Field emission properties of carbon nitride synthesized by microwave plasma chemical vapor deposition

Crystalline carbon nitride is expected to be an emitter with a long lifetime and high emission stability, because it is composed of carbon and nitrogen with high oxidation resistance and its sharp shape facilitates the occurrence of electron emission. The purpose of this paper is to clarify the field emission properties of crystalline carbon nitride. We studied the improvements in the field emission properties of carbon nitride after surface treatments. The carbon nitride was synthesized using microwave plasma chemical vapor deposition from a CH4-N2 gas system. Si substrates with different electrical properties (p- and n-type of 0.01 and 1500 Ω, respectively) were used. The carbon nitride on the 0.01 Ω n-type substrate showed the highest current density of approximately 0.25 mA/cm2. The maximum current densities of the carbon nitride on the n-type or p-type substrates were higher than those of the undoped type by decreasing the resistivity of the substrate. The threshold field (emission current observed in the minimum electric field) of the carbon nitride on n-type substrates was decreased by decreasing the substrate resistance. In the case of Au-coated deposits on an n-type Si substrate of 0.01 Ω, a threshold field was observed at approximately 1 V/μm. In addition, the electric field emission current density at 20 V/μm was 0.83 mA/cm2. The ultra-thin coatings of Au on the carbon nitride were effective in decreasing the threshold field and increasing the maximum current density. The Fowler-Nordheim plots of the carbon nitride with or without Au coatings formed a straight line, indicating that the Fowler-Nordheim theory perfectly fit the field emission behaviors of samples.