Gas sensor properties of zno nanorods grown by chemical bath deposition

The present work shows a study about the growing of ZnO nanorods by chemical bath deposition (CBD) and its application as gas sensor. It was prepared ZnO nanorods and Au decorated ZnO nanorods and the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and gas sensing response measurements. The results obtained by XRD show the growth of ZnO phase. It was possible to observe the formation of uniform dense well-aligned ZnO nanorods. The results obtained also revealed that Ag nanoparticles have decorated the surface of ZnO nanorods successfully. Au nanoparticles with diameter of a few nanometers were distributed over the ZnO surface nanorods. The gas sensing response measurements showed a behavior of n type semiconductor. Furthermore, the Au-functionalized ZnO nanorods gas sensors showed a considerably enhanced response at 250 and 300 °C.

Micromorphologic assessment of CVD (chemical vapor deposition) and conventional diamond tips and their cutting effectiveness

The aim of this study was to compare the micromorphology of CVD diamond tips coupled to ultrasound with conventional high speed diamond tips after cavity preparations, and to measure the width and depth of the cavities obtained. Two hundred bovine teeth were divided into 20 subgroups. Each of the diamond tips (10 CVD and 10 conventional) were used to prepare 10 standardized cavities, using an apparatus that controlled the time (t: 27 s), speed (5.3 mm/s) and load (0.012 KGF) of the tip against the teeth during preparation. The unused and the used (after one, five and 10 preparations) tips were analyzed by scanning electronic microscopy. The images were randomly assessed by 3 examiners with regard to the presence or absence of micromorphologic alterations. Cavity measurements were made after visualization under a stereoscopic microscope. Cavity widths and depths were analyzed by the ANOVA Factorial test (p < 0.05). The CVD diamond tips presented less wear than the conventional tips after all the cavity preparations performed, but produced shallower cavities that were equivalent in width to those made by conventional tips after the fifth preparation. CVD diamond tips may be suggested as an alternative to conventional diamond tips due to their conservative preparation and greater longevity.

Dielectric properties of Ca(Zr0.05Ti0.95)O-3 thin films prepared by chemical solution deposition

Ca(Zr0.05Ti0.95)O-3 (CZT) thin films were grown on Pt(1 1 1)/Ti/SiO2/Si(1 0 0) substrates by the soft chemical method. The films were deposited from spin-coating technique and annealed at 928 K for 4 h under oxygen atmosphere. CZT films present orthorhombic structure with a crack free and granular microstructure. Atomic force microscopy and field-emission scanning electron microscopy showed that CZT present grains with about 47 nm and thickness about 450 nm. Dielectric constant and dielectric loss of the films was approximately 210 at 100 kHz and 0.032 at 1 MHz. The Au/CZT/Pt capacitor shows a hysteresis loop with remnant polarization of 2.5 mu C/cm(2), and coercive field of 18 kV/cm, at an applied voltage of 6 V. The leakage current density was about 4.6 x 10(-8) A/cm(2) at 3 V. Dielectric constant-voltage curve is located at zero bias field suggesting the absence of internal electric fields. (c) 2006 Elsevier B.V. All rights reserved.

SrBi2(Ta0.5Nb0.5)(2)O-9 : W thin films obtained by chemical solution deposition: Morphological and ferroelectric characteristics

The effect of tungsten (W6+) ion substituting on dielectric and ferroelectric behavior in SrBi2(Ta0.5Nb0.5)(2)O-9 (SBTN) thin films prepared by polymeric precursor method was investigated at room temperature. The addition of W6+ ion in the SBTN lattice was evaluated by X-ray diffraction (XRD), microstructural and dielectrical properties. An increase in the grain size is evident when tungsten is introduced in the SBTN lattice. Substitution of tungsten until 10% on B site leads to introduce space charge polarization into the system, resulting in an appreciable decrease in both dielectric constant and tangent loss. The morphology of the thin films investigated by atomic force microscopy leads to an increase in the grain size after tungsten addition. Fatigue resistance was noted with increase in tungsten addition. (C) 2007 Elsevier B.V. All rights reserved.

Photoluminescence at room temperature in amorphous SrTiO3 thin films obtained by chemical solution deposition

Intense photoluminescence in highly disordered strontium titanate amorphous thin films prepared by the polymeric precursor method was observed at room temperature (300 K). The luminescence spectra of SrTiO3 amorphous thin films at room temperature revealed an intense single-emission band in the visible region. X-ray absorption near edge structure was used to probe the local atomic structure of SrTiO3 amorphous and crystalline thin films. Photoluminescence intensity in the 535 nm range was found to be correlated with the presence of non-bridging oxygen defects. A discussion is presented of the nature of this photoluminescence, which may be related to the disordered structure in SrTiO3 amorphous thin films. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Chemical vapor deposition of multi-walled carbon nanotubes from nickel/yttria-stabilized zirconia catalysts

Multi-walled carbon nanotubes (MWNT) were produced by chemical vapor deposition using yttria-stabilized zirconia/nickel (YSZ/Ni) catalysts. The catalysts were obtained by a liquid mixture technique that resulted in fine dispersed nanoparticles of NiO supported in the YSZ matrix. High quality MWNT having smooth walls, few defects, and low amounts of by-products such as amorphous carbon were obtained, even from catalysts with large Ni concentrations (> 50 wt.%). By adjusting the experimental parameters, such as flux of the carbon precursor (ethylene) and Ni concentration, both the MWNT morphology and the process yield could be controlled. The resulting YSZ/Ni/MWNT composites can be interesting due to their mixed ionic-electronic transport properties, which could be useful in electrochemical applications.

Microstructural and transport properties of LaNiO3-delta films grown on Si(111) by chemical solution deposition

Electrically conductive LaNiO3-delta (LNO) thin films with typical thickness of 200 nm were deposited on Si (111) substrates by a chemical solution deposition method and heat-treated in air at 700 degreesC. Structural, morphological, and electrical properties of the LNO thin films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), field-emission scanning electron microscopy (FEG-SEM), and electrical resistivity rho(T). The thin films have a very flat surface and no droplet was found on their surfaces. The average grain size observed by AFM and FEG-SEM was approximately 100 nm in excellent agreement with XRD data. The rho(T) data showed that these thin films display a good metallic character in a large range of temperature. These results suggest the use of this conductive layer as electrode in the integration of microelectronic devices. (C) 2003 Elsevier B.V. All rights reserved.

Ferroelectric characteristics of BiFeO3 thin films prepared via a simple chemical solution deposition

BiFeO3 (BFO) thin films were fabricated on Pt(111)/Ti/SiO2/Si substrates by using a polymeric precursor solution under appropriate crystallization conditions. The capacitance dependence on voltage is strongly nonlinear, confirming the ferroelectric properties of the films resulting from the domain switching. The leakage current density increases with annealing temperature. The polarization electric field curves could be obtained in BFO films annealed at 500 degrees C, free of secondary phases. X-ray photoelectron spectroscopy spectra of films annealed at 500 degrees C indicated that the oxidation state of Fe was purely 3+, demonstrating that our films possess stable chemical configurations. (c) 2007 American Institute of Physics.

Plasma enhanced chemical vapor deposition of titanium(IV) ethoxide-oxygen-helium mixtures

Thin films were deposited by plasma enhanced chemical vapor deposition from titanium (IV) ethoxide (TEOT)-oxygen-helium mixtures. Actinometric optical emission spectroscopy was used to obtain the relative plasma concentrations of the species H, CH, O and CO as a function of the percentage of oxygen in the feed, R(ox). The concentrations of these species rise with increasing R(ox) and tend to fall for R(ox) greater than about 45%. As revealed by a strong decline in the emission intensity of the actinometer Ar as R(ox) was increased, the electron mean energy or density (or both) decreased as greater proportions of oxygen were fed to the chamber. This must tend to reduce gas-phase fragmentation of the monomer by plasma electrons. As the TEOT flow rate was fixed, however, and since the species H and CH do not contain oxygen, the rise in their plasma concentrations with increasing R(ox) is explained only by intermediate reactions involving oxygen or oxygen-containing species. Transmission infrared (IRS) and X-ray photoelectron (XPS) spectroscopies were employed to investigate film structure and composition. The presence of CH(2), CH(3), C=C, C-O and C=O groups was revealed by IRS. In addition, the presence of C-O and C=O groups was confirmed by XPS, which also revealed titanium in the +4 valence state. The Ti content of the films, however, was found to be much less than that of the monomer material itself. (C) 2007 Elsevier B.V. All rights reserved.

Characterization of Si : O : C : H films fabricated using electron emission enhanced chemical vapour deposition

Silicon-based polymers and oxides may be formed when vapours of oxygen-containing organosilicone compounds are exposed to energetic electrons drawn from a hot filament by a bias potential applied to a second electrode in a controlled atmosphere in a vacuum chamber. As little deposition occurs in the absence of the bias potential, electron impact fragmentation is the key mechanism in film fabrication using electron-emission enhanced chemical vapour deposition (EEECVD). The feasibility of depositing amorphous hydrogenated carbon films also containing silicon from plasmas of tetramethylsilane or hexamethyldisiloxane has already been shown. In this work, we report the deposition of diverse films from plasmas of tetraethoxysilane (TEOS)-argon mixtures and the characterization of the materials obtained. The effects of changes in the substrate holder bias (Vs) and of the proportion of TEOS in the mixture (XT) on the chemical structure of the films are examined by infrared-reflection absorption spectroscopy (IRRAS) at near-normal and oblique incidence using unpolarised and p-polarised, light, respectively. The latter is particularly useful in detecting vibrational modes not observed when using conventional near-normal incidence. Elemental analyses of the film were carried out by X-ray photoelectron spectroscopy (XPS), which was also useful in complementary structural investigations. In addition, the dependencies of the deposition rate on Vs and XT are presented. (c) 2007 Elsevier B.V. All rights reserved.

Diverse Amorphous Carbonaceous Thin Films Obtained by Plasma Enhanced Chemical Vapor Deposition and Plasma Immersion Ion Implantation and Deposition

Diverse amorphous hydrogenated carbon and similar films containing additional elements were produced by Plasma Enhanced Chemical Vapor Deposition (PECVD) and by Plasma Immersion Ion Implantation and Deposition (PIIID). Thus a-C:H, a-C:H:F, a-C:H:N, a-C:H:Cl and a-C:H:O:Si were obtained, starting from the same feed gases, using both techniques. The same deposition system supplied with radiofrequency (RF) power was used to produce all the films. A cylindrical stainless steel chamber equipped with circular electrodes mounted horizontally was employed. RF power was fed to the upper electrode; substrates were placed on the lower electrode. For PIIID negative high tension pulses were also applied to the lower electrode. Raman spectroscopy confirmed that all the films are amorphous. Chemical characterization of each pair of films was undertaken using Infrared Reflection Absorption Spectroscopy and X-ray Photoelectron Spectroscopy. The former revealed the presence of specific structures, such as C-H, C-O, O-H. The latter allowed calculation of the ratio of hetero-atoms to carbon atoms in the films, e. g. F:C, N:C, and Si:C. Only relatively small differences in elemental composition were detected between films produced by the two methods. The deposition rate in PIIID is generally reduced in relation to that of PECVD; for a-C:H:Cl films the reduction factor is almost four.

Development of chemical vapor deposition diamond burrs using hot filament

The fabrication of boring tools (burrs) for dentistry with the use of a hot-filament chemical vapor deposition (CVD) system, to form the diamond abrading structure, is reported here. The diamond was synthesized from a methane/freon gas mixture diluted in hydrogen. Comparative drilling tests with conventional diamond burrs and the CVD diamond burrs in borosilicate glasses demonstrated a lifetime more than 20 times larger for the CVD diamond burrs. Also, heat flow experiments in dentine showed that the CVD diamond burrs induce temperature gradients of the same order as the conventional ones. These characteristics of the CVD diamond burrs are highly desirable for odontological applications where the burrs' lifetime and the low temperature processing are essential to the quality and comfort of the treatment. © 1996 American Institute of Physics.

Properties of BaBi2Ta2O9 thin films prepared by chemical solution deposition technique for dynamic random-access memory applications

We report on the properties of BaBi2Ta2O9 (BBT) thin films for dynamic random-access memory (DRAM) and integrated capacitor applications. Crystalline BBT thin films were successfully fabricated by the chemical solution deposition technique on Pt-coated Si substrates at a low annealing temperature of 650°C. The films were characterized in terms of structural, dielectric, and insulating properties. The electrical measurements were conducted on Pt/BBT/Pt capacitors. The typical measured small signal dielectric constant and dissipation factor, at 100 kHz, were 282 and 0.023, respectively, for films annealed at 700°C for 60 min. The leakage current density of the films was lower than 10-9 A/cm2 at an applied electric field of 300 kV/cm. A large storage density of 38.4 fC/μm2 was obtained at an applied electric field of 200 kV/cm. The high dielectric constant, low dielectric loss and low leakage current density suggest the suitability of BBT thin films as dielectric layer for DRAM and integrated capacitor applications.

Temperature and stoichiometry effect on microstructural and ferroelectric properties of Pb(Zr1-xTix)O3 thin films prepared by chemical soulution deposition

Lead zirconate titanate (PZT) solutions were prepared using a polymeric precursor method, Zr n-propoxide and Ti i-propoxide were used as starting materials with ethylene glycol and water as solvents. The PZT solution was spin-coated on Pt/Ti/SiO2/Si substrates, baked on a hot plate, and finally heat-treated in a tube furnace between 400 and 800°C. The surface morphology and grain size of the films were characterized by atomic force microscopy (AFM), using a tapping mode with amplitude modulation. The films, thermal annealed at temperatures higher than 500°C, exhibited a dense microstructure, without noticeable cracks or voids. Electrical properties were investigated as a function of composition and annealing temperature.

Influence of the network modifier on the characteristics of MSnO 3 (M=Sr and Ca) thin films synthesized by chemical solution deposition

CaSnO3 and SrSnO3 alkaline earth stannate thin films were prepared by chemical solution deposition using the polymeric precursor method on various single crystal substrates (R- and C-sapphire and 100-SrTiO3) at different temperatures. The films were characterized by X-ray diffraction (θ-2θ, ω- and φ-scans), field emission scanning electron microscopy, atomic force microscopy, micro-Raman spectroscopy and photoluminescence. Epitaxial SrSnO3 and CaSnO 3 thin films were obtained on SrTiO3 with a high crystalline quality. The long-range symmetry promoted a short-range disorder which led to photoluminescence in the epitaxial films. In contrast, the films deposited on sapphire exhibited a random polycrystalline growth with no meaningful emission regardless of the substrate orientation. The network modifier (Ca or Sr) and the substrate (sapphire or SrTiO3) influenced the crystallization process and/or the microstructure. Higher is the tilts of the SnO6 octahedra, as in CaSnO3, higher is the crystallization temperature, which changed also the nucleation/grain growth process. © 2012 Elsevier Inc. All rights reserved.