ZnO/SiO2 复合薄膜的光学性能

采用溶胶-凝胶法在玻璃衬底上制备ZnO/SiO₂复合薄膜,分别用XRD、TEM、SEM对样品的结构和形貌进行表征,并研究了不同ZnO含量对复合薄膜透过率及荧光特性的影响。结果表明,样品经500 ℃退火处理生成了SiO₂和ZnO,其晶粒尺寸为18.7 nm,薄膜具有双层结构。复合薄膜的透过率随着其中ZnO含量的增加而降低,禁带宽度减小,光学吸收边红移。样品在355 nm波长激发下产生了384 nm的紫外发射峰和440 nm的蓝光发射带,并随ZnO含量的增加而增强,它们分别来自ZnO的电子-空穴复合发光和缺陷发光,及ZnO/SiO₂复合薄膜双层结构的缺陷发光。

Optical Properties of ZnO/SiO2 Composite Film

ZnO/SiO2 composite film was deposited on glass substrates by means of sol-gel method. The crystal structure and morphology of samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM),respectively. The transmittance and photoluminescent properties of ZnO/SiO2 composite film with different concentration of ZnO were studied. The results indicated that the composite film is composed of SiO2 and ZnO two kinds of oxide after annealed in air at 500 ℃, and the crystal particle size calculated by Scherrer formula is 18.7 nm. The results of SEM showed that two-layer structure can be observed clearly. Selected area diffraction (SAED) indicated that the structure of ZnO/SiO2 composite film is polycrystal. Transmittance of film decreases with the content of ZnO increasing, and the band gap diminishes from 3.5 eV to 3.2 eV, which indicates that optical absorption edge moved to long wavelength. The PL spectra show there are two luminescence locations under 355 nm light excitation, one is the broad emission peaked at 384 nm and the other is the blue band peaked at 440 nm. Both of them are attributed to the electron-hole recombination and defect luminescence of ZnO,respectively. In this paper, the coating method is that two kinds of solution are coated, respectively. So, the two-layer structure of ZnO/SiO2 composite film must be considered. As there is a ZnO/SiO2 interface in the two-layer film, so the structure defect, bond defect and the deep level centers caused by crystal lattice aberrance would be formed after annealed at 500 ℃, these defects and deep level centers can influence the photoluminescent properties of composite film in a certain extent. At the same time, defect center (O—Si—O) of oxygen deficiency in SiO2 could contribute to the blue emission, too.