“…There are several materials used for field electron emission but the most promising one is carbon nanotubes (CNTs) (Forbes, 2012;Forbes et al, 2015). CNTs are composed of graphite sheets rolled into seamless hollow cylinders with diameter ranging from (1 nm) to about (50 nm) (Saito & Uemura, 2000), CNTs discovered by lijima (1991) and it have been attached much attention as electron source for many reasons such as ultra-small radius, high aspect ratio, high electrical conductivity (Zhang et al, 2005), high chemical stability and high mechanical strength (Bani Ali & Mousa, 2016), CNTs offer several advantages over other emitters material such as enhanced current stability, low threshold voltage, long lifetime (Hong et al, 2009) and high emission current density. These emission characterizations are directly related to the unique structure and chemical bonding of the CNTs (Cheng & Zhou, 2003).…”