Strategy for improving Ag wetting on oxides: Coalescence dynamics versus nucleation density

• Published in: Applied surface science 2020-04, Vol.510, p.145515, Article 145515
• Main Authors: Zhao, Guoqing, Jeong, Eunwook, Choi, Eun-Ae, Yu, Seung Min, Bae, Jong-Seong, Lee, Sang-Geul, Han, Seung Zeon, Lee, Gun-Hwan, Yun, Jungheum
• Format: Article
• Language: English
• Subjects: DFT simulation; Nanoparticle coalescence; Nucleation density; Silver; Transparent electrode; Wetting improvement
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2020.145515

The dominating factor in the wetting improvement of Ag on SiO2 is early transition in the coalescence of Ag nanoparticles from full to partial fusion in the presence of minor concentrations of wetting agents, and not the nucleation density. [Display omitted] •Structural evolution of Ag on SiO2 is tracked from early stages of nanoparticle growth.•Deviating from a typical full coalescence dominates the improvement of Ag wetting.•Initial number density of Ag nanoparticles is irrelevant to improving Ag wetting.•Lower free energy of nanoparticles causes strong deviation from full coalescence.•Al and O reduce interfacial and surface free energy, respectively. Wetting of noble metals on oxide structures becomes problematic when attempting to grow two-dimensional, atomically smooth and continuous thin film structures because of a strong tendency for three-dimensional growth. This study redefines the crucial factor that controls the wetting of vacuum deposited Ag on SiO2 substrates and refutes the currently accepted assertion that increasing the nucleation density of Ag is responsible for promoting wetting. Ultrahigh-resolution electron microscopy, supported by X-ray spectroscopic techniques, was used to observe how fast Ag nanoparticles evolve to a continuous film by manipulating the contribution of the crucial factor on Ag wetting, and the results were numerically interpreted using first-principles density functional theory calculations to reveal the relevant dynamics. The experimental and numerical results confirmed that the earliest transition of the coalescence dynamics of Ag nanoparticles from full to partial coalescence is the dominating factor in improving Ag wetting. Surprisingly, Ag wetting is independent of the initial nucleation density of Ag nanoparticles. Favorable partial coalescence with more irregularities in the shapes was readily attainable by artificially reducing the thermodynamic surface and interfacial free energies of the evolving Ag nanoparticles through the addition of a small concentration of Al or O as a wetting agent.