B. S. Swartzentruber 1

Characterization of Nanomaterials

Brian S. Swartzentruber, CINT Science Dept.

…from atoms to nanostructures, ensemble systems, and devices

Characterizing nanostructure properties is critical for detailed understanding, predictability, and control.

• Structure properties• Electronic properties

Bulk and interface transportElectronic structureSurface effects

• Mechanical propertiesElastic and plastic deformationFracture and failure mechanisms

• Kinetic propertiesProcesses underlying formation, organization, stability, and decayDiffusivity and diffusion mechanisms

100

101

102

103

104

J (A

/cm

2 )

-0.4 -0.2 0.0 0.2 0.4

Bias (V)

37 nm 54 nm 73 nm 104 nm

250 nm

B. S. Swartzentruber 2

STM can probe atom-scale motion directly

Brian Swartzentruber, 844-6393

r

r2

r1

adatom

L

A meandering localized defect enables the adatom to diffuse via hopover.

Temperature dependence yields the activation barrier.

1.24 eV

Distinctive features of the statistics of motion – a nonbinomial jump distribution, a nonexponential wait-time distribution, and direction and time correlations – imply 1-d hopover diffusion.

w/ Ezra Bussmann

B. S. Swartzentruber 3

AFM provides rapid characterization of surface nanostructures

Julia Hsu, 284-1173

topographycurrent

A

4 m

Carbon fiber in insulating polymer matrix

160 nm

0

250 nmTop of zinc oxide nanorods

B. S. Swartzentruber 4

Conducting AFM enables correlation between topography and conductance

Julia Hsu, 284-1173

Investigate percolation transport of carbon nanofiber - polyimide (insulating polymer) composite microscopically using CAFM.

electrode

Current passes through carbon nanofiber network only (not all nanofibers are part of network).

currenttopography

4 m 4 m4 m

w/ Aaron Trionfi

B. S. Swartzentruber 5

Julia Hsu, 284-1173

Piezoelectric force microscopy (PFM) relates mechanical and electrical state of materials

Polymer

Nanorod Au coatpAamplifier

Biasvoltage

Tipi

250 nm

Topo

PFM

160 nm

7 pm/V0

0

Embedded zinc oxide nanorods

Resistivity (Ωcm)

d 33 R

espo

nse

(pm

/V)

The piezoelectric response correlates directly with the resistivity of the nanorods.

PFM Current

500 nm

w/ David Scrymgeour

B. S. Swartzentruber 6

Interfacial Force Microscopy (IFM) has a non-compliant force sensor that eliminates “snap-to-contact”

Jack Houston, 844-8939

A complete force profile – approach and retract – for a diamond tip on a NaCl crystal. The tip ‘attaches’ to the salt at DC and, upon retraction, pulls out a nanowire that breaks at DR.

The force sensor uses two capacitors in a ‘teeter-totter’ configuration to balance the force.

xyz PiezoController

Sample

ProbeCommon Plate

and Torsion Bars

Cantilever AFM behavior

w/ Nathan Moore

B. S. Swartzentruber 7

The Tecnai F30 TEM at CINT contains specialized piezo-controlled probes

Jianyu Huang, 284-5963

TEM-STM

TEM-AFM

TEM-Indenter

Pulling a nanowire from the NaCl substrate in real time shows the fast diffusion kinetics, defect density, and recrystallization.

B. S. Swartzentruber 8

The ‘air-free’ TEM allows transfer through a glove-box without contamination

Todd Monson, 845-2129

Magnetic nano-particles can be synthesized and imaged in an air-free environment before transfer for magnetic characterization.

TB

B. S. Swartzentruber 9

Nanomanipulator in an SEM allows electrical characterization and direct manipulation of nanostructures

Brian Swartzentruber, 844-6393

Nanomanipulator current-voltage measurements yield metal-semiconductor interface character.

100

101

102

103

104

J (A

/cm

2 )

-0.4 -0.2 0.0 0.2 0.4

Bias (V)

37 nm 54 nm 73 nm 104 nm

Rods are rectifying with diameter-dependent behavior.

Probe contacts Au catalyst particle for IV measurement through the Ge rod.

5

4

3

2

1

n

200150100500

Diameter (nm)

Idea

lity

fact

or

Theoretical ‘carrier-recombination’ mechanism has ideality factor of two.

Rods of diameter > 75 nm appear bulk-like. Depletion width increases in smaller rods.

Forward-bias exponential slope yields ‘ideality factor’.

Ge rods are grown from Au catalyst in a variety of sizes.

w/ Alec Talin

B. S. Swartzentruber 10

Nanomanipulator in an SEM allows electrical characterization and direct manipulation of nanostructures

Brian Swartzentruber, 844-6393

Joystick positioning and programming command allow precise placement and motion control.

500 nm

250 nm

Pulling probe from salt crystal plastically deforms outer layer.

Electron beam ‘shadow’ helps position probe.

Advantage: complete flexibility in hardware, software, and data acquisition

100 nm GaAs rod

Tip-nanostructure adhesion allows pick-and-place.

B. S. Swartzentruber 11

Designing micro-scale platforms for testing mechanical, thermal, and electrochemical properties

John Sullivan, 845-9496

gap for sample

Thermal driven force actuator

Calibrated load measurement

CINT Cantilever Array Discovery Platform™Mechanical Properties

20 m

• Thermal & electrical properties of nanoscale materialsThermal Properties

Electrochemical Properties• Real-time imaging

of electrochemical processes with nanoscale resolution

• Electrochemical cell that operates inside a TEM

seals

electrode 1 window electrode 2

electrolyte channel

Cyn

thia

Vol

kert

(Uni

vers

ity o

f G

oetti

ngen

, Ger

man

y)20

08 C

INT

Use

r Pro

ject

B. S. Swartzentruber 12

Pulsed field gradient nuclear magnetic resonance (PFG-NMR) measures the diffusion of nanoparticles in solution

Todd Alam, 844-1225

Self diffusion and molecular motion of liquids in nano-materials can be measured. Details about the impact of morphology on transport properties within nano-composites and the assembly of nanoparticles and dendrimers are determined.

Decay of NMR signal as a function of field gradient yields particle diffusivity.

PFG NMR - Au Nanoparticles

Gradient (G/cm)

0 5 10 15 20 25 30

Nor

mai

lzed

Sig

nal I

ntes

ity

0.2

0.4

0.6

0.8

1.0

rs

6skTrD

Organically Capped NanoparticlesPFG NMR - Au Nanoparticles

Gradient (G/cm)

0 5 10 15 20 25 30

Nor

mai

lzed

Sig

nal I

ntes

ity

0.2

0.4

0.6

0.8

1.0

rs

6skTrD

Organically Capped Nanoparticles

Present Sandia investigations include:• Diffusion measurements of H2O within fuel cell membranes. How do

changes in membrane nano-morphology (domain size, pore size and surface modification) control the transport rates?

• Measurement of transport in porous materials, and impact of nanostructure on transport of different molecular species

• Measurement of the interaction and aggregation between surface modified nanoparticles and the impact of diffusion of these assemblies.

B. S. Swartzentruber 13

Low-energy electron microscope (LEEM) can image real-time surface nano-structure formation and self-assembly processes

Gary Kellogg, 844-2079

4

Pb/Cu(111)

Pla

ss e

t al.

Patterns are thermodynamic, arising from stress difference between the two phases.

But kinetics have to be fast enough to allow the patterns to form!

Low-energy electron microscope (LEEM) images of Pb/Cu(111)

4

Increasing Pb coverage

• Spatial resolution: 7-8 nm• Time resolution: video rates• Sample temperature: 150 K -1800 K• Background pressure: UHV• Contrast mechanisms: work function

differences (surface chemistry, doping differences), electron interference (surface steps), electron diffraction (surface reconstructions), etc.

Overlayer white - Alloy black

B. S. Swartzentruber 14

LEEM images show p-n contrast on device test structures

Gary Kellogg, 844-2079

10 μm FOV, 0.90 μm linen-type p-type

Blanket n-type implant (<1017)

p-type(~1019)

1000 μm

n-type lines

Schematic of test structure LEEM image of p-n interface

n-type

p-type

=1.2 V

Start Voltage (V)

Inte

nsity

(arb

. uni

ts)

Ramping incident electron energy yields information on surface potential, doping, and oxide properties.

w/ Meredith Anderson

B. S. Swartzentruber 15

Microsystems reliability and failure analysis is pushing to the nanoscale

David Stein, 845-8476

• Charge-Induced Voltage Alteration (CIVA)• Low Energy CIVA (LECIVA)• Light-Induced Voltage Alteration (LIVA)• Seebeck Effect Imaging (SEI)• Thermally-Induced Voltage Alteration (TIVA)

Measure voltage fluctuations in a constant-current power supply as an electron or photon beam is scanned across an IC.

Soft Defect Localization (SDL)

FIB for Imaging and Circuit Editing

TIVA Defect Isolation

• Expertise in Si CMOS, III-V, MEMS, and Optoelectronics

• Support throughout the product life cycle • Extensive reliability & failure analysis capabilities, equipment, tools & techniques

TIVA and STEM for Optoelectronic Failure Analysis

SEM + Nanoprober to arrive fall ‘08

B. S. Swartzentruber 16

Characterizing nanostructure properties is critical for detailed understanding, predictability, and control

• STM can probe atom-scale motion directly• AFM provides rapid characterization of surface nanostructures• Conducting AFM enables correlation between topography and conductance• Piezoelectric force microscopy (PFM) relates mechanical and electrical state of

materials• Interfacial Force Microscopy (IFM) has a non-compliant force sensor that eliminates

“snap-to-contact”• The Tecnai F30 TEM at CINT contains specialized piezo-controlled probes• The ‘air-free’ TEM allows transfer through a glove-box without contamination• Nanomanipulator in an SEM allows electrical characterization and direct manipulation of

nanostructures • Designing micro-scale platforms for testing mechanical, thermal, and electrochemical

properties• Pulsed field gradient nuclear magnetic resonance (PFG-NMR) measures the diffusion of

nanoparticles in solution• Low-energy electron microscope (LEEM) can image real-time surface nano-structure

formation and self-assembly processes • LEEM images show p-n contrast on device test structures• Microsystems reliability and failure analysis is pushing to the nanoscale

David Stein, 845-8476

Gary Kellogg, 844-2079

Gary Kellogg, 844-2079

Todd Alam, 844-1225

John Sullivan, 845-9496

Brian Swartzentruber, 844-6393

Brian Swartzentruber, 844-6393

Todd Monson, 845-2129

Jianyu Huang, 284-5963

Jack Houston, 844-8939

Julia Hsu, 284-1173

Julia Hsu, 284-1173

Julia Hsu, 284-1173

Contact information is on the poster.