Structural Colors on Al Surface via Capped Cu-Si3N4 Bilayer Structure

M. A. Rahman, Dongkyu Kim, Deepshikha Arora, Joo Youl Huh, Ji Young Byun

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


Tunable structural colors have a multitude of applications in the beautification of mobile devices, in the decoration of artwork, and in the creation of color filters. In this paper, we describe a Metal-Insulator-Metal (MIM) design that can be used to systematically tune structural colors by altering the thickness of the top metal and intermediate insulator. Cu and Si3N4 were selected as the top metal and intermediate insulator layers, respectively, and various reflection colors were printed on Al. To protect the Cu surface from scratchiness and oxidation, a number of capping layers, including SiO2, LPSQ, PMMA, and the commercially available clear coat ProtectaClear, were applied. In addition to their ability to protect Cu from a humid environment without deteriorating color quality, ProtectaClear and LPSQ coatings have minimal angle dependency. Furthermore, a bilayer of PMMA/SiO2 can protect the Cu surface from the effects of humidity. In addition, the PMMA/SiO2 and ProtectaClear/SiO2 bilayers can also protect against corrosion on the Cu surface. The colors can be tuned by controlling the thickness of either the metal layer or intermediate insulator layer, and vivid structural colors including brown, dark orange, blue, violet, magenta, cyan, green-yellow, and yellow colors can be printed. The measured dielectric functions of Cu thin films do not provide any evidence of the plasmonic effect, and therefore, it is expected that the obtained colors are attributed to thin-film interference.

Original languageEnglish
Article number471
Issue number2
Publication statusPublished - 2023 Feb

Bibliographical note

Funding Information:
This research was funded by the Korea Institute of Science and Technology [grant numbers 2N61840, 2E31751, and 2N66610] and the R&D convergence program of the National Research Council of Science & Technology of the Republic of Korea [grant number CAP-16-10-KIMS].

Publisher Copyright:
© 2023 by the authors.


  • Cu thin film
  • capping layer
  • metal-insulator-metal structure
  • reflection colors

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Mechanical Engineering
  • Electrical and Electronic Engineering


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