Berlin 2008 – scientific programme
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O: Fachverband Oberflächenphysik
O 94: Methods: Other Experimental Techniques II
O 94.3: Talk
Friday, February 29, 2008, 12:30–12:45, MA 141
The mono-cantilever method of performing multi-contact measurements of surface conductivity — •Justin Wells1, Karsten Hardrup1, Fei Song1,2, Jesper Kallehauge1, Lauge Gammelgaard3, Shi ning Bao2, and Philip Hofmann1 — 1ISA and iNano, University of Aarhus, 8000 Aarhus C, Denmark — 2Department of Physics, Zhejiang University, P.R. China — 3MIC, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
Despite the paramount importance of conductance measurements to bulk solid state physics, surface conductance is very poorly understood. A prominent example for the sorry state of the field is the Si(111)(7×7) reconstruction. Several claims to measure the surface conductance have been made but these span 5 orders of magnitude.
In this work, we present a multi-contact mono-cantilever probe, which differs from earlier monolithic 4-point probes by that fact that all contacts are mounted on a single cantilever. In this approach, the minimum spacing can be reduced to the order of 250 nm, whilst keeping the cantilever size in the micrometer range (and thus it is strong and easily visible).
As an example, we will present measurements made on Bi(111). In contrast to the semimetallic bulk, this surfaces support metallic surface states, forming a quasi two-dimensional metal. Using measurements with different probe spacings, we are able to estimate an upper limit of the conductance through these surface states.