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Dynamic electromechanical control of semiconductor nanostructures by acoustic fields

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A novel training network is making waves with tiny quakes on chips

‘Nanoquakes’ can be generated on chips manufactured with semiconductor technology when piezoelectric materials are used – an alternating electrical voltage gets things moving. An innovative training network has harnessed nanoquakes for new applications in fields from quantum nanotechnology to microchemistry.

Industrial Technologies

In the late 19th century, Nobel-winning physicist Lord Rayleigh predicted the existence of a special type of wave. Rolling over the elastic surface of the Earth, Rayleigh waves are responsible for the power of an earthquake. Shrink them to the nanoscale and put them on a chip and you have today’s surface acoustic waves (SAWs). With the support of the Marie Skłodowska-Curie programme, the SAWTrain project created an innovative training network focused on controlling semiconductor nanostructures with SAWs. The team set out to alter electrical and optical properties with nanoquakes to create new functionalities.

Tiny acoustic waves with mega impact

Project coordinator Hubert Krenner and his team targeted next-generation applications in information technology while creating completely new areas of application. According to Krenner, “The main application of SAWs is signal processing at gigahertz (GHz) frequencies. Today, all wireless communication operates at these frequencies. Another important application is microfluidics, processing the tiniest amounts of liquids on a chip. In these thumbnail-sized lab-on-a-chips, the nanoquakes are used for actuating and stirring tiny droplets to dramatically speed up medical tests.” The team focused on SAWs in quantum nanotechnologies, optical nanosystems, sensors with unprecedented sensitivity or to speed up chemical reactions.

Nanoquakes really shake things up

SAWTrain has been a very fruitful scientific endeavour. Early stage researchers (ESRs) have published their work in numerous high-impact journals including Nature Physics, Physical Review X, and Nature Communications. In addition, two letters on important new findings have appeared in Applied Physics Letters and the Journal of Physics D. SAWTrain provided the impetus behind the Special Issue on Surface Acoustic Waves in Semiconductor Nanosystems in the prestigious Journal of Physics D: Applied Physics. SAWTrain project coordinator Hubert Krenner and PIs Paulo Santos and Mauricio de Lima were the guest editors. Krenner explains with enthusiasm, “Nine of the 25 contributions were co-authored by SAWTrain ESRs. SAWTrain became a ‘brand name’ for SAWs in Europe and, together with our students and stellar colleagues from all over the world, we developed visions on how our field may evolve, collected in the 2019 SAW roadmap.”

Impact beyond scientific contributions

The ESRs took the lead in many ways. “The fellows themselves did a fantastic job organising and conducting networking and training events all on their own. Because of the great success, we doubled the budget to support these unique activities that develop soft and transferrable skills critical to their future careers,” Krenner says. SAWTrain also implemented an extensive outreach and dissemination campaign largely in association with Deutsches Museum in Munich, one of the world’s largest science and technology museums. For instance, the team developed and built a demonstrator to bring SAW technology to the public that was showcased in open lab days and science festivals such as the European Researchers' Night 2018. The first SAWTrain graduate completed his PhD with highest honours in February 2019 and has already received a Marie Skłodowska-Curie Action (MCSA) Individual Fellowship as a postdoctoral researcher to continue his work. Clearly, the SAWTrain project may not have been the main quake but only a foreshock, with the biggest events and impact yet to come.

Keywords

SAWTrain, surface acoustic waves (SAWs), nanoquakes, waves, semiconductor, training, nanosystems, quantum, nanotechnologies, sensors, microfluidics, lab-on-a-chip

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