Metal oxide composite thin films made by magnetron sputtering for bactericidal application

Plasma polymerized (PP) 2,6-diethylaniline (DEA) and N,N,3, 5 tetramethylaniline (TMA) composite thin films were deposited by dynamic plasma (AC, 50 Hz) polymerization technique using a capacitively coupled reactor of diverse monomer composition. The composite film thickness increased proportionally with the percentage of TMA in the composition. X-ray photoelectron spectroscopy confirmed the uniformity of the film composition, consisting primarily of carbon, nitrogen, and oxygen, with different possible groups such as C–C, C–H, C–N, and C–O. Field emission scanning electron microscopy images revealed smooth and homogeneous surface morphologies in the composite films, which contrast with the thin homopolymer films. The current density (J) vs voltage (V) behaviors of the homopolymer and composite polymer thin films sandwiched between aluminum electrodes demonstrated that the J values could be tailored by adjusting the individual monomer concentration in the PP(DEA:TMA) composite films, as well as by increasing the measurement temperature (298–373 K). The conduction behavior of these composite films exhibited ohmic characteristics in the lower voltage region (below 10 V), while space charge-limited conduction dominated in the higher voltage region (above 10 V) across the entire temperature region. The activation energy was ∼0.019 eV in the ohmic region and 0.260 eV in the non-ohmic region. Changing the composition of two monomers can tune the properties of the as-deposited films, making the film suitable for various electronic and optoelectronic devices.

Si thin films are attracted as materials for ultra-large-scale solar cell systems at relatively low cost. Electrodeposition is expected as one fabrication method of Si thin films due to its advantages such as relatively simplicity process, precision control of nanostructure and continuous deposition in large area. Si thin films have been electrodeposited in non-aqueous solvents owing to their large electrochemical windows which allows for the study of Si electrodeposition [1-3]. Among various non-aqueous solvents, organic solvents and ionic liquids, which can be used under low temperature, have been used as electrolytes for the electrodeposition of Si thin films in our laboratory. We have previously succeeded to electrodeposit Si thin films in organic solvents and ionic liquids [4-6]. However, there is a problem for applications to solar cells that some impurities (mainly carbon and oxygen) are incorporated in thin films. We have reported the carbon content can be reduced by annealing treatment [7]. On the other hand, the decrease of oxygen content is still required. Thus, we evaluate the composition of Si thin films electrodeposited in an organic solvent and an ionic liquid without oxygen atoms in order to analysis the effect of bath conditions on the composition of thin films (especially, where the oxygen incorporated in Si thin films comes from). Si thin films were electrodeposited with 3 electrode cell (W.E. : Au, R.E. : Ag/Ag+, C.E. : Pt) in acetonitrile, 0.3 M tetrabutylammonium chloride and 0.5 M SiCl4 was used as an organic solvent, and 1-butyl-3-methylimidazolium hexafluorophosphate and 0.5 M SiCl4 as an ionic liquid. The composition of Si thin films were evaluated by X-ray photoelectron spectroscopy. As a result, the oxygen content in Si thin films were decreased by using the solvents without oxygen atoms in both organic solvent and ionic liquid cases. This results suggest that the reason the oxygen inclusion is derived from the incorporation of solvents themselves in films during electrodeposition, and propose us the way to obtain films with low impurities. In addition, the rotating disk electrode was used in the organic solvent case in order to promote the convection. The usage of this rotating disk electrode showed the decrease of impurities in Si thin films. Therefore, it is indicated that the stable supply of SiCl4 to the electrode surface is important factor to obtain films with low impurities. This study reveals that bath condition significantly affects to the composition of Si thin films, and could help us to fabricate films for applications to solar cells. This study was financially supported in part by the Japan Science and Technology Agency (JST) CREST program, and Y. T. acknowledges the Leading Graduate Program in Science and Engineering, Waseda University, from MEXT, Japan. [1] S. Zein El Abedin, N. Borrissenko, F. Endres, Electrochem. Comm., 6 (2004) 510. [2] T. Munisamy, A. J. Bard, Electrochim. Acta, 55 (2010) 3797. [3] M. Bechelany, J. Elias, P. Brodard, J. Michler, L. Philippe, Thin Solid Films 520 (2012) 1895. [4] Y. Nishimura and Y. Fukunaka, Electrochim. Acta, 53 (2007) 111. [5] T. Homma, J. Komadina, Y. Nakano, T. Ouchi, T. Akiyoshi, Y. Ishibashi, Y. Nishimura, T. Nishida, and Y. Fukunaka, Electrochem. Soc. Trans., 41 (2012) 9. [6] J. Komadina, T. Akiyoshi, Y. Ishibashi, Y. Fukunaka, T. Homma, Electrochim. Acta, 100 (2013) 236. [7] Y. Tsuyuki, A. Pham, J. Komadina, Y. Fukunaka, T. Homma, Electrochim. Acta, 183 (2015) 49.

Sol-gel and coprecipitation methods successfully prepared titanium dioxide (TiO2) powders with anatase structure. The TiO2 powders are then used to fabricate pure TiO2 thin-film or mixed with SnO2 powders for the TiO2/SnO2 composite thin film. Furthermore, the structural, morphological, as well as the optical properties of films were also investigated. The results showed that the synthesized thin-film of TiO2 powders by sol-gel method obtained better crystallinity and microstructure compared to the synthesized thin film by co-precipitation method. In the DSSC system, these features are needed to increase the electron mobility that responsibility for transport and recombination of photoexcited electrons. SEM images exhibited the smooth surface and uniform in particle size obtained by the addition of SnO2 powders in composite films. The composite thin film also indicated a higher transmittance value. Keywords: sol-gel,co-precipitation,anatase, composite.

Here, we study the self-aligned asymmetric electrically conductive composite thin film prepared via casting of graphene oxide (GO)/poly (vinylidene-hexafluoropropylene) (PVDF-HFP) dispersion, followed by low temperature hydriodic acid reduction. The results showed that composite thin film revealed the high orientation of graphene sheets along the direction of film surface. However, graphene sheets are asymmetrically distributed along the film thickness direction in the composite film. Both sides of as prepared composite film showed different surface characteristics. The asymmetric surface properties of composite film induced distinction of surface resistivity response; top surface resistivity (21 Ohm) is ∼ 4 times higher than bottom surface resistivity (5 Ohm). This asymmetric highly electrically conducting composite film revealed efficient electromagnetic interference (EMI) shielding effectiveness of ∼ 30 dB. This study could be crucial for achieving aligned asymmetric composite thin film for high-performance EMI shielding radiation.

This paper presents an experimental comparative study involving the characterization of the thermo-electrical and structural properties of graphene-based vanadium oxide (graphene-VOx) composite thin films on insulating and conducting surfaces (i.e., fused quartz and acrylic resin-impregnated graphite) produced by a sol-gel process via dipping-pyrolysis. A combination of FE-SEM and XPS analyses revealed that the graphene-VOx composite thin films (coated onto fused quartz) exhibiting the microstructure of 2-graded nanowire arrays with a diameter of 40-80 nm were composed of graphene, a few residual oxygen-containing functional groups (i.e., C-O and C=O), and the VO2 Magnéli phase. The temperature-dependent electrical resistance measured on the as-deposited thin films clearly demonstrated that the graphene-VOx composite nanowire arrays thermally grown on fused quartz act as a semiconductor switch, with a transition temperature of 64.7 degrees C in the temperature range of -20 degrees C to 140 degrees C, resulting from the contributions of graphene and graphene oxides. In contrast, the graphene-VOx composite thin films deposited onto acrylic resin-impregnated graphite exhibit a superlinear semiconducting property of extremely low electrical resistance with negative temperature coefficients (i.e., approximately four orders of magnitude lower than that of the fused quartz), despite the similar microstructural and morphological characteristics. This difference is attributed to the synergistic effects of the paramagnetic metal feature of the tightly stacked nanowire arrays consisting of hexagonal V2O3 on the intrinsic electrical properties of the acrylic resin-impregnated graphite substrate, as revealed by FE-SEM, EDX, AFM, and XRD measurements. Although the thermo-sensitive electrical properties of the graphene-VOx composite thin films are very substrate specific, the applicability of graphene sheets can be considerably effective in the formation of highly planar arrays of VOx nanowires to enhance carrier transport.

Tungsten oxide/bismuth oxide composite thin films prepared by multi target radio frequency (RF) reactive sputtering were investigated. X-ray diffraction measurements of the crystallinity of thin films prepared at room temperature revealed amorphous structure. Although the compositional ratio of composite thin films prepared at 50 W and 75 W of the RF power of the Bi target was almost the same, those prepared at 50 W were transparent, and had a much smaller optical absorption coefficient at 3.0 eV than those prepared at 75 W. Bi 4f spectra of these thin films were measured by X-ray photoelectron spectroscopy, and were analyzed by full width at half maximum of Bi 4f7/2 peaks. As a result, the transparency is thought to be caused by the change of bonding state of Bi-O. Electrochromic properties of the composite thin films were also measured in 0.1 M H2SO4. Coloration of composite thin films prepared at 20 W of the RF power of the Bi target changed reversibly from transparent to black and brown.

In this paper, graphene/ZnO composite film is fabricated by fairly rapid and easy approach. Zinc oxide (ZnO) (<50 nm particle size) has been immediately deposited on uncured pre-deposited randomly oriented graphene flakes (less than four layers) thin film, using electrohydrodynamic atomization technique (EHDA). After curing, graphene/ZnO composite film morphology and structure have been characterized. For electrical behavior analysis, graphene/ZnO composite thin film is employed as cathode in a diode device indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS)/poly(dioctylfluorene–benzothiadiazole) (F8BT)/(graphene/ZnO). Obtained J–V curve shows diode behavior i.e., at voltage of 0.3 V, the current density in organic structure is at low value of 1.4 × 10−5 A/cm2 and by further increasing the applied voltage to 2 V, the device current density is increased by 50 times and has reached up to 6.3 × 10−4 A/cm2.

Conductive carbon was codeposited with LiFePO 4 to enhance the electrical conductivity of the olivine-type LiFePO 4 thin films. In this approach, poly(vinyl alcohol) was used as the source for carbon as well as the binder for target densification. After a highly densified (>80%) LiFePO 4 -C target was fabricated, pulse laser deposition (PLD) technique was employed to deposit the LiFePO 4 -C composite thin films on the Si/ SiO 2 /Ti/Pt substrates. The as-deposited LiFePO 4 -C composite films were characterized by techniques of X-ray diffraction, scanning electron microscopy, Raman scattering spectroscopy, X-ray photoelectron spectroscopy, DC conductivity measurement, as well as cyclic voltammograms, electrochemical impedance spectroscopy, and galvanostatics. The effects of carbon content and postdeposition annealing treatments on the electrochemical performances of the as-deposited film electrodes were carefully investigated. The results showed that the codeposited carbon was homogeneously distributed throughout the LiFePO 4 films. It was found that 2 mol% carbon was the optimized amount for the highest capacity. Postdeposition annealing at 600 °C for 6 h in the same vacuum chamber could considerably improve the Coulombic efficiency as well as the high rate capability of the PLD-deposited LiFePO 4 -C composite thin films. However, the specific capacity would be reduced.

SiO2 composite thin films containing InP nanocrystals were fabricated by radio-frequency magnetron co-sputtering technique. The microstructure of the composite thin films was characterized by X-ray diffraction and Raman spectrum. The optical absorption band edges exhibit marked blueshift with respect to bulk InP due to strong quantum confinement effect. Non-linear optical absorption and non-linear optical refraction were studied by a Z-scan technique using a single Gaussian beam of a He-Ne laser (632.8 nm). We observed the saturation absorption and two-photon absorption in the composite films. An enhanced third-order non-linear optical absorption coefficient and non-linear optical refractive index were achieved in the composite films. The nonlinear optical properties of the films display the dependence on InP nanocrystals size.

Nanostructured ruthenium – gadolinia-doped ceria composite anodes for thin film solid oxide fuel cells

SrBi2Ta2O9/polycarbonate (SBT/PC) composite thin films were prepared by spin coating method. Ultra-fine SrBi2Ta2O9(SBT) (∼ 40–50 nm) nanocrystals with pure layered-perovskite phase were synthesized by a polymerizable complex route. The structure and morphology of SBT nanocrystals and composite films were studied by means of x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The frequency and temperature dependence on dielectric properties of SBT/PC composite thin films were evaluated. The orientation degree of nanocrystals in PC polymer was estimated by measuring the transparency spectra of unpoled and poled composite thin films. The poling relaxation properties after corona poling were examined.

Investigations on structural, optical and electrical properties of microwave-assisted rGO:ZnO nanocomposite thin films

Ferroelectric/ferrite composite films are excellent systems in which the electromagnetic material properties can be tuned through changes in composition as well as microstructure. We report on our studies of the structural and magnetic properties of Ba0.5Sr0.5TiO3/BaFe12O19 (BSTO/BaM) composite thin films deposited on Al2O3 substrates using magnetron sputtering. Optimizing the sputtering conditions and postdeposition annealing lead to high-quality films without any impurity phases. Magnetic measurements yield saturation magnetization values in the range of 100 to 200 emu/cm3. Hysteresis loops exhibit a double transition that is observed only in the composite films and not in pure hexaferrite films grown under identical deposition conditions. The unusual feature in the M–H data is ascribed to the possibility of magnetodielectric effects associated with intergranular magnetic coupling mediated by the BSTO polarization layer.

A comparison of qualitative and quantitative adhesion analysis for a composite thin film system

Using tetraethoxysilane and 3-aminopropyltriethoxysilane as the silica sources, amino-functionalized organic/inorganic hybrid mesoporous silica thin films with 2-dimensional hexagonal structure have been synthesized by evaporation induced self-assembly process in the presence of cetyltrimethyl ammonium bromide templates under acid conditions. The Keggin-type molybdphosphoric acid (PMo) is incorporated into the mesoporous silica thin films with amino-groups by wetness impregnation, and the PMo/silica mesoporous composite thin films are obtained. The results of X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), and Fourier transform infrared (FTIR) spectra indicate the PMo molecules maintain Keggin structure and are homogeneously distributed inside mesopores. The composite thin films possess excellent reversible photochromic properties, and change from colorless to blue under ultraviolet irradiation. The photochromic mechanism of the composite thin films is studied by ultraviolet-visible (UV-vis), electron spin resonance (ESR) and X-ray photoelectron spectroscopy (XPS) spectra. It is shown that intervalence charge transfer (IVCT) and ligand-to-metal charge transfer (LMCT) are the main reasons of photochromism. PMo anions interact strongly with amino-groups of the mesoporous suface via hydrogen bond and electrostatic force. After ultraviolet irradiation, the charge transfer occurs by reduction of heteropolyanions accompanying the formation of heteropolyblues with multivalence Mo(VI, V), and the bleaching process of composite thin films is closely related to the presence of oxygen.