Nickel Oxide Thin Films Research Articles

Role of different atmosphere gasses during annealing in chemical-solution-deposition NiO thin films processing

Thermally processed nickel oxide (NiO) thin films were synthesized from nickel hydroxide films obtained by chemical solution deposition. Potential applications derived from electronic properties were studied by thermally treated thin films under two controlled annealing atmospheres. The NiO thin films with thicknesses between 160 and 192 nm and a nanowall-like morphology were obtained. Amorphous thin films with high optical transmittance in the visible region of around 85 % and ∼3.7 eV bandgap energy were obtained. The chemical composition of the NiO films was determined by X-ray photoelectron spectroscopy (XPS), which confirmed that the films were indeed composed of NiO after thermal treatment. The electrical properties were acquired through the Hall effect technique. The NiO films exhibit a p-type conductivity; the highest carrier concentration is 5×1015 cm−3. Mobility up to 11 cm2∙V−1∙S−1 and low resistivity of 9×102 Ω∙cm. These properties are suitable for applications in transparent electronic devices.

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.

Electrochromic Displays via the Room-Temperature Electrochemical Oxidation of Nickel.

Electrochromism refers to the persistent and reversible change in color by applying an electric field. The phenomenon involves the insertion and extraction of electrons and ions within the active material. There is a keen interest in electrochromic (EC) materials, since they exhibit a wide range of potential applications. In recent years, transition-metal oxides have been widely investigated as EC materials due to their low power requirement, high coloration efficiency, and memory effect under an open-circuit condition. Nickel oxide (NiO), a p-type wide band gap semiconductor, exhibits attractive features such as a high color contrast ratio, good chemical stability, cost-effectiveness, and good compatibility with the cathodically coloring tungsten oxide. NiO thin films have been fabricated by various methods, but these are not cost-effective, scalable, or suitable for flexible applications. With the increasing demand for flexible and soft EC devices, it is essential to find routes to fabricate NiO thin films at lower temperatures. In this work, a NiO/Ni(OH)2-based thin EC layer on fluorine-doped tin oxide-coated glass is developed via an electroless nickel (EN) deposition route, followed by room-temperature electrochemical oxidation. The deposition time is optimized to control the film thickness. The EC performance is investigated in an aqueous alkaline electrolyte (1 M KOH) by means of cyclic voltammetry, chronoamperometry, and transmittance measurements. Both the as-deposited and annealed films, after electrochemical oxidation, exhibit excellent EC properties with an optical modulation of approximately 64% (at 550 nm) and good response times of approximately 3 s (coloration) and 14 s (bleaching). A 2 × 2 display obtained by patterning the EN deposition is also demonstrated as part of this work.

Chemical bath deposited Nickel oxide thin film as electrode material for pseudocapacitors

We have synthesized thin films of nickel oxide (NiO) on silver and glass substrates, at very low temperature of 60°C, by chemical bath deposition (CBD) method. The precursor used consists of nickel nitrate and aqueous ammonia. Structural characteristics were studied using x-ray diffraction (XRD) and morphological studies were done using scanning electron microscopy (SEM). Ultraviolet-visible (UV-Vis) spectroscopy was used for optical studies. To investigate electrochemical behaviour of thin film electrode materials, cyclic voltammetry (CV) measurements were conducted. For electrochemical studies the galvanostatic charge/discharge (GCD) tests were also conducted. The formation of face centred cubic NiO structure was confirmed using XRD. The scanning electron microscopy images show uniform distribution of worm-like porous morphology. CV measurements revealed the capacitive behaviour of the films.

Power dependent nonlinear optical characteristics and two-photon absorption of NiO/PVA thin film

The NiO/PVA thin film was prepared by drop-casting the nickel oxide nanoparticles synthesized by the chemical precipitation method. The structural and optical characteristics of the film were investigated using XRD and UV-VIS absorption. The nonlinear optical property of the Nickel oxide thin film was studied by the open aperture Z-scan method at 532 nm. The two-photon absorption coefficient of the film was calculated with different optical intensities. With increasing input intensity, the value of the two-photon absorption coefficient has decreased. This is attributed to the saturation of two-photon absorption mechanism. The NiO/PVA film can be used for optical limiting applications.

Nickel oxide thin film electrode synthesized by pneumatic spray pyrolysis with different NiCl2 concentration

Nickel oxide thin film electrode synthesized by pneumatic spray pyrolysis with different NiCl2 concentration

Effect of laser irradiation on the tribological properties of RF-sputtered nickel oxide (NiO) thin films

The present work aims at investigating the effect of laser irradiation on the tribological properties of RF-sputtered NiO thin films deposited on industrial grade aluminum substrate. A semiconductor laser based on Nd:YAG operating at its 4th harmonic wavelength, λ = 266 nm with varying laser fluence and spot size of about 5 μm is irradiated on the NiO film. The localized heating allows for smoothening of the NiO film along with contributions to the changes in the stoichiometry of NiO (reduction of excess oxygen). In particular, the effects of tuning laser fluence and the subsequent tribology tests pertaining to the coefficient of friction variations for tribological tests are discussed.

Modulation of the conductive behavior of NiO thin film deposited by HiPIMS through varying the O2 flow ratio

Nickel oxide (NiO) films were prepared through High Power Impulse Magnetron Sputtering (HiPIMS). The influence of O2/(Ar + O2) flow ratio (oxygen flow ratio) from 0.5% to 3% on structural and optoelectronic qualities of NiO films were studied. The results indicate that deposition rate of NiO film reduces as increase of oxygen flow ratio. Atomic force microscopy shows that as oxygen flow ratio increases, surface roughness of NiO films decrease. The transmittances of the NiO films are over 60% in the visible wavelengths. Hall effect measurements suggested that by adjusting the oxygen flow ratio NiO films with different type of conduction can be obtained. The carrier concentration of NiO films increase significantly as oxygen flow ratio goes up, which is caused by the fact that more nickel vacancies and interstitial oxygen are formed in NiO films. Therefore, the electrical conductivity enhances accordingly. The XPS analysis demonstrates the presence of both Ni2+ and Ni3+ oxidation states and also confirms the transition of conductive type of the NiO films. HiPIMS is a potential approach for depositing n type or p type transparent conductive oxide NiO films.

Electrochemically prepared Fe: NiO thin film catalysis for oxygen evolution reaction

The electrocatalysis-based nickel oxide (NiO) films and doped with various amount of iron were synthesized on stainless steel (SS) substrate by electrodeposition. X-ray diffraction analysis (XRD) and filed effect scanning electron microscopy (FE-SEM) utilized to investigate structural and morphological properties. The X-ray diffraction analysis polycrystalline cubic structure has confirmed. Surface morphology study revealed the grains are regularly scattered over the total surface of the substrates after doping. The oxygen evolution reaction (OER) properties of doped films more efficient than that of pure thin films. The 4% Fe:NiO films exhibited an over potential of 320 mV at 10 mA cm−2 current density and a Tafel slope of 89.80 mV dec−1. The electrode shows the high durability over 5 h with small degradation.

Ultraviolet Laser Sintering of Printed Nickel Oxide Nanoparticles for Thin-Film Thermistor via Aerosol Jet Printing Technology

In this study, nickel oxide (NiO) thin films were printed by an aerosol jet printer, which is capable of fabricating thin films on the curve substrate via air stream. To approach high efficiency fabricating thin film thermistors in small batch sizes, the printed NiO nanoparticle thin films were sintered by using a 355 nm wavelength ultraviolet (UV) laser; this novel fabrication method reduced several steps of the conventional manufacturing process of the thermistor. Compared with furnace heat treatments of the NiO thermistor in previous studies, the UV laser sintering not only significantly improved the electrical properties but decreased the treatment time from an hour to a second. Since the resistance declined, the thermistor has been operated at an ambient temperature, which provides ready measurement. The resistance and morphology of the thin films were analyzed for evaluating the effect of the laser treatment. To identify the proper UV laser parameters, three laser parameters, including laser output energy, frequency, and scanning speed, were studied. Due to the laser-sintering parameters, namely, 2 W, 150 mm/s, 90 kHz, and a B value of 4683 K, the resistance has been reduced from 106.8 MΩ to 6.15 MΩ at 100 °C. The experiments exhibited a series of analyses for sintering states and defects of printed NiO nanoparticle thin film, which were sintered by UV laser. For NiO nanoparticles, UV laser has higher absorption energy than that of other wavelength lasers, when excess laser output was applied to the NiO thin film, cracks were observed on the surface. It was found that the crystal plane distances were not affected by recrystallization, but the cracks were based on the XRD analysis. Based on the analysis, there were obvious regional compressive stains before the appearance of cracks, and the uneven shrinking strains caused the cracks on the surface as energy irradiation increased.

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

Electronic and Chemical Properties of Nickel Oxide Thin Films and the Intrinsic Defects Compensation Mechanism

Electronic and Chemical Properties of Nickel Oxide Thin Films and the Intrinsic Defects Compensation Mechanism

Chemical Synthesis and Electrochemical Properties of Nickel Oxide Thin Films

Chemical Synthesis and Electrochemical Properties of Nickel Oxide Thin Films

Surface characterization of NiO thin films deposited by RF-magnetron sputtering at different thickness: Statistical and multifractal approach.

Fractal and multifractal are the most important processes and concepts in describing and examining surface morphology, and for this reason, these concepts are an important approach for analyzing the properties and surface geometry of thin films. In this article, multifractal analysis was performed on images, prepared using atomic force microscopy (AFM), of the surface morphology of nickel oxide thin films deposited by RF-Magnetron sputtering at different thicknesses on the glass substrate. The effect of thickness on the surface properties of the layers was studied by applying multifractal and statistical methods on AFM images. The results obtained from the multifractal spectrum show that the surface of the nickel oxide thin films deposited at different thicknesses are multifractal. The multifractal analysis demonstrated that multifractality and complexity of the surface of nickel oxide thin films changes and decrease with thicknesses. We also used statistical parameters to better examine AFM images to study the effects of layers thickness on the deposited NiO thin films. The results indicated that the statistical parameters are a function of the layer's thickness of NiO thin films. Hence, the isotropic properties and functional parameters changed with changing surface thickness. RESEARCH HIGHLIGHTS: Multifractal analysis was applied to the AFM images to study the surface morphology of NiO thin films. The multifractal nature of the surface of NiO thin films is observed. The layers have become more isotropic with increasing thickness. The results illustrated that deposition masses occurred more at the highest sites on the surface. Multifractality of the surface of the sample decreased with increasing layer thickness.

Effect of annealing on structural, optical and electrical properties of nickel oxide thin films synthesized by the reactive radio frequency sputtering

In this paper, Nickel oxide (NiO) thin films were synthesized by the reactive radio frequency sputtering. NiO thin films were annealed at different temperatures (350, 400, 450 and 500 °C). Structural characterizations were performed using X-Ray Diffraction, Scanning Electron Microscopy (SEM), Raman spectroscopy, Infrared spectroscopy. Ultraviolet–visible spectrophotometer were used to estimate the energy band-gap and the thickness. Electrical resistivity measurements were carried out using the four-point probe method then analyzed basing on the structural characterization. The XRD patterns showed that the crystallite size increases by increasing the annealing temperature from 6.3 to 15.8 nm. The structure is cubic with lattice parameter of 4.17 nm and the dislocation and micro strain decrease by annealing. The Thin films surfaces were observed to be homogenous and without cracks. The Raman spectra proved the presence of four peaks, related to vibration of Ni–O bands. The FTIR spectra showed the NiO stretching and bending mode. The optical analyses showed that the transmittance and energy band gap augments by increasing the annealing temperature from 3.54 to 3.68 eV. Finally, the resistivity grows by annealing from 0.33 to 1.4 × 104 Ω cm and decreases by increasing the measuring temperature.

Heterostructure Silicon Solar Cells with Enhanced Power Conversion Efficiency Based on Si x /Ni3+ Self-Doped NiO x Passivating Contact.

Developing efficient crystalline silicon/wide-band gap metal-oxide thin-film heterostructure junction-based crystalline silicon (c-Si) solar cells has been an attractive alternative to the silicon thin film-based counterparts. Herein, nickel oxide thin films are introduced as the hole-selective layer for c-Si solar cells and prepared using the reactive sputtering technique with the target of metallic nickel. An optimal Ni3+ self-doped NiOx film is obtained by tuning the reactive oxygen atmosphere to construct the optimized c-Si/NiOx heterostructure band alignment. A thin SiOx interlayer was further introduced to reduce the defect of the c-Si/NiOx interface with the UV–ozone (UVO) treatment. The constructed p-type c-Si/SiOx/NiOx/Ag solar cell exhibits an increase in the open voltage from 586 to 611 mV and achieves a 19.2% conversion efficiency.

Effect of Ethanolamine and HCl on structural and optical properties of Nickel oxide thin films

In the present work, Nickel Oxide thin films were prepared by spin coating technique. The effects of Ethanolamine and HCl on structural and optical properties of NiO thin films are studied. The structural properties of NiO thin films were examined by X-ray Diffraction (XRD). The amorphous nature of NiO thin films were observed from XRD pattern. FESEM studies of the surface morphology of NiO thin films exhibits smooth and uniform surface with average particle size of 200 nm for Ethanolamine doping sample and 300 nm for HCl doping sample. The functional groups and surface roughness of NiO thin films were investigated by FTIR and 3 D Laser Profilometry. The surface roughness of the prepared samples increases with increasing thickness from 4.49 μm to 6.81 μm. The optical characteristics of the samples were determined by UV Visible Spectrophotometer. This results shows that the prepared NiO thin films exhibits high optical transparency.

Electrodeposited Nickel Oxide Thin Film for Electrochemical Water Splitting

Cheaper and capable electrocatalysts play an important role in electrochemical water splitting. Here, we have prepared nickel oxide (NiO) thin film as an electrocatalyst on the stainless steel substrate by electrodeposition method. XRD and FESEM techniques were used to study structural and morphological properties of prepared electrocatalyst. Further, obtained (NiO) thin film electrocatalysts are used for Oxygen evolution reaction (OER) by LSV in 1 M KOH. The electrodeposited (NiO) thin films exhibited overpotential of 212 mV at a current density of 5 mA cm−2, and a Tafel slope of 75.7 mV dec−1. This electrocatalyst is stable for at least 15 hrs. in the catalytic activity.

Oxygen-vacancy induced ferroelectricity in nitrogen-doped nickel oxide

This paper reports the onset of ferroelectricity in NiO by breaking the crystallographic symmetry with oxygen vacancies created by N doping. Nitrogen-doped NiO was grown at room temperature by RF sputtering of Ni target in Ar–O2–N2 plasma on silicon and fused silica substrates. The impact of the nitrogen doping of NiO on microstructural, optical, and electrical properties has been investigated. According to x-ray diffraction investigations, by increasing the N doping level in NiO, a transition from (002) to a (111) preferential orientation for the cubic NiO phase was observed, as well as a lattice strain relaxation, that is usually ascribed to structural defect formation in crystal. The x-ray diffraction pole figures the presence of a distorted cubic structure in NiO and supports the Rietveld refinement findings related to the strain, which pointed out that nitrogen doping fosters lattice imperfections formation. These findings were found to be in agreement with our far-infrared measurements that revealed that upon nitrogen doping a structural distortion of the NiO cubic phase appears. X-ray photoemission spectroscopy measurements reveal the presence of oxygen vacancies in the NiO film following nitrogen doping. Evidence of ferroelectricity in nitrogen-doped NiO thin films has been provided by using the well-established Sawyer–Tower method. The results reported here provide the first insights on oxygen-vacancy induced ferroelectricity in nitrogen-doped nickel oxide thin films.

An Electrochemical Investigation of Methanol Oxidation on Thin Films of Nickel Oxide and Its Composites with Zirconium and Yttrium Oxides

The present work is focused on the fabrication of NiO-ZrO2/FTO and NiO-Y2O3/FTO thin films via a simple dip-coating method. The films are deposited from precursor solutions of Ni(CH3COO)2·2H2O, Zr(CH3COO)4, Y(CH3COO)3·H2O in methanol. The synthesized films, after proper characterization, are employed for electrochemical oxidation of methanol. The analytical techniques such as X-ray diffraction (XRD), Raman, and Infrared (IR) spectroscopy reveal the successful formation of crystalline thin films of mixed metal oxide without any additional impurities. Further, X-ray photoelectron spectroscopy (XPS) results, confirm the composition and oxidation state of all the elements present in thin films. The field emission scanning electron microscopy (FESEM) further aided to identify the uniformity and porous nature of composite thin films while the energy-dispersive X-ray spectroscopy (EDS) confirms the targeted elemental composition of the prepared thin films is in good agreement with precursors. The electrochemical oxidation of methanol results reveals that NiO-Y2O3/FTO and NiO-ZrO2/FTO thin films showed current densities of 6.2 mA/cm2 and 10 mA/cm2 at 0.65 V, respectively, against Ag/AgCl/3M KCl using 0.6 M methanol solution. Furthermore, Chronoamperometric (CA) results show good stability of NiO-ZrO2/FTO and NiO-Y2O3/FTO thin films with observed current decay of 10% and 6.8% of the initial current density, respectively. Moreover, the effect of scan rate and concentration of metals in a catalyst was also investigated. The Electrochemical impedance studies (EIS) further support electrochemical results, where the lower charge transfer resistance (Rct) values are recorded for composite thin films as compared to the pure metal oxide thin films (NiO/FTO, ZrO2/FTO, and Y2O3/FTO).