Home > Press > Dielectric film has refractive index close to air
By manipulating the structure of aluminum oxide, a dielectric material, researchers were able to improve its optical and mechanical properties. The key to the film's performance is the highly-ordered spacing of the pores, which gives it a more mechanically robust structure without impairing the refractive index. You can see the structure here, on the micrometer scale. CREDIT: Chih-Hao Chang |
Abstract:
“Ordered Three-Dimensional Thin-Shell Nanolattice Materials with Near-Unity Refractive Indices”
Authors: Xu A. Zhang, Abhijeet Bagal, Erinn C. Dandley, Junjie Zhao, Chrisopher J. Oldham, Gregory N. Parsons and Chih-Hao Chang, North Carolina State University; Bae-Ian Wu, Air Force Research Laboratory
Published: Oct. 12, Advanced Functional Materials
DOI: 10.1002/adfm.201502854
Abstract: The refractive indices of naturally occurring materials are limited, and there exists an index gap between indices of air and available solid materials. With many photonics and electronics applications, there has been considerable effort in creating artificial materials with optical and dielectric properties similar to air while simultaneously being mechanically stable to bear load. Here we demonstrate a class of ordered nanolattice materials consisting of periodic thin-shell structures with near-unity refractive index and high stiffness. Using a combination of three-dimensional nanolithography and atomic layer deposition, these ordered nanostructured material have reduced optical scattering and improved mechanical stability compared to existing randomly porous materials. Using ZnO and Al2O3 as the building materials, refractive indices from 1.3 down to 1.025 were achieved. The experimental data can be accurately described by Maxwell-Garnett effective media theory, which can provide a guide for index design. The demonstrated low-index, low-scattering, and high-stiffness materials can serve as high-quality optical films in multilayer photonic structures, waveguides, resonators, and ultra-low-k dielectrics.
Researchers from North Carolina State University have developed a dielectric film that has optical and electrical properties similar to air, but is strong enough to be incorporated into electronic and photonic devices - making them both more efficient and more mechanically stable.
At issue is something called refractive index, which measures how much light bends when it moves through a substance. Air, for example, has a refractive index of 1, while water has a refractive index of 1.33 - which is why a straw appears to bend when you put it in a glass of water.
Photonic devices require a high contrast between its component materials, with some components having a high refractive index and others have a low one. The higher the contrast between those materials, the more efficient the photonic device is - and the better it performs. Air has the lowest refractive index, but it isn't mechanically stable. And the lowest refractive index found in solid, naturally occurring materials is 1.39.
But now researchers have developed a film made of aluminum oxide that has a refractive index as low as 1.025 but that is mechanically stiff.
"By manipulating the structure of the aluminum oxide, which is dielectric, we've improved both its optical and mechanical properties," says Chih-Hao Chang, corresponding author of a paper on the work and an assistant professor of mechanical and aerospace engineering at NC State. Dielectrics are insulator materials that are used in an enormous array of consumer products. For example, every handheld device has hundreds of capacitors, which are dielectric components that can store and manage electric charge.
"The key to the film's performance is the highly-ordered spacing of the pores, which gives it a more mechanically robust structure without impairing the refractive index," says Xu Zhang, lead author of the paper and a Ph.D. student at NC State.
The researchers make the film by first using a nanolithography developed in Chang's lab to create highly-ordered pores in a polymer substrate. That porous polymer then serves as a template, which the researchers coats with a thin layer of aluminum oxide using atomic layer deposition. The polymer is then burned off, leaving behind a three-dimensional aluminum oxide coating.
"We are able to control the thickness of the aluminum oxide, creating a coating between two nanometers and 20 nanometers thick," Zhang says. "Using zinc oxide in the same process, we can create a thicker coating. And the thickness of the coating controls and allows us to design the refractive index of the film." Regardless of the how thick the coating is, the film itself is approximately one micrometer thick.
"The steps in the process are potentially scalable, and are compatible with existing chip manufacturing processes," Chang says. "Our next steps include integrating these materials into functional optical and electronic devices."
###
The paper, "Ordered Three-Dimensional Thin-Shell Nanolattice Materials with Near-Unity Refractive Indices," is published online in the journal Advanced Functional Materials. The paper was co-authored by Abhijeet Bagal, Erinn Dandley, Junjie Zhao, Chrisopher Oldham and Gregory Parsons of NC State; and by Bae-Ian Wu of the Air Force Research Laboratory.
The work was done with support from the Air Force Research Laboratory and from NASA under grant NNX12AQ46G.
####
For more information, please click here
Contacts:
Matt Shipman
919-515-6386
Copyright © North Carolina State University
If you have a comment, please Contact us.Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.
Related News Press |
News and information
Researchers develop artificial building blocks of life March 8th, 2024
Thin films
Understanding the mechanism of non-uniform formation of diamond film on tools: Paving the way to a dry process with less environmental impact March 24th, 2023
New study introduces the best graphite films: The work by Distinguished Professor Feng Ding at UNIST has been published in the October 2022 issue of Nature Nanotechnology November 4th, 2022
Thin-film, high-frequency antenna array offers new flexibility for wireless communications November 5th, 2021
Leibniz Prize winner Professor Dr. Oliver G. Schmidt moves to Chemnitz University of Technology: President Professor Dr. Gerd Strohmeier refers to an 'absolute top transfer' September 10th, 2021
Govt.-Legislation/Regulation/Funding/Policy
What heat can tell us about battery chemistry: using the Peltier effect to study lithium-ion cells March 8th, 2024
Researchers’ approach may protect quantum computers from attacks March 8th, 2024
Optically trapped quantum droplets of light can bind together to form macroscopic complexes March 8th, 2024
Chip Technology
New chip opens door to AI computing at light speed February 16th, 2024
HKUST researchers develop new integration technique for efficient coupling of III-V and silicon February 16th, 2024
NRL discovers two-dimensional waveguides February 16th, 2024
Optical computing/Photonic computing
Optically trapped quantum droplets of light can bind together to form macroscopic complexes March 8th, 2024
New chip opens door to AI computing at light speed February 16th, 2024
HKUST researchers develop new integration technique for efficient coupling of III-V and silicon February 16th, 2024
NRL discovers two-dimensional waveguides February 16th, 2024
Discoveries
What heat can tell us about battery chemistry: using the Peltier effect to study lithium-ion cells March 8th, 2024
Researchers’ approach may protect quantum computers from attacks March 8th, 2024
High-tech 'paint' could spare patients repeated surgeries March 8th, 2024
Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024
Materials/Metamaterials/Magnetoresistance
Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024
Focused ion beam technology: A single tool for a wide range of applications January 12th, 2024
Announcements
What heat can tell us about battery chemistry: using the Peltier effect to study lithium-ion cells March 8th, 2024
Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024
Interviews/Book Reviews/Essays/Reports/Podcasts/Journals/White papers/Posters
Researchers develop artificial building blocks of life March 8th, 2024
Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024
Military
What heat can tell us about battery chemistry: using the Peltier effect to study lithium-ion cells March 8th, 2024
New chip opens door to AI computing at light speed February 16th, 2024
NRL discovers two-dimensional waveguides February 16th, 2024
Aerospace/Space
Under pressure - space exploration in our time: Advancing space exploration through diverse collaborations and ethical policies February 16th, 2024
Bridging light and electrons January 12th, 2024
Manufacturing advances bring material back in vogue January 20th, 2023
Photonics/Optics/Lasers
Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024
Optically trapped quantum droplets of light can bind together to form macroscopic complexes March 8th, 2024
HKUST researchers develop new integration technique for efficient coupling of III-V and silicon February 16th, 2024
A battery’s hopping ions remember where they’ve been: Seen in atomic detail, the seemingly smooth flow of ions through a battery’s electrolyte is surprisingly complicated February 16th, 2024
The latest news from around the world, FREE | ||
Premium Products | ||
Only the news you want to read!
Learn More |
||
Full-service, expert consulting
Learn More |
||