Epitaxial growth of void-free Pd nanofilm using ethylenediamine via one-cell electrochemical-atomic layer deposition

초록

This study focuses on achieving void-free, epitaxial Pd nanofilms by employing ethylenediamine (En) in a one-cell electrochemical atomic layer deposition (E-ALD) configuration. An electrical potential was applied to form a Cu underpotential deposition (UPD) on an Au substrate, followed by the replacement of Cu with Pd ions under an open circuit potential (OCP). In the absence of En, uncontrolled Pd co-deposition during the potential applying step disrupted the atomic-scale displacement pathway and generated nanovoids, whereas the introduction of En suppressed Pd co-deposition and slowed the Cu–Pd displacement kinetics, thereby preventing void formation. At an En concentration of 75 mM, cross-sectional TEM analyses demonstrate a Pd nanofilm with clear lattice registry to the Au substrate, confirming epitaxial (111) growth without nanovoid formation. UV–vis spectroscopy confirms the selective interaction between En and Pd ions, while cyclic voltammetry and EQCM measurements support the suppressed Pd co-deposition behavior and slowed displacement kinetics. XPS further confirms reduced Cu residues and improved film purity. These findings demonstrate that suppressing Pd co-deposition during SLRR enables the epitaxial, void-free nanofilms through a one-cell E-ALD approach, opening new opportunities for interface-engineered thin-film fabrication. Copyright © 2026. Published by Elsevier B.V.

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