Optimized Broad Ion-Beam Workflow for Cross-Sectioning Multilayer Polymer Structures

Broad ion milling of multilayer polymer laminates is often limited by curtaining, redeposition, and thermally driven smear, which compromise structural fidelity at the interface. We systematically map the impact of accelerating voltage, stage kinematics, beam entry direction, and temperature. Lower voltages (0.5-2 kV) under-mill, whereas 4 kV and higher voltages introduce melting and interlayer blending; an operating point near 3 kV for 4 h consistently clears the wall with minimal and correctable curtaining. Superposing a small oscillatory component on the stage motion (60 cycles/min with ±15° swing) relative to baseline dynamics suppresses curtaining by averaging incidence and reducing dwell anisotropy, lowering redeposition features. Milling from the hard side sets a flat, low-yield reference plane that prevents self-amplifying relief as the front traverses softer layers; soft to hard promotes shadowing, redeposition, and long curtains. Milling at room temperature improves planarity with acceptable structural and chemical fidelity; a brief near-normal flat-milling finish truncates residual long-wavelength relief when applied in short, inspected passes. Energy dispersive X-ray spectroscopy (EDS) acquired at multiple magnifications indicates that the apparent composition is driven by which bands are exposed and their areal coverage rather than chemistry. Validation on a second laminate of different composition and thickness demonstrates transferability.