2D Nano-Electromechanical Materials: Recent Highlights
2D Nano-Electromechanical Materials:
Recent Highlights
Karel-Alexander Duerloo*, Yao Li,
Dr. Mitchell Ong, Prof. Evan Reed (PI)
Recent highlights
1.
We discover piezoelectric 2D materials
• Building blocks of 2D sensor and filter devices
2.
We discover accessible phase transitions in 2D materials
• Information and energy storage in 2D materials
3D Materials vs. 2D Materials
Normal (3D) material
10 8 atoms
Two-dimensional (2D) material few atoms thick not naturally occurring, but can be synthesized
10 8 atoms
Advantages of 2D materials:
1.
Ultra-lightweight;
2.
Ultra-flexible, wearable;
3.
Very strong (up to 20% strain);
4.
Low power requirements;
5.
Good and diverse electronic properties;
6.
Can be combined via stacking.
2010 Nobel Prize in Physics graphite graphene
Many different 2D materials exist:
Graphene (C)
BN
MoS
MoSe
2
MoTe
2
In
2
Se
InSe
HfS
2
3
2
…
Which have the most useful properties for electronic devices and sensors? Our HPC efforts provide
WSe
2
WTe
2
TaS
2
TaSe
2
TaTe
2
NbS
NbTe
2
2
2
Recent highlights
1.
We discover piezoelectric 2D materials
• Building blocks of 2D sensor and filter devices
2.
We discover accessible phase transitions in 2D materials
• Information and energy storage in 2D materials
Piezoelectricity Defined
Coupling between mechanical stress and electrical polarization .
+
_
+
_
Most engineering materials do not have this property.
Applications for Piezoelectricity
1.
Impact or Pressure sensors
2.
Vibration sensors
3.
Generation/detection of sonar waves
4.
Nanometer-precision motors and actuators
5.
Surface Acoustic Wave (SAW) signal filters
6.
Electricity generation
7.
In-service detection of propagating cracks
Can 2D materials be applied in this context? a SAW filter
(used in every cellphone)
Computational Prediction of 2D
Piezoelectricity
HPC quantum mechanical simulations
2D Piezoelectricity
Graphene (C)
BN
MoS
MoSe
2
2
MoTe
2
WS
2
WSe
2
WTe
2
TaS
2
TaSe
2
TaTe
2
NbS
NbSe
2
2
NbTe
2
In
2
Se
InSe
3
HfS
2
…
Calculated d
11
coefficients (pm/V):
12
10
ZnO
8
6 AlN
Our HPC-enabled approach enables identification of promising materials.
4
α -quartz
2
0
B N Mo S
2
Mo Se
2
Mo Te
2
Duerloo, J. Phys. Chem. Lett.
, 3 , 19 (2012)
W S
2
W Se
2
W Te
2
Applications for Piezoelectricity
1.
Impact or Pressure sensors
2.
Vibration sensors
3.
Generation/detection of sonar waves
4.
Nanometer-precision motors and actuators
5.
Surface Acoustic Wave (SAW) signal filters
6.
Electricity generation
7.
In-service detection of propagating cracks
Can 2D materials be applied in this context? yes a SAW filter
(used in every cellphone)
Our HPC-enabled predictions have driven experimental observation
0.01
0.005
0
− 0.005
− 0.01
0 2 4 6
Time (s)
8
0.02
0.015
0.01
0.005
0
0
4 x 10
− 17
2
3
2
1
0
0 0.005
4 6
Time (s)
0.01
Strain
ε
11
−
ε
22
8
10
10
0.015
12
12
0.02
Confirmed in experiments at
Columbia U.
ARL has parallel efforts.
Leveraged Piezoelectricity in
Ultra-Thin Bilayers
Duerloo, Nano Lett.
, 13 , 1681-1686 (2013)
Recent highlights
1.
We discover piezoelectric 2D materials
• Building blocks of 2D sensor and filter devices
2.
We discover accessible phase transitions in 2D materials
• Information and energy storage in 2D materials
Some materials have more than one 2D crystal structure:
2H
semiconductor
1T
metal
1T’
metal
Semiconducting Metallic
Can the phases of monolayers be engineered and employed in devices?
Metallic
Two phases have been observed in chemically exfoliated monolayer
MoS
2
and WS
2
.
Eda et al, ACS Nano 6, 7311 (2012);
Voiry et al, Nat. Mat. (2013).
Some materials have more than one 2D crystal structure:
2H
semiconductor
Can this phase transition be controlled in an electronic device?
If so: which material is most promising?
1T’
metal
HPC challenge: find phasechanging materials
MoS
2
WS
2
MoSe
2
WSe
2
MoTe
2
WTe
2
Our semi-local DFT calculations indicate
MoTe
2
and WTe
2
exhibit the smallest
2H-1T’ energy difference.
PBE EXC.
No phonons.
Discovery: tension causes phase transition
x
Lesson from HPC-enabled screening:
1) Use MoTe
2
;
2) Apply tension along the crystal’s y -axis.
HPC bypasses trial-anderror steps and guides
Duerloo will be visiting ARL in July for a week to participate in this
ARL experiment with Madan Dubey et al.
In-depth HPC calculations on Garnet show temperature brings 2D phase transition even closer to ambient conditions.
MoTe
2
300 K
, HSE06,
2
0
,
PBE, 300 K
x
-axis extension (%)
x
Recent highlights
1.
We discover piezoelectric 2D materials
• Building blocks of 2D sensor and filter devices
2.
We discover accessible phase transitions in 2D materials
• Information and energy storage in 2D materials
ARMY COLLABORATIONS ON
FLEXIBLE ELECTRONICS
Strain engineering of electrical contacts with monolayers
Experiments being done at ARL (Madan Dubey,
Matt Chin, et al) to study impact of piezoelectricity on electrical contacts under strain.
Phase transitions in monolayer TMDs
ARL experiments (Dubey et al.) with flexible substrates to observe metal transitions in MoTe
2
.
Upcoming ARL visits:
• Duerloo visits for a week in
July to participate in experiment
• Reed visits in July
HIVE Data Visualization
data provided by Yao Li
Recent journal publications:
FY 2013
• Duerloo, K.-A. N., Li, Y., Reed, E. J., “Structural Phase Transitions in Two-
Dimensional Mo and W-Dichalcogenide Monolayers,” Nature Communications, in press (2014).
• Duerloo, K.-A. N., Reed, E. J., “Flexural Electromechanical Coupling: a Nanoscale
Emergent Property of Boron Nitride Bilayers,” Nano Letters , 13 , 1681-1686, doi:
10.1021/nl4001635 (2013).
• Ong, M. T., Duerloo, K.-A. N., Reed, E. J., “The Effect of Hydrogen and Fluorine
Coadsorption on the Piezoelectric Properties of Graphene.
Journal of Physical
Chemistry C ,” 117 , 3615-3620, doi:10.1021/jp3112759 (2013).
Recent Army visits:
ARL (Nov. 2012), Picatinny (Dec. 2012), Natick (Jan. 2013), ARL (May 2013, February
Feb. 2014). ARL Adelphi and Aberdeen upcoming in July 2014.
2D Nano-Electromechanical Materials
Karel-Alexander Duerloo*, Yao Li,
Dr. Mitchell Ong, Prof. Evan Reed (PI)
