A study of thermal chemical vapor deposition (CVD) grown carbon nanotubes (CNTs) field emitters in a triode amplifier configuration is reported. The CNT transistor characteristics were examined by integrating gate and...
A study of thermal chemical vapor deposition (CVD) grown carbon nanotubes (CNTs) field emitters in a triode amplifier configuration is reported. The CNT transistor characteristics were examined by integrating gate and anode with CNT cathode in two structural forms, utilizing a TEM grid (transmission electron microscope specimen holder) as the gate electrode and a micropatterned CNT with self-aligned gate. The TEM-grid CNT triode displayed clearly gate-controlled current modulation behavior with distinct cutoff, linear, and saturation regions, and a reasonable gate turn-on field of ∼5.4V∕μm despite a large cathode-gate spacing of ∼120μm . The field emission result established the basic transistor characteristics of CNTs in a triode configuration. A CNT triode construct with a self-aligned gated fabrication technique was also developed to realize a monolithic triode structure with shorter gate-cathode spacing, lowering gate voltage, and enhancing emission current. The triode exhibited a significantly lower gate turn-on voltage of ∼40V , and gate-controlled modulation of the emission current. An anode current density of ∼30mA∕cm2 was achieved at a gate voltage of ∼80V and an anode voltage of ∼200V . The dc characteristics for both of the CNT triodes were investigated, including Ia versus Va for different Vg . Moreover, dc parameters such as transconductance, amplification factors, and anode resistance of the triode amplifier were determined. The CNT triodes exhibited useful amplification factor and high output impedance.
The advent of semiconductor devices with nanoscale dimensions creates the potential to integrate nanoelectronics and optoelectronic devices with a great variety of biological systems. Moreover, the advances in nanotec...
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In this paper, vertically aligned carbon nanotubes field emission devices were fabricated from the as grown carbon nanotubes (CNTs) by furnace thermal CVD at atmospheric pressure. The device was tested in vacuum (/spl...
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In this paper, vertically aligned carbon nanotubes field emission devices were fabricated from the as grown carbon nanotubes (CNTs) by furnace thermal CVD at atmospheric pressure. The device was tested in vacuum (/spl sim/10/sup -6/ torr) for field emission characterization. The turn-on field was about 3 V//spl mu/m, which is comparable to data reported elsewhere.
Most edge detection algorithms include three main stages: smoothing, differentiation, and labeling. In this paper, we evaluate the performance of algorithms in which competitive learning is applied first to enhance ed...
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Most edge detection algorithms include three main stages: smoothing, differentiation, and labeling. In this paper, we evaluate the performance of algorithms in which competitive learning is applied first to enhance edges, followed by an edge detector to locate the edges. In this way, more detailed and relatively more unbroken edges can be found as compared to the results when an edge detector is applied alone. The algorithms compared are K-Means, SOM and SOGR for clustering, and Canny and GED for edge detection. Perceptionally, best results were obtained with the GED-SOGR algorithm. The SOGR is also considerably simpler and faster than the SOM algorithm.
Semi-analytical models are used to simulate the response of periodic-field electro quasistatic dielectrometry sensors. Due to the periodic structure of the sensors it is possible to use Fourier series methods in combi...
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Semi-analytical models are used to simulate the response of periodic-field electro quasistatic dielectrometry sensors. Due to the periodic structure of the sensors it is possible to use Fourier series methods in combination with collocation point numerical techniques to generate accurate sensor simulations much more efficiently than with the more general finite-element methods. Previously, collocation-point models used to compute the response of periodic field dielectric sensors, also known as Interdigitated Electrode Dielectrometers (IDED), have ignored the contribution of the constant (zero-order) term in the Fourier series expansion of the physical quantities. This is justifiable if the top dielectric material layer under test is infinitely thick, with any top ground plane bounding the dielectric removed too far from the sensor to influence its response. This is the assumption generally made until now in the application of these models. In practice, however, it is impossible to eliminate the cumulative effect of objects at ground potential in the vicinity of the sensor, which in general manifests itself as a ground plane electrode positioned at some effective distance within the top dielectric layer (usually air). In order to eliminate this source of uncertainty in the measurements, we suggest that a grounded electrode be explicitly placed at the top of the dielectric layer in the experimental setup, and its presence be accounted for in the models. Furthermore, in many cases, such as measurements on ceramic thermal barrier coatings, a metal layer is already present behind the material under test. In this paper we present how the models must be modified to account for this ground plane, and what effect it has on the dependence of the sensor response on the material properties. For example, the sensor transcapacitance may no longer be a monotonically increasing function of the material's permittivity, leading to nonuniqueness in permittivity measurements, as some f
The effects of deposition parameters and NH3 pretreatment on the size and distribution of Pd catalytic particles and subsequently their effects on the characteristics of the synthesized carbon nanotubes (CNTs) were sy...
The effects of deposition parameters and NH3 pretreatment on the size and distribution of Pd catalytic particles and subsequently their effects on the characteristics of the synthesized carbon nanotubes (CNTs) were systematically investigated. It was found that the size of Pd particles decreases and the particle density (total number of Pd particles per unit area) increases as the Pd film thickness decreases. Moreover, pretreatment of Pd film in NH3 gas promotes smaller Pd particles and higher particle density which is beneficial for CNT growth. The CNTs were synthesized by thermal chemical vapor deposition at 750 °C using methane (CH4) as the carbon source, and a mixture of Ar/H2 (80 vol %: 20 vol %) as a carrier gas with NH3 serving as a processing reagent. The incorporation of NH3 in CNT synthesis, per the specific pretreatment of catalytic film, has a distinct effect on the size and morphology of CNTs produced. The interrelation between processing, structure and emission behavior of CNTs produced with different synthesis conditions was examined by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and field emission measurements.
Molecular dynamics simulations are performed on parallel computers to investigate the crystalline Si(111)∕Si3N4(0001) interface that is modeled as an eight-component system. The average total energy per particle and ...
Molecular dynamics simulations are performed on parallel computers to investigate the crystalline Si(111)∕Si3N4(0001) interface that is modeled as an eight-component system. The average total energy per particle and the average kinetic energy per particle of the subsystems are monitored during the preparation of the system. The Young’s modulus of the interface is compared with that of the silicon part alone and that of the silicon-nitride film, respectively. The results for one extended simulation feature a crack in the silicon-nitride film and dislocated atoms in silicon below the crack. Simulations at rates of strain ranging from 0.00125to0.05ps−1 show that for lower strain rates, the systems stretched faster reach their ultimate strength at a higher strain value than those that were stretched more slowly. At the highest strain rates, however, the failure mechanisms change qualitatively indicative of a more ductile behavior.
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