Focused Ion Beam Milling Simulator (Top-Down 2D)

Ion Beam

Incidence angle θ 45°

Beam dose (ion current) 5

Mill pattern

Live Readouts

Sputter yield Y(θ)

— at/ion

Mill rate

— nm/s

Deepest point milled

0.0 nm

How it works

A focused ion beam (FIB) fires ~10–30 keV gallium ions (Ga⁺) at a surface. Each ion strikes an atom, triggers a collision cascade in the lattice, and knocks out (sputters) a handful of surface atoms — material is removed one ion at a time, with no chemistry or resist involved, unlike lithography.

How many atoms leave per incident ion — the sputter yield Y — depends strongly on the incidence angle θ measured from the surface normal. This sim uses a Sigmund/Yamamura-type angular model, the same one driving the 3D version of this simulator:

Y(θ) = Y₀ · cos(θ)⁻ᶠ · exp[ −Σ·(sec θ − 1) ]
  Y₀ = 2.1 atoms/ion   (Si, Ga⁺, normal incidence)
  f = 1.7,  Σ = 0.9

Mill rate:  R(θ) = R₀ · Y(θ)/Y₀   [nm/s]
Depth removed at a cell:  Δz = R(θ) · Δt

θ small (near-normal) — ions penetrate straight in, most energy is deposited deep in the bulk, yield is near its baseline Y₀.
θ ≈ 58° — the model's exact peak here: the cascade sits closer to the surface, so more struck atoms have a clear escape path; yield tops out around 2.78 at/ion versus 2.1 at normal incidence, which is why real FIB tools tilt the stage for fast bulk milling.
θ → 90° (grazing) — ions increasingly reflect off the surface instead of embedding, and the exponential term wins out, so yield collapses back toward zero.

This top-down view is a true bird's-eye reading of the same milled grid the 3D scene shows in perspective: cell brightness encodes remaining column height (bright = untouched, dark = fully milled), and the amber line at the beam spot shows the beam's horizontal footprint — its projected reach across the surface at the current tilt, h·tan(θ), which is why that line barely shows at normal incidence and stretches far out near grazing angles. Drag to pan, scroll or pinch to zoom, and watch the live cross-section track the milled profile along the grid's center row.

Ion beam + footprint Unmilled surface Milled (removed)

drag to pan · scroll to zoom

Focused Ion Beam Milling Simulator — Top-Down 2D