Regensburg 2002 – wissenschaftliches Programm
TT 22: Postersitzung III: Syst. korr. Elektr.: Theorie II (1-15), Metall-Isol.- und Phasenüberg
änge (16-33), SL: Massivmat., Bandl., Pinning, Vortexdyn., Transport, Korngr. (34-43), Niedrigdim. Syst., Magnetotransport (44-63)
TT 22.58: Poster
Donnerstag, 14. März 2002, 14:00–17:30, A
DC Measurements of Confined Electrons on Liquid Helium Films — •Irena Doicescu, Jürgen Klier, and Paul Leiderer — Universität Konstanz, Fachbereich Physik, Fach M676, 78457 Konstanz
Electrons dispersed above a superfluid helium complete a plane capacitor due to the dielectric fluid and the underlying substrate. They built up a horizontal layer of charges which can freely move. This pure two-dimensional (2D) system allows experiments like in semiconductors, e.g., transport phenomena, however, studied under conditions of little scattering on impurities. If the substrate covered by the helium forms an arrangement of in-plane electrodes held at ascending potentials, the electrons move along the x-direction above the helium film. With our configuration of source, split-gate, and drain electrode a 2D charge transport is realized and directly measured by an additional pick-up electrode. The lateral confinement, by increasing the negative gate voltage, leads to a quasi one-dimensional charge transport. The electron transport, however, when using only a thin helium film above the solid substrate is usually strongly influenced by scattering of the substrate roughness. To avoid this problem we use a gate-channel smaller than the capillary length of the liquid helium. Along this suspended film the transport mainly depends on the gate-voltage and on the gradient between source and drain, i.e. the two charge reservoirs. The knowledge of the electron density is indispensable for the interpretation of the IV-characteristics measured so far. For this purpose we use a circular configuration of source- and guard-electrodes and compare the leak currents for both various helium film thicknesses and for a hydrogen film condensed on the substrate.