the design of dielectric environment for ultra long lifetime of graphene plasmon dr. qing dai...
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![Page 1: The design of dielectric environment for ultra long lifetime of graphene plasmon Dr. Qing Dai 22/10/2015](https://reader033.vdocuments.net/reader033/viewer/2022061500/5697bf931a28abf838c8f995/html5/thumbnails/1.jpg)
The design of dielectric environment for ultra long lifetime of graphene plasmon
Dr. Qing Dai
22/10/2015
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Surface Plasmons (SPs)
Surface free charges oscillations
-
E(t)
+
Manipulation of light at nanoscale
Spatial confinement Local field enhancement
Science, 2010, 328, 440
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Metamaterials map
Ultra-high mobility
Low carrier density
Low interband losses
Graphene is an ideal material for plasmon!
Atwater, Science, 2011
Plasmon lifetime
Graphene
Calculated lifetime :~10 ps in mid-IR~10 ns in THz
A. Principi, et al. PRB, 2013, 88, 195405
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Properties of graphene plasmon: Electrical tunability Low intrinsic losses Broad band operation Suitability of on-chip integration High field enhancement for
strong light-matter interaction
T. Low, et al. ACS Nano, 2014, 8, 1086
J.N. Chen, et al. Nature, 2012, 487, 77
Graphene Plasmons
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Motivation & Objectives
SubstrateSubstrate
All atoms are exposed to the substrate
A small portion of atoms are exposed to substrate
Au Graphene
Substrate design for high performance GP
? Surface phonon mode hybridization
? Electron Scattering (dangling bond, impurities)
? Radiation loss (surface roughness)
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Near-field(s-SNOM)
Far-field extinction spectrum( FTIR)
Nanoribbon arrays to excite local plasmon;Extinction spectra obtained (675-4000 cm-1);Multi-modes characterization.
Experimental measurement of graphene plasmon
Metal-coated AFM tips to excite propagating plasmon (~15 nm);High-order demodulated harmonics of the near-field signals to obtain weak signals;
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Hybridization of GP and surface phonons
Free standing --- one peak; On silica substrate --- three peaks
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Graphene Plasmon coplanar coupling
Decrease of inter-ribbon spacing caused red shifts of plasmonic resonances
f is ribbon to period ratio
Coplanar coupling of GPs is verified by resonance red shift
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Plasmon resonance varied as inter-ribbon spacing
Ribbon to period ratio
Plasmon coupling strength on various Substrates
Ribbon to period ratio
Non-polar substrate results in stronger coplanar couplingX. Yang, et al. Small, 201400515
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Van der Waals heterostructures: for long lifetime
Plasmon-phonon hybrid modes: Long lifetime of phonons in monolayer
crystals; High field enhancement.Design of ultra-thin functional device: Combine functions of varied 2D
crystals; Excellent electrical properties.
G/BN heterostructure
Geim, et al. Nature, 2014
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Graphene/h-BN heterostructure
Graphene/monolayer h-BN/SiO2 Graphene/SiO2
1、 Peak 4 origins from the coupling with LO phonon of h-BN( 1370 cm-1);2、 the positions of Peaks 1 and 2 move slightly. (806, 820 cm-1)。 The linewidths become narrower.
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Wavenumber (cm-1)800 1200 1600 2000
-0.21 eV
-0.25 eV
-0.29 eV
-0.33 eV
EF=-0.35 eV
-0.15 eV
-0.1 eV
Ext
inct
ion (
%)
0.2
0.4
0.6
0.8
1.0
0
W=160 nmPeak1Peak2
Peak3 Peak4
1.2
Peak a
c
Peak4Peak3
Peak2
Peak1
d
Ext
inct
ion (
%)
a
Wavenumber (cm-1)800 1000 1200 1400
0.2
0.4
0.6
0.8
0
Peak gPeak b
Peak a
EF=-0.35 eV W=100 nm
Wavenumber (cm-1)700 800 900
b
Ext
inct
ion (
%)
0.2
0.4
0
0.6o-TO (h-BN)
(820 cm-1)SO1(SiO2)806 cm-1
Peak b
Peak1
Peak2
1600 1000
EF=-0.35 eV
55 nm75 nm
100 nm
110 nm
120 nm
130 nm
140 nm
160 nm
W=220 nm
Wavenumber (cm-1)
Ext
inct
ion (
%)
800 1200 1600 2000
0.4
0.8
1.2
1.6
2.0
2.4
2.8
0
Peak4Peak3Peak2
Peak1Out-of-plane TO phonon( 820 cm-1) of BN interact with graphene plasmon.
Graphene/h-BN heterostructure
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Graphene/h-BN heterostructure
For monolayer h-BN: 3 optical phonons
( ) 0qiT r
exp(i . )( ) ,
2
oTB oT
oTBN
en u qz
A
q rr
exp( . )( ) .
2
LB L
LBN
en u i qzi
A
q rr
Remote phonon scattering mechanism: effective electrical potential
1, in-plane LO phonon (1370 cm-1)
2, in-plane TO phonon (820 cm-1)
3, out-of-plane TO phonon (820 cm-1)
A new coupling mode: the o-TO phonon interact with plasmon.
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Fano resonanceEIT
Graphene/h-BN heterostructure
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Lifetime of the hybrid modes
lifetime of Fano peaks: t =2h/G
Lifetimes:Near BN phonon: ~1.6 ps; Far from phonons: ~100 fs;Near SiO2 phonon: ~180 fs;Without coupling: ~40 fs;For Ag LSP: ~10 fs.
1370 cm-1
Peak1 Peak2 Peak3 Peak4
Eres (cm-1)800 1200 1400 16001000
Life
time
(fs)
200
400
600
800
1000
1200
1400
0
1600
1800
GNR/SiO2
GNR/BNR
800 cm-1
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900 cm-1 980 cm-1960 cm-1940 cm-1920 cm-1 1000 cm-1
900 cm-1 940 cm-1 980 cm-1
G/BN heterostructure
G/SiO2 device
Near-field images
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900 cm-1
950 cm-1
1000 cm-1 0 50 100 150 200 250 300 350 400 450
0.2
0.4
0.6
0.8
1
1.2
1.4 1
2
3
4
5
6
7
89
101112
Amplitude A=26.8742
Propagating wave vector q1=0.077792
Decaying wave vector q2=0.002939
q2/q1=0.037781
Constant part=0.51909
sse=0.078434
x (nm)
Vo
ltag
e (
10-5
V)
0 100 200 300 400 500 600
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1
2
3
4
5
6
78
910
Amplitude A=28.1792
Propagating wave vector q1=0.062555
Decaying wave vector q2=0.0024063
q2/q1=0.038467
Constant part=0.46674
sse=0.048575
x (nm)
Vo
ltag
e (
10-5
V)
0 100 200 300 400 500 600 700
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.81
2
3
4
5
6
7
8 910
Amplitude A=86.3336
Propagating wave vector q1=0.049104
Decaying wave vector q2=0.0021745
q2/q1=0.044283
Constant part=0.74817
sse=0.21005
x (nm)
Vo
ltag
e (
10-5
V)
Plasmon wavelength: 260 nmIncident wavelength: 900 cm-1
Confinement: 43Lifetime: 73 fs
Plasmon wavelength: 180 nmIncident wavelength: 950 cm-1
Confinement: 59Lifetime: 66 fs
Plasmon wavelength: 140 nmIncident wavelength:1000 cm-1
Confinement: 72Lifetime: 54 fs
Near-field images
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Dispersion
Peak2
GNR/BNR
0.1 10
400
800
1200
1600
Life
time
(fs)
Group velocity (x0.01c)
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Graphene plasmon: electrical tunability & dielectric environment effect;
Substrate surface phonon effects on GP: Tradeoff between modulation bandwidth\coupling efficiency ;
Long lifetime hybrid modes of plasmon and phonon:Van der Waals heterostructures can improve plasmon lifetime significantly by combine the low loss and highly field enhancement.
Summary
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Acknowledgements
Thank you for your attention!
National Natural Science Foundation of China (NSFC)The Recruitment Program of Global Experts