Electrons above helium films on metal substrates

We report about our investigations on two-dimensional electron ensembles floating above thin helium films supported by metallic substrates. We found a surprisingly high stability of these electrons, although the substrates were conducting which allows breakthrough at weak spots of the helium film due to roughness peaks. We have measured the electron densities and corresponding relaxation times. By putting the electrons from the area above the loading electrode to the area above a separate electrode one can enhance the lifetime of these surface state electrons.