Noble metal alloy thin films by atomic layer deposition and rapid Joule heating

Abstract

Metal alloys are usually fabricated by melting constituent metals together or sintering metal alloy particles made by high energy ball milling (mechanical alloying). All these methods only allow for bulk alloys to be formed. This manuscript details a new method of fabricating Rhodium–Iridium (Rh–Ir) metal alloy films using atomic layer deposition (ALD) and rapid Joule heating induced alloying that gives functional thin film alloys, enabling conformal thin films with high aspect ratios on 3D nanostructured substrate. In this work, ALD was used to deposit Rh thin film on an Al2O3 substrate, followed by an Ir overlayer on top of the Rh film. The multilayered structure was then alloyed/sintered using rapid Joule heating. We can precisely control the thickness of the resultant alloy films down to the atomic scale. The Rh–Ir alloy thin films were characterized using scanning and transmission electron microscopy (SEM/TEM) and energy dispersive spectroscopy (EDS) to study their microstructural characteristics which showed the morphology difference before and after rapid Joule heating and confirmed the interdiffusion between Rh and Ir during rapid Joule heating. The diffraction peak shift was observed by Grazing-incidence X-ray diffraction (GIXRD) indicating the formation of Rh–Ir thin film alloys after rapid Joule heating. X-ray photoelectron spectroscopy (XPS) was also carried out and implied the formation of Rh–Ir alloy. Molecular dynamics simulation experiments of Rh–Ir alloys using Large-Scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) were performed to elucidate the alloying mechanism during the rapid heating process, corroborating the experimental results.

Conformal Noble Metal High-Entropy Alloy Nanofilms by Atomic Layer Deposition for an Enhanced Hydrogen Evolution Reaction

“…First, a two-step approach consisting of sequential ALD and EJH was introduced to fabricate RhRuPtPdIr HEA thin films. , As shown in Figure a, ALD with precise thickness control was first introduced to sequentially deposit the individual layers of Rh, Ru, Pt, Pd, and Ir with a uniform thickness of ∼10 nm each, onto the glassy carbon electrode (GCE) substrate. After ALD growth, the as-deposited Rh/Ru/Pt/Pd/Ir 5-layer underwent EJH at 1000 °C for 1–5 s under low vacuum conditions to induce interdiffusion of various metal atoms in the out-of-plane direction (i.e., along the film thickness) to obtain the HEA thin film.…”

“…The EJH annealing step was conducted with the setup and parameters following our previous work. , In short, the as-deposited Rh/Ru/Pt/Pd/Ir 5-layer thin films on GCE were placed on top of a commercial carbon felt (Fuel Cell Earth Inc.) under low vacuum conditions (<1 Torr). To conduct the EJH process, 3 s of temperature ramping at 10 5 K/s was applied first, and then the samples were annealed at a temperature of 1000 °C for 1, 3, and 5 s.…”

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

“…[36][37][38] EJH of PtIrPd Thin Film: The custom-built electric Joule heating setup and heating parameters have been described elsewhere. [43,44] Briefly, as-deposited PtIrPd thin films on sapphire were placed on top of a carbon felt (Fuel Cell Earth) under mild vacuum conditions (<1 Torr). The alloy film samples were then heated at 785, 980, and 1145 °C, respectively, with a 3 s ramp dwell followed by an annealing dwell of 5 s.…”

“…[41] EJH is an ultrafast heating approach that promotes accelerated interatomic diffusion at high temperatures while kinetically inhibiting phase separation within the few-second-timescale process window. [42][43][44] Hence, we conducted the sequential ALD growth of metal components layerby-layer (i.e., Pt, Ir, and Pd), followed by the EJH post-treatment to obtain homogenous MEA thin films, as shown in Figure 1. PtIrPd MEA thin films with a thickness of %20 nm and an atomic ratio of 35:35:30 at 980 °C were obtained after 5 s EJH.…”

Ultrafast Crystallization of Ordered Mesoporous Metal Oxides and Carbon from Block Copolymer Self‐Assembly and Joule Heating

“…Similar works of Joule heating-induced sintering of metals, nitrides, oxides, and phosphates have been reported by other groups. [38][39][40][41][42][43] However, in all these studies, they did not involve polymer self-assembly, and the structure order and porosity characteristics have not been established at the nanoscale.…”