We present measurements of the electron phase coherence time tau(varphi) on a wide range of open ballistic quantum dots (QDs) made from InGaAs heterostructures. The observed saturation of tau(varphi) below temperatures 0.5 K

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We present here the synthesis and structural characterization of hybrid Au-polypyrrole-Au and Ptpolypyrrole-Au nanowires together with a study of their electrical properties from room-temperature down to very low temperature. A careful characterization of the metal-polymer interfaces by transmission electron microscopy revealed that the structure and mechanical strength of bottom and upper interfaces are very different. Variable temperature electrical transport measurements were performed on both multiple nanowires -contained within the polycarbonate template -and single nanowires. Our data show that the three-dimensional Mott variable-range-hopping model provides a complete framework for the understanding of transport in PPy nanowires, including non-linear current-voltage characteristics and magnetotransport at low temperatures. † Research associate of the FNRS. ometry of the devices. Despite these experimental efforts, the electrical transport at nanoscale in conjugated polymers is still matter of debate. Until now, very few studies [4,9] focused on the synthesis and electrical characterization of hybrid conjugated polymer-metal nanowires. Moreover, none of them reported on the structural characterization of the metal-polymer interfaces, which could play an important role on the electrical properties of the nanodevices. We present here the synthesis and structural characterization of hybrid metal(Au or Pt)-polypyrrole(PPy)-metal(Au) nanowires together with a study of their electrical properties from roomtemperature down to very low temperature (T ≈ 0.5 K). Metallic segments, few microns long, serving as contacting electrodes are electrochemically synthetized within polycarbonate (PC) templates, before and after the PPy nanowire growth. Interestingly, the resulting metal-PPymetal hybrid nanowires have two morphologically different PPy-metal interfaces (see Fig. 1). In terms of mechanical robustness the PPy-onto-metal interface is smoother and more fragile than the metal-onto-PPy interface. By using Pt instead of Au for the first grown segment, much more robust nanowires have been fabricated. The present all-electrochemical technique allows controlled optimization of the mechanical strength arXiv:1112.4656v1 [cond-mat.mes-hall]

We present an experimental comparison of magnetoconductance fluctuations measured in the ballistic, quasiballistic, and diffusive scattering regimes of semiconductor devices. In contradiction to expectations, we show that the spectral content of the magnetoconductance fluctuations exhibits an identical fractal behavior for these scattering regimes and that this behavior is remarkably insensitive to device boundary properties. We propose a unified model of fractal conductance fluctuations in the ballistic, quasiballistic, and diffusive transport regimes, in which the generic fractal behavior is generated by a subtle interplay between boundary and material-induced chaotic scattering events.