9402647 Dahm Technical abstract: The properties of electrons in two dimensions will be investigated using semiconductor heterostructures and electrons on helium films. Studies will be carried out in the variable-range hopping regime in gated heterostructures. A search will be made for a predicted Coulomb gap in the density of states. The magnetic field dependence of the localization length will be studied in an attempt to measure the energy of the "floating" delocalization states. The conduction properties of a pinned electron crystal on a liquid helium film will be carried out. This is a model sliding charge-density wave with a coupling to "impurities" (substrate potentials) which can be varied through a wide range by changing the film thickness. Non-technical abstract: The aim of this study is to achieve a better understanding of the laws of physics governing two- dimensional systems. The investigations span the spectrum of interest from a classical system of electrons on a helium surface to the quantum limit of electrons in semiconductors. The study of two-dimensional electrons in semiconductors is closely related to the 2D Hall effect and results from this study may have applications to electronic devices. Electrons on a helium surface form a model system to study properties of phenomena which occur in three dimensions within a more limited set of variables. ***
