Density, thickness and composition measurements of TiO2SiO2 thin films by coupling X-ray reflectometry, ellipsometry and electron probe microanalysis-X

Mixed TiO₂SiO₂ thin films were deposited by aerosol atmospheric CVD method by using di-acetoxi di-butoxi silane (DADBS) and Ti tetra-butoxide as precursors. By varying the deposition temperatures between 470 and 600 °C and the ratios between the Si and Ti precursors (Si/Ti) from 2 up to 16, films with different compositions and thicknesses were deposited. The coupled analysis of the results of different characterisation methods was used in order to determine the variation of the composition, the thickness and the density of the films. First EPMA measurements were performed at different acceleration voltages with a Cameca SX50 system. By analysing, with specific software, the evolution of the intensity ratio I_x/I_std versus the voltage, the composition and the mass thickness (product of density by the thickness) were determined. In order to measure independently the density, X-ray reflectometry experiments were performed. By analysing the value of the critical angle and the Kiessig fringes, the density and the thickness of the layers were determined. The refractive index and the thickness of the films were also measured by ellipsometry. By assuming a linear interpolation between the index value of the pure SiO₂ and TiO₂ films, the film composition was deduced from the refractive index value. XPS measurements were also performed in order to obtain an independent value of the composition. A good agreement between the ways to measure the density is obtained.     

The determination of the refractive index and the thickness of thin films of aluminium oxide on aluminium by the polarimetric method

Formulas for the reflection of light from glass (i. e. a dielectric) coated with a thin non-metallic film are generalized for the case of the reflection of light from a metal coated with a thin non-metallic film, e. g. a film of aluminium oxide on aluminium. It is shown how the refractive index and the thickness of the aluminium oxide film on an aluminium mirror can be determined by measurements in polarized light. In conclusion the results of Drude's classical theory of thin non-metallic films on metallic mirrors are compared with the results obtained by the author on the basis of the interference of light in thin films.     

Complex study of titanium nano-films prepared by magnetron sputtering

The oxidation of Ti films with thickness from 5 to 100 nm was performed in air at room temperature. The thickness and roughness of metal and oxide layers were determined by neutron and X-ray reflectometry. The thin titanium films were found to be oxidized to a greater depth; than the thick ones. However the metal layer was found to exist even in the thinnest (5 nm) samples, as the direct measuring of electrical resistance of the films has confirmed. The optimal parameters of titanium films utilizable in polarizing coatings of neutron optics were estimated. The AFM data on the microrelief and the phase homogeneity of the Ti nano-film surface were obtained.     

Determination of Thickness and Optical Constants of ZnO Thin Films Prepared by Filtered Cathode Vacuum Arc Deposition

ZnO thin films are prepared on glass substrates by filtered cathode vacuum arc （FCVA） deposition technique. A new method is demonstrated to extract the refractive index, thickness and optical band gap of ZnO thin films from the transmission spectrum alone. The refractive index is calculated from the extremes of the interference fingers. The transmission spectrum is divided into two terms, non-interference term and interference effect term. The thickness of thin films is calculated by simulating the interference term, and the non-interference term is used to calculate optical band gap with the gained thickness. The results are compared with measurements by using an ellipsometry and a scanning electron microscope.     

Stability of thermoresponsive methylcellulose thin film: x‐ray reflectivity study

Methylcellulose (MC), a thermoreversible polymer, was fabricated as thin films into silicon substrates and characterized by x‐ray reflectivity (XRR) measurements for its stability with time and heating. XRR data from the as‐is thin films showed good agreement with the single‐layer model on top of a substrate from Parratt's formalism. Data fitting showed that the density of the thin films is slightly higher than the reported value by manufacturers. Interface roughness values indicate good wetting of the polymer onto the substrate. Heating the thin films at the phase transition temperatures and quenching them to room temperature showed no significant changes in the thin film parameters before and after heating. This showed the thermal stability and/or thermoreversibility of the film. Diffuse scattering measurements also showed no significant changes in the lateral structure of the film with heating and quenching. XRR measurements done on fabricated thin films stored for a month showed a slight increase in the film thickness which could be due to the hygroscopic nature of the polymer. Vacuum heating of the stored thin films at 100 °C for 1 h slightly decreased the thickness, but it has been found that other parameters such as density and surface/interface roughness show good thermal stability. Copyright © 2009 John Wiley & Sons, Ltd.     

Ultrathin multilayer of Fe and Ge: structure and magnetic properties

Metal-semiconductor multilayers are interesting, artificial structures as prospective candidates for spin injection devices. A Fe–Ge multilayer sample with very thin individual layers (few crystallographic planes) has been deposited by sputtering on Si[1 0 0] substrate. We have characterized the structure of this multilayer sample using X-ray diffraction, X-ray reflectometry and neutron reflectometry. The magnetic moment density in the ferromagnetic Fe layer has been obtained by polarized neutron reflectometry and the bulk magnetic behavior of the thin film by SQUID magnetometer measurements. We found that the film is a soft ferromagnet at room temperature with a substantially reduced magnetic moment of the Fe atoms.     

Structure-related infrared optical properties of BaTiO3 thin films grown on Pt/Ti/SiO2/Si substrates

BaTiO₃ thin films with different thickness have been grown on Pt/Ti/SiO₂/Si substrates by a modified sol-gel method. X-ray diffraction analyses show that the BaTiO₃ thin films are polycrystalline. The crystalline quality of the films is improved with increasing thickness. The infrared optical properties of the BaTiO₃ thin films have been investigated using an infrared spectroscopic ellipsometry in the wave number range of 800-4000 cm⁻¹ (2.5-12.5 μm). By fitting the measured pseudodielectric functions with a three-phase model (Air/BaTiO₃/Pt), and a derived classical dispersion relation for the thin films, the optical constants and thicknesses of the thin films have been simultaneously obtained. The refractive index of the BaTiO₃ thin films increases and on the other hand, the extinction coefficient does not change with increasing thickness in the entirely measured wave number range. The dependence of the refractive index on the film thickness has been discussed in detail and was mainly due to both the crystalline quality of the films and packing density. Finally, the absorption coefficient was calculated in the infrared region for applications in the pyroelectric IR detectors.     

Size effect in the spin glass magnetization of thin AuFe films as studied by polarized neutron reflectometry

We used polarized neutron reflectometry to determine the temperature dependence of the magnetization of thin AuFe films with 3% Fe concentration. We performed the measurements in a large magnetic field of 6 T in a temperature range from 295 to 2 K. For the films in the thickness range from 500 to 20 nm we observed a Brillouin-type behavior from 295 K down to 50 K and a constant magnetization of about 0.9 micro(B) per Fe atom below 30 K. However, for the 10 nm thick film we observed a Brillouin-type behavior down to 20 K and a constant magnetization of about 1.3 micro(B) per Fe atom below 20 K. These experiments are the first to show a finite-size effect in the magnetization of single spin-glass films in large magnetic fields. Furthermore, the ability to measure the deviation from the paramagnetic behavior enables us to prove the existence of the spin-glass state where other methods relying on a cusp-type behavior fail.     

Optical constants of nanofilms of J aggregates of organic dyes, measured by spectral ellipsometry and polarization reflectometry

The dispersion of the complex refractive index of thin films of J aggregates of organic dyes has been measured by spectral ellipsometry and polarization reflectometry. It is found that almost all films of J aggregates exhibit normal dispersion in the long-wavelength region, where the films are transparent. In the spectral range where the films absorb, anomalous dispersion is observed with a maximum in the J peak. The refractive index n in this range becomes as high as ?2.5–3.5. It is revealed that polarization reflectometry provides adequate accuracy in determining the optical constants n and κ of nanofilms of organic dyes.     

Strain relaxation and vacancy creation in thin platinum films

Synchrotron based combined in situ x-ray diffractometry and reflectometry is used to investigate the role of vacancies for the relaxation of residual stress in thin metallic Pt films. From the experimentally determined relative changes of the lattice parameter a and of the film thickness L the modification of vacancy concentration and residual strain was derived as a function of annealing time at 130 °C. The results indicate that relaxation of strain resulting from compressive stress is accompanied by the creation of vacancies at the free film surface. This proves experimentally the postulated dominant role of vacancies for stress relaxation in thin metal films close to room temperature.     

Laboratory LPP EUV reflectometer working with non-polarized radiation

A laboratory extreme ultraviolet reflectometer (EUVR) for the wavelength range from 10 to 16 nm was built at IWS Dresden using a gold target laser pulse plasma (Au-LPP) source. The peak reflectance and the center wavelength are reproduced in relative standard deviation of 0.2 and 0.02%, respectively. In contrast to measurements using linearly polarized s-adjusted synchrotron radiation at PTB, measurements with non-polarized radiation at the EUVR yield systematically lower values for the reflectance due to the smaller reflectance of the p-component at higher angles of incidence.     

Magnetic depth profiling of Fe/Au multilayer using neutron reflectometry

We present unpolarized and polarized neutron reflectometry data on Fe/Au multilayer sample for characterizing the layer structure and magnetic moment density profile. Fe/Au multilayer shows strong spin-dependent scattering at interfaces, making it a prospective GMR material. Fe/Au multilayer with bilayer thickness of 130 Å was grown on Si substrate by RF magnetron sputtering technique. Unpolarized neutron reflectivity measurement yields nuclear scattering length density profile. The magnetic scattering length density profile has been obtained from polarized neutron reflectivity measurements.     

Polarized neutron reflectometry at Dhruva reactor

Polarized neutron reflectometry (PNR) is an ideal non-destructive tool for chemical and magnetic characterization of thin films and multilayers. We have installed a position sensitive detector-based polarized neutron reflectometer at Dhruva reactor, Trombay. In this paper we will discuss the results obtained from this instrument for two multilayer samples. The first sample is a (Ni-Mo alloy)/Ti multilayer sample. We have determined the chemical structure of this multilayer by unpolarized neutron reflectometry (NR). The other sample is a Fe/Ge multilayer sample for which we obtained the chemical structure by NR and magnetic moment per Fe atom by PNR.     

镧掺杂BaSnO3薄膜的电学和光学特性

利用射频磁控溅射法在(LaAlO₃)_0.3(SrAl_0.5Ta_0.5O₃)_0.7 (001)单晶基底上生长了镧掺杂BaSnO₃外延薄膜. 通过Hall效应和热电势测量证实了镧掺杂BaSnO₃薄膜具有n型简并半导体特征, 并且基于载流子浓度和Seebeck系数计算出电子的有效质量为0.31m₀ (m₀为自由电子质量). 镧掺杂BaSnO₃薄膜在可见波段具有良好的透明性(透过率大于73%). 基于介电模型对薄膜的透过率曲线进行拟合, 从拟合结果中不仅得到了薄膜的厚度为781.2 nm, 能带宽度为3.43 eV、 带尾宽度为0.27 eV和复光学介电常数随波长的变化规律, 而且也强力地支持了基于电学参数计算电子有效质量的正确性.     

In Situ Characterisation of Polymer Surfaces and Thin Organic Films in Plasma Processing

In situ sampling techniques are presented for investigation of plasma surface modification of polymers and plasma polymerisation. FTIR spectroscopy (infrared absorption reflection spectroscopy - IRRAS, and attenuated total reflection - ATR) are properly used for characterisation of the changes in the molecular structure of thin polymer films (polystyrene, polyethylene) due to low pressure plasma treatment. The thin films were prepared by dip or spin coating procedures. In the case of plasma polymerisation a novel fibre-ATR technique is applied to investigate the plasma polymerisation process in the plasma bulk. Results are exemplary shown for plasma polymerisation of styrene. Ellipsometric measurements allowed the characterisation of the thin plasma modified top polymer surface layer or thin deposited plasma polymer films by their refractive index and thickness. It was shown that the applied surface plasmon ellipsometry is very sensitive with respect to the usual ellipsometry for investigation of polymer surface modification. The in situ microgravimetry by means of electronic vacuum microbalance permitted to measure the change of the sample mass in the order of 1 μg during the plasma treatment. The first steps in plasma modification (concurrence between the incorporation of plasma particles and the material etching) were studied.     

Hydrophilicity of amorphous TiO2 ultra-thin films

The UV-light-induced hydrophilicity of amorphous titanium dioxide thin films obtained by radio frequency magnetron sputtering deposition was studied in relation with film thickness. The effect of UV light irradiation on the film hydrophilicity was fast, strong and did not depend on substrate or thickness for films thicker than a threshold value of about 12 nm, while for thinner films it was weak and dependent on substrate or thickness. The weak effect of UV light irradiation observed for the ultra-thin films (with thickness less than 12 nm) is explained based on results of measurements of surface topography, UV-light absorption and photocurrent decay in vacuum. Comparing to thicker films, the ultra-thin films have a smoother surface, which diminish their real surface area and density of defects, absorb partially the incident UV light radiation, and exhibit a longer decay time of the photocurrent in vacuum, which proves a spatial charge separation. All these effects may contribute to a low UV light irradiation effect on the ultra-thin film hydrophilicity.     

Ion beam sputter deposition of TiO<Subscript>2</Subscript> films using oxygen ions

TiO₂ thin films were grown by ion beam sputter deposition (IBSD) using oxygen ions, with the ion energy and geometrical parameters (ion incidence angle, polar emission angle, and scattering angle) being varied systematically. Metallic Ti and ceramic TiO₂ served as target materials. The thin films were characterized concerning thickness, growth rate, surface topography, structural properties, mass density, and optical properties. It was found that the scattering geometry has the main impact on the film properties. Target material, ion energy, and ion incidence angle have only a marginal influence. Former studies on reactive IBSD of TiO₂ using Ar and Xe ions reported equivalent patterns. Nevertheless, the respective ion species distinctively affects the film properties. For instance, mass density and the refractive index of the TiO₂ thin films are remarkably lower for sputtering with oxygen ions than for sputtering with Ar or Xe ions. The variations in the thin film properties are tentatively attributed to the angular and the energy distribution of the film-forming particles, especially, to those of the backscattered primary particles.     

Mass-limited Sn target irradiated by dual laser pulses for an extreme ultraviolet lithography source

A thin Sn film was investigated as a mass-limited target for an extreme ultraviolet (EUV) lithography source. It was found that those energetic ions that are intrinsic with the mass-limited Sn target could be efficiently mitigated by introducing a low-energy prepulse. High in-band conversion efficiency from a laser to 13.5 nm EUV light could be obtained using an Sn film with a thickness down to 30 nm when irradiated by dual laser pulses. It was shown that the combination of dual pulse and inert Ar gas could fully mitigate ions with a low ambient pressure nearly without the penalty of the absorption of the EUV light.