Superheating of small solid-argon bubbles in aluminum

Small solid-Ar bubbles, formed by the implantation of 50-keV ${\mathrm{Ar}}^{+}$ ions into Al, are observed to melt at 730 K, compared with an equilibrium bulk melting temperature of 250 K. A model based on the suppression of Ar thermal vibrations at the Al interface is used to account for the superheating of 480 K. Measurements on the temperature dependence of diffracted electron intensities from these bubbles yield Debye-Waller factors consistent with an effective Debye temperature of about 140 K, compared with a bulk value of 110 K.