Simplified feedback control system for Scanning Tunneling Microscopy

TL;DR

This paper presents a computer-based feedback control system for Scanning Tunneling Microscopy that enables ultra low noise surface studies at cryogenic temperatures, demonstrating its effectiveness on various advanced materials.

Contribution

It introduces a novel computer and USB-based feedback mechanism for STM, simplifying the system and improving noise performance compared to traditional digital circuits.

Findings

Successful ultra low noise measurements at cryogenic temperatures.

Effective imaging of diverse advanced materials.

Demonstrated system's capability on multiple compound types.

Abstract

A Scanning Tunneling Microscope (STM) is one of the most important scanning probe tools available to study and manipulate matter at the nanoscale. In a STM, a tip is scanned on top of a surface with a separation of a few \AA. Often, the tunneling current between tip and sample is maintained constant by modifying the distance between the tip apex and the surface through a feedback mechanism acting on a piezoelectric transducer. This produces very detailed images of the electronic properties of the surface. The feedback mechanism is nearly always made using a digital processing circuit separate from the user computer. Here we discuss another approach, using a computer and data acquisition through the USB port. We find that it allows succesful ultra low noise studies of surfaces at cryogenic temperatures. We show results on different compounds, a type II Weyl semimetal (WTe$_2$), a quasi two-dimensional dichalcogenide superconductor (2H-NbSe$_2$), a magnetic Weyl semimetal (Co$_3$Sn$_2$S$_2$) and an iron pnictide superconductor (FeSe).