Walking a silicon atom through a graphene landscape

The electron beam in a transmission electron microscope (TEM) can displace atoms in a sample and sometimes cause what’s called knock-on damage.Researchers at the University of Vienna, together with UK teams at the Daresbury SuperSTEM Laboratory and the University of Manchester and a team from Nion Co in the US, have now used those displacements to manipulate a sample one atom at a time. During TEM scans of silicon-doped graphene, they found that the electron beam can cause a Si atom to hop from one lattice site to a neighboring one about 0.14 nm away. The two TEM images here, taken 0.5 seconds apart, show a Si atom (bright spot) before and after such a hop. The hop itself happens on a time scale too fast to see with a TEM, so the researchers turned to molecular dynamics simulations, which showed that the electron beam actually knocks out a carbon...