Liquid-vapour phase transitions at interfaces: sub-nanosecond investigations by monitoring the ejection of thin liquid films

The phase-transition dynamics of isopropanol (C3H8O) films with thicknesses on the order of 100 nm deposited on silicon wafers are investigated. A Nd : YAG nanosecond laser pulse is used to heat the substrate. Due to heat transfer, the fluid adjacent to the interface evaporates and the film on top is ejected as an intact liquid layer. The phase transition and the ejection process are monitored by reflectometry with a temporal resolution of about 200 ps and a spatial sensitivity on the nanometre-scale in the direction perpendicular to the substrate. We demonstrate that this approach allows us to determine the generated pressures, the achievable superheating and the relevant timescales of the process and as a consequence provides insights in the nature of the very early stages of the phase transition