Angular and Spatially Resolved Secondary Electron Yield Measurements of Thin Films and Structured Materials

The secondary electron yield (SEY) plays an important role in various research fields and applications, from electron multipliers and vacuum cavities up to spacecrafts. Depending on the application, either a low, high, or a predetermined SEY needs to be achieved. While the SEY depends on the investigated material, it is also influenced by parameters like surface chemistry, roughness, and the incident angle of primary electrons. Thus, knowledge of the SEY is crucial for improving these applications, which entails the need for an SEY measurement setup. Herein, we present a simple but versatile method to equip a commercial scanning electron microscope (SEM) with a detector unit, allowing for SEY measurements on conducting materials but also insulating thin films. A comparison of measured SEY values for oxygen-free copper, Al2O3, and NbTiN to the literature highlights the accuracy of this setup. Furthermore, the feasibility of tilted measurements is demonstrated, enabling the angular-resolved determination of the SEY. Finally, we demonstrate the recording of a 2D SEY map, therefore elucidating and visualizing structural variations. Moreover, this SEY setup configuration allows for a plug-and-play modification of existing SEMs with components that can easily be removed after the measurement, or can be used as part of a freestanding setup to measure the SEY. These advantages could allow more research groups to investigate and measure the SEY to advance their respective field. Furthermore, the presented 2D SEY map could be a starting point for better application-tailored SEY measurements, or for completely new measurement techniques altogether.