Seeing with Electrons

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About this exhibit

How to drive it

• Click a label on the column to open its instrument-physics card: how it works, typical specifications, how it is calibrated, and live values.
• Drag the 3D column to orbit, scroll to zoom. Keys 1–8 switch modes, Space pauses, L labels, C clarity, R resets the view.
• Drag the detector image to move the specimen stage; scroll it to change magnification. In diffraction, dragging the pattern tilts the crystal. Try to find the zone axis by following the Kikuchi lines.
• 4D-STEM: hover the virtual image to read individual diffraction patterns; drag on the pattern to reshape the virtual detector.
• EDS: click a peak to map that element. EELS: drag on the spectrum to move the energy window.
• Ronchigram: press Scramble, then null the aberrations with the sliders (watch the π/4 circle grow), or press Auto-tune. CBED: thicken the sample to read thickness from the fringes; drag strain to move HOLZ lines.

What is computed, and how

The three specimens are real atomic structures: Au nanoparticles (FCC, [110]) on amorphous carbon; Si [110] against amorphous SiO₂; and a SrTiO₃ Σ5 (310) tilt boundary. Their projected potential is built atom by atom.

TEM and diffraction treat the specimen as a phase object, then apply the full objective-lens transfer function: defocus, C_s, aperture, and temporal and spatial coherence envelopes. STEM convolves the aberrated probe with a Zⁿ scattering map. 4D-STEM computes a real convergent-beam pattern (probe × transmission function, then FFT) at each of 1,600 probe positions. EDS uses real line energies, a Fano-limited detector response and Kramers bremsstrahlung. EELS uses Drude plasmons with Poisson plural scattering and real edge onsets. The Ronchigram is |FFT(probe × amorphous film)|² with the full axial aberration function. CBED/LACBED use two-beam dynamical theory per reflection with 3D structure factors and exact HOLZ geometry.

Simplifications: thick-crystal dynamical scattering (channelling) is approximated by a saturating phase rather than full multislice, and cross-sections are schematic. Trends and length scales are right; absolute intensities are illustrative.