Nanolaminated Al100−Ni / AlO H thin films by hybrid PVD / ALD: An approach towards interface-engineered thin films by dual-route tailoring

Hybrid physical vapour/atomic layer deposition technology has enabled the formation of nanolaminated Al₁₀₀₋_zNi_z/AlO_xH_y (bilayer period: 25/1 nm, z = 0, 2, and 5 at.%) thin films, introducing a novel interface-engineered design strategy with advanced microstructure control. This leverages dual-route tailoring of nanocrystalline Al through 1) compositional grain boundary engineering (Al₁₀₀₋_zNi_z) and 2) well-defined crystalline / amorphous interfaces (Al₁₀₀₋_zNi_z/AlO_xH_y). As ambient plasticity is thought to be governed by dislocation interactions with segregation-modified interfaces & lattice, elucidating the collective role of such barriers in strengthening is essential for establishing a robust design framework. Accordingly, high-resolution analyses by scanning transmission electron microscopy (STEM) and atom probe tomography (APT) established a direct link between enhanced hardness and distinct nanostructural features. The nanolaminated Al₉₅Ni₅/AlO_xH_y thin film here exhibits Ni-rich nanoclusters embedded in a sub-10 nm FCC Al matrix and smooth ∼1 nm amorphous interlayers. Notably, STEM indicated Ni decorating vertical Al grain boundaries, whereas APT reveals these to be distinct Ni-rich nanoclusters. Nanoindentation measurements confirmed hardness of 5.3 GPa for Al₉₅Ni₅/AlO_xH_y versus 2.7 GPa for Al/AlO_xH_y . Calculations showed that comparable strengthening magnitudes originate from both aspects of the dual-route tailored nanostructure: impeding dislocation motion by combined crystalline–amorphous layer confined slip and finely dispersed nanoclusters.