The intercalation of Ar into C₆₀ films

In this Communication we discuss how unimplanted and implanted films (Y and Au implanted) of C₆₀, when hot isostatically pressed (HIPed) at a pressure of 170 MPa (1.7 kbar) of Ar and temperatures of 300 or 400 °C, show substantial uptake of Ar into the film. Rutherford backscattering (RBS) provides an effective method for elucidating film composition, showing the films to have ∼1.5 at.% of Ar, consistent with a stoichiometry close to Ar₁ C₆₀. The Ar was found to diffuse from the films when these were held in a vacuum at 300 °C. It could subsequently be reincorporated into the film by re-HIPing, with uptake of a similar amount of Ar. IR spectroscopy showed that the C₆₀ IR absorptions remain unchanged throughout uptake of the Ar and its subsequent loss during heating at 300 °C. It appears that the Ar is trapped interstitially in the films outside the C₆₀ cages.