Competitive Stability of W@Si 15 and W@Si 16 Superatoms: Oxidative Reactivity and Electrical Conductivity

Gas-phase synthesized superatoms (SAs) consisting of a tungsten-atom-encapsulating silicon cage, W@Sin, were size-selectively deposited on substrates through soft landing, and their oxidative stability and electrical conductivity were evaluated. The size-dependent reactivity of W@Sin (n = 12-17) on C60 substrates toward O2 exposure was measured by X-ray photoelectron spectroscopy, while variable-temperature electrical measurements were conducted for the assembled films of W@Si15 and W@Si16. Both W@Si15 and W@Si16 on C60 exhibit enhanced oxidative resistance compared with neighboring sizes, and the assembled W@Si15 films show higher electrical conductivity than that of W@Si16. Theoretical calculations further indicate that W@Si15 retains a nearly spherical Si cage across charge states, whereas W@Si16 adopts a distorted structure with one protruding Si atom. This study reveals that SAs with high symmetric geometric structure are advantageous for achieving superior chemical stability and electrical conductivity in their assembled states.