Doped NiO Thin Films Research Articles

Preparation of Co doped NiO thin films with excellent switching time and coloring efficiency through sol-gel spin coating

This paper fabricates novel electrochromic films through the sol-gel spin coating of nickel (Ni) and tunable cobalt (Co) atoms. The particle size, band gap, conductivity, and response time of the electrochromic films were improved by accurately adjusting the doping ratio of Co atoms from cobalt acetate. According to the results of scanning electron microscope and X-ray diffraction, the particles size of the Ni-Co oxide film decreased from 9 nm to 25 nm, with the increase in Co content. The reduction of the band gap enhanced the film conductivity, resulting in better electrochromic properties. The electrochemical and optical measurements show the excellence of the film in switching time and coloring efficiency: thanks to incorporating Co atoms, the switching time was shortened from 15.2 s to 10.2 s, and the coloring efficiency was increased from 35.57 to 42.5 cm2 C−1. Overall, the proposed film has a promising future for electrochromic applications.

Synthesis and Characterization of Pure and Cu-doped NiO Thin Films for Detection of Ethanol

Herein, a highly sensitive, selective and stable ethanol sensor based on nanostructured Cu doped NiO thin films is reported. Pure and Cu doped NiO thin films were prepared using spray pyrolysis technique with different copper concentrations. The XRD, Raman, SEM, XPS and TEM were used to investigate the structural, morphological and compositional properties of deposited films. The XRD studies confirmed that deposited films exhibit cubic structure with polycrystalline nature. Raman spectroscopy of the deposited NiO based thin film reveals as single-phonon first-order longitudinal-optical LO mode and double-phonon second-order longitudinal-optical mode 2LO. Scanning electron microscopy (SEM) has demonstrated a significant variation in the morphology of the coated films. X-ray photoelectron spectroscopy (XPS) results revealed that successful doping of copper in NiO matrix, whereas TEM investigations revealed a nanometric crystal size in Cu doped NiO. Gas sensing performance of the deposited thin films was measured using static distribution technique towards 50 ppm ethanol gas at room temperature. Cu doped NiO thin film (4 wt.% ) has shown improved sensing features towards 50 ppm of ethanol with good selective, sensitive and stable features with quick response and recovery characteristics.

60 MeV Si ion beam irradiation induced modifications in the structural and optical properties of Li doped NiO thin films

Li doped NiO films grown on FTO substrates through spin coating technique were irradiated using 60 MeV Si ions. The films were investigated via several approaches including grazing incidence X-ray diffraction, attenuated total reflectance-Fourier transform infrared spectroscopy, atomic force microscopy, micro-Raman and UV–visible spectroscopy. The crystalline nature of films declines with the initial face-centered cubic structure for 1x1014 ions cm−2 owing to the energy loss of Si ions in a Li doped NiO (Li:NiO) lattice during the generation of defects. The crystallite size of samples was evaluated using Scherrer’s equation. The vibrational modes were investigated via micro-Raman analysis. AFM topography was recorded for pristine and Si ion irradiated films. The ion fluence of Si ion in the used energy range lowers the transmittance Li:NiO films as compared to the pristine.

The determination of urbach energy and optical gap energy by many methods for Zn doped NiO thin films fabricant semiconductor by spray pyrolysis

The effect of Zn doping on optical, structural and electrical properties of Ni1-xZnxO thin films has been successfully deposited on glass substrate by Spray Pyrolysis technique. The main objective of this research is to study the Ni1-xZnxO thin films to determine the optical gap energy by various methods and compare it with calculated values. The transmission spectra shows that the Ni1-xZnxO thin films have a good optical transparency in the visible region. The optical gap energy varied between 3.50 and 3.75 eV, which was determined by various methods and equations. they are explained in the curves of A, A2 , α, α2 (Ahυ) 2 and (αhυ) 2 as a function of the photon energy hυ. We observed that the suitable method to calculate the optical gap energy is (Ahυ) 2 versus hυ, but this method can't be related to the film thickness. The urbach energy of the Ni1-xZnxO thin films also was determined by the curves of LnA and Lnα as a function of photon energy hυ. We deduced that LnA versus hυ is also suitable to estimate the urbach energy. However, the Ni0.90Zn0.10O thin films have a few defects with minimum value of urbach energy. The Ni0.90Zn0.10O thin films have maximum value of optical gap energy. XRD patterns of the Ni1-xZnxO thin films indicate that films are polycrystalline with cubic structure. The electrical conductivity of our films is in the order of 9*10-3 (Ω.cm)-1 .

Physical vapour deposition of Zn2+ doped NiO nanostructured thin films for enhanced selective and sensitive ammonia sensing

Highly sensitive and selective ammonia sensors based on Zn2+ doped NiO thin films with well-controlled morphology through a substrate temperature variation developed with the electron beam evaporation method. The obtained films were systematically studied using various characterization techniques involving X-ray Diffraction, FESEM, EDS, XPS, AFM, RBS, UV–visible spectrophotometer and Hall effect measurements. The successful preparation of Zn2+ doped NiO thin films has been confirmed by structural, elemental and chemical analysis. The fabricated Zn: NiO sensors have shown excellent selectivity towards ammonia at 100 ppm concentration at room temperature. Sensors deposited with high temperatures ((≥300°C) were more sensitive towards ammonia with a fast response and recovery time (10/15 s) and a low detection limit of 10 ppm. The enhanced ammonia sensing performance could be attributed to the high surface-to-volume ratio and high porosity of films deposited at substrate temperature (≥300°C), and electronic sensitization through Zn2+ incorporation into NiO lattice. The addition of Zn into NiO caused rapid adsorption of oxygen adsorbates on the surface of doped NiO, which increased the sensor's response. The sensing mechanism for the detection of ammonia is formulated. The outcome of this work opens a pathway for the efficient detection of ammonia at ambient temperature for numerous medical and industrial applications.

Highly sensitive ultraviolet photodetectors fabricated from rare earth metal ions doped NiO thin films via nebulizer spray pyrolysis method

In this report, an automated nebulizer spray pyrolysis (NSP) route was chosen to prepare pure NiO and (1%- Er, Tb, Pr) RE doped NiO thin films samples on glass slides at 450 °C using nickel chloride as a source. Through systematical investigation their microstructure (XRD), surface morphology (FESEM), composition (EDX), optical (UV-Vis absorption and photoluminescence), UV photoconduction (Keithly source meter 2450) information were obtained. The face centered cubic structure occupying the space group (Fm3m) of NiO thin films was confirmed without any impurity phase through X-ray diffraction (XRD) analysis. Also, the effect of (1%- Er, Tb, Pr) RE doping with NiO on the crystallite size confirms that the higher ionic radii Pr-doped NiO sample possess a higher crystalline size of 31 nm. The morphological studies show that the pure and RE doped with NiO thin film samples possess highly dense cloudy spherical morphology. UV studies show that the Pr doped NiO sample exhibits higher absorption and lower bandgap of 3.49 eV. The emission peaks related to the presence of defect sites were studied through the PL analysis showing higher recombination centers occur for the Pr-doped NiO sample suggesting the sample possesses a higher carrier concentration. The fabricated pure and (1%- Er, Tb, Pr) RE doped NiO thin film photodetectors were analyzed through I-V, photo sensing parameters, and transient characteristics. The results show that the Pr-doped NiO photodetector sample possesses higher photocurrent, better responsivity (3.45 ×10−1 AW−1), detectivity (1.20 ×1010 Jones), EQE (81%), and the photo transient characteristics shows better response and repeatability of the photodetector samples under varying UV light intensities (1–5 mW/cm2). From the photo sensing results, it is confirmed that the Pr doped NiO photodetector sample can be better suited for the application of photodetectors.

Cu doped NiO thin film photocathodes for enhanced PEC performance

The present report describes the fabrication of undoped NiO and Cu doped NiO based photocathodes synthesized by sol gel spin coating technique. Mott-Schottky, LSV and EIS measurements have been carried out to investigate the PEC properties of these photocathodes. 3% Cu doped NiO film exhibits the highest PEC performance among all photocathodes. The p-type semiconducting nature of all thin film samples has been confirmed from the M-S plots. Also, the values of carrier density have been tuned from 1.18 × 1020 to 1.36 × 1020 cm−3 for undoped NiO and 3% Cu doped NiO thin films. VB CB levels of the as-prepared photocathodes have been calculated from absorption spectra. 3Cu:NiO exhibits a significantly higher photocurrent density of −6.97 mA/cm2 at −1.5 V vs. Ag/AgCl in 0.1M NaOH solution under UV illumination. The superior PEC performance is due to efficient charge transport and reduced recombination rate of the photogenerated electron-hole pairs. These findings demonstrate the potential of Cu doped NiO photocathodes in water splitting applications.

Structural, Optical and Dielectric Properties of Nd Doped NiO Thin Films Deposited with a Spray Pyrolysis Method

The effect of Nd doping (1, 3 and 5 wt%) on the structural, morphological, electrical and optical properties of NiO thin films deposited on glass substrates using nebulizer spray pyrolysis method are investigated. The X-ray diffraction study reveals cubic structure with an improvement in crystallinity upon the incorporation of Nd into NiO lattice. The films are > 50% transparent in the high wavelength region. The absorption spectra witnesses a sharp fall in the wavelength range, 300 nm < λ < 600 nm reflecting the semiconducting nature of these films. The optical direct (indirect) band gap values obtained using Tauc’s relation decrease from 3.67 eV (3.00 eV) for pure NiO to 3.38 eV (2.44 eV) for 3 wt% Nd:NiO. The linear refractive index (n) values estimated using different models are compared. Using the average linear refractive index along with optical direct band gap, the high-frequency and static dielectric constants; the linear and non-linear optical susceptibilities and non-linear refractive index are calculated. It is observed that all these quantities enhance with Nd doping whereas the static dielectric constant decreases with an increase in Nd content. The high frequency dielectric constant and static dielectric constant values are observed to vary between 5.08–5.45 and 51–32, respectively. The values of linear and non-linear optical susceptibilities and non-linear refractive index are found vary between 0.325–0.354, 1.90 × 10–12–2.67 × 10–12 esu and 3.17 × 10–11–4.31 × 10–11 esu, respectively.

Study the Effect of Cu Doping on Optical and Structural Properties of NiO Thin Films

Abstract In this work, copper doped nickel oxide as the thin films have been elaborated by a spin coating method, the nickel chloride hexahydrate (0.8M) and copper (II) chloride dehydrate (Cu/Ni = 0, 2.15, 4.3, 8.6 and 12.9 At.%) were used to prepare the Cu doped NiO thin films. The Cu doped NiO thin films were heated at a crystallization temperature of 600 °C with 2 h. The obtained thin films by spin coater method have a film thickness in the order of 400 nm. The prepared Cu doped NiO thin films have a polycrystalline with cubic structure (200) peak was observed. The optical property shows that the prepared thin films have a transmittance of about 70 %. The Cu doped NiO thin films have minimum bandgap energy is 3.85 eV at 12.9 at.%, the thin film deposited at 8.6 at.% has the highest value of Urbach energy is 425 meV. The Cu doped NiO thin films have a high electrical conductivity of 8.6 at% it is 7 (Ω.cm)−1. The prepared Cu doped NiO thin film was suitable for gas sensing applications due to the existing phase and higher electrical conductivity.

Highly sensitive and selective NO2 chemical sensors based on Al doped NiO thin films

Al-doped Nickel oxide (Al:NiO) nanostructured thin films, prepared by RF sputtering technique, were tested for NO2 gas detection. The films were deposited on alumina substrates with thicknesses ranging between 52 nm and 167 nm, while the at.% of Al was varied from 5.0% to 6.7%. The effect of the thickness on the morphological, structural and optical properties was investigated. Moreover, the sensing characteristics were examined and optimized with respect to film thickness and operating temperature (200 °C and 300 °C), at NO2 concentrations ranging from 200 ppb to 2500 ppb and in presence of a constant relative humidity (RH) of 40%. An ultimate response of 271% towards a NO2 concentration of 200 ppb at 200 °C was obtained, concluding that Al:NiO can be potentially used as a sensing material for this specific gas.

An impact of La doping content on physical properties of NiO films facilely casted through spin-coater for optoelectronics

With a view to study the optical properties of La doped NiO thin films and make them available for futuristic optoelectronic devices, these films were deposited by spin coating technique assisted by sol-gel. The structural, morphological, linear and non-linear optical properties of the as-prepared films were studied. XRD shows that the films were polycrystalline, and the growth of grains was studied by AFM. The Raman spectra of the pure and La doped films were analyzed over the range 200–1400 cm−1. The optical study of the doped films shows that they are highly transparent in the visible region. Moreover, the direct and indirect band gaps of the films were evaluated and are found to be in the range of 3.84–3.96 eV for the direct and 3.26–3.4 eV for the indirect bandgap. Higher value of non-linear susceptibilities and refractive index opens a window for wide use of these films in optoelectronic devices.

Synthesis of copper-doped nickel oxide thin films: Structural and optical studies

The preparation of nanostructured undoped and Cu doped NiO thin films on to amorphous glass substrate via successive ionic layer absorption and reaction (SILAR) is debated. The optical and structural properties of the nanostructure undoped and Cu doped NiO thin films were studied. The characterization techniques such as UV–visible spectroscopy, Scanning Electron Microscopy and Atomic Force Microscopy were used to investigate undoped and Cu doped NiO thin films. Because of UV–Vis analysis of undoped and Cu doped NiO thin films, the optical band gap value decreased from 3.34 to 2.01 eV with the increase of Cu concentration. As a result of SEM analysis, it was seen that the nanostructures formed when the NiO thin film was enlarged changed its shape as the Cu concentration increased. In the results of AFM analysis, it was observed that copper coated on the surface began to decrease on surface roughness.

Effect of Substrate Temperature on the Optical and Electrical Properties of Nitrogen-Doped NiO Thin Films

NiO is a widely used p-type semiconductor. The desired optical and electrical properties of NiO vary in different application fields. To modulate the properties of NiO, nitrogen (N)-doped NiO thin films were synthesized by reactive radio-frequency magnetron sputtering on ITO-coated glass substrates. The influence of substrate temperature on the properties of NiO was investigated. XRD studies indicated a cubic structure. With the increase of the substrate temperature, the average transmittance in the visible region gradually reduced from 90% to 50%. The bandgap energy narrowed from 3.5 to 3.08 eV. The intensity of the PL spectra weakened, and the electrical conductivity rose. Overall, changing the substrate temperature is an effective method to modulate the optical and electrical properties of N-doped NiO thin films.

Dispersive optical nonlinearities and optical path length compensation in NiO/Al doped NiO bilayer thin film

Dispersive optical nonlinearities in pulsed laser deposited undoped and 5% Al doped NiO thin films reveal negative and positive optical nonlinearities, respectively. The cause of optical nonlinearity is assigned to the presence (absence) of oxygen vacancies in undoped NiO (5% Al doped NiO) thin film which leads to photodensification (photoexpansion) and gives rise to thermo-optic effect. Quite interestingly, the observation of opposite kinds of nonlinearities in a NiO/Al doped NiO bilayer film, leads to the neutralization of the dispersive optical nonlinearity and one expects a resultant optical path length compensation.

Europium incorporation dynamics within NiO films deposited by sol-gel spin coating: Experimental and theoretical studies

Europium doped NiO thin films were grown onto glass substrates via sol-gel spin coating. The evolution of crystal structure, surface topography, and optical properties of NiO was investigated as a function of Eu doping concentration. AFM observations and XRD analysis revealed that NiO:Eu films composed of nano-sized grains exhibit a polycrystalline cubic bunsenite structure with (200) preferential orientation. Optical study showed that the optical band gap of doped NiO films initially increased with low Eu incorporation ratio then decreased with higher Eu content. However, the Urbach energy increased gradually with Eu doping level. First principle calculations were performed to elucidate the changes on electronic, magnetic and optical properties of NiO due to Eu doping. The incorporation of Eu within NiO host lattice induced a strong hybridization between Eu-f and Ni-d states resulting in important changes of bulk magnetization.

Magnetic and optical properties of electrodeposited nanospherical copper doped nickel oxide thin films

Copper doped nickel oxide (NiO:Cu) thin films were synthesized via electrodeposition technique. X-ray diffraction, Scanning Electron Microscope, UV–visible spectroscopy, Vibrating Sample Magnetometer techniques and electrochemical analysis were utilized for the study of the structural, morphological, optical, magnetic and cyclic voltammogram properties respectively of both undoped and doped NiO thin films. The crystallographic studies of the undoped and doped NiO thin films showed that they are polycrystalline with cubic structure. Surface morphology of both the undoped and doped thin films showed nanocrystalline grains with spherical shaped particles. The optical studies showed a decrease in band gap energy from 3.34 eV to 3.32 eV and finally to 3.20 eV for the undoped, 2% and 3% respectively. The refractive index peaked between 2.60 and 2.65 while the calculated extinction coefficient values of the doped thin films have significant variation in the visible and NIR range. The studies of magnetization saturation values were found to be 1.52E-4 and 2.29E-4 for 2% and 3% doped respectively with low remanence values. Electrochemical studies revealed good cyclic voltammograms of the deposited films. These values indicate that the electrodeposited Cu doped NiO thin films are good candidates for magnetic applications.

Structural, morphological, optical and third order nonlinear optical response of spin-coated NiO thin films: An effect of N doping

The present work deals with the deposition of NiO and Nitrogen (N)-doped NiO thin films by sol-gel spin coating technique. Structural, morphological, linear and non-linear optical characteristics of undoped and N-doped (1–15 wt%) NiO films were studied. From XRD measurements, it is evident that single phase nano crystalline NiO is formed for all doping concentrations. Surface morphology study shows that higher concentration of N doped NiO thin films were of high quality and EDX mapping confirmed the doping of Nitrogen in films. The Raman spectra of the studied films were analyzed over the range of 1400-200 cm−1. The optical studies confirm that as doping increases, transparency of the film decreases (except at 10% N doping) and the band gap narrows. Nonlinear parameters such as refractive index and susceptibilities also depend on N dopant concentration. Z-scan studies viz., absorption index, nonlinear refractive index were carried out on undoped and N doped NiO samples and the results were matched with theoretical calculated values.

Structural, Optical and Electrical Studies on Chemical Spray Deposited Cu Doped NiO Thin Films for p–n Junction Diode Application

Structural, Optical and Electrical Studies on Chemical Spray Deposited Cu Doped NiO Thin Films for <i>p</i>–<i>n</i> Junction Diode Application

Transparent nanostructured Co doped NiO thin films deposited by sol‒gel technique

In this work, the effect of annealing temperature (540, 560, 580 and 600 °C) on synthesis of Co doped NiO thin films were investigated. Co doped NiO thin films were deposited by spin coating method with molarity of 0.8 mol.l−1 at room temperature. The XRD analyses showed that the NiO films have a cubic structure with high crystallite size of in Co doped NiO thin film is 82.57 nm of (200) plane was obtained at 580 °C. This is to improvement the structure crystallinity. The optical transmission showed that the band gap energy was found increases from 3.2265 to 3.8382 eV at 600 °C. At high annealing temperature, the Co doped NiO thin films having a less disorder and fewer defects with minimum Urbach energy was 266 meV at 600 °C. The calculate refractive indices were found in qualitative agreement to the values derived from Reddy, Kumar and Ravindra models. P‒type semiconducting Co doped NiO thin films’ having a maximum value of the electrical conductivity was found at 580 °C. The annealing temperature at 580 °C the Co doped NiO thin films have a good crystallinity, optical and electrical conductivity.

Preparation and Characterizations of Monocrystalline Na Doped NiO Thin Films

In the present work, the effect of Na doping on optical, structural and electrical properties of Na doped NiO thin films were studied. The spray pneumatic method was used to deposit the Na doped NiO thin films in the range 0 to 5 wt.%, it are investigated at a substrate temperature of 420 °C with NiO solution 0.1 M. Firstly in the XRD specra, as found that a only (111) peak was observed for Na doped NiO thin film indicate that the Na doped NiO thin films a monocrystalline in nature with cubic structure. The maximum crystallite size of Na doped NiO thin films was 18.90 nm at 3 wt.%. Secondary, the optical transmissions spectra Na doped NiO thin films having a high transparency with comparing to undoped film in visible region. The band gap energy was decreased after doping by Na and reaching a minimum value is 3.53 eV at 2 wt.%. The minimum value of Urbach energy was 0.312 eV, it is obtained at 3 wt.%. In the end, the minimum electrical resistance of the Na doped NiO films was located at 5 wt.%. The optimum Na doping amount is achieved at 3 at %.