A scanning tunneling microscope (STM) images a conducting surface without any lens at all. It holds an atomically sharp needle just a few tenths of a nanometre above the sample and measures the tiny electric current of electrons that quantum-mechanically tunnel across that vacuum gap even though they don't have enough energy to classically cross it. This simulation reproduces the same barrier-tunneling physics as the tunneling-probability model on the article page, but wired up as a real 3D scanning instrument over a lattice of atoms.
Moving the tip just one ångström closer to the surface — about the radius of a hydrogen atom — can change the tunneling current by a factor of ten. That extreme sensitivity, a direct consequence of the exponential in the tunneling formula, is what lets STM resolve individual atoms.
Drag an atomically sharp tip across a lattice of surface atoms and watch the quantum tunneling current — which depends exponentially on the vacuum gap — build a real STM-style topographic image, one raster line at a time.
Tunneling current falls off exponentially with tip-sample distance and barrier (work function) height. In constant-current mode the tip's height trace over the raster becomes a direct atomic-resolution map of the surface.
Adjust tip height, work function, bias voltage and scan speed. Toggle between constant-current and constant-height imaging modes and watch the trail mesh accumulate a topographic scan of the atom lattice.
Gerd Binnig and Heinrich Rohrer won half of the 1986 Nobel Prize in Physics for inventing the STM — the first instrument to directly image individual atoms on a surface using nothing but a quantum tunneling current.