Nano-crystalline CN_x Films and Field Electron Emission Properties

CN_x films with x ≈ 0.5 were prepared onto a titanium coated ceramic substrate by using microwave plasma enhanced chemical vapor deposition. As-deposited films were studied by x-ray photoelectron spectroscopy (XPS), x-ray diffraction, and scanning electron microscopy. The films consist of nano-crystalline grains with sites in a range of 20-40nm approximately. The interplanar distance (d-value) of the nano-crystalline structure determined from the peak position of x-ray diffraction was found to be 0.336 nm. This value is consistent with the d-value of graphite. XPS measurements of the N 1 s and C 1 s core levels for the same sample demonstrate two types of bonding structures between carbon and nitrogen atoms, corresponding to sp² C-N and sp³ C-N. It is suggested that the N atoms mainly exist in aromatic rings of the nano-graphite layers by substituting carbon positions with nitrogen. Field electron emission characteristics of the film were tested. The turn-on field of the emission was as low as 1.1V/μm.