Quantum transport in ultrathin CoSi2 polycrystalline films

Quantum transport in ultrathin CoSi2 polycrystalline films was studied for the first time. The temperature corrections to the conductivity of these films and their anomalous magnetoresistance have been observed and investigated. It is shown that they are determined by the effects of interaction and weak localization with the strong spin-orbit and spin scattering taken into account. Unlike the epitaxial crystalline films reported previously our films including one with the thickness larger than 10 nm show no superconductivity down to the lowest temperature (0.2 K). In the thinnest film we used an unusual dimensional crossover from one dimensional behavior of quantum corrections to two dimensional have been observed with lowering temperature, supposedly due to changes of the characteristic correlation length in the sample, which consisted of meandrous conducting paths caused by the presence of pin-holes. (C) 1997 Published by Elsevier Science Ltd.X11sciescopu

Classical and Quantum Transport in Antidot Arrays

The story of solid state physics is the story of electrons in periodic potentials caused by the periodic arrangement of atoms in crystalline solids. It was early recognized that an additionally imposed periodic potential can significantly modify the solid’s properties [1]. A major breakthrough in this respect was the concept of bandstructure engineering introduced by L. Esaki and R. Tsu [2,3]. The advent of molecular beam epitaxy with the possibility to grow semiconductor crystals atom by atom (see, e.g. [4]) allowed one not only to fabricate such one-dimensional superlattices superimposed upon the three-dimensional crystallographic lattice but also to realize two-dimensional electron systems (2DES) of superior quality [5]. Two-dimensional electron systems offered a wealth of new phenomena and are still the subject of current research. Prominent examples of effects based on the reduction of dimensionality for conduction electrons (or holes), are the quantum Hall effect (QHE) [6] and the fractional quantum Hall effect (FQHE) [7]. New phenomena were also expected for a one- or two-dimensional (2D) periodic potential imposed upon a two-dimensional electron system [8,9]. By using nanolithographic techniques it is possible these days to impress periodic potentials of different strength, period and shape upon high mobility two-dimensional electron systems such that the electron mean free path l e and phase coherence lenght l ø is much longer than the period of the periodic potentials. Two different types of potential landscapes are displayed in Fig. 5.1 showing weak and strong 2D-periodic potentials imposed upon a two-dimensional electron system