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.