Properties Of Nickel Oxide Thin Films Research Articles

Synthesis, characterization, and CO sensing properties of NiO thin film for commercial aircraft applications

Abstract The detection of combustion gases such as carbon monoxide (CO) and fuel leaks is a concern in regard to aeronautical safety and has led to the development of semiconductor sensors. The focus of this work is the detection of CO within commercial aircraft using a thin film of nickel oxide (NiO) as the sensing element. The NiO phase was synthesized using the sol-gel method using a modification of the procedures proposed by N. Talebian and B. Pejova. Microstructural characterization of the NiO thin film was performed using scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Optical analysis was carried out using diffuse reflectance (UV-VIS) spectroscopy. The results showed that the NiO thin film was homogeneous and composed of nodular nanoparticles with size between 10 and 15 nm and thickness of 75 nm. The band gap value was 3.3 eV, which is consistent with p-type semiconductors. The sensitivity of the devices was determined by means of the static environment method. The best operation temperature was 200°C for the device with 100-µm spacing between tracks, which gave a response time of 165 seconds and recovery time of 212 seconds according the results of a flow-through method. The device with this track spacing is ideal for CO detection at 50 ppm, at which the first symptoms of intoxication appear in humans inside commercial aircraft.

Ultra-fast switching of energy efficient electrochromic nickel oxide thin films for smart window applications

In today's modern world, energy consumption continues to escalate. In such cases, smart windows play a crucial role in reducing energy consumption and enhancing the quality of life. Electrochromic devices (ECDs) -based smart windows rely profoundly on nickel oxide (NiO) thin films, which act as a counter electrode in ECDs. This work aims to fabricate NiO thin films, with the intention of achieving ultrafast ECD. Through the sputtering technique, energy-efficient ECD is obtained with the highest optical modulation of 60 % at a rapid switching speed of 0.55s for bleaching and 0.95s for coloration. We have also investigated the structural, morphological, vibrational, and optical properties of NiO thin films. XRD analysis revealed the less crystalline or near amorphous nature of NiO thin film. XPS, PL, and Raman studies confirm the existence of defects in the film. The favourable, less crystalline nature, along with the presence of defects, facilitates ultra-fast ion intercalation and de-intercalation process. We believe that prepared NiO film can be used as a promising anodic colourant in electrochromic smart windows with applications in energy-efficient buildings.

Optical properties of NiO films: Effect of nitrogen-doping, substrate temperature and band gap estimation using machine learning

In this study, nickel oxide (NiO) thin films were synthesized on glass substrates using RF magnetron sputtering with varying nitrogen (N) doping ratio and substrate temperatures to explore modifications in their structural, morphological, and optical properties. The films were prepared using a high-purity NiO target under controlled sputtering conditions. Structural analysis by X-ray diffraction revealed an improvement in crystallinity in the (200) direction with increasing N ratio. In contrast, higher N ratio led to the suppression of (111) and (220) peaks, indicating a significant influence of N on the crystal structure and orientation. The films’ thickness and morphology, examined using scanning electron microscopy and energy-dispersive X-ray spectroscopy, showed uniform and homogeneous growth with smooth surface topologies. Optical properties, assessed by UV–Vis-NIR spectrophotometry, demonstrated a decrease in transmittance and a redshift in the absorption edge with increased N doping, corresponding to a narrowing of the energy bandgap from 3.7 eV to 3.45 eV. This bandgap reduction is attributed to N incorporation substituting oxygen sites, introducing defect states within the band structure. Additionally, the impact of substrate temperature on film growth enhanced crystallinity and orientation along the (111) plane at higher temperatures, with a simultaneous reduction in film thickness due to increased adatom mobility and potential thermal decomposition. The evaluation of Kernel Ridge Regression (KRR) and Ridge Regression (RR) models revealed their effectiveness in predicting band gap values for thin films at varying substrate temperatures and thicknesses. While RR excelled in predicting a band gap of 3.6 eV for a film with a substrate temperature of 24 °C and a thickness of 112.7 nm, KRR outperformed in predicting a band gap of 3.65 eV for a film with a substrate temperature of 24 °C and a thickness of 107 nm. These findings elucidate the dual influence of N doping and substrate temperature on enhancing the functional properties of NiO thin films, promising for applications in optoelectronic devices and gas sensors.

Altering the physical properties of NiO thin films grown through the ultrasonic spray pyrolysis method by incorporating impurity lead dopants

The technology of p-type transparent semiconductors is utilized in various fields, and enhancing their performance holds industrial significance. Thus, improving the versatility and efficiency of the p-type transparent conducting oxides (TCO) has become critical for the semiconductor industries and technologies. To be used as hole carrier layes in optoelectronic devices, this study aimed to modify the physical features of nickel oxide (NiO) through a doping approach which may broaden and strengthen the usage of NiO. A cost-effective ultrasonic pyrolysis spray technique was employed for pure and lead (Pb) doped nickel oxide thin film production. The influence of the lead concentration on optical, structural, and morphological traits of the NiO nanostructures was examined via various analyses, including energy-dispersive X-ray spectroscopy (EDAX), scanning electron microscopy (SEM), Photoluminescence, UV–visible spectroscopy, X-Ray Diffraction, and Raman spectroscopy, were utilized to investigate the optical and structural characteristics of these films. In correlation, the X-Ray Diffraction results indicated that the Pb doping induced strain and altered lattice parameters of the grown nanostructures while the cubic phase of NiO maintained. The crystallite size of NiO samples ranged from 31.49 nm to 18.75 nm based on Pb doping concentration which was notably influenced by species and doping content. The UV–vis measurements demonstrated that optical parameters, such as optical band gap, were sensitive to Pb doping ratios. The Raman spectrum analysis confirmed the successful incorporation of Pb ions into NiO. Additionally, the intensity of the PL spectra decreased with increasing Pb content, offering potential applications as window layers in solar cells, smart windows, and other optoelectronic devices.

Low resistivity and transparent Co-doped NiO thin films synthesized by the sol-gel method: Structural, morphology and photoluminescence studied for optoelectronic applications

Thin films of undoped nickel oxide (NiO) and cobalt-doped nickel oxide (NiO:Co) with different concentrations 1, 3 and 5 at.%, were deposited on glass substrates using the combined sol-gel method to the spin-coating technique. The effect of Co doping concentration on the structural, morphological, optical and electrical properties of NiO thin films was investigated. X-ray diffraction (XRD) analysis revealed that all the films were polycrystalline with cubic structure and have a preferential orientation in (111) direction. Scanning electron microscopy (SEM) analysis revealed that NiO:Co films exhibited a uniform surface morphology with spherical shaped nanocrystalline grains. The energy dispersive X-ray spectroscopy (EDS) spectra confirmed the presence of Ni, O and Co elements in the doped films. Atomic force microscopy (AFM) images revealed that the deposited films have a low roughness value varying between 3.04 and 5.76 nm. All the films showed a high transmittance, ranging from 70 to 85%, in the visible and near-infrared (NIR) regions and the band gap value was reduced from 3.80 eV to 3.76 eV after doping. The room temperature photoluminescence (PL) spectra showed the presence of defects such as nickel vacancies (VNi) playing an important role in improving the conductivity of the films. The lowest electrical resistivity value equal to 1.08 × 10−2 Ω cm and the highest values of figure of merit varying between 6.17 × 10−5 Ω-1 and 1.7 × 10−4 Ω-1 in the visible region were obtained for the sample doped with 3 at. % Co, which can be useful in various optoelectronic applications.

Temperature-dependent oxygen reduction activity of NiO thin film

The temperature-dependence activity of nickel oxide (NiO) thin films for the oxygen reduction reaction (ORR) in 1 M KOH was investigated using sol–gel and spin coating techniques. The peak current density for the ORR was evaluated between room temperature and 100 °C, showing an increase with temperature. XRD and SEM confirmed the formation of cubic phase NiO and uniform morphology of the thin film, respectively. Cyclic voltammetry was used to evaluate the electrocatalytic performance of the NiO film and its temperature sensitivity. The increased activity was attributed to the increased apparent activation energy of the ORR, which also reflected the semiconducting properties of NiO thin film. The findings provide valuable insights into the electrocatalysis of ORR on NiO, which has potential applications in the development of high-performance cathode catalyst.

Effect of Li doping on the structural, linear and nonlinear optical properties of NiO thin films

Nickel oxide (NiO) is a transparent conductive oxide material that has interesting physical properties, making it one of the most promising materials for a variety of modern technological applications. The interest of this work is to study the structural and optical properties of pure and Li doped NiO thin films deposited using spray pyrolysis on glass substrates. The samples were prepared at 480 °C with various concentrations of Li doping (1, 2, 3, and 5%). X-Ray Diffraction (XRD) was employed to study the structural characteristics including the crystallite size, dislocation density, and lattice strain. Meanwhile, UV visible spectroscopy was used to study the optical properties. The results revealed a polycrystalline cubic structure with (200) crystal plan being the preferred orientation for the produced films. On the other hand, (Li: NiO) films have shown a high transmittance ranging between 60 and 80%. Also, the bandgap values (Eg), were found to be significantly affected by the Li doping ratios to take values from 3.38 to 3.66 eV. Furthermore, diverse linear and nonlinear optical properties were examined. It was found that the nonlinear properties values of χ1, χ3, and n2 to were improved when lithium doping is incorporated into the NiO lattice.

Dopant concentration influence on the optical properties of NiO thin films doped by Al and Nb deposited by DC and RF magnetron sputtering

Dopant concentration influence on the optical properties of NiO thin films doped by Al and Nb deposited by DC and RF magnetron sputtering

Study on structural, morphological, optical, and luminescence properties of nickel oxide thin-film synthesized by dip-coating technique

Nickel oxide is one of the best materials for fabricating optical devices. The Dip-coating technique was used to deposit nickel oxide thin films on a glass substrate. Nickel acetate tetrahydrate Ni (Ac) 2·H2O was used as starting precursor and monoethanolamine (MEA) was added as a catalyst. These fabricated films were pre-heated at 150 °C for 10 min and then annealed in the air at 400–700 °C temperatures. XRD, UV–Vis-NIR, FESEM, EDAX, and photoluminescence techniques are used for analyzing the fabricated films. FESEM and EDAX studies confirmed the surface and the elemental analysis of the prepared films. X-ray diffraction studies confirmed the structure of the Nickel oxide film. The UV–Vis-NIR spectrometer was used to analyze the transmission and absorption spectra of the films.

Effect of Bi doping on the structural and optical properties of NiO thin films

Nickel Oxide (NiO) based thin films have drawn widespread attention in optoelectronics applications because of their superior optical and electrical properties. Herein, the effect of Bi doping on the microstructure, phase evolution, composition, electrical and optical properties of NiO thin films are reported. Bi-doped NiO (0–7.5 %) thin films were deposited on glass substrates by the cost-effective spin coating technique. The X-ray diffraction studies showed that the undoped and 2.5 % Bi-doped films develop cubic structure and 5.0 % and 7.5 % of Bi doped films formed an amorphous nature. A systematic decrease in the grain size as well as surface roughness with Bi doping was noticed through AFM analysis. The films are highly transparent (80 %) and the optical band gap increases from 3.45 eV for undoped NiO to 3.99 eV for 7.5 % Bi-doped NiO thin film. The nonlinear optical susceptibility values are found to be in the range of 0.034 × 10-11 to 2.72 × 10-11 esu.

The film thickness effect on the physical properties of NiO thin films elaborated by Sol-gel method

In this work, nickel oxide (NiO) was elaborated on glass substrate at by sol-gel technique. The NiO thin films were prepared with 0.8 M Ni(NO3)2 6H2O annealed at 600 °C for 2 h. The coating process was repeated for 13, 14, 15, 16 and 17 times to obtain a thin film, which corresponded to 124, 137, 143, 147 and 166 nm of film thickness. NiO thin films were observed as nanocrystalline with cubic structure at 166 nm with (111) and (200) peaks were observed. All NiO thin films have an average transmittance of about 80 % in the visible region. The NiO thin films have a variety in the band gap energy from 3.87 to 3.94 eV. Because of the effect of deposition times, the minimum value was found at 166 nm where this condition has the highest Urbach energy. The NiO thin films have an electrical conductivity which was increased from 7.94 x10-3 to 84x10-3 (Ω.cm)-1 when film thickness increases from 124 to 137 nm. In the end, the electrical measurements were investigated by the four-point method, with the results show good electrical conductivity at 166 nm.

Fine modification of reactively sputtered NiOX hole transport layer for application in all-inorganic CsPbI2Br perovskite solar cells

In this study, nickel oxide (NiOX) thin films were prepared by direct current (DC) reactive magnetron sputtering. The various properties of NiOX thin films including deposition rate, morphology, electrical and optical properties as well as grain structure and chemical composition were systematically investigated. The material properties of NiOX were finely modified under the monitoring of target voltage during sputtering. NiOX thin films were applied as hole transport layers (HTLs) in all-inorganic CsPbI2Br perovskite solar cells (PSCs). The highest efficiency of 12.6% had been achieved for the optimized all-inorganic CsPbI2Br PSCs with the inverted structure of Glass/FTO/NiOX(HTL)/CsPbI2Br/ZnO@C60 (electron transport layer, ETL)/Ag. The PSC still yielded over 90% of its initial power output after 10 h operation without encapsulation.

Influence of annealing on properties of SILAR deposited nickel oxide films

Nickel Oxide (NiO) thin films have been grown by Successive Ionic Layer Adsorption and Reaction (SILAR) method on glass substrates at room temperature. Grown NiO thin films subsequently annealed from 200 °C to 400 °C for 0.5 h. The effect of annealing temperature on the structural, morfological, molecular and optical properties were analyzed. NiO thin films were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), fouirer transform infrared spektrofotometre (FTIR) and UV–vis spectrophotometer respectively. The crystal and surface properties of NiO thin films developed with annealing temperature. The energy band gap values were reduced from 3.3 to 3.11 eV depending with annealing temperature.

Effect of substrate temperature and oxygen partial pressure on RF sputtered NiO thin films

Nickel oxide (NiO) thin films were deposited by RF sputtering process and the physical properties were investigated for varying substrate temperatures and oxygen partial pressure. The variation of the crystallographic orientation and microstructure of the NiO thin films with an increase in substrate temperature were studied. It was observed that NiO thin films deposited at 350 °C shows relatively good crystalline characteristics with a preferential orientation along (111) plane. With the optimum substrate temperature of 350 °C, the NiO thin films were deposited under various oxygen partial pressures at the same experimental conditions. The structural, optical and electrical properties of NiO thin films under varying oxygen partial pressure of 10%–50% were investigated. From XRD it is clear that the films prepared in the pure argon atmosphere were amorphous while the films in oxygen partial pressure exhibited polycrystalline NiO phase. SEM and AFM investigations unveil that the higher substrate temperature improves the microstructure of the thin films. It is revealed that the NiO thin films deposited at oxygen partial pressure of 40% and a substrate temperature of 350 °C, showed higher electrical conductivity with p-type characteristics.

Effect of Precursor Concentration on Structural Optical and Electrical Properties of NiO Thin Films Prepared by Spray Pyrolysis

Undoped nickel oxide (NiO) thin films were deposited on 500°C heated glass substrates using spray pyrolysis method at (0.015–0.1 M) range of precursor. The latter was obtained by decomposition of nickel nitrate hexahydrate in double distilled water. Effect of precursor concentration on structural, optical, and electrical properties of NiO thin films was investigated. X-ray diffraction (XRD) shows the formation of NiO under cubic structure with single diffraction peak along(111)plane at2θ=37.24°. When precursor concentration reaches 0.1 M, an increment in NiO crystallite size over 37.04 nm was obtained indicating the product nano structure. SEM images reveal that beyond 0.04 M as precursor concentration the substrate becomes completely covered with NiO and thin films exhibit formation of nano agglomerations at the top of the sample surface. Ni-O bonds vibrations modes in the product of films were confirmed by FT-IR analysis. Transparency of the films ranged from 57 to 88% and band gap energy of the films decreases from 3.68 to 3.60 eV with increasing precursor concentration. Electrical properties of the elaborated NiO thin films were correlated to the precursor concentration.

Studies on Nanocrystalline Nickel Oxide Thin Films for Potential Applications

Nickel oxide (NiO) thin films were prepared by Chemical Bath Deposition (CBD) method. X-ray diffraction (XRD) analysis was used to study the structure and crystallite size of NiO thin film. The surface morphology was studied using scanning electron microscopy (SEM). The optical properties were studied using the UV-Visible spectrum. The dielectric properties of NiO thin films were studied at different frequencies and different temperatures.

Electronic, Optical and Electrical Properties of Nickel Oxide Thin Films Grown by RF Magnetron Sputtering

Nickel oxide (NiO) thin films were grown on soda-lime glass substrates by RF magnetron sputtering method at room temperature (RT), and they were post-annealed at the temperatures of 100℃, 200℃, 300℃ and 400℃ for 30 minutes in vacuum. The electronic structure, optical and electrical properties of NiO thin films were investigated using X-ray photoelectron spectroscopy (XPS), reflection electron energy spectroscopy (REELS), UV-spectrometer and Hall Effect measurements, respectively. XPS results showed that the NiO thin films grown at RT and post annealed at temperatures below 300℃ had the NiO phase, but, at 400℃, the nickel metal phase became dominant. The band gaps of NiO thin films post annealed at temperatures below 300℃ were about 3.7 eV, but that at 400oC should not be measured clearly because of the dominance of Ni metal phase. The NiO thin films post-annealed at temperatures below 300℃ showed p-type conductivity with low electrical resistivity and high optical transmittance of 80% in the visible light region, but that post-annealed at 400℃ showed n-type semiconductor properties, and the average transmittance in the visible light region was less than 42%. Our results demonstrate that the post-annealing plays a crucial role in enhancing the electrical and optical properties of NiO thin films.

Electronic, electrical and optical properties of undoped and Na-doped NiO thin films

The electrical and optical properties as well as the electronic structure of sodium-doped (Na-doped) nickel oxide (NiO) thin films were investigated using X-ray photoelectron spectroscopy (XPS), reflection electron energy loss spectroscopy (REELS), X-ray absorption near edge structure, and extended X-ray absorption fine structure. The XPS results confirmed the presence of NiO bonds of the NiO phase for all films via the Ni 2p spectra. The NiO thin films annealed above 200°C have both nickel oxide and nickel metal phase. The REELS spectra showed that the band gaps of NiO thin films after Na doping were decreased. Na-doped NiO thin films exhibited relatively low resistivity compared to undoped NiO thin films. In addition, the Na-doped NiO thin films deposited at room temperature have p-type conductivity with a low electrical resistivity of 11.57Ωcm and high optical transmittance of 80% in the visible light region. Our results demonstrate that Na doping plays a crucial role in enhancing the electrical and optical properties of NiO thin films.

Nanoporous network of nickel oxide for ammonia gas detection

The nanoporous network of nickel oxide (NiO) thin films have been synthesized by a facile chemical bath deposition method (CBD) at various deposition times. The X-ray diffraction (XRD) patterns of annealed NiO films revealed low intense peaks, confirming nanocrystalline nature with cubic structure. The scanning electron microscopy (SEM) images exhibited well-defined and nanoporous interconnected network. The gas sensing properties of NiO thin films for ammonia gas were investigated. The measurements revealed that the sample deposited at 50min (Ni50) exhibit better gas sensing performance, due to its high surface area and maximum pore-volume available for gas adsorption.

Structural, Optical and Electrical Properties of NiO Thin Films Prepared by Low Cost Spray Pyrolysis Technique

Nickel Oxide (NiO) thin films are fabricated using fresh and aged precursor solutions using a low cost simplified spray pyrolysis technique. Structural, optical and electrical properties of two different films were studied. The structural studies show that the film prepared from the aged solution has more grain size (60.3nm) than the film prepared by fresh solution (21nm). From the optical studies it is found that, the band gap of film from fresh solution have 3.6eV while the band gap of film from aged solution is about 3.5eV. The refractive index (n) is measured with the help of PUMA software and for the film from fresh solution it remains at 1.95 through visible region. However, for the film from aged solution, it varies from 2 to 1.78 in visible region. The calculated extinction coefficient (k) values of the films show no significant variation in visible and NIR range. The electrical studies confirm that the grown films are p- type. The resistivity measured for two films shows that the resistivity is low (2.271×10 2 Ω cm) for the film prepared by fresh solution and it is high (2.725×10 2 Ω cm) for the other one. 