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Recently ferroelectric properties have been found in hafnia-based nanosized films. Such films are of the utmost interest for development of a universal memory, which combines the advantages of random access memory and flash memory. The paper studies optical properties of hafnia-zirconium oxide films H-fxZryO2 and lanthanum-alloyed hafnia-zirconium oxide films La:HfxZryO2. Fluctuations of thickness in HfxZryO2 do not exceed 3.5%, fluctuations of thickness in La:HfxZryO2 films—3.2%. Optical properties are analyzed based on effective-medium theory. According to effective-medium theory data, HfxZryO2 films contain 46% HfO2, 54% ZrO2, La:HfxZryO2 films contain 47.5% HfO2, 52.4% ZrO2, 2.5% La2O3. [ABSTRACT FROM AUTHOR]

The luminescent and optical properties of materials based on zirconium(IV) oxide grown by crystallization of ZrO2 melts with 0, 2.0, 2.5, 2.8, and 3.7 mol % of Y2O3 are studied. Using Raman spectroscopy, it is found that this material with the Y2O3 concentration below 2 mol % is mainly a monoclinic ZrO2 phase. The photoluminescence spectra of these crystals contain a blue–green band peaking at an energy of 2.4 eV. This fact in combination with the specific features of the refractive index and absorption coefficient dispersions indicates the presence of high concentrations of oxygen vacancies and polyvacancies in the samples. At higher concentrations of Y2O3 in the mixture, the tetragonal ZrO2 modification becomes dominant in the materials under study and the blue–green luminescence intensity decreases. The experimental optical spectra are analyzed in comparison with the ab initio calculated spectra for ideal ZrO2 crystals in the cubic, tetragonal, and monoclinic phases. [ABSTRACT FROM AUTHOR]

The optical properties and composition of thermal silicon oxide thin films processed in a hydrogen electron cyclotron resonance plasma have been studied by ellipsometry, quantum-chemical modeling, and photoluminescence spectroscopy. It has been found that the plasma processing of the films leads to their oxygen depletion and the formation of nonstoichiometric oxide SiOx< 2. The parameter x of the obtained SiOx films has been determined by comparing the experimental spectral dependence of the refractive index with the dependence obtained theoretically using the ab initio calculation. It is shown that an increase in the time of processing of thermal dioxide SiO2 in a hydrogen plasma leads to an increase in the refractive index of the film, as well as in the degree of its oxygen depletion. The dependence of the parameter x of the investigated films on the hydrogen plasma processing time is plotted. [ABSTRACT FROM AUTHOR]

Abstract: The optical properties of thin films based on unsubstituted and tetrafluoro-substituted zinc phthalocyanines synthesized by physical vapor deposition are studied within the wavelength range of 250-1000 nm. Spectroscopic ellipsometry shows that films based on zinc phthalocyanines have uniform thicknesses and optical parameters, strongly absorb visible light, and have characteristic absorption peaks corresponding to electronic transitions in the system of conjugated double bonds of phthalocyanine rings. Introduction of fluorine substituents into peripheral positions of the zinc phthalocyanine molecule leads to an increase in light absorption and a shift of the main absorption maximum to longer wavelengths (bathochromic shift). The absorption spectra are described using the Lorentz-Drude dispersion model. It is shown that the films based on a mixture of phthalocyanines can be well described using the Bruggeman effective medium model. [ABSTRACT FROM AUTHOR]

Optical properties of amorphous nonstoichiometric tantalum-oxide films of variable composition (TaOx, x = 1.94-2.51) in the spectral range of 1.12-4.96 eV, obtained by ion-beam sputtering-deposition of metallic tantalum at different partial oxygen pressures (0.53-9.09 × 10-3 Pa), have been investigated. It is shown by spectral ellipsometry that the character of dispersion of the absorption coefficient and refractive index in TaOx of variable composition suggests that light-absorbing films with dispersion similar to that in metals are formed at oxygen pressures in the growth chamber below 2.21 × 10-3 Pa, whereas transparent films with dielectric dispersion are formed at pressures above 2.81 × 10-3 Pa. According to the data of quantumchemical simulation, the absorption peak at a photon energy of 4.6 eV in TaOx observed in the absorptioncoefficient dispersion spectrum is due to oxygen vacancy. The peak in the Raman-scattering spectra of TaOx films with metallic dispersion at frequencies of 200-230 cm-1 is presumably related to tantalum nanoclusters. [ABSTRACT FROM AUTHOR]

Lanthanum oxide (La2O3) films were grown by the reactive dc magnetron sputtering and studied their structural, chemical and optical parameters. La2O3 films were deposited onto Si substrates by sputtering La-metal in a reactive gas (Ar+O2) mixture at a substrate temperature of 200 °C. Reflection high-energy electron diffraction measurements confirm the amorphous state of La2O3 films. Chemical analysis of the top-surface layers evaluated with x-ray photoelectron spectroscopy indicates the presence of a layer modified by hydroxylation due to interaction with atmosphere. Optical parameters of a-La2O3 were determined with spectroscopic ellipsometry (SE). There is no optical absorption over spectral range λ=250-1100 nm. Dispersion of refractive index of a-La2O3 was defined by fitting of SE parameters over λ=250-1100 nm. [ABSTRACT FROM AUTHOR]

Optical characteristics of the HfO2 − xN x and TiO2 − xN x films obtained by reactive ion beam sputtering have been investigated by spectral ellipsometry. The chemical composition of the films was determined using X-ray photoelectron spectroscopy. The nitrogen content in the oxynitride films (determined by the N2/O2 ratio in the gas mixture during synthesis) reached ≈9 at % for TiO2 − xN x and ≈ 6 at % for HfO2 − xN x. It is found that the dispersion relations n(λ) and k(λ) for the TiO2 − xN x films change from those characteristic of titanium dioxide to those typical of titanium nitride with an increase in the nitrogen content from 0 to ≈9 at %. The optical parameters of the HfO2 − xN x films depend weakly on the nitrogen content in the range 0–6 at %. [ABSTRACT FROM AUTHOR]

The optical properties, interface structure, and thermal stability of the ZrO2 films grown on Si(100) were investigated in detail. A 2 nm thick interfacial layer (IL) is formed at the ZrO2–Si interface for the as-grown ZrO2. The optical constants of ZrO2 films and IL correspond to amorphous-ZrO2 and amorphous-SiO2, respectively. The oxidation and IL growth at 900 °C, as a function of annealing time, exhibit a two-step behavior with a slow and a fast growth-rate zones. The transition from a zone of slow to fast rate is attributed to structurally modified ZrO2 facilitating the faster oxygen transport to the ZrO2/Si interface. [ABSTRACT FROM AUTHOR]