Four-point probe measurements using current probes with voltage feedback to measure electric potentials

摘要

We present a four-point probe resistance measurement technique which usesfour equivalent current measuring units, resulting in minimal hardwarerequirements and corresponding sources of noise. Local sample potentials aremeasured by a software feedback loop which adjusts the corresponding tipvoltage such that no current flows to the sample. The resulting tip voltage isthen equivalent to the sample potential at the tip position. We implement thismeasurement method into a multi-tip scanning tunneling microscope setup suchthat potentials can also be measured in tunneling contact, allowing inprinciple truly non-invasive four-probe measurements. The resulting measurementcapabilities are demonstrated for BiSbTe$_3$ and Si$(111)-(7\times7)$ samples.