12,935 research outputs found
The Effect of Carbon Nanotube/Organic Semiconductor Interfacial Area on the Performance of Organic Transistors
We show that the performance of pentacene transistors can be significantly
improved by maximizing the interfacial area at single walled carbon nanotube
(SWCNT)/pentacene. The interfacial areas are varied by anchoring short SWCNTs
of different densities (0-30/{\mu}m) to the Pd electrodes. The average mobility
is increased three, six and nine times for low, medium and high SWCNT
densities, respectively, compared to the devices with zero SWCNT. The current
on-off ratio and on-current are increased up to 40 times and 20 times with
increasing the SWCNT density. We explain the improved device performance using
reduced barrier height of SWCNT/pentacene interface.Comment: 9 pages, 7 figures, 1 tabl
Self-repairing in single-walled carbon nanotubes by heat treatment
Structure transformation by heat treatment in single-walled carbon nanotubes
(SWCNT) is investigated using molecular dynamics simulation. The critical
temperature for the collapse of pure SWCNT is as high as 4655 K due to strong
covalent carbon-carbon bonding. Above 2000 K, the cross section of SWCNT
changes from circle to ellipse. The self-repairing capability is then
investigated and two efficient processes are observed for the SWCNT to repair
themselves. (1) In the first mechanism, vacancy defects aggregate to form a
bigger hole, and a bottleneck junction is constructed nearby. (2) In the second
mechanism, a local curvature is generated around the isolate vacancy to smooth
the SWCNT. Benefit from the powerful self-repairing capability, defective SWCNT
can seek a stable configuration at high temperatures; thus the critical
temperature for collapse is insensitive to the vacancy defect density.Comment: accepted by Journal of Applied Physic
Low temperature fullerene encapsulation in single wall carbon nanotubes: synthesis of N@C@SWCNT
High filling of single wall carbon nanotubes (SWCNT) with C and
C fullerenes in solvent is reported at temperatures as low as 69
C. A 2 hour long refluxing in n-hexane of the mixture of the fullerene
and SWCNT results in a high yield of C,C@SWCNT, fullerene peapod,
material. The peapod filling is characterized by TEM, Raman and electron energy
loss spectroscopy and X-ray scattering. We applied the method to synthesize the
temperature sensitive (N@C:C)@SWCNT as proved by electron spin
resonance spectroscopy. The solvent prepared peapod samples can be transformed
to double walled nanotubes enabling a high yield and industrially scalable
production of DWCNT
Migration of a Carbon Adatom on a Charged Single-Walled Carbon Nanotube
We find that negative charges on an armchair single-walled carbon nanotube
(SWCNT) can significantly enhance the migration of a carbon adatom on the
external surfaces of SWCNTs, along the direction of the tube axis. Nanotube
charging results in stronger binding of adatoms to SWCNTs and consequent longer
lifetimes of adatoms before desorption, which in turn increases their migration
distance several orders of magnitude. These results support the hypothesis of
diffusion enhanced SWCNT growth in the volume of arc plasma. This process could
enhance effective carbon flux to the metal catalyst
Giant Electron-hole Charging Energy Asymmetry in Ultra-short Carbon Nanotubes
Making full usage of bipolar transport in single-wall carbon nanotube (SWCNT)
transistors could permit the development of two-in-one quantum devices with
ultra-short channels. We report on clean 10 to 100 nm long suspended
SWCNT transistors which display a large electron-hole transport asymmetry. The
devices consist of naked SWCNT channels contacted with sections of
SWCNT-under-annealed-gold. The annealed gold acts as an n-doping top gate which
creates nm-sharp barriers at the junctions between the contacts and naked
channel. These tunnel barriers define a single quantum dot (QD) whose charging
energies to add an electron or a hole are vastly different ( charging
energy asymmetry). We parameterize the transport asymmetry by the ratio
of the hole and electron charging energies . We show that this
asymmetry is maximized for short channels and small band gap SWCNTs. In a small
band gap SWCNT device, we demonstrate the fabrication of a two-in-one quantum
device acting as a QD for holes, and a much longer quantum bus for electrons.
In a 14 nm long channel, reaches up to 2.6 for a device with a
band gap of 270 meV. This strong transport asymmetry survives even at
room temperature
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