Scanning Electron Microscopy (SEM) is considered as a reference technique for the determination of nanoparticle (NP) dimensional properties. Nevertheless, the image analysis is a critical step of SEM measuring process and the initial segmentation phase consisting in determining the contour of each nano-object to be measured must be correctly carried out in order to identify all pixels belonging to it. Several techniques can be applied to extract NP from SEM images and evaluate their diameter like thresholding or watershed. However, due to the lack of reference nanomaterials, few papers deals with the uncertainty associated with these segmentation methods. This article proposes a novel approach to extract the NP boundaries from SEM images using a remarkable point. The method is based on the observation that, by varying the electron beam size, the secondary electron profiles crosses each other at this point. First, a theoretical study has been performed using Monte Carlo simulation on silica NP to evaluate the robustness of the method compared with more conventional segmentation techniques (Active Contour or binarization at Full Width at Half-Maximum, FWHM). The simulation results show especially a systematic discrepancy between the NP real size and the measurements performed with both conventional methods. Moreover, generated errors are NP size-dependent. By contrast, it has been demonstrated that a very good agreement between measured and simulated diameters has been obtained with this new technique. As an example, this method of the remarkable point has been applied on SEM images of silica particles. The quality of the segmentation has been shown on silica reference nanoparticles by measuring the modal equivalent projected area diameter and comparing with calibration certificate. The results show that the NP contour can be very accurately delimited with using this point. The measurement uncertainty has been also reduced from 4.3 nm (k = 2) with conventional methods to 2.6 nm (k = 2) using the remarkable point.

中文翻译：

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使用显着点从一组 SEM 图像测量纳米颗粒直径的 FA 新方法

扫描电子显微镜 (SEM) 被认为是确定纳米颗粒 (NP) 尺寸特性的参考技术。然而，图像分析是 SEM 测量过程的关键步骤，必须正确执行确定每个待测量纳米物体轮廓的初始分割阶段，以识别属于它的所有像素。可以应用几种技术从 SEM 图像中提取 NP 并评估它们的直径，如阈值或分水岭。然而，由于缺乏参考纳米材料，很少有论文涉及与这些分割方法相关的不确定性。本文提出了一种使用显着点从 SEM 图像中提取 NP 边界的新方法。该方法基于观察到，通过改变电子束尺寸，二次电子分布在这一点上相互交叉。首先，使用蒙特卡罗模拟对二氧化硅 NP 进行了一项理论研究，以评估该方法与更传统的分割技术（活动轮廓或半最大值全宽二值化，FWHM）相比的稳健性。模拟结果尤其显示了 NP 实际尺寸与使用两种常规方法进行的测量之间的系统差异。此外，生成的错误与 NP 大小有关。相比之下，已经证明使用这种新技术在测量直径和模拟直径之间获得了非常好的一致性。例如，这种显着点的方法已应用于二氧化硅颗粒的 SEM 图像。通过测量模态等效投影面积直径并与校准证书进行比较，已在二氧化硅参考纳米颗粒上显示了分割的质量。结果表明，使用该点可以非常准确地划定 NP 轮廓。使用显着点，测量不确定度也从传统方法的 4.3 nm (k = 2) 降低到 2.6 nm (k = 2)。