Copper Oxide Phase Research Articles

Synthesis and microstructural studies of annealed Cu(2)O/Cu(x)S bilayer as transparent electrode material for photovoltaic and energy storage devices.

Cu2 O thin film and a transparent bilayer have been fabricated by electrodeposition method. The growths were obtained in potentiostatic mode with gradual degradation of anodic current. X-ray diffraction (XRD) study showed that the bilayer is polycrystalline and it possesses mixture of different crystallite phases of copper oxides. Surface morphology of the films was investigated by scanning electron microscopy (SEM). The SEM images revealed that the films were uniformly distributed and the starting material (Cu2 O) had cubical structure. Grains agglomeration and crystallinity were enhanced by annealing. Optical studies indicated that all the samples have direct allowed transition. Energy band gap of the bilayer film was reduced by annealing treatment thus corroborating quantum confinement upshot.

Physical Behaviour of RF Magnetron Sputtered Ag2Cu2O3 Films: Influence of Oxygen Partial Pressure and Substrate Temperature

Thin films of silver copper oxide were deposited on to glass and silicon substrates by RF magnetron sputtering of equimolar silver copper alloy (Ag50Cu50) target at various oxygen partial pressures in the range 5 x 10(-3)-6 x 10(-2) Pa and substrate temperatures in the range 303 to 473 K. The influence of oxygen partial pressure and substrate temperature on the core level binding energies, structure and surface morphology, and electrical and optical properties of the films were studied. The oxygen partial pressure played a prominent role on the growth of the films with different phases of silver copper oxide. X-ray photoelectron spectroscopic studies indicated the presence of characteristic core level binding energies related to the silver, copper and oxygen. The films formed at oxygen partial pressure of 2 x 10(-2) Pa and substrate temperature of 423 K were mixed phase of Ag2Cu2O3, Ag2Cu2O4 and Ag2O. Single phase Ag2Cu2O3 films with crystallite size of 28 nm were achieved at an oxygen partial pressure of 2 x 10(-2) Pa and substrate temperature of 473 K. The optical band gap of the films increased from 1.78 to 1.98 eV with increase of substrate temperature from 303 to 473 K. Single phase Ag2Cu2O3 films formed at substrate temperature of 473 K showed electrical resistivity of 2 x 10(-3) Omega cm and optical band of 1.98 eV.

Single Crystalline CuO Nanowire for Resistive Random Access Memory Application

For the development of high density memory arrays of resistive random access memory (RRAM), nanowires provide the potential to reduce the device size to overcome the limitation of conventional lithography. In this work, copper oxide nanowires were synthesized and served as the building block for 1-D RRAM nanodevice. The phase of Copper oxide was identified to be CuO by selected area electron diffraction (SAED) patterns and energy dispersive spectrometer (EDS). We fabricated the Au/CuO-nanowire/Au RRAM nanodevice by electron-beam lithography techniques. From I-V measurement, the forming voltage and RESET voltage were 0.64 V and 5.2 V, respectively. This low forming voltage and ultra-high reset voltage may result from stacking fault in the core of CuO nanowires. From scanning electron microscope (SEM) image ,the as-formed protrusion near the anode and reduction near the cathode after several electrical measurements indicated that the diffusion of oxygen vacancies generating the conducting filament from cathode, result in the change of nanowire morphology. The result will be beneficial to understand the switching properties of nonvolatile memory device at nanoscale.

Study of correlation between activity and structural properties of Cu-(Cr, Mn and Co)2 nano mixed oxides in VOC combustion

The correlation between structure and catalytic activities of Cu-(Cr, Mn and Co)2 mixed oxides synthesized by a sol–gel combustion method was investigated for the oxidation of 2-propanol. The catalysts were characterized by FTIR, XRD, XPS, TPR and UV–vis DRS. Although the same preparation conditions were used for all the systems, obtained samples presented different pureness degrees. The structural characterization by XRD revealed that copper-chromite was pure CuCr2O4, while copper-manganese and copper-cobalt mixed oxides resulted in a mixture of the spinel (CuMn2O4 and Cu0.15Co2.85O4, respectively) and copper oxide phases. UV–vis DRS results also indicated a larger presence of small crystallites of CuO in the copper-cobalt oxide. Copper-cobalt oxide exhibited the highest activity in 2-propanol combustion which is explained, as expected for a Mars van Krevelen mechanism, by its higher reducibility at the reaction conditions and by a possible synergistic effect between this mixed oxide and CuO particles.

Structural Evolution of Cu-In-Se Thin Films Prepared by Spin Coating Technique

A low cost and simple fabrication of Cu-In-Se polycrystalline thin film for copper indium diselenide solar cell was prepared in a two-step process. The first step, a Cu In precursor film was prepared from copper acetate monohydrate and indium acetate mixed solution. The solution was coated on molybdenum-coated soda lime glass using the spin coating technique at room temperature following annealing in air at 500°C for 20 minutes. The effect between spin parameters and film thickness of as-deposited Cu-In film were investigated. The second step, selenium was added in the precursor film by selenization process at 450°C in Se atmosphere for 30 minutes in a low vacuum tube furnace with background pressure of 10-2 mbar. The crystallographic properties of Cu-In-Se thin films were identified by X-ray diffractometer (XRD), the surface and cross-sectional morphology of films were observed by scanning electron microscopy (SEM). The chemical compositions of films were characterized by energy dispersive spectroscopy (EDS). It was found that the thickness of Cu-In films deposited on molybdenum-coated soda lime glass were approximately 1 μm. The EDS analysis showed the composition ratio in atomic % of Cu/In as approximately as 0.77. The XRD results reveal that the as-deposited Cu-In films consist of a mixture of copper oxide (CuO) and indium oxide (In2O3) phase at the annealing temperature of 500°C. Furthermore, CuO and In2O3 phase were converted to (112) oriented chalcopyrite copper indium diselenide after selenization process.

The Structural Evolution of $(\hbox{Gd}, \hbox{Y}) \hbox{Ba}_{2}\hbox{Cu}_{3}\hbox{O}_{\rm x}$ Tapes With Zr Addition Made by Metal Organic Chemical Vapor Deposition

Structural analysis of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(\hbox{Gd}, \hbox{Y})\hbox{Ba}_{2}\hbox{Cu}_{3} \hbox{O}_{x}$</tex></formula> tapes with Zr addition made by metal organic chemical vapor deposition has been conducted with transmission electron microscopy and X-ray diffraction. Zr content in the films was varied from 0 to 25 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\%$</tex></formula> in the precursor. In all Zr-doped films, self-assembled nanocolumnar structures of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{BaZrO}_{3}$</tex></formula> (BZO) were observed along the <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$c$</tex></formula> -axis. The amount of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$\hbox{BaZrO}_{3}$</tex></formula> was found to increase steadily with Zr content. Additionally, planar BZO plates were found on the (001) plane of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(\hbox{Gd}, \hbox{Y})\hbox{Ba}_{2} \hbox{Cu}_{3}\hbox{O}_{x}$</tex></formula> film. The size and thickness of BZO plates were seen to increase with Zr doping level. Rare-earth copper oxide phases were observed to begin to emerge in the 20 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$\%$</tex></formula> Zr-doped film. Cross-sectional study of the interface between <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(\hbox{Gd}, \hbox{Y})\hbox{Ba}_{2}\hbox{Cu}_{3}\hbox{O}_{\rm x}$</tex></formula> and <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{LaMnO}_{3}$</tex></formula> cap layer revealed a thin discrete BZO layer on the <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{LaMnO}_{3}$</tex></formula> in the 20 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\%$</tex></formula> Zr doped film.

Bimetallic Au–Cu supported on ceria for PROX reaction: Effects of Cu/Au atomic ratios and thermal pretreatments

The influence of pretreatment (calcination or reduction), on bimetallic Au–Cu/CeO2 catalysts with a fixed Au loading of 2wt.% and an atomic Cu/Au ratio of 1/3, 1/1 or 3/1 was studied. The catalysts were prepared by direct anionic exchange of HAuCl4 followed by a Cu(NO3)2 impregnation. Both pretreatment methods led to catalysts of significantly different structures and surface compositions. For the calcined samples, the presence of a copper oxide phase can be observed when the Cu/Au is 3/1, whereas, for the reduced catalysts, there is the formation of an Au–Cu alloy and of metallic copper due to the immediate decomposition of the copper precursor, which is able to be partially alloyed with gold. XPS reveals that the calcination led to the segregation of a CuO-rich phase on the surface, while in the case of reduction, the surface is not so Cu-enriched. All of the catalysts were evaluated by preferential oxidation of CO in the presence of hydrogen and compared with monometallic 2% Au/CeO2 and 2% Cu/CeO2. For all catalysts, it was found that irrespective of the atomic Cu/Au ratio, a reduction improves the CO conversion and CO2 yield compared with monometallics while enhanced catalytic performances are only observed for the 1/3 Cu/Au atomic ratio of the calcined samples. The reduced Au–Cu bimetallics are stable with time on-stream contrary to the calcined one where the formation of carbonate-like species, responsible of a deactivation, is observed. Furthermore the reduced catalyst remained active even in the presence of CO2 and H2O in the gas stream

Copper oxide phase content and its effect on the electric pulse induced resistive switching characteristics of CuxO resistive random access memory

The electric pulse induced resistance (EPIR) switching phenomenon in CuxO thin films has been related to the oxidation states of copper in the films. A quantitative measurement of the copper oxide phase content in the grown CuxO films shows a composition change from a Cu rich CuxO (Cu4O3) phase to a CuO phase on increasing the growth temperature under RF sputtering from 200°C to 500°C. This composition change decreases the film resistance, and affects the forming process required for resistive switching and the EPIR switching phenomenon in the film. Stable EPIR switching has been seen only for films with Cu4O3 as the major phase and such films also exhibit two bipolar resistance switching modes.

Effects of vacuum annealing on the optical and electrical properties of p-type copper-oxide thin-film transistors

We have investigated the effects of vacuum annealing on the optical and electrical properties of the p-type copper-oxide thin-film transistors (TFTs). The vacuum annealing of the copper-oxide thin-film was performed using the RF magnetron sputter at various temperatures. From the x-ray diffraction and UV-vis spectroscopy, it is demonstrated that the high-temperature vacuum annealing reduces the copper-oxide phase from CuO to Cu2O, and increases the optical transmittance in the visible part of the spectrum. The fabricated copper-oxide TFT does not exhibit the switching behavior under low-temperature vacuum annealing conditions. However, as the annealing temperature increases, the drain current begins to be modulated by a gate voltage, and the TFT exhibits a high current on–off ratio over 104 as the vacuum annealing temperature increases over 450 °C. These results show that the vacuum annealing process can be an effective method of simultaneously improving the optical and electrical performances in p-type copper-oxide TFTs.

Nature of the active sites for the total oxidation of toluene by CuO[sbnd]CeO2/Al2O3

The binary metal oxide, CuOCeO2/γ-Al2O3, has been compared with the single oxide components CuO/γ-Al2O3 and CeO2/γ-Al2O3 for toluene total oxidation. The nature of the active sites was determined by means of several spectroscopic techniques, while the transient response technique TAP (Temporal Analysis of Products) was used to investigate the catalytic performance.The improved performance of the CuOCeO2/γ-Al2O3 catalyst compared to CuO/γ-Al2O3 is attributed to the formation of a Ce1−xCuxO2−x solid solution with a crystallite size of 6nm. Within this phase, oxidation of toluene occurs at Cu2+ sites and reduction of oxygen at Ce3+ sites. Similar to Wacker chemistry, two redox couples, Ce4+/Ce3+ and Cu2+/Cu1+, are operational. Apart from the solid solution, a copper oxide phase with a crystallite size of 100nm shows significantly lower catalytic activity.X-ray absorption near-edge structure (XANES) experiments at the copper and cerium edge indicate that Ce4+ is reduced at lower temperature than Cu2+. Upon re-oxidation with CO2 or H2O, Ce3+ is partly re-oxidized, while Cu0 is not. This explains an activity increase in the CuOCeO2/γ-Al2O3 in the presence of H2O or CO2. CuO/γ-Al2O3 shows loss of activity in the presence of H2O as site blocking is not compensated by an increase in the re-oxidation rate.

Atomic Layer Deposition of Copper Oxide using Copper(II) Acetylacetonate and Ozone

AbstractWe report on the deposition of copper oxide by atomic layer deposition (ALD) using copper acetylacetonate (Cu(acac)2) and ozone (O3) as precursors. The aim is to deposit oxides of copper as possible candidates for materials in all‐oxide photovoltaics. The present study results in ALD‐type deposition of the tenorite phase of copper(II) oxide in a temperature window of 150 °C to ca. 230 °C, with a growth rate of ∼0.038 nm per cycle. The resulting ALD characteristics, with a relatively large ALD window in deposition temperature, should be well suited for combination with additional deposition processes for the formation of complex compounds. The film thickness is studied using X‐ray reflectivity (XRR), and phase is determined by X‐ray diffraction (XRD). Surface roughness is studied using atomic force microscopy (AFM), and X‐ray photoelectron spectroscopy (XPS) is used to investigate the chemical state of the deposited films.

Growth and microstructural study of CuO covered ZnO nanorods

A feasible method to synthesize CuO covered ZnO nanorods was realized. Firstly, ZnO nanorods were grown by wet-chemical route at 90°C onto borosilicate glass substrates. Subsequently, the CuO covered ZnO matrix was obtained by Aerosol-Assisted Chemical Vapor Deposition at different temperatures (300, 400, 500 and 600°C). The CuO–ZnO nanocrystals were microstructurally characterized by electron microscopy and Rietveld refinement. Results showed a CuO formed nanocrystals but also an amorphous fraction of CuO which increases with the synthesis temperature. Additionally, it was evident the presence of secondary copper-oxide phase (paramelaconite), which also has grown over the ZnO nanorod surface.

Effect of La&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; Addition on the Microstructure and Electrical Properties of Copper-Nickel Manganese Thermistors

The effect of La2O3 addition on the microstructure and electrical properties of Mn0.75Ni1.25CuO4-xLa2O3 (0≤x≤0.3) was studied. The crystal structure, phase compositions and morphology were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The sintered ceramic bodies was typical polycrystalline, with cubic spinel structure of copper manganese oxide, rocksalt structure of nickel copper oxide, along with monoclinic phase of copper oxide and orthorhombic perovskite structure of lanthanum manganese oxide. The obtained ρ77K, B77K/90K constant and activation energy of the thermistors were in the range of 3.88-9.29 Ω cm, 245-261 K, and 0.0211–0.0225 eV, respectively. This means that the electrical properties can be adjusted to desired values, depending on the La content. So these prepared thermistors were intended to be used under low temperature conditions.

CeO2 ↔ CuOx Interactions and the Controlled Assembly of CeO2(111) and CeO2(100) Nanoparticles on an Oxidized Cu(111) Substrate

The catalytic performance of ceria-based heterogeneous catalysts in many chemical transformations (water–gas shift reaction, CO oxidation, alcohol synthesis from CO/CO2 hydrogenation, etc.) is affected by the surface structure of the ceria. To control the performance of ceria-containing inverse catalysts, we devised a method to grow ceria nanoparticles (NPs) exposing exclusively either (111) or (100) surfaces and characterized their surface structures by scanning tunneling microscopy. When cerium is vapor-deposited on Cu(111) in a background of molecular O2, only CeO2(111) NPs grow. However, if the surface of Cu(111) is preoxidized with O2 or NO2 to form a rectangular copper oxide phase, probably Cu4O3(001), CeO2(100) NPs grow on the oxide template instead. These experimental findings are interpreted using results of density functional calculations. The (100) surface of bulk ceria reconstructs to preserve charge neutrality. This is not necessary for CeO2(100) NPs grown on Cu4O3(001), where the topmost oxy...

Dehydrogenation of cyclohexanol on copper containing catalysts: The role of the support and the preparation method

Abstract SiO 2 and Al 2 O 3 supported copper catalysts were prepared by “chemisorption–hydrolysis” or incipient wetness impregnation methods and investigated by XRD, TG-TPR, UV–vis diffuse reflectance and FTIR spectroscopy. Formation of finely dispersed copper oxide species was registered for the samples prepared by “chemisorption–hydrolysis” method, while a significant amount of XRD detectable copper oxide phase is registered for the SiO 2 impregnated one. The latter materials possess higher catalytic selectivity in cyclohexanol dehydrogenation to cyclohexanone.

Size-dependent thermal oxidation of copper: single-step synthesis of hierarchical nanostructures

Thermal oxidation of copper is a simple and scalable method to produce copper oxide nanowires. We report for the first time the formation of nanowires on copper powder during thermal oxidation and the resulting nanowire coverage that is dependent on the initial particle size. Systematic thermogravimetric analysis (TGA) and in situ X-ray diffraction (XRD) studies of thermal oxidation of particles of different sizes provide insights into the size-dependent process and evolution of the various phases of copper and copper oxide with time. Furthermore, we find that a large void is formed within these particles after oxidation and propose a mechanism based on the Kirkendall effect. The unique tunability of hierarchical features and hollow interior can be used to create new scalable structures for applications in a variety of areas including thermal management and catalysis.

ChemInform Abstract: Structural Properties and Thermochemical Reactivity of Superconducting Mixed Copper Oxide Phases

Abstract A selection of published results on superconducting mixed copper oxides, focussing on the interrelationship between their thermochemical reactivity and their structural properties, is presented. The role of thermal analysis in the field of superconductivity is briefly discussed.

Phenol Hydroxylation over Cu-Containing LDHs and Their Calcined Forms: Profound Cobivalent Metal Influence

Copper containing layered double hydroxides (LDHs) with less than 1 atom % Cu along with different cobivalent ions such as magnesium, zinc, nickel or cobalt at (Cu+M(II))/Al atomic ratio 3.0 were synthesized. Calcination of these materials offered mixed metal oxides (refereed here as CLDHs) without any discrete copper oxide phase as confirmed by PXRD and STEM analysis. Hydroxylation of phenol to catechol (CAT) and hydroquinone (HQ) was carried out over both as-synthesized and calcined materials. Among the cobivalent ions, zinc containing samples both in the as-synthesized and calcined forms showed very high activity while cobalt showed the minimum. Variation of copper content for CuZnAl ternary system (0.009 atom % to 0.056 atom %) showed a maximum activity for the sample with 0.038 atom % (CuZnAl-5-CLDH). High activity was attributed to better dispersion of isolated copper species as inferred through TPR measurements. Highly active CuZnAl-5-CLDH can be reused up to three cycles without any significant change in the activity. No significant variation in the conversion was noted when the reaction was scaled up to 200 times over CuZnAl-5-CLDH renders the promise of exploring it to the next level.

Dielectric properties of CaCu 3Ti 4− xCo xO 12 ( x = 0.10, 0.20, and 0.30) synthesized by semi-wet route

Undoped CaCu 3Ti 4O 12 and cobalt doped CaCu 3Ti 4− x Co x O 12 (CCTCO) with x = 0.10, 0.20 and 0.30 were prepared by semi-wet route for the first time using solid TiO 2 powder and metal nitrate solutions. XRD analysis confirmed the formation of single-phase material in the samples sintered at 900 °C for 6 h. Structure does not change on doping with cobalt and it remains cubic in all the three compositions studied. Lattice parameter increases slightly with cobalt doping. SEM micrographs of the CaCu 3Ti 4− x Co x O 12 samples show that the grain size is in the range of 2–8 μm for these samples. EDX studies show the percentage of elements along with the grain and grain boundary, which confirm the rich phase of copper oxide at grain boundaries. Dielectric properties have been measured as a function of temperature and frequency.

Low-energy theory of thet−t′−t″−UHubbard model at half-filling: Interaction strengths in cuprate superconductors and an effective spin-only description ofLa2CuO4

Spin-only descriptions of the half-filled one-band Hubbard model are relevant for a wide range of Mott insulators. In addition to the usual Heisenberg exchange, many other types of interactions, including ring exchange, appear in the effective Hamiltonian in the intermediate coupling regime. In order to improve on the quantitative description of magnetic excitations in the insulating antiferromagnetic phase of copper-oxide (cuprate) materials, and to be consistent with band-structure calculations and photoemission experiments on these systems, we include second- and third-neighbor hopping parameters, ${t}^{\ensuremath{'}}$ and ${t}^{\ensuremath{''}}$, into the Hubbard Hamiltonian. A unitary transformation method is used to find systematically the effective Hamiltonian and any operator in the spin-only representation. The results include all closed four-hop electronic pathways in the canonical transformation. The method generates many ring exchange terms that play an important role in the comparison with experiments on ${\text{La}}_{2}{\text{CuO}}_{4}$. Performing a spin-wave analysis, we calculate the magnon dispersion as a function of $U$, $t$, ${t}^{\ensuremath{'}}$, and ${t}^{\ensuremath{''}}$. The four parameters are estimated by fitting the magnon dispersion to the experimental results of Coldea et al. [Phys. Rev. Lett. 86, 5377 (2001)] for ${\text{La}}_{2}{\text{CuO}}_{4}$. The ring exchange terms are found essential, in particular to determine the relative sign of ${t}^{\ensuremath{'}}$ and ${t}^{\ensuremath{''}}$, with the values found in good agreement with independent theoretical and experimental estimates for other members of the cuprate family. The zero-temperature sublattice magnetization is calculated using these parameters and also found to be in good agreement with the experimental value estimated by Lee et al. [Phys. Rev. B 60, 3643 (1999)]. We find a value of the interaction strength $U\ensuremath{\simeq}8t$ consistent with Mott insulating behavior.