Researchers at TU Delft’s Kavli Institute of Nanoscience and colleagues at the NTT Basic Research Laboratories in Japan have used a new method to successfully measure vibrations smaller than an atom’s nucleus. This result is important to the development of ultra-small sensors. Their findings have been published in the Nature Physics journal.

An airbag sensor is one of the many examples of what are known as micro-electromechanical systems (MEMS). These systems react to electrical and mechanical stimuli such as making a super-small beam – known as the resonator (R) – oscillate.
Researchers around the world are working on developing even smaller systems: nano-electromechanical systems (NEMS). Their tiny dimensions mean that NEMS can, for instance, easily be integrated into chips.

Absolute zero
At low temperatures quantum mechanical effects start to play a dominant role in the resonator’s vibration behaviour.
Atoms are constantly oscillating due to their temperature. At high temperatures, these vibrations dominate the quantum mechanical effects, but at sufficiently low temperatures the latter become relevant. By cooling the NEMS to near absolute zero, it is possible to observe the tiny vibrations which are not caused by the temperature but which are quantum mechanical in nature.

Femtometer
Researchers at TU Delft’s Kavli Institute of Nanoscience and colleagues at NTT Basic Research Laboratories in Japan have succeeded in measuring their resonator’s oscillations at a temperature of several hundredths of a degree above absolute zero.  With the aid of a super-conducting circuit they were able to observe a movement by the resonator of less than 10 femtometer (a femtometer is a millionth of a nanometer). The measured movement is smaller than the size of an atom nucleus.
‘I still think it is almost unbelievable that you can measure such tiny movements,’ says project leader Prof. Herre van der Zant. He believes that further improvements can be achieved by altering the design of their system and measuring technique.

Editorial note
For more information:
Prof.dr.ir. Herre van der Zant, e-mail H.S.J.vanderZant@tudelft.nl, telephone +31 - 15 - 278 77 33
Frank Nuijens, science information officer, e-mail F.W.Nuijens@tudelft.nl, telephone +31 - 15 - 278 42 59