Silicon Nanocrystals And Ferroelectric Thin Films Spectroscopic Ellipsometry

Spectroscopy ellipsometry(SE) is a non-destructive and non-contacting measurement method,since its mechanism is suitable for film detecting,it has become an important technology to investigate the optical properties of thin films.In this work,spectroscopy ellipsomerty measurement is applied to study the optical properties of Silicon nanocrystals(nc-Si) and Bi_3.15Nd_0.85Ti₃O₁₂(BNdT) ferroelectric thin film,and the results of spectra fitting of ellipsometry are discussed.1.Silicon nanocrystals(nc-Si) is Si crystalline in nano-scale.It has gained main research interest because of its excellent properties of photoluminescence(PL).In this work,SiO_x/SiO₂(1＜x＜2) superlattice approach is employed to synthesize size-controlled nc-Si embedded in SiO₂ matrix.PL spectra and SE measurement are carried out to investigated the properties of nc-Si.The PL spectra indicates the nc-Si embedded in SiO₂ matrix have an uniform size.The ellipsometry parameters are fitted by effective medium approximation(EMA) and Lorentz oscillator model and the complex dielectric functions of nc-Si are obtained.Compared to bulk Si,the amplitude of the dielectric function decreases as the size decreases.The decreasing size of the crystalline also results in a different peak position of the imaginary part of the dielectric functions,which vary with the size of the nc-Si.Preparation of nc-Si by electron beam evaporation is tested.The nc-Si is successfully segregated in the SiO₂ matrix after the annealing.Atomic force microscopy(AFM),PL spectra and SE measurement are applied to characterized the properties of the nc-Si.Improvement of the target and control of the evaporation facility is needed to get a better size control of the nc-Si.2.SE measurement is carried out to study the optical properties of the BNdT ferroelectric thin film.Different fitting model are applied separately in the absorbing and transparent section of the optical spectra to get a well fit of the ellipsometry parameters.The refractive index and extinction coefficient of BNdT thin film in the spectra range 280 nm～820 nm combining of absorbing and transparent section are obtained.The results of two different model match each other well in the critical point between the absorbing section and transparent section of the spectra.