Study Of The Microstructure And Properties Of Silicon Films Prepared Via PECVD

Nanocrystalline silicon films consist of silicon nanocrystals, amorphous phase and high density interface. nc-Si films have been considered as a promising material in solar cells, thin film transistors and sensor devices, due to its superior properties compared to the amorphous silicon (a-Si:H) films, such as high electrical conductivity, low Electrical conductivity activation energy, high charge carrier mobility, better stability and higher absorption.In this work, several series of amorphous silicon films with varied medium-range order and defects density were prepared via plasma enhanced chemical vapor deposition. Silane and hydrogen were used as the reaction sources. Nanocrystalline silicon films were prepared through re-crytsllinzation of amorphous silicon films. The re-crystallization methods were solid phase crystallization (SPC), rapid thermal process as well as combination of RTP and SPC. The influence of annealing parameters, the medium-rang order and defects density of amorphous silicon films on the crystallized fraction was studied. The relationship between microstructure and photoelectric properties of nanocrystalline silicon films was studied. The main research findings are summarized as follows:During the preparation of amorphous silicon films via PECVD, with the increase of Hydrogen dilution ratio, the deposition rate and medium-range order of films decreased, while optical band gap and defects density increased. With the increase of deposition temperature, position rate and medium-range order of films increased, while optical band gap and defects density decreased. When nanocrystalline silicon films were prepared, the crystallized fraction of nanocrystalline silicon films increased with the increase of annealing temperature and annealing durations, as well as the enhancement of medium-range order and the decrease of films. When nanocrystalline silicon films were prepared via the combination of SPC and RTP, the RTP pre-annealing induced the improvement of the medium-range order of films and the decrease of incubation duration, leading to the enhancement of crystallization of films. RTP pre-annealing combined with SPC can significantly enhance the recrystallization process when SPC at900℃for0.5h. Nanocrystalline silicon films consist of amorphous silicon phase and silicon nanocrystals. Silicon nanocrystals are randomly embedded in amorphous silicon matrix. The photoelectric properties of nc-Si films are closely related to the microstructure of films. The electrical conductivity of nc-Si film increased with the increase of crystallized fraction. In addition, for the nc-Si films with similar crystal sizes, it was uncovered that the logarithm of conductivity presented a linear relationship with the crystallized fraction. With the increase of crystallized fraction of nc-Si films, the photoabsorption coefficient increased and the optical band gap reduced.