Four modules, one instrument
From tunnelling and the feedback loop to scanning and imaging—one module per step, each in stages you can scrub to any moment.
Principles·Universities & research institutes
Research Principle Animation:Scanning Tunnelling Microscope Lab
Research results must be explained to reviewers, partners and the public—but the key things are invisibly small and the principles are subtle: how can an instrument “see” atoms a thousand times smaller than a wavelength of light? This lab explains the scanning tunnelling microscope in code, from quantum tunnelling and the feedback loop to line scanning and an atomic image, in four steps.
Tunnelling current follows I ∝ V·e^(−2κd) with a 4.5 eV work function—each extra 0.1 nm of gap cuts the current about tenfold—and the tip height follows the feedback loop’s response. Drag bias, setpoint and scan speed, or switch to constant-height mode, and the drawing, image and curves respond. Your own project or instrument can be made the same way—as video, GIFs or a web demo.
ForResearch groups, key labs, institutes, R&D centers
STM IMAGING LAB
Scanning tunnelling microscopeTunnelling, feedback and atomic imaging
Tungsten tip · graphite (HOPG) · work function 4.5 eV · lattice 0.246 nm · feedback bandwidth 200 Hz
EXPERIMENT 01EXPERIMENT 02EXPERIMENT 03EXPERIMENT 04
Electrons cross a vacuum they cannot climb over
A one-atom tip and a fast enough feedback loop
Hold the current constant and the tip traces the atoms
Stack the lines and you have a picture of atoms
Classically blockedWave leaks throughWiden by 1 ÅCoarse approachCurrent appearsFeedback locksApproach to setpointPoint by pointOver a defectRaster scanImage formsSpot the defectAtoms resolvedFeedback lags, image distortedConstant height: recording currentNo tunnelling current yet
Filled electron statesBarrierElectron wavefunctionElectrons
Tungsten tipCurrent and feedback signalElectronicsSample atoms
Tip height trace (relief ×2)Trace with an ideal feedbackConstant electron-density contoursTungsten tip
Colour = height: brighter is higherScan pathGraphite atoms STM does not show
Classically, electrons bounce back hereVacuum barrier ~4.5 eV above the electronsWavefunction decays exponentiallyA sliver gets through (drawn ×1000)1 Å wider: current drops to ~1/9Piezo tube moves x, y and zElectrochemically etched tungsten tipA single atom at the apexCurrent amplifier: 1 nA → 1 VBias between tip and sampleFeedback: compare current, move tipCurrent flows almost only through this atomTip lowered until current equals setpointTip height trace = surface reliefConstant height: tip still, current recordedMissing atom: the tip dipsTop-layer carbon atomsThe tip rasters line by lineBright spots are atoms in a triangular latticeOnly the highlighted set of atoms showsA dark pit: one atom missingHeight along the line through the defectElectron-density contours flatten with height
BarrierSlope −2κTip height catches upCurrent errorTime constant 0.8 msTrue surfaceMeasuredDefectConstant currentConstant heightAtoms resolvable
↑ Relative probabilityRelative value (%)Height (pm)Measured / true relief (%)Distance from tip surface (Å)Time (ms)Along the scan (Å)Scan speed (nm/s) →
Setpoint current+1 Å: ~1/9 the current
↑ Current (nA, log)Tip–sample gap (Å) →
0%
What to watch
A few ångströms of vacuum separate tip and sample, and electrons lack the energy to climb over. But electrons are waves: the wavefunction decays as e^(−κx) in the vacuum and a sliver reaches the far side—that sliver is the tunnelling current. Each extra ångström cuts it to about 1/9, which makes it exquisitely distance-sensitive.
The tip sits on a piezoelectric tube that moves fractions of a nanometre per volt. A current amplifier turns nanoamps into volts; the feedback loop compares this with the setpoint and drives the tube up or down. If a single atom sticks out at the apex, nearly all the current flows through it.
At every step the feedback adjusts the height to restore the setpoint, so the tip’s path is the surface relief. Scan too fast and the loop lags—the trace flattens and smears, and atoms blur. In constant-height mode the tip stays put and the current variation is recorded instead.
The tip rasters line by line and each point’s height is drawn as colour: graphite’s atoms appear as a triangular lattice 0.246 nm apart, and a missing atom shows as a dark pit. Only every other carbon atom lights up, because of how the layer below is stacked.
01ABOUT THIS LAB
What’s in this lab
Numbers computed live
Current, gap, corrugation and feedback lag come from the equations; the energy diagram, scan trace, image and curves share the same numbers.
Drag parameters, see results
Bias, setpoint, scan speed and mode are adjustable, so you can show “what happens if you scan too fast” on the spot.
One build, many formats
The same lab records as a project video, splits into step figures for papers and posters, or runs on a lab website or in a science exhibit.
02WHO USES IT
How universities & research institutes clients use principle animation
Research groups, key labs, institutes, R&D centers
Grant defenses, project reviews, paper animations, journal covers and video abstracts
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Page updated 2026-10-24