Atomic Layer Deposition of High-Purity Palladium Films from Pd(hfac)₂ and H₂ and O₂ Plasmas

Abstract

A plasma-assisted atomic layer deposition (ALD) process has been developed that allows for low temperature (100 °C) synthesis of virtually 100% pure palladium thin films with low resistivity of 24 ± 3 μΩ cm on oxide substrates. This process is based on Pd(hfac) 2 (hfac = hexafluoroacetylacetonate) precursor dosing followed by sequential H 2 plasma and O 2 plasma steps in a so-called ABC-type ALD process. Gas-phase infrared spectroscopy studies revealed that the O 2 plasma pulse is required to remove carbon contaminants from the Pd surface that remain after the H 2 plasma reduction step. Omitting the O 2 plasma step, that is, Pd ALD from Pd(hfac) 2 and H 2 plasma in a typical AB-like ALD process, leads to a carbon contamination of >10% and significantly higher resistivity values. From transmission electron microscopy, it has also been observed that the ABC-type process leads to a faster nucleation of the Pd nanoparticles formed during the initial stage of film growth. As this novel process allows for the deposition of high-purity Pd at low temperatures, it opens prospects for various applications of Pd thin films and nanoparticles.

Sub-nanometer dimensions control of core/shell nanoparticles prepared by atomic layer deposition

“…This understanding allowed us to establish the conditions for the controllable synthesis of core/shell NPs. To deposit the Pd cores, a plasma-assisted ALD process employing Pd(hfac) 2 dosing with subsequent H 2 plasma and O 2 plasma exposure at 100°C has been used [46]. The ALD precursor step consisted of 3 s of Pd(hfac) 2 dosing with Ar as a carrier gas, followed by a 5 s pump step.…”

Atomic Layer Deposition of Pd Nanoparticles on N‐Doped Electrospun Carbon Nanofibers: Optimization of ORR Activity of Pd‐Based Nanocatalysts by Tuning Their Nanoparticle Size and Loading

“…Owing to lower loading and smaller size of Pd nanoparticles for Pd10/nCNF and Pd20/nCNF, we could not get any meaningful signals associated to crystalline phases of Pd (Figure a). On the other hand, weak signals are clearly visible for Pd30/nCNF and Pd40/nCNF which can be attributed to (111) lattice phase of Pd . Moreover, high resolution TEM (HRTEM) analysis of Pd20/nCNF explicitly evidenced the (111) facet orientation of Pd nanocrystals (Figure S4) …”

Enhanced Catalytic Glycerol Oxidation Activity Enabled by Activated‐Carbon‐Supported Palladium Catalysts Prepared through Atomic Layer Deposition

“…These NPs grow with the increasing number of cycles, coalesce and finally form a continuous film on which the ALD growth continues at a constant rate ,. Therefore, ALD of noble metals can be used as a viable route for the preparation of either films, or NPs ,. Due to their excellent catalytic properties, highly dispersed Pd NPs have been grown by ALD and have been tested on various supports (TiO 2 , carbon, Al 2 O 3 ).…”