We present a multi-tip scanning tunneling potentiometry technique that can be implemented into existing multi-tip scanning tunneling microscopes without installation of additional hardware. The resulting setup allows flexible in situ contacting of samples under UHV conditions and subsequent measurement of the sample topography and local electric potential with resolution down to Å and μV, respectively. The performance of the potentiometry feedback is demonstrated by thermovoltage measurements on the surface by resolving a standing wave pattern. Subsequently, the ability to map the local transport field as a result of a lateral current through the sample surface is shown on and Si(111) − (7 × 7) surfaces.
Due to the voltage spikes occurring when the potentiometry bias voltage is set before the potentiometry feedback and when the topography bias voltage is set before re-activating the topography feedback, a short delay time of a few ms is recommended to be implemented, respectively, to allow the system to settle.
If the voltage probe is not present, it is assumed that the transport field is symmetrical, with the option to correct the voltages later.
Surface photoelectric effects were ruled out by switching off the laser for a short time and still observing the increased potentiometry signal.