Calculation of the Electronic Structure of SiCN Crystal by LAPW Method

The excellent character and broad potential for application of Silicon Carbon Nitride Film have attracted many researchers in the fields of both condensed matter physics and materials science and engineering, etc. However, most of work concentrates on the preparation of SiCN. Scientists have prepared various SiCN materials, such as SiCN crystal, nanocrystalline, ceramics, etc. Thus we investigate the electronic properties of SiCN crystal using LAPW (linearized Augmented Plane Wave) method in order to give proper interpretation of its characteristic. The LAPW method is among the most accurate methods for performing electronic structure calculations for crystals. It is based on the density functional theory. Because the structure of SiCN crystal is similar to that of __Si3N4, in the course of calculation, we calculate the __Si3N4 firstly, then substitute C atom for Si. We could vary the Si:C:N ratio, and compare the electronic structures in the different ratios of Si:C:N. ( In experiment, the average [N] for the crystalline phase is about 50 at %, only slightly than the theoretical value for the C3N4 or Si3N4. the C:Si ratio varies between 5:1 and 1:1 with a mean value around 2:1). This method is used to investigate the intact crystal. We also use supercells, which include several cells of __Si3N4 (or __C3N4) and substitute a Si (or C) atom in it with a C (or Si) as a defect atom. In this method SiCN is considered as a doped system. We use the GGA (Generalized Gradient Approximation) to do the exchange-correlation potential.