2D companion to the 3D ALD model: the same self-limiting half-reaction chemistry, alternating two gas-phase precursors separated by inert purges, read off four live plots instead of a rendered 3D grid:
θ_A(dose) = 1 − exp(−k·D) (Langmuir-type saturation)
Δh/cycle = GPC₀ · θ_A · f(T) (ideal, self-limiting)
f(T) = 1 inside the "ALD window"
f(T) < 1 below window (slow/condensing)
parasitic growth > 0 above window (precursor decomposes, CVD-like)
- Cross-section (top-left) — a side-on strip of substrate growing column by column through Pulse A → Purge → Pulse B → Purge, coloured by local film thickness; roughness above the ALD window shows up as uneven column heights, exactly like the 3D scene.
- Dose saturation curve (top-right) — θ_A vs. exposure dose D for the current reactivity, with the live dose point marked. Past the saturation knee, more dose cannot add a second layer in the same pulse — that plateau is the defining ALD signature.
- ALD window (bottom-left) — growth-per-cycle vs. substrate temperature for the selected material: a flat GPC₀ plateau inside the window, a fall-off below it (incomplete ligand exchange) and a rise above it (thermal decomposition, CVD-like).
- Thickness vs. cycles (bottom-right) — the live growth trace for this run; a straight line means ideal linear ALD growth, a kink upward means the process has drifted into CVD-like runaway.
- Pulse / purge duration sliders — control the real timing of the ABAB cycle; shorter purges leave more residual precursor for the next reagent to react with (visualised in the cross-section overlap), shorter pulses can under-saturate the surface at low dose.
- Auto-stop — halts the run after a chosen number of cycles so you can compare final thickness across parameter sets without babysitting the clock.
Real-world relevance: this four-step ABAB cycle is exactly how semiconductor fabs deposit high-κ gate oxides, and how anticorrosion, antireflective and barrier nanocoatings are actually grown — nanometre by nanometre, with sub-ångström thickness control.