4D-scanning transmission electron microscopy (4D-STEM) can be used to measure electric fields such as atomic fields or polarization-induced electric fields in crystal heterostructures. The paper focuses on effects occurring in 4D-STEM at interfaces, where two model systems are used: an AlN/GaN nanowire superlattice as well as a GaN/vacuum interface. Two different methods are applied: First, we employ the centre-of mass (COM) technique which uses the average momentum transfer evaluated from the intensity distribution in the diffraction pattern. Second, we measure the shift of the undiffracted disc (disc-detection method) in nano-beam electron diffraction (NBED). Both methods are applied to experimental and simulated 4D-STEM data sets. We find for both techniques distinct variations in the momentum transfer at interfaces between materials: In both model systems, peaks occur at the interfaces and we investigate possible sources and routes of interpretation. In case of the AlN/GaN superlattice, the COM and disc-detection methods are used to measure internal polarization-induced electric fields and we observed a reduction of the measured fields with increasing specimen thickness.

4D 扫描透射电子显微镜 (4D-STEM) 可用于测量电场，例如晶体异质结构中的原子场或极化诱导电场。本文重点介绍了 4D-STEM 在界面处发生的效应，其中使用了两个模型系统：AlN/GaN 纳米线超晶格以及 GaN/真空界面。应用了两种不同的方法：首先，我们采用质心 (COM) 技术，该技术使用从衍射图案中的强度分布评估的平均动量转移。其次，我们测量非衍射盘的位移（disc-detection方法）在纳米束电子衍射（NBED）。这两种方法都适用于实验和模拟 4D-STEM 数据集。我们发现两种技术在材料之间界面处的动量传递中都有明显的变化：在两种模型系统中，界面处都出现峰值，我们研究了可能的解释来源和途径。在 AlN/GaN 超晶格的情况下，COM 和圆盘检测方法用于测量内部极化引起的电场，我们观察到随着样品厚度的增加，测量的场减少。