A new chemical path for fabrication of nanocrystalline diamond films

摘要

In this work, we report a new process for synthesis of nanocrystalline diamond films by using a small amount of simultaneous O_2 and N_2 addition into conventional CH_4/H_2 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 O_2 and N_2 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 O_2 and N_2 addition, and with increasing the ratio of O_2/N_2 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.