Low Temperature Physics: 38, 915 (2012); https://doi.org/10.1063/1.4758766 (7 pages)
Fizika Nizkikh Temperatur: Volume 38, Number 10 (October 2012), p. 1158-1166 ( to contents , go back )
Transport properties of surface electrons over structurized substrate
A.V. Smorodin, V.A. Nikolaenko, S.S. Sokolov
B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine, 47 Lenin Ave., Kharkov 61103, Ukraine
L.A. Karachevtseva, and O.O. Lytvynenko
V. Ye. Lashkaryov Institute of Semiconductor Physics of NAS of Ukraine , 41,pr. Nauki, Kyiv, 03028, Ukraine
Received May 15, 2012
A zero-dimensional electronic system is proposed and realized above superfluid helium in cylindrical macropores of a structurized silicon substrate that passes to a dielectric state at helium temperatures. It is shown that in the presence of holding electric field the depth of potential well for an electron above the spherical concave helium surface substantially depends on the curvature radius of liquid surface, that allows to vary the system parameters within wide range. Conductivity of superficial electrons is measured above the structurized substrate. The experiments are carried out in the temperature range T = 0.5 – 1.6 K for electron densities from 2.6·106 to 108 см–2 at holding electric fields up to 103 V/cm. It is found that the character of charge transport above helium strongly depends on both the carrier concentration and the curvature radius of liquid, filling the substrate macropores. At a large radius of curvature and, accordingly, at a relatively large thickness of helium film on the substrate, the electron conductivity at low temperature is thermoactivated. With reducing of the liquid curvature radius the temperature dependence of conductivity weakens and, at some values of radius, a local “failure” (“dip”-effect) appears in the dependence of conductivity on holding potential. For small curvature radia of helium surface the temperature dependence of electron becomes poor and the “dip”-effect is not observed. An interpretation of the observed dependences is proposed, which is based on the assumption that there appear localized electron states about the macropores.
PACS: 73.20.–r Electron states at surfaces and interfaces;
Key words: superfluid helium, structurized silicon substrate, transport properties.