Structure And Optical Properties Of The Semiconductor/SiO₂ Nanocrystals Embedded Thin Films

The GaP nanocrystals embedded in SiO2 matrix were prepared on Si substrate by radio frequency magnetron co-sputtering and subsequent annealing technology. The structure and morphology of the films were investigated by scanning electron microscope (SEM), X-ray diffraction (XRD), and energy dispersive spectrum (EDS). The results showed that GaP nanocrystals were formed in the thin films.Raman spectra results showed that transverse optical phonon model (TO) and longitudinal optical phonon model (LO) of GaP nanocrystals were both discovered to undergo red shift, broadening, and asymmetry. The red shift degree of the TO model was about 8.8 cm-1. They were connected with the combined action of finite size effect and stress. The red shift and broadening of the Raman peaks was explained by residual stress, phonon confinement effect and interface effect. 2.84 eV ~ 2.54 eV blue light emission was explained by quantum confinement-luminescence centers model (QC-LCs). The origin of 3.1 eV violet light emission was attributed to the related defects between SiO2 matrix and nc-GaP, and/or Ga-O related defect centers.Colligated the structure and Raman scattering information of the Ge/SiO2, InP/SiO2, GaP/SiO2 films, the structure of the semiconductor/ SiO2 films on Si substrate were described on macroscopic. The growth mechanism of the embedded semiconductor nanocrystals in film was discussed, and the growth inhibition mechanism put forward. It is considered that the growth for quantum dot was restrained by stress filed and medium potential barrier. From the crystal structure the interface structures in film were discussed and reckoned that interface energy level can exist in the band gap. The possible actions of P and O to the film structure and energy level were investigated.Three kind of semiconductor/SiO2 thin films all present strong photoluminescence. The possible recombination luminescence energy band models were investigated. The main luminescence peaks for Ge/SiO2, GaP/SiO2 thin films were both at 391~394 nm (3.15~3.17eV), and these emission were explained by the model of quantum confinement- luminescence centers (QC-LCs). The emissions at 581 nm (2.13 eV) for InP/SiO2, 432 nm (2.87 eV) for Ge/SiO2 thin films were regarded as the band-to-band transition caused by quantum confinement effect. A series of spiting blue emission was considered as excited by confinement exciton which at 436 nm ~ 487 nm (2.84 eV~2.54 eV) for GaP/SiO2 thin film. It showed that the quantum confinement effect of the semiconductor quantum dot embedded in matrix and the interface energy level play an important role in luminescence properties for semiconductor/SiO2 thin films.