Ni-doped ZnO Thin Films Research Articles

Structural and optical properties of Ni-doped ZnO thin films as TCO material, fabricated by pulsed laser deposition method

Thin transparent layers of zinc oxide doped with nickel ions were obtained using the pulsed laser deposition method. The content of nickel ions in the initial solid solution was 1–10 %. The crystallographic structure was studied by X-ray diffraction. Measurements show that the fabricated layer crystallizes in the wurtzite phase and has a dominant orientation along the c-axis. The texture coefficient, grain size, and crystal lattice constants were calculated. The absorption coefficient of the layers was calculated from the transmission spectra of ultraviolet–visible light - near infrared. Photocurrent spectra were investigated. The composition of the layers significantly affects the optical constants. Ni-doped ZnO layers can find applications in optoelectronic devices.

Band gap tunability in DC sputtered Ni-doped ZnO thin films for wide usage in optoelectronic gadgets

ZnO thin films have brought significant applicability in optoelectronic and energy storage devices based on their environmental friendliness. Pristine ZnO, 6.25 % and 12.5 % Ni-doped ZnO thin films were deposited on Si substrate via direct current and radio frequency magnetrons, respectively. The X-ray diffraction patterns exhibited phase purity of synthesized thin films. The micrographs showed reduction in average grain size for pure ZnO, 6.25 % and 12.5 % Ni-doped ZnO as 95 nm, 70 nm and 60 nm, respectively. The elemental purity was confirmed by energy dispersive X-ray. The ellipsometric analysis showed that Ni inclusion brought band gap variation from 3.06 to 3.08 eV for pure ZnO to 12.5 % Ni-doped ZnO thin films. The real part of dielectric constant enhanced from 3.60 to 3.75 for 12.5 % Ni-doped ZnO, simultaneously depicting reduction in dielectric loss from 0.45 to 0.40. Conclusively, proposing Ni-doped ZnO thin films with low dielectric loss as a potential candidate in optoelectronic industry.

Band alignment studies of Zn1-xNixO/ZnO: As bilayer electron transport layer in perovskite solar cells

An efficient electron transport layer (ETL) is an essential requirement for performance and stability for perovskite solar cells. In this study, we have opted Zn1-xNixO/ZnO bilayer as is used electron transport layer instead of the ZnO single layer to overcome the trap-assisted recombination and also to enhance energy level alignment in the solar cell. For this, pristine ZnO and Ni-doped ZnO (Ni–ZnO) thin films were deposited on fused silica (Quartz) by pulsed laser deposition (PLD). For confirmation of the structural properties of deposited thin films, X-ray diffraction has been used. Electron affinity and band gap of these films have been evaluated by UPS and UV–Vis spectroscopy to design Zn1-xNixO/ZnO bilayer ETL. Further, planar perovskite solar cell has been schematized and simulated using SCAPS-1D software using experimentally designed bilayer ETL.

Evolution of structural phase transition from hexagonal wurtzite ZnO to cubic rocksalt NiO in Ni doped ZnO thin films and their electronic structures

This study thoroughly examines the collective influence of compositional variation and annealing temperature on the electronic structure of sol–gel derived NixZn1−xO (x = 0 to 1) thin films annealed at different temperatures (700 ° C, 800 ° C, and 900 ° C) using x-ray photoelectron spectroscopy (XPS) and x-ray absorption spectroscopy. A gradual structural phase transition from hexagonal wurtzite ZnO to cubic rocksalt NiO with increasing Ni concentration was revealed by x-ray diffraction (XRD). Grain growth was observed from scanning electron microscopy with increasing annealing temperature. Photoluminescence measurements indicate the presence of interstitial oxygen when Ni atoms are incorporated in the film. The Ni L 3,2 absorption edge shows an intensity enhancement in the white-line feature with increasing Ni concentration, evidencing the presence of higher oxidation states. Concurring results were observed by XPS where both Ni2+ and Ni3+ free ion multiplets are present in the Ni 2p core level spectrum for 20% and higher Ni concentration. O K and Zn L 3,2 XAS spectra demonstrated the e g-t 2g sub-band splitting at higher Ni concentration, triggered by band anti-crossing interaction and crystal field splitting. The extended x-ray absorption fine structure (EXAFS) simulation for the Zn K edge revealed a Zn–Zn/Ni bond length change for 60% Ni concentration. The thermal disorder factor increased up to 40% Ni concentration, and beyond that, it decreased due to stable NiO phase dominance in the alloy composite. Ni K edge EXAFS fitting indicated an insignificant change in the Ni-O and Ni–Ni/Zn bond lengths throughout the range of varying Ni concentrations. The thermal disorder factor increases with increasing annealing temperature, indicating a more disordered lattice. Such investigation is essential where the electronic properties of nanometer-sized materials determine the performance of functional devices. The present work critically elucidates the combined impact of compositional variations and annealing temperatures on electronic structures.

The role of Ni-Doped ZnO thin films on Methylene Blue (MB) photodegradation under visible irradiation

We report the effect of Ni-doped ZnO thin films on the photodegradation of methylene blue (MB) under visible irradiation. The Ni-doped ZnO thin films were deposited on a silicon substrate by ultrasonic spray pyrolysis (USP) at 450 °C for 15 minutes. The ZnO thin films are characterized by X-ray diffraction (XRD) and UV-Vis spectroscopy. The X-ray diffraction (XRD) pattern for all samples confirms that the crystalline phase of Ni-doped ZnO thin films is polycrystalline hexagonal wurtzite. However, due to the Ni incorporation into the ZnO site, there is a change in the crystal plane. All ZnO films confirmed photocatalytic properties, indicating methylene blue (MB) degradation under visible irradiation. Nevertheless, the degradation of the MB dye increased by about 76% with increasing Ni incorporation. Therefore, we confirmed that Ni incorporation affects the photocatalytic properties of the ZnO thin films.

Enhancement of UV detection properties of ZnO thin films via Ni doping

In this work, pure and Ni-doped ZnO thin films have been deposited onto glass substrates using the spray pyrolysis technique. All films were deposited at constant deposition parameters but the Ni content was changed from 0 to 7 weight (wt) %. XRD results revealed the formation of a hexagonal ZnO phase whilst no other phases were detected. The crystallite size was determined using Scherrer’s equation and found to be 45.9 nm for the pure film. Scanning electron microscope images show the formation of irregular grains with a broad size distribution. The existence of Ni in the deposited films was confirmed using energy dispersive spectroscopy (EDX), where the Ni content in the film increases as the weight % increases in the starting solution. The optical band gap was determined and found to be 3.3 eV for the pure ZnO films, which was reduced with Ni doping. The performance of the deposited films for UV radiation has been examined for the 365 nm wavelength and at different applied potentials and constant power. The rise and decay times for doped films were observed to exhibit faster rise/recovery as compared to pure films. The minimum response time was found to be 0.09 s for Ni-7 wt% film and the minimum decay time is 0.07 s for Ni-1 wt%.

Effect of Ni doping on structural, optical and gas sensing properties of ZnO films for the development of acetone sensor devices

The development of sensor materials for environmental air surveillance is very challenging. In order to meet the demand, the present study corelates the effect of nickel doping on structural, optical, morphological and gas sensing ability of zinc oxide thin films. The films were deposited on the glass substrates using spray pyrolysis technique. The crystalline character and morphological analysis of the films were characterized by X-ray diffraction (XRD) and Field emission scanning electron microscopy (FESEM). The hexagonal wurtzite structure of polycrystalline nature is observed from the XRD patterns. The preferred orientation is (101), however doping has significantly triggered (002) orientation. Systematic decrement in the lattice parameters and bond length have been observed which led to structural distortions as result of mismatch in ionic radii of dopant and host materials. FESEM analysis reveals that thin film samples exhibit nanoflake morphology. A well-defined morphology is observed with Ni doping. The compositional analysis (Energy dispersive X-ray spectroscopy) shows that the Ni content was increased with doping which confirm the successful Ni doping. Optical analysis of the samples was performed using UV–Vis spectroscopical analysis. Transmission spectra indicated the highest transmission value in the case of undoped ZnO samples (More than 80%). Gradually decreasing band gap values of ZnO films were observed with Ni doping. The sensor response was investigated for undoped and Ni doped ZnO samples at room temperature in the absence and presence of acetone with 50 ppm concentration. Optimum response (∼78%) is obtained for Ni doped ZnO (2% Ni) samples with response time of 33s. Spray synthesized 2% Ni doped ZnO thin film samples show promising approach to achieve high response at ambient temperature.

Structural, optical, and electronic studies of Ni doped ZnO thin films

The structural, optical, and electronic properties of Ni-doped ZnO (NZO) thin films were studied by X-ray diffraction (XRD), ultraviolet-visible transmittance spectroscopy (UV-Vis), atomic force microscopy (AFM), and Fourier transform infrared spectroscopy (FTIR). 0, 3, 5, and 7% NZO thin films were deposited on quartz substrate by pulsed laser deposition (PLD) technique at a substrate temperature of 300oC and oxygen partial pressure of 1 mTorr. XRD results show that all deposited films were crystalline and oriented along the (002) plane with wurtzite symmetry. All deposited films also show high transmittance in the UV-Visible regime (300-800 nm). Tauc formulation was used to calculate the bandgap. NZO thins films show a lesser bandgap as compared to pure ZnO films and further with Ni concentration the bandgap was reduced from 3.20 eV (3%) to 3.11 eV (7%). AFM results revealed the uniform deposition of NZO and ZnO films over a quartz substrate and FTIR analysis shows the shifting of the Zn-O-Zn band towards higher frequency numbers with Ni concentrations. Results obtained from this study indicate that as PLD grew NZO thin films can be a promising candidate for optoelectronic application. Keywords: ZnO, PLD, XRD, Ni, UV, NZO.

Structural, optical and magnetic properties of dilute magnetic semiconductor of Zn1-xNixO thin films for spintronic devices

Co-precipitation method is used to create various compositions of the bulk sample of Zn1- xNixO (x = 0, 0.02, 0.04, 0.06, 0.08, and 0.1). By using an electron beam approach, the required coatings were deposited onto extremely clean glass substrates. The current study examines the structural and optical, characteristics of Ni-doped ZnO thin films. The creation of the hexagonal wurtzite single phase of ZnO was revealed by X-ray diffraction, and it had a strong (002) peak with a peak shift towards a lower angle. It was discovered that the films' crystallite size shrank as the Ni content rose. Investigations were done into how Ni dopant affected the produced thin films' optical and magnetic properties. The optical energy gap decreases from 3.28 to 2.90eV with increasing Ni content. In addition, ferromagnetism increases with increasing Ni concentration at expense of Zn in Zn1-xNixO films . The changes in the optical and magnetic properties of the prepared films were discussed based on the structural modification, which, further, enhances upon Ni-doping

Enhanced and tunable femtosecond nonlinear optical properties of pure and nickel-doped zinc oxide films.

The nonlinear optical properties of pure ZnO and Ni-doped ZnO thin films are explored using the Z-scan technique at different input laser intensities and an excitation wavelength of 750 nm by 100 fs laser pulses. The pure ZnO and Ni-doped ZnO thin films were prepared by radio frequency magnetron sputtering at room temperature. A scanning electron microscope equipped with energy-dispersive x-ray spectroscopy was used to measure the thickness and composition of the thin films, while a UV-visible spectrophotometer was used to measure the linear optical properties. The structure of the thin films was measured using x-ray diffraction. Saturable absorption (SA) was observed in the pure ZnO thin film, while Ni-doped ZnO illustrated a combination of SA and reverse SA (RSA). The nonlinear absorption coefficient (β) and nonlinear refractive index (n2) of both pure ZnO and Ni-doped ZnO thin films were found to be input laser intensity dependent. As the input laser intensity increased, the nonlinear absorption coefficient and the nonlinear refractive index of both samples increased. An enhancement of two times in the nonlinear refractive index was observed for the Ni-doped ZnO thin film compared to the pure ZnO thin film. The optical limiting behavior of pure ZnO and Ni-doped ZnO thin films was investigated, and the data demonstrated that Ni-doped ZnO thin film is a good candidate for optical limiter applications due to the presence of strong RSA.

Synthesis and Characterization of Ni-Doped ZnO Thin Films Prepared by Sol–Gel Spin-Coating Method

Synthesis and Characterization of Ni-Doped ZnO Thin Films Prepared by Sol–Gel Spin-Coating Method

Microstructure and anti-corrosion properties of spray pyrolyzed Ni-doped ZnO thin films for multifunctional surface protection applications

The microstructures, electrochemical, and hardness properties of deposited Ni-doped ZnO thin films on ultrasonically cleaned 316L stainless steel (316L ST) employing a low-cost chemical spray pyrolysis technique (CSPT) was examined in this work. The films were prepared at various concentrations using commercially available purity zinc acetate and nickel acetate as the precursor sources. The result of x-ray diffractometry (XRD) showed that the films have polycrystalline structure with all the films consisting of single phase ZnO hexagonal wurtzite structure. Scanning electron microscopy (SEM) result affirmed that the coated films adhered to the substrates and equally spread through the substrate surfaces. The surface microstructure of the 316L ST improves with Ni content. The corrosion resistance of the 316L ST was observed to improve with the coated films. Hardness value of the uncoated 316L ST was observed to increase from 139.15 HV to 233.03 HV of coated S3 (9% nickel acetate (0.2 M) and 91% zinc acetate (0.2 M)).

Ni-Doped ZnO Thin Films: Deposition, Characterization and Photocatalytic Applications.

Root like structured Ni-doped zinc oxide [Zn(1-x)NixO (x = 0.09)] thin films were deposited on a non-conducting glass substrate by indigenously developed spray pyrolysis system at optimized substrate hotness of 573±5 K. Thus obtained Ni-doped ZnO thin films were characterized by UV-visible spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Atomic Force Microscopy (AFM). XRD result revealed that Ni-doped ZnO has a polycrystalline nature with a hexagonal wurtzite structure. For pure ZnO and Ni-doped ZnO thin films, the particle sizes were 60.9 and 53.3 nm while lattice strain values were 1.56×10-3 and 1.14×10-3, respectively. The film surface showed characteristic root-like structure as observed by the SEM. It was observed that the Ni-doped ZnO thin films were grown in high density along with more extent of branching as compared to pure ZnO thin films but retained the root-like morphologies, however, the branches were more-thinner and of shorter lengths. AFM analysis showed that the surface grains of the Ni-doped samples are homogeneous with less RMS roughness values compared with the undoped ZnO samples. The photocatalytic activity of the prepared thin films was evaluated by the degradation of methyl orange (MO) dye under UV light irradiation. Pure ZnO and Ni-doped ZnO thin films took 150 min and 100 min to degrade about 60% MO dye, respectively.

Multi-technique investigation of Ni-doped ZnO thin films on sapphire by metalorganic chemical vapor deposition

Optical and material properties of nickel-doped zinc oxide (ZnO-Ni) grown by metalorganic chemical vapor deposition with varying Ni source flow rates are investigated. ZnO-Ni showed a good crystal quality with (002) orientation but deteriorated at high Ni source flow rates. Photoluminescence responses show a reduction in the bandgap of ZnO-Ni with an increase in the Ni source flow and also with an increase in the temperature. Ni-doping can enhance luminescences at low concentrations (<25 SCCM and ∼2%) and suppress at high concentrations. Ni-related defects occur more toward the surface than bulk of the thin films. Longitudinal optical phonon replicas named 1LO and 2LO redshifts at low Ni source flow rates ≤100 SCCM with an increase in the temperature from 14 to 300 K, but exhibits an “S-shaped” red-blue-red shift with a dip at 50 K at higher Ni source flow rates (150 SCCM). Ni-doping also induces asymmetric crystal vibrations and rougher surfaces with the Ni incorporation. This study enhances the understanding of Ni-doped ZnO that is needed to apply transition-metal doped ZnO for various optoelectronic applications.

Structural and optical properties of ZnO and Ni:ZnO thin films: the trace of post-annealing

Nickel-doped zinc oxide thin films (Ni:ZnO) were deposited on quartz substrates by RF magnetron sputtering. The effect of annealing temperatures on the structural, morphological, and optical properties of the Ni:ZnO thin films were investigated. X-ray diffraction analysis revealed that the ZnO and the Ni:ZnO thin films were crystallized in wurtzite phase with the crystallites preferentially oriented towards the (002) direction parallel to the c-axis except for Ni:ZnO which annealed at 300 °C. Based on the optical transmittance measurements, the Ni-doped ZnO thin films were found to be almost transparent but darker than the ZnO thin films. The optical band-gap values of the Ni:ZnO thin films decreased from 3.30 to 3.20 eV, by increasing the annealing temperature. In addition, a linear relationship between the band-gap energy and tail width was determined.

Structural, raman, photo-luminescent and optical investigation of sol–gel derived Co, Al and Ni doped ZnO thin films

In this work, sol–gel spin coating route was utilized for the synthesis of undoped, Co-doped, Al-doped, and Ni-doped thin films of ZnO. XRD results show that deposited thin films possess a hexagonal lattice with preferential c-axis orientation. A reduction in lattice constants was observed owing to the substitution of Zn2+ ions by lower radius doping ions Co2+, Al3+, and Ni2+. The effect of doping is to reduce the crystallite size. Raman spectra show a characteristic peak of hexagonal ZnO at 439 cm−1. PL spectrum of all films demonstrates a UV emission ascribed to near band edge transition and a green emission band. All thin films with the transmission in visible regions above 86% are highly transparent. The doping element influenced the band gap of doped thin films.

Structural, morphological and transport properties of Ni doped ZnO thin films deposited by thermal co-evaporation method

Defects and doping play an important role in determine the physical and/or chemical properties of semiconductor materials. In this study, thermoelectric performance of nickel doped zinc oxide (Ni doped ZnO) was investigated in order to obtain the optimal defects concentration. The Ni doped ZnO thin films were prepared using thermal co-evaporation technique. It is observed that all the obtained samples exhibited preferential orientation along (002), the increases of Ni contents leads to crystallinity enhancement and lower surface roughness. The morphological, compositional and topological results of the Ni doped ZnO thin films indicate that the increases of Ni contents to 0.91% leads to low surface roughness (5.4 nm). The samples demonstrated an electrons concentration of 1.5 × 1019 cm−3, Seebeck coefficient at 178 μV∙K−1 and an electrical conductivity of 3175 S∙m with a maximum power factor of 101 μW∙m−1 K−2. The doping technique used in this work, showed promising results in producing high thermoelectric performance.

Significance of Ni doping on structure-morphology-photoluminescence, optical and photocatalytic activity of CBD grown ZnO nanowires for opto-photocatalyst applications

In this work, we study bare and Nickel (Ni) doped ZnO nanostructured thin films synthesized by the chemical bath approach. The as-prepared thin films were characterized extensively by XRD, SEM, PL, and UV–visible spectroscopy before and after Ni incorporation. Finally, the photocatalytic action of all catalysts was assessed using methylene blue (MB) dye degradation under the visible light irradiation. X-ray diffraction analysis approves wurtzite hexagonal structure with predominant orientation along (002) plane, and crystallite size was noticed to reduce from 34 to 32 nm by Ni-doping. The SEM images proved the formation of well-defined nanowire structures. Photoluminescence analysis confirmed the band-edge and defect-related emission peaks. The intensity of PL spectra ensured a decreased value after Ni-doping, suggesting delayed electron-hole pair recombination, which influences the decolorization activity. The 3 wt% Ni-doped ZnO thin film possessed the least optical bandgap value of 3.21 eV. It was observed that the Ni (3%) doped ZnO nanowires showed a significantly improved photocatalytic performance (96%) compared to the pure ZnO nanostructure (83%).

Influence of Ni-Doping in ZnO Thin Films Coated on Porous Silicon Substrates and ZnO|PS Based Hetero-Junction Diodes

Ni2+-doped ZnO thin films were prepared for various Ni concentration on the porous silicon substrates. The residual stress in the ZnO thin film is relaxed with increase in the concentration of Ni. FESEM images show the growth of pillar-like nanostructures over the entire porous silicon substrates. The variation of resistivity due to UV illumination was observed for the Ni-doped ZnO thin films. Ideality factor value is less for the ZnO:Ni|PS hetero-junction diode than ZnO|PS hetero-junction, Ni doping in ZnO improves the rectifying behavior.

Electrochemical Corrosion Behavior of Ni-doped ZnO Thin Film Coated on Low Carbon Steel Substrate in 3.5% NaCl Solution

Electrochemical Corrosion Behavior of Ni-doped ZnO Thin Film Coated on Low Carbon Steel Substrate in 3.5% NaCl Solution