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

TL;DR

This paper introduces a four-point probe measurement method using current probes with voltage feedback, enabling minimal hardware noise and non-invasive potential measurements in scanning tunneling microscopes.

Contribution

The authors develop a software-controlled four-point probe technique that simplifies hardware and allows non-invasive potential measurements in tunneling contact.

Findings

Effective measurement of sample potentials in tunneling contact.

Minimal hardware requirements reduce noise sources.

Demonstrated measurements on BiSbTe$_3$ and Si$(111)-(7\times7)$ samples.

Abstract

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