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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]

Nonstoichiometric silicon oxide SiOx is a promising material for developing a new generation of high-speed, reliable flash memory based on the resistive effect. It is necessary to understand the electron transport mechanism of the high-resistive state in SiOx to develop a resistive memory element. At present, it is generally accepted that the charge transport of the high-resistive state in the Resistive Random Access Memory (RRAM) is described by the Frenkel effect. In our work, the charge transport of the high-resistive state in RRAM based on SiOx is analyzed with two contact-limited and five volume-limited charge transport models. It is established that the Schottky effect model, thermally assisted tunneling, the Frenkel model of Coulomb trap ionization, the Makram-Ebeid and Lannoo model of multiphonon isolated trap ionization, and the Nasyrov-Gritsenko model of phonon-assisted tunneling between traps, quantitatively, do not describe the charge transport of the high-resistive state in the RRAM based on SiOx. The Shklovskii-Efros percolation model gives a consistent explanation for the charge transport of the high-resistive state in the RRAM based on SiOx at temperatures above room temperature. [ABSTRACT FROM AUTHOR]

Nonstoichiometric silicon oxide SiOx is a promising material for developing a new generation of high-speed, reliable flash memory based on the resistive effect. It is necessary to understand the electron transport mechanism of the high-resistive state in SiOx to develop a resistive memory element. At present, it is generally accepted that the charge transport of the high-resistive state in the Resistive Random Access Memory (RRAM) is described by the Frenkel effect. In our work, the charge transport of the high-resistive state in RRAM based on SiOx is analyzed with two contact-limited and five volume-limited charge transport models. It is established that the Schottky effect model, thermally assisted tunneling, the Frenkel model of Coulomb trap ionization, the Makram-Ebeid and Lannoo model of multiphonon isolated trap ionization, and the Nasyrov-Gritsenko model of phonon-assisted tunneling between traps, quantitatively, do not describe the charge transport of the high-resistive state in the RRAM based on SiOx. The Shklovskii-Efros percolation model gives a consistent explanation for the charge transport of the high-resistive state in the RRAM based on SiOx at temperatures above room temperature. [ABSTRACT FROM AUTHOR]

The optical quality HfxTi1−xO2 films with a wide range of the Hf/Ti ratio were prepared on Si (100) substrates by the ALD method with the use of tetrakis(ethylmethylamido)hafnium(IV) (Hf(NC2H5CH3)4, TEMAH) and titanium(IV) chloride TiCl4 as Hf and Ti precursors, respectively. The H2O vapor was applied as oxygen source. The structural properties of the as-deposited and annealed films were evaluated by the XRD analysis. The Hf/Ti ratio in the films was measured by energy dispersive spectroscopy and X-ray photoelectron spectroscopy. The dispersive optical constants were obtained by spectroscopic ellipsometry over the photon energy range of E = 1.12-4.96 eV. The specific growth kinetics is observed for 0 < x < 1. The optical constants wide-range tuning is reached in the HfxTi1−xO2 (x = 0-1) films via the chemical composition variation and annealing. [ABSTRACT FROM AUTHOR]

The atomic and electronic structures of metal-rich noncentrosymmetric zirconium oxide synthesized by the ion beam sputtering of a metallic target in an oxygen atmosphere has been studied by X-ray photoelectron spectroscopy, Raman scattering, spectral ellipsometry, and quantum-chemical simulation. It has been established that ZrOx < 2 consists of ZrO2, metallic Zr, and zirconium suboxides ZrOy. The stoichiometry parameter of ZrOy has been estimated. It has been shown that the optical properties of ZrOx < 2 are determined by metallic Zr. A model of fluctuation of the width of the band gap and a potential for electrons and holes in ZrOx < 2 based on spatial fluctuations of the chemical composition has been proposed. [ABSTRACT FROM AUTHOR]

The atomic and electronic structures of metal-rich noncentrosymmetric zirconium oxide synthesized by the ion beam sputtering of a metallic target in an oxygen atmosphere has been studied by X-ray photoelectron spectroscopy, Raman scattering, spectral ellipsometry, and quantum-chemical simulation. It has been established that ZrOx < 2 consists of ZrO2, metallic Zr, and zirconium suboxides ZrOy. The stoichiometry parameter of ZrOy has been estimated. It has been shown that the optical properties of ZrOx < 2 are determined by metallic Zr. A model of fluctuation of the width of the band gap and a potential for electrons and holes in ZrOx < 2 based on spatial fluctuations of the chemical composition has been proposed. [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]

The microstructures of amorphous and polycrystalline ferroelectric Hf0.5Zr0.5O2 films are studied by X-ray spectroscopy and ellipsometry. EXAFS spectra demonstrate that the amorphous film consists of an “incompletely mixed” solid solution of metallic oxides HfO2 and ZrO2. After rapid thermal annealing, the mixed Hf0.5Zr0.5O2 oxide films have a more ordered polycrystalline structure, and individual Hf and Zr monoxide islands are formed in the films. These islands are several nanometers in size and have a structure that is similar to the monoclinic structure of HfO2 and ZrO2. The presence of the HfO2 and ZrO2 phases in the Hf0.5Zr0.5O2 films is also detected by ellipsometry. [ABSTRACT FROM AUTHOR]