Study On The Field Emission Current Of Carbon Nanotube Films

Since carbon nanotubes were first discovered in 1991, they have attracted considerable interest amongst scientists worldwide because of their unique excellent physical properties, chemical properties and electronics properties. Carbon nanotubes have been studied extensively as cold cathodes for microelectroics devices, such as field emission display ,field emission lighting ,microwave amplifier, X-Xay tube ,due to their high aspect ratio, small tip radio of curvature, high conductivity ,high-intensity, high toughness, stability and good thermal conductivity.It is an ideal field emission material, and its application for flat panel display is progressing rapidly.In this paper , the microscopic mechanism on field emission of carbon nanotubes films has been discussed; the structure and electrical properties of carbon nanotubes have been analysised .Intermolecular charge transport under external electric field is discussed in systems of conjugated chain interaction of carbon nanotubes . The curve deflection of field emission current characteristics has been explained by the contact between carbon nanotubes with the base material,phase shift and thermal emission.At first, the microscopic mechanism on field emission of carbon nanotubes film has been discussed, include field emission from the tip and the defects. Field emission have been impacted by topological defects and doping defects, which change energy band structure of the carbon nanotubes,increase emission. The modification on surface of carbon nanotubes film can reduce surface work function of carbon nanotubes films or increase the density of states . It can be seen that increasing field emission of the carbon nanotubes film is really to change the work function of carbon nanotubes films or reduce surface barrier. there are many useful methods to lower surface barrier of carbon nanotubes ,such as atomic adsorped, diamond-like carbon films formated and surface atoms doped on the surface.The electrical properties of carbon nanotubes has also been studied by tight-binding approximation method. The results show that, at room temperature, peierls phase change has taken place in carbon nanotubes, the carbon nanotubes have been changed from metal into semiconductor, linked by strong carbon bond between polymers. In this paper, the carrier transport properties of carbon nanotubes , based on the transport properties of polymers ,has been studied . Soliton is the electrical carrier in carbon nanotubes. The carrier transport properties of carbon nanotubes become stronger under electric field ,the conductive conductivity of carbon nanotubes is changed from one-dimensional to two-dimensional, at the same time the charge transport capacity is also enhanced. The increastion of charge transport capacity under electric field has been explained by two-way conducting mechanism.The curve deflection of field emission current on carbon nanotubes has been researched. The results show that,the curve deflection of the field emission current comes form double-barrier including substrate with carbon nanotubes and carbon nanotubes with vacuum. The effect about phase shift under strong electric field and thermal emission on field emission of carbon nanotubes films has been analysised, Electric field and thermal emission are secondary reasons for the curve deflection of field emission current .