒙特卡罗方法对SEM二次电子（SE）产率进行建模，使我们能够将这种变化与材料中的信息体积联系起来。最后，使用参考颗粒和透射电子显微镜（TEM）使我们能够根据化学成分和颗粒尺寸确定要应用的LE的最佳值，以限制SEM测量中的偏差。我们表明，通过扫描LE范围，可以在不使用参考纳米材料的情况下简单地确定该操作点。
