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CNx films with x ≈ 0.5 were prepared on to a titanium coated ceramic substrate by using microwave plasma enhanced chemical vapour 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 0.336nm. This value is consistent with the d-value of graphite. XPS measurements of the N1 s and C1 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 tu-on field of the emission was as Iow as 1.1 V/μm.