Interfacial slippage of helium films on 2D mesoporous hectorite

We measured by 10 MHz ultrasound the interfacial slippage of He-3 and He-4 films on a vibrating substrate of a two-dimensional mesoporous hectorite. I t was found that the interfacial slippage shows a qualitative difference be tween the monolayer and bilayer films, irrespective of the adsorbate. The m onolayer films slipped and underwent decoupling from this substrate at low temperatures. In the bilayer films, in contrast, the first layer of the fil ms was locked on the substrate by the second layer promotion. (C) 2000 Else vier Science B.V. All rights reserved.