Cu2O Films Research Articles

Mn‐Doped CuO Nanostructure Films Based Gas Sensor for High Sensitive and Selective Formaldehyde Detection at a Room Temperature

AbstractThe development of an efficient gas‐sensing materials is crucial for applications in healthcare, industry, environmental monitoring, and agriculture. In this study, Mn‐doped CuO thin films were synthesized and evaluated for their gas‐sensing properties. The fabricated films exhibited a monoclinic CuO structure with (002) and (111) orientations, and their morphology reveals a uniform, spherical‐like crystalline distribution. Mn doping adjusts the optical bandgap from 2.11 eV to 2.03 eV. Compared with pure, 3% Mn‐doped CuO‐based sensor demonstrated a high response value of 82% to 20 ppm formaldehyde at room temperature with swift response and recovery times of 9 and 36 s, respectively. The high sensitivity and stability of these sensors make Mn‐doped CuO films a promising candidate for practical gas detection applications.

Effect of Process Pressure on the Properties of Cu2O Thin Films Deposited by RF Magnetron Sputtering

Cu2O thin films were deposited on soda-lime glass substrates using RF magnetron sputtering under various process pressures, and their structural, morphological, compositional, and optical properties were investigated. X-ray diffraction (XRD) revealed that the films crystallized in the cubic Cu2O phase, with the highest crystallinity observed at 5 mTorr, as evidenced by the sharp and intense (111) peak. Raman spectroscopy confirmed the predominance of Cu2O vibrational modes across all samples, with improved phase purity and crystallinity at 5 mTorr and 10 mTorr. Field-emission scanning electron microscopy (FE-SEM) showed that the films deposited at 5 mTorr and 10 mTorr exhibited densely packed, well-defined grains, while those at 1 mTorr and 15 mTorr displayed irregular or poorly defined morphologies. X-ray photoelectron spectroscopy (XPS) confirmed the presence of Cu(I) without significant secondary phases, with slight surface oxidation observed at higher pressures. Optical characterization revealed that transmittance increased with pressure, reaching ~90% in the NIR range at 15 mTorr. The optical band gap (Eg) values increased from 2.34 eV at 1 mTorr to 2.43 eV at 15 mTorr with higher process pressure. Cu2O films deposited at 5 mTorr and 10 mTorr exhibited an optimal balance between high transparency and band gap values. These findings highlight the critical role of process pressure in determining the properties of Cu2O thin films and identify 5 mTorr as the optimal deposition condition for achieving high-quality films with superior structural and optical performance.

Enhancing the Photoelectrochemical Activity of CuO/ZnO Junction Photocathodes for Water Splitting.

To facilitate fast transfer of photogenerated electrons and surface stability, the CuO photocathode needs to be coupled with another heterojunction material. Here, we propose CuO/ZnO heterojunctions as photocathodes for photoelectrochemical (PEC) water splitting. First, CuO was grown on a Cu substrate, either in the form of a foil or mesh gauge, via anodization followed by postheating treatment. Subsequently, ZnO was electrodeposited on the grown CuO. The grown CuO film was composed of two-dimensional nanoplates aligned vertically against the substrate. The film morphology changed to flower-like or nearly spherical when ZnO was deposited by electrodeposition. Based on its open-circuit potential (OCP), overpotential and current density, CuO/ZnO grown on the Cu mesh exhibited better PEC performance than its counterpart grown on the Cu foil. When the mesh substrate was used, the surface area of the grown nanostructures was high and reached approximately 102.42 m2 g-1. The OCP of the CuO/ZnO mesh reached a low value of approximately -137 mV; this value quantitatively indicated that its PEC activity was more favorable for the hydrogen evolution reaction (HER). Moreover, the overpotential at the benchmark current density of 10 mA cm-2 for the Cu mesh was 379 mV, and this value was lower than those of the other photocathode materials.

Controllable synthesis of high porous CuO film on ZnO via electrodeposition for improved sensitivity and stability in nonenzymatic glucose sensing

A facile electrodeposition process is employed to synthesize Cu2O nanoparticle aggregates on ZnO layer for glucose sensing. The electrolytes (CuSO4/lactic acid, pH 11 ∼ 12, 65 °C and CuSO4/lactic acid/K2S2O8, pH 9, RT) and deposition times (30 to 7200 s) were investigated to optimize the structures and morphologies of the Cu2O layer. After annealing, the resulted ZnO/CuO electrode of 1800 s electrodepositing in CuSO4/lactic acid/K2S2O8 showed high current response, presenting a linear range from 10 μM to 1 mM (R2 = 0.999) with the high sensitivity of 1.43 mA/mM cm2 and the detection limit of 1.1 μM. Moreover, the long-term current responses revealed that the electrodeposited ZnO/CuO nanostructure exhibited good stability (RSD 8.2 %, 60 min) in 0.1 M NaOH.

(Invited) Development of High-Efficiency Transparent Cu2O Top Cells for Tandem Photovoltaics with Efficiency Exceeding 30%

Solar cells with high power generation efficiency are expected to be used in mobility applications that require high power output in a limited footprint, such as electric vehicles (EVs) and high-altitude platform stations (HAPS), as well as in current products for housing and industrial applications. A tandem structure is an effective option for high-efficiency solar cells, and various combinations of solar cells have been proposed as the top and bottom cells, including InGaP/GaAs and perovskite/Si. Our proposed tandem solar cell consists of a transparent cuprous oxide (Cu2O) top cell and a crystalline Si bottom cell and is a promising candidate for the next generation of tandem solar cells because of its combination of high efficiency and low cost. High tandem efficiency of 30% or higher is required for various advanced applications such as mobility. Cu2O has a wide bandgap of 2.1 eV, and its spectral sensitivity complements that of crystalline Si, so high bottom-cell efficiency can be achieved. By using Cu2O in the top cell, the Si bottom cell can be expected to have an efficiency of 20% due to long-wavelength light transmitted through Cu2O, and by generating an efficiency of 10% in the Cu2O top cell, a tandem efficiency exceeding 30% is within sight. Cu2O is a low-cost material because it consists of the abundant elements copper and oxygen. Also, it can be formed on inexpensive glass substrates by low-cost manufacturing processes such as sputtering. We have established a technology to deposit high-quality Cu2O thin films as a single phase on transparent electrodes by reactive sputtering. By precisely adjusting the oxygen gas flow rate and substrate temperature, Cu and CuO present as different phases could be removed and a metastable Cu2O phase selectively deposited. A top cell using this low-defect Cu2O as the optical absorption layer has achieved an efficiency of 8.4% [1]. In this paper, we report on a Cu2O top cell that exhibits the world's highest efficiency of 10.5%, which was achieved by improving the short-circuit current density (Jsc) and the open-circuit voltage (Voc). By increasing the size of the Cu2O top cell by a factor of about 3, the area ratio of the dead area at the cell edge to the power-generating area was reduced. We expect that our Cu2O film has a long carrier diffusion length, and thus when the cell area is small, many carriers diffuse to the cell edge face and recombine. By contrast, a larger cell area increases the number of carriers that can contribute to power generation without carriers reaching the cell edge face. Device simulations showed that there were many interfacial defects between p-type Cu2O and n-type Ga2O3, which reduced Voc. Therefore, a unique passivation layer was introduced at the pn interface. This suppressed the interfacial defects and increased Voc by about 0.1 V compared with the conventional cell. The measured efficiency of 10.5% for the Cu2O top cell exceeds our milestone target of 10% for top-cell efficiency, which is required to achieve tandem efficiency of 30%.This work is based on results obtained from a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO).[1] S. Shibasaki, Y. Honishi, N. Nakagawa, M. Yamazaki, Y. Mizuno, Y. Nishida, K. Sugimoto, and K. Yamamoto, "Highly transparent Cu2O absorbing layer for thin film solar cells," Appl. Phys. Lett. 119, 242102 (2021).

(Invited) Advanced Plated Cu Metallization for Hybrid Bonding and 3D Interconnects

Semiconductor packaging has been developed to meet the requirement of high-density input/output terminals and downsizing. For further high performance and functionality, the research and development on System in Package (SiP), which achieves interconnection between heterogeneous devices in a package, goes on. There are various packaging configurations suggested, such as 2.1D SiP and 2.3D SiP using organic substrates, 2.5D SiP using Si substrates with TSV, and 3D SiP using TSV with microbump or Cu-SiO2 hybrid bonding [1][2][3]. Hybrid bonding using Cu-Cu direct bonding technology is gaining greater momentum owing to its ability to form the ultra-scaled interconnection at much reduced pitches below 5 µm. While improving the quality of Cu-Cu bonding plays a critical role in enhancing the performance of 3D SiP, reducing the resistance of Cu-Cu junctions is one of the most important strategies. Therefore, the additive chemistry for plated Cu plays a significant impact in advanced 3D packaging.In our recent study, we succeeded in making large Cu grain at low temperature, which shows good physical properties by controlled Cu grain size and orientation We defined plating solution A as the low crystal growth process and solution B as the high crystal growth process. Fig.1 shows the SIM images of the cross-section of Cu pretreated with FIB; it was indicated that Cu film plated with solution A shows a grain size under 2 µm, while solution B shows a grain size over 5 µm. Plated Cu with large grains showed high electrical conductivity and thermal conductivity. We concluded that the results are due to the large Cu grains exhibited less grain boundary than polycrystalline Cu having various orientations; therefore, the large grains are appropriate as an interconnecting material [4]. Additionally, we applied the large Cu grains to Cu-SiO2 hybrid bonding and confirmed quite low electrical resistance. We demonstrated that the interface of Cu bonding plated with solution B showed large Cu grains, and Cu crystal orientation of the top and bottom are identical compared with solution A.On the other hand, it is also important to control oxidation since copper oxide film is expected to affect electrical properties in Cu-Cu direct bonding. Therefore, we have investigated the dominant factors that affect the oxidation of plated Cu. Generally, the oxidation reaction of Cu first produces the monovalent Cu ion Cu+, which undergoes CuOH to form a cuprous oxide Cu2O film on the Cu surface. When exposed to an oxidizing environment, cupric oxide CuO is grown. The thickness of copper oxide film formed after annealing at 150 degrees Celsius for 1 hour was measured by the sequential electrochemical reduction analysis (SERA) method, which is capable of distinguishing CuO and Cu2O. Consequently, the copper oxide film grown after annealing mainly consisted of Cu2O, and we have confirmed that the thickness of Cu2O was highly related to additive factors such as concentration and molecular weight. For instance, it was increased logarithmically with increasing molecular weight of polyethylene glycol (PEG), a commonly used suppressor in acid plating solution. The concentration of the brightener showed a proportional relationship to the thickness of Cu2O, and the charge density of the levelers was one of the most significant factors affecting the oxidation of plated Cu among the factors examined in this study. Further evaluation of how additives in the plating solution affect oxidation and its applications, such as Cu-Cu bonding, will be presented at the conference.

Effect of Local pH Change on Galvanostatic Deposition of n-Type Cu2o in Acidic Media: A Chronopotentiometry Study

N-type cuprous oxides (Cu2O) were electrodeposited on Fluorine-doped Tin Oxide (FTO) coated glass substrate in acidic media. We investigated the chrono-potentiometry behavior of the deposited Cu2O films across various current densities. Lower current densities exhibited stable potentials, while higher densities resulted in sharp spikes followed by stabilization. Notably, our study in an acidic medium did not manifest potential oscillations typically observed in alkaline systems. Remarkably, we observed negative potential spikes in the chronopotentiometry curve, particularly at higher current densities exceeding -0.2 mA cm-2, which remains a highlight of our findings. The potential spike indicates the likelihood of a second reaction, the formation of Cu. We argue that the formation of Cu originates from the reduction of Cu2O rather than bulk deposition, primarily due to the change in local pH near the working electrode during the Cu2O deposition process. Continuous stirring of the electrolyte aids in delaying the Cu2O to Cu conversion reaction (Cu2O corrosion), with further influence observed by altering the rotation speed during stirring. Unlike the well-explored galvanostatic deposition of Cu2O in basic media, the behavior of such deposition in acidic media remains largely unexplored. Our study provides insights into the formation of phase-pure n-type Cu2O and obviates the occurrence of the speculated second reaction, Cu2O corrosion. Phase-pure n-type Cu2O enables investigations into defect chemistry governing n-type behavior without metallic Cu complications. It serves as an electron transport layer in photo-conversion devices and allows for homojunction devices with p-type Cu2O. Figure 1

Characterization of Cu and SiCn Surface for Hybrid Bonding

The miniaturization of integrated circuits (ICs) comes with many challenges caused by R&D costs, physical constraints, and connectivity bottlenecks. Consequently, 3D integration and chiplet have gained a lot of interest as an alternative technique to address such problems. It is expected to offer reduced wire lengths for interconnects, low power consumption, and heterogeneous integration capabilities, among other benefits [1]. 3D integration and chiplets require high-density, and fine-pitch interconnects, which make the conventional solder bumps, commonly used as a bonding technique, face reliability issues. Thus, Cu–Cu direct bonding has emerged as a promising bonding method [1-3]. Compared to conventional solder base interconnects, direct Cu-Cu bonding offers the advantages of significantly lower electrical resistivity, ultra fine-pitch (high density), and lower electromigration. Direct bonding interconnection (DBI) is one of the technologies used for hybrid bonding, which combines a dielectric bond with a Cu-Cu bond (metal bond).The Cu pads, for hybrid bonding, are created by the electrochemical deposition (ECD) method. After the Cu deposition, reducing the roughness and cleaning the Cu surface prior to the bonding process is necessary to achieve high yield and reliability [4]. Therefore, surface planarization is a key factor for Cu-Cu hybrid bonding, and chemical mechanical polishing (CMP) using a chemical slurry can flatten and decrease the roughness of Cu surfaces [2]. However, CMP slurries contain chemical species, such as oxidizers, chelating agents, corrosion inhibitors, surfactants, and pH adjustors that need to be removed by applying a post-CMP (P-CMP) process [5]. For instance, if BTA (common corrosion inhibitor) remains on the Cu surface after the P-CMP process, it might inhibit Cu interdiffusion during hybrid bonding, which may require a high post-bond annealing temperature [6]. P-CMP process has shown that it can remove the contaminants through the cleaning process, plasma activation, and DIW rinsing before hybrid bonding [6].This work aimed to evaluate pre and post-CMP surfaces for Cu-SiCN hybrid bonding. Alkaline and Acidic cleaning agents were investigated. Fig 1(a) and (b) show the Open Circuit Potential (OCP) data of the Cu surface when an acidic and an alkaline solution was used as a cleaning agent, respectively. In the alkaline solution, Post-CMP Cu and Oxidized Cu samples showed a decreased response over time until they achieved a steady state, progressing to the Pure Cu values. It suggests that the Pure Cu surface did not show CuO film growth, hence, demonstrating a better cleaning potential than the acidic solution. Cu surface before and after the cleaning process was analyzed by X-ray photoelectron spectroscopy (XPS). The organic residue, BTA, could be removed from the surface after the cleaning process by PVA brush using the alkaline solution, though there were remaining residues after cleaning with the acidic solution. The effect of plasma activation was analyzed in order to reduce the removal of Cu residues, as well. On top of the above mentioned, we will analyze the different Cu types for corrosion inhibition. Figure 1

One‐step polymerization of polyvinyl alcohol/cashew gum/polypyrrole/copper oxide nanocomposites for high‐performance flexible films in optoelectronics

AbstractA ternary blend nanocomposite composed of polyvinyl alcohol/cashew gum/polypyrrole (PVA/CG/PPy) with varying contents of copper oxide (CuO) nanoparticles was synthesized via an in situ polymerization method, using water as an eco‐friendly solvent. Fourier‐transform infrared spectroscopy (FTIR), UV–visible spectroscopy, field emission scanning electron microscopy (FE‐SEM), x‐ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) were used to characterize the ternary blend nanocomposites. FTIR and UV–visible spectra demonstrated strong intermolecular interactions between the functional groups of the PVA/CG/PPy blend and the CuO nanoparticles. XRD patterns revealed that the CuO nanofillers were arranged in a structured manner within the ternary blend matrix. FE‐SEM confirmed the uniform dispersion and structured arrangement of CuO nanofillers at a concentration of 3 wt% within the blend matrix. TGA and DSC results showed that the addition of CuO nanoparticles to the PVA/CG/PPy blend improved both the thermal stability and glass transition temperature of the blend matrix. Electrical properties improved with CuO content up to 3 wt%, resulting in enhanced conductivity, an increased dielectric constant, and reduced activation energy. The highest tensile strength, 13.76 MPa, was also observed at this concentration. However, properties declined beyond 3 wt% due to agglomeration, making 3 wt% the ideal concentration for maximum performance. This study highlights the potential of PVA/CG/PPy/CuO nanocomposites for applications requiring improved electrical properties and thermal stability, particularly in flexible electronics and energy storage devices.Highlights Eco‐friendly synthesis of PVA/CG/PPy/CuO biopolymer nanocomposite films Improvement in morphological, and optical properties of PVA/CG/PPy/CuO films. CuO nanofillers magnify the thermal properties of the pristine PVA/CG/PPy Conductivity and dielectric characteristics: frequency and temperature dependence explored. PVA/CG/PPy/CuO nanocomposite films: pliable contenders unveiling industrial potentials.

Study of the Photovoltaic Parameters of Inorganic Solar Cells Based on Cu<i>2</i>O and CuO

A theoretical study of the photovoltaic parameters of inorganic solar cells based on ZnO/Cu2O and ZnO/CuO heterojunctions was carried out to improve the energy conversion efficiency. The influence of the thickness, charge carrier concentration and band gap of Cu2O and CuO films, as well as ZnO, on the photovoltaic parameters of solar cells has been studied. The simulation results showed that the efficiency of solar cells is significantly affected by the contact potential difference, the diffusion length of minority charge carriers, the amount of generated photocurrent and the recombination rate. The maximum efficiency of a solar cell based on ZnO/Cu2O was obtained equal to 10,63%, which is achieved with a band gap, thickness and charge carrier concentration in Cu2O equal to 1.9 eV, 5 μm and 1015 cm–3 and band gap, thickness and the concentration of charge carriers in ZnO is equal to 3,4 eV, 20 nm and 1019 cm–3, as well as the displacement of the edges of the conduction bands is 0.8 eV. For a solar cell based on ZnO/CuO, a maximum efficiency of 18.27% was obtained with a band gap, thickness and charge carrier concentration in CuO equal to 1.4 eV, 3 μm and 1017 cm–3, as well as a displacement of the conduction band edges of 0.03 eV. The obtained results of modeling solar cells can be used in the design and manufacture of inexpensive and efficient photovoltaic structures.

Enhancing the photo-response of CuO thin film based infrared light photodetector via fabricating ZnO-capped CuO device

In this study, we investigate the influence of ZnO capping on CuO films deposited by spray pyrolysis and its subsequent impact on the photo-response of Ag/CuO/Ag photodetector. Our findings demonstrate that ZnO capping significantly affects the electrical properties of CuO film. This is manifested as a substantial decrease in dark-current (from 12.06 μA to 0.49 μA), a pronounced increase in photo-current (from 28 μA to 665 μA), and a rapid photo-response time of 3.2 ms. These enhanced electrical characteristics translate to superior photodetector performance, as evidenced by increased responsivity (0.9 A/W), detectivity (5 × 1011 Jones), sensitivity (2.4 × 104 %), and external quantum efficiency (132 %) compared to the bare CuO device (0.11 A/W, 1.3 × 1010 Jones, 132 %, and 17 %, respectively). These results highlight the promising potential of ZnO-capped CuO films for application in high-performance infrared photodetectors.

Impact of bath temperature on the optical, structural, and photoelectrochemical properties of thin films of copper (II) oxide synthesized via electrodeposition method

This study investigates how bath temperature influences the properties of CuO thin films grown on FTO substrates using the electrochemical deposition method. CuO films were fabricated at bath temperatures ranging from 40 °C to 80 °C under a constant voltage of 0.5 V, using a bath solution containing copper sulphate, tartaric acid, and sodium hydroxide to maintain pH. CuO films were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, UV-Vis spectroscopy, photoluminescence (PL) spectroscopy, photocurrent measurements, Mott-Schottky (MS) measurements, and electrochemical impedance spectroscopy (EIS). XRD analysis definitively verifies the presence of a monoclinic structure in the CuO films, exhibiting a dominant orientation along the (200) plane. Raman analysis identified shifts in characteristic CuO vibrational modes at 270 cm⁻1, 317 cm⁻1, and 605 cm⁻1, reflecting changes in crystallographic structure. SEM revealed that particle size varied significantly with bath deposition temperature increased. UV-Vis spectra showed a systematic decrease in the optical bandgap from 1.67 eV to 1.39 eV with increasing temperature, attributed to improved crystallinity and reduced defect states. PL spectra of CuO thin films indicated two distinct photoluminescence maxima at about 465 nm and 517 nm with difference in the intensity for all samples due to changes in defect density and crystallinity. Photocurrent measurements and Mott-Schottky analyses demonstrated that the CuO films behave as p-type semiconductor, and with increasing the bath temperature the acceptor carrier increased. EIS analyses demonstrated improvements in electrochemical properties, with the flat band potential and charge transfer resistance showing significant temperature dependence. The results indicate that deposition temperature critically affects the structural, optical, and electrochemical performance of CuO thin films, providing insights for optimizing their application in optoelectronic devices and energy systems.

Influence of substrate temperature and Mn/Y co-doping concentration on the morphological, structural and optical properties of CuO nanostructured film deposited by the spray pyrolysis method

In this work, the effect of substrate temperature (ST) during deposition and dopant amount of Mn (1,3,5, and 7 %) and Y(3 %), (Mn/Y), on the physical properties of copper oxide (CuO) the nanostructured film were analyzed using different diagnostic tools. The pure and (Mn, Y) co-doped CuO thin films were deposited by the spray pyrolysis method, which is effective and easy to apply for any substrate. Deposited pure and (Mn,Y) co-doped CuO nanostructured films were investigated by X-ray diffraction (XRD), UV–Vis spectroscopy, and Field emission scanning electron microscopy (FESEM) techniques to analyze the influence of ST and co-doping on the structural, morphological, and optical properties of prepared films. The FESEM is used to visualize nanostructures on the surface of the film. Also, it is observed that the surface morphology of CuO film changes from a spherical-like to a nanocloumnar-like structure with increasing substrate temperature. The XRD diffractograms confirm the monoclinic crystal structure of CuO, in polycrystalline nature for all deposited films. UV–Vis spectra suggest changing the optical absorbance and the band gap of the pure and Mn/Y co-doped CuO nanostructured films. In the first investigation of this study, the better substrate temperature was obtained as 400 °C according to results. In the second part, the effect of Y and Mn doping with different content was analyzed for the CuO film deposited at the chosen ST of 400 °C. There is no observable crystalline structure variation in the XRD pattern, but the size of nanostructure and dislocation density are varied with Mn/Y co-doping. FESEM micrographs confirm the impact of the co-doping concentration on the size, shape, and surface properties of CuO nanostructured film. In addition, the optical band gap increases with Mn doping up to 3 % of Mn content and it was determined as 2.69 eV for the sample 3Mn/Y@CuO nanostructured film. The obtained results suggest that the substrate temperature has an important impact on the physical properties of the spray deposited CuO nanostructured film, and the structural, optical, and surface properties of the CuO nanostructured films may be engineered by Mn/Y doping concentration.

Semitransparent Cu2O Films Based on CuO Back Layer for Photoelectrochemical Water Splitting and Photovoltaic Applications.

Cuprous oxide (Cu2O) as an intrinsic p-type semiconductor is promising for solar energy conversion. The major challenge in fabricating Cu2O lies in achieving both high transparency and high performance in a tandem device. The Cu2O photocathodes often employ gold as the back contact layer. However, it is not an optimal choice in tandem device due to its poor transmission, scarcity, and electron-hole recombination at the interface of Au and Cu2O. Here, we presented a facile method that utilizes the earth-abundant material copper oxide (CuO) to fabricate highly transparent Cu2O devices. The maximum transmittance of the Cu2O film on CuO (FTO/CuO/Cu2O) increased from 42 % to 58 % compared with Cu2O film on Au (FTO/Au (3 nm)/Cu2O) in 550-800 nm. After coating atomic layer deposition (ALD) layers and hydrogen evolution reaction (HER) catalyst, the photocurrent density at 0 V (versus RHE) of the semitransparent Cu2O photocathode with CuO as the back layer for photoelectrochemical (PEC) water splitting reached -4.9 mA cm-2, which showed a 24.5 % improvement compared with FTO/Au/Cu2O photocathode. Moreover, expanding the CuO layer strategy to the field of solar cells enables Cu2O solar cells to achieve a PCE of 2.37 %.

Construction and photothermal properties of Ag nanoparticles modified multilevel porous CuO film with ultra-wide infrared spectrum absorption

Based on lattice vibration and energy band theory, narrow bandgap inorganic semiconductor materials have become a new type of photothermal material, but it is difficult to achieve absorption for long wavelength infrared radiation to meet the application requirements of ultra-wide spectrum (2.5–20 μm) infrared detectors. From the perspective of structural optics, this paper constructed a multilevel porous CuO film with both coral-like micro-porous and flower-like nano-porous structures based on chemical bath deposition technique, and the Ag nanoparticles were uniformly embedded in the "petal" gaps of flower-like nano-porous CuO by optimizing the dosages of PVP. Benefiting from the synergistic effect of multilevel porous structure and loaded Ag nanoparticles, the Ag nanoparticles modified multilevel porous CuO (CuO@Ag-PVP 0.05) film had an average absorption of 94.17 % over the wavelength range of 2.5–20 μm. The photothermal conversion efficiency of CuO@Ag-PVP 0.05 film can reach up to 81.12 % and 86.96 % over near-infrared and far-infrared light ranges, respectively. The various material characterizations and simulations analysis showed that the multilevel porous structure containing coral-like and flower-like multi-scale pores can form two guiding modes for light, and based on the synergistic effect of the two guiding modes, the CuO film can form a strong trapping effect for light over ultra-wide spectral range, broaden its absorption range, and enhance its absorption characteristics. The loaded Ag nanoparticles contain a large number of free electrons, which can capture light energy and convert it into heat energy through local surface plasmon resonance (LSPR) effect, further enhancing the light absorption and photothermal conversion efficiency.

Synthesis and characterization of ZnO and CuO coatings for antibacterial and antiviral applications

Copper oxide (CuO) and Zinc oxide (ZnO), coating have attracted attention for their potential antiviral properties, including their ability to combat virus. This study focuses on the development and characterization of self-disinfecting surface passivation films composed of CuO and ZnO, obtained using the spin-coating technique. The research aims to develop surfaces that can actively eliminate harmful microorganisms, reducing the risk of infections, while also offering strong mechanical resistance and adhesion to withstand external factors, which is crucial for ensuring long-term effectiveness. Additionally, the microstructural properties of the elaborated films were analyzed using SEM/EDS, which stands for Scanning Electron Microscopy/Energy Dispersive X-ray Spectroscopy and X-Ray diffraction analysis (XRD). The mechanical behavior was assessed through Vickers hardness and scratch resistance tests. It was found a dense and homogeneous thin films. The hardness of CuO and ZnO films were 11.14 ± 0.04 GPa, and 8.89 ± 0.04 GPa respectively. Therefore, scratching tests revealed high adhesion properties with a critical load LC1 of 1.89 ± 0.02 N and 1.04 ± 0.02 N for CuO and ZnO films respectively. Then, this study revealed that CuO and ZnO films exhibit excellent antimicrobial activity against Staphylococcus aureus ATCC 29213, as well as outstanding antiviral activity against the HSV-2 virus.

Nitrogen doping of cuprous oxide films: A surface science perspective

Nitrogen doping of Cu2O films grown on Au(111) and Pt(111) supports was explored by a variety of surface-science techniques, including electron-diffraction, X-ray photoelectron-spectroscopy (XPS), scanning tunneling microscopy and photoluminescence spectroscopy (PL). The films were prepared by Cu vapor deposition and high-pressure oxidation at 50 mbar O2. Nitrogen was inserted by adding N2 to the reactive gas or via sputter doping. Only the latter resulted in a clear N1s signal in XPS, compatible with the insertion of N-atoms at O substitutional sites. The N-doping caused an overall degradation of the oxide lattice and suppressed the formation of the (√3×√3)R30° surface reconstruction observed on pristine Cu2O(111). Moreover, the oxide Fermi level shifted from the valence-band top into the band gap, indicative for a reduced p-type conductivity of the sample upon doping. The N-dopants featured low thermal stability and largely desorbed at around 500 K, leaving behind a pronounced 850 nm PL peak due to O vacancy emission. Our findings indicate that the N-atoms initially occupy O substitutional sites but get removed easily at moderate temperature, casting doubts whether N-doping is a suitable pathway to improve the conductance and luminescence behavior of Cu2O.

Effects of cadmium doping on the physical and sensing properties of nanostructured CuO thin films

This investigation used sol-gel deposition to create undoped CuO and CuO: Cd thin films. All films of undoped CuO and CuO: Cd phase exhibit four dominating peaks at 35.52°, 38.84°, 53.37°, and 68.23°, which are correspondingly assigned to the (022), (200), (020), and (220) planes, according to X-ray diffraction analysis. The dislocation density reduced from 60.55 to 49.94, the strain decreased from 26.98 to 24.60, and the grain size of the produced films measured by XRD was 12.85–14.15 nm. Atomic force microscopy (AFM) was used to study the morphology. SEM analysis showed increased aggregation with higher Cd content, resulting in a more uniform porous structure. The optical band gap decreases for all samples as the cadmium content increases, ranging from 2.28 to 2.14 eV. Similarly, the refractive index and extinction coefficient values decrease as the cadmium content increases for all samples. The gas sensor detects H2 (375 ppm) using CuO film cadmium doping, which enhances sensitivity, CuO: 4% exhibits highest resistance. Sensitivity decreases with higher doping, indicating reduced sensor responsiveness.

The surface chemistry of cuprous oxide

The chemical and electronic properties of copper combined with its large natural abundance lend this material to impact a wide range of technological applications, including heterogeneous catalysis. The reactivity of copper in its Cu1+oxidation state makes this specific configuration relevant in various chemical reactions, but the facile redox properties of copper make the isolation of individual states for fundamental studies difficult. Here we review three Cu2O model systems used to study the interaction of Cu1+ with small molecules making use of surface science techniques: Cu2O/Cu(111), thin polycrystalline Cu2O films on Cu foil, and bulk Cu2O crystals. Advantages and disadvantages of each system are discussed and exemplified through case studies of chemical adsorption and reactivity studies.

An in-depth Analysis of the Physical Characteristics of TiO2–CuO Films Fabricated via Spray Pyrolysis

An in-depth Analysis of the Physical Characteristics of TiO2–CuO Films Fabricated via Spray Pyrolysis