Transcript MOSFET Strain Enhanced Channels for Measurements

Thermal Conduction
Coefficient in Single Wall
Carbon Nanotubes
David R. Myers
February 21, 2007
EE 235
Bulk Thermal Conductivity
T
T
q   kA
  kA
x
x
Heat  x
k
Tim e A  T
•
TH
k
TC
Typical Values
– Air 26.3 X 10-3 W/mK
– Glass 1.4 W/mK
– Gold 317 W/mK
– Graphite 1950 W/mK
– Diamond 2300 W/mK
T
x
Δx
Microscopic Theory
• Thermal conductivity governed through free electrons
interactions and phonons
• Carbon nanotubes have very low scattering at the
boundaries and thus high thermal conductivities
Conserves Phonon
Momentum
Changes Phonon
Momentum
• Quantum of Thermal Conductance
g 0
 2 kb2T
3h
Testing Apparatus Fabrication
and Function
• Heat one side
• Measure the other resulting temperature
• Use Q=(kA)(ΔT)
Measuring Thermal Conductivity
Nanowire Placement:
• Sharp Probe to pick up sample
• Nanowire Solution Spun on wafer
• CVD to grow individual nanowires
across gap
Cool Tricks for CVD:
• Old - Spin solution onto wafer
with catalyst nanoparticles
• New – Sharp probe to directly
deliver solutions onto
membrane
Results
Diamond
Gold
• Don’t really know the nanotube thickness, but makes a big difference
• In any case, outperforms diamond
• Umklapp Scattering is weak in 2.76 μm 1-3 nm CNT
• Notice increasing temperature gives increasing conductivity (will
continue until scattering dominates
Questions?