Field emission from carbon nanotubes on a graphitized carbon fabric R.B. Rakhi a,b , K. Sethupathi b , S. Ramaprabhu a, * a Alternative Energy Technology Laboratory, Department of Physics, Indian Institute of Technology Madras, Chennai 600 036, India b Low Temperature Laboratory, Department of Physics, Indian Institute of Technology Madras, Chennai 600 036, India ARTICLE INFO Article history: Received 22 December 2007 Accepted 10 July 2008 Available online 30 July 2008 ABSTRACT Multi-walled carbon nanotubes (MWCNTs) have been directly grown over a flexible graph- itized carbon fabric by water assisted chemical vapor deposition. Field emission properties are compared with randomly oriented multi-walled and single walled carbon nanotube field emitters obtained by spin coating on to carbon fabric. The MWCNTs and single walled carbon nanotubes (SWCNTs) used in spin coating were characterized by X-ray diffraction (XRD) and Raman spectroscopy. High resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM) were used to characterize the field emitters. The use of graphitized carbon fabric as substrate has brought in flexibility in the fabrication of carbon nanotube field emitters. The samples show good field emission properties with a fairly stable emission current. Analysis of field emission based on the Fowler–Nordheim theory reveals current saturation effects at high applied fields for all the samples. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction Ever since their discovery, carbon nanotubes (CNTs) have at- tracted considerable research interest owing to their excep- tional electronic and mechanical properties [1,2]. Electron field emission from CNTs has been demonstrated as the most promising among the various suggested applications of CNTs. Due to their natural geometry with high aspect ratio, chemi- cal stability, high mechanical strength, high electrical con- ductivity and the possibility of large scale production, both vertically aligned and randomly oriented CNTs have been re- ported as excellent emitters at low operating voltages [3–5].A film of single walled carbon nanotubes (SWCNTs) produced by arc discharge under static He yields a current density of 10 mA/cm 2 at 4.4 V/lm but shows a significant degradation with time [6]. High emission stability has been shown by mul- ti walled carbon nanotubes (MWCNTs), however, a small field enhancement factor has resulted in low emission current [7]. The lack of a suitable stable film fabrication process over a suitable flexible substrate has limited the realization of CNT based vacuum microelectronic devices. CNT field emitters on flexible substrates are very much useful in foldable display devices as the source of electrons or as addressing electrodes [8]. Weak adhesion of CNTs to the substrate often leads to a catastrophic vacuum breakdown or arcing during device oper- ation [9]. Moreover, the electronic resistance between the CNTs and substrate results in joule heating of the interface, thereby damaging the interface and resulting in an increase in the voltage required for emission over extended periods [10–13]. In order to overcome such undesirable effects, we have grown CNTs over a graphitized carbon fabric which offers excellent flexibility and opens several new possibilities for field emission devices. The graphitized carbon fabric is a double layer structured gas diffusion layer porous carbon fabric which consists of macroporous layer of carbon fiber fabric (Bellard, USA) and a microporous layer of carbon black powder and a hydrophobic agent. The carbon black powder 0008-6223/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.carbon.2008.07.024 * Corresponding author: Fax: +91 44 22570509. E-mail address: ramp@iitm.ac.in (S. Ramaprabhu). CARBON 46 (2008) 1656 – 1663 available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/carbon