UNIVERSITE Pierre & Marie CURIE La science à PARIS

Bernard Perrin

International Workshop on « Nanoscale Energy Conversion and Information Processing Devices »

- September 24-26, 2006, Nice - France - 

"NANO-ACOUSTICS AND TERAHERTZ ACOUSTICS"

Probing vibrations at the nanoscale

LATA

Fré

quen

cy

(T

Hz)

10

1,010-310-4 10-2 10-1

10-3

10-4

10-2

10-1

1,0

10-5

piez

oB

rillo

uin

Picose

cond

acou

stics IXS

Wavevector q/ (u.a.)

nano-systems

neutron

Sound wave velocity in solids5 – 10 nm/ps

Phonons :nm scale THz range

What can be done with an optical pump probe technique to increase the frequency range of laser ultrasonics? Phonon engineering Phonon nanocavities

Ballistic phonon heat transport

Picosecond acoustics(H. Maris, 1985)

probe

pump

Lsubstrate > a few hundreds m

Lfilm > a few tens nm

substrate

ir

r

reflectometry

interferometry

Frequency (THz)

0,0 0,1 0,2 0,3 0,4 0,5 0,6

Pow

er s

pec

tru

m

0,00

0,02

0,04

0,06

0,08

Nanometric sonar in thin films

Lattice dispersion Lattice anharmonocity

(MgO)

Dispersion and nonlinearity : Solitons

0 0 ,0 s 0. sssol

150 fs(1.4nm)

Stable solution(soliton)

zs

stzhtz

2sec),(

6

1 and 24

00

z

s

s

sss

2

2202

2

zs

t

Non linearity

zz

s2

0

Dispersion

2

4

02z

s

strain 5 10-3

spatial width (nm)

temporal width

(fs)

frequency (–3dB) (THz)

Si 3.8 450 0.8 MgO 1.4 150 2.33 Quartz 6.3 990 0.36 Sapphire 3.6 320 1.1 GaAs 3.2 675 0.52

112 2

02

.

ii

sol

swEn

112 2

0 iii wsw

Multi-soliton formation

Rectangular initial strain i

iw

i

sii wss

w0

2

0

1264

Area conservation

Acoustic Nonlinearity

2

2202

2

zs

t

Non linearity

zz

s2

011

11111 3

C

CC

- Harmonic distorsion- sound velocity = f()- Acoustic rectification

GaAspump

probe

Al-30 nm Al-30 nm

356 m

[100]

-30 -20 -10 0 10 20 30 40 50 60-20

-16

-12

-8

-4

0

4

8

12

r/r

(10

-6)

délai (ps)

I0

-30 -20 -10 0 10 20 30 40 50 60-20

-16

-12

-8

-4

0

4

8

12

r

/r (

10-6

)

délai (ps)

I0

2I0

-30 -20 -10 0 10 20 30 40 50 60-20

-16

-12

-8

-4

0

4

8

12

r

/r (

10-6

)

délai (ps)

I0

2I0

4I0

-30 -20 -10 0 10 20 30 40 50 60-20

-16

-12

-8

-4

0

4

8

12

r

/r (

10-6

)

délai (ps)

I0

2I0

4I0

8I0

-30 -20 -10 0 10 20 30 40 50 60-20

-16

-12

-8

-4

0

4

8

12

r

/r (

10-6

)

délai (ps)

I0

2I0

4I0

8I0

16I0

-30 -20 -10 0 10 20 30 40 50 60-20

-16

-12

-8

-4

0

4

8

12

r

/r (

10-6

)

délai (ps)

I0

2I0

4I0

8I0

16I0

32I0

-30 -20 -10 0 10 20 30 40 50 60-20

-16

-12

-8

-4

0

4

8

12

r

/r (

10-6

)

délai (ps)

I0

2I0

4I0

8I0

16I0

32I0

64I0

Ballistic propagation of heat pulses

Z-cut in Sapphire - T = 3.8 K

time

longitudinal phononstranverse phonons

1exp

3

.

Tk

E

B

ph

Black body radiation

Spectrum up to a few THz

Q

Dispersion curve

wave vector q (nm-1)

0.00 0.05 0.10 0.15 0.20 0.25

Fre

qu

ency

(T

Hz)

0.00

0.05

0.10

0.15

0.20

qs

GaAs/AlAs

221111

22

22

112211 dqsindqsin

s

s

s

s

2

1dqcosdqcosqdcos

Extended Brillouin zone

wave vector q (nm-1)

0.00 0.05 0.10 0.15 0.20 0.25

Fre

qu

ency

(T

Hz)

0.00

0.05

0.10

0.15

0.20

016.1s

s

s

s

2

1 194.1

s

s

11

22

22

11

22

11

Reduced Brillouin zone

wave vector q (nm-1)

0.00 0.01 0.02 0.03 0.04 0.05 0.06

Fre

qu

ency

(T

Hz)

0.00

0.05

0.10

0.15

0.20

reflectometry

Can we do the same with a pump probe technique?

T = 15 K

GaAspump

probe

Al-30 nm Al-30 nm

356 m

[100]

One way+

6 round trips

One way+

2 round trips

interferometry

First longitudinal coherent acoustic echo (one way trip)

Temperature dependence

Time (ps)

0 200 400 600 800 1000 1200

m(

r/r)

(arb

. uni

ts)

17.2 K

15.9 K

14.1 K

11.8 K

10.0 K

27.2 K

22.5 K

19.5 K

Q = 0.12 nJ

0

30

60

1

313

200 400 600 800 1000 1200 1400

Pos

ition

(m

)

Delay (ps)

12 K - Q=0.6 nJ

pump

Al 30 nm

Al 30 nm

probe at differentlocations

XY scan in the detection surface

Heat pulse : moving acoustic

source

vph.vph.

vst.

vstvph : building up ofa large matter displacement

Phonon engineering and acoustic nanocavity

Acoustic cavities without capping

Frequency (GHz)

0 50 100 150 200 250

Su

rfa

ce d

isp

lace

men

t (A

rb. u

nit

s)

0

2

4

6

8

10

Cavity Cavity

Cavity D10

Frequency (THz)

0.00 0.05 0.10 0.15 0.20

Pow

er s

pect

rum

0.0

0.5

1.0

1.5

2.0

2.5Cavity modes

Acoustic mirror Acoustic nanocavity

Nanocavity used as a phonons generator

0 500 1000 1500 2000 2500 3000 3500 4000 4500

5

6

0 1000 2000 3000 4000

-4

-2

0

2

4

0,00 0,05 0,10 0,150

5

10

15

20

25

0,00 0,05 0,10 0,150

2

4

6

8

10

12

14

16

18

500 550 600 650 700 750 800 850 900 950 1000

4,70

4,75

4,80

4,85

4,90

4,95

Re(R

/R)

t (ps)

acoustic wave vector

Im(

R/R

)

D10 20 mars 2006 20K 750nm TsunamiPompe côté cavité nuesonde côté substrat aluminé

Fréq (THz)

-1,5

-1,0

-0,5

0,0

Re(R

/R)

t (ps)

cavity

GaAs

356 µm

pump probe

Cavity D10 - Simulation

Frequency (THz)

0,04 0,06 0,08 0,10 0,12 0,14 0,16

Pow

er s

pec

tru

m (

arb

. un

its)

0,00

0,02

0,04

0,06

0,08

0,10

0,12

Cavity D10 - Experiments

Frequency (THz)

0,04 0,06 0,08 0,10 0,12 0,14 0,16

Pow

er s

pec

tru

m (

arb

. un

its)

0

2

4

6

8

10

12

14

16

Cavity D10 - Simulation

Frequency (THz)

0,04 0,06 0,08 0,10 0,12 0,14 0,16

Pow

er s

pec

tru

m (

arb

. un

its)

0,00

0,02

0,04

0,06

0,08

0,10

0,12

absorption in every GaAs layersabsorption only in the cavity

Selective excitation of the cavity mode

wave vector (nm-1)

0.00 0.01 0.02 0.03 0.04 0.05 0.06

Fre

quen

cy (

TH

z)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

n4

q

Nanocavity or mirror used as a phonon detector

0,0 0,1 0,2 0,3 0,4 0,5 0,6

4 avril 06 D1 2 800nm Mai Tai a froid transmissionpompe côté substrat + 30nm Alu sonde côté cavité nue

0.25 nJ/ pulse

1.3 nJ/ pulse

2.5 nJ/ pulse

5.0 nJ/ pulse

6.4 nJ/ pulse

Frequency (THz)

GaAs

356 µmAcoustic mirror

pumpprobe

Laurent Belliard – INSP Alex Fainstein – Institut Balseiro (Bariloche)Agnès Huynh - INSPBernard Jusserand - INSPDaniel Kimura- Lanzillotti (INSP/Institut Balseiro - Bariloche)Aristide Lemaitre (LPN – Marcoussis)Emmannuel Péronne - INSPShuo Zhang - INSP

Phonon engineering in the subterahertz range is possibleSemiconductor superlattices work as excellent acoustic Bragg mirrorsAcoustic nanocavity has been evidencedA first step towards a SASER

12th international conference on phonon scattering in condensed matter

Phonons in nanostructures and low-dimensional structuresUltrafast acousticsCoherent phononsMicro and nano acousticsMEMS and NEMS (micro and nano electromechanical systems)Phonons in devices for electronics, optoelectronics and spintronicsElectron-phonon interactionMicro and nanoscale phonon heat transferNanoscale energy conversion and thermo-electricityPhonon transportSolitons and nonlinear phenomenaAcoustic waves in anisotropic media and phonon imagingPhonons in superconductors and magnetic materialsPhononic crystals Surface and Interface phononsQuantum fluidsLattice dynamicsPhonons in glasses and disordered systemsPhase transitionsLight, neutron and X-ray inelastic scatteringNew techniquesParticle detectors

July 15–20, 2007