Combinatorial surface nanostructuring in aluminium-niobium system

Co-deposition at glancing angles is used for deposition of an AlNb thin film library with a compositional resolution of 0.8 at.% mm−1 and a total compositional spread of 55 at.%. Atomic self-shadowing leads to nanostructure formation along the compositional gradient. The morphology of the obtained different nanowires is fundamentally studied together with their crystallinity in the cubic system and is linked to specific AlNb nanostructured alloys. Composition and morphology of the nanowires, naturally emerging as coupled variables due to the deposition geometry, are decoupled using the deposition distance. This allows identifying conditions for reproducing a single wire for further applications. Electrical properties are mapped across the library by scanning Kelvin probe microscopy and four point resistivity measurements. Nanowires with low work function are identified at low Nb concentration. Contact angle measurements are performed along the library before and after anodic oxide formation, and these changes are mapped as a function of composition. The presented compositional mappings are relevant for alloys selection in applications where surface tuning or functionalization is paramount.