Preparation of Ag–Fe2O3-Based black and electrically insulating coatings by magnetron sputtering from metal targets. (April 2023)

• Record Type: Journal Article
• Authors: Tanaka, Satoru; Ishii, Akihiro; Yamaguchi, Mina; Oikawa, Itaru; Yamazaki, Yusuke; Imura, Masaaki; Takamura, Hitoshi
• Is Part Of: Vacuum. Volume 210(2023)
• Publication Date: 2023-04
• Subjects: Optical coating -- Black insulator -- Cermet nanomaterial -- Plasmonic material -- Visible-light absorber -- Magnetron sputtering; Vacuum -- Periodicals; 621.55
• DOI: 10.1016/j.vacuum.2023.111839
• Languages: English
• ISSNs: 0042-207X

Abstract

Abstract: Black and electrically insulating coatings provide touch panel displays with a classic appearance. In this study, black and electrically insulating Ag–Fe2 O3 -based coatings were prepared using reactive magnetron sputtering, stainless steel and silver foil. The thin films prepared with oxygen introduction and no Ag foil showed blue light absorption and high electrical resistance, which are comparable to those of Fe2 O3 single crystals. The optimal Ag foil size for maintaining a high electrical resistivity of 10 8 Ω·sq −1 was determined to be 54 mol%Ag in the film samples. Black and electrically insulating thin films composed of metallic Ag, amorphous Ag–Fe–O, and slightly crystallized Fe2 O3 were prepared using 3.4 or 3.9 %O2 . Metallic Ag segregated randomly in the high-refractive-index Fe2 O3 -based matrix, resulting in plasmonic absorption over a wide range of wavelengths centered in the red-wavelength region. At 3.9 %O2, a high sheet resistance of 10 8 Ω·sq −1 and strong visible absorption of 35.2 μm −1 (on average), slightly deviating by 2.4 μm −1 were simultaneously achieved by clear phase separation of the Ag grains and Fe2 O3 -based matrix. A clear phase separation mechanism based on thermodynamic nonequilibrium oxidation of the metallic Ag phase is proposed. Highlights: Black insulative Ag–Fe2 O3 -based coating was prepared by sputtering from metal target. Visible light absorption of 35 ± 2 μm −1 with resistance of 10 8 Ω·sq −1 was achieved. Oxygen dissolution into metallic silver is important to be black and insulative. Substitutional oxygen dissolution is experimentally and theoretically suggested. This process has advantages for widespread applications in display industry.