The electronic structure of III-V zinc blend Gallium Phosphide nanocrystals is investigated using ab-initio density functional theory coupled with large unit cell for the core and surface parts. Two kinds of cells are...The electronic structure of III-V zinc blend Gallium Phosphide nanocrystals is investigated using ab-initio density functional theory coupled with large unit cell for the core and surface parts. Two kinds of cells are investigated: multiple Bravais and multiple primitive cells. The results show that both energy gap and valence band width depend on the shape of the nanocrystal. Results also revealed that most electronic properties converge to some limit as the size of the large unit cell increases. Furthermore, the results have shown that the cohesive energy is decreasing with increasing size of nanocrystals. The core part is more degenerate, with larger energy gap and smaller valance and conduction bands than the surface.展开更多
The three-photon absorption (3PA) in nanostructure wide-band gap ZnO semiconductor material is observed under high intensity femtosecond Titanium-Sapphire laser of 800 nm wavelength excitation. The ZnO film was prepar...The three-photon absorption (3PA) in nanostructure wide-band gap ZnO semiconductor material is observed under high intensity femtosecond Titanium-Sapphire laser of 800 nm wavelength excitation. The ZnO film was prepared by chemical spray pyrolysis technique with substrate temperature of 400℃. The optical properties concerning the absorp-tion, transmission, reflection, Raman and the photoluminescence spectra are studied for the prepared film. The structure of the ZnO film was tested with the X-Ray diffraction and it was found to be a polycrystalline with recognized peaks oriented in (002), and (102). The measured of three photon absorption coefficient was found to be about 0.0166 cm3/Gwatt2, which is about five times higher than the bulk value. The fully computerized z-scan system was used to measure the nonlinear coefficients from the Gaussian fit of the transmitted laser incident.展开更多
Strong nonlinear absorption in CdS nanoparticles of dimensions in the range 4 - 50 nm when irradiated with a femtosecond pulsed laser at 800 nm is observed. The CdS nanoparticles sizes were controlled by changing the ...Strong nonlinear absorption in CdS nanoparticles of dimensions in the range 4 - 50 nm when irradiated with a femtosecond pulsed laser at 800 nm is observed. The CdS nanoparticles sizes were controlled by changing the reaction time of aqueous solutions of thiourea and cadmium chloride. The structure of the prepared CdS nanoparticles were tested and their optical properties were investigated and the nonlinear absorption coeffi-cients were measured using a fully computerized z-scan unit. It is found that the formation of the CdS nanos-tructuresfor are responsible for the observation of the strong tow photon absorption.展开更多
文摘The electronic structure of III-V zinc blend Gallium Phosphide nanocrystals is investigated using ab-initio density functional theory coupled with large unit cell for the core and surface parts. Two kinds of cells are investigated: multiple Bravais and multiple primitive cells. The results show that both energy gap and valence band width depend on the shape of the nanocrystal. Results also revealed that most electronic properties converge to some limit as the size of the large unit cell increases. Furthermore, the results have shown that the cohesive energy is decreasing with increasing size of nanocrystals. The core part is more degenerate, with larger energy gap and smaller valance and conduction bands than the surface.
文摘The three-photon absorption (3PA) in nanostructure wide-band gap ZnO semiconductor material is observed under high intensity femtosecond Titanium-Sapphire laser of 800 nm wavelength excitation. The ZnO film was prepared by chemical spray pyrolysis technique with substrate temperature of 400℃. The optical properties concerning the absorp-tion, transmission, reflection, Raman and the photoluminescence spectra are studied for the prepared film. The structure of the ZnO film was tested with the X-Ray diffraction and it was found to be a polycrystalline with recognized peaks oriented in (002), and (102). The measured of three photon absorption coefficient was found to be about 0.0166 cm3/Gwatt2, which is about five times higher than the bulk value. The fully computerized z-scan system was used to measure the nonlinear coefficients from the Gaussian fit of the transmitted laser incident.
文摘Strong nonlinear absorption in CdS nanoparticles of dimensions in the range 4 - 50 nm when irradiated with a femtosecond pulsed laser at 800 nm is observed. The CdS nanoparticles sizes were controlled by changing the reaction time of aqueous solutions of thiourea and cadmium chloride. The structure of the prepared CdS nanoparticles were tested and their optical properties were investigated and the nonlinear absorption coeffi-cients were measured using a fully computerized z-scan unit. It is found that the formation of the CdS nanos-tructuresfor are responsible for the observation of the strong tow photon absorption.
