We performed four-terminal conductivity measurements on a CoSi2 nanowire (NW) at room temperature by using PtIr-coated carbon nanotube (CNT) tips in a four-tip scanning tunneling microscope. The physical stability and high aspect ratio of the CNT tips made it possible to reduce the probe spacing down to ca. 30 nm. The probe-spacing dependence of resistance showed diffusive transport even at 30 nm and no current leakage to the Si substrate.
We have performed in situ resistance measurements for individual epitaxial CoSi 2 nanowires ͑NWs͒ ͑approximately 60 nm wide and 5 m long͒ formed on a Si͑110͒ surface. Two-and four-point probe measurements were done with a multitip scanning tunneling microscope at room temperature. The NWs were well isolated from the substrate by a Schottky barrier with zero-bias resistance of 10 7 ⍀. The resistivity of the NWs was 30 ⍀ cm, which is similar to that for high-quality epitaxial films. The NW resistance was essentially unchanged after exposure to air.
The sheet conductivity of a Au-covered Si͑557͒ facet surface was measured by microscopic four-point probe methods using an independently driven four-tip scanning tunneling microscope and temperature-variable monolithic probes. This surface is composed of a periodic array of Au chains and known to have a quasi-onedimensional metallic band structure. Its surface conductivities parallel to the Au chains ͑ ʈ ͒ and perpendicular to them ͑ Ќ ͒, were obtained separately at room temperature (RT), and the anisotropy ʈ / Ќ was ϳ3. The temperature dependence of the surface conductivity showed a semiconductive character below RT with an activation energy of ϳ55 meV. Then it can be concluded that the transport along the Au chains is not metallic band conduction.
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