Post on 26-Mar-2015
transcript
Quantitative measurements of
non contact interaction
G. Torricelli, M. Rodrigues, C. Alandi, M.Stark, F. CominJ. Chevrier Université Joseph Fourier GrenobleLEPES CNRS GrenobleSpectro CNRS UJFESRF Grenoble
Coll. S. Huant, F. Martins SpectroColl. G. Jourdan, A Lambrecht, S Reynaud LKB
<<1m
Courtesy of Hubert GRANGE and Marie-Thérèse DELAYE (2004)
CEA LETI
…. forces are acting at the Nanoscale on MEMS and on NEMS
Nature of forces at Nanoscale:
PhotonicRadiation pressurevan der Waals interactionCasimir effect
ElectrostaticBrownian Motion (kBT)Hard core repulsionAdhesion-metallic bondingDissipation
MEMS Parameters:atmosphere-vacuumsurface
roughnesschemical naturenanostructuration
restoring force (mechanical spring constant)surface/bulk elastic stress
L=1000nm=1m
A=50mx50m
FCas= 3pN
Strong gradient: FL5 > K
mechanical instability
When micromechanics and quantum electrodynamics meet:MEMS based on Casimir-Lifschitz forces
Federico Capasso
Radius of interaction R= 50m
no longer local
no microscopy
surface
R
tip
Z
• 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 ћp= 14eV
p 100nm
Origin: electron-photon coupling
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 photonsi.e. zero point motion of ElectroMagnetic field
x
Hy
EEz
+++ --- +++ --- +++ ---metal (1<0)
+++ --- +++ --- +++ --- metal (2<0)
d
L=10nm (non retarded van der Waals régime L<< p )
F= H R/ L2 H=5x 10-19 Joule
F=500 nanoNewton
F =50 N/m
J.J. Greffet EM2C Ecole Centrale de Paris 2003
polystyrene sphere R= 42 m metal coating (gold) =300 nm
Measure (G. Torricelli PhD thesis LEPES 2001-2004)Omicron VT UHV AFM
100nm < z < 500nmV
Sphere/surface distance determinationCantilever spring constant measurement
Static cantilever deflection F= -kx
Cantilever deflection cannot be neglected at large voltage
zzdef
19200 19300 19400 19500 19600 19700
0,0
0,5
1,0
1,5
2,0
2,5
3,0
3,5
4,0 2,5V 2,0V 0,5V
Am
plit
ud
e (a
.u)
frequency (Hz)
Vdw/ Casimir: Oscillating mode of the sphere at resonance
k
Fd res
VF
res
res
0 50 100 150 200 250 300 350 400-40
-35
-30
-25
-20
-15
-10
-5
0
5
f (
Hz)
Distance (nm)
Casimir/vdw interaction (fit in z-3)
86.4 mK ≈ 88.6N/m
Z ≈ 0.05 - 0.4 m
Electrostatic longrange interaction V=0.5volt (fit in z-2)
fres=52.670 kHz
L=50nmgrad F= 10-1 N/m
p ≈ 130nm
Short distances: D<<p with p plasmon length,
Force machine: sphere-surface distance
10nm
Tuning forkK= 1000 - 10000 N/m
Full scale is 0.3Hz
The distance is again determined using capacitive interaction
Large surface roughness at the origin of our measurementno van der Waals contribution,
instead direct metallic bonding
At nanoscale,At nanoscale,
attractive force attractive force
between 2 metallic plates between 2 metallic plates
in vacuumin vacuum