Of Sicn Thin Films And Its Optical Parameters

Silicon carbon nitride (SiCN) is a new wide band-gap semiconductor with excellent optical properties. It has bright prospect in the field of optoelectronic devices. The optical band gap of SiCN films can be tuned in the range of 2.86eV to 5.0eV with different ratio of Si, C, and N elements. This greatly benefits the application of SiCN films in the fields of light emitting diode(LED) and light semiconductor laser and so on. In the preparation of SiCN film, the different ratio of Si, C, and N elements can generate the band-gap in the range (2.86-5.0 eV) continuously in order to get the adjustable thin film, and a wide range of light-emitting capability can be achieved.In this thesis, the SiCN thin films were prepared on the silicon and quartz substrates by the hot-filament chemical vapor deposition (HFCVD). The effect of the process parameters such as the flow of SiH4/CH4/N2, the temperature of the substrate and the chamber pressure on the performance of the SiCN thin films was investigated. The optimized parameters are as follows:the temperature of the tungsten filament is 2000℃, the temperature of the substrate is 950℃, the distance between the tungsten filament and the substrate is 9mm, the flow rate of the SiH4/CH4/N2 is 1 SCCM,2 SCCM and 6 SCCM and the reaction chamber pressure is 6.5×102 Pa. The prepared samples were characterized by the x-ray diffraction XRD, scanning electron microscopy SEM, atomic force microscopy AFM, Fourier transform infrared spectroscopy FT-IR and the energy dispersive spectrometer EDS. The effect of crystalline phase, microstructure, surface bond and the composition on the optical properties of SiCN films were also explored.Moreover, the optical properties of the prepared SiCN films were characterized by the NKD-8000e thin film analyzer. The transmittance T, reflectance R, the refractive index n, the extinction coefficient k and the thickness of the films were measured to investigate the influence of the parameter on the optical properties of the prepared samples. The results indicated that the refractive index n of the SiCN films reduced with the increasing or deceasing of the flow of the N2. Meanwhile, with the increasing of the wavelength, the refractive index n of the SiCN films decreased.The extinction coefficient k was large in the wavelength range of 350nm to 400nm, indicating that a strong absorption existed in the violet light for the SiCN films. However, the absorption decreased in the visible range and particularly, the optical absorption droped to a low state in the wavelength range of 600nm to 2000nm, suggesting that the SiCN films has weak absorption in this wavelength.