Polyvinyl alcohol thin film reinforced by green synthesized zirconia nanoparticles

The focus of this work is to prepare polyvinyl alcohol (PVA) thin film reinforced by green synthesized zirconia nanoparticles. In order to do so, firstly, zirconia nanoparticles were synthesized by the rosemary extract-assisted sol-gel process as both template and stabilizing agents. The results showed that the as-obtained sample with zirconium salt to rosemary extract ratio of 1:4 had a semi-spherical morphology with the mean particle size of 12–17?nm. This nanoparticle was added as reinforcement with different ratios to the polyvinyl alcohol matrix. The mechanical property of the as-prepared nanocomposites revealed that the elastic modulus of 1?wt% ZrO2-PVA sample was about 5.5 times higher than pure PVA thin film.     

Wafer scale catalytic growth of graphene on nickel by solid carbon source

We report the growth of graphene by solid carbon source on full 8-inch wafers. The first step is to deposit the fine-tuned carbon source and the nickel catalyst thin films on top. The second step is to anneal the stack for driving carbon throughout the catalyst and grow graphene upon the surface. The graphene can be optimized by tuning the stack design and the annealing conditions. Via this method, graphene with a transmittance of 91.9% and a sheet resistance of 565 Ohm/sq has been obtained. Our technique provides a rapid route to grow large scale graphene using standard microelectronic facilities.     

Magnetic studies on one-step chemically synthesized nickel ferrite thin films

Nickel ferrite thin films were synthesized at room temperature using one-step electrodeposition solution processing. Reaction kinetics was also proposed. An effect of air baking on the structural, surface morphological and magnetic properties was investigated. As-deposited nickel ferrite thin films were cubic in crystal structure. Calculated grain size after annealing was increased from 30 to 48 nm in addition to formation of rough surface morphology. Due to decrease in defect levels after air baking the annealed nickel ferrite thin film showed saturation magnetization of 268 emu/cc, higher than non-annealed (230 emu/cc), when used in magnetic studies.     

Structural and charge transport characteristics of graphene layers obtained from CVD thin film and bulk graphite materials

We report an experimental comparative study of graphene layers produced by micromechanical cleavage of bulk graphite materials of different origins and graphite films obtained by plasma enhanced chemical vapor deposition (PECVD). Structural characteristics of these materials were evaluated using Raman spectroscopy and electron microscopy. Field effect transistors (FETs) based on the PECVD graphene were produced using electron beam lithography. Conductivity, carrier mobility and other characteristics of the PECVD graphene obtained from Raman and FET tests were similar to the properties of graphene flakes obtained from bulk graphite materials. Taking into account the scalability of the CVD fabrication, these results confirm the possible industrial use of graphene films obtained by this method.     

Multi-layer graphene obtained by high temperature carbon implantation into nickel films

We present a study of carbon implantation in a stacked layered substrate made of Ni(200 nm)/SiO₂(300 nm)/Si(1 0 0). The carbon atoms have energy of 20 keV. Simultaneous or subsequent heat treatment is performed in the 450–600 °C range. The carbon dose was set to be 4 equivalent graphene monolayers (EGM). Most of the carbon implanted diffuses directly to the surface, forming multi-layer graphene (MLG). A progressive structuration of these graphitic fragments occurs with the increase of the implantation temperature. However, this structuration is more pronounced if the thermal treatment is performed in situ following the carbon implantation at room temperature. The mean MLG thickness, corresponding to around 4–5 EGM, was measured by angular X-ray Photoemission Spectroscopy. Moreover, the overall carbon concentration inside and at the limits of the nickel films, determined by nuclear reaction analysis (NRA), is in the 7–10 EGM range. This concentration depends on the temperature but it exceeds surprisingly the expected carbon concentration. This discrepancy shows that some carbon is incorporated along the different steps. NRA analyses of the preparation confirm this point. To obtain large film, the presented results stress the interest to better understand the full system carbon–nickel in the preparation of MLG at each step of the process.     

Deposition of highly oriented lanthanum nickel oxide thin film on silicon wafer by CSD

This paper describes the orientation control and the electrical properties of the chemical solution deposition (CSD) derived LaNiO₃ (LNO) thin film. The LNO precursor solutions were prepared using lanthanum nitrate and nickel acetate as La and Ni source, and ethanol or 2-methoxyethanol and 2-aminoethanol mixed solution as solvents. The LNO films were spin-coated using these precursor solutions and annealed at the temperature from 500 to 700 °C. The resulting LNO film annealed at 700 °C derived from 2-methoxyethanol and 2-aminoethanol mixed solvent exhibited (1 0 0)-orientation, with some surface cracks and pores, and relatively higher resistivity of 2.49 × 10⁻³ Ω cm. The LNO film derived from 2-methoxyethanol and 2-aminoethanol mixed solvent annealed at 700 °C in an oxygen atmosphere showed highly (1 0 0)-orientation, with higher density, a few cracks and pores, and exhibited a good electrical resistivity of 7.27 × 10⁻⁴ Ω cm.     

SMA polymer thin film electrodeposition on carbon particles

Electrodeposition of styrene-co-maleic anhydride (SMA) polymer, as thin films on carbon particle substrates, was carried out in a fluidized electrode bed reactor (FEBR). Feeder current, time of deposition, flow rate of anolyte (i.e., bed expansion or bed porosity), concentration of SMA in the anolyte, and pH of the anolyte were the key parameters investigated. The film characteristics were evaluated through SEM and FTIR analyses, the amounts determined by weighing. The effect of these parameters on the electrodeposition process is discussed and optimum conditions for deposition are proposed. Also, a possible mechanism for electrodeposition, particularly for the SMA–carbon system, is discussed. Furthermore, where relevant, the parameters and mechanism are compared with those for our parallel work on the ethylene-co-acrylic acid (EAA)–carbon system.     

Remarkably enhanced photocatalytic activity by nickel nanoparticle deposition on sulfur-doped titanium dioxide thin film

To enhance the photocatalytic performance of titanium dioxide, the structures of both bulk and surface were modified. Doping of sulfur atoms to be substituted for lattice oxygen atoms of titanium dioxide was carried out to extend the light absorption by atmosphere-controlled pulsed laser deposition, which allows direct preparation of impurity-included thin film such as sulfur-doped titanium dioxide. On the other hand, to enhance the surface catalytic reaction, nickel nanoparticles were deposited at the thin film substrate by chemical vapor reductive deposition method, which is a novel preparation technique of metallic nanoparticles on the substrate surface. Obtained sulfur-doped titanium dioxide was found to possess sensitivity to visible light with the wavelength up to 550 nm, indicating the photocatalytic activity in visible region. Sulfur doping induced the dye degradation activity under visible light irradiation. When nickel nanoparticles were deposited, a remarkable enhancement of the hydrogen evolution activity through ethanol decomposition of more than 20 times as much as unmodified titanium dioxide thin film was accomplished. In addition, the stability of sulfur atom doped into titanium dioxide structure was investigated.     

Thermal properties and characteristics of thin layers of nickel dithiolene complexes

Thermal properties of near infra–red–absorbing nickel dithiolene complexes have been examined by thermal gravimetric and differential scanning calorimetry analysis. The nickel complexes with relatively low melting points gave a DRAW disc with better recording characteristics, when they were used as inhibitors of the photofading of thin layers of cyanine dyes. Thin layers of the nickel complexes on polymethylmethacrylate or glass were formed by spin coating and by the radio–frequency reactive ion plating technique. Their reflectance, absorption spectra and optical recording characteristics have been recorded.     

Synthesis and properties of an atomically thin carbon nanosheet similar to graphene and its promising use as an organic thin film transistor

We synthesize an atomically thin carbon nanosheet (CNS) analogous to graphene with properties suitable for an organic thin film transistor (OTFT). The synthesis of graphene by chemical vapor deposition has serious drawbacks such as wrinkles, grain boundaries, and defects due to catalyst removal and transfer process. Here the CNS is directly synthesized on a silicon wafer by heat-treatment of spin-coated polyacrylonitrile and shows a higher electrical conductivity (>1600 S cm⁻¹) than that of chemically converted graphene. The CNS on glass, transferred from a silicon wafer, exhibits approximately 92% optical transmittance. We have used our CNS as the electrodes of OTFTs, and recorded a mobility (0.25–0.35 cm² V⁻¹ s⁻¹) that exceeds that of gold electrodes (0.2–0.25 cm² V⁻¹ s⁻¹).     

Electrochromism of nickel oxide thin film with polymer gel electrolyte

Polymer gel electrolytes were investigated for an electrochromic device (ECD) using nickel oxide thin film. Poly(ethylene oxide) (PEO) derivatives were cross‐linked and swelled in KOH–aqueous solution giving a hydrogel electrolyte. The ECD containing the uniformly cross‐linked hydrogel showed good result in electrochromic switching performance. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1305–1308, 2002     

Optical and electronic properties of thin films and solutions of functionalized forms of graphene and related carbon materials

With the advent of many different forms of graphene (in addition to the long standing interest in fullerenes and carbon nanotubes), the characterization of carbon materials and their degree of conjugation is a particularly important topic in carbon science. We report the application of absorption spectroscopy and conductivity measurements to graphene derivatives and related carbon materials. Reduced graphene oxide (RGO) has been widely studied as a promising material for graphene applications because of its processability, and the same considerations apply to graphene functionalized with octadecylamine (ODA). This study utilizes a direct chemical modification of GO with ODA in the presence of dicyclohexylcarbodiimide to partially regenerate the graphene π-conjugation while producing a material (ODA-G) with excellent solubility in organic solvents. We show that the ODA-G exhibits optical absorptions, which are much stronger than those of GO, and comparable to liquid phase exfoliated graphene and reduced graphene oxide; the optical analysis is unified by the development of an analytical relationship between solid state absorption coefficients and solution state extinction coefficients, which allows the direct comparison of the electronic absorption spectroscopy of films and solutions of carbon materials. We further benchmark the regeneration of the graphenic structure in ODA-G with electrical conductivity measurements.     

XAFS measurement of gallium in DLC thin film fabricated by FIB-CVD method

We measured the florescence X-ray absorption fine structure (XAFS) spectra of gallium atoms in a diamond-like carbon (DLC) thin film deposited by focused ion beam-chemical vapor deposition (FIB-CVD). Ga K-edge XAFS spectra were measured by monitoring the Ga Kα line in the energy range of 9.9–11.5 keV. The radial distribution function was calculated from the Fourier transform of the extended X-ray absorption fine structure (EXAFS) oscillation that had been obtained by appropriately removing the background and normalization. The peak due to the carbon atoms nearest the central gallium atom was at 1.6 Å. A comparison of the experimentally measured EXAFS oscillation and one calculated by single scattering theory indicated that the coordination number around the central gallium atom and the interatomic distance between the central gallium atom and the carbon atom were ≈ 6.4 and ≈ 2.6 Å, respectively. The interatomic distances for FIB-CVD DLC thin films annealed for 1 h at 200 °C and at 400 °C were the same as the as-deposited film.     

Electron transfer behaviour of single-walled carbon nanotubes electro-decorated with nickel and nickel oxide layers

The electron transfer behaviour of nickel film-decorated single-walled carbon nanotubes (SWCNTs-Ni) at edge plane pyrolytic graphite electrodes (EPPGEs) was investigated. The impact of SWCNTs on the redox properties of the nickel film was investigated with cyclic voltammetry and electrochemical impedance spectroscopy (EIS). From EIS data, obtained using ferrocyanide/ferricyanide as a redox probe, we show that the electrodes based on nickel and nickel oxide films follow electrical equivalent circuit models typical of partial charge transfer or adsorption-controlled kinetics, resembling the “electrolyte-insulator-semiconductor sensors (EIS)”. From the models, we prove that EPPGE-SWCNT-Ni exhibits the least resistance to charge transport compared to other electrodes (approximately 30 times faster than the EPPGE-SWCNT-NiO, 25 times faster than EPPGE-SWCNT, and over 300 times faster than the bare EPPGE) suggesting the ability of the SWCNTs to act as efficient conducting species that facilitate electron transport of the integrated nickel and nickel oxide particles.     

Surface grafting of polymer onto carbon thin film

The surface grafting of polymers onto carbon thin film deposited on a glass plate was achieved by two methods: the graft polymerization initiated by initiating groups introduced onto the surface; and the trapping of polymer radicals by surface aromatic rings of the thin film. It was found that the radical and cationic graft polymerization of vinyl monomers are initiated by azo and acylium perchlorate groups introduced onto the surface, respectively, and the corresponding polymers are grafted onto the surface: the surface grafting of polymers were confirmed by the contact angle of the surface with water. In addition, the anionic ring-opening alternating copolymerization of epoxides with cyclic acid anhydrides was found to be initiated by potassium carboxylate groups on the carbon thin film to give the corresponding polyester-grafted carbon thin film. On the other hand, polymer radicals formed by the decomposition of azo polymer, such as poly(polydimethylsiloxane-azobiscyanopentanoate) and poly(polyoxyethylene-azobiscyanopentanoate), were successfully trapped by the surface aromatic rings of carbon thin film and polydimethylsiloxane and polyoxyethylene were grafted onto the surface. © 1995 John Wiley & Sons, Inc.     

Deposition of a thin film of carbon nanotubes onto a glassy carbon electrode by electropolymerization

A novel and easy route for the deposition of a thin film of carbon nanotubes onto an electrode surface by electropolymerization is described. Multi-wall carbon nanotubes (MWNTs) were “dissolved” in aqueous alizarin red S (ARS, 3,4-dihydroxy-9,10-dioxo-2-anthracenesulfonic acid, sodium salt) solution, and a very stable and well-distributed aqueous MWNTs–ARS solution was obtained. A thin film of MWNTs–ARS was successfully deposited onto the electrode surface by an in situ electropolymerization in aqueous MWNTs–ARS solution. The MWNTs–ARS thin film was characterized by scanning electron microscopy, Raman spectroscopy, UV–Vis spectroscopy and electrochemical techniques.     

Effect of the liquid environment on the formation of carbon nanotubes and graphene layers by arcing processes

The influence of the liquid environment on the formation of different carbon nanostructures by arcing processes, in particular liquid nitrogen (LN₂) and de-ionised water (DI-H₂O), has been investigated. Large structural differences between the nanomaterials produced in the two cases are shown: the use of DI-H₂O induces a large number of pentagon–heptagon defects in the nanotubes, compared to the use of LN₂. A large amount of graphene layers has been observed by scanning electron microscopy and transmission electron microscopy in the case of arc discharge in DI-H₂O. Micro-Raman analysis confirms the electron microscopy results.     

Qualitative measurement of residual carbon in wet-chemically synthesized powders

Sodium niobate powders were prepared by the polymerizable complex (PC) method using a water-soluble Nb–malic acid complex and sodium carbonate. Niobium oxide pentahydrated was dissolved in hot oxalic acid (OA) solution, followed by the addition of NH₃ (30%) until pH 11, precipitating niobic-acid that was added into a solution of -malic acid (MA) at mole ratio of [MA]:[Nb]=2:1. Na₂CO₃ was added in the mole ratio [Na]:[Nb]=1:1, and the solvent was eliminated at 70 °C, forming a yellow gel without any segregation. The gel was calcined at 300 °C for 3 h, and the (Na---Nb---MA) heated material was calcined in the range of temperatures from 400 to 900 °C, from 5 min to 8 h. Pure NaNbO₃ (NN), free from amorphous carbon, which crystallized at temperatures higher than 450 °C, was confirmed by a combined analysis using X-ray diffraction and UV–Raman spectroscopy. A correlation between the presence of residual carbon and the crystallite size, which was calculated using the Scherrer formula, was observed and qualitatively used to infer about this presence of residual carbon.     

Study on SiC layers synthesized with carbon ion beam at low substrate temperature

Carbon implantation into silicon, at beam energies from 30 to 60 keV and at ion doses of 3.0×10¹⁷ to 1.6×10¹⁸cm⁻² with a metal vapor vacuum arc ion, was performed to form SiC layers at substrate temperatures below 400°C. It was found that the substrate temperature for the conversion of amorphous phase SiC (a-SiC) into cubic phase SiC (β-SiC) during the carbon implantation, is much lower than the conversion temperature (approx. 900°C) of a-SiC into β-SiC induced by the post-annealing. The feature of the low substrate temperature of the metal vapor vacuum arc (MEVVA) ion source is thought to be due to the ion-beam-induced crystallization (IBIC) effect. The profile of the carbon content, which is of Gaussian shape similar to the data of TRIM-90 calculation, is associated well with the distribution of the ratio of [relative amount of β-SiC/relative amount of a-SiC] in the SiC layers. Moreover, in the carbon rich region the higher degree of crystallization is attributed to the higher β-SiC fraction.     

Bright nickel film deposited by supercritical carbon dioxide emulsion using additive-free Watts bath

This paper is aimed on studying film smoothening effect of supercritical carbon dioxide emulsion (Sc-CO₂-E) on nickel film electroplated using an additive-free Watts bath. Morphology of nickel film electroplated with Sc-CO₂-E was found to be similar to that of nickel film prepared from electroless plating. Surface roughness (R_a) of nickel film electroplated with Sc-CO₂-E was lower than that of nickel film electroplated through conventional method. A minimum R_a was found for nickel film electroplated through conventional method and Sc-CO₂-E when increasing current density from 0.010 to 0.150 A/cm². The minimum R_a was 69.8 nm at 0.020 A/cm² and 14.0 nm at 0.030 A/cm², respectively for conventional and Sc-CO₂-E case. After the minimum point, increasing rate of R_a increased was lower for Sc-CO₂-E case; this was because of higher hydrogen solubility in Sc-CO₂. Grain size of nickel film electroplated with Sc-CO₂-E was found to be finer than that of conventional case.