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Nanochemistry, Plasmonics,
and Correlated Imaging
Integrated IR Nanocharacterization with Inspire
PS
PMMA
Si
Inspire – New Capabilities for New Discoveries
•
A first of its kind nanoscale mapping system
•
•
Nanochemical properties – from SPIR
•
Infrared (IR) reflection and absorption
•
10 nm spatial resolution – 1000x beyond diffraction limit
•
Monolayer thickness sensitivity
Nanomechanical properties – from PeakForce QNM
•
•
Nanoelectrical properties – from KPFM, SCM
•
•
PS
Work function, conductivity
PHBV
With a broad range of applications
•
•
Stiffness, adhesion, etc.
Polymers, thin films, graphene, …
In an easy to use integrated package
•
No additional sample preparation – all AFM samples work!
•
Simple, quick, automated optical alignment
•
Meaningful results – reflection and absorption
10/22/2014
Bruker
2
Inspire – unambiguous nanoscale
chemical mapping
4 microns
Height
Reflection
Height
Reflection
Phase
Absorption
Phase
Absorption
1759 cm-1
1736 cm-1
PS PMMA
•
Spatio-spectral imaging with a QCL on PS-PMMA polymer:
•
Reflection shows material contrast at any frequency
•
Absorption shows PMMA C=O stretch on resonance
10/22/2014
Bruker
3
Inspire – monolayer sensitivity
From graphene to organic semiconductors
•
•
Graphene in absorption
@ 870 cm-1
Individual pentacene monolayers show up in
non-resonant reflection
3D overlay of height and IR
reflection @ 1900 cm-1
Max
Min
3.3um
500 nm
10/22/2014
Bruker
4
PeakForce IR
Simultaneous mapping of nanochemistry and quantitative
nanomechanics, with the full power of PeakForce QNM.
Peak Force QNM:
Approach
Withdraw
PeakForce IR combines
SPIR and PeakForce QNM
Correlated
nanochemicalnanomechanical
imaging with
PeakForce IR:
LDPE domains in PS
matrix. The
domains are seen
to protrude, have
lower modulus,
similar adhesion,
and be chemically
distinct from the
matrix. All this
information was
obtained
simultaneously!
Please see Jan 2014 AFM webinar for more information:
http://www.bruker.com/service/education-training/webinars/afm.html
10/22/2014
Bruker
1 mm
Height
Adhesion
Modulus
Chemistry
PS
LDPE
5
Exclusive Measurement Breadth
Combine IR nanochemical mapping with Bruker exclusive
electrical measurements including mV level workfunction
measurements and conductivity on soft samples.
PeakForce IR:
SPIR imaging, here
shown for graphene at
1730cm-1, showing the
expected layer ordering
in universal
conductivity regime’
15 mm
1 mm
Height
Inspire provides the widest set of
new & exclusive capabilities.
What will you discover?
10 nm
750 nm
Conductivity
PeakForce TUNA
conductivity imaging,
shown here on
vertically standing
carbon nanotubes.
Impossible with
contact mode.
10/22/2014
PeakForce QNM
nanomechanical
imaging with
atomic defect
resolution, shown
here on calcite.
PeakForce KPFM
work function imaging with
mV sensitivity, here shown
for reduced graphene
oxide. Revealing <20nm
potential variations due to
chemical heterogeneity.
Bruker
6
Introducing Inspire
Introduction to the Technique
PS-PMMA: Absorption at 1730cm-1, 5 micron image.
10/22/2014
Bruker
7
Why is infrared spectroscopy useful?
Example: PMMA infrared
spectrum shows absorption lines:
Bruker Tensor
Duan G. et. al. Nanoscale Res. Lett. (2008)
BUT:
Such spectra can be acquired using Bruker
FTIR instruments such as the Tensor
PMMA
polymer
IR absorption provides chemical
fingerprint + IR light is sensitive
to molecular vibrations, lattice
vibrations, plasmons…
Far-field spectroscopy is limited in spatial resolution to ~10 mm
Does not provide simultaneous reflection!
10/22/2014
Bruker
8
But nanoscale IR imaging is useful!
Semiconductors
Polymers
PS-b-P2VP
~2 mm spot7.5um x 7.5um
7.5um
A.J. Huber et. al. NanoLett 2008
M. Raschke et. al. ChemPhysChem
50nm x2005
50nm
Biology: Tobacco Mosaic Virus
Geology: comet dust
BN: phonon polaritons
940cm-1
993cm-1
1043cm-1
1mm
M. Brehm et. al. Nano Lett 2006
10/22/2014
X. Xu et. al. Nat. Comm. 2014
Bruker
SEM
SNOM
Gainsforth et al. 44th Lunar and
Planetary Science Conference 2013
9
Scattering SNOM = SPIR
(Scanning Probe IR)
implementation in the Inspire
3
Interferometer
+++
---
1
1. IR laser light from
optics box is focused
by a lens onto a
metallized AFM tip
2
XYZ
2. AFM engages the
tip and scans a
sample in XYZ
10/22/2014
Bruker
3. IR light focused
on the tip creates
IR near fields in
the tip/sample gap
with field
enhancement
10
Scattering SNOM = SPIR
(Scanning Probe IR)
implementation in the Inspire
Interferometer
+++
---
7
5
6
XYZ
7. The tip’s radiated light
is collimated and directed
to an IR detector in the
optics box
10/22/2014
6. The same
focusing lens
collects the tip’s
radiated IR light
Bruker
5. The tip radiates IR light
a portion of which is
sensitive to the near fields
11
Scattering SNOM = SPIR
(Scanning Probe IR)
implementation in the Inspire
Interferometer
+++
---
7
5
Infrared absorption
and reflection!
6
XYZ
Imaging with
PeakForce QNM,
KPFM, …!
10/22/2014
Bruker
Localization to ~ 10 nm
(tip radius), independent
of l!
12
SPIR detection
𝑬𝒃𝒈
𝑬𝒏𝒇 +𝑬𝒃𝒈
Inside the
Interferometer
𝑬𝒏𝒇 +𝑬𝒃𝒈
Piezo-actuated Mirror
MCT Detector Voltage:
Contains nanoscale information
10/22/2014
Bruker
13
SPIR detection
Tip tapping to extract near-field
information from scattering signal:
Inside the
Interferometer
𝑬𝒏𝒇 +𝑬𝒃𝒈
FFT
height
time
Piezo-actuated Mirror
𝑉𝑑𝑒𝑡 ∝ 𝐸𝑟𝑒𝑓 𝐸𝑛𝑓 cos 𝜑𝑟𝑒𝑓 − 𝜑𝑛𝑓 + 𝐸𝑏𝑔𝐸𝑛𝑓 cos 𝜑𝑏𝑔 − 𝜑𝑛𝑓 + 𝐸𝑟𝑒𝑓𝐸𝑏𝑔 cos 𝜑𝑟𝑒𝑓 − 𝜑𝑏𝑔
Isolated at higher harmonics
and amplified by large Eref
+ 𝐸𝑟𝑒𝑓 2 + |𝐸𝑛𝑓 |2 + |𝐸𝑏𝑔|2
Negligible
compared to Eref
 Allows phase sensitive
measurement!
10/22/2014
Bruker
Suppressed at
higher harmonics
14
SPIR detection
Tip tapping to extract near-field
information from scattering signal:
Inside the
Interferometer
𝑬𝒏𝒇 +𝑬𝒃𝒈
FFT
height
time
Piezo-actuated Mirror
𝑉𝑑𝑒𝑡 ∝ 𝐸𝑟𝑒𝑓 𝐸𝑛𝑓 cos 𝜑𝑟𝑒𝑓 − 𝜑𝑛𝑓
Isolated at higher harmonics
and amplified by large Eref
 Allows phase sensitive
measurement!
10/22/2014
Choose 𝜑𝑟𝑒𝑓 to sample the IR
near field response, 𝑬𝒏𝒇:
𝜑𝑟𝑒𝑓 = 0
𝜑𝑟𝑒𝑓 = π/2
Bruker
Reflection
Absorption
15
SPIR with Inspire
Effect of a resonance on Absorption
On Carbonyl resonance, IR laser ω = 1730cm-1
Off Carbonyl resonance, IR laser ω = 1760cm-1
10nm
+++
𝜑𝑟𝑒𝑓 = π/2
+++
---
𝜑𝑟𝑒𝑓 = π/2
--By measuring “out of phase”
Inspire detects Absorption
with 10nm resolution
C=O
10/22/2014
Enables nanoscale chemical
identification
Bruker
C=O
16
SPIR with Inspire
Effect of a resonance on Reflection
On Carbonyl resonance, IR laser ω = 1720cm-1
Off Carbonyl resonance, IR laser ω = 1760cm-1
10nm
+++
𝜑𝑟𝑒𝑓 = 0
+++
---
𝜑𝑟𝑒𝑓 = 0
--By measuring “in phase”
Inspire detects Reflection
with 10nm resolution
C=O
10/22/2014
Information beyond ChemID:
Film Thickness
Conductivity
Plasmonics
Bruker
C=O
17
Beyond absorption: reflection spectrum
provides additional information
Graphene
Metal-to-insulator
50nm x 50nm
transitions
324K
reflection
absorption
328K
Polymers and other chemicals
reflection
Liu et al. Phys Rev Lett 2013
Bruker
Simultaneous reflection AND
absorption enables
characterization of virtually
any material!
absorption
10/22/2014
Bruker
18
Introducing Inspire
Demonstration of Capabilities
Cross-section of a Glass Optical Fiber :Reflection at 1900cm-1, 5 micron image.
10/22/2014
Bruker
19
10nm-resolved IR reflection map
10 microns
1 micron
250 nm
10nm spatial resolution:
Resolving 10nm features in IR reflection at
1933cm-1 on Si/SiO2 grating.
10/22/2014
10nm
Bruker
20
Simultaneous reflection AND
absorption mapping
• On resonance with IR fingerprint
•
IR reflection AND absorption at 10nm resolution
•
Simultaneously acquired in tapping mode (or PFT)
PS
Height
PMMA
On resonance
Phase
2um
Reflection
10/22/2014
Absorption
Bruker
C=O
21
Simultaneous reflection AND
absorption mapping
• Off resonance with IR fingerprint
•
Absorption channel disappears
•
Reflection channel provides material contrast across entire IR range
PS PMMA
Height
Off resonance
Phase
2um
Reflection
Contrast..
Absorption
C=O
No Contrast..
Reflection channel is less specific but enables
identification over a wider spectral range
10/22/2014
Bruker
22
Inspire – Sensitivity to phase
changing materials
CD-RW media
Height
DVD-RW media
Height
Reflection
Reflection
5um
15um
• Lower reflection reveals amorphous regions
• Topography free contrast demonstrated
10/22/2014
Bruker
23
PeakForce IR: simultaneous
nanomechanical and optical imaging
QNM images of PS/LDPE blend
Height
Simultaneous IR
Adhesion
IR Reflection
Re(rp)
0.16
Modulus
Deformation
0.04
PS
Re(rp) ~ 0.12
LDPE
Re(rp) ~ 0.07
PeakForce IR - the only method for simultaneous, quantitative,
nanomechanical AND nanooptical characterization
10/22/2014
Bruker
24
PeakForce IR: simultaneous
nanomechanical, electrical
and optical imaging
Aluminum
Silicon
Gold
Height
Height
Adhesion
Adhesion
Potential
Potential
Reflection
Reflection
Charged Particle?
20um
10/22/2014
Bruker
25
Sample compatibility: equally effective
on Organic or Inorganic samples
Imaging organic
materials
Height
Ps-b-PMMA block
copolymer, PMMA
shows IR absorption
at 1725 cm-1.
IR Absorption
Imaging multiple
inorganic materials
Showing location of Si vs
SiO2 as well as small
contamination specks. IR
reflection at 1900cm-1.
Si
SiO2
Revealing PS
matrix, LDPE
inclusion, and
exposed Si
substrate. IR
reflection at
1028cm-1.
PS
Si
LDPE
7 mm
500 nm
7 mm
Height
Distinguishing
multiple organic
materials and
inorganic
substrate
IR Reflection
Direct optical mapping, not requiring
photothermal response, no special sample
preparation, works even on samples not
conducive to contact or Tapping mode.
Imaging embedded organic/inorganic materials
Clearly identifying the cross sectioned fiber by its higher
reflectivity compared to the matrix and droplets of epoxy. IR
reflection at 1900cm-1.
10/22/2014
Bruker
26
SPIR characterization
of Graphene
Calculated SPIR spectrum of Graphene
What does SPIR reveal
about Graphene?
2Ef±Γ
Plasmonics
Reflection
Carrier density – 2Ef
position
Absorption
Defects – Γ,
conductivity floor
Universal
Conductivity
Ef = 700cm-1, Γ = 30cm-1
10/22/2014
Number of layers –
universal conductivity
level
For a description of Graphene’s infrared conductivity see
Z.Q. Li et. al. “Dirac Charge dynamics in graphene by infrared spectroscopy”
Bruker
27
SPIR characterization of Graphene
Universal Conductivity regime
Calculated SPIR spectrum of Graphene
Reflection
Absorption
1730cm-1
For a description of Graphene’s infrared conductivity see
Z.Q. Li et. al. “Dirac Charge dynamics in graphene by infrared spectroscopy”
10/22/2014
Bruker
28
Inspire: optical characterization of
Graphene in Universal Cond. Regime
AFM
Reflection 1730cm-1
KPFM
10nm resolution
Reflection image
at 1900cm-1
4
SiO2
~50mV
10/22/2014
2
3
1
Bruker
29
Inspire: optical characterization of
Graphene - defect detection
Nanomechanics shows signs of wrinkles
IR Reflection
1900cm-1
2%lower
lower
2%
SPIR
reflection
signal
consistent with
higher defect
concentration
Hint of
defects in
D-band
Raman
10/22/2014
Bruker
30
SPIR characterization of Graphene
Plasmonic regime
Calculated SPIR spectrum of Graphene
Reflection
Absorption
870cm-1
For a description of Graphene’s infrared conductivity see
Z.Q. Li et. al. “Dirac Charge dynamics in graphene by infrared spectroscopy”
10/22/2014
Bruker
31
SPIR characterization of Graphene
Plasmonic regime
Coupling to high momenta…
Fei,
Andreev,
Nano Lett.
11, 4701
(2011)
10/22/2014
Bruker
32
SPIR characterization of Graphene
Plasmonic regime
Coupling to high momenta…
Fei,
Andreev,
Nano Lett.
11, 4701
(2011)
Ju, Nat. Mater.
6, 630 (2011)
…via nanostructuring
10/22/2014
Bruker
33
SPIR characterization of Graphene
Plasmonic regime
Coupling to high momenta…
Fei,
Andreev,
Nano Lett.
11, 4701
(2011)
…via s-SNOM
10/22/2014
Bruker
34
SPIR characterization of Graphene
Plasmonic regime
Coupling to high momenta…
Example from scientific literature:
Fei,
Andreev,
Nano Lett.
11, 4701
(2011)
Plasmonic
interfence
…via s-SNOM
10/22/2014
Andreev G.O. et. al. APS 2011
Fei Z. et. al. Nature 2012
Chen J. et. al. Nature 2012
Bruker
35
SPIR characterization of Graphene
Plasmonic regime
Examples from Inspire
Example from scientific literature:
IR 870cm-1
Refl.
Abs
Plasmonic
interfence
Andreev G.O. et. al. APS 2011
Fei Z. et. al. Nature 2012
Chen J. et. al. Nature 2012
500 nm
10/22/2014
Bruker
36
Imaging Graphene plasmons with
market leading scan speeds
~140nm
• 10Hz image obtained in
just 30s
• No significant loss of
spatial resolution
• No sample damage
1Hz
10/22/2014
4Hz
10Hz
Bruker
• Impossible without the
stability of Bruker AFM
technology and near
field optical imaging of
Inspire
37
Inspire – New Capabilities for New Discoveries
•
A first of its kind nanoscale mapping system
•
•
Nanochemical properties – from SPIR
•
Infrared (IR) reflection and absorption
•
10 nm spatial resolution – 1000x beyond diffraction limit
•
Monolayer thickness sensitivity
Nanomechanical properties – from PeakForce QNM
•
•
Nanoelectrical properties – from KPFM, SCM
•
•
PS
Work function, conductivity
PHBV
With a broad range of applications
•
•
Stiffness, adhesion, etc.
Polymers, thin films, graphene, …
In an easy to use integrated package
•
No additional sample preparation – all AFM samples work!
•
Simple, quick, automated optical alignment
•
Meaningful results – reflection and absorption
10/22/2014
Bruker
38
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