Fabrication of PtIrPd Noble Metal Medium Entropy Alloy Thin Film by Atomic Layer Deposition

Abstract

Noble metal medium entropy alloy (MEA) thin films have recently attracted enormous research interests recently because of their great potential in the catalytic application. However, conventional bottom‐up fabrication methods for MEA thin film such as magnetron sputtering face enormous challenges including precise control over film thickness and consumption of costly high‐purity noble metal targets. Herein, a facile and tunable approach is developed coupling sequential atomic layer deposition (ALD) of noble metal layers with electric Joule heating (EJH) alloying process to grow platinum‐iridium‐palladium (PtIrPd) MEA thin films. The PtIrPd MEA thin film with a thickness of ≈20 nm and an atomic ratio of 35:35:30 is successfully fabricated. The effect of EJH processing temperature on the film morphology and structure evolution is investigated. ALD provides flexibility in the metal deposition sequence with meticulous thickness control and atomic composition precision, while the ultrafast EJH ramping/cooling rates promote homogeneous alloying of MEA combinations inhibiting phase separation. Furthermore, the integrated method circumvents a major obstacle of finding a common ALD temperature window for different noble metal precursors as well as opens new pathways for the controllable synthesis of multicomponent metal alloy thin films with potential catalytic, magnetic, and optical properties.

ALD-made noble metal high entropy alloy nanofilm with sub-surface amorphization for enhanced hydrogen evolution

“…The feasibility of this method was veried in our previous works. 50,51 The sub-surface area of HEA exhibited partial amorphization and nanocrystallites, which was caused by the explosive crystallization that occurred during the cooling phase of the EJH process. 52,53 The ultrafast ramping/cooling rate also enabled the alloying of multiple layers without encountering phase separation and precipitation.…”