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Investigation on the Plasma-Induced Emission Properties of Large Area Carbon Nanotube Array Cathodes with Different Morphologies

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ABSTRACT

Large area well-aligned carbon nanotube (CNT) arrays with different morphologies were synthesized by using a chemical vapor deposition. The plasma-induced emission properties of CNT array cathodes with different morphologies were investigated. The ratio of CNT height to CNT-to-CNT distance has considerable effects on their plasma-induced emission properties. As the ratio increases, emission currents of CNT array cathodes decrease due to screening effects. Under the pulse electric field of about 6 V/μm, high-intensity electron beams of 170–180 A/cm2 were emitted from the surface plasma. The production mechanism of the high-intensity electron beams emitted from the CNT arrays was plasma-induced emission. Moreover, the distribution of the electron beams was in situ characterized by the light emission from the surface plasma.

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The side view FESEM images of four kinds of arrays with different CNT heights: a 4 μm, b 7 μm, c 14 μm, d 16 μm.
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Figure 2: The side view FESEM images of four kinds of arrays with different CNT heights: a 4 μm, b 7 μm, c 14 μm, d 16 μm.

Mentions: Figure 2 shows the side view SEM image of four kinds of CNT arrays grown at different growth times. The obvious difference among the four kinds of arrays is the CNT height. The CNT heights of four kinds of arrays are 4, 7, 14 and 16 μm, respectively. The CNTs of the four samples are oriented in a perpendicular fashion and arrange very close with a high density. Besides the heights of the four CNT arrays are different, the CNTs of the four samples have different orientations to the substrates. Most CNTs of the 4-μm height sample are flexural and not perpendicular to the substrate. There are many very long CNTs extruding from the array surface, and the CNTs of the sample are randomly ordered. The CNT arrays of Figure 2a have the shortest growth time among the four kinds of arrays. During the short growth process, the growth temperature rising and falling rapidly and the CNTs have different growth velocity. A lot of CNTs grow at unstable high velocity during the short grown process, but most grown slowly and uniformly. Therefore, there are a lot of long CNTs appeared in the Figure 2a, and the arrays lose the uniformity. If the growth time is long enough, the growth of arrays would reaches a steady state and the arrays would grow very uniform. The CNT arrays of the 7-μm height sample arranges more orderly than that of the 4-μm height sample. A few nanotubes of the 7-μm height sample are flexural at the root. The distributions of the CNTs become regular with the height of the CNT arrays increasing. The CNTs of the 14- and 16-μm height samples are more uniform than that of the 4- and 7-μm height samples. The CNTs have uniform diameters and heights, and they are aligned regularly one by one. CNT arrays with four different heights in the range of 4–16 μm have been fabricated. The nanotubes of the four kinds of arrays have different CNT heights and similar CNT densities. Therefore, the four samples have different ratios of CNT height to CNT-to-CNT distance. The intertube distance is about 130~150 nm, and the ratios of CNT height to CNT-to-CNT distance of four kinds of arrays are 31, 54, 108 and 123, respectively. As the growth times increase, the heights of the CNT arrays increase and the ratios of CNT height to CNT-to-CNT distance increase simultaneously.


Investigation on the Plasma-Induced Emission Properties of Large Area Carbon Nanotube Array Cathodes with Different Morphologies
The side view FESEM images of four kinds of arrays with different CNT heights: a 4 μm, b 7 μm, c 14 μm, d 16 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211494&req=5

Figure 2: The side view FESEM images of four kinds of arrays with different CNT heights: a 4 μm, b 7 μm, c 14 μm, d 16 μm.
Mentions: Figure 2 shows the side view SEM image of four kinds of CNT arrays grown at different growth times. The obvious difference among the four kinds of arrays is the CNT height. The CNT heights of four kinds of arrays are 4, 7, 14 and 16 μm, respectively. The CNTs of the four samples are oriented in a perpendicular fashion and arrange very close with a high density. Besides the heights of the four CNT arrays are different, the CNTs of the four samples have different orientations to the substrates. Most CNTs of the 4-μm height sample are flexural and not perpendicular to the substrate. There are many very long CNTs extruding from the array surface, and the CNTs of the sample are randomly ordered. The CNT arrays of Figure 2a have the shortest growth time among the four kinds of arrays. During the short growth process, the growth temperature rising and falling rapidly and the CNTs have different growth velocity. A lot of CNTs grow at unstable high velocity during the short grown process, but most grown slowly and uniformly. Therefore, there are a lot of long CNTs appeared in the Figure 2a, and the arrays lose the uniformity. If the growth time is long enough, the growth of arrays would reaches a steady state and the arrays would grow very uniform. The CNT arrays of the 7-μm height sample arranges more orderly than that of the 4-μm height sample. A few nanotubes of the 7-μm height sample are flexural at the root. The distributions of the CNTs become regular with the height of the CNT arrays increasing. The CNTs of the 14- and 16-μm height samples are more uniform than that of the 4- and 7-μm height samples. The CNTs have uniform diameters and heights, and they are aligned regularly one by one. CNT arrays with four different heights in the range of 4–16 μm have been fabricated. The nanotubes of the four kinds of arrays have different CNT heights and similar CNT densities. Therefore, the four samples have different ratios of CNT height to CNT-to-CNT distance. The intertube distance is about 130~150 nm, and the ratios of CNT height to CNT-to-CNT distance of four kinds of arrays are 31, 54, 108 and 123, respectively. As the growth times increase, the heights of the CNT arrays increase and the ratios of CNT height to CNT-to-CNT distance increase simultaneously.

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Large area well-aligned carbon nanotube (CNT) arrays with different morphologies were synthesized by using a chemical vapor deposition. The plasma-induced emission properties of CNT array cathodes with different morphologies were investigated. The ratio of CNT height to CNT-to-CNT distance has considerable effects on their plasma-induced emission properties. As the ratio increases, emission currents of CNT array cathodes decrease due to screening effects. Under the pulse electric field of about 6 V/μm, high-intensity electron beams of 170–180 A/cm2 were emitted from the surface plasma. The production mechanism of the high-intensity electron beams emitted from the CNT arrays was plasma-induced emission. Moreover, the distribution of the electron beams was in situ characterized by the light emission from the surface plasma.

No MeSH data available.