Atomistic Insights into Aluminum Doping Effect on Surface Roughness of Deposited Ultra-Thin Silver Films.

Zhong Tian,Qing Peng,Shengjun Zhou,Lin Jay Guo,Han Yan,Can Ding,Peng Li,Qi Luo

doi:10.3390/nano11010158

Abstract

Ultra-thin and continuous metallic silver films are attracting growing interest due to the applications in flexible transparent conducting electrodes. The surface morphology and structure of silver film are very important for its electrical resistivity and optical loss. Therefore, roughness control is essential for the production of ultra-thin metallic electrode film. We have investigated the effect of aluminum doping on the improvement of surface morphology of ultra-thin silver films using molecular dynamics simulations. Al-doped silver films showed smaller surface roughness than pure silver films at various substrate temperatures. When the temperature of the substrate was 600 K, the roughness of Al-doped silver film first decreased, and then increased with the increase of the incident velocity of silver atoms. Silver atoms were more likely to agglomerate on the surface of the substrate after adding aluminum atoms, as aluminum dopants promoted the immobilization of silver atoms on SiO2 substrate due to the anchoring effect. The smoother surface could be attributable to the reduced mean free path of silver due to the cage effect by the aluminum dopant.

Highlights

Zhang et al developed Al-doped silver films on fused silica substrate and investigated the electrical and optical properties, and the results show that organic photovoltaic devices using Al-doped silver films as transparent cathodes produce better efficiency than those made with indium tin oxide (ITO) electrodes [18]
These processes indicate that silver atoms are more likely to agglomerate on the surface of the substrate after adding aluminum atoms, and aluminum atoms mitigate the migration behavior of silver atoms, which confirms that the smoothness of Al-doped silver film is better than pure silver film
We have systematically studied the effects of aluminum doping on the initial growth of ultra-thin silver films using molecular dynamics simulations

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Large area metal films can be prepared by electron beam and magnetron sputtering, rough surface morphology is often obtained during the deposition process, as a result of thin silver films grown in the Vomer–Webber mode on polycrystalline substrates [9,10] To address this issue, much experimental and theoretical research on the fabrication of smooth ultra-thin silver films has been carried out. High-efficiency transparent organic photovoltaics have recently been realized by using the doped silver film [21] These results reveal that doping in the deposition process can greatly improve the performance of ultra-thin silver film electrodes. A separate discussion of the effects of concentration and incident kinetic energy in atomistic insights would be helpful for further investigation

Model and Methods

Effects of Aluminum Composition

Effects of Initial Incident Velocity of Deposition Atoms

Atomic Migration Mechanism

Conclusions