What kinds of materials can a scanning tunneling microscope examine?

A scanning tunneling microscope (STM) is designed to examine the surfaces of conductive materials by measuring the tunneling current between a sharp probe tip and the sample. Because the instrument relies on the flow of electrons, it is primarily used to image and analyze the atomic structure of metals and semiconductors.1

Specific materials and surfaces that have been successfully examined include:

• Metals: The atomic arrangements of gold, platinum, silver, nickel, and copper have been extensively documented.1
• Semiconductors: Silicon surfaces, particularly their complex reconstructions, have been studied in great detail.1
• Superconductors: The STM can be cooled to temperatures below 4 K to investigate the properties of superconducting materials.1

The microscope is highly versatile regarding its environment; it can operate in high vacuum, ambient air, water, insulating fluids, and ionic solutions used in electrochemistry. Beyond imaging, the STM can also be used to manipulate atoms on a surface or fabricate nanostructures.12