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Preparation and Optical Properties of SiO2 Based Composite Thin Films

Author: SunXiaoFei
Tutor: WeiChangPing
School: Changchun University of Science and Technology
Course: Materials Physics and Chemistry
Keywords: Ag/SiO2 Au/SiO2 Ag-Au alloy / SiO2 ZnO/SiO2 Composite films Doping UV irradiation Optical Performance
CLC: TB383.2
Type: PhD thesis
Year: 2009
Downloads: 198
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Abstract


The nano-sized metal (especially Ag and Cu) embedded in the inorganic oxide particles and the medium (such as glass, ceramics, etc.) in the formation of nano-composite material having a different optical properties of the bulk material, such as an optical nonlinearity (including plasmon resonance), optical absorption, photoluminescence and so on. Because of these properties, such nanocomposites in optical switches, optical waveguide devices, optical filters and display devices, and so has a very broad application prospects. In recent years, the preparation of such materials and properties of materials science and physics is becoming an important field of research. Sol - gel method and spin coating techniques, by UV irradiation and heat treatment have been different Ag content uniformity good Ag/SiO2 nanocomposite thin films, the film structure is dense, basically no holes. Film of Ag nanoparticles tissue distribution is more uniform, the size is very small. With nAg / nsi increases, Ag nanoparticles around 420nm UV - visible absorption gradually increased, and a certain redshift. In nAg / nsi = 0.05,0.08 film obtained by UV irradiation samples, respectively, at 640nm and 690nm or so there is a broad absorption peak is due to a small amount of Ag particles larger due. The resulting film sample UV radiation absorbing properties of the light treatment is superior to 300 ℃ 1h sample obtained. Raman spectra showed that the surface of Ag nanoparticles local field enhancement caused by surface-enhanced Raman scattering, making the sample substrate peak intensity is 5 times. Reduction obtained by UV irradiation good uniformity Au/SiO2 composite film, the resulting composite film Au/SiO2, the nanoparticles are small in size and evenly distributed; composite film shows a light absorption properties, Au nanoparticles Surface plasmon resonance absorption peak as the calcination temperature increases and nAu / nsi changes gradually from near 585 nm red shift near 600 nm, and gradually increased. According to Maxwell-Gamett Mie theory and the effective medium theory, composite film shape and position of the absorption peak of the gold particles and the dielectric constant of the dielectric constant determined by the film densification, the matrix increase the dielectric constant, nAu / nsi The larger the larger gold particles, resulting in the absorption band of the composite film redshift. With AgNO3, HAuCl4 and TEOS as the main raw material, the use of sol - gel method and spin-coating technology, through heat and UV radiation obtained for different nAg / nAu (1:0,2:1,1:2, 0:1) of the Ag-Au alloy / SiO2 composite film. From the SEM, XRD and other characterization methods results can be seen in the resulting nanocomposite film alloy particle size of about 10 nm, the resulting film uniformity; by ultraviolet-visible spectrophotometer of the composite optical absorption properties, The results showed that with nAg / nAu decrease in the peak position from the initial Ag nanoparticle plasmon resonance absorption (SPR) peak near 430 nm, and gradually move to gold nanoparticles red plasmon resonance absorption peak near 605nm and 880nm . As can be seen from the light absorption spectrum, nAg: nAu = 2:1 and 1:2 respectively, in two samples of 515 nm, 730 nm and near 550 nm, 730 nm in the vicinity of the surface plasmon absorption peak indicates the Au-Ag alloy solid solution formation. Sol - gel method on glass substrates were prepared ZnO/SiO2 composite film, the temperature influence on ZnO/SiO2 composite film structure and optical properties were investigated ZnO content on optical properties of thin films. Test results show that the temperature is conducive to the crystallization and reduce structural defects, but also to promote the film within the particles agglomerate. Composite film after heat treatment at 400 ℃ better transmittance, the sample has a strong blue emission peak area. The increased ZnO content can adjust the optical band gap, and enhancement film in the ultraviolet and blue region of the photoluminescence intensity. The effects of Ag doping on the composite film structure and optical properties. The results show that the heat treatment at 300 ℃ elemental Ag film has generated increased as the content of Ag, Ag and ZnO and Ag electron transfer between particles becomes large to promote the characteristic absorption peak of Ag rendering red shift and broadening. After incorporation of Ag and interstitial Zn site instead of the hole concentration and reduce structural defects, so that the sample in the ultraviolet and visible region of the emission intensity decreased.

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