Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Chemists advance clear conductive films

08.08.2012
Thin, conductive films are useful in displays and solar cells. A new solution-based chemistry developed at Brown University for making indium tin oxide films could allow engineers to employ a much simpler and cheaper manufacturing process.

In a touch-screen display or a solar panel, any conductive overlay had better be clear. Engineers employ transparent thin films of indium tin oxide (ITO) for the job, but a high-tech material’s properties are only half its resume. They must also be as cheap and easy to manufacture as possible. In a new study, researchers from Brown University and ATMI Inc. report the best-ever transparency and conductivity performance for an ITO made using a chemical solution, which is potentially the facile, low-cost method manufacturers want.


Efficient manufacture and optimized conductivity
Electron microscopy (cross-section, left, and facing view) shows an even distribution of indium titanium oxide nanocrystals essential for a highly conductive, transparent thin film. Credit: Sun Lab/Brown University

“Our technology is already at the performance level for application in resistive touch screens,” said Jonghun Lee, a Brown chemistry graduate student and lead author of the paper posted online Aug. 1 by the Journal of the American Chemical Society.

The group made conductive ITO films 146 billionths of a meter thick that allowed 93 percent of light to pass through, a transparency comparable to the glass plates they were deposited on. The team also made their films on top of bendable polyimide, showing that it could potentially be useful for making flexible display technologies.

In several experiments they showed that by varying the thickness and the tin content (between 5 and 10 percent was best) they could vary the transparency and resistance to find the best combination.

“By controlling the concentration of the nanocrystal solution, we could control the thickness of the film from 30 nanometers to 140 nanometers,” Lee said.

The solution

To make the films, the team synthesized nanoscale ITO crystals in a solution. Then they made a flat and smooth film of them by dripping the solution onto a glass plate followed by rapid spinning, a process called spin casting. From there they baked, or annealed, the coated plates for several hours (the best length of time turned out to be six hours) and then tested their transparency and conductivity.

Spin casting is simple as high-tech manufacturing processes go, but finding the chemistry that allows spin casting to produce a high-performance ITO thin film has proven elusive. A key achievement described in the new paper, was finding the materials needed to make the nanoscale ITO crystals in the first place, said Shouheng Sun, professor of chemistry at Brown and the study’s corresponding author.

The best chemicals turned out to be indium acetylacetonate and tin bis(acetylacetonate)dichloride. They synthesized ITO nanocrystals that had a narrow range of sizes, about 11 billionths of a meter in diameter. That consistency meant that when the crystals arranged themselves in the thin films, they neither bunched together in clumps, nor stayed too far apart. The result was a dense but evenly distributed array of crystals, which promotes conductivity.

“If the particle clumps, then you cannot get uniform assembly and you can’t get good conductivity,” Sun said.

This discovery was critical for achieving the high-level performance detailed in the paper, but the team knows it still needs to build on that progress — for instance, to match the conductivity performance of films made by a process called sputtering.

“The next step is to improve conductivity to a magnitude commensurate with sputtered ITO while realizing the reduced cost and process efficiency benefits expected of a solution-based ITO deposition method,” said Melissa Petruska, senior scientist at ATMI and co-author of the paper.

In new experiments, therefore, the team plans to further drive down electrical resistance, to reduce the length of time the films need to anneal, and to lay down fine patterns of their films, rather than continuous sheets, using inkjet or roll-to-roll printing.

In addition to Sun and Lee, the other Brown authors are Sunghwan Lee, Guanglai Li and David Paine.

ATMI provided project funding and engineering assistance for the research.

Editors: Brown University has a fiber link television studio available for domestic and international live and taped interviews, and maintains an ISDN line for radio interviews. For more information, call (401) 863-2476.

David Orenstein | EurekAlert!
Further information:
http://www.brown.edu

More articles from Life Sciences:

nachricht One step closer to reality
20.04.2018 | Max-Planck-Institut für Entwicklungsbiologie

nachricht The dark side of cichlid fish: from cannibal to caregiver
20.04.2018 | Veterinärmedizinische Universität Wien

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

Im Focus: Basel researchers succeed in cultivating cartilage from stem cells

Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.

Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...

Im Focus: Like a wedge in a hinge

Researchers lay groundwork to tailor drugs for new targets in cancer therapy

In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Magnetic nano-imaging on a table top

20.04.2018 | Physics and Astronomy

Start of work for the world's largest electric truck

20.04.2018 | Interdisciplinary Research

Atoms may hum a tune from grand cosmic symphony

20.04.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>