Thermal effect of two adjacent nanospheres during electron irradiation

Abstract

Along with the characteristic size continuously reducing, the impact of the thermal effect on the accurate size assessment of nanoscale devices by the scanning electron microscopy (SEM) technique is increasingly apparent. Various thermal phenomena may occur in different structures of samples under the electron irradiation. To explore the fundamental rule behind this issue, this study used a Monte Carlo (MC) simulation approach to mainly obtain a series of spatial distributions of the temperature rise in two adjacent gold (Au) nanoparticles (Au nanosphere (Au-NS)) with different sizes. Study on the influences of the detection mode, primary electron (PE) energy, the angle of incidence and the size of the PE beam on the thermal effect were carried out systematically. This paper concluded that Au-NSs with different sizes exhibit various heat capacities with PE energy. The smaller the size of an Au-NS, the less heat it accumulates. The detection mode plays an important role in heat generation. Simply put, the overall heat generated in the no extraction mode is larger than that generated in the full extraction mode. This study next examined that, as the incident angle increases, the temperature rise distribution area spreads gradually from the contact region to the inside and its intensity decreases with the PE beam size. Finally, the thermal effect in a system of multi-Au-NSs (a good extrapolation to actual powder samples) was also discussed. Based on the analysis of the electron trajectory and the electron-solid interaction, the underlying mechanism of these results was explained in detail. Compared with earlier reports that just studied on the thermal issue under the case of the PE beam being kept in a fixed incident area for infinite bulks, this work focuses on a whole SEM imaging process, wherein the thermal issue would shed a more substantial light. It is beneficial to develop the relations between the local thermal issue and the structure of samples, which is believed to greatly promote the development of the semiconductor industry.