A new chemical path for fabrication of nanocrystalline diamond films

In this work, we report a new process for synthesis of nanocrystalline diamond films by using a small amount of simultaneous O2 and N2 addition into conventional CH4/H2 mixtures. The nanocrystalline diamond samples were grown in a 5 kW microwave plasma assisted chemical vapor deposition system on large silicon wafers of 5.08 cm in diameter. Depending on the amount of O2 and N2 addition, the growth rates were in the range from 2.5 to 3.5 μm/h. The samples were characterized by scanning electron microscopy, X-ray diffraction and micro-Raman spectroscopy. Our work demonstrates that the morphology, microstructure, grain size, crystalline quality and growth rate of nanocrystalline diamond films can be tailored by simply adjusting the amount of O2 and N2 addition, and with increasing the ratio of O2/N2 addition, the crystalline quality of the nanocrystalline diamond films is significantly enhanced, while the average grain size increases only slightly from 31 to 45 nm. This new process offers a simple way to tailor the growth of large-area uniform nanocrystalline diamond films of high growth rates and variable microstructures for different applications of nanocrystalline diamond films.