Study Of Fabrication And Field Emission Of CNT On Cu Catalyst

Field emission display (FED) is believed as the best flat panel display due to its high brightness, high contrast, low power consumption and fast response time. Carbon nanotubes (CNTs) have been studied extensively in the past decade, and CNTs based FED (c-FED) has attracted considerable attention. Compared with metal and semiconductor microtip field emission sources, CNTs can work in less stringent vacuum conditions and have high aspect ratio, high emission current, good chemical stability and high mechanical strength, thus can be used as promising electron emitters.With various forms of CNTs such as whiskerlike, branched, bidirectional, spiral, and coiled, many kinds of CNT growth methods have been established. Among the various techniques, thermal chemical vapor deposition (CVD) is most popular, especially due to the simplicity and low cost. The physical structures and properties of the CNT are determined by the choice of catalyst which plays a major role. General speaking, transition metals such as Ni, Fe, and Co are chosen to fabricate CNTs. In recent years, some new materials, such as Pb, Cu and Pt, are also can be used as catalyst in the growth of CNTs. In this study, copper is chosen as the catalyst for the growth of CNTs, and various CNTs film are grown on Cu catalyst on glass substrate using CVD method. The main concludes and innovative results are listed as bellow:1) Effects on growth and field emission(FE) properties of CNT using single Cu film as catalyst: Optimization of the CNT cathodes growth on Cu-coated glass substrate using CVD is studied. The morphologies and FE properties of CNT on various Cu catalyst affected by sputtering power and deposition time are systematically studied. The results indicate that diameters and densities of CNT can be controlled by changing the thickness of Cu film and growth temperature. There is an optimal thickness range of Cu film (260-360nm) and growth temperature (650℃) being used as the field emission cathode.2) The influence of Cr film on growth and FE properties of CNTs on various Cu-coated glass: Cr film with thickness of 50-60nm is inserted as a barrier layer to prevent diffusion of Cu film on the glass substrate. With increasing of Cu sputtering power, the diameters and densities of CNTs become bigger and higher, which affects the FE properties. 3) Morphologies and FE properties of CNT on CuCr alloy catalysts: CuCr alloy catalysts are deposited on glass substrates by Radio Frequency (RF) magnetron co-sputtering, and the CNT are grown by CVD. The growth temperature of CNT is at 600-675℃while a dual target magnetron sputtering system was used to control the ratio of the CuCr alloy catalyst by the RF sputtering power. CNT with wirelike and coiled shapes are got by changing some parameters. The results show that FE properties of coiled CNT are better than that of the wirelike CNT due to optimal density and spiral structure.4) Morphologies and FE properties of aligned CNT (ACNT) on Cu catalysts: ACNT are deposited using Cu catalyst on Cr-coated substrate by DC plasma-enhanced CVD (PECVD) at the temperature of 675℃. The thicknesses of Cu films on Cr-coated glass substrates are controlled by deposition time of magnetron sputtering.. The growth morphologies of the ACNTs are investigated by scanning electronmicroscopy and transmission electron microscopy. The different performance ofACNTs on various Cu films is explained by referring to the graphitic order asdetected by Raman spectroscopy. The results indicate that the ACNTs are formedin tip-growth model where Cu is used as a novel catalyst, and the thickness of Cufilms is responsible to the diameter and quality of synthesized CNTs.In sumarry, CNTs of various shapes on Cu catalysts are achieved. The densitiesand diameters of CNT can be controlled by changing thickness and sputtering power ofCu, which can get CNT cathode with high emission capability and high definitiondirectly grown on glass.