真空度对TiO_2薄膜光学和结构特性的影响

为制备高性能TiO2光学薄膜,采用离子束辅助,电子束蒸发沉积的方法,研究不同真空度对薄膜性能的影响。真空度随真空室内通氧量增大从1.3×10-3Pa变化到2.5×10-3Pa,得到不同光学和结构特性的TiO2薄膜。采用分光光度计测试其光谱,SEM测试其表面形貌。测试结果发现,TiO2薄膜的透过率峰值随真空度降低而增大,折射率和消光系数随真空度降低而减小,薄膜表面形貌随真空度降低从致密变粗糙。在真空度2.0×10-3Pa的工艺条件下,成膜质量最佳,此时最大透过率92%,折射率在2.45～2.20之间,消光系数在10-4以下。根据Cauchy公式拟合其色散规律,拟合曲线和采用包络法计算得到的曲线较好重合,折射率随波长的变化公式为n(λ)=2.12+5.69×104/λ2+8.07×107/λ4。

INFLUENCE OF VACUUM DEGREE ON THE OPTICAL AND STRUCTURE PROPERTIES OF TIO2 FILMS

In order to get high capability titanium dioxide optical thin films, have synthesized by ion beam sputtering （IBS） and Ion Beam Assisted Deposition （IAD） at different vacuum degree. When the rate of oxygen increased, the value of vacuum degree is rising from1.3×10-4 Pa to 2.5×10-4Pa. Spectrophotometer is used to test spectrum, the surface were characterized by scanning electron microscope （SEM）. When the vacuum degree decreased , it is found that the tiptop transmittance of titanium dioxide is increasing、the refractive index and the extinction coefficient are decreased and the surface quality changes roughness.When the vacuum degree is 2.0×10-3 Pa, we get the best quality titanium dioxide optical thin film. The tiptop transmittance is 92%; The refractive index changes from 2.45 to 2.20;The extinction coefficient of the thin film is below 10-4. Using Cauchy chromatic dispersion formula, the fitting curve accord well with the result by the envelope method, the formula of the refractive index change with wavelength is n（λ）=2.12＋5.69×104/λ2＋8.07×107/λ4.