Relations between electron yield and temperature rise under low-energy electron irradiation for Au element.

Scanning electron microscope (SEM) is a widely used tool for analysing the micro/nanoscale structural information. In the process of the SEM imaging, the temperature rise caused by the electron beam bombardment has already become an issue because the SEM results might thus be modified by it as the specimen downsizes. This work aims to explore the relationship between the total electron yield (TEY) and the temperature rise in order to directly evaluate the heat accumulation inside the solid during the imaging using a Monte Carlo (MC) simulation. The rules of profiles of the TEY and the temperature rise integral with various primary electron (PE) beam energies and incident angles were first investigated focusing on a semi-infinite gold (Au) bulk. Based on this rule, it is concluded that, with the increase of the TEY, the temperature rise integral decreases almost linearly (As the PE energy getting larger, the linear correlation is more obvious). In addition, this result was also applied to evaluate the heat built up for two specific SEM imaging examples: nanoscale Au balls and arbitrary shaped Au particles on a carbon (C) substrate. Their temperature contour maps present an almost inverse contrast compared with their respective SEM images. Furthermore, the influence of external electric field (full extraction and no extraction modes) for thermal effect was discussed. It is concluded that the full extraction mode can effectively avoid the local overheating. The mechanism of these observations was explained in detail. On the one hand, this work gives a better elucidation and understanding for physical mechanism of electron-beam-induced deposition, of which reliability, process control and performance can thus be greatly improved. On the other hand, because some damages caused by nonuniform heat accumulation in various local geometric structures of specimen during imaging process could be effectively analysed and even reduced, this work thus greatly benefits for the analysis of the correlation between thermal effect and the structures of samples.
(© 2020 Royal Microscopical Society.)