Nanocrystalline silicon embedded SiO2 matrix is formed by annealing the SiOx films fabricated by plasma enhanced chemical vapor deposition technique. In conjunction with the micro-Raman spectra, the absorption spectra...Nanocrystalline silicon embedded SiO2 matrix is formed by annealing the SiOx films fabricated by plasma enhanced chemical vapor deposition technique. In conjunction with the micro-Raman spectra, the absorption spectra of the films have been investigated. The blue-shift of absorption edge with decreasing size of silicon crystallites is due to quantum confinement effect. It is found that nanocrystalline silicon is of an indirect band structure, and that the absorption presents an exponential dependence of absorption coefficient on photon energy in the range of 2.0-3.0eV, and a sub-band appears in the range of 1.0-1.5eV. We believe that the exponential absorption is due to the indirect band-to-band transition of electrons in silicon nanocrystallites, while the sub-band absorption is ascribed to transitions between the amorphous silicon states existing in the films.展开更多
Nanocrystalline silicon embedded SiO<sub>2</sub> matrix has been formed by annealing the a-SiO<sub>x</sub> films fabricated by plasma enhanced chemical vapor deposition technique. Absorption an...Nanocrystalline silicon embedded SiO<sub>2</sub> matrix has been formed by annealing the a-SiO<sub>x</sub> films fabricated by plasma enhanced chemical vapor deposition technique. Absorption and photoluminescence spectra of the films have been studied in conjunction with micro-Raman scattering spectra. It is found that absorption presents an exponential dependence of absorption coefficient to photon energy in the range of 1.5—3.0 eV, and a sub-band appears in the range of 1.0—1.5 eV. The exponential absorption is due to the indirect band-to-band transition of electrons in silicon nanocrystallites, while the sub-band absorption is ascribed to transitions between surfaces and/or defect states of the silicon nanocrystallites. The existence of Stokes shift between absorption and photoluminescence suggests that the phonon-assisted luminescence would be enhanced due to the quantum confinement effects.展开更多
Two strong photoluminescence （PL） bands in the spectral range of 550\900 nm have been observed at room temperature from a series of a\|SiO\-\%x\%∶H films fabricated by plasma\|enhanced chemical vapor deposition （P...Two strong photoluminescence （PL） bands in the spectral range of 550\900 nm have been observed at room temperature from a series of a\|SiO\-\%x\%∶H films fabricated by plasma\|enhanced chemical vapor deposition （PECVD） technique. One is composed of a main band in the red\|light region and a shoulder; the other is located at about 850 nm, only found after 1170℃ annealing in N\-2 atmosphere. In conjunction with infrared （IR） and micro\|Raman spectra, it is thought that the two PL bands are associated with a\|Si clusters in the SiO\-\%x\% network and nanocrystalline silicon in SiO\-2, respectively.展开更多
Raman scattering of nanocrystalline silicon embedded in SiO2 matrix is systematically in-vestigated. it is found that the Raman spectra can be well fitted by 5 Lorentzian lines in the Raman shift range of 100-600 cm-1...Raman scattering of nanocrystalline silicon embedded in SiO2 matrix is systematically in-vestigated. it is found that the Raman spectra can be well fitted by 5 Lorentzian lines in the Raman shift range of 100-600 cm-1. The two-phonon scattering is also observed in the range of 600-1100 cM-1 The experimental results indicate that the silicon crystallites in the films consist of nanocrystalline phase and amorphous phase; both can contribute to the Raman scattering. Besides the red-shift of the first order optical phonon modes with the decreasing size of silicon nanocrystallites, we have also found an enhancement effect on the second order Raman scattering, and the size effect on their Raman shift.展开更多
文摘Nanocrystalline silicon embedded SiO2 matrix is formed by annealing the SiOx films fabricated by plasma enhanced chemical vapor deposition technique. In conjunction with the micro-Raman spectra, the absorption spectra of the films have been investigated. The blue-shift of absorption edge with decreasing size of silicon crystallites is due to quantum confinement effect. It is found that nanocrystalline silicon is of an indirect band structure, and that the absorption presents an exponential dependence of absorption coefficient on photon energy in the range of 2.0-3.0eV, and a sub-band appears in the range of 1.0-1.5eV. We believe that the exponential absorption is due to the indirect band-to-band transition of electrons in silicon nanocrystallites, while the sub-band absorption is ascribed to transitions between the amorphous silicon states existing in the films.
基金NationalNaturalScienceFoundationofChina(No .6980600669976014+1 种基金69636010and 69987001) the National High Technology Research & Development Project of China ( No.863-715-001-0030)
文摘Nanocrystalline silicon embedded SiO<sub>2</sub> matrix has been formed by annealing the a-SiO<sub>x</sub> films fabricated by plasma enhanced chemical vapor deposition technique. Absorption and photoluminescence spectra of the films have been studied in conjunction with micro-Raman scattering spectra. It is found that absorption presents an exponential dependence of absorption coefficient to photon energy in the range of 1.5—3.0 eV, and a sub-band appears in the range of 1.0—1.5 eV. The exponential absorption is due to the indirect band-to-band transition of electrons in silicon nanocrystallites, while the sub-band absorption is ascribed to transitions between surfaces and/or defect states of the silicon nanocrystallites. The existence of Stokes shift between absorption and photoluminescence suggests that the phonon-assisted luminescence would be enhanced due to the quantum confinement effects.
文摘Two strong photoluminescence （PL） bands in the spectral range of 550\900 nm have been observed at room temperature from a series of a\|SiO\-\%x\%∶H films fabricated by plasma\|enhanced chemical vapor deposition （PECVD） technique. One is composed of a main band in the red\|light region and a shoulder; the other is located at about 850 nm, only found after 1170℃ annealing in N\-2 atmosphere. In conjunction with infrared （IR） and micro\|Raman spectra, it is thought that the two PL bands are associated with a\|Si clusters in the SiO\-\%x\% network and nanocrystalline silicon in SiO\-2, respectively.
文摘Raman scattering of nanocrystalline silicon embedded in SiO2 matrix is systematically in-vestigated. it is found that the Raman spectra can be well fitted by 5 Lorentzian lines in the Raman shift range of 100-600 cm-1. The two-phonon scattering is also observed in the range of 600-1100 cM-1 The experimental results indicate that the silicon crystallites in the films consist of nanocrystalline phase and amorphous phase; both can contribute to the Raman scattering. Besides the red-shift of the first order optical phonon modes with the decreasing size of silicon nanocrystallites, we have also found an enhancement effect on the second order Raman scattering, and the size effect on their Raman shift.
