Visiting the thermal emission in the near

Visiting the thermal emission in the near

Thermal radiation scanning tunnelling
microscope (TRSTM):
Near-field imaging and spectroscopy
probe of the thermal emission
Yannick De Wilde
Institut Langevin, CNRS, ESPCI ParisTech, Paris
yannick.dewilde@espci.fr
Nanoscale Radiative Heat Transfer–May 13, 2013
Motivation : Theoretical predictions
Energy density
1.0
SiC
z = 100 µm
0.8
Far-Field
0.6
0.4
0.2
0.0
wresonance = 178.7 *1012 s-1
= 948 cm-1
lresonance = 10.55µm
Shchegrov, Joulain, Carminati, Greffet,
Phys. Rev. Lett., 85, 1548 (2000)
20x10
Energy density
SiC = polar material which supports
surface phonon-polaritons
=> Evanescent waves thermally
stimulated
3
z = 100 nm
15
Near-Field
10
5
0
0
100
200
300
w (Hz)
Nanoscale Radiative Heat Transfer–May 13, 2013
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400 500x10
12
Motivation : Far-field measurements
SiC + grating
T=500°C
AFM (topography)
Antenna like emission pattern
SiC
DIFFRACTION
Greffet, Carminati, Joulain, Mulet,
Mainguy, Chen, Nature 416, 61 (2002)
SPATIAL COHERENCE OF THERMAL EMISSION !!!
Nanoscale Radiative Heat Transfer–May 13, 2013
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Probe of thermal emission
in the near-field
Optical
Detector
Collection
optics
Far-field
l
Near-field
T≠0
1
U (r , w ) = r (r,w ) hw
exp ( hw / kT ) - 1
LDOS
Photon statistics
(Bose Einstein distribution)
Nanoscale Radiative Heat Transfer–May 13, 2013
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OUTLINE
Ø Infrared-NSOM & Thermal radiation scanning tunnelling (TRSTM) setup.
Ø Examples using laser sources.
Ø TRSTM for imaging thermal radiation in the near-field.
Ø TRSTM for spectroscopy measurements.
Nanoscale Radiative Heat Transfer–May 13, 2013
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Optical near-field :definition
k= e
0,8
Surface waves
0,6
Real metal
0,4
Surface Plasmons
ky
kx 2 + k y 2 = k 2
Plane
waves
0,2
w/wp
SPPs
c
Light line (e=1)
0,707
Air
w
1
ckx/wp
kx
2
Source
Sub-l objects
k=(w/c) =(2p/l)
Evanescent waves
No propagation
in far-field
z
x
10 nm
Nanoscale Radiative Heat Transfer–May 13, 2013
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Applications of near-field probes
NANOMATERIALS
z
CONFINED FIELDS
PROPAGATING
Illumination
EVANESCENT
High spatial
frequencies
(small details)
y
x
<<l
Optical imaging
of nano-materials
( resolution << l )
SPPs
dd
dm
Air
EVANESCENT
Real metal
Detection of purely
evanescent fields
( example: surface plasmons )
Nanoscale Radiative Heat Transfer–May 13, 2013
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Aperture NSOM
Veerman et al. ,
Appl. Phys. Lett. 72, 3115 (1998)
Pohl et al. , Appl. Phys. Lett 44, 651 (1984)
NSOM= near-field scanning optical microscope
Nanoscale Radiative Heat Transfer–May 13, 2013
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Aperture NSOM
Veerman et al. ,
Appl. Phys. Lett. 72, 3115 (1998)
Silica fiber : Well-suited for visible and near-IR but not for
the mid-IR !!!
Nanoscale Radiative Heat Transfer–May 13, 2013
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Wikramasynghe et al., APL65,1623 (1994);
Boccara et al., Micro. Microanal. Microstruct. 5, 389 (1994)
- Perhaps one could try instead to disturb the
near-field with a small subwavelength scatterer…
« Scattering-type NSOM » (s-NSOM)
A. Claude Boccara
Idea :
I scat . ( xt , yt ) = s E ( xt , yt )
2
In practice :
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Tip approach in an evanescent field.
I scat . ( xt , yt ) = s E ( xt , yt )
Nanoscale Radiative Heat Transfer–May 13, 2013
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2
s-NSOM for mid-infrared detection
of near-field thermal emission
Thermal radiation scanning tunnelling microscope
« TRSTM »
W
Filter
W
tip (W)
IMAGING De Wilde, Formanek, Carminati, Gralak, Lemoine, Mulet, Joulain, Chen, Greffet, Nature 444, 740 (2006)
SPECTROSCOPY
Babuty,, Joulain, Chapuis, Greffet, De Wilde, Phys. Rev. Lett. 110, 146103 (2013).
Nanoscale Radiative Heat Transfer–May 13, 2013
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Mid IR s-NSOM – TRSTM:
Tip preparation
Tungsten wire
BEFORE
d=50 µm
Electrochemical etching
AFTER
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Mid IR s-NSOM – TRSTM:
Tip gluing
De Wilde, Formanek, Aigouy,
Rev. Sci. Instrum. 74, 3889 (2003)
Nanoscale Radiative Heat Transfer–May 13, 2013
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Mid IR s-NSOM – TRSTM:
Cassegrain objective
Reflective objective
5 cm
5 cm
Two gold spherical mirrors:
- Broad spectral range (UV, Vis,
IR, THz)
- No chromatic aberrations
Magnification= x36
Numerical aperture= 0.5
Working distance= 10.4 mm
10.4 mm
Sample
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Mid IR s-NSOM – TRSTM:
HgCdTe detector
Liquid N2 cooled
Size: d=0.5 mm (5 10-2 cm)
Detectivity: D*»4 1010 cm Hz1/2 W -1
(>50 % between l» 7 µm - 12 µm)
Noise =
d
-12 W
»
10
Hz1/ 2
D*
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Super-resolution with external source:
Imaging of nano-materials
Infrared near-field
imaging
AFM
Holes sub-l (f=200nm) :
SiO2
Detector
Laser
l=10.6 µm
Chromium
Tip
Cr
SiO2
Optical
200 nm
Optical resolution
~ 30 - 50 nm
~ l/200
Piezoelectric translation stage
(scanner)
Formanek, De Wilde, Aigouy,
J. Appl. Phys. 93, 9548 (2003)
NSOM (3mmx3mm)
l=10.6 mm
Diffraction limit
Nanoscale Radiative Heat Transfer–May 13, 2013
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Building block of active plasmonics:
Slit doublet experiment
Measured
topography
(AFM)
3
2
1
Top electrode
of quantum
cascade laser
2
Au
1
l≈7.5µm
SPP
Coupler
Generator
2
1
llaser/neff
Collaboration: R. Colombelli’s group, IEF
Passive
waveguide
3
b spp
-b spp
2
1
llaser
Babuty, et al., Phys. Rev. Lett., 104, 226806, (2010)
Nanoscale Radiative Heat Transfer–May 13, 2013
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Building block of active plasmonics:
Slit doublet experiment
Measured
topography
(AFM)
2
1
3
Au
2
1
Measured
near-field
l≈7.5µm
Interference of counterpropagating SPPs
generated by electrical pumping of a QC laser.
Collaboration: R. Colombelli’s group, IEF
Babuty, et al., Phys. Rev. Lett., 104, 226806, (2010)
Nanoscale Radiative Heat Transfer–May 13, 2013
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Remark 1: Far field background issue
50 µm
Laser
beam
Tip
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Extracting the near-field contribution in
the detector signal.
Tip
Far-field
Near-field
Sample
~l
<< l
Nanoscale Radiative Heat Transfer–May 13, 2013
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Z
Tip-Scattered intensity in a plan
perpendicular to metal surface.
Iscat.(xt,zt)
z
x
Bousseksou, Babuty, Tetienne, Moldovan, Braive, Beaudoin, Sagnes,
De Wilde, Colombelli, Optics Express 20, 13738 (2012).
Nanoscale Radiative Heat Transfer–May 13, 2013
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Extracting the near-field contribution in
the detector signal.
Tip
Far-field
Near-field
Sample
~ 100 nm
W»32 KHz
~l
<< l
Nanoscale Radiative Heat Transfer–May 13, 2013
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Z
Lock-in demodulation
|E|2
Signal at detector
S µ s|E|2
- If modulation applied along z:
S(z+a cos Wt) µ S0+A dS/dz cos Wt +
B d2S /dz2 cos 2Wt +…
Sample
surface
z
Signal demodulation with a lock-in :
SW µ dS /dz
- Rejection of far-field contribution
- Improvement of near-field/far-field ratio
when demodulating at tip oscillation
S2W µ d2S /dz2
frequency W or higher harmonics.
Bousseksou, Babuty, Tetienne, Moldovan, Braive, Beaudoin, Sagnes,
De Wilde, Colombelli, Optics Express 20, 13738 (2012).
Nanoscale Radiative Heat Transfer–May 13, 2013
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Infrared apertureless SNOM with laser source
CO2 laser beam
[l=10.6µm]
reference
Detector
W
Tip
S
Lock-in
amplifier
AFM
Signal
SW or S2W
Metal film
SiO2
Optical
= SW or S2W
Formanek, De Wilde, Aigouy, J. Appl. Phys. 93, 9548 (2003)
Nanoscale Radiative Heat Transfer–May 13, 2013
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Remark 2: Tip illumination conditions
S(w)=seff.(etip,esample,rtip)|E(rtip)|2
|E(rtip)|2 is here imposed by the
external laser source.
Nanoscale Radiative Heat Transfer–May 13, 2013
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Thermal Radiation STM: New paradigm
W
Filter
W
tip (W)
The EM-LDOS r(rtip,w)
2
1
can be probed with
E (rtip , w ) = r (rtip ,w ) hw
exp ( hw / kT ) - 1 the TRSTM.
Nanoscale Radiative Heat Transfer–May 13, 2013
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Jean-Jacques
Greffet
Near-field imaging
with the TRSTM
Experiments:
F. Formanek
(ex-PhD,ESPCI)
Karl
Joulain
•De Wilde, Formanek, Carminati, Gralak, Lemoine, Mulet,
Joulain, Chen, Greffet, Nature 444, 740 (2006).
•Shchegrov, Joulain, Carminati, Greffet,
Phys. Rev. Lett., 85, 1548 (2000).
Rémi
Carminati
Boris
Gralak
•Joulain, Carminati, Mulet, Greffet, PRB 68, 245405 (2003).
Nanoscale Radiative Heat Transfer–May 13, 2013
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TRSTM Images of pattern of Au on SiC
Tsample » 500 K
Ttip » 300 K
B
B
A
Au
A
SiC
Topography (AFM)
TRSTM
Resolution ~ 100 nm
TRSTM signal ~ 20 pW
No filter
,W
~
IR-SNOM signal
103
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Energy selection :
TRSTM images with filter at l = 10,9 mm
SiC
TRSTM
A
B
C
Au
A
B
Topography
(AFM)
C
FRINGES
=
Thermally excited surface
plasmon modes in a
planar cavity
Nanoscale Radiative Heat Transfer–May 13, Nature
2013 444, 740 (2006).
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Images TRSTM vs. EM-LDOS
B. Gralak
Inst. Fresnel
TRSTM
l=10.9mm
T=170°C
AFM
l=10.6mm
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Higher harmonic demodulation
SiC
Au
SiC = Polar material with surface :
phonon polaritons.
SiC
Dispersion curve
TRSTM image at 2W
Filter at 10.9mm (width 1 mm)
V. Shchegrov, K. Joulain, R. Carminati,
J-J. Greffet, Phys.Rev.Lett. 85, 1548(2000)
• Near-field energy density
peaked at 10.55 mm.
• Large k║ => higher confinement
Nanoscale Radiative Heat Transfer–May 13, 2013
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Revisiting « blackbody radiation » spectra
in the near-field.
Near-field spectroscopy
with the TRSTM
Karl
Joulain
Jean-Jacques
Greffet
Pierre-Olivier
Chapuis
Arthur
Babuty
?
d
d << lemission
• Babuty, Joulain, Chapuis, Greffet, De Wilde,
Phys. Rev. Lett. 110, 146103 (2013).
• Joulain, Ben-Abdallah, Chapuis, Babuty,
De Wilde, arXiv:1201.4834.
Nanoscale Radiative Heat Transfer–May 13, 2013
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Spatial coherence of thermal emission in
the near-field of SiC
SiC + grating
T=500°C
AFM (topography)
Antenna like emission pattern
SiC
DIFFRACTION
Greffet, Carminati, Joulain, Mulet,
Mainguy, Chen, Nature 416, 61 (2002)
SPATIAL COHERENCE OF THERMAL EMISSION !!!
Nanoscale Radiative Heat Transfer–May 13, 2013
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What about the temporal coherence ?
Nanoscale Radiative Heat Transfer–May 13, 2013
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Local FTIR spectroscopy probe of nearfield thermal emission
FTIR
d
TRSTM
Delay
MCT Detector
BS
Lock-In
amplifier
TRSTM
Tip
Objective
Sample
FTIR
i
Heater
Intensity
Wtip
d
Nanoscale Radiative Heat Transfer–May 13, 2013
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LDOS on SiC : Theoretical predictions
stheo.=948 cm-1
Dispersion relation of SPhP
w resonance
Wavenumber s [cm-1]
Shchegrov, Joulain, Carminati, Greffet, Phys. Rev. Lett., 85, 1548 (2000)
Nanoscale Radiative Heat Transfer–May 13, 2013
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Near-field thermal emission on SiC
Intensity (a.u.)
0.025
0.020
0.015
sexp.=913 cm-1
471 K
433 K
395 K
342 K
330 K
0.010
0.005
0.000
-0.005
800
1000
1200
1400
-1 )
Wavenumberws (cm
[cm-1]
Frequency
Babuty, Joulain, Chapuis, Greffet, De Wilde, Phys. Rev. Lett. 110, 146103 (2013).
Nanoscale Radiative Heat Transfer–May 13, 2013
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Intensity (a.u.)
Test of near-field origin of the signal
1 Wtip
0.004
2 Wtip
0.002
0.000
800
1000
1200
1400
-1)
Wavenumber
[cm-1]
Frequency
w s(cm
Peak present at 1 Wtip and 2 Wtip
Babuty, Joulain, Chapuis, Greffet, De Wilde, Phys. Rev. Lett. 110, 146103 (2013).
Nanoscale Radiative Heat Transfer–May 13, 2013
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SiC : Experiment vs. LDOS
Experiment
Theory
Partial temporal coherence is demonstrated, but a redshift
and broadening is observed in the experimental peak
with respect to theory.
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S(w)=seff.(etip,esample,rtip)|E(rtip)|2
|E(rtip)|2 µ EM-LDOS
T=500 K
See Karl Joulain’s Talk at 2 pm.
Joulain, Ben-Abdallah, Chapuis, Babuty, De Wilde, arXiv:1201.4834.
Nanoscale Radiative Heat Transfer–May 13, 2013
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SiC: Theoretical modelling vs. experiment
SiC
Good agreement with experiments (Rtip=1.6 µm)
Babuty, Joulain, Chapuis, Greffet, De Wilde, Phys. Rev. Lett. 110, 146103 (2013).
Joulain, Ben-Abdallah, Chapuis, Babuty, De Wilde, arXiv:1201.4834.
Nanoscale Radiative Heat Transfer–May 13, 2013
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SiO2: Theory modelling vs. experiment
Intensity (a.u.)
SiO2
1.0
Theory (rt=1.6 µm)
0.8
Experiment (T=473 K)
0.6
0.4
Sample: SiO2
0.2
0.0
-0.2
700
800
900
1000
1100
-1
1200
Wavenumber s (cm )
Good agreement with experiments (Rtip=1.6 µm)
Babuty, Joulain, Chapuis, Greffet, De Wilde, Phys. Rev. Lett. 110, 146103 (2013).
Joulain, Ben-Abdallah, Chapuis, Babuty, De Wilde, arXiv:1201.4834.
Nanoscale Radiative Heat Transfer–May 13, 2013
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TRSTM spectroscopy with a heated tip
(Markus B. Raschke group)
Jones, Raschke, Nanoletters 12, 1475 (2012).
Nanoscale Radiative Heat Transfer–May 13, 2013
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Mapping the EM-LDOS in the visible
Valentina Krachmalnicoff
wfluo
12
2
1
100 nm
Da Cao
Mapping of LDOS at wfluo. based
on measurements of G .
Rémi Carminati
V.Krachmalnicoff, et al., Phys. Rev. Lett. 105,183901 (2010).
Krachmalnicoff, Cao, Cazé, Castanié, Pierrat, Bardou, Collin, Carminati, De Wilde,
Optics Express 21, 11536 (2013).
+ Romain Pierrat, Alexandre Cazé, Etienne Castanié
Nanoscale Radiative Heat Transfer–May 13, 2013
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CONCLUSIONS
Infrared-NSOM based on home-built system for subwavelength
imaging of materials and investigations of plasmonic devices.
The set-up can operate without any external source in the
« TRSTM mode », allowing the detection of thermal emission
in the near-field.
TRSTM images and FTIR spectra have been obtained. They probe
the spatial and frequency dependence of the EM-LDOS (see Karl
Joulain’s talk this afternoon).
TRSTM spectra have revealed the temporal coherence
of the near-field thermal emission in SiC and SiO2.
Nanoscale Radiative Heat Transfer–May 13, 2013
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THANK YOU !
Near-Field thermal emission:
Laboratoire Charles Fabry, Inst. d’Optique
J.-J. Greffet, P. Ben Abdallah
Institut P’
K. Joulain
Centre d’Etudes Thermiques de Lyon
P.-O. Chapuis
Institut d'Electronique du Sud
T. Taliercio, V. Ntsame Guilengui
Labo. Nanotechnologies Nanosystèmes
Ali Belarouci
CRHEA-CNRS
Yvon Cordier, Adrien Michon
SPPs active devices:
Institut d’Electronique Fondamentale
R. Colombelli, D. Costantini, A. Bousseksou
III-V Lab
A. Accard,J. Decobert, G-H. Duan
Laboratoire Photonique et Nanostructures
G. Beaudoin, I. Sagnes,
Institut Langevin
A. Babuty, L. Greusard, F. Peragut
Institut Langevin: A. Babuty, F. Peragut, L. Greusard, V. Krachmalnicoff, R. Carminati,
D. Cao, A. Cazé, R. Pierrat, E. Castanié (+ LPN: S. Collin, N. Bardou)
=
+
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