Abstract: Nano Diamond(NCD) has a wide range of applications in precise instruments and optical vacuum windows filed.Microwave plasma chemical vapor deposition(MPCVD) was used to synthesize NCD thin films using CH3CH2OH, Ar and H2 as gas resource.The effect of argon concentration on the films optical properties were studied, The structure,component and property of NCD thin films deposited under different Ar concentrations were investigated by scanning electron microscopy(SEM), Raman spectroscopy, X-ray diffraction(XRD)and infrared spectroscopy(FTIR).The result shows that, with the increasing of Ar concentration, surface roughness and the diamond phase purity decreases, the optical transmittance increases first and then decreases.

Key words: Nano Diamond(NCD) has a wide range of applications in precise instruments and optical vacuum windows filed.Microwave plasma chemical vapor deposition(MPCVD) was used to synthesize NCD thin films using CH3CH2OH, Ar and H2 as gas resource.The effect of argon concentration on the films optical properties were studied, The structure,component and property of NCD thin films deposited under different Ar concentrations were investigated by scanning electron microscopy(SEM), Raman spectroscopy, X-ray diffraction(XRD)and infrared spectroscopy(FTIR).The result shows that, with the increasing of Ar concentration, surface roughness and the diamond phase purity decreases, the optical transmittance increases first and then decreases.