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Published byIsabel Wentworth Modified over 5 years ago

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Quantitative measurements of non contact interaction G. Torricelli, M. Rodrigues, C. Alandi, M.Stark, F. Comin J. Chevrier Université Joseph Fourier Grenoble LEPES CNRS Grenoble Spectro CNRS UJF ESRF Grenoble Coll. S. Huant, F. Martins Spectro Coll. G. Jourdan, A Lambrecht, S Reynaud LKB

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<<1 m Courtesy of Hubert GRANGE and Marie-Thérèse DELAYE (2004) CEA LETI …. forces are acting at the Nanoscale on MEMS and on NEMS

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Nature of forces at Nanoscale: Photonic Radiation pressure van der Waals interaction Casimir effect Electrostatic Brownian Motion (k B T) Hard core repulsion Adhesion-metallic bonding Dissipation MEMS Parameters: atmosphere-vacuum surface roughness chemical nature nanostructuration restoring force (mechanical spring constant) surface/bulk elastic stress

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L=1000nm=1 m A=50 mx50 m F Cas = 3pN Strong gradient: F L 5 > K mechanical instability When micromechanics and quantum electrodynamics meet: MEMS based on Casimir-Lifschitz forces Federico Capasso

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Radius of interaction R= 50 m no longer local no microscopy surface R tip Z

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L >> p retarded régime (Casimir régime) electron coupling to propagating photon modes dominant L << p NON retarded régime (Van der Waals) electron coupling to NON propagating photon modes dominant: surface plasmon-photon coupling p = 2 c/ p Characteristic length:plasma length Aluminum ћ p = 14eV p 100nm Origin: electron-photon coupling

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L=100nm (retarded régime L /> p ) F=100 picoN F =10 -3 N/m Large distance limit and perfect mirror Casimir limit L>> p Radiation pressure of virtual photons i.e. zero point motion of ElectroMagnetic field

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x Hy EE z +++ --- +++ --- +++ --- metal ( 1 <0) +++ --- +++ --- +++ --- metal ( 2 <0) d L=10nm (non retarded van der Waals régime L<< p ) F= H R/ L 2 H=5x 10 -19 Joule F=500 nanoNewton F =50 N/m J.J. Greffet EM2C Ecole Centrale de Paris 2003

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polystyrene sphere R= 42 m metal coating (gold) =300 nm Measure (G. Torricelli PhD thesis LEPES 2001-2004) Omicron VT UHV AFM 100nm < z < 500nm V

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Sphere/surface distance determination Cantilever spring constant measurement Static cantilever deflection F= -kx

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Cantilever deflection cannot be neglected at large voltage z z def

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Vdw/ Casimir: Oscillating mode of the sphere at resonance V F res

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Casimir/vdw interaction (fit in z -3 ) 86.4 m K 88.6N/m Z 0.05 - 0.4 m Electrostatic long range interaction V=0.5volt (fit in z -2 ) f res =52.670 kHz L=50nm grad F= 10 -1 N/m p 130nm

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Short distances: D<< p with p plasmon length, Force machine: sphere-surface distance 10nm Tuning fork K= 1000 - 10000 N/m

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Full scale is 0.3Hz The distance is again determined using capacitive interaction

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Large surface roughness at the origin of our measurement no van der Waals contribution, instead direct metallic bonding

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At nanoscale, attractive force between 2 metallic plates in vacuum

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