Surface morphology of silver thin films exposed to water vapour and/or oxygen in vacuum

ABSTRACT

Silver thin films degrade when subjected to environmental tests at high humidity. As environmental tests are typically conducted in air, the effect of oxygen, a component other than water vapour, cannot be ignored. In this study, silver thin films deposited in vacuum were subjected to environmental tests in an atmosphere of water vapour, oxygen, and a mixture of water vapour and oxygen in the same chamber. The surface morphologies of the samples were examined using optical and atomic force microscopy. A comparison of surface roughness showed that the mixture of water vapour and oxygen gave the highest increase of the roughness of the silver surface, followed by water vapour. The degradation caused by water vapour and oxygen has been discussed before, but this is the first time that the effect of water vapour alone has been revealed. As surface roughness affects optical properties, a corresponding decrease in specular reflectance was observed.

KEYWORDS:

• Silver
• thin film
• water vapour
• oxygen
• vacuum
• roughness
• degradation

Acknowledgements

This paper is based on a presentation given at Interfinish2020, held on-line 6–8 September 2021, organised by the Surface Finishing Society of Japan, supported by the International Union of Surface Finishing.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by JSPS KAKENHI [grant number JP19H02471].