Dresden 2017 – scientific programme

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O: Fachverband Oberflächenphysik

O 32: Focus Session: Charge Transport at Surfaces and Nanostructures with Multi-probe Techniques I

O 32.8: Talk

Tuesday, March 21, 2017, 12:45–13:00, WIL C307

Separating 2D and 3D resistivities using a modified 4-probe method — Snorre Kjeldby, Simon Cooil, and •Justin Wells — Norwegian University of Science and Technology (NTNU), Trondheim, Norway.

4-probe electrical measurements have been in existence for many decades. One of most useful aspects of the 4-probe method is that it is not only possible to find the resistivity of a sample (independently of the contact resistances), but that it is also possible to probe the dimensionality of the sample. In theory, this is straightforward to achieve; by measuring the 4-probe resistance as a function of probe separation. In practice, it is challenging to move all four probes reliable and with sufficient precision over the necessary range. The available instrumentation (usually based on 4 independently driven STM tips) is complex, expensive and often unreliable.

Here, we present an alternative approach. Combining analytical and numerical modelling with scaled experiments, we demonstrate that the dimensionality of the sample resistivity can be directly probed using a modified 4-probe method in which 3 of the probes are kept stationary, and the position of only one probe is changed. This allows 2D and 3D contributions the to resistivity to be easily deconvolved. The required experimental instrumentation is vastly simplified relative to traditional variable spacing 4-probe instruments.