Lecture 7 MEMS devices for In-Situ Electron Microscopy...
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Micro and Nanomechanics LabDepartment of Mechanical Engineering
Lecture 7 MEMS devices forLecture 7 MEMS devices for InIn--SituSitu Electron Electron Microscopy Testing of NanostructuresMicroscopy Testing 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
Micro and Nanomechanics LabDepartment of Mechanical Engineering
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
Micro and Nanomechanics LabDepartment of Mechanical Engineering
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
Micro and Nanomechanics LabDepartment of Mechanical Engineering
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
Micro and Nanomechanics LabDepartment of Mechanical Engineering
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
Micro and Nanomechanics LabDepartment of Mechanical Engineering
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
Micro and Nanomechanics LabDepartment of Mechanical Engineering
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=
+
−∆=
Micro and Nanomechanics LabDepartment of Mechanical Engineering
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
Micro and Nanomechanics LabDepartment of Mechanical Engineering
100 µm100 µm
Beam Angle Selection Beam Angle Selection -- 22
10o beam angle 30o beam angle
10 beam pairs 5 beam pairs
Micro and Nanomechanics LabDepartment of Mechanical Engineering
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
⇒ ⇒
⇒⇒
⇒⇒
Micro and Nanomechanics LabDepartment of Mechanical Engineering
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
Micro and Nanomechanics LabDepartment of Mechanical Engineering
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
actuation voltage (V)
curr
ent (
mA) 1/R
Micro and Nanomechanics LabDepartment of Mechanical Engineering
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
Micro and Nanomechanics LabDepartment of Mechanical Engineering
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)
Micro and Nanomechanics LabDepartment of Mechanical Engineering
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
Micro and Nanomechanics LabDepartment of Mechanical Engineering
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
Micro and Nanomechanics LabDepartment of Mechanical Engineering
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
actuation voltage (V)
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
Micro and Nanomechanics LabDepartment of Mechanical Engineering
Other ConfigurationsOther Configurations
200 µm
200 µm
Compression/Buckling
Electronic measurement of load and elongation
Micro and Nanomechanics LabDepartment of Mechanical Engineering
Load sensor Thermal actuator
Heat sink beams
Backside window
Displacement markers
In-situ TEM Devices: Nanostructure & Thin Film
Micro and Nanomechanics LabDepartment of Mechanical Engineering
Fabrication Process of In-situ TEM Device
Micro and Nanomechanics LabDepartment of Mechanical Engineering
inin--situ SEM Experimentssitu SEM Experiments
Micro and Nanomechanics LabDepartment of Mechanical Engineering
Nanoscale Polysilicon Film - 1FIB machined
Micro and Nanomechanics LabDepartment of Mechanical Engineering
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)
Micro and Nanomechanics LabDepartment of Mechanical Engineering
inin--situ SEM/TEM Experiments of situ SEM/TEM Experiments of CNTsCNTs
Micro and Nanomechanics LabDepartment of Mechanical Engineering
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
Micro and Nanomechanics LabDepartment of Mechanical Engineering
5 µm
A B
C D
FIB Cut
EBID Ptnanoweld
Specimen Mounting on MEMS
Micro and Nanomechanics LabDepartment of Mechanical Engineering
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
Micro and Nanomechanics LabDepartment of Mechanical Engineering
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
Micro and Nanomechanics LabDepartment of Mechanical Engineering
Telescopic Failurea b
c
1
2
Micro and Nanomechanics LabDepartment of Mechanical Engineering
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
Micro and Nanomechanics LabDepartment of Mechanical Engineering
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.
Micro and Nanomechanics LabDepartment of Mechanical Engineering
Before Straining
low mag. high mag.mid. mag.
In-situ TEM Testing of Carbon Nanotubes
Micro and Nanomechanics LabDepartment of Mechanical Engineering
After Straining
Walls disappeared?
Micro and Nanomechanics LabDepartment of Mechanical Engineering
High Resolution TEM
Micro and Nanomechanics LabDepartment of Mechanical Engineering
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)
Micro and Nanomechanics LabDepartment of Mechanical Engineering
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
Micro and Nanomechanics LabDepartment of Mechanical Engineering
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
5 10 15Diameter (nm)
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
5 10 15Diameter (nm)
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
5 10 15Diameter (nm)
Equi
libriu
m S
trai
n (%
)
[111] [110]
Micro and Nanomechanics LabDepartment of Mechanical Engineering
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.
Micro and Nanomechanics LabDepartment of Mechanical Engineering
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