Investigation On The Optical And Dielectric Properties Of Nano-Films By Ellipsometer

Compared with other conventional methods, Spectroscopic Ellipsometer(SE) is a powerful, non-destructive, non-rigorous measure tools with high precision and high sensitivity. Hence, it is widely used in investigation of various materials’optical and dielectric properties.By using SE, one can directly obtain ellipsometric parameters(Ψ and△) as a func-tion of wavelength. After measure process, many parameters such as dielectric func-tions, complex refractive index, layer thickness, and the property of surface can be de-termined by modeling. In order to deeply understand SE, this study will be carried out from several aspects as follow:First, chapter1is devoted to introduce the characteristics of lights, such as reflec-tion, refraction and polarization. In addition, the properties of various polarized light are also investigated. SE’s characteristics and applications in many kinds of functional film materials are also discussed. Furthermore, different models and its applicability are also analyzed. Mean Square Error(MSE) is a judge standard whether the model is appropriate or not.In chapter2, α-Co films with different thickness were prepared by sputtering. The XRD results suggest Co is Hexagonal Close Packing Structure. Then ellipsomet-ric parameters were measured by Variable Angles Spectroscopic Ellipsometer(VASE). Choosing various models for films with different thickness:the film thicker than100nm, can be treated as bulk materials, while the films thinner than100nm are modeled by Multiple Samples Method or Oscillator Formula Method, and the results proves the Oscillator Formula can obtain believable results. Meanwhile, we confirmed the Multi-ple Samples Method is suitable for the films whose thickness is between10nm and40nm. The optical and dielectric properties are also acquired through the optimal model. Finally, SEM results confirm the fit thickness is believable.In chapter3, TiO2films with different thickness were prepared by sputtering. The XRD results suggest TiO2is Rutile. Then ellipsometric parameters were measured by Variable Angles Spectroscopic Ellipsometer(VASE). We analyzed the reason why the Mean Square Errors(MSE) is rather high in the wavelength range below400nm. Fi-nally, choosing Cauchy Urbach Extinction Models for all films with different thickness in400-1700nm, then we further optimized the models by adding Surface Roughness Layer. The SEM results prove the fit thickness is believable.In chapter4, ZnO films were prepared in various sputtering conditions. It is ap-proved that ZnO is Hexagonal Wurtzite by XRD. Then ellipsometric parameters were measured by Variable Angles Spectroscopic Ellipsometer(VASE). Similarly, we used Cauchy Urbach Extinction Models for all ZnO films in400-1700nm. Finally, we con-firmed whether the fit thickness is believable through SEM.