Chemical Vapor Deposition Synthesis and Terahertz Photoconductivity of Low-Band-Gap N = 9 Armchair Graphene Nanoribbons

Article abstract of DOI:10.1021/jacs.7b00776

Recent advances in bottom-up synthesis of atomically defined graphene nanoribbons (GNRs) with various microstructures and properties have demonstrated their promise in electronic and optoelectronic devices. Here we synthesized N = 9 armchair graphene nanoribbons (9-AGNRs) with a low optical band gap of ～1.0 eV and extended absorption into the infrared range by an efficient chemical vapor deposition process. Time-resolved terahertz spectroscopy was employed to characterize the photoconductivity in 9-AGNRs and revealed their high intrinsic charge-carrier mobility of approximately 350 cm²·V^-1·s^-1

Full text of DOI:10.1021/jacs.7b00776

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Communication
Chemical vapor deposition synthesis and terahertz photoconductivity
of low-bandgap N = 9 armchair graphene nanoribbons
Zongping Chen, Hai I. Wang, Joan Teyssandier, Kunal S. Mali, Tim Dumslaff, Ivan Ivanov,
Wen Zhang, Pascal Ruffieux, Roman Fasel, Hans Joachim Räder, Dmitry Turchinovich, Steven
De Feyter, Xinliang Feng, Mathias Kläui, Akimitsu Narita, Mischa Bonn, and Klaus Müllen
J. Am. Chem. Soc., Just Accepted Manuscript • DOI: 10.1021/jacs.7b00776 • Publication Date (Web): 01 Mar 2017
Downloaded from http://pubs.acs.org on March 1, 2017
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Chemical vapor deposition synthesis and terahertz photoconductivity
of low-bandgap N = 9 armchair graphene nanoribbons
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Zongping Chen1, Hai I. Wang2, Joan Teyssandier3, Kunal S. Mali3, Tim Dumslaff1, Ivan Ivanov1, Wen
Zhang1, Pascal Ruffieux4, Roman Fasel4,5, Hans Joachim Räder1, Dmitry Turchinovich1, Steven De Feyꢀ
ter3, Xinliang Feng6, Mathias Kläui2, Akimitsu Narita*,1, Mischa Bonn*,1 and Klaus Müllen*,1,7
1Max Planck Institute for Polymer Research, Ackermannweg 10, Dꢀ55128 Mainz, Germany
2Institute of Physics, Johannes GutenbergꢀUniversity Mainz, Staudingerweg 7, 55128 Mainz, Germany
3Division of Molecular Imaging and Photonics, Department of Chemistry, KU Leuven Celestijnenlaan, 200 F, Bꢀ3001 Leuꢀ
ven, Belgium
4Empa, Swiss Federal Laboratories for Materials Science and Technology, nanotech@surfaces Laboratory, 8600 Dübendorf,
Switzerland
5Department of Chemistry and Biochemistry, University of Bern, 3012 Bern, Switzerland
6Center for Advancing Electronics Dresden and Department of Chemistry and Food Chemistry, Technische Universität
Dresden, Mommsenstrasse 4, Dꢀ01062 Dresden, Germany
7Institute of Physical Chemistry, Johannes GutenbergꢀUniversity Mainz, Duesbergweg 10ꢀ14, 55128 Mainz, Germany
Supporting Information Placeholder
mentally important, which is expected to provide GNRꢀbased
devices approaching the Shockley–Queisser limit.14 Nevertheless,
structurally wellꢀdefined GNRs with optical bandgaps in this
range still remain rather rare.5 The electronic structure of armchair
GNRs (nꢀAGNRs) has been shown to be extremely sensitive to
the ribbon width, and can be divided into three subfamilies with
atomic number N = 3n, 3n + 1, and 3n + 2 (n = 1, 2, 3, ...). All
three kinds of AGNRs are expected to be semiconducting. And
the bandgap of different subfamily AGNRs with the same n varies
as: 3n + 2 < 3n < 3n + 1.1ꢀ2 According to theoretical prediction by
GWꢀBSE calculations, N = 9 armchair graphene nanoribbons (9ꢀ
AGNRs) possess an optical bandgap of ~1.0 eV,15 which was very
recently corroborated by the solutionꢀmediated synthesis reported
by Dong et al.16 On the other hand, Nakae et al. previously proꢀ
posed a synthesis of 9ꢀAGNRs by a lowꢀpressure CVD method,12
but the observed optical bandgap was larger, and unambiguous
structural characterization has remained elusive.
ABSTRACT: Recent advances in bottomꢀup synthesis of atomiꢀ
cally defined graphene nanoribbons (GNRs) with various microꢀ
structures and properties have demonstrated their promise in
electronic and optoelectronic devices. Here we synthesize N = 9
armchair graphene nanoribbons (9ꢀAGNRs) with a low optical
bandgap of ~1.0 eV and extended absorption into the infrared
range by an efficient chemical vapor deposition process. Time
resolved terahertz spectroscopy has been employed to characterize
the photoconductivity in 9ꢀAGNRs, and revealed their high intrinꢀ
sic chargeꢀcarrier mobility of approximately 350 cm2·V–1·s–1.
Graphene nanoribbons (GNRs), quasiꢀoneꢀdimensional graꢀ
phene strips, have attracted much attention as a new class of
semiconducting materials for various applications in electronic
and optoelectronic devices.1ꢀ6 In the past few years, various types
of GNRs have been synthesized via bottomꢀup approaches in
solution as well as on metal surfaces3ꢀ11 with a wide range of
bandgap energies. Among the different bottomꢀup methods, onꢀ
surface synthesis, especially through chemical vapor deposition
(CVD) appears to be highly promising, as being capable of highꢀ
throughput and scalable growth of structurally defined GNRs at
low cost.6, 8, 12 The surfaceꢀgrown GNR films can be readily transꢀ
ferred onto arbitrary substrates, allowing for optical characterizaꢀ
tions and device integration. However, the performance of fieldꢀ
effect transistor (FET) devices fabricated with such GNRs have so
Here we report an efficient CVD process for inexpensive highꢀ
throughput growth of structurally defined 9ꢀAGNRs. The obꢀ
tained 9ꢀAGNRs exhibit a low optical bandgap of ~1.0 eV with
broad absorption up to ~1200 nm. Ultrafast optical pump ꢀ THz
probe spectroscopy (OPTP) is for the first time applied to surfaceꢀ
synthesized GNRs, revealing high intrinsic chargeꢀcarrier mobiliꢀ
ty of 9ꢀAGNRs, i.e., approximately 350 cm2·V–1·s–1, which reꢀ
flects the high quality of the sample fabricated by our CVD methꢀ
od. The potential of 9ꢀAGNRs for future optoelectronics has been
further demonstrated in comparison with previously reported 7ꢀ
AGNRs and chevronꢀtype GNRs, showing higher photoconducꢀ
tivity by a factor of 1.2 and 2.5, respectively.
8, 10, 12ꢀ13
far been compromised by a huge contact resistance,6,
hampering the investigations of their intrinsic electronic transport
properties.
We have recently reported an efficient ambientꢀpressure CVD
growth of 7ꢀAGNRs and chevronꢀtype GNRs.6 Notably, the
CVDꢀgrown GNRs demonstrated structural perfection well comꢀ
For efficient optoelectronic applications such as photovoltaics,
GNRs with an optical bandgap between 1.0 to 1.3 eV are fundaꢀ
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parable with GNRs synthesized under ultraꢀhighꢀvacuum condiꢀ
tions. Because of the high versatility, our CVD process provides
access to a broad class of GNRs with designed structures, by
employing different oligophenylene monomers. The synthesis of
9ꢀAGNRs has been achieved by CVD using 3',6'ꢀdibromoꢀ
1,1':2',1''ꢀterphenyl (DBTP) as the monomeric building block
(Figure 1). In a typical CVD experiment, DBTP is sublimed at
135ꢀ150 °C and deposited on the Au/mica substrate kept at 200
°C. At this temperature DBTP is simultaneously dehalogenated,
generating biradicals that subsequently undergo a coupling reacꢀ
tion to form oligo(diphenylꢀpꢀphenylene) (ODPP) with a linear
backbone (Figure 1a). The sample is subsequently annealed at a
higher temperature of 400 °C to transform ODPPs into 9ꢀAGNRs
through the surfaceꢀassisted intramolecular cyclodehydrogenation,
eliminating 8 hydrogens per repeating unit.
growth and solution synthesis.12,
The monolayers of asꢀ
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16
synthesized 9ꢀAGNRs were further unambiguously characterized
using atomic force microscopy (AFM) as well as scanning tunnelꢀ
ing microscopy (STM) under ambient conditions (Figures 2 and
S3). AFM height images show terraces of Au(111) surface uniꢀ
formly covered with monolayer thick (~2.5 Å) film of 9ꢀAGNRs
(Figure 2a). STM images agree well with AFM data indicating
good surface coverage of striped features (Figure 2b). Typical
domain size is ~30 nm. Each terrace of Au(111) contains multiple
domains of 9ꢀAGNRs indicating several nucleation sites along
each terrace. Wellꢀdefined domains of planar striped features are
sometimes surrounded by illꢀdefined regions which may indicate
adsorption of unreacted material. The width of each striped feaꢀ
ture is ~1.2 nm and it is uniform across the surface (Figure 2c, d).
This is in good agreement with the expected width of 9ꢀAGNRs
estimated from a molecular mechanics model (Figure 2e) and
further indicates that the 9ꢀAGNRs remain parallel (faceꢀon) to
the Au(111) surface. The 9ꢀAGNRs appear continuous and closeꢀ
packed within each domain. While the STM images provided in
Figure 2 reveal GNRs with length up to ~20 nm, the length can
reach up to 30ꢀ35 nm (see Figure S3).
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a
200 °C
400 °C
Br Br
H
H
H
H
n
n
DBTP
100
ODPP
9-AGNRs
b
x186
0
1250
1750
2250
2750
3250
G
3750
4250
4750
5250
5750
m/z(Da)
c
700
Edge C-H
600
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400
300
200
9-AGNRs
D
RBLM
4
6
8
10
12
N
400
800
1200
1600
2000
2400
2800
3200
Raman shift (cm-1
)
Figure 1. (a) Synthesis of 9ꢀAGNRs by CVD method. (b) Mass
spectrum of ODPPs before cyclodehydrogenation. (c) Raman
spectrum of CVDꢀgrown 9ꢀAGNRs by 785 nm laser. The calcuꢀ
lated RBLM peaks vs. width of GNRs are given in the inset.17
To investigate the chemical structures of the oligomer/polymer
after the radical polymerization step during the onꢀsurface syntheꢀ
sis of GNRs, we have recently developed a quick and powerful
surfaceꢀmassꢀspectrometry analysis method.6 ODPPs were thus
studied by the highꢀresolution matrixꢀassisted laser desorpꢀ
tion/ionization timeꢀofꢀflight mass spectrometry (MALDIꢀTOF
Figure 2. AFM/STM characterization of 9ꢀAGNRs on
Au(111)/Mica surface. (a) AFM height image showing domains
of 9ꢀAGNRs. The inset shows height profile along the black line,
indicating formation of monolayer of 9ꢀAGNRs. (b) STM image
showing domains of 9ꢀAGNRs. (Iset = 300 pA; Vbias = 0.06 V) (c)
Smallꢀscale STM image showing 9ꢀAGNRs as wellꢀdefined
stripes with uniform width of ~1.2 nm. (Iset = 60 pA; Vbias = 0.03
V) (d) Line profile along the white line in panel (c). (e) Molecular
model showing the laterally stacked 9ꢀAGNRs.
MS)
with
transꢀ2ꢀ[3ꢀ(4ꢀtertꢀbutylphenyl)ꢀ2ꢀmethylꢀ2ꢀ
propenylidene] malononitrile (DCTB) as matrix (Figure 1b). The
MS spectrum of the ODPPs exhibits regular patterns from penꢀ
tamer (m/z = ~1142 Da) up to a species with 23 units (m/z =
~5257 Da). The difference between the neighboring signals is
exactly the same value of ~228 Da, which corresponds to the
molecular mass of the repeating unit. The observed isotopic disꢀ
tribution of the ODPPs is in agreement with the simulated pattern,
demonstrating the successful polymerization reaction to form the
expected structures (Figure S1).
The Raman spectrum of the final 9ꢀAGNRs after cyclodehyꢀ
drogenation reveals four main peaks at 1592, 1340, 1250, and 315
cm–1, which can be assigned to D, G, Edge CꢀH, and radial
breathingꢀlike mode (RBLM) peaks, respectively (Figures 1c and
S2).18 The sharp and intense widthꢀspecific RBLM peak is in
excellent agreement with the DFT calculation, demonstrating the
high uniformity in width of the obtained 9ꢀAGNR sample (inset
of Figure 1c).17 Note that the specific RBLM peak of 9ꢀAGNRs
was not observed in previous reports on 9ꢀAGNRs by CVD
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a
b
tudes increasing with the frequencies, sharing a large similarity
H
H
n
Re
0.0010
with the frequencyꢀresolved THz conductivity in semiconducting
polymers21ꢀ23 and other types of GNRs dispersed in organic solꢀ
vents.4 The DrudeꢀSmith model24 has been widely employed to
model the transport characteristic in conducting polymers and
GNRs as:
9-AGNRs
~1.0 eV
H
H
n
0.0005
0.0000
-0.0005
-0.0010
~1.6 eV 7-AGNRs
H
H
n
Chevron-GNRs
9-AGNRs
7-AGNRs
Chevron
~1.7 eV
ꢃꢄꢅꢆꢇꢈ
Im
1
ꢋ
ꢀꢁꢂ
=
ꢊ1 +
ꢌ
400
800
1200
1600
2000
-1
0
2
3
4
5
1 − ꢉꢅꢈ
1 − ꢉꢅꢈ
Pump probe delay (ps)
Wavelength (nm)
d
c
9
Here, ε0 is the vacuum permittivity, ωp is the plasma frequency
(which is proportional to the carrier concentration), τ is the elecꢀ
tron momentum scattering time, and the parameter c accounts for
the correlation between carrier momentum before and after a
scattering event, with c = 0 as nonꢀpreferential, fully isotropic
scattering (classical Drude model of free electron plasma) and c =
–1 as backscatteringꢀdominant process of localized charge carrier.
By fitting the complex conductivity using the DrudeꢀSmith model
as shown in Figure 3c, we can obtain c parameter ~ꢀ0.72 ± 0.02,
which is fully consistent with previous reported c values in ranꢀ
domly oriented 1D Drude conductors, such as carbon nanotubes
and GNRs in dispersions.20 Based on the fitting, we can also
derive the momentum scattering time to be 20 ± 5 fs. Applying
the reported effective mass for the 9ꢀAGNRs (m* = 0.1·m0),10 one
can readily estimate the intrinsic dc carrier mobility in 9ꢀAGNRs
using µ = eτ/m*, which results in a value of 352 ± 88 cm2·V–1·s–1.
This is a rough estimation of the local carrier mobility within a
nanoribbon. The physical length of the molecular wire has been
reported to affect its charge mobility due to the charge scattering
effect at the ends of the molecular wires.25 Consequently, controlꢀ
ling the growth conditions for producing even longer 9ꢀAGNRs
than those reported here (up to ~35 nm) could be beneficial for
further boosting the highꢀfrequency carrier mobility of 9ꢀAGNRs
for device applications. Speaking of the measured photoconducꢀ
tivity of the sample, we can also estimate carrier mobility in the
film of 25 layers of GNR networks – a film of GNR chains intriꢀ
cately connected with each other. This can be estimated from
average measured conductivity and the quantum yield (which in
the similar materials are found to be QE = 10–3–10–5).22 Thus, the
mobility in the film is comparable to 50–5000 cm2·V–1·s–1, which
indicates the high quality of the CVDꢀgrown GNRs used in this
study. We expect a negligible effect of sample thickness on the
mobility estimate for samples consisting of a large number of
layers, such as 25 layers in this study (see Supporting Information
for extended discussion). Note that this intrinsic chargeꢀcarrier
mobility estimated for 9ꢀAGNRs is much higher than the mobility
measured in FET devices on thin films of 7ꢀAGNRs and chevronꢀ
type GNRs (estimated to be ~10ꢀ3ꢀ10ꢀ5 cm2Vꢀ1sꢀ1),6, 12 since the
electrical response in the GNR FET devices is mostly dominated
by the large interꢀGNR junction resistances as well as the contact
resistance between the GNRs and the electrodes.
9-AGNRs
7-AGNRs
Chevron
0.12
0.09
0.06
0.03
0.00
-0.03
-0.06
2.0x10-21
10
11
12
13
14
15
16
17
Drude-Smith fitting
Data
Re
Im
1.0x10-21
0.0
0.5
1.0
1.5
2.0
0
1
2
3
4
5
Pump probe delay (ps)
Frequency (Thz)
Figure 3. (a) UVꢀvisꢀNIR absorption spectra of different CVDꢀ
grown GNRs. The inset shows the chemical structures of the
GNRs and their optical bandgaps. (b) Timeꢀresolved photoinꢀ
duced real and imaginary conductivity of 9ꢀAGNRs measured as
the relative change of THz transmission at the peak of THz pulse
(real, solid line) and zeroꢀcrossing point of THz pulse (imaginary,
dotted line) (pump at 400 nm, with fluence 200 ꢁJ/cm2). (c) Freꢀ
quencyꢀresolved THz conductivity of 9ꢀAGNRs measured at the
peak of the photoconductivity, and a DrudeꢀSmith fit with c paꢀ
rameter ~ꢀ0.72 ± 0.02. (d) Comparative study of THz photoconꢀ
ductivities of different GNR structures.
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After the growth, the 9ꢀAGNRs can be readily transferred to
other substrates, yielding a largeꢀarea uniform GNR film, as
demonstrated by the optical images and Raman mapping (Figure
S4). The UVꢀvisꢀNIR absorption analysis of the 9ꢀAGNRs was
carried out by multiple transfer of 9ꢀAGNR films on one fused
silica substrate to have enough optical density (Figure 3a). An
absorption onset was thus detectable at ~1185 nm in the IR reꢀ
gion, suggesting an optical bandgap of ~1.0 eV for the obtained 9ꢀ
AGNR multilayer film, which is close to the theoretical value of
isolated 9ꢀAGNR,15 and significantly smaller than values of 7ꢀ
AGNRs (~1.6 eV) and chevronꢀtype GNRs (~1.7 eV) (see Figures
3a and S5).
For assessing the potential of the 9ꢀAGNRs for optoelectronics,
we have investigated their photoconductivity by OPTP,19 which
has been demonstrated as a powerful spectroscopic tool for conꢀ
tactꢀfree and noninvasive characterization of the intrinsic chargeꢀ
carrier mobility within individual solutionꢀsynthesized GNRs.4ꢀ5,
20
In Figure 3b, we show the timeꢀresolved photoconductivity
dynamics (in a form of transient change of the THz transmission)
of a thin film of 25 layers of 9ꢀAGNRs deposited on fused silica.
After photoexcitation with the optical pulse (400 nm wavelength),
we observe a subꢀpicosecond rapid rise and a subsequent, ~2 ps ꢀ
fast decay in the real conductivity. The imaginary conductivity
component displays a similarly fast riseꢀtime, however the decay
time is considerably longer. Both the transient conductivity dyꢀ
namics and their time scale are fully consistent with our previous
studies on solutionꢀsynthesized GNRs in dispersions4ꢀ5, 20 and can
be rationalized by the charge state transitions from quasiꢀfree
cases at early time (< 1 ps) to strongly bounded excitons at the
longer timeꢀdelays (> 2 ps with longꢀlived imaginary conductivity
indicative of photoinduced dielectric polarizability of the sample).
Furthermore, the frequencyꢀdependent THz conductivity at the
peak position of the dynamics shown in Figure 3b (~0.55 ps after
photoexcitation), is demonstrated in Figure 3c. We observe a
positive real and negative imaginary component with both ampliꢀ
To establish the potential of 9ꢀAGNRs for optoelectronic appliꢀ
cations, we have conducted a further comparative investigation of
photoconductivity for two other CVDꢀgrown GNRs with certain
structural similarities: namely, 7ꢀAGNRs and chevronꢀtype GNRs
(see Figure 3a). By selectively exciting the samples with a fixed
pump fluence at 400 nm, we have compared the photonꢀinduced
THz conductivity for all three GNR structures as shown in Figure
3d. As we can see, for a given excitation fluence and optical
density (OD), the photoconductivity of 9ꢀAGNRs is a factor of
1.2 and 2.5 higher than that of 7ꢀAGNRs and chevronꢀtype GNRs,
respectively, which can be partially attributed the relatively smallꢀ
er electron effective mass, leading to a higher mobility, of 9ꢀ
AGNRs than that of the rest GNRs.10, 26ꢀ27
In summary, a synthesis of structurally wellꢀdefined 9ꢀAGNRs
has been achieved through a highly efficient CVD method. STM,
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(5)
Narita, A.; Verzhbitskiy, I. A.; Frederickx, W.; Mali, K. S.;
Raman, UVꢀvisꢀNIR absorption, and time resolved THz spectrosꢀ
copy analysis manifested the high quality of the 9ꢀAGNRs with a
low bandgap of ~1.0 eV and absorption extending up to ~1200
nm. Given the scalability and low cost of the CVD synthetic
method, these results pave the way for exploiting such bottomꢀup
synthesized GNRs for efficient optoelectronic device applications,
including visible ꢀ to ꢀ infrared photodetectors and photovoltaics.
Jensen, S. A.; Hansen, M. R.; Bonn, M.; De Feyter, S.; Casiraghi, C.;
Feng, X.; Müllen, K. ACS Nano 2014, 8, 11622ꢀ11630.
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Chen, Z.; Zhang, W.; Palma, C.ꢀA.; Lodi Rizzini, A.; Liu, B.;
Abbas, A. N.; Richter, N.; Martini, L.; Wang, X.ꢀY.; Cavani, N.; Lu, H.;
Mishra, N.; Coletti, C.; Berger, R.; Klappenberger, F.; Kläui, M.; Candini,
A.; Affronte, M.; Zhou, C.; De Renzi, V.; del Pennino, U.; Barth, J. V.;
Räder, H. J.; Narita, A.; Feng, X.; Müllen, K. J. Am. Chem. Soc. 2016,
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(7)
Ruffieux, P.; Wang, S.; Yang, B.; SánchezꢀSánchez, C.; Liu, J.;
ASSOCIATED CONTENT
Supporting Information
9
Dienel, T.; Talirz, L.; Shinde, P.; Pignedoli, C. A.; Passerone, D.;
Dumslaff, T.; Feng, X.; Müllen, K.; Fasel, R. Nature 2016, 531, 489ꢀ492.
(8)
2017, 9, 57ꢀ63.
(9)
Rev. 2015, 44, 6616ꢀ6643.
(10)
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Sakaguchi, H.; Song, S.; Kojima, T.; Nakae, T. Nature Chem.
Experimental details and more characterization data: MALDIꢀ
TOF MS, Raman spectra and AFM/STM images.
The Supporting Information is available free of charge on the
ACS Publications website at DOI: .
Narita, A.; Wang, X. Y.; Feng, X. L.; Müllen, K. Chem. Soc.
Talirz, L.; Ruffieux, P.; Fasel, R. Adv. Mater. 2016, 28, 6222ꢀ
6231.
(11)
Talirz, L.; Söde, H.; Dumslaff, T.; Wang, S.; Sanchezꢀ
AUTHOR INFORMATION
Corresponding Author
Valencia, J. R.; Liu, J.; Shinde, P.; Pignedoli, C. A.; Liang, L.; Meunier,
V.; Plumb, N. C.; Shi, M.; Feng, X.; Narita, A.; Müllen, K.; Fasel, R.;
Ruffieux, P. ACS Nano 2017, DOI: 10.1021/acsnano.1026b06405.
*narita@mpipꢀmainz.mpg.de
*bonn@mpipꢀmainz.mpg.de
*muellen@mpipꢀmainz.mpg.de
Notes
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The authors declare no competing financial interests.
Shockley, W.; Queisser, H. J. J. Appl. Phys. 1961, 32, 510ꢀ
ACKNOWLEDGMENT
Prezzi, D.; Varsano, D.; Ruini, A.; Marini, A.; Molinari, E.
This work was financially supported by DFG Priority Program
Graphene SPP 1459, the Max Planck Society, the Office of Naval
Research BRC Program, the Swiss National Science Foundation,
and the European Commission through the FETꢀProactive Project
“MoQuaS” (FP7ꢀICTꢀ2013ꢀ10, contract number 610449), EU
CIG (334324 LIGHTER), and Graphene Flagship.
Li, G.; Yoon, K.ꢀY.; Zhong, X.; Zhu, X.; Dong, G. Chem.ꢀEur.
Zhou, J.; Dong, J. Appl. Phys. Lett. 2007, 91, 173108.
Saito, R.; Furukawa, M.; Dresselhaus, G.; Dresselhaus, M. S. J.
Ulbricht, R.; Hendry, E.; Shan, J.; Heinz, T. F.; Bonn, M. Rev.
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Table of Contents
1
2
3
Real
0.12
0.0010
0.0005
0.0000
-0.0005
-0.0010
4
5
0.08
6
7
Drude-Smith fitting
Data
Real
Imag
Real
Imag
0.04
0.00
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Imag
0
-0.04
-1
1
2
3
4
5
0.5
1.0
1.5
2.0
Pump probe delay (ps)
Frequency (Thz)
5
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