Doped With Nitrogen Sic Thin Films And Their Optical Properties

Silicon carbon nitride (SiCN) thin films, as a new ternary element films, exhibit outstanding optical, electrical and mechanical properties. Particularly they are proposed as candidates for luminescent application due to their extraordinary luminescent properties and adjustable band gaps varying from to visible light range. In this dissertation, we grow the silicon carbide (SiC) and SiCN semiconductor films by using the modified hot filament chemical vapor deposition (HFCVD) method and study their optical properties. The main work and results are listed as following.First of all, the modified hot filament chemical vapor deposition (HFCVD) system used in present dissertation is designed and developed.Secondly, based on the crystalline structure of theβ-SiC andβ-Si₃N₄, two kinds of elementary models of the SiCN structure are constructed and investigated by the first-principles calculation of plane wave ultrasoft pseudopotential. The calculated results indicate that the SiCN model based on theβ-Si₃N₄ structure is consistent with the experimental results.And then, SiC films are successfully deposited on silicon, quartz, etc... substrates by HFCVD method with the mixture of silane (SiH₄), methane (CH₄) and hydrogen (H₂) used as reacting gas. The influence of pretreatment and growth technology on the SiC films is studied systematically and the technology is optimized. The deposited samples are highly crystallized 3C-SiC films consisted of compact and orderliness grains. And the atom ratio of Si to C reaches nearly 1:1 and these atoms distribute homogeneous. The FTIR and Raman spectrum confirm that Si-C bond take a dominant position in the deposited 3C-SiC samples. Because of quantum size effect, the band gap of the samples obtained by UV-vis spectroscopy and photo- luminescence (PL) is wider than that of the 3C-SiC bulk structure. Moreover, the field emission properties of the SiC films are explored, and it is found that the field emission properties are related to the surface morphology and structure of the films. At last, SiCN films are successfully grown on substrate(such as silicon, quartz). The effects of technological conditions (nitrogen (N₂) flow rate, CH₄ flow rate, substrate temperature) on quality of SiCN thin films are analyzed and discussed and the growth technology is optimized. The structure, surface morphology, composition and chemical bond of the SiCN films are explored in detail. It reveals that there are some cracks and space in the surface of the prepared films, which means that a new material with undercrystal structure has formed. And the uniform distribution of Si, C, and N elements is observed in the film, altogether with Si-C, Si-N, C-N bonds. The UV-vis spectroscopy indicates that optical band gap of the SiCN films is affected by N₂ flow rate, and the relationship between the band gap and the N content in films is not linear. The film thickness (d,808nm), refraction index (n, 2.34～2.37) and extinction coefficient (k, 0.007～0.012) are measured by nkd-8000.