Considerable knock-on displacement of metal atoms under a low energy electron beam

Abstract

Under electron beam irradiation, knock-on atomic displacement is commonly thought to occur only when the incident electron energy is above the incident-energy threshold of the material in question. However, we report that when exposed to intense electrons at room temperature at a low incident energy of 30 keV, which is far below the theoretically predicted incident-energy threshold of zirconium, Zircaloy-4 (Zr-1.50Sn-0.25Fe-0.15Cr (wt.%)) surfaces can undergo considerable displacement damage. We demonstrate that electron beam irradiation of the bulk Zircaloy-4 surface resulted in a striking radiation effect that nanoscale precipitates within the surface layer gradually emerged and became clearly visible with increasing the irradiation time. Our transmission electron microscope (TEM) observations further reveal that electron beam irradiation of the thin-film Zircaly-4 surface caused the sputtering of surface α-Zr atoms, the nanoscale atomic restructuring in the α-Zr matrix, and the amorphization of precipitates. These results are the first direct evidences suggesting that displacement of metal atoms can be induced by a low incident electron energy below threshold. The presented way to irradiate may be extended to other materials aiming at producing appealing properties for applications in fields of nanotechnology, surface technology, and others.

Modifications of Polymeric Membranes Used in Guided Tissue and Bone Regeneration

“…Electron beam irradiation is a method in which linearly accelerated electrons interact with a surface, thus causing its damage [52,53]. The study conducted by Bilgi et al reported the use of bacterial cellulose non-resorbable membrane irradiated at 100 or 300 kGy in GBR.…”

Distributing the Electron Dose to Minimise Electron Beam Damage in Scanning Transmission Electron Microscopy

“…What does change is the spacing between probe positions in the raster scan, which decreases with increasing magnification, eventually getting to the situation where the electron beam and/or damage species diffusion profiles overlap ( Figure 1)this is the case for most high-resolution STEM image acquisitions. Simulations that compare raster, random, and line hop scanning during image acquisition in a homogenous film have been performed using the concept of beam influence -the electron beam imparts energy onto the sample, and it is the accumulation of this imparted energy which causes beam induced phenomena; such as radiolysis 3 , knock-on 4 , etc. By modelling the beam influence, these simulations can explain how increasing the magnification (reducing the step separation) causes a local increase in the maximum beam influence under the beam during raster scanning.…”

Electron irradiation effects on Ag nanoparticles

“…In this respect, electron irradiation experiments are particularly interesting. In contrast to very large electron fluxes effects associated with melting [25] or with multiple electron collisions [26], the irradiation parameters (energy and flux) can be fine-tuned to produce single atom displacements uncorrelated in time and space, meaning that lattice relaxation occurs in a smaller time interval than the average time between two consecutive electron impacts on the same NP. Nevertheless, the achieved atomic displacement rates produced by electron-atom elastic collisions can enhance atomic migration and therefore promote microstructural changes.…”