Diamond/microcrystalline graphite composite films were synthesized by thermal catalytic etching method with nickel as the catalyst. The surface morphology and composition of the composite films were examined by scanning electron microscopy (SEM), Raman spectroscopy and X-ray diffraction (XRD). The results show that the etching and graphitizing degree of diamond surface increased with the rising annealing temperature and the surface of as-grown diamonds were replaced by the tips of high aspect ratios and porous foam structure. The electron field emission (EFE) properties of composite films were improved compared to the as-grown diamond. The lowest turn-on field of 9.6 V/mu m has been detected for the composite film annealed at 900 degrees C. The field emission current stability was influenced by graphite phase formed in the etching process. Gradual increase of emission currents along with time were observed for both samples annealed at 700 degrees C and 800 degrees C. However, there was a slightly decrease for the emission current of sample annealed at 900 degrees C. (C) 2016 Elsevier B.V. All rights reserved.