Properties Of CuO Thin Films Research Articles

Effects of Rapid Heat Treatments on the Properties of Cu2O Thin Films Deposited at Room Temperature Using an Ammonia-Free SILAR Technique

We report herein the analysis of the properties of copper(I) oxide thin films deposited by an optimized ammonium-free successive ion layer adsorption and reaction (SILAR) technique. The Cu2O thin film deposition process was carried out at room temperature using copper acetate monohydrate, sodium citrate as complexing agent, and hydrogen peroxide as precursors of copper and oxygen ions, respectively. The harmless and easy-to-handle sodium citrate replaces the volatile NH4OH commonly employed as complexing agent in the SILAR technique for the deposition of metal oxide thin films. The optical, structural, morphological, and electrical properties of the as-deposited Cu2O thin films were studied as a function of the number of cycles during deposition, as well as their modifications produced by the effect of rapid thermal annealing (RTA) in vacuum in a temperature range of 200–250°C for 1 min, 3 min, and 5 min. The as-deposited thin films had cubic crystalline structure corresponding to the Cu2O phase as determined by x-ray diffraction (XRD), with a direct energy bandgap of 2.43–2.51 eV depending on the number of cycles, and electrical resistivity of the order of 103 Ω cm. The XRD and x-ray photoelectron spectroscopy (XPS) analysis of the Cu2O thin films treated by RTA demonstrated an increase of the crystal size with time and temperature of the RTA and reduction effects from Cu2+ to Cu1+ oxidation states. On the other hand, the RTA treatments also decreased their energy bandgap to 2.38 eV and electrical resistivity to 102 Ω cm. The high energy bandgap values of the Cu2O thin films were attributed to quantum confinement effects produced by their small crystal size in the range of 3.6–8.6 nm.Graphical

The outcomes of Zn doping on the properties of CuO thin films prepared via modified SILAR method and its impact on the performance of CuO-based solar cells using Cd0.4Zn0.6S-ETL and Spiro-OMeTAD-HTL

The outcomes of Zn doping on the properties of CuO thin films prepared via modified SILAR method and its impact on the performance of CuO-based solar cells using Cd0.4Zn0.6S-ETL and Spiro-OMeTAD-HTL

Effect of repeating hydrothermal growth processes and rapid thermal annealing on CuO thin film properties.

This paper presents an investigation into the influence of repeating cycles of hydrothermal growth processes and rapid thermal annealing (HT+RTA) on the properties of CuO thin films. An innovative hydrothermal method ensures homogeneous single-phase films initially. However, their electrical instability and susceptibility to cracking under the influence of temperature have posed a challenge to their utilization in electronic devices. To address this limitation, the HT+RTA procedure has been developed, which effectively eliminated the issue. Comprehensive surface analysis confirmed the procedure's ability to yield continuous films in which the content of organic compounds responsible for the formation of cracks significantly decreases. Structural analysis underscored the achieved improvements in the crystalline quality of the films. The implementation of the HT+RTA procedure significantly enhances the potential of CuO films for electronic applications. Key findings from Kelvin probe force microscopy analysis demonstrate the possibility of modulating the work function of the material. In addition, scanning capacitance microscopy measurements provided information on the changes in the local carrier concentration with each repetition. These studies indicate the increased usefulness of CuO thin films obtained from the HT+RTA procedure, which expands the possibilities of their applications in electronic devices.

Effects of Postdeposition Annealing on the Electrical Properties of Cu2O/4H–SiC PiN Diodes

Copper oxide (Cu2O) is a promising p‐type material owing to its high absorption coefficient, suitable bandgap width, chemical stability, nontoxicity, and abundance. In this study, the effect of postdeposition annealing (PDA) on the electrical properties of Cu2O thin films deposited on silicon carbide (SiC) substrates is investigated. The films are subjected to PDA using radio‐frequency sputtering at various temperatures in air. During PDA, the Cu2O films are maintained at <300 °C and transitioned to cupric oxide (CuO) at 400 °C. The as‐deposited Cu2O film exhibits a low oxidation peak (Cu2+), whereas the phase‐transformed CuO films exhibit a higher binding energy with the emergence of satellite peaks. The rectification ratios of the Cu2O device annealed at 300 °C and CuO device annealed at 400 °C are determined as 2.02 × 107 and 1.01 × 105, respectively, denoting the substantial enhancement of approximately 55.04 for the Cu2O/SiC device and degradation of approximately 0.28 for the CuO/SiC device relative to their non‐annealed counterparts. Therefore, in this study, the significant improvement in the performance of Cu2O thin films with the meticulous deposition control of potential p‐type materials, such as Cu2O and CuO, for high‐throughput and low‐cost electronic applications is demonstrated.

Effect of Li Doping on Structural, Optical, and Electrical Properties of CuO Thin Films Produced by Spray Pyrolysis Method

Effect of Li Doping on Structural, Optical, and Electrical Properties of CuO Thin Films Produced by Spray Pyrolysis Method

Effect of Hydrothermal Reaction Temperature on the Structural and Optical Properties of CuO Thin Films

Copper oxides are one of the first semiconductors studied for device applications. In the present work, CuO thin films were deposited on fluorine-doped tin oxide (FTO) substrates via hydrothermal method without using any surfactant and the effects of reaction temperature on the properties of the films were studied. CuO thin films deposited at different reaction temperatures were characterized for their structural and optical properties using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), Raman spectroscopy, and optical absorption measurements. XRD results revealed that all the films consisted of polycrystalline CuO with a monoclinic crystal structure without any impurity phase. SEM images showed that chrysanthemum-like structures were formed, the number of which increased with increasing hydrothermal reaction temperature. EDAX measurements proved the existence of Cu and O elements and showed that all the films have Cu/O ratios close to unity. The Raman spectra confirmed the formation of crystalline CuO in all the films. From the optical absorption measurements, the direct forbidden energy gap values of the CuO thin films were found to be between 1.34 eV and 1.41 eV, depending on the hydrothermal reaction temperature.

Influence of pH value of precursor on growth, structural, and optical properties of Cu2O thin films grown in Mist-CVD

The Cu2O thin films were prepared from copper (II) acetylacetonate (Cu(acac)2) by the mist chemical vapor deposition (mist-CVD) method, depending on the pH value of the prepared solution. It was confirmed that the well-oriented Cu2O thin films were grown at a dominant (111) peak according to X-ray diffraction (XRD) measurement using an alkaline precursor solution. The pH of the prepared solution drastically affected the surface morphology of the Cu2O thin films, and the lowest Root Means Square (RMS) was found for pH-10 of the precursor solution. The confocal Raman spectrum confirmed the formation of the cubic Cu2O crystal structures for each pH value of the precursor solution. The very transparent Cu2O thin films that were grown. The highest transmittance, 70%, was obtained at 1100 nm from the absorption spectrum for Sample B. The optical energy band gaps of Cu2O thin films were determined using Tauc's method and found to vary within a range of 2.53 to 2.49 eV, indicating a change in the material's electronic structure. The study demonstrated the crucial role of the pH level of the prepared solution in the growth of the Cu2O thin film. Specifically, it was found that a higher pH level resulted in a greater concentration of hydroxide ions (OH−), which was a crucial factor in the growth process. These findings can be significant in using p-type Cu2O thin films prepared based on mist-CVD for optoelectronic applications.

Transition of Cu film to Cu2O film through oxygen plasma treatment

Metal–oxide-semiconductor-based thin-film transistors have attracted increasing research attention owing to their wide bandgap and minimal leakage current. However, the prevalent n-type behavior of several oxide semiconductors prompted the exploration of p-type alternatives. Among these, Cu films are promising candidates for different fields. In this study, the effectiveness of oxygen plasma treatment for the transition of Cu films to their p-type oxide semiconductor phase, i.e., Cu2O, was demonstrated with a focus on low-temperature fabrication for future integration in flexible devices. We reported the adjustability of the oxidation depth of a Cu thin film and the effect of oxidation dynamics by controlling the bottom radio frequency power of a high-density plasma system. This novel approach enabled metal-to-semiconductor transitions and modulation of the physical properties of Cu2O thin films by inducing changes in their composition and microstrain. The oxidation dynamics, oxidation depth, crystallinity, and film surface were analyzed. Moreover, the changes in the optical bandgap were determined, with the transition of the Cu (111) phase to the Cu2O (111) phase confirmed as a function of the process time. As oxidation progressed, particles formed on the surface of the Cu2O thin film and the particle size increased. Further, the oxidized Cu thin film was determined to be Cu2O rather than CuO. Therefore, oxygen plasma treatment is expected to be a new approach to low-temperature oxidation.

Influence of different temperatures and pH on structural, morphological, and electrochemical properties of Cu2O thin films by electrodeposition in acidic media

The present work describes the effect of deposition temperatures and pH values on structural, morphological, and electrochemical properties of cuprous oxide (Cu2O) thin films deposited on the conductive SnO2 glass substrates by using electrodeposition technique in an acidic system. The chronoamperometry curve of the solution was tested on an electrochemical workstation. X-ray diffraction patterns indicate that the deposited films have better crystallinity which is deposited at the deposition temperature of 50 °C and pH value of 5–6. Scanning electron microscopy displays that surface morphology of the deposited films varied greatly with the deposition temperature and pH value rising. The results of quantitative study of the target product films by Energy Dispersive Spectrometer (EDS) show that they are all in line with the element content ratio of Cu2O. By measuring the resistivity and conductivity of the deposited films, it was found to be in the semiconductor range.

Probing intrinsic defects of aluminium-doped CuO thin films for solar cell applications.

Intrinsic defects in semiconductor thin films play a significant role in determining their optoelectronic properties. In this work, we investigated the impact of aluminium doping on the intrinsic defects and, thereby, the optoelectronic properties of CuO thin films deposited via spray pyrolysis. Doping considerably influenced the inherent defects of CuO thin films. Al3+ doping enhanced oxygen interstitial defects and suppressed oxygen vacancy defects. The presence of oxygen interstitials and an improvement in the crystallinity of the films resulted in favourable changes in the properties of the films. The observed modifications in the properties had a profound significance in improving the performance of CuO-based optoelectronic devices such as solar cells. Further, the ease of formation of oxygen interstitial defects compared to other possible defects and their favourable role in enhancing optoelectronic properties were confirmed through theoretical calculations. Thus, via comprehensive experimental and theoretical investigation, this study provides significant insights into the formation of defects and their influence on the properties of Al-doped CuO films.

The Effect of Transient Power Ramp‐Up on Structural and Optical Properties of CuO Thin Films Prepared by Radio Frequency Magnetron Sputtering

Transition metal oxides have found application as charge transport materials (CTMs) in perovskite solar cell devices due to their better environmental stability and superior electronic properties compared to organic CTMs. Many researchers have used radio frequency (RF) magnetron sputtering to deposit inorganic CTMs on inorganic layers. However, such efforts on perovskites have been limited by the distortion of high‐energy ions of the sputtering gas energized by the RF power and temperature. The ions may also distort the interface between transparent conducting oxides and the charge transport layers, thereby increasing optical scattering. Thus, the effect of ramp power during RF magnetron sputtering deposition on the structural and optical properties of copper oxide thin films is investigated. While the optical transmittance of the films decreases with increased RF power, it remains the same for all ramped power films; however, it has a similar profile as the highest RF power film. As the ramp power increases, the X‐ray diffraction shows that the films become more polycrystalline with a monoclinic crystal structure. The energy‐dispersive X‐ray spectroscopy results reveal that the atomic concentration of copper slightly increases with the RF power, whereas oxygen concentration slightly decreases.

Comparative structure, optical and electrical characteristics of sol-gel-deposited In-, Ga-, and Sn-doped CuO thin films

Doping of metal-oxide thin films provides an effective method to improve the performance of various devices based on them such as solar cells, photodetectors, and gas sensors. Developing high-performance of these devices, the influence of In, Ga, and Sn dopants on structure, optical and electrical characteristics of CuO deserves further study. Herein, undoped and In-, Ga-, and Sn-doped CuO thin films are deposited on glass substrates by the sol-gel method, and the parameters influenced by these dopants are determined systematically. The effect of studied dopants on XRD, SEM, UV-vis, PL, and electrical conductivity measurements are examined, and the results are correlated with each other. Additionally, the electrical transport mechanism of the films is comprehensively investigated. It is determined that the multi-phonon hopping (MPH) conduction mechanism governs the temperature-dependent conductivity of the films. Finally, it is found that the probed dopants significantly impact the properties of CuO thin film.

Performances of Nano-Structured Cu2O Thin Films Electrochemically Deposited on ITO Substrates in Lactate Bath as Liquid Petroleum Gas Sensors

The investigations are focused on structural and surface morphological features and their influence on electrical and wetting characteristics against liquid petroleum gas (LPG) sensing of synthesized nanostructured cuprous oxide (Cu2O) thin films grown by electrochemical deposition (ECD) on indium tin oxide (ITO) glass substrates in lactate bath (pH 10). p-Cu2O films revealed a cubical-tetrahedron nano-scale polycrystalline grain distribution (average grain size: 64.2 nm, inter planer spacing: 0.24 nm) that exhibited dominance in the crystallographic plane (111). LPG sensing evaluations of p-Cu2O/ITO done at 70 °C constant temperature with 100% LPG at 5 cc min−1 flow rate, showed excellent gas sensor response, recovery, and stability over time due to its moderate wetting behavior (average contact angle: ∼86°). AC impedance measurements carried out at room temperature demonstrated an ionic to electronic conduction variation from 100 Hz to 1 MHz, due to adsorption/desorption of LPG molecules (CnH2n+2) and oxygen species on the nano-particles surface. Cu2O/ITO flat band potential was found to be higher than its’ ambient state after exposure to LPG with an increment in acceptor density. Overall, this efficient LPG sensing could be attributed to the interfacial properties of Cu2O thin films and ITO substrates, that provide an optimized fabrication process of nano-structured Cu2O thin films.

Harnessing the tunability of intrinsic defects in isovalent Zn doped spray deposited CuO thin films

Doping is a versatile tool for tailoring the properties of semiconductor thin films. This article investigates the influence of isovalent dopant, Zinc (Zn), on the electronic, optical and structural characteristics of copper oxide (CuO) thin films prepared by spray pyrolysis technique. Structural characterization from XRD and Raman studies confirms the successful incorporation of Zn atoms into the CuO lattice without altering monoclinic structure of the films. The absence of secondary phases like Cu2O and ZnO confirms the good quality of the prepared films. A significant variation in the morphology of the films was observed in FESEM images. The EDS analysis confirmed the incorporation of Zn atoms in CuO films and showed that the prepared films are oxygen rich in nature. The band gap of the films increased from 1.50 eV in pristine samples to 1.62 eV in 8 at% Zn-doped sample. Different defect related emissions were observed in PL spectra with the resultant emission in yellowish green region as obtained from chromaticity diagram. XPS analysis confirmed that both Cu and Zn are found in +2 oxidation state. The electrical conductivity and carrier concentration of CuO films improved with doping due to the enhanced oxygen interstitial defects. The carrier density increased from 2.17 × 1014 to 2.82 × 1015 cm−3 after 6 at %doping with the lowest resistivity of 708 Ω cm. Hence, the properties of CuO films can be effectively modified by Zn doping. Zn doping improved the electrical properties of the films without trading off the excellent optical properties of CuO thin films making them suitable in solar cell absorber layer applications.

Defect-Induced Phase Transformations in CuO Thin Films by Ag Ion Implantation and Their Gas-Sensing Applications

The present study is aimed to modify the structural, optical, and morphological properties of CuO thin films with Ag ion implantation toward their potential applications. Fabrication of thin films of CuO was carried out using a thermal evaporation technique on silicon (Si) substrate; post implantation was done with 30 keV Ag ions with varying fluences from 1 × 1014 to 1 × 1016 ions/cm2. The pristine and implanted samples were characterized through X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM), and diffused reflectance spectroscopy (DRS). SRIM simulation was also carried out to understand the range and other effects. XRD measurements confirmed the formation of the CuO phase for pristine samples, and with the increase in ion fluence, the chemical composition changed from pure CuO to Cu2O + CuO and then to Cu2O + Cu at higher ion fluences. These experimental results from Raman spectroscopy were also consistent with the XRD analysis, which also showed the presence of mixed phases of CuO, Cu2O, and Cu. Results from AFM showed that the value of average roughness increased due to more defects. DRS results revealed the variation in band-gap energy for pristine and implanted samples from 1.96 to 1.71 eV. Density functional theory (DFT) simulations confirmed that Ag ion implantation causes the reduction of CuO surface into Cu2O and Cu. We found that Ag ion implantation-induced defects lead to the mixed phases of CuO, Cu2O, and Cu, which can help in the selective sensing of ethanol and acetone, demonstrating this as a useful technique and having potential applications in energy conversions, and gas and biomolecule sensing.

Effect of Ga doping on structural, morphological, optical and electrical properties of CuO thin films deposited by spray pyrolysis technique

Effect of Ga doping on structural, morphological, optical and electrical properties of CuO thin films deposited by spray pyrolysis technique

Effect of Substrate Temperature on Variations in the Structural and Optical Properties of Cu2O Thin Films Deposited via RF Magnetron Sputtering

In the present study, Cu2O films were deposited on a glass substrate via RF (radio frequency) magnetron sputtering under substrate temperature conditions that ranged from room temperature (RT, 25 °C) to 400 °C. The structural, compositional, and optical properties of the Cu2O films were analyzed in relation to the experimental variables by applying various measurement methods. The substrate temperature was a crucial factor in shaping the structural, compositional, and optical properties of the Cu2O films that were synthesized via RF-magnetron sputtering. Our findings revealed that the Cu2O films exhibited a cubic structure, which was confirmed by XRD analysis. Specifically, the (111) and (200) planes showed different trends with respect to the substrate temperature. The intensity of the (111) peak increased at 250 °C, and above 300 °C, the preferred orientation of the (111) plane was maintained. The grain size, which was determined via FE-SEM, displayed a positive correlation with the substrate temperature. Additionally, XPS analysis revealed that the binding energy (BE) of the Cu2O film sputtered at 400 °C was similar to that which was previously reported. Notably, the as-grown Cu2O film demonstrated the highest transmittance (15.9%) in the visible region, which decreased with increasing substrate temperature. Furthermore, the energy band gap (Eg) of the Cu2O films remained constant (2.51 eV) at low substrate temperatures (25 °C to 200 °C) but exhibited a slight increase at higher temperatures, reaching 2.57 eV at 400 °C.

Structural, optical and electrical properties of CuO thin films deposited by spray pyrolysis technique: influence annealing process

In this work, CuO thin films about the synthesis of the thin films are prepared on glass substrate using spray pyrolysis technique at room temperature different annealing times in temperature 450 0 C.In order to study the effect of annealing times onthe structural, optical and electrical properties.XRD analysis has shown that films with a polycrystalline structurehave a(Monoclinic) structure.In addition, the crystallite phase CuO increases with increasing of annealing temperature.Moreover, with a preferred orientation along (002) peak.The optical properties confirmed that the elaborated films have a transmittance of 70%. We have found that the band gap energy (Eg) is a decreasing function with respect to the annealing temperature time. In addition, the electrical resistivity varies from 18.97 to 4.58 KOhm.cm for the films grown at different annealing times.

Structural and photocatalytic properties of undoped and Zn-doped CuO thin films deposited by reactive magnetron sputtering

In this research, undoped and Zn-doped CuO thin films were successfully fabricated by the reactive magnetron sputtering method. The effect of Zn dopant concentration on the enhancement of photocatalytic behavior and structural properties of CuO thin films was investigated. To obtain the optimal conditions in terms of the highest efficiency and rate in the photocatalytic degradation of methylene blue (MB), CuO films were first deposited at different oxygen partial pressures (30 %, 40 %, and 50 %). Optimal conditions, i.e., a 70 % photodegradation efficiency with a rate of 0.279 h−1 were achieved in the undoped sample deposited at a partial pressure of 40 %. Then different Zn amounts were incorporated into the CuO lattice by controlling the RF power in the range of 10–40 W. As-prepared samples were analyzed using GIXRD, XPS, PL, EIS, and UV–vis spectroscopy. The GIXRD pattern of the Zn-doped sample showed the formation of CuO without altering its monoclinic structure. XPS spectra indicated the presence of Cu2+ and Zn2+ oxidation states, which means the successful substitution of Zn2+ at Cu2+ sites in the CuO lattice. Based on EIS results, increasing the Zn cation dopant up to 0.026 led to a decrease in the charge resistance transfer compared to the undoped CuO. By increasing the amount of Zn in the cationic ratio up to 0.02, PL peak intensity reached the lowest value. Accordingly, the MB degradation efficiency increased to above 80 % in this sample. Active species involved in the photocatalytic reactions were investigated via a scavenger test. The Zn-doped CuO film showed high MB degradation efficiency even after five cycles (77 %), which made it a potential candidate for wastewater purification.

Unravelling the role of nickel incorporation on the physical properties of CuO thin films deposited by spray pyrolysis and theoretical analysis of nanostructured ZnO/Ni:CuO-based heterojunction solar cells

Unravelling the role of nickel incorporation on the physical properties of CuO thin films deposited by spray pyrolysis and theoretical analysis of nanostructured ZnO/Ni:CuO-based heterojunction solar cells