More Atomically Thin Materials

By conducting a combined microscopy, spectroscopy, and computational study of one-atom-thick films of silicon, European researchers have gathered what they describe as “compelling experimental evidence” that they have succeeded in preparing the Si analog of graphene (Phys. Rev. Lett., DOI: 10.1103/PhysRev​Lett.108.155501). Dubbed silicene because of its predicted graphenelike structural and electronic properties, the ultrathin 2-D form of silicon is expected to be inherently more compatible with silicon-based electronics than graphene is. A number of research groups have previously claimed to have prepared the material, but those claims were based strictly on scanning tunneling microscope (STM) images, which are often difficult to interpret. Patrick Vogt of Berlin’s Technical University, Paola De Padova of Italy’s National Research Council in Rome, and coworkers, grew atomically thin Si films on silver via vapor deposition. They showed that the bond lengths and angles determined from STM and angle-resolved photoemission data, and the details in micrographs, closely match the results of quantum calculations. In related work, Rice University’s Boris I. Yakobson and coworkers devised a computational method that treats vacancy-riddled one-atom-thick films of boron as alloys of atoms and vacancies. The model predicts that, in contrast to graph­ene, the holey boron family of materials includes many stable structures and phases (Nano Lett., DOI: 10.1021/nl3004754).