Nickel-induced transformation of diamond into graphite and carbon nanotubes and the electron field emission properties of resulting composite films

Highlights: • Transformation of diamond into graphite and CNTs was achieved with Ni as catalyst. • Offering new information concerning the nature of the CNTs-nickel-diamond interface. • Both the catalytic etching and growth mechanism were investigated. • Effects of methane concentration on the catalytic process were systematically studied. • EFE properties of diamond-based composite films were studied. The metal-induced transformation of diamond into graphite and carbon nanotubes (CNTs) was achieved by catalytic deposition with nickel as the catalyst. The quality of catalytic products was assessed by scanning electron microscopy, Raman spectroscopy and transmission electron microscopy. Results showed that the catalytic process could be controlled by adjusting the carbonaceous concentration in the deposition atmosphere, and new information concerning the diamond/Ni/graphite multi-phase mixed interface between diamond and carbon nanotube has been analyzed. A model was put forward to elucidate the mechanism of catalytic etching and growth on the diamond surface. In addition, the resulting diamond/CNTs composite film (10% CH₄) was found to exhibit the lowest turn-on field of 6.9 V/μm as well as good current emission stability compared to the other composite films.