This PDF file contains the front matter associated with SPIE
Proceedings Volume 7399, including the Title Page, Copyright
information, Table of Contents, Introduction (if any), and the
Conference Committee listing.
We investigated the effects of hydrogen pretreatment on nickel catalyst of different thicknesses and deposition
methods on a silicon substrate and how it will affect the growth of carbon nanotubes using microwave plasma
enhanced chemical vapor deposition (MPECVD). Nickel catalyst of 10, 50, 100, 200, 350 and 500 Å thickness
was treated with hydrogen flowing at 135 standard cubic centimeter per minute (sccm), substrate temperature
of 400 °C, microwave power of 400 W, and pressure of 20 torr. The treated catalyst granule size and density was
determined optically through scanning electron microscope (SEM) images and atomic force microscope (AFM)
measurements. We found that sputtered catalyst needs a longer pretreatment than evaporated catalyst. As
expected, the pretreatment time must be increased as the catalyst thickness increases to get granule sizes and
densities favorable for carbon nanotube (CNT) growth. CNT growth took place with a hydrogen flow of 120
sccm, methane flow of 15 sccm, substrate temperature of 650 °C, microwave power of 1000 W and a pressure
of 20 torr. We determined the catalyst can be over treated causing catalyst conglomeration that result in poor
We have developed a simple and unique metal-free chemical vapor deposition technique in mild condition for the
synthesis of carbon nanotubes on carbon black and graphite surfaces. The existence of topologically heterogeneous
surfaces is a key factor for inducing the growth of the CNTs. Surface functional groups also play an important role in
manipulating the reaction path of the carbon deposition reaction. A surface structure-related model was proposed to
describe the growth procedure of CNTs on carbon surfaces. We anticipate that this method will be useful for controlling
the growth of metal-free CNTs at desired sites on various carbon surfaces.
We demonstrate doping-free and adaptive inverter to verify that the single ambipolar SWCNT transistors can be utilized both p- and n-type. Furthermore, we fabricate an adaptive logic circuit that can reveal multifunctions such as NOR and NAND gate using four ambipolar transistors. This new approach is innovative in several aspects, for instance, in improving integration density, simplicity without intentional doping, and its multifunctionality and ensures multidisciplinary interests in materials, physics, mechanics, and electronics areas.
The effect of using EBL with devices incorporating CNT has also been investigated. The effect on metallic and
semiconducting CNT exposure in the channel of the transistor devices was examined and a physical mechanism for the
variations discussed. We show that the subsequent generation of trap states along the CNT channel varies the conduction
mechanism of the nanotube and has a significant effect on device performance. Metallic and semiconducting CNT react
very differently, with an apparent increased localization effect in the metallic tubes responsible for dramatic decreases in
Our study deals with the utilization of carbon nanotubes networks based transistors with different metal
electrodes for highly selective gas sensing. Indeed, carbon nanotubes networks can be used as semi
conducting materials to achieve good performances transistors. These devices are extremely sensitive to the
change of the Schottky barrier heights between Single Wall Carbon Nanotubes (SWCNTs) and drain/source
metal electrodes: the gas adsorption creates an interfacial dipole that modifies the metal work function and so
the bending and the height of the Schottky barrier at the contacts. Moreover each gas interacts specifically
with each metal identifying a sort of electronic fingerprinting. Using airbrush technique for deposition, we
have been able to achieve uniform random networks of carbon nanotubes suitable for large area applications
and mass production such as fabrication of CNT based gas sensors. These networks enable us to achieve
transistors with on/off ratio of more than 5 orders of magnitude. To reach these characteristics, the density of
the CNT network has been adjusted in order to reach the percolation threshold only for semi-conducting
nanotubes. These optimized devices have allowed us to tune the sensitivity (improving it) of our sensors for
highly selective detection of DiMethyl-Methyl-Phosphonate (DMMP, a sarin stimulant), and even volatile
drug precursors using Pd, Au and Mo electrodes.
Nanodispersion of single-walled carbon nanotubes (SWCNTs) has been systematically investigated with the use of
sodium dodecyl sulfate (SDS) and poly(vinylpyrrolidone) (PVP) surfactant in de-ionized water. A high concentration of
nanodispersed SWCNTs up to 0.08 mg/mL was achieved with introduction of an additional dispersant of PVP by
optimizing surfactant concentration, sonication time, and centrifugation speed, which was crucial to obtaining a high
concentration of SWCNTs in the supernatant solution. We also demonstrate that diameters of the nanodispersed
nanotubes can be sorted out by controlling the centrifugation speed and furthermore the saturated SWCNT concentration
was nearly constant, independent of the initial concentration at high centrifugation speed. Two dispersion states were
identified depending on the centrifugation speed: an intermediate dispersion of nanodispersion mixed with
macrodispersion (I) and nanodispersion (II). This was verified by Raman spectroscopy, scanning probe microscopy,
optical absorption spectroscopy, and photoluminescence measurements. The obtained SWCNT solution was stable up to
about ten days. Some aggregated SWCNT solution after a long period of time was fully recovered to initial state of
dispersion after re-sonication for a few minutes. Our systematic study on high concentration nanodispersion of SWCNTs
with selective diameters provides an opportunity to extend the application areas of high quality SWCNTs in large
The novel thermal conductance mechanism, theoretically predicted and experimentally measured in nanotube
field-effect transistors (FET), is discussed with respect to the power dissipation problem of modern carbon-based
electronics. Such an effect is due to the near-field coupling of the charge carriers in the transistor channel with
the local electric field of the surface electromagnetic modes. The coupling leads to a quantum electrodynamic
(QED) energy exchange between the hot electrons in FET channel and the optical polar phonon bath being in
thermal equilibrium with the substrate. For an example of a NT on silica, this QED coupling mechanism is
shown to exceed significantly the interface Kapitza conductance, that is, the classical phonon heat transport.
The QED thermal conductance is proposed to play dominant role in the energy dissipation in nanoelectronics
with a hetero-interface between the device channel and the polar substrate.
In this paper, we propose a new design configuration for a carbon nanotube (CNT) array based pulsed field
emission device to stabilize the field emission current. In the new design, we consider a pointed height distribution
of the carbon nanotube array under a diode configuration with two side gates maintained at a negative potential
to obtain a highly intense beam of electrons localized at the center of the array. The randomly oriented CNTs are
assumed to be grown on a metallic substrate in the form of a thin film. A model of field emission from an array of
CNTs under diode configuration was proposed and validated by experiments. Despite high output, the current in
such a thin film device often decays drastically. The present paper is focused on understanding this problem. The
random orientation of the CNTs and the electromechanical interaction are modeled to explain the self-assembly.
The degraded state of the CNTs and the electromechanical force are employed to update the orientation of the
CNTs. Pulsed field emission current at the device scale is finally obtained by using the Fowler-Nordheim equation
by considering a dynamic electric field across the cathode and the anode and integration of current densities
over the computational cell surfaces on the anode side. Furthermore we compare the subsequent performance of
the pointed array with the conventionally used random and uniform arrays and show that the proposed design
outperforms the conventional designs by several orders of magnitude. Based on the developed model, numerical
simulations aimed at understanding the effects of various geometric parameters and their statistical features on
the device current history are reported.
Since it was isolated in 2004, graphene, the first known 2D crystal, is the object of a growing interest, due to the range of its possible applications as well as its intrinsic properties. From large scale electronics and photovoltaics to spintronics and fundamental quantum phenomena, graphene films have attracted a large community of researchers. But bringing graphene to industrial applications will require a reliable, low cost and easily scalable synthesis process. In this paper we present a new growth process based on plasma enhanced chemical vapor deposition. Furthermore, we show that, when the substrate is an oxidized silicon wafer covered by a nickel thin film, graphene is formed not only on top of the nickel film, but also at the interface with the supporting SiO2 layer. The films grown using this method were characterized using classical methods (Raman spectroscopy, AFM, SEM) and their conductivity is found to be close to those reported by others.
The need to have a complete control of the length of the carbon nanotubes is one of the most limiting factor in
using nanotubes based devices. In fact their treatments often lead to have different length distribution involving
therefore different properties. In this work we aim at controlling the length of the nanotubes adjusting the
oxidation temperature. Temperature dependence of SWNTs oxidation was analyzed by Raman spectroscopy.
AFM images shows the height of micropatterned self-assembled monolayers of carboxylated SWNTs. SWNTs
forest with different height could be fabricated controlling oxidation temperature in the range of 303K-313K.
Highly crystalline few-graphene layers were synthesized on poly-nickel, Ni(111) and Ni-deposited substrates by
optimizing the mixing ratio of C2H2/H2 and C2H4/H2 and growth time. The hydrogen effect was investigated to minimize
defects and maintain uniformity of the synthesized few-layer graphenes. Using the optimized ratio of hydrogen and
acetylene mixture, few graphene layers with large sizes of up to 4 inches in diameter were also synthesized on Ni
evaporated Si substrate with different thicknesses and were transferred successfully onto PET film. We also found that
the wrinkles, different from inherent ripples, were formed in the graphene layer independent of the location of the grain
boundary of poly-Ni substrate and growth conditions. This was attributed to the formation of a step terrace followed by
the terrace bunching to result in higher wrinkles due to the thermal mismatch existing between Ni substrate and graphene
layers during thermal quenching. A sheet resistance of 233 Ω/sq was obtained at a transmittance of 65%.
This paper investigates the radiation characteristics of a Vee dipole antenna operating in the near infra-red and optical
frequency regimes. Antenna properties, such as far-field radiation patterns, coupling coefficient, measured by the
scattering parameter S11, and directivity are provided. The resonance and directivity behavior of the optical Vee dipole,
which is based on Multi-Wall Carbon Nano Tube (MWCNT), are investigated by varying the dipole length in order to
exploit the effective operating frequency in the near infra-red range (~120 to 400 THz) and the visible light range (~400-
750 THz). Moreover, a parametric study aimed at optimizing the antenna directivity is performed by varying the angle
between the two arms of the dipole using CST Microwave Studio simulation software which is based on the Finite
Integration Technique (FIT). The proposed antenna achieved a directivity 3.767 dB higher than the traditional dipole in
the visible regime while maintaining the same directivity in the near infrared regime.