Rastertunnelmikroskopie

Rastertunnelmikroskopie, commonly abbreviated as STM, is a surface‑analysis technique that enables imaging and manipulation of conductive materials at the atomic scale. The method relies on quantum tunnelling: when a sharp metallic tip is brought within a few angstroms of a sample surface and a bias voltage is applied, electrons tunnel between tip and sample, creating a measurable current. By maintaining a constant tunnelling current while raster‑scanning the tip across the surface, a topographic map of the electron density is generated.

The concept was first demonstrated in 1981 by Gerd Binnig and Heinrich Rohrer at IBM Zurich, for which they received the Nobel Prize in Physics in 1986. Early instruments operated in ultra‑high vacuum and at cryogenic temperatures, but subsequent developments have expanded STM to ambient conditions and various temperature regimes.

STM provides sub‑ångström vertical resolution and lateral resolution of about 0.1 nm, allowing direct observation of individual atoms, defects, and adsorbates on conductive surfaces. Besides imaging, the technique can be used for spectroscopic measurements (STS) that probe local electronic states, and for atom‑by‑atom manipulation, enabling the construction of prototype nanostructures.

The method is limited to conductive or semiconductive samples, and the requirement for an atomically sharp tip can affect reproducibility. Surface cleanliness and stability are critical, as vibrations or thermal drift can distort images. Despite these constraints, rastertunnelmikroskopie remains a cornerstone of nanoscience, influencing fields such as surface physics, materials science, chemistry, and emerging quantum technologies.