Producing technicolor through brain-like electronic devices

Date:
September 8, 2020
Source:
Pohang University of Science & Technology (POSTECH)
Summary:
Structural coloration is promised to be the display technology
of the future as there is no fading - it does not use dyes -
and enables low- power displays without strong external light
source. However, the disadvantage of this technique is that once a
device is made, it is impossible to change its properties so the
reproducible colors remain fixed. Recently, a research team has
successfully obtained vivid colors by using semiconductor chips -
not dyes - made by mimicking the human brain structure.



FULL STORY ========================================================================== Structural coloration is promised to be the display technology of the
future as there is no fading -- it does not use dyes -- and enables
low-power displays without strong external light source. However, the disadvantage of this technique is that once a device is made, it is
impossible to change its properties so the reproducible colors remain
fixed. Recently, a POSTECH research team has successfully obtained vivid
colors by using semiconductor chips -- not dyes -- made by mimicking
the human brain structure.


========================================================================== POSTECH's joint research team consisting of Professor Junsuk Rho of
the mechanical engineering and chemical engineering departments, Inki
Kim, a mechanical engineering student in the MS/PhD integrated program,
along with Professor Yoonyoung Jung and masters student Juyoung Yun of
the Department of Electrical Engineering developed a technology that can
freely change the structural colors using IGZO(Indium-Galium-Zinc-Oxide),
a type of oxide semiconductor. IGZO is a material that is widely used
not only in flexible displays but also in neuromorphic electronic
devices. This is the first study that incorporates IGZO to nanoptics.

IGZO can freely control the charge concentration within a layer through
the hydrogen plasma treatment process, thereby controlling the refractive
index in all ranges of visible light. In addition, nanoptical simulations
and experiments have confirmed that the extinction coefficient of
visible light is close to zero, thus enabling the actualization of a transmittable color filter in the penetrable form that can transmit exceptionally clear colors with extremely low light loss.

The IGZO-based color filter technology developed by the research team
consists of a 4-layer (Ag-IGZO-SiO2-Ag) multilayer and can transmit
vivid colors using the Fabry-Perot resonance3 properties. Experiments
have confirmed that as the charge concentration of IGZO layer increases,
the refractive index decreases which can change the resonance properties
of light that is selectively transmitted.

This design method can be applied not only to color filters for
large-scale displays, but also to color printing technique of micro
(11-6, millionth) or nano (10-9, billionth) sizes.

To verify this, the research team demonstrated a color printing technology
that has a pixel size of one micrometer (mm, one millionth of a meter).

The results proved that the colors from the centimeter or micrometer-sized color pixels can be adjusted freely depending on the charge concentration
of the IGZO layer. It was also confirmed that the structural color can be changed more reliably and quickly through changing the refractive index
via charge concentration compared to other conventional all solid-state variable materials like WO3 or GdOx.

"This research is the very first application of IGZO to nanoptical
structural color display technology. IGZO is the next-generation oxide semiconductor used in flexible displays and neuromorphic electronic
devices," stated Professor Rho who led the research. He added,
"It is anticipated that this technology, which enables filtering the transmitted light by adjusting the charge concentration, can be applied
to the next-generation low-power reflective display and anti- tamper
display technologies." This study was conducted with the support from
the Samsung Research Funding & Incubation Center for Future Technology.


========================================================================== Story Source: Materials provided by Pohang_University_of_Science_&_Technology_(POSTECH).

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Inki Kim, Juyoung Yun, Trevon Badloe, Hyuk Park, Taewon Seo,
Younghwan
Yang, Juhoon Kim, Yoonyoung Chung, Junsuk Rho. Structural
color switching with a doped indium-gallium-zinc-oxide
semiconductor. Photonics Research, 2020; 8 (9): 1409 DOI:
10.1364/PRJ.395749 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200908101616.htm

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