AsianScientist (Jan. 24, 2017) – Metals can now come in a wider range of colors, thanks to work by South Korean researchers. Their method, which uses thin films of germanium, has been described in an article published in Nanoscale.
Coating metals with an ultra-thin layer of semiconducting materials can cause the color of the metal to change through the thin-film interference effect. Previous studies showed that color changes depend on the thickness of the semiconducting films; however, there have been some difficulties in using this method due to the rapid change of colors.
In the present study, a team led by Professor Jang Kyung-in from Daegu Gyeongbuk Institute of Science and Technology and Professor Song Young-min from Gwangju Institute of Science and Technology have succeeded in developing a method to control various color changes by coating several nanometers of semiconducting materials on a metal substrate.
The research team coated a thin germanium film of 5 to 25 nanometers on a gold substrate by utilizing oblique angle deposition. As a result, they succeeded in producing various colors such as yellow, orange, blue, and purple at will according to the thickness and deposition angle of the germanium coating.
They confirmed that the extension of the color range and purity of color was enhanced due to the porous structure of the germanium layer. The researchers were also able to control the wavelength and purity of the colors by changing the thickness of the germanium film using the oblique angle deposition method.
“The result of this research is the development of a simple method of applying various colors to existing electronic devices. Currently, we have succeeded in expressing single colors, but we may also be able to coat patterns such as symbols and pictures,” Jang said.
“In the future, I think it can be used in coating visual designs on flexible devices such as solar cells, wearable devices, and displays that are used for various purposes including building exterior walls. It can also be applied in camouflage by coating things with the same pattern or color as the surrounding objects.”
The article can be found at: Yoo et al. (2016) Ultra-thin Films with Highly Absorbent Porous Media Fine-tunable for Coloration and Enhanced Color Purity.
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Source: Daegu Gyeongbuk Institute of Science and Technology.
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