A thin-film optical filter used as a one-dimensional spatial filter is presented, and its design is briefly examined. The filter consists of a stack of quarter-wave dielectric layers upon a right-angle prism that selectively cancel a reflected or transmitted plane-wave front for various angles of incidence. Transmittance and reflectance are low-pass functions or high-pass functions of the angle of incidence with a high degree of steepness. In combination, these filters exhibit bandpass transmittance with a variable bandwidth. Applications to detection of extrasolar planets are briefly discussed.

Polycrystalline transparent Zinc oxide thin films have been grown on glass substrates by the sol–gel technique using two different precursor solutions. The physical properties of the films were analyzed with X-ray diffraction, Atomic Force Microscopy, UV–Vis and Raman spectroscopy. The results show that the films grew in the hexagonal wurtzite structure. The band gap of the samples was estimated from UV–Vis measurements in values from 3.1 to 3.22eV, these values are in agreement with those reported in the literature. Two different simple ways to obtain polycrystalline ZnO were developed and the properties of the films were studied as a function of the precursor solution

Hafnium oxide films were deposited on sapphire and silicon (100) substrates using the DC reactive magnetron sputtering technique from a pure hafnium target at different discharge power levels. The influence of the cathode power on the chemical composition, morphology, crystallographic structure and optical properties of the films was investigated. X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX) and Fourier-transform infrared spectroscopy (FTIR) were employed to determine the chemical composition and bonding structure. In all cases, the films were found to be amorphous or nanocrystalline with increased crystalline content as the sputtering power was increased, according to XRD and FTIR. In addition, EDX showed that the films were oxygen-rich. The effect of power deposition on the surface topography and morphology of the films was studied using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The AFM and SEM images revealed the emergence of mound morphologies as the cathode power was increased. These features are related to blistering effects probably due to the presence of stress and its promotion within the film thickness. Finally, the optical properties showed an average transmission of 80% in the visible range, and the refractive index determined by spectral ellipsometry (SE) was found to be in the range of 1.85–1.92, close to the reported bulk value. SE was also used to study the film porosity observed by SEM, which can be related to the oxygen-rich character of the films.

Yttrium oxide films deposited by laser ablation on Si(100) substrates have been evaluated for possible application as high dielectric constant insulator layers. The structural, optical and electrical characteristics of these films have been determined by means of x-ray diffraction, atomic force microscopy, Auger electron spectroscopy, ellipsometry, infrared transmittance, and capacitance and current versus voltage $\mathrm{(C-V}$ and $\mathrm{I-V)}$ as a function of the deposition parameters. It has been found that the crystallinity of these films is strongly dependent on the substrate temperature during the deposition. At low deposition temperatures $\text{(350\hspace{0.17em}°}\mathrm{C})$ the films present an amorphous component and a polycrystalline part that is highly oriented in the (100) direction perpendicular to the surface of the film. As the deposition temperature is increased up to $\text{650\hspace{0.17em}°}\mathrm{C},$ the amorphous part of the films is reduced drastically and the dominant orientation of the polycrystalline part becomes the (111) orientation. The refractive index at 630 nm was found to be in the range between 1.91 and 1.95, having its maximum value for films deposited at $\text{450\hspace{0.17em}°}\mathrm{C}.$ Similar behavior was observed for the dielectric constant κ, measured from the high frequency capacitance measurements, with a maximum value of 15 obtained for the above mentioned deposition temperature as well. The average roughness of the films decreases with substrate temperature from $\text{∼30\hspace{0.17em}Å}$ to less than 5 Å in the range of temperatures studied.

Y 2 O 3 films were deposited on c-Si substrates at temperatures in the 400–550°C range, with no further thermal treatment given to these samples, using the spray pyrolysis technique. The spraying solution was yttrium acetilacetonate disolved N,N-dimethylformamide. In addition, a solution of H2O–NH4OH was sprayed in parallel during the deposition process to improve the optical, structural, and electrical properties of the deposited films. The growth of a SiO2 layer between the yttrium oxide and the Si substrate during this deposition process resulted in interface state density values as low as 1010eV−1cm−2. An effective refractive index value of 1.86, and deposition rates close to 1Å∕s were obtained. The Y2O3 films were polycrystalline with a crystalline cubic phase highly textured with the (400) direction normal to the Si surface. An effective dielectric constant up to 13, as well as a dielectric strength of the order of 0.2MV∕cm was obtained for ∼1000Å thick as-deposited films incorporated in a metal-oxide-semiconductor structure.