Measuring the Thickness of the Liquid-like Layer on Ice Surfaces with Atomic Force Microscopy

Atomic force microscopy was used to study the surface melting of ice in a temperature range above −35 °C. The thickness of the liquid-like layer (d) on ice was determined from the jump-in distance of force-versus-distance curves. The layer thickness of ice formed from distilled water was roughly 32 nm at −1 °C and 11 nm at −10 °C. The temperature dependence of d could best be described by d ∝ −log ΔT, where ΔT is the difference between the melting temperature and the actual temperature. The addition of salt increased the thickness of the liquid-like layer, and the temperature dependency agreed with predictions by Wettlaufer (Phys. Rev. Lett. 1999, 82, 2516).