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Thermal and Thermoelectric Characterization of Nanostructures. Li Shi, PhD Assistant Professor Department of Mechanical Engineering & Center for Nano and Molecular Science and Technology, Texas Materials Institute The University of Texas at Austin

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Thermal and Thermoelectric Characterization of Nanostructures


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thermal and thermoelectric characterization of nanostructures

Thermal and Thermoelectric Characterization of Nanostructures

Li Shi, PhD

Assistant Professor

Department of Mechanical Engineering &

Center for Nano and Molecular Science and Technology,

Texas Materials Institute

The University of Texas at Austin

Tutorial on Micro and Nano Scale Heat Transfer, 2003 IMECE

outline
Outline
  • Scanning Thermal Microscopy of Nanoelectronics
  • Thermoelectric Measurements of Nanostructures
slide3

Silicon Nanoelectronics

  • Heat dissipation influences speed and reliability
  • Device scaling is limited by power dissipation

IBM Silicon-On-Insulator (SOI) Technology

carbon nanoelectronics
Carbon Nanoelectronics

TubeFET (McEuen et al., Berkeley)

Nanotube Logic (Avouris et al., IBM)

  • Current density: 109 A/cm2
  • Ballistic charge transport

V

-

thermometry of nanoelectronics
Thermometry of Nanoelectronics

Techniques Spatial Resolution

Infrared Thermometry 1-10 mm*

Laser Surface Reflectance 1 mm*

Raman Spectroscopy 1 mm*

Liquid Crystals 1 mm*

Near-Field Optical Thermometry < 100 nm Scanning Thermal Microscopy (SThM) < 100 nm

*Diffraction limit for far-field optics

scanning thermal microscopy

Thermal

Topographic

Z

T

X

X

Scanning Thermal Microscopy

Atomic Force Microscope (AFM) + Thermal Probe

Laser

Deflection

Sensing

Cantilever

Temperature sensor

Sample

X-Y-Z

Actuator

microfabricated thermal probes

10 mm

Microfabricated Thermal Probes

Pt Line

Tip

Pt-Cr

Junction

Laser Reflector

SiNx Cantilever

Cr Line

Shi, Kwon, Miner, Majumdar, J. MicroElectroMechanical Sys., 10, p. 370 (2001)

slide8

Thermal Imaging of Nanotubes

Thermal

30

10

10

20

5

5

Height (nm)

Height (nm)

30 nm

30 nm

10

0

0

0

-400

-200

0

200

400

-400

-400

-200

-200

0

0

200

200

400

400

Distance (nm)

Distance (nm)

Multiwall Carbon Nanotube

Topography

Topography

3 V

m

88

A

m

m

1

1

m

m

Spatial Resolution

V)

m

50 nm

Thermal signal (

Distance (nm)

Shi, Plyosunov, Bachtold, McEuen, Majumdar, Appl. Phys. Lett., 77, p. 4295 (2000)

metallic single wall nanotube

Low bias:

Ballistic

High bias:

Dissipative (optical

phonon emission)

Metallic Single Wall Nanotube

Topographic

Thermal

DTtip

A

B

C

D

2 K

0

1 mm

polymer coated nanotubes
Polymer-coated Nanotubes

Topography

Thermal

After coating

Before coating

-2 V, 4.4 mA

2 V, 7.8 mA

1 mm

GND

GND

  • Asymmetric heating at the two contacts

The polymer melted at a ~3V bias

slide11

Future Challenge:

Temperature Mapping of Nanotransistors

SOI Devices

SiGe Devices

  • Low thermal conductivities of SiO2 and SiGe
  • Interface thermal resistance
  • Short (10-100 nm) channel effects (ballistic transport, quantum transport)
  • Phonon “bottle neck” (optical-acoustic phonon decay length > channel length)
  • Few thermal measurements are available to verify simulation results
thermal transport in nanostructures
Thermal Transport in Nanostructures

Carbon Nanotubes

Hot

Cold

p

  • Long mean free path l
  • Strong SP2 bonding: high sound velocity v
  •  high thermal conductivity:k = Cvl/3~ 6000 W/m-K
  • Below 30 K, thermal conductance  4G0 = ( 4 x 10-12T) W/m-K, linear T dependence (G0 :Quantum of thermal conductance)

Heat capacity

semiconductor nanowires
Semiconductor Nanowires

Nano-patterned Si Nanotransistor

(Berkeley Device group)

VLS-grown Si Nanowires

(P. Yang, Berkeley)

Gate

Drain

Source

Nanowire Channel

Hot Spots

  • Increased phonon-boundary scattering
  • Modified phonon dispersion
  •  Suppressed thermal conductivity
  • Ref: Chen and Shakouri, J. Heat Transfer 124, 242

Hot

p

Cold

efficient peltier cooling using nanowires
Efficient Peltier Cooling using Nanowires

Bi

Nanowires

Thermoelectric figure of merit:

Low k  high COP

Dresselhaus et al., Phys. Rev. B. 62, 4610

thermal measurements of nanostructures

Q

I

Thermal Measurements of Nanostructures

Suspended SiNx membrane

Long SiNx beams

Pt resistance thermometer

Kim, Shi, Majumdar, McEuen,Phys. Rev. Lett. 87, 215502

Shi, Li, Yu, Jang, Kim, Yao, Kim, Majumdar, J. Heat Tran 125, 881

sample preparation

Pipet

Nanostructure suspension

Spin

  • Direct CVD growth
  • Dielectrophoretic trapping
Sample Preparation
  • Wet deposition

Chip

SnO2 nanobelt

Nanotube bundle

Individual Nanotube

thermal conductance measurement
Thermal Conductance Measurement

T

-

1

-

1

-

1

G

T

G

G

h

s

b

b

T

T

0

0

Q

2QL

Q

h

measurement errors and uncertainties

Size

-- Thickness: 1 nm uncertainty in tapping mode AFM

d/d = 10 % for d = 10 nm

d/d = 50 % for d = 2 nm (individual SWCN) Raman Spectroscopy

Measurement Errors and Uncertainties
  • Contact Resistance

~ d

~ d 2

-- G-1Sample /G-1Contact decreases with d, and is estimated to larger than 10 for measurements reported here

carbon nanotubes
Carbon Nanotubes

CVD SWCN

  • An individual nanotube has a high k~ 2000-11000 W/m-K at 300 K
  • The diameter and chirality of a CN may be probed using Raman spectroscopy
  • k of a CN bundleis reduced by thermal resistance at tube-tube junctions
sno 2 nanobelts
SnO2 Nanobelts

Phonon scattering rate:

64 nm

64 nm

53 nm

39 nm

Umklapp Boundary Impurity

Collaboration:

N. Mingo, NASA Ames

tU-1 = tU,bulk-1

ti-1 = ti,bulk-1

tb-1 = v/FL

v: phonon group velocity

FL: effective thickness

53 nm

53 nm,

ti-1 =10t-1i, bulk

Circles: Measurements

Lines: Simulation using a Full Dispersion Transmission Function approach

  • Phonon-boundary scattering is the primary effect determining the suppressed thermal conductivities

Shi, Hao, Yu, Mingo, Kong, Wang, submitted

si nanowires
Si Nanowires

Symbols: Measurements

Lines: Simulation using a modified Callaway method

  • Phonon-boundary scattering is the primary effect determining the suppressed thermal conductivities except for the 22 nm sample, where boundary scattering alone can not account for the measurement results.

Li, Wu, Kim, Shi, Yang, Majumdar, Appl. Phys. Lett. 83, 2934 (2003)

seebeck coefficient

Th

Seebeck Coefficient

S = VTE / (Th –Ts)

I

  • Oxygen doped
  • Quasilinear (metallic) behavior
  • Phonon drag effect at low T

Ts

VTE

slide23

Future Challenge:Nanomanufacturing of Nanowire Arrays as Efficient Peltier Devices

  • Nano- imprint Pattering of Thermoelectric Nanowire Arrays

10 nm Cr nanowire array

40 nm Cr nanowire array

  • Test-bed Peltier devices for cooling IR sensors
slide24

Summary

  • Scanning Thermal Microscopy of Nanoelectronics:
  • -- Thermal imaging with 50 nm spatial resolution
  • Thermoelectric (k, s, S) Measurements of Nanostructures Using a Microfabricated Device:
  • -- Super-high k of nanotubes
  • -- Suppressed k of nanowires
acknowledgment

Acknowledgment

Students:

Choongho Yu; Jianhua Zhou; Qing Hao; Rehan Farooqi; Sanjoy Saha;

Anastassios Marvrokefalos; Anthony Hayes; Carlos Vallalobos

Collaborations:

UC Berkeley: Arun Majumdar; Deyu Li (now at Vanderbilt); Philip Kim (now at Columbia); Paul McEuen (now at Cornell); Adrian Bachtold (now at Paris); Sergei Plyosunov

UT Austin: C. K. Ken Shih & Ho-Ki Lyeo; Zhen Yao; Brian Korgel

GaTech: Z. L. Wang

NASA: Natalio Mingo

UCSC: Ali Shakouri

MIT: Rajeev Ram & Kevin Pipe

Support:

NSF CTS (CAREER; Instrumentation)