Search

The optical properties of nitrogen-doped SnO2 films with different N2/(N2+O2) gas ratios grown by reactive sputtering were studied by spectroscopy ellipsometry. The optical dielectric functions of the films were simulated by the Tauc-Lorentz model. It was found that the refractive index and extinction coefficient of nitrogen-doped SnO2 films increase and the band gap has a redshift with the increase of the N2 ratios. The general influences of the electronegativity and bond ionicity on the band gap, the refractive index in the spectral region below the fundamental absorption edge of nitrogen-doped SnO2, and other doped semiconductors are demonstrated. [ABSTRACT FROM AUTHOR]

The microstructure and optical properties of MgO–TiO2 composite thin films prepared by radio frequency magnetron sputtering were studied. The composite films have an amorphous structure and the growth rate of the composite film increases with increasing Mg content. The refractive index almost linearly decreases with increasing Mg content in the composite films at wavelength larger than 300 nm and can be adjusted in the wide range between the refractive index of TiO2 and that of MgO. The extinction coefficient decreases with Mg content and is nearly zero at visible light region. The optical band gap of the composite films determined from the absorption spectra increases with Mg content, and has a good agreement with that obtained from spectroscopic ellipsometry simulation. A broad photoluminescence band in the visible region was observed in the composite films with high Mg content and was considered resulted from the oxygen vacancies. [ABSTRACT FROM AUTHOR]

The influence of annealing on the morphological, structural, and optical properties of ZnO:Tb thin films on Si substrate grown by magnetron cosputtering is investigated. It has been found that the ZnO:Tb thin films with structures of tetrapod and screwlike nanorod are formed after annealing at temperature of 950 °C. X-ray photoelectron spectroscopy, energy dispersive spectroscopy, and Raman analyses prove that the tetrapod-aiguille zinc oxide (T-A-ZnO) and the screwlike nanorods are composed of Zn, Tb, and O elements. The photoluminescence spectra of the ZnO:Tb thin films with the T-A-ZnO structure and the screwlike nanorods are featured with two ultraviolet emission peaks and one strong green emission band, and the photoluminescence intensity increases with increasing annealing temperature. The surface defects in the T-A-ZnO structure and the screwlike nanorods are considered to be responsible for enhanced green emission in the annealed ZnO:Tb thin films. [ABSTRACT FROM AUTHOR]

The Fuping Complex is one of the important basement terranes within the central segment of the Trans-North China Orogen (TNCO) where mafic granulites are exposed as boudins within tonalite-trondhjemite-granodiorite ( TTG) gneisses. Garnet in these granulites shows compositional zoning with homogeneous cores formed in the peak metamorphic stage, surrounded by thin rims with an increase in almandine and decrease in grossular contents suggesting retrograde decompression and cooling. Petrological and phase equilibria studies including pseudosection calculation using thermocalc define a clockwise P-T path. The peak mineral assemblages comprise garnet+clinopyroxene+amphibole+quartz+plagioclase+K-feldspar+ilmenite±orthopyroxene±magnetite, with metamorphic P-T conditions estimated at 8.2-9.2 kbar, 870-882 °C (15 FP-02), 9.6-11.3 kbar, 855-870 °C (15 FP-03) and 9.7-10.5 kbar, 880-900 °C (15 FP-06) respectively. The pseudosections for the subsequent retrograde stages based on relatively higher H2O contents from P/T-M(H2O) diagrams define the retrograde P-T conditions of <6.1 kbar, <795 °C (15 FP-02), 5.6-5.8 kbar, <795 °C (15 FP-03), and <9 kbar, <865 °C (15 FP-06) respectively. Data from LA- ICP- MS zircon U-Pb dating show that the mafic dyke protoliths of the granulite were emplaced at c. 2327 Ma. The metamorphic zircon shows two groups of ages at 1.96-1.90 Ga (peak at 1.93-1.92 Ga) and 1.89-1.80 Ga (peak at 1.86-1.83 Ga), consistent with the two metamorphic events widely reported from different segments of the TNCO. The 1.93-1.92 Ga ages are considered to date the peak granulite facies metamorphism, whereas the 1.86-1.83 Ga ages are correlated with the retrograde event. Thus, the collisional assembly of the major crustal blocks in the North China Craton (NCC) might have occurred during 1.93-1.90 Ga, marking the final cratonization of the NCC. [ABSTRACT FROM AUTHOR]

Nanocrystalline compound thin films of ZnO-TiO2 with different Zn/Ti atomic ratios were prepared by radio frequency magnetron reactive sputtering. The optical constants and the optical band gap were investigated using spectroscopic ellipsometry and the optical absorption spectrum. It was found that the cubic ZnTiO3 phase can be obtained with the atomic ratio of Zn to Ti of about 1:1, and transforms to rhombohedral ZnTiO3 phase and a phase mixture of rhombohedral ZnTiO3 and ZnO with increasing Zn content. The refractive index decreases with the increase of Zn content, and the extinction coefficient in the visible range is near zero. The optical band gap was derived from the modeling of ellipsometry data and extinction coefficient spectra, and compared with that obtained from optical absorption spectrum, and it was found that the optical band gaps obtained by these three methods are consistent with each other. [ABSTRACT FROM AUTHOR]

Nitrogen-incorporated SnO2 thin films have been grown on Si(100) and quartz substrates by reactive sputtering of a Sn target in gas mixtures of N2–O2. The structure of the nitrogen-incorporated SnO2 thin films was studied by X-ray diffraction, and the changes in the chemical bonds and atomic binding states of the nitrogen-incorporated SnO2 thin films were analyzed by X-ray photoelectron spectroscopy. It was found that the binding energy of Sn 3d and O 1s shifts 0.65 eV and 0.35 eV, respectively, toward the lower-energy side after nitrogen was incorporated into the SnO2 thin films as a comparison with that of pure SnO2 film. The indirect optical band gap gradually decreases from 3.42 eV to 3.23 eV, i.e. from the UV to the edge of the visible-light range, with increasing nitrogen flux content in the N2–O2 gas mixtures. [ABSTRACT FROM AUTHOR]

We study the optical properties of amorphous GaAs1-xNx films grown by radio frequency magnetron sputtering method with different N2 partial pressures. The surface morphology, the optical absorption, the Raman spectra, and optical constants of the films with different N2 partial pressures are reported. The appearance of the Raman peak at 245 cm-1 of “GaAslike” and a shoulder at about 750 cm-1 related to GaN indicates the formation of GaN clusters in GaAs matrix. The roughness decreases and the optical band gap of amorphous GaAs1-xNx films moves to short wavelength with increasing N2 partial pressure. The refractive index and the extinction coefficient of the films decrease with increasing N2 partial pressure, and it has been found that the amorphous GaAs1-xNx films with nonzero N2 partial pressure are transparent in red and near infrared wavelength regions. [ABSTRACT FROM AUTHOR]

Photoluminescence (PL) properties of ZnO thin films on Si substrate with and without an indium tin oxide (ITO) buffer layer, prepared under different oxygen partial pressures in the sputtering gas, were studied. It was found that PL characteristics of ZnO thin films depend on oxygen partial pressure and substrate, and the PL peak in the ultraviolet region has a strong red-shift with increasing excitation intensity on the glass and Si substrates with the ITO buffer layer, and the PL intensity increases with the increasing measuring cycle. Enhanced luminescence efficiency of ZnO thin films on the substrates with ITO buffer layer measured at different cycles can be obtained by thermal annealing. [ABSTRACT FROM AUTHOR]

The photoluminescence properties of nitrogen-incorporated SnO2 thin films on Si (100) substrates deposited by reactive magnetron sputtering have been studied. A strong photoluminescence band centered at 3.696 eV with full width at half maximum of 0.2 eV has been observed at room temperature. The peak position of the emission shifts to higher energy with increasing excitation intensity or decreasing temperature. The emission is considered due to the localized exciton recombination, and the observed exciton localization and band-tail states are believed to originate from the potential fluctuation induced by spatial distribution fluctuations of nitrogen concentration and/or grain boundary defects in the nanocrystalline film. [ABSTRACT FROM AUTHOR]

The optical properties of δ-Bi2O3 thin films were investigated using spectroscopic ellipsometry and optical absorption spectrum. δ-Bi2O3 thin films were grown on Si and quartz substrates under different oxygen flow ratios (OFR) by radio frequency reactive magnetron sputtering. The Tauc-Lorentz dispersion method was adopted to model the optical dispersion functions of the thin films. The optical bandgap was obtained by three different methods. It was found that refractive index and extinction coefficient decrease, and the optical bandgap has a slight blue shift with increasing the OFR. Factors influencing the optical constants and optical bandgap are discussed. [ABSTRACT FROM AUTHOR]