Infrared dielectric function spectra and phonon modes of high-quality, single crystalline, and highly resistive wurtzite ZnO films were obtained from infrared (300–1200 cm−1) spectroscopic ellipsometry and Raman scattering studies. The ZnO films were deposited by pulsed-laser deposition on c-plane sapphire substrates and investigated by high-resolution x-ray diffraction, high-resolution transmission electron microscopy, and Rutherford backscattering experiments. The crystal structure, phonon modes, and dielectric functions are compared to those obtained from a single-crystal ZnO bulk sample. The film ZnO phonon mode frequencies are highly consistent with those of the bulk material. A small redshift of the longitudinal optical phonon mode frequencies of the ZnO films with respect to the bulk material is observed. This is tentatively assigned to the existence of vacancy point defects within the films. Accurate long-wavelength dielectric constant limits of ZnO are obtained from the infrared ellipsometry analysis and compared with previously measured near-band-gap index-of-refraction data using the Lyddane–Sachs–Teller relation. The ZnO model dielectric function spectra will become useful for future infrared ellipsometry analysis of free-carrier parameters in complex ZnO-based heterostructures.

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Imaging ellipsometry is presented as a technique for quantification and visualization of the lateral thickness distribution of thin ͑0-30 nm͒ transparent layers on solid substrates. The main advantage of imaging ellipsometry is that every point on a surface is measured at the same time with a high lateral resolution. The method is based on the use of combined null and off-null ellipsometry at an incident angle close to the pseudo-Brewster angle of a high index substrate such as silicon. In the present experimental setup, a xenon lamp, a collimator, and a wavelength-selective filter provide an expanded collimated probe beam with a diameter of 25 mm. Other major components in the system are a polarizer, a compensator, and an analyzer. In this way, a 15ϫ30 mm 2 image of a sample surface can be focused onto a charge-coupled-device video camera and transferred to a computer for further evaluation by image processing. Thickness measurements are performed for calibration purposes with ordinary null ellipsometry. The imaging ellipsometer has an accuracy of better than 0.5 nm at a lateral resolution of 5 m in the present configuration, but improvements of at least a factor of 5 can be foreseen. Several aspects of the ellipsometric imaging system are illustrated in selected applications including continuous protein thickness distributions, stepped silicon dioxide thickness distributions, and visualization of protein patterning of surfaces. The latter can be used in a biosensor system as illustrated here by antigen-antibody binding studies.

Variable angle spectroscopic ellipsometry (VASE) has been used in the photon energy range 1.25–5.0 eV to study the structure and optical properties of cerium dioxide (CeO2) films. Both amorphous and highly oriented crystalline films were grown on sapphire by rf magnetron sputtering. The crystallinity, chemical structure, and surface morphology of the films were studied by x-ray diffraction, x-ray photoelectron spectroscopy, and atomic force microscopy, respectively. The measured VASE spectra on a series of films with different thicknesses were analyzed by using multiple optical models. In this way, the complex refractive index N=n+ik of CeO2, the film thicknesses, and the surface roughness of the different films could be determined. The ellipsometrically deduced refractive index spectrum was observed to be strongly dependent on the film structure. Highly oriented crystalline CeO2 films exhibited a higher refractive index and a higher band gap energy than the amorphous film. The surface roughness of the crystalline films increased with film thickness. The optical dispersion relations have also been analyzed by line-shape fitting with a modified Lorentz oscillator model.

A concept for a measurement technique based on ellipsometry in conditions of total internal reflection is presented. When combined with surface plasmon resonance (SPR) effects, this technique becomes powerful for monitoring and analyzing adsorption and desorption on thin semitransparent metal films as well as for analyzing the semitransparent films themselves. We call this technique total internal reflection ellipsometry (TIRE). The theory of ellipsometry under total internal reflection combined with SPR is discussed for some simple cases. For more advanced cases and to prove the concept, simulations are performed with the Fresnel formalism. The use of TIRE is exemplified by applications in protein adsorption, corrosion monitoring, and adsorption from opaque liquids on metal surfaces. Simulations and experiments show greatly enhanced thin-film sensitivity compared with ordinary ellipsometry.