Design and Performance of a Miniaturized, Low-Energy, Large Beam Spot Electron Flood Gun

Charge accumulation often occurs in electron optics equipment and interferes with their operation. The trouble can be handled by using the electron flood gun. However, there are still some scenarios where neutralization is not as desired. To achieve a better charge neutralization effect and to facilitate work in confined spaces, a small size, low-energy electron flood gun providing a large area and uniform electron beam has been required. This article employs Munro’s Electron Beam Software (MEBS) to simulate the effect of the structure parameters on the performance of the beam. Based on the simulation results, the electron flood gun is processed and assembled. To verify the performance of the electron flood gun, this paper proposes a new “pinhole scanning method”. By using the method, we have achieved in-situ measurements of beam current and beam spot. The experimental results generally match the simulation results, which demonstrates that the electron flood gun has good performance and is likely to have many applications.

Imaging simulation of charged nanowires in TEM with large defocus distance

In transmission electron microscope (TEM), both the amplitude and the phase of electron beam change when electrons traverse a specimen. The amplitude is easily obtained by the square root of the intensity of a TEM image, while the phase affects defocused images. In order to obtain the phase map and verify the theoretical model of the interaction between electron beam and specimen, a lot of simulations have to be performed by researchers. In this work, we have simulated defocus images of a SiC nanowire in TEM with the method of electron optics. Mean inner potential and charge distribution on the nanowire have been considered in the simulation. Besides, due to electron scattering, coherence loss of the electron beam has been introduced. A dynamic process with Bayesian optimization was used in the simulation. With the infocus image as input and by adjusting fitting parameters, the defocus image is determined with a reasonable charge distribution. The calculated defocus images are in a good agreement with the experimental ones. Here, we present a complete solution and verification method for solving nanoscale charge distribution in TEM.