a–c Schematic breakdown of growth process into three steps: deposition of TaNS, columnar growth of silicon amorphous film exploiting the shadowing effect of the TaNS and thermal annealing at 150 °C enhancing the mobility and consequent annihilation of voids at open surfaces (indicated by the red arrows). Grey spheres represent Ta nanoparticles and silicon is designated in blue. The mechanical response under the force of the nanoindenter is indicated for the three structures under study: d columnar, e vaulted, and f sedimentary. The nanoindenter for PF-QNM measurements is shown in green, exerting a compressive force on silicon samples (red arrow). White arrows indicate film stresses, irrespective of indentation; the film response under the nanoindenter is shown in yellow. Red dashed lines indicate sample deformations and small red arrows represent the force distribution in the columns.