mems devices for in-situ electron microscopy testing of...

Micro and Nanomechanics LabDepartment of Mechanical Engineering

MEMSMEMS devices fordevices for InIn--SituSitu Electron Microscopy Electron Microscopy Testing of NanostructuresTesting of Nanostructures

HoracioHoracio D. EspinosaD. Espinosa

Acknowledgments: NSF-NIRT, NSF-NSEC, FAA, ONR

Y. Zhu, CY. Zhu, C--H. H. KeKe, N. Moldovan, N. Moldovan


NEMS Characterization TechniqueNEMS Characterization Technique-- Component Constitutive Behavior (Component Constitutive Behavior (CNTs/NWsCNTs/NWs))

-- ElectroElectro--Mechanical Characterization at the Device LevelMechanical Characterization at the Device Level


AFM bending

SEM Tension

Yu et al., Science (2000)

Marszalek et al., PNAS (2000)

Techniques for Testing NanostructuresTechniques for Testing Nanostructures

AFM Tension

Salvetat et al. PRL (1999)

Stiff cantilever

Compliant cantilever

stretch

to Piezo-positioner

Haque and Saif, Exp. Mechanics (2002)

TEM Tension


Lack direct or simultaneous real time measurement of load, deformation and imaging of atomic defects. Imaging is required for both load measurement and atomic defects identification. However, the required magnifications are quite different.Do not exhibit a single loading condition specially at large deformations.Are not suitable for in-situ TEM (highest atomic resolution).Cannot measure specimen electronic properties under a well-characterized loading condition.

LimitationsLimitations


MEMSMEMS--based Material Testing Systembased Material Testing System

ThermalActuator

Zhu, Moldovan and Espinosa, Appl. Phys. Lett. 86, 013506 (2005)

Displacement Control Force Control

Thin FilmsNWs/CNTs


movable combs

stationary combs

overlap

widthgap

• Pairs of combs: 300/1200

• Folded beam length: 125 µm

• Folded beam width: 2.5 µm

• Folded beam height: 3.5 µm

F=Nε0V2h/d • Height (h): 2 µm

• Width (w): 2 µm

• Gap (d): 2 µm

• Overlap (o): 15 µm

• Length (l): 30 µm

Electrostatic (Comb Drive) Actuator Electrostatic (Comb Drive) Actuator –– Force ControlForce Control

wing

shuttle

arm

folded beam


Thermal Actuator Thermal Actuator –– Displacement ControlDisplacement Control

Poly-Si Beam

AirSi3N4

Si Substrate

hair

h

hn

Cross Section A-A’(b)

V

Inclined beams

Motion u

Shuttle

(a)A

A’

• Pair of inclined beams: 5/10

• Beam length: 300 µm

• Beam width: 8 µm

• Beam height: 3.5 µm

θ

Prorok, Zhu, Espinosa, Bazant & Yakobson, in Encyclopedia of Nanoscience and Nanotechnology(2004), p. 555; Zhu, Corigliano & Espinosa, in press J. Micromech. Microeng., (2006)

Anchors

( )ratio stiffness bendingover axial :

12 ;

cossin2

sin 2

22

ψ

ψθθψ

θα

IAlNEA

lFlTU

S=

+

−∆=


0

5

10

15

20

25

0 5 10 15 20 25 30θ (°)

U/a

DTl

analytical

FEA-linear region

FEA-nonlinear region

0

0.05

0.1

0.15

0.2

0.25

0.3

0 5 10 15 20 25 30θ (°)

Kl/2

EA

0

1

2

3

4

5

6

7

0 5 10 15 20 25 30θ (°)

-N (m

N)

Pcr min

Beam Angle Selection Beam Angle Selection -- 11

2 22

sin12sin cos

UIT l

Al

θα θ θ

=∆ ⎛ ⎞+⎜ ⎟

⎝ ⎠

2 22

12sin cos2

tbK l IEA Al

θ θ= +

⎟⎟⎠

⎞⎜⎜⎝

⎛+

∆=θθ

θα2

22

2

cos12

sin

cos

IAl

EATN

Displacement Stiffness

Beam internal forceBuckling force

Buckling


100 µm100 µm

Beam Angle Selection Beam Angle Selection -- 22

10o beam angle 30o beam angle

10 beam pairs 5 beam pairs


Small KlS Large XLS

θα sin2 TEANFXKXKXKXK

XXX

AASS

SSLSLS

ASLS

∆==+=

=+KA KS KLS

F

XLSXA

XS =XA -XLS

high load sensor resolution

large XA high temperature increase

To test a particular structure, KS and XS are given

KLS is an important design parameter

Lumped SystemLumped System ModelModel

⇒ ⇒

⇒⇒

⇒⇒


Thermal Actuator

KT KSKL

F

XLXT

Governing Equations:XS = XT - XLKS XS = KL XLKT XT = F – KS XSF= NEAα∆T cosθ

Capacitive load sensor stiffness:

MWCNT specimen stiffness:

Thermal actuator stiffness:

For a MWCNT specimen (ls = 2 µm; F=1 µN, ε = 4%)XT=157.3 nm, XS=93.5nm and XL=53.8nm

Zhu and Espinosa, PNAS, Vol. 102, 2005

Lumped Model Lumped Model –– CNT Example CNT Example

Specimen

Capacitive Load Sensor

Thermal Actuator Au film

N/m 4689212)cos(sin10 3

3

3

322 =++=

sb

sbA l

hEbl

hEbl

EbhK θθ

N/m 6.182243

3

3 ===L

LL

LL l

hEblEIK

N/m 7.100 ===S

S

S

SS l

tDEl

AEK π• Pair of inclined beams: 5/10• Beam length: 300 µm• Beam width: 8 µm• Beam height: 3.5 µm


0

200

400

600

800

1000

1200

0 50 100 150 200 250 300

temperature increase close to specimen (°C)

disp

lace

men

t (nm

)

no sink beamsone pair of sink beamsthree pairs of sink beamssix pairs of sink beams

Thermal Actuator Thermal Actuator –– MultiphysicsMultiphysics SimulationSimulation

Temp uanchors

Heat sink beams

Actuation Voltage: 1V1VIn Vacuum

55oC 66nm

Zhu, Corigliano & Espinosa, in press J. Micromech. Microeng., (2006)

0

200

400

600

800

1000

1200

0 2 4 6 8 10

actuation voltage (V)

disp

lace

men

t (nm

)

0

3

6

9

12

15

0 1 2 3 4 5 6 7 8 9


curr

ent (

mA) 1/R


34

38

42

46

50

54

0 3 6 9 12 15

current (mA)

resi

stiv

ity ( Ω

µm

)

0

100

200

300

400

500

avg.

tem

p. c

hang

e (K

)experiment 1

experiment 2

experiment 3

Highest temperature

Highest temperature

Comparison between Experiments and SimulationsComparison between Experiments and Simulations

0

100

200

300

400

500

600

700

800

0 3 6 9 12 15current (mA)

disp

lace

men

t (nm

)

experiment 1experiment 2experiment 3FEA

Damage

1 µm

(a)

(b)

(c)

1 µm

1 µm


Load SensorLoad Sensor

ddCAVNC

CVV

ddd

ANC

ddddANCCC

oosense ∆∆=∆

∆+∆=∆

⎟⎟⎠

⎞⎜⎜⎝

⎛∆+

−∆−

=−=∆

2000

320

0012

2~

)(2

11

ε

οε

ε

∆d

R2

R2

R12

R1

R1R3

C1 C2

C3

S1 S2RS2

Zhu, Moldovan and Espinosa, Appl. Phys. Lett. 86, 013506 (2005)


Load Sensor and Signal ConditioningLoad Sensor and Signal ConditioningCharge sensing method:•

• Eliminates parasitic capacitances

dVsense ∆∝∆

1 cm

Vref

Cf

LPF

outputvoltage

synchronousdemodulator

-+

C1

C2

capacitive load sensor

Device Chip Sensing IC Chip

• Both chips on a custom-made PCB;

• Minimizes stray capacitance and electro-

magnetic interference.

Double chip Architecture


Load Sensor Calibration Load Sensor Calibration -- 11

2.539

2.54

2.541

2.542

2.543

2.544

2.545

2.546

2.547

0 10 20 30 40 50

time (s)

output voltage (V)

(b)

(e)

2.539

2.54

2.541

2.542

2.543

2.544

2.545

2.546

2.547

0 10 20 30 40 50

time (s)output voltage (V)

(d)CCVV

fsense ∆=∆ 0

1 mV corresponds to 1 fF

(a) Actuation voltage = 2 V

200 nm

(c) Actuation voltage = 5 V

200 nm

∆d


Load Sensor Calibration Load Sensor Calibration -- 22

0

100

200

300

400

500

0 1 2 3 4 5 6 7 8actuation voltage (V)

disp

lace

men

t (nm

)

0

5

10

15

20

0 2 4 6 8


capa

cita

nce

chan

ge (f

F)

Load = displacement × stiffness

0

100

200

300

400

500

0 5 10 15 20capacitance change (fF)

disp

lace

men

t (nm

)

0

1000

2000

3000

4000

5000

6000

load

(nN

)

Stiffness = 11.8 N/m

Device ResolutionDevice Resolution

Capacitance change: 0.05 fFDisplacement: 1 nmLoad: 12 nN


Other ConfigurationsOther Configurations

200 µm

200 µm

Compression/Buckling

Electronic measurement of load and elongation


Load sensor Thermal actuator

Heat sink beams

Backside window

Displacement markers

In-situ TEM Devices: Nanostructure & Thin Film


Fabrication Process of In-situ TEM Device


inin--situ SEM Experimentssitu SEM Experiments


Nanoscale Polysilicon Film - 1FIB machined


Nanoscale Polysilicon Film - 2

Young’s modulus = 155±5 GPa

Fracture strength 0.72~1.42 GPa

Displacement Markers

Fracture surface

Zhu and Espinosa, PNAS, (2005)


inin--situ SEM/TEM Experiments of situ SEM/TEM Experiments of CNTsCNTs


In-situ TEM Setup

1

5 mm

10 mm

Φ = 3 mm Electric contacts

1.5 mm

TEM holder platform

Chip with MEMS devices

In collaboration with Prof. Ivan Petrov, Center for Microanalysis of Materials, UIUC

5 mm


5 µm

A B

C D

FIB Cut

EBID Ptnanoweld

Specimen Mounting on MEMS


Experimental Data – CVD Grown MWCNTs

0

5

10

15

20

25

30

35

0 50 100 150 200 250

Displacement [nm]

Load

[ µm

]

Ion Irradiation (FIB-TEM)E-beam 1 (TEM)E-beam 2 (TEM)Low irradiation (SEM)

0

5

10

15

20

25

30

35

0 2 4 6 8 10

Strain [%]

Stre

ss [G

Pa]

Ion Irradiation (13 shells)E-beam 1 (5 shells)E-beam 2 (3 shells)Low irradiation (1 shell)

•• EE--beam 1 and 2 tested in TEM operated at 200 kV (Telescopic failurbeam 1 and 2 tested in TEM operated at 200 kV (Telescopic failure)e)• EE--beam 1 (beam 1 (nanoweldingnanowelding very close to shuttle edge, very close to shuttle edge, failure inside failure inside

observation windowobservation window), E), E--beam 2 (beam 2 (nanoweldingnanowelding ~1.5 ~1.5 µµm from edge, m from edge, failure failure just outside observation windowjust outside observation window))

•• Ion Beam irradiation in FIB with gallium ions (entire crossIon Beam irradiation in FIB with gallium ions (entire cross--sectional failure)sectional failure)•• Low irradiation sample tested in SEM operated at 3Low irradiation sample tested in SEM operated at 3--5 kV 5 kV (Telescopic failure inside observation window)(Telescopic failure inside observation window)

E=315 E=315 GPaGPa


0

5

10

15

20

25

30

35

0 2 4 6 8 10

Strain [%]

Stre

ss [G

Pa]

Ion Irradiation (13 shells)E-beam 1 (5 shells)E-beam 2 (3 shells)Low irradiation (1 shell)

Constitutive Behavior and Failure Modes

Nano diffraction

Two Failure ModesTwo Failure Modes

CVD Grown CVD Grown MWCNTsMWCNTs•• EE--beam 1 and 2 tested in TEM beam 1 and 2 tested in TEM operated at 200 kV (T)operated at 200 kV (T)

•• Ion Beam irradiation in FIB with Ion Beam irradiation in FIB with gallium ions (CS)gallium ions (CS)

•• Low irradiation sample tested Low irradiation sample tested in SEM operated at 5 kV (T)in SEM operated at 5 kV (T)

•• Young’s Modulus E=315 Young’s Modulus E=315 GPaGPa T: telescopic ; CS: entire cross-section

50 nm

50 nm

E=315 E=315 GPaGPa


Telescopic Failurea b

c

1

2


Load Transfer Mechanism- Inter-Shell Bridging

Vacancy or Interstitial threshold Vacancy or Interstitial threshold Energy is 86 Energy is 86 keVkeV

Telling et al., Nature Mat. (2003)

Kis et al., Nature Mat. (2004)

DFT prediction DFT prediction of C atom in a of C atom in a fourfold coordinated fourfold coordinated interstitialinterstitial

SWCNT bundles


Discussion

Zhang et al., PRB, 71 (2005)

QMQM

MMMM--MTBMTB

ExperimentsExperimentsArcArc--growngrown

rh

• CVD and arc grown MWCNTs exhibit the same E and comparable failure stresses.

• For the first time, in-situ TEM experiments revealtwo failure modes with increasing number offailing shells as the irradiation dose and type isvaried. The lowest dose was obtained inin-situ SEM experiments where single shell failurewas observed.

• Failure stress shows statistical behavior consistentwith brittle failure and volume scaling.

• Large number of missing atoms, holes with radiiof about 3-4 nm are required to explain the lowstrengths experimentally measured.

• Models based on van der Waals inter-shell interac-tions are insufficient to explain the multi-shell failureobserved experimentally. Additional QM studies ofmechanical and electronic states are needed.


Before Straining

low mag. high mag.mid. mag.

In-situ TEM Testing of Carbon Nanotubes


After Straining

Walls disappeared?


High Resolution TEM


EELS Spectrum

0.00E+00

1.00E+04

2.00E+04

3.00E+04

4.00E+04

5.00E+04

6.00E+04

280 300 320 340 360

photon energy (eV)


Gold Nanowires

twin

nanotwin

20nm

[110]

• [110] growth direction• Average diameter: 20±5 nm• One grain through the thickness• A large number of twins but no dislocations

20nm

[110]

[111]

HRTEM

In collaboration with Dr. Hsien-Hau Wang, Materials Division, Argonne National Lab

Dr. C. Li


MD Simulations of NWs[111] Nanowires

012345678

0 0.02 0.04 0.06 0.08 0.1Strain

Tens

ile S

tres

s (G

Pa)

5nm10nm15nm17.5nm

[110] Nanowires

0

0.5

1

1.5

2

2.5

3

3.5

0 0.02 0.04 0.06 0.08 0.1Strain

Tens

ile S

tres

s (G

Pa)

5nm10nm15nm17.5nm

012345678

5 10 15Diameter (nm)

Tens

ile Y

ield

Str

ess

(GPa

)

<111><110>

A

B

C

[111] Nanowires

012345678

0 0.02 0.04 0.06 0.08 0.1Strain

Tens

ile S

tres

s (G

Pa) 5nm

10nm15nm17.5nm

[110] Nanowires

0

0.5

1

1.5

2

2.5

3

3.5

0 0.02 0.04 0.06 0.08 0.1Strain

Tens

ile S

tres

s (G

Pa)

5nm10nm15nm17.5nm

012345678


Tens

ile Y

ield

Str

ess

(GPa

)

<111><110>

A

B

C

(A and B) Tensile stress responses for [111] and [110] axially oriented wires (as seen in Figure 1A and 1B, respectively) with representative radii from 5nm to 17.5nm. (C) Tensile yield stress as a function of diameter for all examined sizes. Both orientations show a drop in tensile yield stress with increasing diameter.

[111][110] [111][110]

5

7.510 12.5 15 17.5

5

7.510

12.515

17.5

-1.2

-1

-0.8

-0.6

-0.4

-0.2

0


Equi

libriu

m S

trai

n (%

)

[111] [110]

[111][110] [111][110]

5

7.510 12.5 15 17.5

5

7.510

12.515

17.5

-1.2

-1

-0.8

-0.6

-0.4

-0.2

0


Equi

libriu

m S

trai

n (%

)

[111] [110]


Role of Surface Defects

0

0.005

0.01

0.015

0.02

0.025

0 0.02 0.04 0.06 0.08 0.1 0.12

Deformation

Cha

nge

in E

nerg

y (e

V)/A

tom

2 30

2 23

E EV

ε ξε∆= +

0

0.002

0.004

0.006

0.008

0.01

0.012

0 0.02 0.04 0.06 0.08 0.1 0.12

Deformation

Cha

nge

in E

nerg

y (e

V)/a

tom σ1=4.07σy=7.35 GPa

Orientation <111>Orientation <111>D=5 nmD=5 nmStrain Rate = 5x10Strain Rate = 5x107 7 ss--11

Step is created by a ½ Step is created by a ½ <110> translation; perfect <110> translation; perfect dislocation shift.dislocation shift.


http://clifton.mech.northwestern.edu/~espinosa/

Y. Zhu, Northwestern UniversityC-H. Ke, Northwestern UniversityN. Moldovan, Northwestern UniversityK-H. Kim, Northwestern UniversityB. Peng, Northwestern UniversityT. Belytschko, Northwestern UniversityG. Schatz, Northwestern UniversityC. Mirkin, Northwestern UniversityZ. Bazant, Northwestern University

Acknowledgments:Acknowledgments:

National Science Foundation-NIRT, J. Larsen-Basse, K. ChongFederal Aviation Administration, J. NewcombNSF-NSEC at NU for Integrated Nanopatterning and Detection TechnologyOffice of Naval Research, L. Kabakoff

D. Farkas, Virginia Tech.B. Hyde, NUN. Pugno, Politecnico di TorinoP. Zapol, ANLO. Auciello, ANLI. Petrov, UIUCJ. Mahon, UIUCM. Marshall, UIUCB. Prorok, Aurburn University

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