Scanning Nanoelectrochemistry and Nanoelectrical Liquid Imaging with Nanoelectrode Probe
Teddy Huang, PhD Sr. Applications Scientist, Bruker Nano Surfaces, [email protected]
Outline
• Overview
• Nanoelectrode Probe
• AFM-SECM
• PeakForce SECM
• Force Volume SECM
• Contact Mode SECM
• Tapping Mode SECM
• Nanoelectrical Measurements in Liquid
• Conductive AFM
• PFM: Nano-Electromechanics
• Kelvin Probe Force Microscopy
• Conclusion
11/15/2017 2 Bruker Confidential
Pt
SiO2
r ~ 25 nm
h ~ 250 nm
Success from Collaboration
11/15/2017 3 Bruker Confidential
Applications Collaborators
PeakForce SECM
PF-TUNA in Liquid
Solar Fuels
Surface Chemistry
JCAP/Caltech
Universität Bayreuth (Germany)
CCI Solar
University of Oregon
University of Leeds (UK)
Battery
Brown University
General Motors R&D
Fujian Normal University (China)
Force Volume SECM Stanford University
Industrial Companies in China
PFM in Liquid East China Normal University
• Nanoelectrode Probe
• Scanning Nano-Electrochemistry
• Nanoelectrical Measurements in Liquid
Pt
SiO2
r ~ 25 nm
h ~ 250 nm
Some Publications
• Nellist et al. Nature Energy 2017, accepted
• Jiang et al. ChemSusChem 2017, DOI: 10.1002/cssc.201700893
• Nellist et al. Nanotechnology 2017, 28, 095711
• Huang et al. Bruker Application Note 2017
• Huang et al. Microscopy Today 2016, 24, 18
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Bruker Confidential
Nanoelectrode Probe
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Active Tip for SECM (local EC studies) & Electrical Characterization in Liquid
• Probe
• Batch (wafer) manufactured
• Exposed tip height: ~ 250 nm
• End tip radius: ~ 25nm
• k = 1.5 N/m, f = 65 kHz
• Package
• Fully isolated, encapsulated in two parts glass
• Easy to handle, robust ESD protection
• Chemical resistant (pH 1-13 & battery solution)
11/15/2017 6 Bruker Confidential
Pt
SiO2
r ~ 25 nm
h ~ 250 nm 1 mm
Nellist et al. Nanotechnology 2017, 28, 095711
High Electrochemical Performance
• Robust for handling and electrochemistry:
[Ru(NH3)6]2+/3+: 4 rinse-and-dry cycles, 5 min
amperometry, and 29 CVs
11/15/2017 7 Bruker Confidential
5 mM [Ru(NH3)6]3+
Potential (V vs
Ag/AgCl)
Cu
rre
nt
(pA
)
[Fe(CN)6]4-/3-
50 CVs
2 hr i-t curve
[Fe(CN)6]3+/4+: 50 CVs and 2 hr amperometry
sub-pA noise level
Nellist et al. Nanotechnology 2017, 28, 095711
High Spatial Sensitivity
11/15/2017 8 Bruker Confidential
Hynek et. al. InTech, 2014, DOI: 10.5772/57203
Nellist et al. Nanotechnology 2017, 28, 095711
Force Curve
Line: Experiment
Symbols: Simulation
• Approach Curves
• Current vs tip-sample distance
• Inactive/active area: negative/positive feedbacks
• Kinetic quantification: shape vs. surface activity
• Consistent with simulation
• No leakage current
• Changes mostly occur within 150 nm
• High spatial sensitivity
• Consistent with diffusion layer structure
0
5
10 mM
[Ru(NH3)6]3+ [Ru(NH3)6]
2+
e
< 100 nm diffusion layer
PeakForce Scanning Electrochemical Microscopy
11/15/2017 9 Bruker Confidential
Scanning Electrochemical Microscopy (SECM)
11/15/2017 10 Bruker Confidential
• A tiny electrode brings electrochemistry to micro- or nano-scale
• Local EC characterizes active site, diffusion, ionic transport, permeability, etc.
• Resolutions are primarily defined by the probe electrode dimension
E vs Ref
E + ΔV vs Ref
O + e R
Sample
R O + e
SECM Applications
11/15/2017 11 Bruker Confidential
Mauzeroll et. al., Chem. Rev. 2016, 116, 13234
PeakForce Tapping
11/15/2017 12 Bruker Confidential
Probe is sinusoidally modulated at 1~2 kHz:
• No cantilever tuning required.
• Low and stable force, < 50 pN.
• Automatic image optimization.
• Quantitative NanoMechanics (QNM).
• Simultaneous nanoelectric capture.
Time Z position Separation
Electrics
Time
PF-TUNA PF-QNM
FSP
ASP
Contact High imaging force
Tapping Rely on resonance
F0
Fpeak PeakForce Tapping Precise force control
PeakForce Tapping: Application Examples
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Small 2014, 10, 3257
DNA
Embedded CNT on P3HT lamellar
Leclere et al. Nanoscale, 2012, 4, 2705
Live E. Coli cells
SAM on Au
Electrochemistry
Microscopy Today 2016, 24, 18
PeakForce SECM
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• Simultaneously multimodal imaging:
Topography, mechanics, conductivity, electrochemistry, etc.
Nellist et al. Nanotechnology 2017, 28, 095711
Lift
Height
PeakForce AFM
Electrochemistry
Interleaved Scan Scanning NanoEC
PeakForce SECM Hardware
Boot Probe
Probe holder
Strain-released module AFM scanner
Resistor selector
Probe connection
EC cell
Temperature control (RT to 65 oC)
Huang et al. Microscopy Today 2016, 24, 18
• Low noise electronics, limited only by potentiostat
• Robust ESD protection
• Compatible with glovebox operation
• Wide range of chemical compatibility
11/15/2017 Bruker Confidential 15
Operation inside a glovebox
PeakForce SECM
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• Multimodal imaging at 15 nm lift height
Si3N4 Pt
25 nm depth Si3N4
Contact Current
4.5 nN 9 nN 4.5 nN
SECM Current
7~10 nA 0.3 nA 0.3 nA
495 pA 290 pA 290 pA
15 nm
25 nm
40 nm
60 nm
150 nm
400 nm
Si3N4 Pt Si3N4
• Lift height-dependent current.
• Changes mostly occur within 100 nm lift height.
• Confirm the compact structure of the diffusion layer.
Defects on HOPG Electrode
11/15/2017 17 Bruker Confidential
Nellist et al. Nanotechnology 2017, 28, 095711
Electrochemistry
Modulus Adhesion
Conductivity
r ~ 25 nm
Topography 250 nm
0.4 nm step 800 nm
4 nN difference 800 nm
900 nm x 600 nm
55 pA difference 800 nm
2~5 pA higher
Topography
Adhesion
SECM
PeakForce SECM Pt/p+-Si for Catalysis
• Settings:
• 10 mM [Ru(NH3)6]3+, 0.1M KCl
• Tip potential: -0.4 V vs AgQRE
• Sample potential: -0.1 V vs AgQRE
• Peak force: 700 pN; Scan rate: 0.2 Hz; Lift height: 100 nm;
• PeakForce Tapping is required to measure these loosely attached particles
• Contact current measures interfacial conductivity
• SECM current measures electrochemical activity
11/15/2017 18 Bruker Confidential
Topography Contact Current
SECM Current
Jiang et al. ChemSusChem, 2017 DOI: 10.1002/cssc.201700893
Force Volume Scanning Electrochemical Microscopy
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Kinetic Quantification of Surface Reaction
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3 µm
3 µm
3 µm
Si3N4
Pt
Inhomogeneous conductivity
Inhomogeneous electrochemical activity
Approach curves of distinct characteristics
Force Volume Quantitative mechanical mapping modes
• Linear ramping to collect the complete force curve from every tap
• Multiple property maps calculated
• Multiple ramp data channels acquired
• Ramp and hold functionality
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Separation
Force Volume: 1Hz FastForce Volume156Hz
Force Volume SECM
• Array of approach curves for improved EC quantification.
• EC activity in function of distance to sample surface, in every pixel (mapping).
• Correlated topography, nanomechanics and nanoelectrics
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0.75 Hz ramp rate on Z
62.5 nm / pixel
Topography
Force Curves
Approach Curves
Force Volume SECM Insulating Flake on Au Substrate
• Sample Courtesy: Liming Zhang, J. Tyler Meffordd, Andrew Akbashev, and William Chueh, Stanford University
11/15/2017 23 Bruker Confidential
Oxide Au
Force Volume SECM Density Plot
• Density plot shows which EC activities are most commonly present
• Two distinct areas are differentiated by the two density plots
• Sample Courtesy: Liming Zhang, J. Tyler Meffordd, Andrew Akbashev, and William Chueh, Stanford University
24 Bruker Confidential
Tip
Cu
rre
nt
(nA
)
Oxide
Au
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Ramp and Hold with FV-SECM
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Pt
Si3N4
Pt
Si3N4
Fo
rce (
nN
) T
ip C
urr
en
t (n
A)
Tip
Cu
rren
t (p
A)
On Pt, positive feedback and electrically connected with the Pt electrode
On nitride, negative feedback and electrically disconnected with the Pt electrode
Nellist, M. R.; Laskowski, F. A. L.; Qiu, J.; Sivula, K.; Hamann, T.W.; Boettcher, S.W. Potential-sensing electrochemical atomic force microscopy
enables in-operando analysis of electrocatalysis during (photo)electrochemical water splitting. Accepted, Nat. Energy.
Nanoelectrode AFM probes enable the in-operando
measurement of surface electrochemical potentials
during oxygen evolution catalysis
1 µm 1 µm
CoPi on planar
Fe2O3
planar Fe2O3 CoPi
photoelectro-
deposition
• Catalytst voltage (Vtip) identical
whether on ITO or illuminated hematite
• Holes transfer from hematite to CoPi,
where water oxidation occurs Spatially resolved photovoltage!
11/15/2017 27 Bruker Confidential
Nanoelectrical Measurements in Liquid
AFM Nanoelectrical Measurements
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• Bruker provides a versatile array of electrical techniques for a multitude of applications.
Conductivity/Resistivity C-AFM, TUNA, PeakForce-TUNA, SSRM
Electric Field EFM
Charge EFM, SCM
Surface Potential / Work Function KPFM, PeakForce KPFM
Carrier Density SCM, SSRM, sMIM, PeakForce-sMIM
Piezoelectricity PFM
PeakForce Nanoelectrical Measurements
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• For previously AFM-inaccessible, delicate samples and adds correlated nanomechanical data
• Improve tip lifetime with hard samples
• Decrease sample wear with soft samples
• Improve resolution due to sharper tips & less sample damage
Electrics
Time
PeakForce TUNA (A) topography, (B) current, and (C) adhesion maps
reveal the influence of an embedded nanotube on P3HT lamellar ordering
and current pathways. Image size 500 nm.
Leclere et al. Nanoscale, 2012, 4, 2705
Nanoelectrical Liquid Imaging
11/15/2017 30 Bruker Confidential
Battery • Applications
• Energy research
• Bio-electricity
• Catalysis
• Sensing
• Challenges
• Compatibility:
Environment & chemicals
• Localized signals
• High S/N
Energy/Catalysis
Lee et al. Adv. Mater. 2014, 26, 4880
Bio-electricity
Kumar et al. ACS Appl. Mater. Interfaces, 2017, 9, 28406
Jiang et al. ChemSusChem, 2017 DOI: 10.1002/cssc.201700893
• Probe and sample are fully immersed in solution
• High quality, localized signal
• Fully-insulated but the tip apex
• Conductive path to minimize stray capacitance
• High bandwidth, next-to-tip amplifier
100 µm
Nanoelectrical Liquid Imaging
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TUNA & PeakForce TUNA in Liquid
PeakForce TUNA in Liquid (DMC) in Glove Box
• Sample was in DMC, a solvent for battery research
• Measurement was done inside a glove box
• Clearly differentiates exposed Pt on the current map
• I-V spectra confirms the difference in conductivity
• Negligible background current at nitride surface
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1
2
3
Si3N4
Si3N4 Pt
1 2
3
Single line data, no averaging
Nellist et al. Nanotechnology 2017, 28, 095711
PeakForce TUNA in Liquid in 1M KCl Aqueous Solution at High Bias
• Low parasitic currents on Si3N4:
• At -0.5V: 1.06 pA
• At +0.5V: 0.07 pA
• Low current noise level: ~1 pA
11/15/2017 34 Bruker Confidential
0.5V
-0.5V
0.5V
-0.5V
Si3N4 Pt
Si3N4 Pt
Si3N4 Pt
PeakForce TUNA in Liquid Interfacial Energetics on a Photoelectrode
• Semiconductor/Metal Junction in Liquid
• Sample shows diode behavior in air
• I-V characteristics in H2O totally changes
11/15/2017 35 Bruker Confidential
Air
Liquid
Liquid on SiO2
-250 pA
100 pA
120 nm
120 nm
Sample bias: 0.3 V
Huang et al. Microscopy Today 2016, 24, 18
Pt/p+-Si: PeakForce SECM
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Topography
Contact Current
SECM Current
• Resistive interface: contact current (interfacial conductivity) is correlated with SECM current
• Conductive interface: EC activity is compared (e.g. #2 vs. #3, higher contact current but lower SECM current)
Contact Current (nA)
1.4 1.6 1.8 4.0 5.0
SE
CM
Curr
ent (n
A)
1.40
1.45
1.50
1.55
1.60
Col 1 vs Col 2 Col 1 vs Col 2: 1.5500
Col 1 vs Col 2: 5.1900
#2
#3
Jiang et al. ChemSusChem, 2017 DOI: 10.1002/cssc.201700893
Pt
SiO2
Si
e
O R
e
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PeakForce KPFM in Liquid
PeakForce KPFM in Liquid (H2O, 1 mM KCl, or DMC)
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Pt Pt
Si3N4 Si3N4
Pt Pt
Si3N4 Si3N4
• In Air: ~125 mV difference
• In H2O: ~150 mV difference
Pt Si3N4 Si3N4
Si3N4 Pt
Pt
11/15/2017 39 Bruker Confidential
Piezoresponse Force Microscopy (PFM) in Liquid
Web: http://spec-lab.ecnu.edu.cn/ E-mail: [email protected]
Air- at contact resonance H2O-Off resonance H2O - at resonance
0.5 M NaCl 0.01 mM NaCl 0.1 mM NaCl 1 M NaCl
High-Resolution Electromechanical Imaging of Bio-compatible
Ferroelectric Materials in Air, Water and NaCl Electrolyte.
• Slides contributed from Anyang Cui, East China Normal University.
• Measurements were in collaboration with Bruker.
• Cui & Hu et al., manuscript in preparation.
Nanoelectrode from Bruker
Unpublished Results, Manuscript in Preparation
Anyang Cui
Phase Contrast at Contact Resonance
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Air H2O
1 mM 10 mM
H2O
Air
1 mM
Measurements were in collaboration with Cui&Hu et. al. at ECNU in China
Air H2O 1 mM 10 mM
2 µm 2 µm 2 µm 2 µm
• Sample: PPLN; Electrolyte: NaCl; Image Force: 100 nN
Conclusion
• Bruker’s new AFM-SECM probe technology improves
SECM lateral resolution by orders of magnitude and
opens the door to new measurements on individual
nanoparticles, -phases, and –pores
• PeakForce SECM enables the highest spatial resolution
and multi-modal imaging on soft and fragile samples
• Force Volume SECM allows for improved kinetic
quantification and provides 3D electrochemical
mapping, through capturing a complete data cube
• PeakForce nanoelectrical measurements in liquid
provide new capabilities for visualization of electrical
processes in solution
11/15/2017 42 Bruker Confidential
Huang et al. Microscopy Today 2016, 24, 18
Pt
SiO2
r ~ 25 nm
h ~ 250 nm
© Copyright Bruker Corporation. All rights reserved.
www.bruker.com
43 Bruker Confidential
KPFM Sensitivity Scales with Q/k
• In liquid, the sensitivity is about 20x lower (vs. air) with these cantilevers
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f0 ~ 62 kHz Q ~ 215
f0 ~ 29 kHz Q = 10
• In di-H2O • In Air
Tapping Mode (Z Modulation)
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• Cells were over grown and covered the whole petri dish
• SECM probe successfully imaged the topography of live cells without sample damages
Defects on HOPG Electrode
11/15/2017 46 Bruker Confidential
800 nm 800 nm
Topography Electrochemistry