Metallic transport in a monatomic layer of in on a silicon surface.

Department of Physics, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Physical Review Letters (Impact Factor: 7.73). 03/2011; 106(11):116802. DOI: 10.1103/PhysRevLett.106.116802
Source: PubMed

ABSTRACT We have succeeded in detecting metallic transport in a monatomic layer of In on an Si(111) surface, Si(111)-sqrt[7]×sqrt[3]-In surface reconstruction, using the micro-four-point probe method. The In layer exhibited conductivity higher than the minimum metallic conductivity (the Ioffe-Regel criterion) and kept the metallic temperature dependence of resistivity down to 10 K. This is the first example of a monatomic layer, with the exception of graphene, showing metallic transport without carrier localization at cryogenic temperatures. By introducing defects on this surface, a metal-insulator transition occurred due to Anderson localization, showing hopping conduction.

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    ABSTRACT: The temperature dependence of anisotropic conductivity of a quasi-one-dimensional metallic surface, Si(111)4 × 1-In, was measured by a variable-temperature four-tip scanning tunneling microscope. Using the square four-point probe method, we succeeded in measuring the conductivity parallel and perpendicular to the In chains independently as a function of temperature. It was shown that the conductivity perpendicular to the In chains was mainly the conductivity of the space-charge layer of the substrate. Moreover, it was clarified that it strongly depends on the substrate flashing temperature and this sometimes hindered the anisotropic conductivity at low temperatures. In contrast, the conductivity parallel to In chains was clearly dominated by the surface states and decreased drastically around 110 K by the well-known 4×1 to 8×2 metal-insulator transition. The low temperature 8×2 phase had an energy gap as large as ∼250 meV, consistent with previous photoemission reports.
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    Nanoscale Research Letters 04/2013; 8(1):167. · 2.52 Impact Factor

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