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Laser crystallization of amorphous Si thin films is one of reliable method of preparing nanocrystalline silicon with high density and controllable size. In the present work, molecular dynamics simulation based on Tersoff potential was used to study the laser crystallization process of ultrathin amorphous silicon film (2.7 nm) on amorphous silicon nitride substrate. The influence of laser fluences on the crystallization and formation of nanocrystalline Si was investigated. It was found that there exists a laser fluence window in which nucleation and growth of nanocrystalline Si can be realized, which is in agreement with our previous experimental observations. The nucleation and growth processes in microscopic scale were simulated and the size of formed nanocrystalline Si was limited in both vertical and lateral directions by the film thickness and the formation of grain boundaries.

Based on the general form of Fresnel diffraction,light intensity distribution in laser interference crystallization with a phase shifting grating mask (PSGM) was calculated.Two-dimensional (2D) periodic nanocrystalline silicon (nc-Si) array was fabricated by laser interference crystallization combined with 2D-PSGM.The light intensity irradiated on the surface of a-Si:H samples can be modulated by the PSGM with the periodicity of 400 nm.Experimental results demonstrate that the periodicity of 2D nc-Si array is the same as that of the PSGM,the crystalline regions of nc-Si array are consistant with the simulated results.

SiN-based multilayers were prepared in a plasma enhanced chemical vapor deposition system followed by subsequently thermal annealing and laser irradiation with the aim of fabrication three-dimensional constrained, size-controlled and well-regulated Si nanocrystals. The experimental results show that Si nanocrystals grow in the Si-rich SiN sublayer. Furthermore, the grain size can be controlled according to the thick of Si-rich SiN. It is also found that the crystalline fraction of the multilayers irradiated by laser is significantly higher than that by thermal annealing. The devices that employing the laser-irradiated multilayer as luminescent active layer exhibit an enhanced visible electroluminescence and the external quantum efficiency is improved by 40% in comparison with the device without annealing.

SiN-based multilayer light-emitting devices, which employed Si-rich SiNx/N-rich SiNy multilayer as luminescence active layer, were fabricated by plasma enhanced chemical vapor deposition （PECVD）. Strong visible electroluminescence （EL） from the devices was observed at room temperature. By adjusting the Si/N ratio of the barrier layer, the effect of barrier on the electroluminescence properties was further investigated. The experimental results show that the performance of the devices can be significantly improved by controlling the Si/N ratio of the barrier layer.