Synchrotron study of laser-thermally oxidized thin titanium films

The features of oxidation of thin titanium films on single-crystal silicon have been investigated and the character and mechanism of the action of mid-IR laser radiation on the oxidation of these films in the temperature range 400–500°C have been established. The effects of “laser acceleration” and “laser breaking” of the oxide film growth are revealed. X-ray diffraction data and X-ray absorption near-edge structure spectra of the grown oxides are reported and the change in the phase composition of the oxide films is explained by resonant absorption of laser radiation.     

Laser assisted modification and chemical metallization of electron-beam deposited ceria thin films

Excimer laser processing is applied for tailoring the surface morphology and phase composition of CeO₂ ceramic thin films. E-beam evaporation technique is used to deposit samples on stainless steel and silicate glass substrates. The films are then irradiated with ArF* excimer laser pulses under different exposure conditions. Scanning electron microscopy, optical spectrophotometry, X-ray diffractometry and EDS microanalysis are used to characterize the non-irradiated and laser-processed films. Upon UV laser exposure there is large increase of the surface roughness that is accompanied by photo-darkening and ceria reduction. It is shown that the laser induced changes in the CeO₂ films facilitate the deposition of metal nano-aggregates in a commercial copper electroless plating bath. The significance of laser modification as a novel approach for the production of CeO₂ based thin film catalysts is discussed.     

Nano-ionic thin films of gadolinia-doped ceria prepared by pulsed laser ablation

Microstructural properties of nano-ionic thin films of gadolinia-doped ceria (GDC) prepared by pulsed laser ablation from sintered targets of gadolinia (5–20 mol%) doped ceria are investigated. The ionic conductivity measurements of the sintered pellets showed a decrease in the activation energy from 1.1 to 0.65 eV for 5 and 30 mol% gadolinia-doped ceria, respectively. The microstructural properties of the GDC films as a function of substrate temperature, oxygen partial pressure, and laser energy show that the films are polycrystalline in the entire range of substrate temperature. The grain size is found to increase with increasing temperature up to 873 K. Further improved crystallinity is noticed for the films grown with oxygen partial pressure of 0.1–0.2 mbar. X-ray diffraction and transmission electron microscopy (TEM) reveal nanocrystalline grains with textured growth along <111> orientation in these films at low substrate temperature and at lower oxygen partial pressure. TEM study shows a uniform distribution of nanocrystal of 8–10 nm for energies ≤200 mJ/pulse, and nanocrystals embedded in a large crystalline matrix of doped ceria for energies in the range 400–600 mJ/pulse. Raman spectroscopy also confirms the defects in these films. The study also reveals that the substrate temperature and oxygen partial pressure could influence preferred orientation, while the laser energy could significantly influence defect concentration in these films. Invited paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7–9, 2006.     

Thermal decomposition of nickel carbide thin films

Thin films of nickel carbide are produced by evaporating fourteen atomic layers (1.8 × 10¹⁶ atoms cm^?2) of nickel onto the (0001) surface of graphite at room temperature. The presence of nickel carbide is indicated by the characteristic carbide Auger electron signal. LEED shows that no ordered structural change takes place on the graphite (0001) surface when nickel carbide is produced in this manner. Isothermal heating of the sample leads to an irreversible change of the carbon Auger signal. The times required for this change range from 150 min at 150°C to 45 min at 185°C. The times required for decomposition yield an activation energy for decomposition equal to 50 kJ mole^?1. The decomposition of nickel carbide thin films obeys zero order kinetics. Depth profiling of the film after decomposition reveals that the observed decomposition is limited only to the top two or three atomic layers.     

Optical and electrical properties of thermally oxidized bismuth thin films

Bismuth trioxide (Bi₂O₃) thin films were prepared by dry thermal oxidation of metallic bismuth films deposited by vacuum evaporation. The oxidation process of Bi films consists of a heating from the room temperature to an oxidation temperature (T_o = 673 K), with a temperature rate of 8 K/min; an annealing for 1 h at oxidation temperature and, finally, a cooling to room temperature. The optical transmission and reflection spectra of the films were studied in spectral domains ranged between 300 nm and 1700 nm, for the transmission coefficient, and between 380 nm and 1050 nm for the reflection coefficient, respectively. The thin-film surface structures of the metal/oxide/metal type were used for the study of the static current-voltage (I-U) characteristics. The temperature of the substrate during bismuth deposition strongly influences both the optical and the electrical properties of the oxidized films. For lower values of intensity of electric field (ξ < 5 × 10⁴V/cm), I-U characteristics are ohmic.     

Study of Fe-Al thin films oxidized at room temperature

Very thin films of Fe andFe/Al were oxidized at room temperature in dry air andthen studied by means of surface Mössbauer measurements andX-ray photoelectron spectroscopy. A mechanism is proposed for the oxidation process.     

CEMS spectra of non-spherical nanoparticles in oxidized iron thin films

The polycrystalline stannide SmRhSn was prepared by arc melting of the elements in an argon atmosphere. The title compound crystallizes with the ZrNiAl type structure (space group $P\bar{6}2m)$ with the lattice parameters: a?= 739.6(1) and c?= 406.9(1) pm. The magnetic and electronic properties of SmRhSn were investigated in detail by magnetic susceptibility measurements and ¹¹⁹Sn Mössbauer spectroscopy. A transition from a paramagnetic to a ferromagnetic state was determined to be T _C?= 14.5(1) K. The ¹¹⁹Sn Mössbauer spectrum recorded in T?= 4.2 K was fitted using single component, but with a broad quasi-distribution of magnetic hyperfine fields.     

Epitaxial growth of atomically flat gadolinia-doped ceria thin films by pulsed laser deposition

Epitaxial growth of Ce_0.8Gd_0.2O₂(CGO) films on (001) TiO₂-terminated SrTiO₃ substrates by pulsed laser deposition was investigated using in situ reflective high energy electron diffraction. The initial film growth shows a Stransky–Krastanov growth mode. However, this three-dimensional island formation is replaced by a two-dimensional island nucleation during further deposition, which results in atomically smooth CGO films. The obtained high-quality CGO films may be attractive for the electrolyte of solid-oxide fuel cells operating at low temperature.     

Optical properties and adhesion of air oxidized vacuum evaporated bismuth thin films

Highly adhesive bismuth oxide thin films on glass have been prepared by air oxidation of vacuum evaporated bismuth thin films at various temperatures. The transmittance, optical band gap, refractive index and adhesion show temperature and oxidation time effects. The films show a direct band gap between 2 and 2.5 eV. The refractive indices are in the range 1.854-1.991. The transmittances of the bismuth oxide films are quite high in a large wavelength range. These bismuth oxide films can have potential use in optical waveguides.     

Electrochemical synthesis and STM-STS studies of thin diamond-like films on the surface of oxidized aluminum

Thin carbon films on the surface of aluminum containing native oxide were prepared at room temperature by electrochemical deposition from a solution of lithium acetylenide in dimethylsulfoxide. The structure of the coatings obtained was studied by scanning tunnel microscopy and spectroscopy. The mechanical characteristics of carbon coatings were found to depend strongly on the main parameters determining deposition conditions. The presence of a considerable amount of sp ³ carbon (diamond-like phases) in the films was substantiated.     

Thickness dependence of the optical constants of oxidized copper thin films based on ellipsometry and transmittance

Thin oxidized copper films in various thickness values are deposited onto quartz glass substrates by electron beam evaporation. The ellipsometry parameters and transmittance in a wavelength range of 300 nm–1000 nm are collected by a spectroscopic ellipsometer and a spectrophotometer respectively. The effective thickness and optical constants, i.e.,refractive index n and extinction coefficient k, are accurately determined by using newly developed ellipsometry combined with transmittance iteration method. It is found that the effective thickness determined by this method is close to the physical thickness and has obvious difference from the mass thickness for very thin film due to variable density of film.Furthermore, the thickness dependence of optical constants of thin oxidized Cu films is analyzed.     

Thermal properties of 15-mol% gadolinia doped ceria thin films prepared by pulsed laser ablation

Thermal properties of 15-mol% gadolinia doped ceria thin films (Ce_0.85Gd_0.15 O_1.925) prepared by pulsed laser ablation on silicon substrates in the temperature range 473–973 K are presented. Thermal diffusivities and thermal conductivities were evaluated using photoacoustic spectroscopy. The influence of grain size on thermal properties of the films as a function of deposition temperature is studied. It is observed that the thermal diffusivity and the conductivity of these films decreases up to 873 K and then increases with substrate temperatures. The thermal properties obtained in these films are discussed on the basis of influence of grain size on phonon scattering.     

Microstructural study of thin films of 5 mol% gadolinia-doped ceria prepared by pulsed laser ablation

Microstructural characterization of thin films of 5 mol% gadolinia-doped ceria films deposited by pulsed laser ablation in the energy range 100–600 mJ/pulse has been investigated. As-deposited films were found to be nanocrystalline with preferred orientation. X-ray diffraction (XRD) analysis revealed that the size of the nanocrystals of doped ceria does not vary significantly with increasing laser energy, while transmission electron microscopy (TEM) study showed a uniform distribution of nanocrystals of 8–10 nm for energies ≤200 mJ/pulse and nanocrystals embedded in a large crystalline matrix of doped ceria for energies in the range 400–600 mJ/pulse. Though, the laser-ablated films were totally free from secondary phases, lattice imaging of the large grained doped ceria showed growth-induced defects such as dislocations and ledges. This artice was accidentally published twice. This is the second publication, please cite only the authoritative first one which is available at . An additional erratum is available at . An erratum to this article can be found at     

化学溶液沉积法制备YBCO薄膜的快速分解工艺研究

文中对化学溶液沉积法快速制备YBCO薄膜的工艺进行了探索。通过对分解工艺的优化,成功将薄膜的干燥分解时间缩短到1小时以内,而传统工艺则需要10小时以上的处理时间。以快速分解工艺成相的YBCO薄膜的X射线衍射、扫面电镜和物性测量结果表明薄膜具有良好的c轴外延织构,表面微观形貌平整致密,临界超导转变温度(Tc)为92K。     

Transparent conductive reduced graphene oxide thin films produced by spray coating

Reduced graphene oxide thin films were fabricated on quartz by spray coating method using a stable dispersion of reduced graphene oxide in N,N-Dimethylformamide.The dispersion was produced by chemical reduction of graphene oxide,and the film thickness was controlled with the amount of spray volume.AFM measurements revealed that the thin films have near-atomically flat surface.The chemical and structural parameters of the samples were analyzed by Raman and XPS studies.It was found that the thin films show electrical conductivity with good optical transparency in the visible to near infrared region.The sheet resistance of the films can be significantly reduced by annealing in vacuum and reach 58 k?with a light transmittance of 68.69%at 550 nm.The conductive transparent properties of the reduced graphene oxide thin films would be useful to develop flexible electronics.     

Interaction of dimethyl methylphosphonate with oxidized iron and the effect of coadsorbed water

The behavior of dimethyl methylphosphonate (DMMP), dosed at 100 K with and without coadsorbed water on oxidized iron has been examined by temperature programmed desorption (TPD) and Auger electron spectroscopy (AES). Molecular and dissociated states of DMMP are readily distinguished by the P(LMM) Auger lineshape. At low coverages DMMP undergoes complete decomposition during heating, leaving carbon, phosphorus and oxygen residues on the surface. The major low temperature decomposition products are CH₃OH, H₂O, CO, H₂ and a surface phosphate species. The DMMP decomposition is limited and large exposures lead to molecular DMMP desorption characteristics of multilayers (200–210 K). Pre-exposure to H₂O increases the extent of DMMP decomposition.     

Preparation of CuInS2 thin films by metal-organic decomposition

Metal-organic decomposition (MOD) technique has been developed as a low cost thin film CuInS₂ preparation method for solar cell application. XRD and Raman spectra measurement revealed that deposited films contain CuInS₂. Stoichiometric films with a bandgap of 1.53 eV and an FWHM of 0.45° were obtained from a solution with Cu/In=1.5.