Copper Oxide Films Research Articles

Nanostructuring of anodic copper oxides in fluoride-containing ethylene glycol media

We demonstrate that the anodization of copper in alkaline water/ethylene glycol media containing fluoride ions generates nanostructured copper oxide films. By modifying the anodization conditions (fluoride and OH– concentrations, applied voltage and anodization time), nanofibrillar Cu2O as well as highly rough nanofibrillar network or nanoporous mixed Cu2O/CuO films are obtained. Raman and X-ray Photoemission Spectroscopy (XPS) results indicate that in fluoride presence, Cu(I) oxide is obtained when anodization takes place applying low voltages at a relatively low OH– concentration. In comparison, the subsequent oxidation to obtain Cu(II) species (CuO and Cu(OH)2) is promoted by increasing the OH– contents. According to the present results, an oxidation reaction scheme is proposed in order to gain a deeper understanding in the preparation of controlled nanostructured copper oxide films.

Effects of RF plasma treatment on spray-pyrolyzed copper oxide films on silicon substrates

The effects of radio-frequency (RF) argon (Ar) plasma treatment on the structural, morphological, electrical and compositional properties of the spray-pyrolyzed p-type copper oxide films on n-type (100) silicon (Si) substrates were investigated. The films were successfully synthesized using 0.3 M copper acetate monohydrate sprayed on precut Si substrates maintained at 350 °C. X-ray diffraction revealed cupric oxide (CuO) with a monoclinic structure. An apparent improvement in crystallinity was realized after Ar plasma treatment, attributed to the removal of residues contaminating the surface. Scanning electron microscope images showed agglomerated monoclinic grains and revealed a reduction in size upon plasma exposure induced by the sputtering effect. The current–voltage characteristics of CuO/Si showed a rectifying behavior after Ar plasma exposure with an increase in turn-on voltage. Four-point probe measurements revealed a decrease in sheet resistance after plasma irradiation. Fourier transform infrared spectral analyses also showed O–H and C–O bands on the films. This work was able to produce CuO thin films via spray pyrolysis on Si substrates and enhancement in their properties by applying postdeposition Ar plasma treatment.

Role of Ar/O2 mixture on structural, compositional and optical properties of thin copper oxide films deposited by DC magnetron sputtering

In this study, the effect of oxygen content on a thin copper oxide layer deposited on BK7 and steel substrates by DC magnetron sputtering were investigated. Argon as working gas with impurity of 99.9% and various oxygen ratios were used to sputter a pure Cu cathode target in a cylindrical geometry. The produced samples were analyzed by X-ray diffraction (XRD), energy-dispersive X-ray (EDX), atomic force microscopy (AFM), and spectrophotometry techniques. The films thickness was measured by profilometer facility. The results show that by increasing oxygen content in the working gas the sputtering rate reduces. Moreover, the type of oxide phase (Cu2O or CuO) in the synthesized layer and consequently its optical properties dramatically depend on Ar/O2 ratio in the working gas.

An effect of temperature on structural, optical, photoluminescence and electrical properties of copper oxide thin films deposited by nebulizer spray pyrolysis technique

In this work, copper oxide thin films were deposited on glass substrate by nebulizer spray pyrolysis technique with different temperatures (i.e. 250–320°C). All the deposited films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), Laser Raman, UV–Vis, Photoluminescence and Hall Effect measurements for the Structural, morphological, vibrational, optical and electrical properties. The XRD studies confirmed that the films deposited with different temperatures from 250 to 300°C possess single cubic crystal structure phase of cuprous oxide (Cu2O) whereas the films deposited at 310 and 320°C were found to have a mixed phase of CuO and Cu2O. When the temperature reaches above 310°C the Cu2O phase become unstable and started to convert as CuO. Laser Raman studies confirmed that the observed peaks at 109, 148, 219, 416,515 and 635cm−1 are belong to Cu2O phase deposited at 250 and 280°C. However, the films deposited at 310°C and 320°C having additional peaks at 273, 327 and 619cm−1 which conforms the presence of mixed (CuO and Cu2O) phase. The AFM studies shows that the deposited films has uniformly distributed with homogeneity and the particles extended all over the surface. Optical measurement showed that the band gap of deposited thin films in the range of 2.44–1.97 for 250–320°C, respectively. A single and strong emission peak at ~ 617nm is observed in PL spectra, which conforms the copper oxide film. Hall Effect measurements showed that all the films are of p-type conductivity with resistivity (ρ) of 4.61 × 102Ωcm, carrier concentration (n) of 13.53 × 1015cm−3 and mobility of 1.0cm2/vs at 320°C temperature. The low activation energy of 0.012eV were observed for the film deposited at 320°C.

Anodic copper oxide nanowire and nanopore arrays with mixed phase content: synthesis, characterization and optical limiting response

Thin films consisting of copper oxide nanowires (NWs) containing a mixture of copper oxide phases were formed by electrochemical anodization in de-ionized water (DI) and methanol based electrolytes. Well-defined arrays of vertical nanopores were obtained via anodization in ethylene glycol (EG)-based electrolytes. Optical absorption spectra revealed the electronic bandgap of the NWs formed in DI and methanol to be 2.50 eV, and that of nanopores formed in EG electrolytes to be 1.94 eV. The nanostructures were found to exhibit p-type conduction through Mott–Schottky analysis. The as-formed nanostructures exhibited two photon photoluminescence with lifetimes ranging between 200 and 1100 ps. They also displayed strong optical limiting in the form of a 25% decrease in optical transmission at 800 nm at a relatively low fluence of 0.1 J cm−2 and an absolute transmittance <50% over the entire range of laser fluence values used in this study. The optical transmittance decreased from 40% at an incident Ti-sapphire laser fluence of 20 mJ cm−2 to ∼9% when the fluence was increased to 700 mJ cm−2. Furthermore, the damage threshold of 0.7 J cm−2 compares favorably with advanced optical limiting materials such as gold-graphene composites and single-walled carbon nanotube composites even without further optimization of nanoscale morphology to maximize scattering. Therefore the nanostructures of mixed copper oxide films studied in this report are particularly promising as optical limiters for protecting low damage threshold (<1 J cm−2) photonic devices and are an important addition to the narrow selection of optical limiting materials that are currently available.

Cu2O epitaxial films with domain structures prepared on Y-stabilized ZrO2 substrates by pulsed laser deposition

Abstract Copper oxide films have been deposited on the Y-stabilized ZrO2 (YSZ) (100) substrates by pulsed laser deposition and the effect of oxygen pressure (PO2) on the film properties was investigated in detail. The phase, crystallinity, and surface morphology of the films were strongly influenced by PO2 and the film prepared at 0.09 Pa was pure cuprous oxide (Cu2O) having the best film crystallinity. An out-of-plane epitaxial relationship of Cu2O (110)∥YSZ (100) with six different kinds of domain structure were observed for the 0.09 Pa-deposited sample and the corresponding in-plane epitaxial relationships were deduced. The lowest resistivity of 13.4 Ω cm and highest Hall mobility of 16.3 cm2 v−1 s−1 were also obtained for the film deposited at 0.09 Pa. The optical band gap of the as-prepared copper oxide films varied from 2.37 to 2.57 eV.

Characterisation of Cu2O, Cu4O3, and CuO mixed phase thin films produced by microwave-activated reactive sputtering

Copper readily forms three oxides, CuO, Cu4O3 and Cu2O, widely recognised as the most promising p-type oxides because of their desirable optical and electrical properties and potential use in solar cells, transparent electronics as well as other specialised applications such as electrodes for rechargeable lithium batteries, catalysis and memristors. For large-scale implementation of devices, magnetron sputtering is a practical method of producing metal oxides; however, sputtered copper oxides tend to form as a mixture of the oxides, with Cu2O being particularly difficult to produce reliably in pure form. Here, nanostructured thin films of copper oxides were prepared by a variation on reactive sputtering known as microwave-activated reactive sputtering under various rates of oxygen flow. Microwave-activated reactive sputtering was shown to be a suitable technique for the inexpensive production of large areas of copper oxide thin films at near room temperature, facilitating deposition on a wide variety of substrates including polymers. Furthermore, it was demonstrated that the sputtered films develop through CuO, Cu4O3 and Cu2O mixed phases as oxygen flow rate is increased. The preparation of a given stoichiometry for a particular application can be achieved by varying the flow rate of oxygen during the microwave-activated reactive sputtering process.

Control of the Structure of Diffusion Layer in Carbon Steels Under Nitriding with Preliminary Deposition of Copper Oxide Catalytic Films

The effect of thin films of copper oxide deposited before nitriding on the phase composition and the kinetics of growth of diffusion layers in carbon steels is considered. The process of formation of an oxide film involves chemical reduction of pure copper on the surface of steel specimens from a salt solution and subsequent oxidation under air heating. The oxide film exerts a catalytic action in nitriding of low- and medium-carbon steels, which consists in accelerated growth of the diffusion layer, the nitride zone in the first turn. The kinetics of the nitriding process and the phase composition of the layer are controlled by the thickness of the copper oxide precursor, i.e., the deposited copper film.

Dual functionality anti-reflection and biocidal coatings

A thin film combination of anti-reflection (AR) and biocidal properties would be of particular interest to reduce the transfer of infection and improve readability of public high use touch screens. In this paper we describe the development of a dual functionality film of silica (AR) and copper oxide (biocidal). Deposition was via flame assisted chemical vapour deposition (FACVD) which has the advantages of being a cost efficient atmospheric pressure technique enabling use of non-volatile precursors and that no closed reaction cell is required so making it ideal for integration into industrial production lines. The resulting films were characterised by a range of techniques including optical spectroscopy, electron microscope and X-ray fluorescence. Biocidal behaviour was tested by determining the kill rate of Escherichia coli.A 3 layer stack on glass of silica/copper oxide/silica had better adhesion and lower reflection than a comparable 2 layer stack. This multilayer film led to a >2% drop in reflection from that of uncoated glass, similar to that of silica only film. In addition, showed a >6 log10 kill between 6 and 24h for as deposited and annealed samples.

H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;S dosimeter with controllable percolation threshold based on semi-conducting copper oxide thin films

Abstract. Copper oxides, such as CuO and Cu2O, are promising materials for H2S detection because of the reversible reaction with H2S to copper sulfides (CuS, Cu2S). Along with the phase change, the electrical conductance increases by several orders of magnitude. On CuOx films the H2S reaction causes the formation of statistically distributed CuxS islands. Continuous exposition to H2S leads to island growth and eventually to the formation of an electrical highly conductive path traversing the entire system: the so-called percolation path. The associated CuOx ∕ CuxS conversion ratio is referred to as the percolation threshold. This pronounced threshold causes a gas concentration dependent switch-like behaviour of the film conductance. However, to utilize this effect for the preparation of CuO-based H2S sensors, a profound understanding of the operational and morphological parameters influencing the CuS path evolution is needed.Thus, this article is focused on basic features of H2S detection by copper oxide films and the influence of structural parameters on the percolation threshold and switching behaviour. In particular, two important factors, namely the stoichiometry of copper oxides (CuO, Cu2O and Cu4O3) and surface morphology, are investigated in detail. CuOx thin films were synthesized by a radio frequency magnetron sputtering process which allows modification of these parameters. It could be shown that, for instance, the impact on the switching behaviour is dominated by morphology rather than stoichiometry of copper oxide.

Mono-fractal analysis of CuXO films: Texture and phase distribution

Several studies on thermally-grown copper oxide films dealing with their crystalline properties and main phases as functions of the growth temperature have been published; notwithstanding, few research works have proposed a description of the surface morphology of the films using mono-fractal analysis. In this work, copper oxide films were grown by direct thermal oxidation in atmospheric air at different temperatures and times to obtain experimental proof of the phases present in the films by XRD, FTIR and Raman. The textural properties of the copper oxide films were analyzed from atomic force microscopy (AFM) images. The box counting and information fractal dimensions were used to perform the mono-fractal analysis to establish a correlation between the textural properties and the phases of the CuxO films.

Rapid synthesis strategy of CuO nanocubes for sensitive and selective detection of NO2

Abstract In present work, copper oxide (CuO) films have been successfully synthesized onto a quartz substrate using a simple and catalyst-free thermal evaporation technique and their chemiresistive properties were carried out towards host of target gases. Structural analysis demonstrates the formation of polycrystalline single phase monoclinic CuO. Formation of nanocubes–type of surface morphology of CuO was observed from morphological investigation. Gas sensing results demonstrate that the CuO films, composed of nanocubes (NCs), are highly selective towards oxidizing nitrogen dioxide (NO 2 ) gas than other target gases along with rapid response and recovery times. CuO sensor films exhibit the maximum response value of 76%–100 ppm NO 2 @150 °C. In addition, CuO films are able to sense as low as 1 ppm concentration of NO 2 gas. The effect of operating temperature on the NO 2 sensing properties of CuO films was thoroughly investigated and reported. Impedance spectroscopy was used to study the interaction mechanism between CuO sensor film and NO 2 gas molecules.

Thermally evaporated copper oxide films: A view of annealing effect on physical and gas sensing properties

The present paper reports a facile approach to prepare copper oxide (CuO) films directly onto a glass substrate by thermal evaporation method and their chemiresistive properties towards hazardous nitrogen dioxide (NO2). The influence of annealing temperature on structural, morphological, and gas sensing properties of the CuO films has been thoroughly investigated and reported. Structural and morphological analyses has confirmed the formation of polycrystalline monoclinic CuO with uniformly distributed nanoparticles over the substrate surface. Gas sensing measurements on CuO films reveal the high response, excellent selectivity, fast response-recovery time signatures, good repeatability, and stability towards lower concentration of NO2 gas @150°C. A maximum response of 48% towards 100ppm NO2 has been achieved. Gas sensing results demonstrate an influence of morphology on the NO2 sensing performance of CuO films. In addition, the interactions between CuO sensor film and NO2 gas molecules are studied through an impendence spectroscopy analysis.

Copper Oxide Film In-situ Electrodeposited from Cu(II) Complex as Highly Efficient Catalyst for Water Oxidation

Water splitting is deemed as an effective pathway for producing ideal clean energy, such as hydrogen. Here, a copper oxide film (Cu-Tris film) was prepared in-situ from a 0.2M phosphate buffer solution (pH=12.0) containing 1.0mM Cu2+ and 2.0mM Tris via controlled-potential electrodeposition. The Cu-Tris film showed a significantly low overpotential of 390mV at a current density of 1.0mA/cm2 for electrocatalytic water oxidation. Simultaneously, a considerably low Tafel slope of 41mV/decade was achieved. This Cu-Tris film also exhibited a high and stable current density of ca. 7.5mA/cm2 at 1.15V vs. NHE for long-term electrocatalysis (10h). These results demonstrated the superior performance of the developed Cu-Tris film, which should be attributed to the regulating effect of the five coordinated planar structure of the Cu-Tris complex precursor during the process of electrodeposition.

Studies on copper oxide thin films prepared by simple nebulizer spray technique

Copper oxide films were deposited by simple nebulizer spray pyrolysis technique using aqueous solution of Copper(II) acetate monohydrate, high pure glucose and 20 vol% of 2-propanol. Structural, morphological, optical and electrical properties of the deposited films were characterized by XRD, Laser Raman, AFM, UV–Vis and Hall Effect measurements. The XRD study confirmed that the copper oxide films are in polycrystalline form of cuprous oxide (Cu2O) phase with cubic crystal structure for the films deposited using precursor volumes of 3 and 4 ml, whereas the films deposited using 5 ml precursor solution are in cupric oxide (CuO) phase with monoclinic crystal structure. The higher concentration films shows higher thickness (~ 600 nm for 5 ml) and that change the phase/composition of the films. The prepared CuO films with 5 ml precursor solution are expected to show better properties. AFM studies revealed that the surfaces of the films are very smooth with uniformly distributed grains. The surface roughness of the film was increased with volume of the solution and the grain islands were coalesced with each other. UV visible spectrophotometer measurements showed that the band gap value of the prepared copper oxide thin films is varied between 1.63 and 1.23 eV due to change of volume of the solution. Hall Effect measurement showed that the prepared films are in p-type conductivity with 8.21 ×102 Ω-cm resistivity (ρ) and 12.56 ×1015 cm−3 carrier concentration (n) for the films prepared at 5 ml solution. All the studied properties of CuO for 5 ml precursor solution are remarkably changed.

Formation and characterization of infrared absorbing copper oxide surfaces

Copper oxide formation has been investigated to combine the advantages of producing different size and shapes of coatings that possess good light absorbing properties. An aqueous blackening solution was investigated and optimum composition was found as 2.5M NaOH and 0.225M NaClO to form velvet copper oxide films. A two-step oxidation mechanism was proposed for the blackening process by carefully examining the experimental results. Formation of Cu2O was observed until the entire copper surface was covered at first. In the second step, Cu2O surface was further oxidized to CuO until the whole Cu2O surface was covered by CuO. Therefore, blackened copper surfaces consisted of Cu2O/CuO duplex oxides. Characterization of the coatings were performed in terms of microstructure, phase analysis, chemical state, infrared specular and total reflectivity by SEM, XRD, XPS, FTIR and UV–vis spectrophotometry, respectively.

Нанесение окрашенных декоративных покрытий на поверхность конструкционных сталей

Introduction. Chemical decorative treatment of steel consists in painting steel products and applying oxide films to the surface to create an attractive appearance and prevent the product from rust. Staining copper organic compounds with aqueous solutions has the following feature: the coating color varies depending on the resistance time in solution, which is associated with changing in thickness of the forming oxide layer where interference phenomena occur. For a wide application of this method, studies are needed to investigate the relationship between the staining modes and the resulting coating color. The work objective is to establish relationship between the coating staining obtained from alkaline copper-containing solutions and their quantitative and qualitative phase composition. Materials and Methods. The phase composition of the coatings obtained was studied by the method of local electrochemical analysis (LEA) based on the cathodic reduction of the oxide phases of the coatings in the galvanopulse mode using a clamp sensor. From the obtained impulse chronopotentiograms, the potential values at the pause moment were considered, and then these values were compared to the standard potentials of various redox pairs of copper oxides. Research Results. The analyzed coatings were formed during different time of holding the sample in solution and had a different color. The data of the redox pair correspond to: [[Сu(OH) 4 ] 2- /Cu - adsorption layer of hydroxocuprate-anions on the surface of electrodeposited copper steel; Cu(OH) 2 /Cu - adsorption layer of copper hydroxide on the surface of electrodeposited copper; Cu 2 О/Cu - oxide film of copper oxide (I) on copper. This equates to conclude about the colored coatings composition on the samples studied. Brown, violet and blue films formed during the initial period of exposure of the copper coating in solution contain adsorbed hydroxocuprate and copper hydroxide. Blue, yellow and lilac films formed over a longer period of time contain, in addition to these phases, copper oxide (I). Discussion and Conclusions. From the data obtained, it follows that the management of the color change time required in various technological applications can be carried out through changing the concentration of copper sulfate, as well as an organic reducing agent. The mechanism of coating coloration is affected by the adsorption layers formed on the steel surface. By varying the aging time of the sample in the electrolyte, it is possible to control the phase composition of the adsorption layers, and, consequently, influence the coating colorability.

CuOX thin films by direct oxidation of Cu films deposited by physical vapor deposition

Thin films of Cu2O and CuO oxides were developed by direct oxidation of physical vapor deposited copper films in an open atmosphere by varying the temperature in the range between 250 and 400 °C. In this work, the influence of oxidation temperature on structural, optical and electrical properties of copper oxide films has been discussed. The characterization results revealed that at lower temperatures (<300 °C), it is feasible to obtained coper (I) oxide whereas at temperatures higher than 300 °C, the copper (II) oxide is formed. The band gap is found to vary in between 1.54 and 2.21 eV depending on the oxidation temperature. Both oxides present p-type electrical conductivity. The carrier concentration has been increased as a function of the oxidation temperature from 1.61 × 1012 at 250 °C to 6.8 × 1012 cm−3 at 400 °C. The mobility has attained its maximum of 34.5 cm2 V−1 s−1 at a temperature of 300 °C, and a minimum of 13.8 cm2 V−1 s−1 for 400 °C. Finally, the resistivity of copper oxide films decreases as a function of oxidation temperature from 5.4 × 106 to 2.4 × 105 Ω-cm at 250 and 400 °C, respectively.

ギ酸による銅酸化膜還元過程のリアルタイム測定と考察

ギ酸による銅酸化膜還元過程のリアルタイム測定と考察

Hydrophobicity and tribology of large-area textured copper with nanogrown copper oxide

Copper (Cu) is widely used as an engineering material for automotive industries. Herein, a two-step surface innovation process was evolved to enhance the hydrophobicity and wear resistance of the copper surface. Rapid fabrication of large-area texturing was performed by the abrasive water jet technique followed by nanogrowth of copper oxide (CuO) film on the copper substrate. Increased hydrophobicity is observed for textured copper (120°) and copper with nanogrown CuO (133°) compared to that of copper without these features (63°). It may be noted that synergistic texturing and nanogrowth of CuO has resulted in the highest contact angle (155°). X-ray photoelectron spectroscopy revealed the least percentage contribution of Cu–OH group to synergetic texture and nanogrowth (1·25 %). Further, the fretting wear test divulged the high wear resistance of synergistically textured copper with nanogrown CuO, as its coefficient of friction was lowest (0·46) when compared with that of copper (0·52). The observed improvement in wear resistance is attributed to textured pillars trapping the wear debris and reduction in the real contact area due to nanogrown CuO. Thus, this novel large-area texturing technique combined with nanogrown CuO may provide potential self-lubrication and render superhydrophobic surfaces for automotive applications.