How do scientists use a scanning tunneling microscope to study oxygen absorption on surfaces?

Scientists use a scanning tunneling microscope (STM) to study oxygen absorption by leveraging its ability to resolve individual atoms and map surface conductivity.

The instrument operates by positioning a sharp probe tip a few angstroms from a sample surface. By applying a small voltage, electrons tunnel across the gap between the tip and the surface. Because the tunneling current is extremely sensitive to the distance between the tip and the sample, the STM can detect minute variations in electron density. When oxygen molecules interact with a metal surface, they alter the local electronic structure; the STM registers these changes as the probe scans the surface, allowing researchers to document the absorption and diffusion of these species in detail.

To ensure the accuracy of these observations, scientists often conduct these experiments in high-vacuum environments to maintain sample cleanliness. This allows for the precise mapping of atomic arrangements and the study of how different chemical species interact with the surface lattice.1