Japan: Material Science Vivid Colors with Subwavelength Resolution
Editor: Alexander Stark
A trio of researchers at Osaka University recently demonstrated precise color control using monocrystalline silicon. Their colorful findings were published in Nano Letters.
Bright-field optical microscope image of the Si nanostructure arrays. Si nanostructures of different sizes exhibit distinct reflection colors. (scale bar is 20 μm).
(Source: Takahara et al. Nano Letters)
Osaka/Japan — Until now, the metamaterials used to create tunable color from structural geometry have been based on metals. Although effective in achieving high resolutions, metallic materials suffer from inherent energy losses at visible wavelengths, which makes optimizing color purity challenging. By comparison, the resonance of silicon materials enables high reflectance and purity.
According to study corresponding author Junichi Takahara, the use of silicon achieves both high resolution and high saturation. "All-dielectric materials that can produce individual color pixels with high-resolution, without color mixing, offer distinct advantages over metallic materials,” she said.
The metamaterial arrays feature nanoscale patterns that function as antennae, which convert optical radiation into localized energy. Electron beam lithography was used to create masks, which were used to protect the silicon surface from subsequent plasma etching. The team was able to generate vivid colors controlled completely by the geometry of the antennae, also demonstrating white light generation, which is important for full-color printing. In addition, two-color information was inherent in each pixel and could be revealed by changing the polarization of the incident light.
The subwavelength resolution was demonstrated by generating a clearly discernable yellow and blue checkerboard pattern within unit areas of just 300×300 nanometers. In terms of eventual applications, this translates into printing at ~85,000 dpi.
Gallery
“Our work reveals the high degree of precision possible through etching monocrystalline silicon,” lead author Yusuke Nagasaki says. “The agreement between the calculated and experimental reflectance values for our system also supports our confidence in the robust nature of the technique we created.”
The dual-color properties of the pixels offer the potential to create overlaid images, as well as maximizing the information encoded into a particular area of the array. The work shows potential for use in anti-counterfeiting technology and advanced display technology such as three-dimensional displays.
Naturally, we always handle your personal data responsibly. Any personal data we receive from you is processed in accordance with applicable data protection legislation. For detailed information please see our privacy policy.
Consent to the use of data for promotional purposes
I hereby consent to Vogel Communications Group GmbH & Co. KG, Max-Planckstr. 7-9, 97082 Würzburg including any affiliated companies according to §§ 15 et seq. AktG (hereafter: Vogel Communications Group) using my e-mail address to send editorial newsletters. A list of all affiliated companies can be found here
Newsletter content may include all products and services of any companies mentioned above, including for example specialist journals and books, events and fairs as well as event-related products and services, print and digital media offers and services such as additional (editorial) newsletters, raffles, lead campaigns, market research both online and offline, specialist webportals and e-learning offers. In case my personal telephone number has also been collected, it may be used for offers of aforementioned products, for services of the companies mentioned above, and market research purposes.
In case I access protected data on Internet portals of Vogel Communications Group including any affiliated companies according to §§ 15 et seq. AktG, I need to provide further data in order to register for the access to such content. In return for this free access to editorial content, my data may be used in accordance with this consent for the purposes stated here.
Right of revocation
I understand that I can revoke my consent at will. My revocation does not change the lawfulness of data processing that was conducted based on my consent leading up to my revocation. One option to declare my revocation is to use the contact form found at https://support.vogel.de. In case I no longer wish to receive certain newsletters, I have subscribed to, I can also click on the unsubscribe link included at the end of a newsletter. Further information regarding my right of revocation and the implementation of it as well as the consequences of my revocation can be found in the data protection declaration, section editorial newsletter.