Field emission characteristics of mixture films of nano-structure amorphous graphite and carbon nanotubes

The mixture film of nano-structure graphite and carbon nanotubes was fabricated on titanium coated ceramic substrate by microwave plasma chemical vapor deposition system (MPCVD). The source gas was a mixture of H₂ and CH₄ with flow rates of 100 sccm and 12 sccm, respectively. During the deposition, the total pressure of 6.0 KPa, substrate temperature of 850°C and microwave power of 1500W were kept for 2 hours. The surface morphology and the nano-structure of the film were examined using field emission scanning electron microscopy, X-ray diffraction, Raman scattering spectroscopy and X-ray photoelectron spectroscopy. Field emission of the film were carried out in a vacuum chamber with base pressure of below 5×10^-5Pa. The initial turn-on field was 0.6V/μm and 1.7 mA/cm² of current density at 1.7 V/μm was obtained. The stability of the emission was tested by maintaining the electric field at 1.8 V/μm. The experiments indicate that the film is an efficient and stable cathode material at low electric field.