Atomic structures for three-fold and four-fold coordinated silicon impurities in monolayer graphene © APSA combination of scanning transmission electron microscopy and atomic-resolution spectroscopic techniques has allowed US researchers to pick out individual silicon atoms in a doped graphene sheet. The technique reveals that the silicon atoms can exist in a planar hybridised ‘sp2d’ like form when bonded to four carbon atoms, as well as the anticipated sp3 form when triply coordinated. The experimental observations mesh with simulations of two-dimensional solids and point the way to a method for exploring single impurities in graphene and related materials.Stephen Pennycook and colleagues at...