Nataliya Nabatova-Gabain

Preparation and characterization of polycrystalline anatase and rutile TiO2 thin films by rf magnetron sputtering

Titanium dioxide films with the anatase and rutile single phase were formed on Si substrates by rf sputtering through a precise control of critical parameters. The structure of the films was studied by X-ray diffraction (XRD) and transmission electron microscopy (TEM), and the optical properties were evaluated with spectroscopic ellipsometry (SE). Lattice distortion was found in both anatase and rutile films from TEM observation. The obtained refractive indices n exhibit higher values than those reported for thin films due presumably to the density structure of the sputtered films. Optical band gaps were calculated by Tauc plot using the obtained extinction coefficient separately for anatase and rutile, with values larger than those reported for bulk materials. The reasons for the larger band gap might be due to the strain from lattice distortion.

Simultaneous epitaxial growth of anatase and rutile TiO2 thin films by RF helicon magnetron sputtering

Epitaxial films of TiO2 with rutile structure on sapphire and anatase structure on SrTiO3 were simultaneously grown by RF helicon magnetron sputtering of a TiO2 target in Ar atmosphere. X-ray diffraction using y � 2y scan and pole figure plots confirmed the epitaxial relationship, which were rutile (1 0 1)Jsapphire (1 1 0), (0 1 0)fJ(0 0 1)s, and anatase (0 0 1)JSrTiO3(0 0 1), (1 0 0)fJ(1 0 0)s, where suffix f and s stand for the film and substrate, respectively. Moreover, observation by transmission electron microscopy identified the epitaxial film growth of single crystalline anatase and rutile structure with slight lattice distortion compared with bulk. The lattice constants of a and b; which were calculated from electron diffraction spots and lattice image in TEM of the films were contracted while that of c beingexpanded. Accordingto the results of spectroscopic ellipsometry, the films show very hig h refractive indices ( n) at the designated wavelength range in comparison with the past reports on TiO2 thin films. Although there are no bulk references in the anatase case, the values n of the rutile film are comparable to the bulk in the data-book. Such high refractive indices of the films indicate the compact texture of the epitaxial films fabricated by helicon sputtering. r 2003 Elsevier Science B.V. All rights reserved.

Spectroscopic Ellipsometry of Yttrium–Iron Garnet Thin Films Containing Gold Nanoparticles

We report complex dielectric function (e) for yttrium–iron garnet thin films containing Au nanoparticles. Films are prepared using a co-sputtering method with post-annealing. Real and imaginary parts of e of the films are obtained using spectroscopic ellipsometry in a photon energy region from near-infrared to ultra-violet. An anomalous dispersion of Re[e] in the visible region originating from localized surface plasmon of Au nanoparticles is clearly observed. The influence of e on the magneto-optical Kerr properties of the nanocomposite films is discussed.

Moisture barrier properties of single-layer graphene deposited on Cu films for Cu metallization

The moisture barrier properties of large-grain single-layer graphene (SLG) deposited on a Cu(111)/sapphire substrate are demonstrated by comparing with the bare Cu(111) surface under an accelerated degradation test (ADT) at 85 °C and 85% relative humidity (RH) for various durations. The change in surface color and the formation of Cu oxide are investigated by optical microscopy (OM) and X-ray photoelectron spectroscopy (XPS), respectively. First-principle simulation is performed to understand the mechanisms underlying the barrier properties of SLG against O diffusion. The correlation between Cu oxide thickness and SLG quality are also analyzed by spectroscopic ellipsometry (SE) measured on a non-uniform SLG film. SLG with large grains shows high performance in preventing the Cu oxidation due to moisture during ADT.

Emission decay rate of a light emitter on thin metal films

We theoretically study the emission decay rate of a light emitter on thin Au films based on a semiclassical point-dipole model. The complex dielectric functions of Au films determined by spectroscopic ellipsometry are used in this calculation model. We investigate the dependences of the decay rate on the metal thickness, distance between emitter and metal, and emitted-light wavelength. It is found that the decay rate shows a peak at the surface plasmon resonance wavelength. It is also shown that its peak wavelength, width, and peak value are strongly dependent on the Au layer thickness. The peak value in the decay rate versus wavelength curves for the Au film of 10 nm thickness is also found to be higher than for the bulk Au metal. These results are due to the metal-thickness-dependent plasmon effects on the emission decay rates.