Access success story - LP3

Periodic porous membranes produced by intense lasers (LP3)

Researchers from the Italian National Research Institute (INRIM, Torino, Italy) used the unique laser facilities at LASERLAB-EUROPE partner LP3 (Marseille, France) to create tiny holes in thin layers of silica. A chance encounter at a conference led to a new method to produce periodic porous membranes for nanofabrication.

In 2010, Luca Boarino and Natascia De Leo from INRIM participated in an international nanoscience conference (NANOSEA) held in Cassis, France. They presented a poster just next to another poster presented by researchers from LP3. The topic of the conference was ‘self-assembled ordered nanomaterials’ and the researchers realized during this poster session that, combining their approaches, they could produce very efficiently periodic porous membranes – a key element for nanofabrication protocols.

The Italians were working on methods to fabricate devices on nano- and microscale from silica microspheres. They had a very large set of technological resources at their disposal, but no intense lasers. At the conference, they devised detailed methods to combine microsphere synthesis and near-field laser ablation to fabricate so-called mesoporous membranes (containing holes with a diameter of 2 to 50 nanometers). The scientists realized that the possibility to perform laser experiments with specially engineered micro- or nanospheres should provide a unique opportunity to study microsphere near-field laser ablation processes in detail.

After the conference, the INRIM researchers applied for Transnational Access, describing in their proposal the concept they discussed with the LP3 researchers. The proposal was accepted and after just two few-day visits at the LP3 laboratory, they were able to demonstrate that their concept holds.

In their experiments, they prepare silica nanospheres and assemble them into monolayers. Subsequently, a laser beam hits the monolayer deposited on top of the dense silica membranes. The laser interaction with the nanospheres creates extremely small and intense light spots, leading to a periodic nano-ablation of the membranes. Then, the approach fabricates beautifully ordered mesoporous membranes with the use of a single nanosecond laser pulse.

The LP3 laser facilities are unique, because the researchers can find all the equipment to prepare substrates (surface preparation), to irradiate the substrate (intense pulsed lasers) and to characterize directly the modified materials (optical, electron and atomic force microscopes) in one place. Thanks to all this equipment, the nanoscale experiments are not performed in the blind, which saves a lot of time. After the access experiments, further detailed characterization took place using the world-class nanoscale metrology facilities at INRIM and the results were published in Nanotechnology.

The Italian-French consortium will continue their research on this hybrid-photonic approach, which appears extremely promising because it is dry, clean and fast but also extremely flexible thanks to the use of laser ablation. The researchers plan to push their concept further with the help of another access project this year.

 Luca Boarino

Luca Boarino characterizing the laser-fabricated nanoporous materials at ‘Nanofacility Piemonte’

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