The Study On Preparation And Luminescence Properties Of Semiconductor Nanocrystals Embedded In Different Dielectric Matrices

The Ge nanocrystals embedded in amorphous SiO₂ and high-K dielectric material Lu₂O₃ matrices were fabricated successfully using pulsed laser deposition (PLD) method. The structure and optical properties of the Ge nanocrystals embedded in amorphous SiO₂ and Lu₂O₃ were investigated using ANSYS, Rietveld refinement method, high-resolution transmission electron microscopy (HRTEM), X-ray diffractometry (XRD) and photoluminescence spectroscopy (PL), respectively. The main results achieved in this thesis can be summarized as follows:1,HRTEM showed the Ge nanocrystals embedded in SiO₂ and Lu₂O₃ are spherical shape. The formation mechanism of Ge nanocrystals is also explained.2,The bond lengths of Ge nanocrystals in Lu₂O₃ and SiO₂ matrices are smaller than that of bulk Ge using the Rietveld refinement method. This is due to the Ge nanocrystals experienced compressive stress in the both matrices. Furthermore, it is found that the bond lengths of Ge nanocrystals in Lu₂O₃ matrix is smaller than that in SiO₂ matrix, which can be attributed to the greater compressive stress exerted on Ge nanocrystals by the Lu₂O₃ matrix. The Rietveld method was performed by the Fullprof computer program.3,Two dimensional finite element calculations clearly reveal that Ge nanocrystals certainly experienced greater compressive stress in Lu₂O₃ thin film than in SiO₂ thin film. These results are in agreement with the results of the Rietveld refinement method.4,Photoluminescence (PL) property of the Ge nanocrystals in both samples is analyzed by photoluminescence spectroscopy at low temperature. The enhancement PL intensity was observed in the sample with Ge nanocrystals embedded in Lu₂O₃ matrix. The difference of PL intensity is believed to originate from the various compressive stresses in these samples. The Ge nanocrystal in Lu₂O₃ matrix experienced greater compressive stress in comparison with that in SiO₂ matrix. This may lead to much more defects at the interface of Ge nanocrystals embedded in Lu₂O₃ matrix, thus lead to the enhancement of PL intensity.In conclusion, the influence of the matrix environment plays a significant role in the PL and varying of bond lengths of Ge nanocrystals.