Selective and Non-selective Synthesis of Carbon Nanotubes (CNTs) by Chemical Vapor Deposition (CVD) Characterization: Catalysts and Underlayers Effects on Field Emission Properties
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Since the discovery of carbon nanotubes (CNTs), they have been attracted much attention with abundant potential applications based on their outstanding properties. CNTs are well-known for their superior mechanical strength and low weight, excellent heat conductance, and varying electronic properties depending on their helicity and diameter. In particular, the recent research studies have reported that CNTs have excellent electrical ﬁeld emission properties, with high emission currents at low electric ﬁeld strength due to the high aspect ratio (small diameter and relatively long length). As a result, CNTs are considered as one of the promising materials as cold-cathode ﬁeld emission sources, especially for application requiring high-current densities and lightweight packaging. In this research work, the selective and non-selective multi-wall CNTs (MWCNTs) are grown by using chemical vapor deposition (CVD) technique. Then, their ﬁeld emission properties are examined in a high pressure vacuum chamber of around 10 −7 to 10−6 Torr. MWCNTs are grown onto various underlying layers such as SiO 2 ,Ti ,and W-coated silicon substrates. Thermal CVD furnace containing gas mixtures of acetylene and argon is used to grow CNTs. The growth conditions such as catalyst types and thickness, gas ﬂow rate and deposition temperature are discussed. Eﬀects of diﬀerent catalysts with various underlayers on the ﬁeld emission properties of CNTs are studied and results are presented. The measurement results indicate that CNTs have signiﬁcant ﬁeld emission capabilities to be used as cold cathode materials.