Investigation Of Nano-SiC Film Photoluminescence And Nanoporous SiO₂:F Film With Low Dielectric Constant

As a promising third generation semiconductor material, silicon carbide (SiC) has a large band gap, high breakdown voltage, high thermal conductivity, high electron saturation velocity, and inert chemical properties. These unique properties make it an attractive material for optoelectronic devices and high-frequency, high-power, high-temperature electronic devices. However, being an indirect energy band gap semiconductor, SiC exhibits only weak blue photoluminescence (PL) peaks at low temperature. Therefore, researchers are eager to seek effective means to improve its luminescent efficiency. In particular, its light emission mechanisms have been studied intensively.In the first part of this study, we prepared SiC granule films and SiC particles embedded in silicon dioxide (SiO₂) nano-composite thin films.1. SiC granule films were fabricated on porous glass substrates by radio frequency (RF) magnetron technology, and the effects on luminescence of substrate etching time, SiC deposition time and the annealing temperature were studied. When the etching time of the glass substrate was 20 min, and the SiC deposition time was 1 h, we obtained the PL with most intensity.2. The silicon carbide/silicon dioxide (SiC/SiO₂) nano-composite thin films were prepared by radio frequency (RF) magnetron circular-sputtering and subsequent high temperature annealing. X-ray diffusion (XRD) analyses showed the process of transformation from the amorphous to the crystalline phase with the increase in the annealing temperature. When annealed the sample at 800 oC, SiO₂ began crystallization. Annealed the sample at 1000 oC, SiC was observed to be crystallization. Photoexcited electrons and holes in the extended states loose their energy and fall into the localized tail state to recombine radiatively, which is responsible for the red emission. The electric measurements for the [SiC/SiO₂]2 nano-composite thin films show that the sample has a relative high resistivity (6.8×106 ?·cm), and its electric behavior mainly happens in the bandtai of the film.In second section of this study, nanoporous SiO₂: F films with ultralow dielectric constants were successfully synthesized by the sol-gel method. The minimum leakage current density is 3×10-6 A/cm2 in the nanoporous SiO₂:F films annealed at 450 oC. The three dimensional networks that make up the high-porosity films were clearly observed in scanning electron microscopy (SEM) micrographs, with films of porosity 80 %. The measured dielectric constants ranged from 2.05 to 2.3 depending on the porous nature of the films. The introduction of the Si-F bond, which reduces the dielectric constant of the film, was observed in Fourier transform infrared spectroscopy (FTIR).