Spatial characterization of thickness in thin films deposited by thermal evaporation

Abstract

This work analyzes the spatial thickness distribution of aluminum thin films deposited onto a glass substrate via thermal evaporation. A methodology combining a gridded lift-off mask with optical mapping enabled precise large-area topographic characterization. The experimental data were fitted to the Knudsen cosine law (R2 = 0.92), confirming a radial thickness decay with a maximum central thickness of d0 = (93.0 ± 0.5) nm. The empirical beaming parameter (n = 0.9 ± 0.3) is highly consistent with an ideal planar surface source (n = 1). This demonstrates that the crucible used distributes the atomic flux predictably, acting as a flat emitting area without inducing severe collimation. Finally, the preservation of this distinct directional profile is attributed to the high-vacuum regime, which prevents the intermolecular flux dispersion typical of higher working pressures.