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

108 atoms

108 a

tom

s

108 atoms

few atoms thick

Normal (3D) material Two-dimensional (2D) material

not naturally occurring, but can be synthesized

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

MoS2 MoSe2 MoTe2 WS2

WSe2

WTe2 TaS2

TaSe2 TaTe2 NbS2

NbSe2 NbTe2

In2Se3 InSe HfS2 …

Which have the most useful properties for electronic devices and sensors? Our HPC efforts provide

direction.

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

a SAW filter (used in every

cellphone)

Can 2D materials be applied in this context?

Computational Prediction of 2D Piezoelectricity

quantum mechanical simulations

HPC

2D Piezoelectricity

Graphene (C) BN

MoS2 MoSe2 MoTe2 WS2

WSe2

WTe2 TaS2 TaSe2 TaTe2 NbS2

NbSe2 NbTe2

In2Se3 InSe HfS2 …

Calculated d11 coefficients (pm/V):

0

2

4

6

8

10

12

AlN

α-quartz

ZnO

BN MoS2 MoSe2 MoTe2 WS2 WSe2 WTe2

Duerloo, J. Phys. Chem. Lett., 3, 19 (2012)

Our HPC-enabled approach enables identification of promising materials.

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

a SAW filter (used in every

cellphone)

Can 2D materials be applied in this context? yes

0 0.005 0.01 0.015 0.020

1

2

3

4x 10

!17

Strain !11

! !22

Qm

eta

l (C

)

0 2 4 6 8 10 120

0.005

0.01

0.015

0.02

Str

ain

!11 !

!22

Time (s)

0 2 4 6 8 10 12!0.01

!0.005

0

0.005

0.01

Curr

ent (p

A)

Time (s)

Our HPC-enabled predictions have driven experimental observation

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

1T

1T’

semiconductor

metal

metal

Semiconducting Metallic

Two phases have been observed in chemically exfoliated monolayer

MoS2 and WS2.

Eda et al, ACS Nano 6, 7311 (2012); Voiry et al, Nat. Mat. (2013).

Can the phases of monolayers be engineered and employed in devices?

Metallic

Some materials have more than one 2D crystal structure:

2H

1T’

semiconductor

metal

Can this phase transition be controlled in an electronic device? If so: which material is most promising?

HPC challenge: find phase-changing materials

MoS2 WS2

MoSe2 WSe2

MoTe2 WTe2

2D p

hase

ene

rgy

(e

V p

er M

X2)

Our semi-local DFT calculations indicate MoTe2 and WTe2 exhibit the smallest

2H-1T’ energy difference.

PBE EXC. No phonons.

Discovery: tension causes phase transition

x-axis extension (%)

y-ax

is e

xten

sion

(%)

Lesson from HPC-enabled screening: 1)   Use MoTe2; 2)   Apply tension along the

crystal’s y-axis.

HPC bypasses trial-and-error steps and guides future experiments.

Duerloo will be visiting ARL in July for a week to participate in this ARL experiment with Madan Dubey et al.

x-axis extension (%)

y-ax

is e

xten

sion

(%)

In-depth HPC calculations on Garnet show temperature brings 2D phase transition even

closer to ambient conditions.

MoTe2, PBE, 300 K

x-axis extension (%) y-

axis

ext

ensi

on (%

) MoTe2, HSE06, 300 K

2

0

6

4

10

8

0 4 8 -4

2

0

6

4

0 2 4 -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

Strain engineering of electrical contacts with monolayers

Phase transitions in monolayer TMDs

Experiments being done at ARL (Madan Dubey,

Matt Chin, et al) to study impact of piezoelectricity

on electrical contacts under strain.

ARMY COLLABORATIONS ON FLEXIBLE ELECTRONICS

ARL experiments (Dubey et al.) with flexible

substrates to observe metal transitions in MoTe2.

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

PROJECT PUBLICATIONS FY 2013

Recent journal publications: •  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)