Lead lanthanum zirconate titanate (PLZT) thin films with different La concentrations (x), whose composition is x/40/60, have been grown directly on Pt/Ti/SiO2/Si (100) substrates by a modified sol-gel method. X-ray diffraction analysis shows that the PLZT thin films are polycrystalline. The infrared optical properties of the PLZT thin films have been investigated using the infrared spectroscopic ellipsometry in the spectral range of 2.5–12.5 μm. By fitting the measured ellipsometric spectra (Ψ andΔ) with a three-phase model (air/PLZT/Pt), and a derived classical dispersion relation for the thin films, the optical constants and thicknesses of the thin films have been obtained. The refractive index of the PLZT thin films decreases with increasing La concentrations, however, the extinction coefficient increases with increasing La concentrations except for the PLZT(4/40/60) thin films. The values of the effective static charge calculated for the PLZT thin films, which state that PLZT belongs to a mixed ionic-covalent compound, decrease with increasing La concentrations. Moreover, the refractive index at the wavelength of 2.5 μm changes linearly with the effective static charge. The plot of the calculated infrared optical absorption versus wavelength for the Ni/PLZT/Pt multilayer structures with various La concentrations is given and indicates that the PLZT thin films are excellent candidates for ferroelectric infrared detectors and focal plane arrays.

(Pb1−xLax)Ti1−x/4O3 (PLT) ferroelectric thin films with various La concentrations have been grown on LaNiO3/Si(100) substrates by a modified sol-gel technique. X-ray-diffraction analyses show that the PLT and LaNiO3 thin films are polycrystalline and entirely perovskite phase. The infrared optical properties of the PLT thin films have been investigated using infrared spectroscopic ellipsometry in the wavelength range of 2.5-12.5 μm. By fitting the measured ellipsometric parameter (tanΨ and cos Δ) data with a four-phase model (air/PLT/LaNiO3/Si), and a derived dispersion relation for the PLT thin films, the optical constants and thicknesses of the thin films have been determined. The refractive index of the PLT thin films decreases with increasing wavelength; however, by a Kramers-Kronig analysis the extinction coefficient increases with increasing wavelength. Moreover, the refractive index and extinction coefficient of the PLT thin films increase with increasing La concentration. This indicates that the infrared optical constants of the PLT thin films are a function of the La concentration. It is believed that the increase in the infrared optical constants of the PLT thin films with increasing La concentration is mainly due to the crystallinity and the electronic band structure of the PLT thin films.

The reflectance measurements of p-type GaSb: Zn epitaxial films with different hole concentrations, grown by metalorganic vapor-phase epitaxy, have been investigated in the 3-30-THz frequency region. The experimental spectra were fitted using a classical harmonic Lorentz oscillator and the Drude model, illustrating that the hole effective mass and the mobility change with the carrier concentration. The hole effective mass was found to vary from 0.22m to 0.41m as the carrier concentration changed from 3.5×1017 to 3.8×1018 cm−3. The mobility values derived from the reflectance measurements were slightly smaller than the values obtained from Hall-effect measurements. A sublinear relationship between the absorption coefficient and the hole concentration was found at a frequency of 3 THz. Those results can be used for designing GaSb-based terahertz detectors.

The optical properties of hexagonal AlxGa1−xN x from 0.05 to 0.42 epitaxial films with Sim doping concentrations up to 1018 cm−3 grown on c-plane sapphire substrates by metal-organic chemical vapor deposition have been investigated using infrared reflectance spectra. The dielectric functions=1+i2 of the AlxGa1−xN films are determined in the wavelength region of 1.54-50m at room temperature. The experimental reflectance spectra are analyzed using classical harmonic Lorentz oscillators and Drude model in the transparent,reststrahlen, and free carrier absorption regions. GaN-like E1 transverse-optical TO phonon frequency linearly decreases and its strength increases with decreasing Al composition. However, AlN-like E1 TO phonon frequency shows a relatively weak composition dependence and its strength increases with increasing composition. At a wavelength of 1.54m, 1 varies between 4.86 and 5.2 when the composition changes from 0.05 to 0.42 and 2 is close to zero. The longitudinal-optical phonon plasmon LPP coupled modes of n-type hexagonal AlxGa1−xN films are also discussed. For samples with higher concentrations beyond 1018cm−3 the upper LPP coupled mode frequencies increase with increasing carrier concentration indicating the transition from phononlike to plasmonlike behavior.

Reflectance measurements from p-type GaSb: Zn epitaxial films with different hole concentrations(1017-1018 cm−3) have been investigated over the frequency region of 100-1000 cm−1. A minimum broadening feature corresponding to the hole plasmon was observed in the reflectance spectra. The experimental infrared spectra were well fitted using a Lorentz-Drude dispersion model. The real part ε1 of the dielectric function decreases with increasing hole concentration. However, the imaginary part ε2 increases with hole concentration in the far-infrared region. This indicates that the acoustic- and optic-phonons mainly participate in the free carrier absorption processes. The hole mobility obtained from Hall-effect measurements is slightly larger than that derived from optical measurements and the average ratio of mobilities is estimated to be 1.33. Owing to overdamping effects, the upper branch of longitudinal-optical phonon plasmon (LPP) coupled modes was observed. The upper LPP+ frequency increases with hole concentration and it shows a transition from phonon-like to plasmon-like behavior. A theoretical analysis with solutions in the complex frequency plane describes these experimental results.