Anomaly of Film Porosity Dependence on Deposition Rate

TL;DR

This paper investigates an unexpected increase in film porosity at lower deposition rates during physical vapor deposition, revealing complex interactions affecting nanorod formation.

Contribution

It uncovers the anomaly where lower deposition rates lead to higher porosity, attributed to substrate wetting, nucleation density, and nanorod dimensions.

Findings

Porosity increases as deposition rate decreases.

Nanorods are well separated at 1 nm/second.

More uniform films form at 6 nm/second.

Abstract

This Letter reports an anomaly of film porosity dependence on deposition rate during physical vapor deposition - the porosity increases as deposition rate decreases. Using glancing angle deposition of Cu on SiO2 substrate, the authors show that the Cu film consists of well separated nanorods when the deposition rate is 1 nm/second, and that the Cu films consists of a more uniform (or lower porosity) film when the deposition rate is 6 nm/second; all other deposition conditions remain the same. This anomaly is the result of interplay among substrate non-wetting, density of Cu nuclei on the substrate, and the minimum diameter of nanorods.