document: According to the ellipsometric spectra, optical constants and other physical parameters can be extracted by an appropriate fitting model. In order to estimate the optical constants/dielectric functions of Ni-doped TiO2 films, a three-phase layered system (air/film/substrate) [15] was utilized to study the ellipsometric spectra. TiO2 belongs to the wide band gap semiconductors. Considering the contribution of the M0 type critical point with the lowest three dimensions, its dielectric function can be calculated by Adachi's model [15,22,23]: ε(Ε)=ε∞+{A0[2−(1+χ0)1/2−(1−χ0)1/2]}/(EOBG2/3χ02). In the model, E is the incident photon energy, ε∞ is the high-frequency dielectric constant, χ0=(E+iΓ), EOBG is the optical gap energy, and A0 and Γ are the strength and broadening parameters of the EOBG transition, respectively. As an example, the experimental SE of the film TN1 at an incident angle 70° by dot scatter is shown in Fig. 4. The Fabry–Pérot interference oscillations due to multiple reflections within the film have been found in the photon energy from 1.5eV to 3.5eV (354nm–826nm), which indicates that the films are transparent in this region. Note that a good agreement of the experimental and calculated spectra is attained in the whole measured photon energy range. The fitting thickness for film TN2 is 159nm, which is very near to the value obtained by SEM (see Fig. 1(b)).
doc_bio_tags: O O O B I B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O B I I B O O O O O O B O O O O O O B I I O O B I I I O O B O O O O O O O B O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O
extractive_keyphrases: a0 and γ e ellipsometric spectra eobg fabry–pérot interference incident photon energy optical constants se sem semiconductors strength and broadening parameters ε∞
abstractive_keyphrases: adachi's model air/film/substrate high-frequency dielectric constant ni-doped tio2 films optical constants/dielectric three-phase layered system ε(ε)=ε∞+{a0[2−(1+χ0)1/2−(1−χ0)1/2]}/(eobg2/3χ02) χ0=(e+iγ)