Cathodic Phase Research Articles

Analysis of compound action potentials elicited with specific current stimulating pulses in an isolated rat sciatic nerve.

The ability to selectively stimulate Aα, Aβ-fibers and Aδ-fibers in an isolated rat sciatic nerve (SNR) was assessed. The stimulus used was a current, biphasic pulse with a quasitrapezoidal cathodic phase and rectangular anodic phase where parameters were systematically varied: intensity of the cathodic phase (ic); width of the cathodic phase (tc); width of the cathodic exponential decay (texp) and time constant of the exponential decay (τexp). A SNR was stimulated using a pair of hook electrodes while conduction velocity (CV) and compound action potentials (CAP) were measured at two sites along the SNR using another two pairs of electrodes. Results showed that the highest CAP1 (8.5-9 mV), shall be expected when parameters of the stimulus were within the following range: ic=3.8-4 mA, tc=350-400 μs and texp=330-440 μs. Results also showed that with ascending tc and texp, CV of the corresponding superficial region of the SNR was reduced in both, conduction velocity of CAP1 and conduction velocity of CAP2. It was concluded that action potentials (APs) were activated in the Aβ-fibers and Aδ-fibers along with a slight AP inhibition in the Aβ-fibers. The obtained results, could serve as a tool for developing multi-electrode systems that potentially enable fiber-type selective stimulation of nerve fibers.

Effect of Zn Existence on Mg Corrosion Due to Cu

INTRODUCTION Mg alloys are attractive materials due to its lightness and excellent mechanical properties. Recycling of Mg alloy is meaningful because secondary Mg alloy is produced with few energy than its virgin metal. However, secondary Mg alloy easily contains some impurities elements which degrade the corrosion property. Cu is one of undesirable impurities, and its tolerance limit is 1000 ppm in pure Mg. Since it is difficult to remove Cu from Mg alloy because of it chemical affinity with Mg, another method to reduce the harmful influence of Cu must be considered.In this study, the corrosion behaviors of Mg-Cu and Mg-Zn-Cu were investigated, and the inhibitory effect on Mg corrosion due to Cu by Zn was discussed. EXPERIMENTAL PROCEDURE Mg-Zn, Mg-Cu and Mg-Zn-Cu alloys shown in Table 1 were prepared by electric furnace. The specimens were immersed for 1h, 2h, 4h and 6h in 5 mass% NaCl solution, and the specimens before and after the immersion test were observed and analyzed by OM, SEM-EDX and XRD. The corrosion rate were also estimated by polarization measurement. RESULTS AND DISCUSSION Mg2Cu was detected by XRD in the Mg-Cu specimens, while the peak of Mg21Zn25 was observed in the Mg-Zn and the Mg-Zn-Cu specimens. Fig.1 shows the SEM images and the element distributions of the Mg-6mass%Zn-0.1mass%Cu specimens by EDX. In the specimens, the deposits containing Mg and Zn were seen, and Cu was condensed locally in the deposit. Considering the results of XRD and EDX, Mg21Zn25 containing Cu was formed.After the immersion test for 1h, local corrosion was observed in the Mg-Cu and the Mg-Zn-Cu specimens by OM. The deposits remained on the surface, while the matrix around the deposit was corroded. This result indicates that the micro-galvanic corrosion occurred and that the deposit acted a cathodic phase. Only local corrosion was seen in the Mg-Cu specimens, while general corrosion occurred on the Mg-Zn-Cu specimens. After the immersion test for 6h, general corrosion were seen in all the specimen.The corrosion rates of the specimens were estimated by polarization measurement as shown Fig.2. The more the Cu content was, the bigger the corrosion rate became. Zn addition decreased the corrosion rates overall. When the Cu content was below 2000 ppm in the specimen containing 6 mass% Zn, the corrosion rate was kept less than commercial AZ31.Even though micro-galvanic corrosion occurred in both the Mg-Zn-Cu and Mg-Cu specimen, the corrosion rate of the former was smaller than the latter. The difference in the corrosion rate can be explained by the change in the deposit: Mg21Zn25 containing Cu in the former and Mg2Cu in the latter. From the electrochemical property of Zn and Cu, it is presumed that Mg21Zn25 containing Cu is baser than Mg2Cu. Under this consideration, the potential defference between the deposit and the matrix in Mg-Zn-Cu alloy should be smaller than that in Mg-Cu alloy, and so micro-galvanic corrosion could be inhibited. It is concluded that the corrosion property of Mg due to Cu can be improved by the existence of Zn. CONCLUSIONS In this study, the corrosion behaviors of Mg-Cu and Mg-Zn-Cu alloys were investigated and the inhibitory effect on Mg corrosion due to Cu by Zn was discussed. Mg2Cu deposit and Mg21Zn25 deposit containing Cu were found in Mg-Cu alloy and Mg-Zn-Cu alloy, respectively, and micro-galvanic corrosion occurred in both alloys. The corrosion rate of Mg-Zn-Cu was smaller than that of Mg-Cu, and the difference in the corrosion rate was considered due to the difference in the deposit in the alloys. The corrosion rate of Mg-6mass%Zn containing 2000 ppm-Cu was controlled less than that of AZ31. Figure 1

Electron transfer processes occurring on platinum neural stimulating electrodes: pulsing experiments for cathodic-first/charge-balanced/biphasic pulses for 0.566 ≤ k ≥ 2.3 in oxygenated and deoxygenated sulfuric acid

The application of a train of cathodic-first/charge-balanced/biphasic pulses applied to a platinum electrode resulted in a positive creep of the anodic phase potential that increases with increasing charge injection but reaches a steady-state value before 1000 pulses have been delivered. The increase follows from the fact that charge going into irreversible reactions occurring during the anodic phase must equal the charge going into irreversible reactions during the cathodic phase for charge-balanced pulses. In an oxygenated electrolyte the drift of the measured positive potential moved into the platinum oxidation region of the i(Ve) profile when the charge injection level exceeds k = 1.75. Platinum dissolution may occur in this region and k = 1.75 defines a boundary between damaging and non-damaging levels on the Shannon Plot. In a very low oxygen environment, the positive potential remained below the platinum oxidation region for the highest charge injection values studied, k = 2.3. The results support the hypothesis that platinum dissolution is the defining factor for the Shannon limit, k = 1.75. Numerous instrumentation issues were encountered in the course of making measurements. The solutions to these issues are provided.

Anion vs cation exchange membrane strongly affect mechanisms and yield of CO2 fixation in a microbial electrolysis cell

The CO2 removal from a concentrated gas stream (simulating biogas) has been investigated by using two identical fully bio-catalyzed microbial electrolysis cell (MEC), equipped with either a proton exchange membrane (PEM-MEC) or an anion exchange membrane (AEM-MEC). The equivalents deriving from the anodic oxidation of the organic matter were mainly converted into current, with an average coulombic efficiency between 53±9% and 85±15%, resulting in a little microbial growth (with an observed growth yield between 0.17 and 0.18gCOD/gCOD). The cathode compartment was continuously bubbled with a gas mixture containing CO2 (30% v/v, N2 balance) and the presence of an hydrogenophilic autotrophic culture allowed for CO2 reduction into CH4, with a cathode capture efficiency between 47±2% and 80±1%, respectively. In both systems, the first mechanisms of CO2 removal was its sorption as bicarbonate ion at high concentration in the MEC cathode, which was supported by alkalinity generation, needed by electroneutrality maintenance. However, in the AEM-MEC, 5.4g/Ld of CO2 were removed by crossing the membrane (which was due to both molecular diffusion and ionic transport) whereas in the PEM-MEC only 3.2g/Ld of CO2 were removed (through the osmotic overflow which was spilled from the cathodic liquid phase). Moreover, PEM-MEC showed higher COD removal efficiency (78±7%) and methane production rate (83±24meq/Ld) than AEM-MEC but showed a higher energy demand per unit of removed CO2 (2.36 vs 0.78 vs kWh/Nm3CO2removed). It is noteworthy that AEM-MEC energy demand was lower than full scale processes for biogas upgrading such as water scrubbing.

Microstructures and electrochemical corrosion properties of Mg–Al–Pb and Mg–Al–Pb–Ce anode materials

Mg–Al–Pb alloy is a good candidate for the anode material of magnesium seawater battery. For improving the low current utilization efficiency of Mg–Al–Pb alloy, the influence of Ce on the microstructures and electrochemical corrosion properties in a 3.5% NaCl solution was investigated using scanning electron microscope and electrochemical measurements. The results indicate that Ce refines the grain structure of Mg–Al–Pb alloy. The formation of strip Al11Ce3 second phase promotes the uniform distribution of Mg17Al12 phase in Mg–Al–Pb–Ce alloy. The addition of cerium accelerates the discharge activity of Mg–Al–Pb alloy. Due to a large number of cathodic Al11Ce3 and Mg17Al12 phases, Ce promotes the micro-galvanic corrosion and leads to larger corrosion current density and hydrogen evolution rate in Mg–Al–Pb–Ce alloy than those in Mg–Al–Pb alloy. However, Mg–Al–Pb alloy expresses smaller utilization efficiency than Mg–Al–Pb–Ce alloy because of grain detachment.

Reduction of Carbon Dioxide into Acetate in a Fully Biological Microbial Electrolysis Cell

A microbial electrolysis cell (MEC) was operated in continuous-flow condition to obtain cathodic CO2 reduction into acetate and methane along with COD anodic oxidation. Under steady-state conditions, most of the electron equivalents produced by COD anodic oxidation (866 mgCOD/Ld) were diverted into current rather than microbial growth, with an average Coulombic efficiency of 95 ± 8 %. In the cathodic chamber, acetate and methane formation from CO2 reduction accounted for 76% of the equivalents generated in the anodic oxidation reaction. Because a spill of cathodic liquid phase was necessary in order to counterbalance osmotic diffusion across the PEM, it was also possible to spill from the cathodic chamber a concentrated stream of acetate (248 ± 16meq/L). Moreover, as an additional effect, cation transport across the proton exchange membrane (PEM) and the consequent alkalinity generation made it possible to accumulate ammoniumnitrogen (242 ± 19 mgN/L) and bicarbonate (22.49 ± 1.45 gHCO3-/L). Hence, the MEC combined COD andCO2 removal in addition to nutrients and energy recovery from an anodic influent that simulated an urban wastewater.

Effects of Pulse Shape and Polarity on Sensitivity to Cochlear Implant Stimulation: A Chronic Study in Guinea Pigs.

Most cochlear implants (CIs) stimulate the auditory nerve with trains of symmetric biphasic pulses consisting of two phases of opposite polarity. Animal and human studies have shown that both polarities can elicit neural responses. In human CI listeners, studies have shown that at suprathreshold levels, the anodic phase is more effective than the cathodic phase. In contrast, animal studies usually show the opposite trend. Although the reason for this discrepancy remains unclear, computational modelling results have proposed that the degeneration of the peripheral processes of the neurons could lead to a higher efficiency of anodic stimulation. We tested this hypothesis in ten guinea pigs who were deafened with an injection of sysomycin and implanted with a single ball electrode inserted in the first turn of the cochlea. Animals were tested at regular intervals between 1 week after deafening and up to 1 year for some of them. Our hypothesis was that if the effect of polarity is determined by the presence or absence of peripheral processes, the difference in polarity efficiency should change over time because of a progressive neural degeneration. Stimuli consisted of charge-balanced symmetric and asymmetric pulses allowing us to observe the response to each polarity individually. For all stimuli, the inferior colliculus evoked potential was measured. Results show that the cathodic phase was more effective than the anodic phase and that this remained so even several months after deafening. This suggests that neural degeneration cannot entirely account for the higher efficiency of anodic stimulation observed in human CI listeners.

Formation of a Trivalent Chromium Conversion Coating on AA2024-T351 Alloy

The formation of a trivalent chromium conversion coating on AA2024-T351 aluminum alloy has been studied using electron microscopy, scanning Kelvin probe force microscopy, ion beam analysis and X-ray photoelectron spectroscopy (XPS). The coating contained oxide, hydroxide, fluoride and sulfate species, and consisted of two main layers: a zirconium- and chromium-rich outer layer and a thinner, aluminum-rich, inner layer. XPS indicated that zirconium and chromium are mainly present as ZrO2, Cr(OH)3, Cr2(SO4)3 and CrF3. In addition, a thin aluminum-rich layer, probably composed of hydrated alumina, occurred transiently at the coating surface. The coating above cathodic second phase particles was usually thicker than that above the matrix due to the locally increased alkalinity. In the early stages of treatment, the thickest coating formed above the S-phase particles. Localized corrosion and copper enrichment of the matrix occurred at the coating base. The localized corrosion is possibly related to the observed accumulation of fluoride ions at the inner layer and the enrichment of copper in the alloy. The thickness of the coating above the alloy matrix was significantly less than that of a coating formed on high purity aluminum.

Corrosion inhibition of pure aluminium and AA2014‐T6 alloy by strontium chromate at low concentration

The influence of a low concentration of strontium chromate on the corrosion inhibition of superpure aluminium and AA2014‐T6 aluminium alloy in 0.6 m chloride solution has been investigated to simulate the leaching process of inhibitors from coatings. The potential‐time and polarisation behaviour show influences on both the anodic and cathodic kinetics on the superpure aluminium surface. However, predominant cathodic inhibition was observed for the AA2014‐T6 aluminium alloy. It was evident that chromium species were reduced at cathodic second phase particles, forming a thin passive film at the cathodic sites, which blocks the oxygen reduction reaction and, consequently, provides effective corrosion inhibition. Copyright © 2015 The Authors Surface and Interface Analysis Published by John Wiley & Sons Ltd.

Evaluation of Ba deficient NdBaCo2O5+δ oxide as cathode material for IT-SOFC

Neodymium- and cobalt-based layered perovskite oxides with increasing Ba deficiency (NdBa1-xCo2O5+δ, x=0.0÷0.2) are prepared via solid state firing. The chemical and electrochemical properties of these materials are characterized via XRD, SEM, TG-DTA, 4-probe conductivity measurement and EIS tests on symmetric cells. The maximum tolerated Ba deficiency is slightly below 10%. The compounds crystallize in an ordered layered structure with orthorhombic Pmmm (for x=0 and 0.5) and tetragonal P4/mmm (for x=0.10) crystal lattice. All the compounds show high total conductivity (between 400 and 600S/cm at 700°C). A remarkable tenfold decrease of the area specific resistance is observed at decreasing the Ba content from 0 to 10%, with the compound at 10% Ba deficiency reaching the best performance (0.1Ω*cm2 at 700°C). Detailed equivalent circuit analysis on EIS tests at varying temperature (550 to 700°C) and O2 content (100% to 5% v/v) reveals that the limiting steps are the transport of oxygen ions within the cathodic phase and across the electrolyte interface at high frequency, and the formation of an oxygen ion at intermediate frequency. The effect of Ba on the electrochemical mechanism is associated with a promotion of the bulk diffusion steps at high frequency.

Effect of Solution Treatment on Mechanical and Corrosion Behaviors of 6082-T6 Al Alloy

The mechanical and corrosion behavior of Al alloy 6082-T6 subjected to solution heat treating condition at temperatures varying from 400 to 600 °C and soaking times of 3–24 h have been investigated. Solution heat treating at 550 °C for 24 h led to the dissolution of the Mg2Si and AlSi6Mg3Fe precipitates into the matrix, and the Al12(FeMn)3Si2 phase transformed into Al85(Fe0.28Mn0.72)14Si phase. The solution-treated alloy showed equiaxed grain morphology with an average grain size of 85.7 µm. Increasing the solution heat treating temperature beyond 550 °C caused a reduction in corrosion resistance of the alloy. The pitting potential increased due to the presence of the anodic phase Mg2Si (dissolved at 550 °C) in Al matrix and it decreased with the formation of cathodic phases such as AlSi6Mg3Fe and Al12(FeMn)3Si2 (dissolved at 550 °C/24 h) in the alloy. General corrosion resistance of the alloy increased with decreasing Mg2Si concentration in the Al matrix. The optimum solution heat treating condition of 550 °C for 24 h resulted in an improvement in hardness (63 VHN), ultimate tensile strength (UTS—208 MPa), and pitting potential (−675 mV) and uniform corrosion potential (−1.255 mV) of 6082 Al alloy.

The gas phase emitter effect of lanthanum within ceramic metal halide lamps and its dependence on the La vapor pressure and operating frequency

The gas phase emitter effect increases the lamp lifetime by lowering the work function and, with it, the temperature of the tungsten electrodes of metal halide lamps especially for lamps in ceramic vessels due to their high rare earth pressures. It is generated by a monolayer on the electrode surface of electropositive atoms of certain emitter elements, which are inserted into the lamp bulb by metal iodide salts. They are vaporized, dissociated, ionized, and deposited by an emitter ion current onto the electrode surface within the cathodic phase of lamp operation with a switched-dc or ac-current. The gas phase emitter effect of La and the influence of Na on the emitter effect of La are studied by spatially and phase-resolved pyrometric measurements of the electrode tip temperature, La atom, and ion densities by optical emission spectroscopy as well as optical broadband absorption spectroscopy and arc attachment images by short time photography. An addition of Na to the lamp filling increases the La vapor pressure within the lamp considerably, resulting in an improved gas phase emitter effect of La. Furthermore, the La vapor pressure is raised by a heating of the cold spot. In this way, conditions depending on the La vapor pressure and operating frequency are identified, at which the temperature of the electrodes becomes a minimum.

Relationship between heat treatment and corrosion behavior of Mg-15Y alloy

The corrosion behaviors of a basic type of RE-containing magnesium alloy Mg-15Y processed by different heat treatment methods were studied in 3.5% NaCl solution at room temperature. The amount of Mg24Y5 phase decreased with the extending of homogenization treatment. The time for achieving dissolving equilibrium of homogenization treatment at 525, 535, and 545 ° was 24, 20, and 8 h, respectively. The corrosion behavior of Mg-15Y alloy was studied using immersion, hydrogen evolution and electrochemical tests. The experimental results revealed that the heat treatment improved the corrosion resistance, and the corrosion resistance became better with increasing the heat treatment time. The corrosion mode of the alloy after heat treatment was microgalvanic corrosion consisting of the cathodic Mg24Y5 phase and anodic α-Mg matrix, and Mg-15Y exhibited favorable uniform corrosion mode in NaCl solution. The volume and increasing tendency of the homogenization treatment samples were both more than those of the as-cast sample.

High‐voltage compliant microelectrode array drivers for intracortical microstimulation

SummaryWe present in this paper two low‐power high‐impedance microelectrode array drivers (MEDs) dedicated for visual intracortical microstimulation. These output stages of a new microstimulator are highly configurable and able to deliver higher compliance voltage (20 V for anodic and cathodic phases) across microelectrode‐tissue interface impedance compared with previously reported designs. Each MED is featured with a high‐voltage switch‐matrix, 3.3 V/20 V current mirrors, an on‐chip 32‐bit serial‐in parallel‐out shift register, and the new forbidden state logic circuits. Both systems are able to deliver eight bipolar or 16 monopolar stimulation simultaneously. The first MED is able to deliver one stimulation current level and the second one provides four different current amplitudes simultaneously to 16 electrodes. Two microchips have been designed and fabricated using Teledyne DALSA 0.8 µm 5V/ 20v double‐diffused metal‐oxide‐semiconductor field‐effect transistor (Teledyne DALSA Semiconductor, Bromont, Québec, Canada) technology to meet the required high‐voltage compliance. The nominal values of largest supply voltages are ±10 V. The maximum stimulation current per input channel is 400 μA and per output channel through an emulated microelectrode impedance of 100 kΩ is 100 μA. The measured output compliance voltage is 10 V/phase (anodic or cathodic) for the specified supply voltages. Increment of supply voltages to ±13 V allows 220 μA stimulation current per output channel enhancing the output compliance voltage up to 20 V/phase. The measured quiescent power consumptions of the proposed microelectrode array drivers are 316 and 735 μW, respectively. Post‐layout simulation and measurement results of two MEDs and comparison with other designs have been reported in this paper. Copyright © 2015 John Wiley & Sons, Ltd.

Protons accumulation during anodic phase turned to advantage for oxygen reduction during cathodic phase in reversible bioelectrodes

Reversible bioelectrodes were designed by alternating acetate and oxygen supply. It was demonstrated that the protons produced and accumulated inside the biofilm during the anodic phase greatly favored the oxygen reduction reaction when the electrode was switched to become the biocathode. Protons accumulation, which hindered the bioanode operation, thus became an advantage for the biocathode. The bioanodes, formed from garden compost leachate under constant polarization at −0.2V vs. SCE, were able to support long exposure to forced aeration, with only a slight alteration of their anodic efficiency. They produced a current density of 16±1.7A/m2 for acetate oxidation and up to −0.4A/m2 for oxygen reduction. Analysis of the microbial communities by 16S rRNA pyrosequencing revealed strong selection of Chloroflexi (49±1%), which was not observed for conventional bioanodes not exposed to oxygen. Chloroflexi were found as the dominant phylum of electroactive biofilms for the first time.

Impact of modulating phase duration on electrically evoked auditory brainstem responses obtained during cochlear implantation

ObjectiveTo investigate the effect of increasing phase duration (pulse width, T-pulse) using a biphasic pulse composed of an initial anodic active phase followed by a balancing cathodic phase on the electrically evoked auditory brainstem responses (eABRs) recorded at the time of cochlear implantation.DesigneABRs recorded during 188 surgeries for cochlear implantation from 1999 to 2006 in a single center were retrospectively reviewed by two independent observers. All patients were fitted with a NEURELEC cochlear implant (CI) device, initially DIGISONIC® then DIGISONIC SP® (2004–2006).ResultImmediately following cochlear implantation, stimulation by the CI resulted in reliable wave III and V eABR waveforms (mean wave III latency 2.23 ± 0.38 ms SD and wave V latency 4.28 ± 0.42 ms SD). Latencies followed an apical to basal gradient (0.32 ms increase in mean eV latency and 0.12 ms for eIII latency). With increasing phase duration, wave III and wave V latencies significantly decreased in association with a shortening of the eIII–eV interwave gap, while amplitudes of both waves increased.ConclusionThe impact of increasing phase duration on latency and amplitude of brainstem responses in a large set of patients implanted with NEURELEC CIs was reported.

Cathodic peeling damage of Cu6Sn5 phase in Cu/SnAg3.0Cu0.5/Cu bridge interconnections under current stressing

The cathodic interfacial damage behavior that has been attributed to electromigration is serious but has often been confused with thermomigration damage in solder interconnections. In this paper, after the effects of the non-uniform temperature distribution of Cu/SnAg3.0Cu0.5/Cu bridge joints are decoupled from the effects of the current stress, the microstructural evolution of the cathodic Cu6Sn5 phase is investigated under an average current density of 7.12 × 107 A·m−2 for 0–350 h. The results show that the interfacial Cu6Sn5 peels rather than dissolving completely at the cathode, because of both adhesion degradation at the Cu6Sn5/Cu interface and sustained cathodic stresses. This unrecorded peeling behavior will contribute to the rapid formation of interfacial voids and will thus dramatically increase the risk of interfacial failure. Fortunately, by restricting the intergranular diffusion and enhancing the bond strengths between adjacent Cu6Sn5 grains, an aging pre-treatment of the solder joints is found to be an effective way to slow down the Cu6Sn5 peeling process and achieve robust solder interconnections.

Effect of samarium on microstructure and corrosion resistance of aged as-cast AZ92 magnesium alloy

The effects of samarium (Sm) on microstructure and corrosion resistance of AZ92 magnesium alloy were characterized and analyzed by scanning electronic microscopy, X-ray diffraction, mass loss test, electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy and potentio-dynamic polarization test. The results showed that the added Sm could promote continuous precipitation of β-Mg17Al12 phase in grains, and meanwhile restrain discontinuous precipitation of the same phase along the grain boundaries. Thus, the precipitations distributed more uniformly in the aged AZ92 magnesium alloys. When the content of Sm was 0.5 wt.%, the corrosion resistance of aged AZ92 alloy tended to be the best, which was due to the β-phase distributes more homogeneous reducing the galvanic corrosion. The corrosion product film had more integrality and compactness than AZ92 alloys without Sm. However, it resulted in worse corrosion resistance of AZ92 alloy because of the formation of mass cathodic Al2Sm phase coming from excess Sm in AZ92 alloy.

Effect of native air-formed oxidation on the corrosion behavior of AA 7075 aluminum alloys

The effect of native air-formed oxidation on the corrosion behavior of AA 7075 aluminum alloy and selective corrosion of anodic Mg2Si precipitates was presented. Oxidation of Mg2Si leads to formation of Mg(OH)2 protrusions depleting magnesium in this precipitate as shown by AFM, SEM and EDX results. Spectroscopic studies prove that composition changes occurring within the passive layer may be a cause of observed improvement of electrochemical properties under prolonged exposition to air. Influence of cathodic phases containing AlFe(Cu,Mn,Cr) is limited in these conditions.

Correlation between optical and structural properties of copper oxide electrodeposited on ITO glass

In this paper we study the growth of copper oxide (Cu2O) thin films on indium tin oxide (ITO)-coated glass substrate by electrochemical deposition. We vary the applied potential from −0.50 to −0.60V vs. Ag/AgCl in order to have a pure Cu2O. The copper oxide thin films properties are obtained using Spectroscopic Ellipsometry (SE) in the frame of the Forouhi and Bloomer model. This model demonstrates that depending on the applied cathodic potential pure or mixed phases of CuO and Cu2O can be obtained. Structural, morphological and optical properties are performed in order to confirm the SE results. X-ray diffraction analysis of the films reveals a mixed phase for a potential lower than −0.60V vs. Ag/AgCl while a high purity is obtained for this last potential. The optical band gap energy (Eg) is evaluated using the tauc relation. Pure Cu2O having a band gap of Eg=2.5eV and a thickness around 900nm are therefore successfully obtained with an applied potential of −0.60V. Raman measurements show the characteristic modes of Cu2O with a contribution of CuO modes at 618cm−1. The intensity of the CuO modes decreases as the applied cathodic potential increases, leading to pure copper oxide layers.