The Preparation And Its Performance Of Graphene And Carbon Nanotube Film FED Cathode

In carbon materials, carbon nanotubes, graphene cathode material is considered the most promising field emission. Carbon nanotubes, become a potential ideal field emission cold cathode materials, with its high strength, good electric conductivity, strong chemical stability and low saturation vapor pressure. Graphene is a two-dimensional crystal, it composed of single-layer hexagonal original cell honeycomb, It can go beyond many material of high conductivity and electron transport rate, so that the presence of graphene launch device has a certain application prospect. The carbon nanotubes, graphene is made of transparent film is an ideal material to instead of indium tin oxide (ITO) conductive films, So they can completely replace cathode ray tube display whiche volume and weight are extremely huge, more important is that it is expected to be widely used in completely transparent and flexible field electron emitter.This paper presents the cold cathode field emission materials selection criterion, screening out of carbon nanotubes and graphene as a field emission materials, and summarized the research progress of carbon nanotubes and graphene in the field.Respectively by chemical vapor deposition method of multi-walled carbon nanotubes as well as the REDOX of graphene as a raw material prepared by the preparation of dispersion, with simple vacuum suction filter of the complete structure, uniform thickness, larger area, different film thickness measurement of carbon nanotube film and graphene films. Dispersion concentration and film thickness are related, When the concentration of dispersed carbon nanotubes is0.5mg/mL,1mg/mL,1.5mg/mL, the film thickness are respectively214.37nm,409.53nm,998.26nm.When the concentration of dispersed graphene is0.05mg/mL,0.10mg/mL,0.15mg/mL, the film thickness are respectively23.41nm,38.65nm,96.71nm.Using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM), On surface morphology and structure of film-making carried out extensive characterization. Found that carbon nanotube film is carbon tubes parallel to the basal, mixed and disorderly arrangement, structure, density and thickness of thin film structure. Graphene thin film surface evenly, and smooth. Graphene film’s surface smoothness and density are better than the carbon nanotube film.After described tests the film conductivity and transmittance found:The carbon nanotube film thickness from214.37nm to998.26nm, the transmittance decreased from63%to44%, the square resistance value from37896to9005Ω/sq Ω/sq, electrical conductivity from26.36S/cm to119.4S/cm. Graphene film thickness from23.41nm to96.71nm, the transmittance decreased from82%to66%, square resistance value from6875/sq to2825/sq, the conductivity from69.03S/cm to168.44S/cm.It is found that with the increase of film thickness, transmittance decreased, while the conductivity increased, and graphene conductivity and transmittance are slightly better than the carbon nanotubes.Using the scratch tester analyses the membrane-based adhesion. Found that carbon nanotube film thickness by214.37nm998.26nm, the film of the value of critical load Lc dropped to3.9from10.4N. The thickness of the graphene films by23.41nm and96.71nm, the values of critical load Lc film dropped from14.7N to6.3N. Know that, with increasing film thickness, adhesion strength decreases. Adhesion strength of graphene film is better than carbon nanotube filmRespectively tests and analysis with different thickness and material of the thin film field emission performance. With the increase of film thickness, the carbon nanotube film field enhancement factor were3.992,1.429,7.613, and the work function is respectively0.10057,0.02468,0.13915, open voltage of5.2V,4.5V,3.8V.The field enhancement factor and the film surface has great relationship. The carbon nanotube film with large length diameter ratio, with the film thickness increase, the surface increased, this makes the field enhancement factor value is increased, so that the open voltage decreased. But the bump does not bring stability and lasting emission current density.The preparation of carbon nanotubes film too thick, the film surface will produce the non-uniform conditions such as reunion, However, the preparation of thin film was too thin, although it can enhance the field emission performance, but the film easily broken, and will not be able to combine with basal good.Graphene film field enhancement factor were109.336,76.3243,9.20308. The work function values were0.00295eV,0.00069eV,0.00001eV.The thinner the graphene film is, the bigger the field enhancement factor, and the work function is very small. Emission is stability.Through the comparison of the two sets of data, some data can not be obvious linear relationship.there are very big relations with not perfect of F-N theory.