Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Plasmonics: Minimizing loss by thinning and smoothing


A gas cluster ion beam smoothing produces ultrathin silver films and lithographically patterned structures to enhance plasmonic performance.

Plasmonic devices — such as superlenses, hyperlenses and plasmonic waveguides — have exciting potential for research and commercial applications because they permit optical lithography, imaging and waveguiding to be performed at resolutions below the diffraction limit of light.

The smoothing effect of a gas cluster ion beam (purple) on a rough surface (gray).

Copyright : 2014 A*STAR Institute of Materials Research and Engineering

These devices often require low-loss ultrathin metal films, which are difficult to fabricate using current deposition techniques. Researchers have investigated processes such as seed layer deposition and thermal annealing to reduce the surface roughness and grain-boundary density of these films. To date, however, these processes have not been hugely successful.

Now, Ee Jin Teo and colleagues at the A*STAR Institute of Materials Research and Engineering, Singapore, the University of Hyogo, Japan, and the National University of Singapore have used gas cluster ion beam (GCIB) processing to smooth ultrathin metal films and thereby enhance their properties(1).

A GCIB consists of thousands of gas molecules that are weakly bound by van der Waals forces. Such a beam is able to smooth out surface irregularities and reduce film thickness with nanometer precision. This processing significantly enhances surface plasmon resonance and propagation, and enables the fabrication of ultrathin films with extremely low electrical resistivity and optical loss.

Unlike monomer ion beams used in conventional ion-beam milling and plasma etching, a cluster of nitrogen gas molecules with an energy of 20 kiloelectron volts impinging on a silver film can deliver a high energy density to a relatively small volume: yet the cluster penetrates to a depth of only a few nanometers.

The impact of the beam on the film causes silver atoms in surface peaks to scatter sideways towards valleys, voids and grain boundaries. As well as producing a smoother surface, this processing triples the grain width through the redeposition of atoms at grain boundaries.

The team’s GCIB treatment resulted in up to a four-fold improvement in the electrical and optical properties of films of a thickness of 12 nanometers. “The unique characteristics of GCIB irradiation meant that in a single irradiation step we could reduce scattering losses due to surface roughness, grain boundaries and voids,” notes Teo.

The research team also used the technique to smooth the top surface and sidewalls of lithographically patterned silver-stripe waveguides, increasing the propagation lengths of surface plasmons in these waveguides.

“In the future, we intend to use this technique to improve the colour purity of plasmonic color filters or reflectors, and also to increase the patterned area of superlens nanolithography,” says Teo. “Such developments will bring plasmonic research a step closer to commercialization.”


1. Teo, E. J., Toyoda, N., Yang, C., Wang, B., Zhang, N. et al. Sub-30 nm thick plasmonic films and structures with ultralow loss. Nanoscale 6, 3243–3249 (2014). 

Associated links

Lee Swee Heng | Research SEA News
Further information:

More articles from Materials Sciences:

nachricht The route to high temperature superconductivity goes through the flat land
23.11.2015 | Aalto University

nachricht Quantum spin could create unstoppable, one-dimensional electron waves
19.11.2015 | DOE/Brookhaven National Laboratory

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Lactate for Brain Energy

Nerve cells cover their high energy demand with glucose and lactate. Scientists of the University of Zurich now provide new support for this. They show for the first time in the intact mouse brain evidence for an exchange of lactate between different brain cells. With this study they were able to confirm a 20-year old hypothesis.

In comparison to other organs, the human brain has the highest energy requirements. The supply of energy for nerve cells and the particular role of lactic acid...

Im Focus: Laser process simulation available as app for first time

In laser material processing, the simulation of processes has made great strides over the past few years. Today, the software can predict relatively well what will happen on the workpiece. Unfortunately, it is also highly complex and requires a lot of computing time. Thanks to clever simplification, experts from Fraunhofer ILT are now able to offer the first-ever simulation software that calculates processes in real time and also runs on tablet computers and smartphones. The fast software enables users to do without expensive experiments and to find optimum process parameters even more effectively.

Before now, the reliable simulation of laser processes was a job for experts. Armed with sophisticated software packages and after many hours on computer...

Im Focus: Quantum Simulation: A Better Understanding of Magnetism

Heidelberg physicists use ultracold atoms to imitate the behaviour of electrons in a solid

Researchers at Heidelberg University have devised a new way to study the phenomenon of magnetism. Using ultracold atoms at near absolute zero, they prepared a...

Im Focus: Climate Change: Warm water is mixing up life in the Arctic

AWI researchers’ unique 15-year observation series reveals how sensitive marine ecosystems in polar regions are to change

The warming of arctic waters in the wake of climate change is likely to produce radical changes in the marine habitats of the High North. This is indicated by...

Im Focus: Nanocarriers may carry new hope for brain cancer therapy

Berkeley Lab researchers develop nanoparticles that can carry therapeutics across the brain blood barrier

Glioblastoma multiforme, a cancer of the brain also known as "octopus tumors" because of the manner in which the cancer cells extend their tendrils into...

All Focus news of the innovation-report >>>



Event News

Fraunhofer’s Urban Futures Conference: 2 days in the city of the future

25.11.2015 | Event News

Gluten oder nicht Gluten? Überempfindlichkeit auf Weizen kann unterschiedliche Ursachen haben

17.11.2015 | Event News

Art Collection Deutsche Börse zeigt Ausstellung „Traces of Disorder“

21.10.2015 | Event News

Latest News

Fraunhofer’s Urban Futures Conference: 2 days in the city of the future

25.11.2015 | Event News

NASA's Operation IceBridge completes twin polar campaigns

25.11.2015 | Earth Sciences

NASA plans twin sounding rocket launches over Norway this winter

25.11.2015 | Physics and Astronomy

More VideoLinks >>>