Church Help Request Letter

Less is more when measuring weak atomic bonds

If you want to see single atoms, it helps to have a powerful microscope. But in difficult situations as an atom at the edge of a sheet of carbon atoms, a high energy beam can disrupt the bonds that hold atoms of this type, making it difficult to study. Now for the first time, a low energy beam was used to having these bonds.

In the past, the beams of high energy electrons have been used to investigate the individual atoms. For example, as an electron beam is used to identify individual atoms-called "rare earth" elements were trapped inside buckyballs, round cage made of carbon atoms. By observing the energy spectra of electrons recovered, researchers can infer the size of the inside of the atom, and thus identify it.

probe atoms in other situations, however, may require more sensitive methods. Masanori Koshino, Kazu Suenaga and the National Institute of Advanced Industrial Science and Technology in Tsukuba, Japan, wanted to make measurements on carbon atoms cling to the edge of a sample of graphene - a sheet of carbon atoms arranged in a hexagonal grid. In particular, became interested in the number of bonds holding the atoms of the edge in place, as this can affect the electrical and chemical properties of the graphene sheet.

In principle, the energy spectra of electrons scattered by an atom edge can be used to count the bonds. The problem is that a high electron beam energy can also reorder the edge atoms, changing the property itself to be measured.

Suenaga Koshino and took advantage of a new electron microscope that was able to accurately resolve the spectra of scattered electrons, even if they were of relatively low energy. Using electron beam with about 40 percent less energy than previous studies, the couple was able to resolve the spectra of electrons scattered by different atoms of graphene edge before the interruption occurred bond.