28.11.2014 Views

(Microsoft PowerPoint - \351coleaNW_ayari2.ppt) - IEMN

(Microsoft PowerPoint - \351coleaNW_ayari2.ppt) - IEMN

(Microsoft PowerPoint - \351coleaNW_ayari2.ppt) - IEMN

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

Introduction to nano-electromechanical<br />

systems<br />

Anthony Ayari, Pascal Vincent, Sorin Perisanu, May<br />

Choueib, Vincent Gouttenoire, Steve Purcell<br />

Laboratoire de Physique de la Matière Condensée et<br />

Nanostructures, Université Lyon 1<br />

Mikhael Bechelany, Arnaud Brioude,<br />

David Cornu<br />

Laboratoire de Multimatériaux et Interfaces,<br />

Université Lyon 1


Outline<br />

1)NEMS<br />

definition<br />

materials<br />

scaling<br />

experimental method<br />

2)New effects in nanomechanics<br />

oscillator<br />

non linear effect, hysteresis<br />

frequency tuning<br />

Casimir forces<br />

quantum/ thermal regime<br />

3)state of the art<br />

-performances : frequency range, quality factor<br />

-nanobalance<br />

-Self oscillations in nanomechanics


Electro Mechanical Systems<br />

What is is ? How it works ?<br />

Signal IN(ω)<br />

x<br />

External Perturbation<br />

Signal OUT(ω)


At the micron scale<br />

Detector<br />

Accelerometer for airbag<br />

Mechanical springs<br />

Width 50nm<br />

1 µm<br />

Electrostatic combs<br />

Gap width 150nm<br />

Actuator<br />

Digital micromirror device in video projector


materials<br />

Si, SiN, GaAs<br />

standard in<br />

microelectronic<br />

Nanowire Pt, SiC<br />

AlN, ZnO piezo-<br />

electric<br />

carbone nanotubes<br />

300 nm<br />

Pt<br />

SiN<br />

J.A.P. 99,124304(2006)<br />

A.P.L. 83,1240(2003)


Scaling<br />

Mass (< 10 -15<br />

g) m eff ~ L 3<br />

Resonant frequency (10 MHz à 1GHz) ~ L -1<br />

Amplitude (


Nano Electro Mechanical Systems<br />

ISSUES :<br />

Low OUTPUT signal<br />

Low Q factor<br />

Crosstalk<br />

Signal IN(ω)<br />

x<br />

External Perturbation<br />

CROSS TALK<br />

Signal OUT(ω)


Detection/actuation<br />

<br />

<br />

<br />

<br />

<br />

<br />

<br />

Magnetomotive<br />

Optical : laser<br />

Capacitive<br />

SEM<br />

Field emission<br />

AFM<br />

STM<br />

F=I*L^B<br />

Laplace Force<br />

Need high magnetic field


Optical coupling<br />

2µm<br />

Need flat surface, good reflexion<br />

APL 86 193114 (2005)


capacitive<br />

Low signal and large band pass<br />

Impedance mismatch with 50 Ω


SEM<br />

SiC<br />

Nanowire<br />

rest fundamental harmonics<br />

PRB 66 073406 (2002)


Field emission<br />

Experimental set up, out of the resonance<br />

Nanowire<br />

Tungsten tip<br />

Anode<br />

V A<br />

-<br />

+<br />

Anode<br />

∼ V s<br />

e -


Field emission<br />

Experimental set up at the resonance<br />

Nanowire<br />

Tungstene tip<br />

Anode<br />

V A<br />

-<br />

+<br />

Anode<br />

∼ V s<br />

e -<br />

Amplification of the vibration amplitude by<br />

projection


Why nano ?<br />

Lower size<br />

Lower power consumption<br />

Faster mechanically and thermally<br />

Mass sensing : single molecule/atom, nano<br />

bio<br />

New forces/phenomena/paradigm


What’s new?<br />

Non-linearity<br />

Frequency tuning<br />

Casimir force surface


Non-linear<br />

effects<br />

Amplitude<br />

∆f<br />

Fréquence<br />

Lorentzien shape,<br />

quality factor :<br />

Q=f/<br />

f/∆f<br />

ẍ+ω 0 ẋ/Q+ /Q+ω 2 0 x =F(t)/m eff


Non-linear<br />

effects<br />

Amplitude<br />

Frequency (Hz)<br />

Hysteresis, , jumps,<br />

memory<br />

ẍ+ω 0 ẋ/Q+ /Q+ω 2 0 x +ax 3 + … =F(t)/m eff


Non-linear<br />

effects<br />

Amplitude<br />

Frequency (Hz)<br />

Need to reduce<br />

excitation<br />

Critical amplitude:


Role of Electric Field<br />

Electrostatiques Forces :<br />

– T L ≈ (ε 0 /2).πr 2 . F 2 ≡ γ 2 β 2 V 2 APP<br />

Tuning like music intrument


Frequency tuning<br />

Nanofil<br />

4.0<br />

MWNT<br />

Pointe en tungstène<br />

Anode<br />

3.0<br />

V A<br />

-<br />

+<br />

Anode<br />

e -<br />

2.0<br />

1.0<br />

∼ V s<br />

0.0<br />

400 500 600 700 800 900 1000<br />

Tension (Volt)<br />

PRL 89, 276103 (2002)<br />

linear variation of the resonant<br />

frequency with tension<br />

tunable resonator


Casimir forces<br />

PRL 87, 211801 (2001)<br />

Science 291, 1941 (2001)<br />

Quantum fluctuations of vacuum<br />

H=ħω n (p+1/2) with p=0<br />

Confinement effect ω n inside < outside


Thermal vibration<br />

E thermal =k B T ⇒<br />

∆x thermal = L -0.5<br />

Observed in CNTs<br />

dominates excitation<br />

for low L (∆x(<br />

lin ~ L)<br />

P.R.B. 58,14013(1998)<br />

Nature 381, 678 (1996)<br />

Nanoletters 3,1577(2003)


Quantum limit<br />

H=½mv<br />

2 + ½kx<br />

2 ⇒ H=hν(a<br />

+ a+1/2)


Macroscopic quantum oscillator<br />

NEMS coupled to an SET<br />

∆x quantique = L -1 , n=58<br />

Resolution ∆x x = 114 fm<br />

1GHz=50 mK<br />

Quantum computing, Heisenberg<br />

science 304,74 (2004)<br />

PRL 94 030402 (2005)<br />

, Heisenberg inequality


Performances<br />

Damping<br />

Mass sensing<br />

Self-oscillation


Quality factor<br />

Log(Q)=.3*log(vol(mm 3 ))+6


Nanobalance<br />

nano letters 6, 583 (2006)<br />

Résolution<br />

δm=2m* m=2m*δν/ν=2m/Q<br />

⇒ 7 zg (10 -21<br />

g) soit 30 atomes


GHz NEMS<br />

Nature 421,496 (2003)<br />

New Journal of Physics 7 (2005) 247


Self-oscillations<br />

What is self oscillation?<br />

– Self oscillator: constant input generates periodic<br />

output<br />

=Driven oscillator: periodic input generates periodic<br />

output<br />

Observed in many fields:<br />

– Oscillating chemical reaction<br />

– heart beat<br />

– Rayleigh - Bénard<br />

thermal convection<br />

– Gunn diode: negative differential resistance<br />

electrical device<br />

Is it possible in NEMS ?


Self-oscillation in UHV<br />

<br />

<br />

Widening of the field<br />

emission pattern without<br />

AC signal<br />

Jump and hysteresis in IV<br />

curve


SEM Experiments<br />

Ayari et al., Nano Letters Vol.7, Issue 8, 2252, (2007)


Self-oscillations in SEM


Why did it work ?<br />

V<br />

R, k<br />

C, k Y , m eff , γ<br />

es<br />

x<br />

U, I FN


Why did it work ?<br />

V<br />

C, k R, k<br />

es<br />

Y , m eff , γ<br />

U, I<br />

x<br />

FN<br />

⇒ Similar to the physics of the garden<br />

hose


Why did it work ?<br />

Mechanical equation<br />

&& x<br />

2<br />

+ γ x&<br />

+ ( ω + pU ) x =<br />

0<br />

2<br />

0<br />

k Y m eff , γ k es (U)<br />

x


Why did it work ?<br />

<br />

Electrical equation<br />

d<br />

dt<br />

VDC −U<br />

( CU ) = − I<br />

FN<br />

,<br />

R<br />

( U x)<br />

Wire apex<br />

C(x)<br />

V<br />

R I FN (U, x)<br />

tip<br />

U


Why did it work ?<br />

Mechanical equation<br />

&& x<br />

Electrical equation<br />

d<br />

dt<br />

2<br />

+ γ x&<br />

+ ( ω + pU ) x =<br />

0<br />

VDC −U<br />

( CU ) = − I<br />

FN<br />

,<br />

R<br />

2<br />

0<br />

( U x)<br />

huge R<br />

Coupled equations<br />

Low damping (Perisanu et al. APL 2007, 90, 043113)<br />

x dependence in FN current<br />

Non linear terms


Numerical simulations and semianalytical<br />

calculation<br />

•Good qualitative agreement<br />

•hysteresis


Summary<br />

First observation of self–oscillation in a fully<br />

electrical NEMS<br />

DC-AC converter 50 %<br />

Nano AC generator<br />

Solution against cross talk


Conclusion<br />

NEMS : mechanical oscillators at the<br />

nanoscale<br />

Difficult to actuate and detect, high<br />

damping<br />

Applications in mass sensing, high<br />

frequency communication

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!