Quantitative measurements

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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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. forces are acting at the Nanoscale on MEMS and
on NEMS
ltlt1mm
Courtesy of Hubert GRANGE and Marie-Thérèse
DELAYE (2004) CEA LETI
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Nature of forces at Nanoscale Photonic Radiati
on pressure van der Waals interaction Casimir
effect Electrostatic Brownian Motion (kBT) Hard
core repulsion Adhesion-metallic
bonding Dissipation
MEMS Parameters atmosphere-vacuum surface roughn
ess chemical nature nanostructuration restoring
force (mechanical spring constant) surface/bulk
elastic stress
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When micromechanics and quantum electrodynamics
meet MEMS based on Casimir-Lifschitz
forces Federico Capasso
FCas 3pN
L1000nm1mm A50mmx50mm
Strong gradient ?F?L5 gt K mechanical instability
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Radius of interaction R 50mm no longer
local no microscopy
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Origin electron-photon coupling
Characteristic length plasma length
l p ? 100nm
l p 2p c/ w p
Aluminum ?w p 14eV

• L gtgt l p retarded régime (Casimir régime)
  
• electron coupling to propagating photon modes
  dominant
• L ltlt l p NON retarded régime (Van der
  Waals)
• electron coupling to NON propagating photon modes
  dominant
• surface plasmon-photon coupling

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Large distance limit and perfect mirror Casimir
limit Lgtgtl p
Radiation pressure of virtual photons i.e. zero
point motion of ElectroMagnetic field
L100nm (retarded régime L? /gtl p ) F100
picoN ?F 10-3 N/m
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L10nm (non retarded van der Waals régime Lltlt l
p ) F H R/ L2 H5x 10-19 Joule F500
nanoNewton ?F 50 N/m
d
J.J. Greffet EM2C Ecole Centrale de Paris 2003
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Measure (G. Torricelli PhD thesis LEPES
2001-2004)Omicron VT UHV AFM
polystyrene sphere R 42 mm metal coating (gold)
300 nm
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Static cantilever deflection F -kx
Sphere/surface distance determination Cantilever
spring constant measurement
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Dzdef
z
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Vdw/ Casimir Oscillating mode of the sphere at
resonance
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Short distances Dltltlp with lp plasmon length,
Tuning fork K 1000 - 10000 N/m
Force machine sphere-surface distance 10nm
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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