Another well-known damage mechanism is atomic displacement or knock-on damage, which can also lead to sputtering.
Now, atomic-sized beams are routine, even at accelerating voltages as low as 40 kV, allowing knock-on damage to be minimized in beam sensitive materials.
Ionization damage increases as the beam energy is reduced, but knock-on damage decreases, until it disappears entirely below a certain threshold.
But in most insulating materials, radiolysis provides a far more efficient damage mechanism; although knock-on damage must occur in organic materials, it is likely to be 103 to 106 times slower than radiolysis [27].
However, unlike the abrupt onset of knock-on damage in bulk materials, this onset is continuous and occurs at much lower energies because of the distribution of reduced binding energies of atoms at surfaces, interfaces, or defects [24, 25].
Using electrons at 80 kV not only minimizes the knock-on damage, but also improves the detection sensitivity due to the higher scattering power of carbon at lower acceleration voltage of the electron.
These threshold values are above the acceleration voltage (200 keV) in the present study, thus which leads us to exclude the possibility that knock-on damage induces the hole drilling and the formation of the new phases (Figs. 1 and 2).
Electron-beam damages in the TEM for inorganic specimens are largely classified into knock-on damage which means atomic displacement by the electron beam through elastic scattering and radiolysis which indicates chemical bond breaking through inelastic scattering (ionization) [16, 25, 26].
We discover exceptionally high rates for irradiation induced SW healing, incompatible with the previously assumed mechanism of direct knock-on damage and indicating the presence of an efficient nonadiabatic coupling healing mechanism involving beam induced electronic excitations of the SW defect.
For example, waterlogging of the soil risks asphyxiating roots through oxygen shortage, with knock-on damage to the shoot systems that depend on them.
In fact, the low energy of the electron beam would not be sufficient to create new vacancies in the bulk lattice (as the threshold for knock-on damage of single carbon atoms in graphene is 86 keV), but it could be enough to displace atoms at graphene edges.
