Single Phase CuO Research Articles

Ultrasound assisted one pot synthesis of nano-sized CuO and its nanocomposite with poly(vinyl alcohol)

The ultrasound (US) assisted one pot method has used to synthesize CuO nanoparticles. The fourier transform infrared spectroscopy (FTIR) spectrum shows a characteristic peak of metal–oxygen bond at 535 cm−1, which confirms the CuO formation. The high resolution transmission electron microscope (HRTEM) images of the synthesized nano-CuO confirms the size of nanorods with the length of approximately 25–30 nm, and its breadth is less than one nanometer. X-ray diffraction (XRD) pattern of CuO can be readily assigned to those of crystalline CuO, indicating the formation of single-phase CuO with monoclinic structure. The synthesized nano-CuO is mixed with poly(vinyl alcohol) (PVA) to prepare the PVA/CuO nanocomposite to improve the thermal stability of PVA. Their physico-chemical properties are examined by means of FTIR, XRD, differential scanning calorimetry, thermogravimetric analysis, HRTEM, and scanning electron microscope (SEM) techniques.

Synthesis and characteristics of nanocrystalline 3Y-TZP and CuO powders for ceramic composites

A weakly agglomerated 3Y-TZP powder with 100% tetragonal crystal structure and a primary crystallite diameter of 8 nm was prepared by co-precipitation of metal chlorides in an ammonia solution, followed by extensive washing with ethanol, drying and calcining at 550 °C. Powder characteristics as function of thermal treatment are discussed. A copper oxalate precipitation for the preparation of nanocrystalline CuO powders was optimised in order to minimise aggregation and agglomeration. The influence of calcination procedure and synthesis medium on several powder characteristics of the CuO powders were investigated in detail. Oxalate precipitation in ethanol followed by sequential drying and calcination in air at 250 °C in an open tubular furnace with proper air-powder contact area was found to be the optimal procedure for producing nanocrystalline single-phase CuO powder with small aggregates and weak agglomerates. With this optimal procedure a CuO powder with crystallite diameter and BET equivalent particle diameter of respectively 12 and 20 nm was obtained.

Electrical, structural and optical characterization of copper oxide thin films as a function of post annealing temperature

AbstractCopper oxide thin films were obtained by annealing (temperature ranging between 100 and 450 °C) the metallic Cu films deposited on glass substrates by e‐beam evaporation. XRD studies confirmed that the cubic Cu phase of the as‐deposited films changes into single cubic Cu2O phase and single monoclinic CuO phase, depending on the annealing conditions. The crystallite size is varied between ∼12 and 31 nm. The lattice parameters of cubic Cu and Cu2O phases are estimated to ∼3.60 and ∼4.26 Å, respectively. The films with Cu2O phase showed p‐type characteristics. The conductivity is decreased linearly with the decreasing temperature (1/T), which has confirmed the semiconductor nature of the deposited films. The calculated activation energy is varied between 0.10 and 0.16 eV. The surface microstructure is changed depending on the variation in the annealing temperature. The poor transmittance of the as‐deposited films (<1%) is increased to a maximum of ∼80% (800 nm) on annealing at 200 °C. The estimated direct allowed band gap is varied between 1.73 and 2.89 eV.

Third-order nonlinear optical properties of CuO film

Single-phase CuO thin films have been obtained on Si(100) and quartz substrates using pulsed laser deposition technique. The structure, surface image, optical transmittance and reflectance of the films were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy and UV-vis spectroscopy. The SEM image demonstrates that the grain size is about 45nm. The third-order optical nonlinearities in CuO films were investigated by Z-scan method using a femtosecond laser (800nm, 50fs). The results show that CuO films have ultrafast nonlinear optical response and large optical nonlinearity with the real and imaginary parts of third-order nonlinear susceptibility, χ(3), being -7.88×10-11 esu and -2.13×10-11 esu, respectively, indicating CuO thin films are potential materials for applications in nonlinear optical devices.

Nonlinear optical properties of laser deposited CuO thin films

In this work we investigate the third-order optical nonlinearities in CuO films by Z-scan method using a femtosecond laser (800 nm, 50 fs, 200 Hz). Single-phase CuO thin films have been obtained using pulsed laser deposition technique. The structure properties, surface image, optical transmittance and reflectance of the films were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy and UV–vis spectroscopy. The Z-scan results show that laser-deposited CuO films exhibit large nonlinear refractive coefficient, n 2 = − 3.96 × 10 − 17 m 2/W, and nonlinear absorption coefficient, β = − 1.69 × 10 − 10 m/W, respectively.

Controlled growth and characteristics of single-phase Cu 2O and CuO films by pulsed laser deposition

Copper oxide, Cu 2O and CuO, thin films have been synthesized on Si (100) substrates using pulsed laser deposition method. The influences of substrate temperature and oxygen pressure on the structural properties of copper oxide films were discussed. The X-ray diffraction results show that the structure of the films changes from Cu 2O to CuO phase with the increasing of the oxygen pressure. It is also found that the (200) and (111) preferred Cu 2O films can be modified by changing substrate temperature. The formation of Cu 2O and CuO films are further identified by Fourier transform infrared spectroscopy. For the Cu 2O films, X-ray photoelectron spectroscopic studies indicate the presence of CuO on the surface. In addition, the optical gaps of Cu 2O and CuO films have been determined by measuring the transmittance and reflectance spectra.

Electrodeposition of n-type Cuprous Oxide Thin Films

Cuprous oxide (Cu2O) is generally a p-type semiconductor material due to the Cu ion vacancies exist in the crystal lattice. The technique of electrodeposition provides the possibility of depositing Cu2O thin films resulting n-type photoresponses in solar cell devices. By maintaining pH values of the depositing aqueous acetate bath in an appropriate range, Cu2O thin films can be potentiostatically electrodeposited. Single phase Cu2O polycrystalline films can be obtained using this technique. The n-type behavior and the quality of the Cu2O films produced by this technique are demonstrated by the photocurrent, capacitance-voltage, SEM and XRD measurements. Existence of oxygen vacancies in the n-Cu2O films is evident from the photoluminescence measurements. Possibility of using these films in low cost solar cell devices is demonstrated after establishing the n-Cu2O/p-CuxS hetero junction by sulphiding Cu2O thin films.

Template‐Free Hydrothermal Synthesis of CuO/Cu2O Composite Hollow Microspheres.

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Template-free Hydrothermal Synthesis of CuO/Cu2O Composite Hollow Microspheres

CuO/Cu2O composite hollow microspheres with controlled diameter and composition were prepared without the addition of templates and additives by hydrothermal synthesis using Cu(CH3COO)2·H2O as a precursor. Increasing the precursor concentration from 0.02 to 0.2 M increased the diameter of the composite hollow microspheres from 500 nm to 5 μm. Moreover, the content of Cu2O in the composite hollow microspheres increased with increasing the reaction time or/and precursor concentration to produce a range of composite hollow microspheres with Cu2O contents from 20 to 80 wt %. A localized Ostwald ripening mechanism was proposed to account for the formation of CuO/Cu2O composite hollow microspheres. The photocatalytic activity experiment indicated that the prepared CuO/Cu2O composite hollow microspheres exhibited a higher photocatalytic activity for the photocatalytic decolorization of methyl orange aqueous solution under the visible-light illumination than the single phase CuO or Cu2O samples.

Cathodic reduction of the duplex oxide films formed on copper in air with high relative humidity at 60 °C

The cathodic reduction of duplex air-formed oxide film on copper was performed at a constant current density of i c = −50 μA cm −2 in deaerated 0.1 M KCl solution to investigate the sequence of cathodic reduction of each oxide layer and its mechanism. The single-phase thick CuO film on copper was also cathodically reduced at i c = −50 μA cm −2 or −2.5 mA cm −2. The surface characterizations of the air-formed oxide film and single-phase CuO film before cathodic reduction and after partial or complete cathodic reduction were performed by XPS and X-ray diffraction, respectively. The two plateau regions appeared in the potential vs. time curve during cathodic reduction of the duplex air-formed oxide film on copper, while one plateau region was observed in the potential–time curve during cathodic reduction of the single-phase CuO film on copper. The potential in the first plateau region for the air-formed film coincided with that in the plateau region for the CuO film. The results of XPS and X-ray diffraction suggested that in the first plateau region, the outer CuO layer is directly reduced to metallic Cu, while in the second plateau region, the inner Cu 2O layer is reduced to metallic Cu.

Investigation of individual CuO nanorods by polarized micro-Raman scattering

Rod-shaped CuO nanostructures were successfully synthesized by a one-step annealing process in air using copper plates as starting material. Phase analysis was carried out using X-ray diffraction, transmission electron microscopy and micro-Raman scattering and the results confirmed the nanorods as single-phase CuO. For the first time, single individual CuO nanorods with different aspect ratios were investigated by polarized micro-Raman scattering in this work. An obvious anisotropy in the intensity of Raman modes was observed when the electric field vector of the incident laser beam is parallel and perpendicular to the long axis of a nanorod. The mechanism responsible for the observed polarized Raman spectra was attributed to the polarization effect produced by the large length to diameter ratio of the nanorods and the large dielectric contrast between these nanorods and their surrounding environment.

Phase formation in ion irradiated metal-organic complexes of copper-bis-acetylacetonate

Irradiation effects on spin cast films of metal-organic copper-bis-acetylacetone [((CH3CO)2CH)2Cu:Cu(acac)2] have been studied using He+, Ar+, and O+ ionic species. The formation of CuO and paramelaconite (6CuO · Cu2O) phases is observed in the irradiated samples irrespectively of the ionic species. Post irradiation oxygen annealing leads to the formation of a single phase CuO film for the sample irradiated with O+ ions. The formation of a single phase CuO film is assigned to the combination of the fact that the compound formations with higher oxidation states are preferred in the cascade of ions with heavier masses and the presence of excess oxygen in the O+ irradiated sample.

Synthesis of Copper Oxide Nanoparticles by Activated Reactive Evaporation Method

The present study reviews various synthesis techniques for preparing single-phase Cu2O nanoparticles. The ‘nanoparticle route’ results in the growth stable semiconductor materials via the size-induced stabilization at nanodimension. In comparison to other techniques, activated reactive evaporation (ARE) method has an excellent parametric control to obtain the nanoparticles in a wide size range. The size-dependent optical, structural and electronic properties of Cu2O nanoparticles prepared by ARE method have been discussed in detail. Increase in ionic nature of the Cu2O lattice and a surface-modified thin CuO shell surrounded Cu2O core stabilizes the Cu2O phase. High-energy heavy ion irradiation has been used to modify the nanocrystalline characteristics of the Cu2O nanophase without destroying nanoparticle nature. These results show that Cu2O nanoparticles based Schottky and heterojunction will be stable to yield better photovoltaic performance.

Formation of Single-phase CuO Quantum Particles

CuO nanocrystals of three different sizes 3.5, 6.5, and 10.0 nm were synthesized by a novel electrochemical route. Quantum size effects in these nanocrystals are evident from the optical absorption spectra. The optical absorption feature is observed to be blue shifted by about 1 eV with size reduction. The CuO q-particles were found to be single-phased and very stable as far as the size and phase is concerned.

On the Influence of Non-Protective CuO on High-Temperature Oxidation of Cu-Rich Cu-Ni Based Alloys

A number of copper-rich Cu-Ni alloys wereoxidized from 750 to 1000°C at differentoxygen pressures. The oxide scales formed consist of anouter copper oxide layer and an inner porous layer where internal oxide-derived NiO particles aredispersed in a copper oxide matrix. The copper oxide maybe both single-phase CuO and a two-phase(CuO+Cu2O). At the lower part of thetemperature range, the oxidation kinetics and oxidemorphology depend strongly upon the formation of CuO.The CuO layer is nonprotective and further oxidation ofCu2O, forming CuO, therefore changes the oxidation from being approximately parabolic tohaving a breakaway-like behavior. The relative thicknessof nonprotective CuO increases with increasing NiO andreflects that the solid-state flux of copper across the Cu2O decreases due to abarrier effect of the NiO particles and porosity in theoxide and NiO particles in the alloy. The beneficialeffect of Ni in reducing the oxidation rate is lost due to the extensive formation ofnonprotective CuO.

Synthesis and Raman Spectra of Cupric Oxide Quantum Dots

ABSTRACTWe have synthesised CuO quantum dots by using a method of one-step solid state reaction under ambient conditions, and investigated them by X-ray diffraction (XRD), transmission electron microscopy (TEM), and Raman scattering technique. The XRD shows that the sample is composed of single phase CuO with a monoclinic structure. The particle size estimated from the x-ray diffraction peaks is about 12 nm, consistent with the TEM result. The Raman spectra show that there are three Raman peaks at 282, 332 and 618 cm−1, which are much broader and shifted several cm−l to lower frequencies in comparison with those of bulk CuO crystal. The temperature dependence of the Raman spectra in the range 77–873 K is also presented.

Copper Oxide Thin Films Prepared from Copper Dipivaloylmethanate and Oxygen by Chemical Vapor Deposition

Polycrystalline copper oxide thin films have been prepared from copper dipivaloylmethanate and oxygen by an atmospheric-pressure chemical vapor deposition method at a reaction temperature of 300°C. The deposition at oxygen partial pressure (p0) ≦2.13 kPa forms single-phase Cu2O with [100] oriented polycrystalline structure, in which Cu+ is partially substituted by Cu2+ in proportion to the increase in oxygen partial pressure from 1.06 kPa. The optical energy gap decreases from 2.5 to 1.8 eV with the increasing Cu2+ fraction in the film. At p0 ≧2.48 kPa, the crystalline CuO is formed with nonoriented crystalline Cu2O. The content of the CuO phase markedly increase with increasing oxygen partial pressure.

Electrical and Optical Properties of Copper Oxide Films Prepared by Reactive RF Magnetron Sputtering

Copper oxide thin films were prepared by reactive rf magnetron sputtering of a pure copper target in an oxygen-argon atmosphere. The phases of the deposited films strongly depend on the oxygen content in the sputtering gas. X-ray diffraction studies show that by controlling the oxygen partial pressure single phase Cu2O and CuO can be obtained. The resistivity of the Cu2O film in the present study is 43 Ω cm. The optical constants were evaluated from transmission and reflection measurements.

Cathodic arc deposition of copper oxide thin films

Black CuO films are used for improved radiation cooling of, e.g. an r.f. kicker at the Advanced Light Source of Lawrence Berkeley Laboratory. The films are required to be transparent to r.f. fields particularly in the range 1–1.25 GHz, UHV compatible, and very adhesive even after a number of baking cycles. Usual techniques such as wet-chemical coating do not fulfil the requirements for UHV compatibility. A cathodic arc plasma source with a copper cathode was operated in an oxygen atmosphere to form CuO films on the substrate, which was either the anode or was mounted on a substrate holder using a separate anode. The films are single-phase polycrystalline CuO. They are slightly oxygen-rich, adhere very well (pull strength exceeding 85 MPa) and fulfil all UHV requirements. The deposition method is very efficient, and large workpieces up to a surface area of 5000 cm 2 have been coated.