纳米TiO2薄膜的脉冲激光沉积及其光学特性

采用脉冲激光沉积技术(PLD)在硅基片上生长了二氧化钛纳米晶氧化物薄膜, 系统讨论了基片温度、氧分压等因素对薄膜结构特性的影响.X射线衍射结果表明在氧气氛下, 生长的薄膜为锐钛矿结构, 其结晶性随着基片温度的升高而增强, 在750℃、5Pa氧压的情况下为完全c轴取向的锐钛矿相TiO₂薄膜, 在750℃、5Pa氩气氛下则为(110)取向的金红石相薄膜. 场发射扫描电子显微镜结果表明薄膜表面致密, 呈纳米晶结构, 其晶粒尺寸在35nm左右.用傅立叶红外光谱和拉曼光谱对不同条件下制备的TiO₂薄膜进行了表征.紫外-可见透射光谱的测试结果表明, 薄膜在可见光区具有良好的透过率, 计算得到制备的锐钛矿和金红石相TiO₂薄膜在550nm处的折射率分别为2.3和2.5, 其光学带隙分别为3.2和3.0eV.因此通过沉积条件的改变可得到结晶性能和光学性能都不同的TiO₂薄膜.

Pulsed Laser Deposition of Nanocrystal TiO2 Films and its Optical Properties

Titanium dioxide nanocrystal films were deposited on silicon substrates using pulsed laser deposition method. The influences of substrate temperature, oxygen partial pressure and the kinds of gas on the crystal structure of TiO₂ thin films were discussed. The optical properties of films were studied by means of transmission spectra in UV-visible range, Fourier transform infrared spectra and Raman spectra. The results show that the films are high c-axis-oriented anatase and (110) oriented rutile prepared at the substrate temperature of 750℃ under the oxygen and argon pressure of 5Pa, respectively. The field emission scanning electron microscopy images indicate that the TiO₂ films has a good smooth and hole-free surface which are composed of nanocrystal grains with about 35nm in diameter. And the optical properties tested show that the films are transparent in the visible range. From the transmission spectra in UV-visible range, the refractive index of the anatase and rutile TiO₂ films are determined to be about 2.3 and 2.5 at 550nm, respectively. And the optical band gaps are determined to be 3.2eV and 3.0eV for the anatase film and rutile film, respectively.