Preparation of nano-structure amorphous carbon film and its field emission properties

Nano-structure amorphous carbons films were fabricated on n-Si(111) substrates coated with titanium by microwave plasma chemical vapor deposition (MPCVD) system. The source gas was a mixture of H₂ and CH₄ with the flow rates of 100 sccm and 16 sccm, respectively. During the deposition, the total pressure of 6.0 KPa, substrates temperature of 830°C and microwave power of 1700W which were kept for 4 hours. The surface morphology and the nano-structure of the films were tested by field emission scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman scattering spectroscopy and X-ray photoelectron spectroscopy (XPS). The results show that the film consists of carbon grain size of no more than 100 nm and the main component was amorphous carbon with the mixture of sp² and sp³ bond. Field emission of as-deposited film was then measured at a vacuum of below 5×10^-5Pa. It was found that the initial turn-on field was very low, which was about 0.6 V/μm; the current density of 2.5mA/cm² was obtained under an electric field of 3.7 V/μm. The emission sites density was estimated to be more than 10⁴/cm² at electric field of 3.7V/μm. All these characteristics indicate that such deposited nano-structure amorphous carbon film is an efficient cold cathode material.