Shuffling atomic layer deposition gas sequences to modulate bimetallic thin films and nanoparticle properties

Atomic layer deposition (ALD) typically employs metal precursor and co-reactant pulses to deposit thin films in a layer-by-layer fashion. While conventional ABAB-type ALD sequences implement only two functionalities, namely a metal source and ligand exchange agent, additional functionalities have emerged, including etching and reduction agents. Herein, we construct gas phase sequences – coined as ALD+ – with complexities reaching beyond classic ABAB-type ALD by freely combining multiple functionalities within irregular pulse schemes, e.g. ABCADC. The possibilities of such combinations are explored as a smart strategy to tailor bimetallic thin film and nanoparticle (NP) properties. By doing so, we demonstrate that bimetallic thin films can be tailored with target thickness and through the full compositional range, whilst the morphology can be flexibly modulated from thin films to NPs by shuffling the pulse sequence. These complex pulse schemes are expected to be broadely applicable, but are here explored for Pd-Ru bimetallic thin films and NPs.