Limits...
Field Emission Characteristics of the Structure of Vertically Aligned Carbon Nanotube Bundles.

Lin PH, Sie CL, Chen CA, Chang HC, Shih YT, Chang HY, Su WJ, Lee KY - Nanoscale Res Lett (2015)

Bottom Line: In this study, we performed thermal chemical vapor deposition for growing vertically aligned carbon nanotube (VACNT) bundles for a field emitter and applied photolithography for defining the arrangement pattern to simultaneously compare square and hexagonal arrangements by using two ratios of the interbundle distance to the bundle height (R) of field emitters.The fluorescent images of the synthesized VACNT bundles manifested the uniformity of FE currents.The results of our study indicate the feasibility of applying the VACNT field emitter arrangement to achieve optimal FE performance.

View Article: PubMed Central - PubMed

Affiliation: Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Road, Taipei, 10607, Taiwan, plin21@mail.ntust.edu.tw.

ABSTRACT
In this study, we performed thermal chemical vapor deposition for growing vertically aligned carbon nanotube (VACNT) bundles for a field emitter and applied photolithography for defining the arrangement pattern to simultaneously compare square and hexagonal arrangements by using two ratios of the interbundle distance to the bundle height (R) of field emitters. The hexagon arrangement with R = 2 had the lowest turn-on electric field (E to) and highest enhancement factor, whereas the square arrangement with R = 3 had the most stable field emission (FE) characteristic. The number density can reveal the correlation to the lowest E to and highest enhancement factor more effectively than can the R or L. The fluorescent images of the synthesized VACNT bundles manifested the uniformity of FE currents. The results of our study indicate the feasibility of applying the VACNT field emitter arrangement to achieve optimal FE performance.

No MeSH data available.


Field emission characteristics of samples A, B, C, and D. aJ–E plot and b FN plot
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4504873&req=5

Fig3: Field emission characteristics of samples A, B, C, and D. aJ–E plot and b FN plot

Mentions: Figure 3a presents the J–E curves of the synthesized VACNT bundles. The turn-on electric fields (Eto) corresponding to the current density of 10−2 mA cm−2 [13, 14] for samples A, B, C, and D were approximately 2.0, 2.8, 1.6, and 2.5 V μm−1, respectively. Figure 3b shows the FN plots of the synthesized samples. The β of each sample was calculated as , where , which was derived by the log of the FN equation, , where J is the FE current density (A cm−2), E is the applied electric field (V cm−1), q is the charge (Coulomb), ħ is Planck’s constant divided by 2π, and m is the electron mass. When the Φ of CNT was set at 4.8 eV [15], the enhancement factors (β) of samples A, B, C, and D were 1020, 840, 1770, and 905, respectively. Table 2 shows a summary of the relation among the Eto, β, and number density of VACNT bundle samples. Evidently, Eto decreased as β and the VACNT bundle number density increased. The correlation between the number density and Eto, or the correlation between the number density and β, reveals that the number density is a more favorable indication compared with the ratio of R or L. According to the FE results, the ratio R = 2 produced a relatively higher FE current density than did R = 3. In addition, when the ratio R was fixed, the hexagonal arrangement, at a same applied electric field, exhibited a higher FE current density than did the square arrangement. According to the geometrical arrangement, the hexagonal arrangement had a higher number density than did the square arrangement; this phenomenon was consistent with our results when the amount of emission sites was low (less than 107 cm−2).Fig. 3


Field Emission Characteristics of the Structure of Vertically Aligned Carbon Nanotube Bundles.

Lin PH, Sie CL, Chen CA, Chang HC, Shih YT, Chang HY, Su WJ, Lee KY - Nanoscale Res Lett (2015)

Field emission characteristics of samples A, B, C, and D. aJ–E plot and b FN plot
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4504873&req=5

Fig3: Field emission characteristics of samples A, B, C, and D. aJ–E plot and b FN plot
Mentions: Figure 3a presents the J–E curves of the synthesized VACNT bundles. The turn-on electric fields (Eto) corresponding to the current density of 10−2 mA cm−2 [13, 14] for samples A, B, C, and D were approximately 2.0, 2.8, 1.6, and 2.5 V μm−1, respectively. Figure 3b shows the FN plots of the synthesized samples. The β of each sample was calculated as , where , which was derived by the log of the FN equation, , where J is the FE current density (A cm−2), E is the applied electric field (V cm−1), q is the charge (Coulomb), ħ is Planck’s constant divided by 2π, and m is the electron mass. When the Φ of CNT was set at 4.8 eV [15], the enhancement factors (β) of samples A, B, C, and D were 1020, 840, 1770, and 905, respectively. Table 2 shows a summary of the relation among the Eto, β, and number density of VACNT bundle samples. Evidently, Eto decreased as β and the VACNT bundle number density increased. The correlation between the number density and Eto, or the correlation between the number density and β, reveals that the number density is a more favorable indication compared with the ratio of R or L. According to the FE results, the ratio R = 2 produced a relatively higher FE current density than did R = 3. In addition, when the ratio R was fixed, the hexagonal arrangement, at a same applied electric field, exhibited a higher FE current density than did the square arrangement. According to the geometrical arrangement, the hexagonal arrangement had a higher number density than did the square arrangement; this phenomenon was consistent with our results when the amount of emission sites was low (less than 107 cm−2).Fig. 3

Bottom Line: In this study, we performed thermal chemical vapor deposition for growing vertically aligned carbon nanotube (VACNT) bundles for a field emitter and applied photolithography for defining the arrangement pattern to simultaneously compare square and hexagonal arrangements by using two ratios of the interbundle distance to the bundle height (R) of field emitters.The fluorescent images of the synthesized VACNT bundles manifested the uniformity of FE currents.The results of our study indicate the feasibility of applying the VACNT field emitter arrangement to achieve optimal FE performance.

View Article: PubMed Central - PubMed

Affiliation: Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Road, Taipei, 10607, Taiwan, plin21@mail.ntust.edu.tw.

ABSTRACT
In this study, we performed thermal chemical vapor deposition for growing vertically aligned carbon nanotube (VACNT) bundles for a field emitter and applied photolithography for defining the arrangement pattern to simultaneously compare square and hexagonal arrangements by using two ratios of the interbundle distance to the bundle height (R) of field emitters. The hexagon arrangement with R = 2 had the lowest turn-on electric field (E to) and highest enhancement factor, whereas the square arrangement with R = 3 had the most stable field emission (FE) characteristic. The number density can reveal the correlation to the lowest E to and highest enhancement factor more effectively than can the R or L. The fluorescent images of the synthesized VACNT bundles manifested the uniformity of FE currents. The results of our study indicate the feasibility of applying the VACNT field emitter arrangement to achieve optimal FE performance.

No MeSH data available.