Effect of nitrogen plasma treatment on the hydrophilicity of polycrystalline diamond films with micron-scale grains

Diamond film with micron-scale grains was prepared on silicon substrate by microwave plasma chemical vapor deposition (MPCVD) system. Then, MPCVD equipment was still used to change the experimental conditions, and only nitrogen was used as the gas source, so as to conduct nitrogen plasma treatment on the deposited diamond film. The effects of different treatment time on the structure, morphology and hydrophilicity of diamond films were investigated under the same nitrogen plasma treatment conditions. The results showed that with the increase of nitrogen plasma treatment time, the surface defect density of diamond grains becomes higher and higher, the concentration of nitrogen and sp(2)C=C composition gradually increase, the hydrophilicity of the corresponding diamond film and deionized water becomes better first (the contact angle between deionized water and diamond film decreases from 97 degrees to 44 degrees), and then, it becomes slightly worse (the contact angle between deionized water and diamond film increases from 44 degrees to 49 degrees). It shows that nitrogen plasma treatment can effectively improve the hydrophilicity of diamond film, and the experimental results are explained reasonably.