Every object at finite temperature is submitted to a thermal agitation. The movements induced by such thermal agitation are generally negligible at the macroscopic scale ; however they can dominate and control the behaviours of objects at the nanoscales. Further, this “thermal noise” appears as the main limitation for a great number of ultra-‐ sensitive measurements such as high
resolution imaging, integrated force sensors, mass spectrometry or even time measurement and triggering.
A. Niguès and A. Siria at the Laboratoire de Physique Statistique, in collaboration with Pierre Verlot at the Institut Lumiere et Matiere in Lyon, has recently been able to cool down the thermal agitation of a nano-‐object by using an electron beam.
By exposing a nanowire to a highly focused electron beam , the authors have been able to reduce the object thermal vibration of more than an order of magnitude. This result has been published in the journal Nature Communications.
Figure 1 : Control of the thermal vibration with an electron beam. a) Schema of the experimental set-‐up. b)
SEM picture of the nanowire under study
To realize the study, the authors have chosen a nanometric wire made of Silicon Carbide, glued at the extremity of tip. Everything has been put inside a Scanning Electron
Microscope, delivering a highly focused electron beam. The displacement of the nanowire respect with the electron beam induces a modulation of the signal measured by the microscope detector.
Using this experimental set-‐up, the authors have been able to measure a displacement with a resolution in the order of the picometer (i.e. one tenth of one atom).
Further the authors have been able to show that the interaction between the electron beam and the matter of the nano-‐object can modify the thermal vibration of the nanowire. When the
nanowire departs from the equilibrium position because of the thermal noise, it “enters” within the electron beam. The nanowire absorbs a part of the electron beam and as a consequence it contracts to come back to the equilibrium position. This mechanism is very general and could be applied to a
vast number of nan-‐ objects, paving the way to new functionalises in the field of nano-‐imaging and nano-‐ engeneering.
« Dynamical Backaction Cooling with Free Electrons »,
A. Niguès, A. Siria, P. Verlot, Nature Communications 2015
Retrouvez la publication sur http://www.nature.com/ncomms/index.html