Photoluminescence Properties And Structure Design Of Nano SiC Thin Films

Nanocrystalline silicon carbide （nc-SiC） thin films have been deposited by the helicon wave plasma-enhanced chemical vapor deposition （HWP-CVD） technique on single crystal silicon and corning glass substrates from SiH₄, CH₄ and H₂.reactant A variety of techniques, including Fourier transform infrared spectroscopy, X-ray diffraction, ultraviolet-visible transmittance and reflection spectroscopy, scan electron microscopy, atomic force microscopy, transmittance electron micrograph and photoluminescence （PL） are utilized to analyze the crystalline fraction, bonding configurations, morphology, optical gap and the PL property of the films. The effects of the experiment parameters such as coupling radio frequency （rf） power and hydrogen flow rates on the structural and optical characteristics of the films are studied. A multilayer nc-SiC film was designed according to the preparation conditions for amorphous and nc-SiC. Furthermore, the relation between the microstructure and photoluminescence property was investigated as well.It has been shown that nc-SiC thin films were achieved through modulating the rf power. Amorphous SiC films were deposited at lower rf power, while nanocrystalline 3C-SiC films was obtained after the rf power increasing to a higher value. A strong room temperature PL visible to the naked eyes is observed for nc-SiC thin films. On the basis of the film microstructure characterization, the observed distribution of PL peak energy is mainly attributed to the radiation originated from nanocrystallites with different size, while that of PL peak shift is interpreted as a reflection of the size distribution of nanocrystallites and degree of structure disorder. The modification of the energy band characteristics for nc-SiC films have been performed through changing the hydrogen flow rates. The obtained PL tuned from green to blue-purple is attributed to the adjusting of the energy band gap of the films. Multilayer SiC nanocrystallites interbedded in amorphous SiC potential barrier has been designed. The interfaces alternated periodically between nanometer scale amorphous and crystalline layers through the observation of scanning electron microscope. The red shift of PL peak energy with the increase of excitation wavelength indicates that the quantum confinement effect dominates the luminescent process of the film.