Nanostructure Enhanced Terahertz Technology for Sensing and Imaging
Seongsin Margaret Kim, Babatunde Ajilore, Gang Shen, Dave Wilbert, and Patrick Kung
Supported by NSF DMR-0821704 and EEC-0824452
TERAHERTZ FOR SENSING AND IMAGING
¾Material fundamental properties
studies (metamaterials, quantum
nonlinear dynamics)
¾Biomedical imaging
¾Gas sensing, gas phase spectroscopy
¾Biological agent, explosive detection
NANOSTRUCTURE SYNTHESIS AND
CHARACTERIZATION
¾Unique custom designed MOVPE
reactor
¾Specifically designed for wide
bandgap semiconductors and
nanostructures
THz-TDS System:
¾Broadband THz signal
upto 3THz
Biomedical imaging, S.M. Kim et al, (2005) ¾High dynamic range
III-NITRIDE NANOSTRUCTURES
THz NANOSTRUCTURE CHARACTERIZATION
and COMPACT THz SOURCES
¾ The time-resolved photoinduced conductivity
¾ Nanowires/rods have a significantly
can be obtained from the differential terahertz
increased smooth emitting surface area
transmission
¾ Diameters can be on the order of the
accumulation layer thickness.
Advantages of InGaN for THz:
•Engineerable bandgap (λ=365~1775 nm)
•High saturation & peak drift
velocity
•Short carrier lifetime
•High breakdown electric field
∆σ (τ ) =
T (ω ) =
1 + n s ∆T
δZ 0 E T(ω )
ES (ω )
e iφ s ( ω )
= S
Er (ω ) Er (ω ) e iφr (ω )
cd
[φs (ω ) − φr (ω )]
ω
¾New method of nanomaterials Parkinson et al, (2007)
characterization:charge transfer in photovoltaic
solar cell
∆n(ω ) = −
THz NANOSTRUCTURE CHARACTERIZATION
Being a non-contact optical
method, THz time domain
spectroscopy is an ideal method
to characterize the electrical
properties of semiconductor
nanostructures, including
carrier densities and
conductivity.
¾ The time-resolved photoinduced conductivity
can be obtained from the differential terahertz
transmission
1 + ns ∆T
∆σ (τ ) =
δZ 0 T
ES (ω ) ES (ω ) eiφs (ω )
T (ω ) =
=
Er (ω ) Er (ω ) e iφr (ω )
ES (ω )
2
α (ω ) = − ln
rd
Er (ω )
cd
∆n(ω ) = − [φs (ω ) − φr (ω )]
ω
Parkinson et al, Nano Lett. (2007)
A. Huber et al, Nano Lett. (2008)
¾ Application of various THz spectroscopy
technology
¾ New method of nanomaterials characterization:
-Nanomagnetic materials, spintronic devices
-Probe for charge transfer in photovoltaic solar
cells
-Carbon Nanotube