Interface structure of silicon and diamond film

Diamond films produced by the CVD method have recently attracted great interest in the field of new material studies. In this paper, the interface structure between a single crystalline Si substrate and a diamond film which was deposited by EACVD on a pretreated Si wafer is studied by the method of XPS surface analysis and Laser Raman spectroscopy. In order to expose the interface, the diamond film can be gradually etched away by Ar ions. Based on the feature that different scattering angles of photoelectrons correspond to different detecting depths, the spectra with different scattering angles of 75, 45, 30° are acquired. In the 75° spectrum, the Si-2p peaks of SiO2 and Si appear at 103.4 and 99.4 eV, respectively. In the 45° spectrum, we found the Si-2p peak of Si decreasing, but an apparent rise appeared in 103-100 eV. This indicates a new structure has been generated. In the 30° spectrum, because the detecting depth comes to surface, the Si-2p peak of Si disappears, but a new peak at about 101.2 eV is found obviously. This indicates that the mixed structure of SiOx and SiCx (x < 2) is generated. The Si wafers on which no diamond film deposited are also analysed, only the Si-2p peak of SiO2 and Si can be found in the spectra. The Laser Raman spectra with different film thickness (d < 1 μm, 1 μm < d < 10 μm, d > 10 μm) are still analysed. For the thick films, the diamond structure peak at 1333 cm-1 is obviously large, but the peak of diamond-like, etc. at about 1550 cm-1 is fairly weak. For the thin films, the diamond peak is quite weak, but the peak in the vicinity of 1550 cm-1 becomes wider and larger. This indicates the nondiamond carbon structure appearing. Therefore, we can reach a conclusion that a transition layer between the Si and film is generated in the growth process of diamond film. The first is a SiO2 layer produced on the pretreated Si substrate. The second is diamond-like and noncrystalline carbon structure layer. And the third is a diamond structure layer. Between SiO2 and C, there is a process of O-Si unsaturated bonds and gradually forming C-Si bonds. This transition layer is very important for diamond film deposition.