Scanning Tunneling Microscope: Constant-Current Imaging

A scanning tunneling microscope doesn't touch the surface it images — it feels it, through a quantum-mechanical tunneling current that falls off exponentially with the sub-nanometre gap between a sharp conducting tip and the sample. This simulation renders an atomic lattice with a step edge and an adsorbed-atom defect, then rasters a tip across it exactly as a real STM does: a feedback loop reads the tunneling current from I ∝ V·exp(-2κd) and continuously adjusts the tip height to keep that current locked at a setpoint, tracing out the surface topography one scan line at a time. Toggle constant-height mode to see the alternative imaging strategy, tune the work function and setpoint current to see how they change the tip's standoff distance, and watch the small readout panel build up a genuine reconstructed STM image, pixel by pixel, from the live feedback trace.