Optical properties of nano-crystalline diamond films

A Nano-crystalline diamond film with a smooth surface and compact and uniform crystal grains was successfully deposited on silicon by HFCVD method. Scanning electron microscopy (SEM), atom force microscopy(AFM), Raman scattering spectra, as well as optical. transmission spectra and spectroscopic ellipsometry were employed to characterize the as-grown films. The calculated values of the optical constants n and k were obtained from the applied EMA model and fitted result. The surface roughness of the film is only 21 rim, while its grain size is no more than 100nm. The optical transmission of the film, whose thickness is 3.28 mu m, is close to 25 percent at the wavelength of 632. 8nm and up to be 50percent at the wavelength of I 100nm. Its band gap is estimated to be 4.3ev by direct optical transition machanics.