Crystalline Structure Of Films Research Articles

Electrochemical control of composition and crystalline structure of CoNi nanowires and films prepared potentiostatically from a single bath

Using a single bath and controlling the deposition regime, it has been possible to grow electrochemically both CoNi films and nanowires of variable composition and crystalline structure. Low deposition potentials favour the formation of cobalt-rich hcp CoNi films, whereas fcc films (also cobalt-rich) can be obtained at more negative deposition potentials as a consequence of the faster deposition rate. By using membranes to grow CoNi nanowires, the control of the deposition rate is more difficult because the growth is strongly affected by the transport of the electroactive species into the channels: in this case, the structure of the nanowires is also affected by the type of the membrane used (nature, pore’s diameter and length). Short nanowires (between 2μm and 250nm length) in membranes with decreasing pore diameter (200, 100 and 20nm) have been electrodeposited in order to tend to monodomain magnetic nanowires. The magnetic properties of the different deposits related to size, shape, crystalline structure and composition were studied and interpreted.

Correlation between oxygen vacancies and magnetism in Fe-doped In2O3 films

Correlation between oxygen vacancies and magnetic property in the as-deposited and annealed (In0.93Fe0.07)2O3 films has been investigated by X-ray diffraction, magnetization measurement, X-ray absorption near-edge structure and extend X-ray absorption fine structure. Magnetic measurement reveals that clear room temperature ferromagnetism is observed for the as-deposited film, in which the doped Fe ions substitute for In sites of the In2O3 lattice and Fe-related secondary phases or clusters as the source of ferromagnetism is safely ruled out. After high-temperature annealing in air, the crystalline structure of film and occupation sites of Fe ions keep unchanged, whereas the magnetic property has a dramatic decrease. Based on X-ray absorption near-edge spectroscopy analysis and multiple-scattering theoretical calculations, it is found that the content of oxygen vacancy of film remarkably decreases, even disappears by annealing in air, which resulting in greatly decreasing the ferromagnetism. These results further provide strong evidence that the oxygen vacancies play an important role in activating the ferromagnetic interactions in Fe-doped In2O3.

Influence of growth time on crystalline structure, conductivity and optical properties of ZnO thin films

This paper examines the growth of ZnO thin films on glass substrate at 350 °C using an ultrasonic spray technique. We have investigated the influence of growth time ranging from 1 to 4 min on structural, optical and electrical properties of ZnO thin films. The as-grown films exhibit a hexagonal structure wurtzite and are (002) oriented. The maximum value of grain size G = 63.99 nm is attained for ZnO films grown at 2 min. The average transmittance is about 80%, thus the films are transparent in the visible region. The optical gap energy is found to increase from 3.26 to 3.37 eV with growth time increased from 1 to 2 min. The minimum value of electrical resistivity of the films is 0.13 Ω·cm obtained at 2 min. A systematic study on the influence of growth time on the properties of ZnO thin films deposited by ultrasonic spray at 350 °C has been reported.

Experimental Design and Investigation of Novel Pulsed Laser Deposited Structures for YBCO Based Coated Conductors

ABSTRACTThe study of high quality YBa2Cu3O7-x (YBCO) based superconducting films is a fundamental issue to be addressed when dealing with the realization of efficient coated conductors with large current carrying capacity. In this perspective the investigation of innovative buffer layers structures able to allow epitaxial YBCO film grow on metallic substrates and to prevent contamination and degradation issues holds a central role.In this work we thoroughly study the properties of YBCO films grown by means of pulsed lasers deposition on CeO2 template on both bare MgO single crystal and MgO-homoepitaxial/MgO single crystal substrates. Due to its high chemical and temperature stability the MgO reduces the oxygen diffusion effects. On the other hand, the CeO2 layer, pulsed laser deposited, prevents the YBCO film from metallic contamination and facilitates its epitaxial growth. Morphology and crystalline structure of buffer layers and superconductors film are investigated by using scanning electron microscopy (SEM), X-ray and electrons back-scattered diffraction techniques (XRD and EBSD).YBCO films show good critical temperature values (Tc > 87K) with sharp transitions. These encouraging results make our structures promising candidates in the realization of high quality YBCO based coated conductors.

Deformation investigation on iPP/SiO2 composites: Influence of stretching temperature and particle size on morphology evolution and crystalline structure of thin films

In the present work, structure changes during stretching of isotactic polypropylene (iPP) and iPP/silicon dioxide (SiO2) composites have been investigated systematically. The α-form crystal structure of both iPP and iPP/SiO2 composites is destroyed and transforms into the mesophase as the samples are stretched at a low temperature (35°C), while stretching at high temperatures (90°C and 120°C) can restrain the appearance of defects and keep the perfection of crystal structure. FTIR results reveal that the stretching temperatures show no obvious difference of the effect on the orientation of pure iPP, however, the orientation of iPP/SiO2 composites is greatly changed by the tensile temperature. In the case of micron-sized SiO2 particles (average particle diameter d > 1 μm), the orientation of the composites is lower than that of pure iPP at all stretching temperatures. The above results suggest that the stretching temperature and the SiO2 particle size have great influence on the structure variation and orientation behavior of iPP/SiO2 composites.

Electropolymerized Polyaniline Stabilized Tungsten Oxide Nanocomposite Films: Electrochromic Behavior and Electrochemical Energy Storage

Polyaniline (PANI)/tungsten oxide (WO3) nanocomposite films were fabricated by electropolymerization of aniline monomers onto WO3 coated indium tin oxide (ITO) glass slides, which were prepared by spin coating technique and followed by annealing at 500 °C for 2 h. The morphology and crystalline structure of the composite films were studied using Fourier transform infrared (FT-IR) spectroscopy, atomic force microscopy (AFM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The results confirm chemical interactions between the polymer matrix and the WO3 particles and reveal a well crystallized PANI/WO3 nanocomposite structure. The optical properties and electrochemical capacitive behaviors of the composite films for electrochromic (EC) and energy storage devices applications were investigated using spectroelectrochemistry (SEC), cyclic voltammetry (CV) and galvanostatic charge–discharge measurements. The composite films show dual electrochromism at both positive and negative potentials arising from PANI and WO3, respectively. A coloration efficiency of 98.4 cm2 C–1 was obtained for the composite film, which was much higher than that of WO3 (36.3 cm2 C–1) and PANI (50.0 cm2 C–1) thin film. An areal capacitance of 0.025 F cm–2 that is comparable to that of pure PANI (0.075 F cm–2) is derived from CV at a scan rate of 5 mV/s with a broader working potential window of 1.3 V. The cyclic stability studies reveal that the composite films exhibit much more enhanced durability and retain significant charge storage or discharge capacity after 1000 charge–discharge cycles. However, pure PANI loses most of the charge storage or discharge capacity after 350 cycles. The chemical bonding between PANI matrix and WO3 particles is believed to play an important role in enhancing the stability of the nanocomposite film.

Gasochromic tungsten oxide films with PdCl2 solution as an aqueous Hydrogen catalyst

In this study, WO3 nanostructured films were prepared by sol–gel spin coating process on glass substrates and drops of PdCl2 solution were used as an aqueous hydrogen catalyst for gasochromic investigations. As deposited WO3 films were annealed at different temperatures of 100, 200, 300 and 400°C in air. The effect of annealing temperature on crystalline structure and surface morphology of WO3 films was studied by X-ray Diffraction (XRD), Field Emission Scanning Electron Microscope (FE-SEM) and/or Atomic Force Microscope (AFM). Fourier Transform Infrared (FTIR) spectroscopy revealed the variation of chemical bonds with annealing temperature. Because of the aqueous nature of hydrogen catalyst, hydrophilicity of samples was measured by means of contact angle and it was found to increase with annealing temperature. We found a correlation between annealing temperature, hydrophilicity, palladium growth and coloring of tungsten oxide films when an aqueous hydrogen catalyst is used. The effect of catalyst concentration on colored state optical density was also studied for films annealed at 400°C.

Optical and photoelectrochemical properties of a TiO2 thin film doped with a ruthenium–tungsten bimetallic complex

Optical and photoelectrochemical (PEC) properties of a TiO2 thin film electrode doped with a new variation of ruthenium–(4,4′dimethyl-2,2′-bipyridine)–isothiocyanato–tungsten[bis-(phenyl-1,2-ethilenodithiolenic)] bimetallic complex (BM) were investigated. Physical adsorption process was used to immobilise the BM on the TiO2 thin film. Crystalline structure and surface morphology of the thin films were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy-dispersive X-ray (EDX) techniques. N3 commercial dye was also used as a dopant to the TiO2 films for comparison. Light absorption spectra and bandgap energy of the thin films were determined using UV–vis spectroscopy. Light absorption of the TiO2 thin film doped with BM was better than the TiO2 doped with the N3 commercial dye. Band edges of the TiO2 thin film and the BM were determined via cyclic voltammetry (CV) measurements. Top-edge of the BM valence band (VB) was more positive than the bottom edge of the conduction band (CB) of the TiO2 film (vs. NHE). PEC analysis indicated that photocurrent of TiO2 doped with the BM electrode was higher than TiO2 doped with the N3 in the beginning of illumination process, but the performance was defeated after a while. Based on the optical properties and the PEC analyses, BM has potential to be used as dye sensitisers for a PEC cell.

In-Plane Optical Anisotropy of a-Plane GaN Film on r-Plane Sapphire Grown by Metal Organic Chemical vapour Deposition

The in-plane optical anisotropic properties of the non-polar a-plane GaN films grown by metal organic chemical vapour deposition are investigated by using polarised photoluminescence (PL), optical transmission and Raman scattering measurements. Through polarised PL and transmission spectra, the in-plane optical anisotropic properties of a-plane GaN film are found, which are attributed to the topmost valance band (at Γ point) split into three sub-bands under anisotropic strain. The PL spectra also exhibit that the light hole band moves up more rapidly than the spin-orbit crystal-field spilt-off hole band with the increasing in-plane anisotropic compressive strain. Raman scattering spectra under different configurations further indicate the in-plane anisotropy and the hexagonal crystalline structure of these a-plane GaN films.

Photocatalytic activity of thin TiO2 films deposited using sol–gel and plasma enhanced chemical vapor deposition methods

Thin titanium dioxide films, deposited using RF PECVD and sol–gel techniques, were studied comparatively with respect to their bactericidal as well as self-cleaning properties. The effect of the deposition process on film morphology, chemical and crystalline structure, bactericidal activity and hydrophilic properties was investigated using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), surface profilometry, optical microscopy and contact angle measurements. It was found that the bactericidal activity of amorphous TiO2 films, produced using the RF PECVD method, as either comparable to or better than those of crystalline (anatase) films deposited by means of the sol–gel technique. One reason for such advantageous behavior of plasma deposited materials is thought to be their substantially higher surface roughness, as revealed by AFM measurements. The hydrophilic effect, induced with UV irradiation, was strongest in the case of sol–gel films, but the RF PECVD synthesized coatings were found to be only slightly less hydrophilic. The conclusion follows that both sol–gel and RF PECVD techniques are equally capable of producing titanium dioxide films of high photocatalytic quality.

Influence of annealing temperature on structure and photocatalytic activity of TiO2 thin films prepared by DC reactive magnetron sputtering method

Transparent TiO2 thin films were successfully prepared on high purity silica substrates by DC reactive magnetron sputtering method and annealed at different temperatures. The effects of the annealing temperature (300–600 °C) on crystalline structure, morphology, and photocatalytic activity of the TiO2 thin films were discussed. The photocatalytic activity of the films was evaluated by photodegradation of methylene blue solution. With increasing annealing temperature, the photocatalytic activity of the TiO2 thin films gradually increased because of the improvement of crystallization of anatase TiO2 thin films. At 500 °C, the TiO2 thin film shows the highest photocatalytic activity due to the improvement of crystallization of anatase TiO2 thin films. When the annealing temperature increases to 600 °C, the photocatalytic activity of thin film decreases owing to the formation of rutile phase and the decrease of surface area.

81 Application of quantum therapy in complex treatment of bronchial asthma in children

This chapter discusses the as-quenched microstructures in Fe–25Cr–20Ni-based melt-spun and sputtered alloys. The microstructure morphology and the phase type encountered in the as-quenched Fe–25Cr–20Ni steels are liable to contain high segregation coefficients elements such as sulfur, carbon, or boron. These steels are prepared by melt spinning or sputtering. The sputtering targets are massive or compacted powder mixtures; the sputtered films obtained have approximately the chemical composition of the targets. As opposed to ribbons, sputtered films crystalline structure is composed, at room temperature, of a great amount of b.c.c. metastable ferrite. The microstructure is characterized by very fine regular grains with a 10 nm average size, in agreement with the calculated value from Scherrer's law relative to the half-intensity width of X-ray lines. This chapter also discusses the effects of sulfur, carbon, and boron addition on microstructures.

Influence of ion assistance on LaF3 films deposited by molybdenum boat evaporation

LaF3 thin films at 193 nm were deposited by the molybdenum boat evaporation with ion-assisted deposition (IAD). Various optical characteristics, stress, and microstructures that formed under different ion-beam voltages of IAD deposition were investigated. The relation between these properties is also discussed. LaF3 films deposited with IAD exhibited small rough surfaces and large optical loss at 193 nm. The largest value of optical loss for films at 193 nm, which were prepared at an ion-beam voltage of 400 V, was 1.55% and the extinction coefficient was smaller than 0.0015. Microstructures and crystalline structures of films were influenced and changed by the ion-assisted deposition process. Tensile stress value of films increased as the ion-beam voltage rose. Refractive index, related to the packing density and microstructures, also increased as the ion-beam voltage rose.

Thermal properties and crystallization behaviors of medium-chain-length poly(3-hydroxyalkanoate)s

Medium-chain-length poly(3-hydroxyalkanoate)s (mcl-P(3HA)s) with different side-chain length ranging from C3–C9 were synthesized from 2-alkenoic acids of C6–C12 by using a metabolically engineered strain of Escherichia coli. The effect of side-chain length of mcl-P(3HA)s on thermal properties and crystallization behaviors was investigated by DSC and X-ray analyses. All mcl-P(3HA)s formed a chain-packed crystalline structure in the solvent-cast films. Melting temperatures of solvent-cast film of mcl-P(3HA)s first decreased from 59 °C to 45 °C with the change of side-chain from C3 to C4 and thereafter increased to 69 °C with an extension of side-chain to C9. The X-ray diffraction patterns indicate the formation of a layered structure aligned the main-chains in planes involving side-by-side packing of side-chains with a periodic distance of 1.6–2.8 nm for the mcl-P(3HA)s with over C4 side-chain. The interlayer distance increased proportionally to the length of side-chain for the mcl-P(3HA)s with over C4 side-chain, while the corresponding value of mcl-P(3HA) with C3 side-chain was apparently deviated from the extrapolated line plotted the distance against side-chain length. These results indicate that the changeover in crystallization manner occurs between P(3HA)s with under C3 side-chain and with over C4 side-chain. For the mcl-P(3HA)s with side-chain carbon number over C7, two distinct phase transitions were happened during heating process from a melt-quenched amorphous state. At lower temperature region, the mcl-P(3HA) molecules formed a smectic liquid-crystalline structure owing to the side-chain interactions, and the structure was disrupted at temperatures between 20 and 50 °C. After the disruption of smectic aggregates, the crystallization of mcl-P(3HA) chains immediately occurred with participation of both main- and side-chains.

Magnetization reversal analysis of a thin B2-type ordered Co50Fe50 film by magnetooptic Kerr effect

The magnetic structure of a thin B2 ordered Co50Fe50 film is determined by vectorial magnetometry using magnetooptic Kerr effect including different polarizations of the incident light and varied directions of the external magnetic field. Both the magnetic reversal process and the magnetic remanence reveal two in-plane magnetic easy axes of different strengths which are not orthogonal. Atypical magnetization curves including multidomain states in magnetic remanence with some magnetic moments providing antiparallel alignment to the direction of the previously applied external field (if projected to the direction of the external field) confirm the appearance of different strong magnetic easy axes. This magnetic structure can be explained by a cubic magnetic anisotropy (CMA) induced by the crystalline film structure superimposed by an additional uniaxial magnetic anisotropy (UMA) which is not parallel to one of the magnetic easy axes of the CMA. The results are compared with the regular magnetic behaviour of a thin A2 ordered Co50Fe50 film with UMA parallel to one of the magnetic easy axes of the CMA.

Nanoporous ZnO film grown on sapphire by chemical vapor deposition

Without template, nanoporous zinc oxide (ZnO) film was grown on sapphire in a homemade chemical vapor deposition system under atmospheric pressure. In large area, the uniform pores have almost equal inner diameters of 500nm and the figurations of the pores are quasi hexagons. The wurtzite crystalline structure and preferred (0001) orientation of the nanoporous ZnO film were confirmed by X-ray diffraction. The high element purity and optical quality were testified by the strong E2 vibration modes in Raman scattering and the sharp ultraviolet emission at 380nm in photoluminescence, respectively. These results show a potential method for fabricating nanoporous ZnO film at low cost.

Transparent and crystalline Al-doped ZnO film-embedded heterojunction Si solar cell

A heterojunction of Al-doped ZnO (AZO) and Si was applied as a solar cell. Quality AZO films were grown by a co-sputtering technique using a RF power supply for ZnO while a DC one for Al. The Al content significantly modulates the electrical performance and crystalline structure of the AZO films. The lowest resistivity of AZO film was achieved to be 5.4×10−4Ωcm. The crystalline structures of different Al-containing AZO films were systematically investigated by X-ray diffraction.A transparent AZO film was deposited onto an n-Si substrate. This AZO/Si heterojunction diode offers an ideality factor of 1.19. Under illumination, the heterojunction provided a short-circuit current of 15.64mA/cm2 and an open-circuit voltage of 321mV.This research presents the quality growth of AZO films by using a co-sputtering method. It also discusses the working mechanism of the heterojunction n-AZO/n-Si solar cells with unique design schemes.

Layer resolved evolution of the optical properties of α-sexithiophene thin films

We report a combined reflectance difference spectroscopy and scanning tunneling microscopy study of ultrathin α-sexithiophene (6T) films deposited on the Cu(110)-(2×1)O surface. The correlation between the layer resolved crystalline structure and the corresponding optical spectra data reveals a highly sensitive dependence of the excitonic optical properties on the layer thickness and crystalline structure of the 6T film.

Investigation of structural and magnetic properties of Ni, NiFe and NiFe2O4 thin films

Soft magnetic thin films of Ni, NiFe and NiFe2O4 were prepared using reactive magnetron sputtering in various deposition conditions. Experimentally observed soft magnetic property was compared and correlated with nanocrystalline structure evolution. Ni and NiFe deposited films are textured with fcc(111) phase preferred orientation. Accordingly, grain size and lattice parameter were calculated from X-ray diffraction (111) peak line width and 2θ peak position. Addition of reactive gas oxygen in deposition process has substantial effect on crystalline structure of film. There is phase transition from the ordered NiFe (111) structure to the NiFe2O4 nanocrystalline phase. The resulting film has shown small X-ray diffraction intensity peak corresponding to (311) and (400) orientation, indicating small amount of existing NiFe2O4 phase. The mechanism has been discussed to be responsible for nanocrystallization and amorphization of NiFe2O4 films. Magnetic measurement (M-H) loop reveal soft magnetic nature of films with magnetic anisotropy. The coercivity (Hc) of films is in accordance with random anisotropy model, where Hc reduced with grain size. The structural transformation was supported by Fourier transforms infrared spectroscopy measurement. The films are highly smooth with surface roughness in the range of ∼0.53–0.93nm. NiFe2O4 films have shown lowest surface roughness with highest electrical resistivity values. The structural, surface, magnetic and infrared spectroscopy results are observed and analyzed.

Surface morphology and crystalline structure of high-stable polycrystalline transparent conductive zinc oxide films

Surface morphology and crystalline structure of high-stable zinc oxide films were evaluated by atomic force microscopy, scanning electron microscopy and X-ray diffraction (XRD) measurements. AFM measurement revealed that the higher stable samples have smaller roughness (average roughness and root mean square) parameters than the lower stable samples. Furthermore, in-plane XRD measurement showed that the crystallite size of high stable samples is smaller than that of the low stable samples. These results indicate that the larger surface area and lower film density deteriorates the stability of zinc oxide films through the adsorption and reaction of water or oxygen molecules. They also suggest that we can prepare the high stable zinc oxide transparent electrode films by controlling the surface morphology.