Vertical MWNTs
We have shown the synthesis of self-oriented multi-walled
carbon nanotube arrays [Fan et al., Science, 1999], demonstrating for
the first time that nanotube materials can be synthesized in patterned
and self-aligned fashions. This work has led to much follow up for vertically
aligned carbon nanotube synthesis.
SWNTs by CVD for Integration.
We developed synthesis methods for highly quality single-walled carbon
nanotubes (SWNTs) by chemical vapor deposition (CVD) and their patterned
growth on substrates. This work has enabled a deterministic synthesis
of arrays of addressable electrical devices of individual nanotube quantum
wires [Kong et al., Nature, 1998; Soh et al., Appl. Phys. Lett., 1999;],
and has now been used by groups worldwide for synthesis of SWNTs for
quantum transport and other mesoscopic physics studies.
SWNT growth Control.
We have made much new progress lately in synthesis, including single
particle patterning for SWNT growth [A. Javey et al, JACS, 2006] and
vertical SWNT mats on 4-inch wafer scale [G. Zhang, PNAS, 2005]. We
have also achieved 90% semiconducting SWNT synthesis by a plasma PECVD
method [Y. Li, Nano Lett., 2004].
Self-Oriented Vertical Single-Walled NTs
Self-Oriented Vertical Multi-Walled NTs
Suspended Nanotubes
Alan Cassell, Nathan Franklin, JACS, Adv. Mat., 1999-2000
SWNTs Synthesis From Individual Nanoparticles
(1.2) Electrical, mechanical, electromechanical, electro-thermal and electro-optical properties of single nanotube molecules.
NanoElectromechanics.With the advance in the synthesis of high quality SWNTs, we have made some original measurements on nanotubes including electromechanical investigation of single-walled nanotubes that to uncover the influence of mechanical deformation to electron transport in these materials [Tombler, Nature, 2000; Cao, PRL, 2003].
Quantum transport down to 300mK.
Suspended SWNTs are our favorite systems
for synthesis [Cassell, JACS, 1999; Franklin, 2000] as well as for various
quantum transport measurements. We found that these tubes (in as-grown
form between metal pads) are the 'cleanest' SWNT devices. The clean
quantum transport data has allowed us to elucidate the Aharonov Bohm
effect for SWNTs in the ballistic Fabry Perot transport regime (with
ohmic contacts) [Cao, PRL, 2004 & Nature Materials, 2005]. Suspended
SWNT devices are now made in many groups for not only electrical transport
but also spectroscopy research.
Ballistic transport.
We are among the first to measure near 4e2/h quantum
conductance in a single nanotube to prove ballistic transport in these
materials and the high material quality for CVD grown SWNTs [Kong, PRL,
2001].
For high bias transport, we showed quasi-ballistic transport in ultra-short
nanotubes at high biases or energies, overcoming the optical phonon
scattering limitation by length scaling [Javey, PRL, 2004; PNAS, 2004].
Thermal and electro-thermal transport
We explore single-walled nanotube
(SWNT) transport via "suspended" and "on-substrate"
devices. By fabricating and measuring devices with a variety of length
and diameter scales, we study the limits of electronic transport and
the phenomena that arise in that regime. In suspended nanotubes, we
previously determined the existence extreme self-heating and non-equilibrium
optical phonons [Pop et al. PRL 2005] and the strong effect of environment
on these phenomenon [Mann et al. JPCB 2006]. With high quality contacts
and the unperturbed nature of suspended SWNTs, we have the opportunity
to study SWNTs in a state of extreme self-heating in many environments,
which gives us insight into fundamental properties of the specific SWNT,
including the temperature dependence of the thermal conductivity, and
the strength of the coupling between hot phonons and the environment.
Unifying the "on-substrate" and "suspended" transport
models allows us to design new and better substrates to improve heat
sinking and phonon coupling, leading to better device reliability and
potentially higher peak currents than previously observed.
Self-Oriented Vertical Single-Walled NTs
Electromechanical Properties of Suspended Nanotubes
Thomas Tombler, Chongwu Zhou, et al., Nature,
2000; Jien Cao , et al., PRL, 2004.
Suspended Nanotubes: Very High Quality &
Unperturbed
As-grown between Pt across trenches Exhibit 'clean'
quantum transport signatures.
Quantum Transport (Aharonov Bohm Effect)
Non-Equilibrium Hot Phonons in Suspended Tubes
