Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Taking Thin Films to the Extreme

01.10.2014

Layering rough surfaces with nanometer-thin optical interference coatings opens new array of possible applications, such as nearly weight-free logos on the sides of spacecraft

Applying a well-known optical phenomenon called thin-film interference, a group of researchers at Harvard University has demonstrated the ability to "paint" ultra-thin coatings onto a rough surface -- work that holds promise for making future, flexible electronic devices, creating advanced solar cells and detailing the sides of next-gen rocket ships and spacecraft with extremely lightweight decorative logos.


M. Kats / Harvard

Gold-coated notebook paper pieces with ultra-thin germanium films of different thickness deposited on top

When light passes through oil in water, it becomes iridescent, revealing a myriad of colors that glisten and shift along with your perspective. This behavior, known as thin-film interference, is well-studied and is implemented in creating all manner of optical devices. Recently, the Harvard team demonstrated that this behavior can persist when patterned on extremely rough and flexible surfaces.

“Normally when you think of thin-film interference, you think of smooth substrates,” said Mikhail Kats, a postdoctoral fellow at Harvard University working in the lab of Federico Capasso. He and Capasso describe their work in the journal Applied Physics Letters, from AIP Publishing. “With increasing roughness the effect is expected to fade and you just don’t get this coherent behavior.”

Optically speaking, notebook paper is at the far end of the roughness spectrum, owing to its fibrous composition. However, after the researchers deposited onto paper an initial layer of gold and a subsequent layer of germanium, the paper began to display interference. The optical trickery lies in the influence of the film’s angle of incidence.

Traditionally, thin films needed to be transparent and no thinner than roughly one-quarter of the wavelength of light – 600 nm – to exhibit interference colors.

This is due to the phase shifts, or changes in optical path length, which occur as a result of changes in the observer’s angle of incidence. The path length directly corresponds to which colors appear to an observer - tilt your head and they change slightly.

At the nanometer scale, however, the amount of phase shift that occurs is greatly diminished due to the significantly smaller thickness of the films, resulting in a decrease in the angle of incidence’s effect. Tilt your head now, and the colors remain unchanged.

“You can use this effect to essentially see atomic monolayers, bilayers or tri-layers with your naked eye,” Kats said.

This would allow for the coloring of metallic objects by use of far less material than with traditional paint – a claim confirmed by the orange, indigo, and violet hues visible from the 7, 10 and 15 nm layered sheets of paper.

“There’s a famous story where, by not painting the space shuttle’s fuel tank, 600 pounds were saved, because that’s how much the paint weighed,” Kats said. “If you wanted to put a logo on something that you’re sending up in space, or you wanted to color it, here you could do it without almost any increase in weight.”

Future applications of the films include making extremely thin, flexible photodetectors and optoelectronic devices, including solar cells.

“I don’t think a solar cell made out of these materials is going to break any efficiency records, but we might demonstrate one that uses 1/10th-1/100th of the material of a conventional cell,” Kats said. “And that’s still an interesting parameter to explore when it comes to cost.”

The article, "Ultra-thin optical interference coatings on rough and flexible substrates" is authored by Mikhail A. Kats and Federico Capasso. It will appear in the journal Applied Physics Letters on September 30, 2014. After that date, it can be accessed at:
http://scitation.aip.org/content/aip/journal/apl/105/13/10.1063/1.4896527

ABOUT THE JOURNAL
Applied Physics Letters features concise, rapid reports on significant new findings in applied physics. The journal covers new experimental and theoretical research on applications of physics phenomena related to all branches of science, engineering, and modern technology. See: http://apl.aip.org

Jason Bardi | newswise

More articles from Physics and Astronomy:

nachricht Engineering team images tiny quasicrystals as they form
18.08.2017 | Cornell University

nachricht Astrophysicists explain the mysterious behavior of cosmic rays
18.08.2017 | Moscow Institute of Physics and Technology

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>