Electronic property of intrinsic point defect system on β–Si3N4 (0001) surface.

The intrinsic point defect influence data for β –Si3N4 by far are incomplete and experimental clarification is not easy. In this contribution, the effects of vacancy ( V 2c , V 6h and V Si ) and interstitial ( I N and I Si ) defects on the electronic properties of H-passivated β –Si3N4 (0001) surface are explored based on density functional theory (DFT) calculation. The results show that it is easier to form N 6h vacancy defects in the surface layer under Si-rich conditions. The existence of N vacancies makes the bottom of conduction bands shift downwards, and the top of valance band is away from Fermi level. The presence of V Si makes the system have the characteristics of p-type semiconductor, and the closer to the inner layer, the narrower the range of additional energy bands and the greater the degree of localization of electrons. The closer the Si atom vacancy is to the surface, the smaller the photon energy corresponding to the maximum absorption coefficient is. Compared with the N vacancy system, the Si vacancy system has higher reflection ability in the low energy region. For the interstitial defect systems, I N is easy to form on the surface layer, and I Si is easy to produce in the inner layer. The I N system has a new additional energy level at the Fermi level, and as the I N is closer to the inner layer, the energy range of the additional energy level is also narrower. In the I Si system, the new additional energy levels appear at the Fermi level and the intermediate band. The results have positive significance for the design of this advanced structural and functional integrated ceramics. The absorption coefficient and reflection coefficient of I Si - 3 system are much higher than those of other systems when the energy is greater than 2.5 eV. [ABSTRACT FROM AUTHOR]