Department of Materials, Oxford University, Parks Road, Oxford OX1 3PH, UK.
Ultramicroscopy. 2013 Oct;133:109-19. doi: 10.1016/j.ultramic.2013.07.002. Epub 2013 Jul 15.
The physical basis for using a probe-position integrated cross section (PICS) for a single column of atoms as an effective way to compare simulation and experiment in high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) is described, and the use of PICS in order to make quantitative use of image intensities is evaluated. It is based upon the calibration of the detector and the measurement of scattered intensities. Due to the predominantly incoherent nature of HAADF STEM, it is found to be robust to parameters that affect probe size and shape such as defocus and source coherence. The main imaging parameter dependencies are on detector angle and accelerating voltage, which are well known. The robustness to variation in other parameters allows for a quantitative comparison of experimental data and simulation without the need to fit parameters. By demonstrating the application of the PICS to the chemical identification of single atoms in a heterogeneous catalyst and in thin, layered-materials, we explore some of the experimental considerations when using this approach.
描述了将探针位置积分截面（PICS）用于单个原子列作为比较高角度环形暗场（HAADF）扫描透射电子显微镜（STEM）中模拟和实验的有效方法的物理基础，并评估了使用 PICS 进行定量图像强度的使用。它基于探测器的校准和散射强度的测量。由于 HAADF STEM 的主要非相干性质，它对影响探针大小和形状的参数（例如散焦和源相干性）具有鲁棒性。主要成像参数依赖于探测器角度和加速电压，这些都是众所周知的。对其他参数变化的鲁棒性允许对实验数据和模拟进行定量比较，而无需拟合参数。通过将 PICS 应用于异质催化剂和薄层状材料中单原子的化学鉴定，我们探讨了使用这种方法时的一些实验注意事项。
