Edge melting in two-dimensional solid films

The one-dimensional analog of surface melting is observed in adsorbed monolayer films. Evidence of ‘‘edge melting’’ is obtained by high-resolution calorimetry of neon monolayers adsorbed on graphite, which displays a precursor of first-order melting at the two-dimensional triple point. The precursor begins about 1 K below $T_t$, then increases according to the temperature dependence ΔC=const×($T_t$-T${)}^{\mathrm{-}r}$. The power law is consistent with the mean-field theory of surface melting of two-dimensional solids governed by dispersion forces. An extensive analysis of finite-size effects and substrate binding-energy variations permits a detailed interpretation of the specific-heat peak shapes. Previous experiments and computer simulations are quantitatively consistent with the present results.