We report a significant improvement in electron field emission property of carbon nanotubes film by using an electron cyclotron resonance plasma treatment. Our research results reveal that plasma treatment can modify the surface morphology and enhance the field emission characteristics of carbon nanotubes. Raman spectra indicate that plasma treated CNTs sample has lesser defects. Before plasma treatment, low current density of 6.5？mA/cm2 at 3.0？V/μm and at a high turn-on field of 2.4？V/μm was observed. ECR plasma treated CNTs showed a high current density of 20.0？mA/cm2 at 3.0？V/μm and at a low of 1.6？V/μm. The calculated enhancement factors are 694 and 8721 for ECR-plasma untreated and treated carbon nanotubes, respectively. We found an increase in the enhancement factor and emission current after the ECR-plasma treatment. This may be attributed to creation of geometrical features through the removal of amorphous carbon and catalyst particles. 1. Introduction Carbon nanotubes (CNTs) have great attention because of their unique morphologies, which make their uses in wide variety of applications. The different techniques for the synthesis of CNTs have been developed, such as arc discharge method, laser ablation method, and chemical vapor deposition (CVD) [1–4]. The most widely used method is CVD technique, in which the synthesis is achieved by putting a carbon source in the gas phase. One of the most promising applications of CNTs is in field emission (FE) devices [5–14]. High aspect ratio and atomically sharp radius of apex curvature of the CNTs enhance the local field and lower the threshold field for electron emission. The emission properties of CNTs are governed by the work function, crystalline structure, geometry of their tips, and so forth. In addition, the surrounding gases and impurities on the surface have also been known to strongly affect their FE characteristics. However, the effect of crystallinity of CNTs on the FE has not been much investigated till now. Schwoebel and Spindt [15] experimentally found that low-pressure hydrogen glow discharge can clean the surface contaminants in both microfabricated single molybdenum tips and arrays which resulted in a decrease of ~1？eV in the work function. Yu et al. [16] achieved a low-field electron emission in undoped nanostructure diamond by employing a hydrogen plasma heat treatment. Hydrogen plasma has been known to greatly enhance the field emission property of CNTs [17]. These references indicate that plasma treatment is an effective method to improve the field emission property of CNTs. In this
References
[1]
Z. F. Ren, Z. P. Huang, J. W. Xu et al., “Synthesis of large arrays of well-aligned carbon nanotubes on glass,” Science, vol. 282, no. 5391, pp. 1105–1107, 1998.
[2]
C. J. Lee, D. W. Kim, T. J. Lee, et al., “Synthesis of aligned carbon nanotubes using thermal chemical vapor deposition,” Chemical Physics Letters, vol. 312, no. 5-6, pp. 461–468, 1999.
[3]
W. Z. Li, S. S. Xie, L. X. Qian et al., “Large-scale synthesis of aligned carbon nanotubes,” Science, vol. 274, no. 5293, pp. 1701–1703, 1996.
[4]
S. Fan, M. G. Chapline, N. R. Franklin, T. W. Tombler, A. M. Cassell, and H. Dai, “Self-oriented regular arrays of carbon nanotubes and their field emission properties,” Science, vol. 283, no. 5401, pp. 512–514, 1999.
[5]
G. P. Collins and A. Zettl, “A simple and robust electron beam source from carbon nanotubes,” Applied Physics Letters, vol. 9, no. 13, pp. 1969–1971, 1996.
[6]
E. Milnoux, O. Groening, K. B. K. Teo et al., “Achieving high-current carbon nanotube emitters,” Nano Letters, vol. 5, pp. 2135–2138, 2005.
[7]
X. Zhao, M. Ohkohchi, M. Wang, S. Iijima, T. Ichihashi, and Y. Ando, “Preparation of high-grade carbon nanotubes by hydrogen arc discharge,” Carbon, vol. 35, no. 6, pp. 775–781, 1997.
[8]
X. Xu and R. G. Brandes, “A method for fabricating large-area, patterned, carbon nanotube field emitters,” Applied Physics Letters, vol. 74, no. 17, pp. 2549–2551, 1999.
[9]
D. W. Kang and J. S. Suh, “Fabrication temperature effect of the field emission from closed and open tip carbon nanotube arrays fabricated on anodic aluminum oxide films,” Journal of Applied Physics, vol. 96, no. 9, pp. 5234–5238, 2004.
[10]
S. J. Oh, J. Zhang, Y. Cheng, H. Shimoda, and O. Zhou, “Liquid-phase fabrication of patterned carbon nanotube field emission cathodes,” Applied Physics Letters, vol. 84, no. 19, pp. 3738–3740, 2004.
[11]
K. A. Dean and B. R. Chalamala, “The environmental stability of field emission from single-walled carbon nanotubes,” Applied Physics Letters, vol. 75, no. 19, pp. 3017–3019, 1999.
[12]
J. M. Kim, W. B. Choi, N. S. Lee, and J. E. Jang, “Field emission from carbon nanotubes for displays,” Diamond and Related Materials, vol. 9, no. 3–6, pp. 1184–1189, 2000.
[13]
I. T. Han, H. J. Kim, Y. J. Par et al., “Fabrication and characterization of gated field emitter arrays with self-aligned carbon nanotubes grown by chemical vapor deposition,” Applied Physics Letters, vol. 81, no. 11, pp. 2070–2072, 2002.
[14]
J. Ali, A. Kumar, S. Husain, and M. Husain, “Effect of catalyst-deposition methods on the alignment of carbon nanotubes grown by low pressure chemical vapor deposition,” Nanoscience and Nanotechnology Letters, vol. 3, no. 2, pp. 175–178, 2011.
[15]
P. R. Schwoebel and C. A. Spindt, “Field-emitter array performance enhancement using hydrogen glow discharges,” Applied Physics Letters, vol. 63, no. 1, pp. 33–35, 1993.
[16]
K. Yu, Z. Zhu, M. Xu, Q. Li, and W. Lu, “Electron field emission from soluble carbon nanotube films treated by hydrogen plasma,” Chemical Physics Letters, vol. 373, no. 1-2, pp. 109–114, 2003.
[17]
Y. M. Wong, W. P. Kang, J. L. Davidson, B. K. Choi, and J. H. Huang, “Growth and profile modification of carbon nanotubes designed for field emission applications by hydrogen plasma pretreatment,” Diamond and Related Materials, vol. 15, no. 4–8, pp. 1132–1137, 2006.
[18]
J. Asmussen, “Electron cyclotron resonance microwave discharges for etching and thin‐film deposition,” Journal of Vacuum Science & Technology A, vol. 7, no. 3, p. 883, 1989.
[19]
C. Journet, W. K. Maser, P. Bernier et al., “Large-scale production of single-walled carbon nanotubes by the electric-arc technique,” Nature, vol. 388, no. 6644, pp. 756–758, 1997.
