Type Of Metal Electrode Research Articles

Enhancing the performance of TiO2 nanotube-based hydrogen sensors through crystal structure and metal electrode

In this research, the effect of metal electrodes and crystalline phase on gas detection of titanium dioxide (TiO2) nanotube-based hydrogen (H2) sensors was investigated. TiO2 nanotubes were produced using glycerol-based electrolyte and annealed at 300 °C and 700 °C to change the anatase and rutile crystalline phases, respectively. TiO2 nanotubes were coated by platinum (Pt), palladium (Pd), gold (Au) and silver (Ag) electrodes to fabricate metal/TiO2 nanotubes Ti H2 sensor devices and then the current-voltage (I–V) characteristics were investigated at room temperature. The structural properties of TiO2 nanotubes were characterized by SEM, FE-SEM, XRD, and Raman techniques. The H2 detection properties of the sensors were examined at the 1000 ppm - 5% H2 concentration range. The crystal structure and metal electrodes are the main factors that affect the H2 sensing properties of TiO2 nanotube-based sensors. The effect of crystal forms on sensitivity was not the same as for metal electrodes. The underlying sensing mechanisms for different types of metal electrodes and crystal structures are discussed and the relevance of their sensing performance to nanotubes and electronic properties is investigated. In addition, discussion of each metal electrode and crystal structure will make important contributions to the development of H2 sensors. The Pd-coated device annealed at 700 °C showed the best detection performance.

Precipitation Patterns in Reaction–Diffusion–Reaction Systems of Prussian Blue and Cu–Fe-Based Prussian Blue Analogs

In agarose gel containing [Fe(CN)6]3‒ions and sandwiched between two metal rods (Ti, Fe, or Cu) with a voltage of 1‒5 V applied for 20–100 h, reaction–diffusion–reaction (RDR) processes (that is, electrochemical reactions at metal rods to generate reactant ions, diffusion of the reactant ions influenced by the electric field in agarose gel, and reactions of the reactant ions to form/decompose precipitates) were coupled to generate diverse precipitation patterns of Prussian blues (PB) or Cu–Fe-based Prussian blue analogs (Cu–Fe PBA). These patterns strongly depended on the type of metal electrode, applied voltage, initial [Fe(CN)6]3‒concentration, and elapsed time after voltage application. Under the application of 2 V for 20/50 h, the PB/Cu–Fe PBA formed a discrete precipitation band on the anode/cathode side in an agarose gel containing 0.050 M [Fe(CN)6]3‒ions. In the Cu–Fe PBA system, a relatively long precipitation band of Cu(OH)2was also generated on the anode side by OH−ions produced on the cathode as a byproduct. Longer voltage applications promoted propagation of the Cu–Fe PBA band to the anode side and caused the discrete PB band to disappear. Higher initial [Fe(CN)6]3‒concentrations deepened the color of the generated patterns. Higher voltage applications suppressed the propagation of the Cu–Fe PBA band to the anode side and caused the PB band to disappear. Experiments using a Ti cathode suggested that the formation and subsequent decomposition of PB or Cu–Fe PBA at the cathode surface are important for forming precipitation band(s) in the gel near the cathode. The application of cyclic alternating voltages (particularly, 4 V for 1 h and 1 V for 4 h) was effective in generating Liesegang-band-like periodic bands, particularly for the Cu–Fe PBA system.

CO2 Photoelectrochemical Reduction Catalyzed by a GaP(001) Photoelectrode

Several types of metal electrodes (especially copper) can catalyze electrochemical CO2 reduction. Among semiconductor electrodes for CO2 photoelectroreduction, GaP electrodes exposing (111) and (11...

Construction of novel electrochemical treatment systems for indigo wastewater and their performance

PurposeThis study aims to evaluate the efficiency of metal electrode and electrolytes on the electroflocculation of indigo wastewater, produced by printing and dyeing factory, and to optimize the treatment system.Design/methodology/approachFor effective purging, various types of metal electrodes (graphite, pure aluminum and stainless steel) and supporting electrolytes (sodium chloride and sodium sulfate) were selected for electroflocculation experiments. The decolorization rate and chemical oxygen demand (COD) removal rate were characterized.FindingsThe treatment effects of stainless steel and aluminum were similar, but the dissolution loss of aluminum and the production of flocs greatly limit its application. Electrolytes gave obvious effects to these systems. Sodium sulfate was better than sodium chloride, the decolorization rate was increased by 3.31%, the removal rate of COD in the solution was increased by 28.65% and the weight of flocculation precipitation was reduced by 0.214 g.Research limitations/implicationsThe electrochemical treatment system was constructed to compare and analyze the influence of experimental parameters and to provide a reference for the actual treatment of indigo wastewater.Practical implicationsElectrochemical flocculation can remove the insoluble indigo solids and it plays a key role in wastewater treatment.Originality/valueIt is novel to optimize the combination of electrode and electrolyte to improve the efficiency of electroflocculation, which can be widely used in the actual wastewater treatment process.

Influence of metal electrodes on c‐axis orientation of AlN thin films deposited by DC magnetron sputtering

Nanocrystalline aluminum nitride (AlN) thin films were deposited on two types of metallic seed layers on silicon substrates, (111) textured Pt and (110) Mo, by reactive DC magnetron sputtering at low temperature (200 °C). Both textured films of Pt and Mo promote nucleation, thereby improving the crystallinity and epitaxial growth condition for AlN thin films. The deposited films were examined by X‐ray diffraction, scanning electron microscopy and atomic force microscopy techniques. The results indicated that the preferred orientation of crystallites greatly depends upon the kinetic energy of the sputtered species (target power) and seed layers used. Furthermore, AlN thin films with c‐axis perpendicular to the substrate grew on both types of metal electrodes at all power levels larger than 100 W. By comparing the structural properties and compressive stresses at perfect c‐axis orientation conditions, it is evident that AlN films deposited on (110) oriented Mo substrates exhibited superior properties as compared with Pt/Ti seed layers. Furthermore, less values of compressive stresses (−3 GPa) as compared with Pt/Ti substrates (−7.08 GPa) make Mo preferentially better candidate to be employed in the field of suspended Micro/Nano ‐ electromechanical systems (MEMS/NEMS) for piezoelectric devices. Copyright © 2017 John Wiley & Sons, Ltd.

Consideration of conduction mechanisms in high-k dielectric stacks as a tool to study electrically active defects

In this paper conduction mechanisms which could govern the electron transport through high-k dielectrics are summarized. The influence of various factors - the type of high-k dielectric and its thickness; the doping with a certain element; the type of metal electrode as well as the measurement conditions (bias, polarity and temperature), on the leakage currents and dominant conduction mechanisms have been considered. Practical hints how to consider different conduction mechanisms and to differentiate between them are given. The paper presents an approach to assess important trap parameters from investigation of dominant conduction mechanisms.

Electrode effect on high-detectivity ultraviolet photodetectors based on perovskite oxides

High-detectivity metal-semiconductor-metal ultraviolet photodetectors have been fabricated based on SrTiO3 with different types of metal electrodes (Ag, Ni, and Pt), and the effects of the different types of the electrodes on the photoelectric properties were investigated. Comparing with three types of the metal electrodes, the largest responsivity of 0.517 A/W and the smallest dark current of 2.215 × 10−11 A were obtained by using Ag electrode due to the largest Schottky barrier between Ag electrode and SrTiO3. The detectivities of all the photodetectors are achieved about 1012 cm·HZ1/2/W, which can be comparable to Si-based photodetectors. Furthermore, a transient photovoltaic signal with a rise time of ∼360 ps and a full width at half-maximum of ∼576 ps are obtained in the Ag/SrTiO3/Ag photodetectors under the illumination of a 355 nm laser with 15 ps duration. These results provide a useful guide for designing high-performance photodetectors based on perovskite oxides and the appropriate metal electrode selected.

Effect of Electrode Types on the Resistive Switching Behavior of Titania Thin Films

The resistive switching or memristive behavior of sputtered titania thin films sandwiched in between of three types of metal electrodes (Au, Pt and Ti) was investigated. The active region of the device consisted of two titania thin films, in which, the first layer was exposed to a plasma treatment to create the oxygen vacancies, before the deposition of the second layer. The whole active layer sputtering deposition process was conducted in a one-flow process without exposing the sample to the room ambient. From the I-V measurements, titania thin films in between Ti and Au did not show any resistive switching, but those sandwiched between Pt electrodes exhibit a noticeable memristive behavior. This may due to the metal work function of the platinum itself.

Metal-Semiconductor Contact Behavior of Solution-Processed ZnSnO Thin Film Transistors

We studied the influence of different types of metal electrodes on the performance of solution-processed zinc tin oxide (ZTO) thin-film transistors. The ZTO thin-film was obtained by spin-coating the sol-gel solution made from zinc acetate and tin acetate dissolved in 2-methoxyethanol. Various metals, Al, Au, Ag and Cu, were used to make contacts with the solution-deposited ZTO layers by selective deposition through a metal shadow mask. Contact resistance between the metal electrode and the semiconductor was obtained by a transmission line method (TLM). The device based on an Al electrode exhibited superior performance as compared to those based on other metals. Kelvin probe force microscopy (KPFM) allowed us to measure the work function of the oxide semiconductor to understand the variation of the device performance as a function of the types metal electrode. The solution-processed ZTO contained nanopores that resulted from the burnout of the organic species during the annealing. This different surface structure associated with the solution-processed ZTO gave a rise to a different work function value as compared to the vacuum-deposited counterpart. More oxygen could be adsorbed on the nanoporous solution-processed ZTO with large accessible surface areas, which increased its work function. This observation explained why the solution-processed ZTO makes an ohmic contact with the Al electrode.

Positioning of the Fermi Level in Graphene Devices with Asymmetric Metal Electrodes

To elucidate the effect of the work function on the position of the Dirac point, we fabricated graphene devices with asymmetric metal contacts. By measuring the peak position of the resistance for each pair of metal electrodes, we obtained the voltage of the Dirac point (V) from the gate response. We found that the position of (V) in the hybrid devices was significantly influenced by the type of metal electrode. The measured shifts in (V) were closely related to the modified work functions of the metal‐graphene complexes. Within a certain bias range, the Fermi level of one of the contacts aligned with the electron band and that of the other contact aligned with the hole band.

Influence of metal work function on the position of the Dirac point of graphene field-effect transistors

We studied the effect of metal contact on the position of the Dirac point by means of transport measurements. To determine the sole effect of metal contact, we prepared more than 100 graphene devices following the same fabrication procedure and with a device layout that differed only in the type of metal electrode used. By measuring the peak position of the resistance, the Dirac points (VgDirac) were recorded in the gate response. The work function of metal-graphene complex was found to be a fair phenomenological indicator of the location of VgDirac in the transfer response.

無電解めっきにおける次亜りん酸ナトリウムのアノード酸化に対する金属の触媒活性

The anodic oxidation of hypophosphite on nickel, palladium, platinum, gold and cobalt electrodes in sodium citrate solution was studied with special attention to the catalytic activity of the metals in electroless plating. The polarization curves exhibited the current peaks, that were probably attributable to the formation of anodic films on the electrode surface at noble potentials. The anodic currents of the ascending portion of the polarization curves increased with increases either the pH value or the concentration of hypophosphite. The reaction orders in regard to the concentrations of hyphosphite and hydroxyl ion were approximately 0.5 and 0.2 respectively, and were dependent to some extent on the type of metal electrode. The relative catalytic activity of the metals, evaluated by the potential values at an anodic current density of 1.0×10-4A/cm2, decreases in the order Au, Ni, Pd, Co and Pt. Anodic oxidation of hypophosphite did not occur on Cu and Ag electrodes. The apparent activation energies for the anodic reaction were 7.9, 11, 13, 21 and 14kcal/mol for Au, Ni, Pd, Co and Pt respectively. Thus, the activation energy of the metals in the anodic oxidation of hypophosphite increases in descending order of their catalytic activity.

Tunneling in Ultrathin Glass Films

Ultrathin phosphosilicate glass films have been formed on degenerate n-type Si wafers in a high temperature vapor transport process. The glass thickness (determined ellipsometrically) could be controllably varied in the range from 30 to 100 A. A quadratic dependence of the glass thickness vs growth time was observed in most cases. This dependence indicates that the glass film forms via a diffusion-controlled reaction. After depositing metal electrodes on the glass, the tunneling current was studied down to temperatures of about 1.5 K. The thickness dependence of the junction resistance was measured and an estimate of the tunneling barrier height was obtained. It will be shown that the barrier height depends on the history of the samples. Structures in the i-v curve are discussed in terms of properties of the glass film and the type of metal electrode.