研究目的
To study the elastic and inelastic light scattering by silicon nanocrystals (Si-nc) embedded in an amorphous silicon nitride matrix and to determine the structural characteristics of Si-ncs from the effect of light scattering.
研究成果
The study concludes that the elastic scattering (Rayleigh scattering) affects the photoluminescence in terms of peaks broadening, while the inelastic scattering (Raman scattering) contributes to the shift of the PL peak. A novel method using the Lennard-Jones potential was developed for estimating the bond length of both the Si-nc core and surface. The Raman red shift from Si-ncs is attributed mostly to the surface effect, likely due to the decrease of the coordinated number of nanocrystals surface atoms.
研究不足
The Lennard Jones potential is incapable to describe carefully the pair and triplet potential of the tetrahedral structure of silicon, indicating the need for a more detailed model to describe the Si-nc bond length.
1：Experimental Design and Method Selection:
The study involves the use of reflectance combined with photoluminescence (PL) and Raman spectroscopy to probe the scattering light. A model is proposed to calculate the bond lengths of both the Si-nc core and interface.
2：Sample Selection and Data Sources:
An amorphous silicon nitride matrix containing Si-ncs was deposited on (1 1 1) oxidized silicon substrate using the low pressure chemical vapor deposition technique from a mixture of disilane and ammonia. The film stoichiometry was determined using ellipsometry.
3：List of Experimental Equipment and Materials:
The study uses a conventional furnace for annealing, ellipsometry for film stoichiometry determination, and spectroscopy tools for light scattering analysis.
4：Experimental Procedures and Operational Workflow:
The film was annealed at a temperature of 1050°C for 1 hour under nitrogen (N2) environment. The Si-ncs size distribution was calculated from Raman distribution.
5：Data Analysis Methods:
The reflectance spectrum was measured for the visible range between 394 and 686 nm. The PL peaks positions were compared theoretically and experimentally after Raman shift.
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