Nanostructured Zinc Oxide Thin Films Research Articles

Synthesis and Characterization of Nanostructured Cerium-Doped Zinc Oxide Thin Films for Selective Nitrogen Dioxide Gas Sensing Applications

Zinc oxide thin films doped with cerium were synthesized through facile spray pyrolysis technique and subsequently characterized via an array of analytical methods, including X-ray diffraction, ultraviolet-visible diffused reflectance absorption spectroscopy, photoluminescence, scanning electron microscopy and energy-dispersive X-ray spectroscopy techniques. The operative mechanism of the semiconductor metal oxide gas sensors is predicated on the modulation of electrical conductivity in response to varying gaseous atmospheres, under the influence of disparate thermal conditions. The nitrogen dioxide gas-sensing performance of the films demonstrated a noteworthy gas response of 18% at an elevated temperature of 400°C for a concentration of 100 ppm, accompanied by rapid response and recovery times of 23 and 60 s, respectively.

Synthesis of Mn doped nanostructured zinc oxide thin films for H2 gas sensing

Thin films of zinc oxide and (ZnO:Mn) with 1% and 3% concentrations were created at 400 °C by spray pyrolysis. According to X-ray diffraction (XRD) investigation, ZnO films are polycrystalline and have a cubic structure with a distinct peak in one direction (101). The grain size increases as manganese content rise, from 12.66 nm to 14.66 nm. While the strain (ε) for ZnO reduced after manganese doping, it decreased from 27.36 to 23.63. Surface topography and nanostructure study reveal that as the manganese (Mn) content of ZnO films increased, cluster grain size, average roughness, and root mean square roughness (Rrms) all significantly reduced. SEM images show substantial morphological changes from flat islands to spherical nano-grains post-manganese via Mn content. The average transmittance was >70% in the visible area for Undoped ZnO and 1, 3% Manganese doping optical transmittance demonstrates exceptional optical transparency. When doping levels are increased by 1% or 3%, the absorption coefficient rises. The optical band gap widens in ZnO: Mn film for allowed direct transition has been decreased from (3.32 to 3.21) eV. Results illustrate that the films' refractive index and extinction coefficient decreases with increasing Mn Doped. Hydrogen gas decreases resistance in ZnO films, suggesting p-type behavior. Doping with 3% Mn increases resistance. Decreased sensitivity with higher Mn content after hydrogen gas exposure indicates increased electrical resistance in the film.

Effect of Picosecond Laser Irradiation on the Properties of Nanostructured Zinc Oxide Thin Films

In this article, a picosecond laser source was employed to irradiate the nanostructured ZnO thin film prepared by the sol-gel method. The impact of laser irradiation on the characteristics of a nanostructured ZnO thin film was investigated. Analysis using X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy confirmed a significant influence on the structure of the ZnO thin film. As the duration of laser irradiation (the number of laser pulses) increased, there was a remarkable decrease in both the electronic and photoluminescence intensities of the nanostructured film. Tauc's plot indicates a noticeable change in the optical band gaps of the thin film with the increase in irradiation time. The morphological image suggests that the laser irradiation energy induces both degradation and modification of the film surface, consequently causing changes in the structural, absorption, and photoluminescence properties of nanostructured ZnO. The observed effects are attributed to alterations in the crystal structure and size of the nanostructured ZnO film, as confirmed by XRD. The reduction in photoluminescence intensity observed over the laser irradiation times may be a result of potential degradation in the crystalline structure of the nanostructured ZnO film.

Modeling of gas sensor based on zinc oxide thin films by feedback loop using operational amplifier

Nanostructured Zincoxide thin-film is widely used as a sensing material because of its tunable surface microstructure and wide optical bandgap but synthesizing a film with desired value of resistance and reproducibility of film is challenging, particularly by chemical method. In this work, we showed how a ZnO film of arbitrary resistance can be used as a sensor without application of heat using operational amplifier. Zinc oxide thin film was synthesized by using the Sol-gel method (Spin coating) and was characterized by XRD and SEM which revealed wurtzite polycrystalline nature of Zinc oxide film with average grain size 17–25 nm. In this report, we designed a noble electronic circuit capable of detecting analyte gas molecule even if very small change in film resistance occurs due to the influence of gas molecule. In recently available sensors, the quality of the film degrades over time due to repeated heating and cooling, resulting in a reduced lifetime for the sensor. To address this issue and achieve higher sensitivity, as well as to fabricate an affordable, portable, precise, energy-efficient and durable device, this electronic model offers advantages over classical temperature-dependent sensors.

Influence of the Cadmium Sulfide Chemical Bath Deposition Temperature on Cadmium Sulfide/Zinc Oxide Thin Films

The spin-coating method has been employed for nanostructured crystalline zinc oxide (ZnO) thin film preparation on FTO glass substrates. Cadmium sulfide (CdS) layers were then deposited on the surface via the chemical bath deposition method. To investigate the effect of the formation of the CdS layer on ZnO/FTO, the deposition of these layers was performed at three different temperatures (40, 60, and 80 °C). The synthesized CdS/ZnO composite was found to have homogenously distributed crystalline grains of both ZnO and CdS. The uniform distribution of the grains and the equal molar ratio of the two components resulted in excellent optical and photocatalytic performance. Analysis of CdS/ZnO thin films was performed using XRD analysis, UV-vis spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and linear sweep voltammetry. The best optical, morphological, and electrical properties and the highest photocurrent value of the CdS/ZnO thin films were obtained when the CdS layers were formed at 60 °C. X-ray diffraction characterization revealed that CdS/ZnO thin films crystallized into hexagonal wurtzite ZnO and cubic CdS. The crystallite size of ZnO and CdS/ZnO was ~38 nm and ~19 nm, respectively. The band gap calculated for CdS/ZnO, formed at different temperatures, varies from 2.05 to 2.15 eV.

Photocatalytic activity in nanostructured zinc oxide thin films doped with metallic copper

Nanostructured zinc oxide (ZnO) thin films doped with metallic copper were synthesized by a sputtering process. As the copper sputtering power increased from 20 to 40 W, the copper content increased from 2.37% to 14.15%. The film thickness increased from 166 nm (ZnO) to 387 nm (14.15Cu–ZnO). The crystallite size on plane (002) of ZnO films was 7.95 nm and increased to 17.82 nm at 14.15 Cu–ZnO films. Spherical particles were observed, and the surface roughness increased from 2.77 nm (ZnO) to 5.35 nm (14.15 Cu–ZnO). The intercalation of metallic copper in the ZnO lattice decreased the optical transmittance and photoluminescence (PL) intensities and shifted the absorption edge towards higher photon wavelengths. Methyl green dye (MG) was used as a pollutant in wastewater to examine the photocatalytic activity of the films. The degradation ratio of MG dye in ZnO thin films was 60%, reaching 99.8% at 14.15 Cu–ZnO thin films.

Thin Film Photodetectors Based on Zinc Oxide Nanoinks

Zinc oxide (ZnO) has many useful properties for electronics and optoelectronics including wide band gap, large exciton binding energy, low-cost, ease of processing and availability [1]. This has led to increased interest and development of thin film electronics, transparent conductors, solar cells, light-emitting diodes, lasers, photodetectors and various sensors based on ZnO materials [2, 3]. The high surface areas and tunable properties of ZnO nanostructures make them particularly suitable for applications such as sensing and photonic devices [4, 5].In this work, we present results on nanostructured ZnO thin film photodetectors fabricated using nanoparticle inks (nanoinks) obtained via planetary ball milling (PBM) of bulk powders. PBM [6] is an emerging solution-based nanofabrication approach that can quickly produce nanoink suspensions at low-cost by nanoscale grinding, without complex processing and suitable for thin film coating of various materials on different substrates [7]. The thin film photodetector devices were fabricated by depositing PBM ZnO nanoink onto flat insulating glass substrates followed by contact formation as shown schematically in Fig. 1a: PBM was performed using ZnO powder in ethylene glycol (EG) or deionized (DI) water solvent (a.k.a. colloidal grinding) with zirconia grinding beads. The grinding speed and time were varied between 200 and 1000 rpm and 10 min. and 60 min., respectively. A few μL of the resulting ZnO nanoink was used to coat the substrate surface and dried at ~ 100 °C. Lastly, two electrical contacts to the resulting films were made using silver paint and copper tape. Analysis of ZnO films after deposition showed they consist of nanostructured particles with sizes reaching below 100 nm, as displayed in the scanning electron microscopy (SEM) and atomic force microscopy (AFM) images in Fig. 1b, depending on grinding conditions (speed, time).The optical properties of the ZnO thin films were evaluated via photoluminescence measurements (Fig. 1c), which, in addition to interband transitions in the UV, displayed longer wavelength emission peaks due to surface and bulk defect states. Such deep level states are dependent on grinding parameters and thus allow the accessible spectrum for the nanostructured ZnO films to be extended into the visible region in a tunable manner. Two-terminal photoconductance data of the ZnO PBM nanoink thin film devices were obtained using a probe station and precision source-measure unit, with and without illumination, under ambient atmosphere and at room temperature. Fig. 1d shows current vs. voltage curves obtained for a typical photodetector device, which display current increasing proportional to incident light intensity. This behavior can be explained by electron-hole pair creation and desorption of surface oxygen species (leading to vacancies that act as donors) upon photon absorption, which leads to an increase in conductance. This is consistent with previous studies where ZnO thin films have been used for photoconductive sensor applications, validating PBM nanoink as a suitable synthesis technique for the active material in photodetectors.Compared to standard ZnO thin films, the PBM nanoink method allows both particle dimensions and surface states to be tailored and optimized for different photodetector applications in a straightforward manner by adjusting grinding conditions. In particular, both UV and visible light detection can be tuned via the solution-based ZnO nanoink approach presented without additional material/chemical processing. Such PBM nanoinks thus offer the potential of realizing low-cost photodetectors and multifunctional thin film coatings for applications in optoelectronics, imaging, environmental monitoring and communications.

Successive Ion Layer Adsorption and Reaction Method Developed ZnO Thin Films for NO2 Gas Sensing

The present investigation deals with the NO2 gas detection via nanostructured zinc oxide (ZnO) thin films harvested over a glass substrate via a simple and facile successive ion layer adsorption and reaction (SILAR) approach. ZnO nanostructured thin films are developed by different SILAR cycles (ZnO:15, ZnO:30, ZnO:45, ZnO:60). The physicochemical, optical, and morphological properties of prepared thin films are explored by various characterization techniques. The phase purity and grains size are confirmed by X‐ray diffraction (XRD) and Scherrer formula, which reveal the hexagonal phase structure with variant grain size (≈16–21 nm). The surface morphology of deposited films shows the well‐dispersion of ZnO nanoparticles, which is picturized by field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), attenuated total reflectance (ATR). UV–Vis and FTIR spectroscopy elaborates on the optical properties and functional groups of ZnO films, respectively. Further, the sensing ability of ZnO thin films is studied with different concentrations (50–250 ppm) of NO2 gas in the span of 50 ppm by recording the resistance transient. The ZnO:30 thin‐film displays an enhanced gas sensing response of 1.42 GΩ at 100 °C compared to other synthesized films and at different temperature ranges. The ZnO:30 film shows the highly selective response toward the NO2 gas compared to other interference gas species. Thus, the present study highly recommends the investigated method for the ZnO thin film formation to be employed toward NO2 gas sensing.

Growth of Aluminum Doped Zinc Oxide Nanostructure Thin Films by Nonconventional Sol‐Gel Method

AbstractThe present work demonstrates the growth of undoped and Al doped ZnO (AZO) thin films by using nonconventional sol‐gel method. The structural, morphological, optical, and electrical properties of obtained thin films are studied. X‐ray diffraction (XRD) analysis confirms hexagonal wurtzite structures for both undoped and doped thin films. The crystallite size is found between 15 and 30 nm. Scanning electron microscope (SEM) images show that the films have approximately uniform morphologies, consisting in several flower‐like aggregates with nanosized multipetals. From the optical properties, it is found that with the increase in the doping concentration, there is a decrease in the absorption coefficient in the visible wavelength range. It is also noticed that the increase in doping concentration causes an increase in bandgap (Eg) and a decrease in extinction coefficient. Urbach energy decreases with increase in the doping concentration. In the Hall effect study, it is observed that the conductivity and carrier concentration increase sharply with increasing the aluminum quantity. The causes and significance of these observations are discussed.

Flexible thermoelectric and photosensitive thin-film material based on nanostructured ZnO:In layer covered by nanocellulose

In this study, to create new flexible thermoelectric and photosensitive thin-film material for in-plane thermoelectric generator (TEG) and broadband photodetector (PD) we deposited nanostructured indium-doped zinc oxide (ZnO:In) thin films on polyimide (PI) substrates by using the inexpensive and scalable method Successive Ionic Layer Adsorption and Reaction (SILAR). To reduce the resistivity of the ZnO:In film in the ZnO:In/PI composition to about 0.02 Ω∙m, it was annealed in a vacuum at 300 °C. To protect ZnO:In from the influence of gases and environmental moisture, the composition ZnO:In/PI was coated with nanocellulose (NC) manufactured by TEMPO-mediated oxidation of cheap and abundant herbaceous plant. An analysis of the surface morphology using scanning electron microscopy (SEM) using secondary electron (SE) and backscattered electron (BSE) images combined with energy dispersive X-ray spectrometry (EDS) made it possible to select the optimal mode for the formation of a continuous nanocellulose coating in the prepared in this way NC/ZnO:In/PI sample. By using ZnO:In/PI and NC/ZnO:In/PI test samples with ohmic aluminum contacts we determined output thermoelectric characteristics and time-dependent photoresponses depending on the illumination wavelength λ, bias voltage U and irradiance intensity Pλ. It has been experimentally established that both samples are suitable for use as broadband photodetectors. Their spectral responsivity Rλ data are from 2 to 0.1 A/W in the UV–visible-NIR detection range. The external quantum efficiencies (EQEs) for UV and blue light are especially high, at the level of hundreds of percent. But even under red and NIR illuminations, the obtained ZnO:In/PI and NC/ZnO:In/PI test samples demonstrate Rλ and EQE values, which exceed those of modern photodetectors based on zinc oxide and its composites. The specific detectivity D* is in the level of 1010-1012 Jones (cm∙s−1/2∙W−1) for all U, λ and Pλ, which is similar to D* values obtained for the known broadband photodetectors based on ZnO-contained compositions.

Green and cost-effective synthesis of zinc oxide thin films by L-ascorbic acid (AA) and their potential for electronics and antibacterial applications

The evolution of eco-friendly, green route and cheap technology for synthesizing nanostructured zinc oxide (ZnO) thin films using plant extracts is a promising choice because such materials present a widespread potential for numerous technological applications. This study proposes the green and cost-effective technique to synthesize stable ZnO thin films using a good reducing agent and facilitating many natural L-ascorbic acids (AA) metabolic reactions capacity. The influence of AA concentrations in the starting bath solution on ZnO samples' structural, morphological, electrical and antibacterial performances has been reported in detail. The main physical characteristics of the ZnO materials were improved by supplementing of reducing and capping agents AA. Average particle size varies with the adding AA from 58.29 to 48.68 nm and also thickness of these films was decreased from 0.82 to 0.44 μm. Also, it was seen that, the presence of AA in the bath solution significantly affected the absorption process and causes a morphological alteration due to the reaction between Zn2+ and AA during the deposition process. FTIR transmittance spectra of bare ZnO presented that a transmittance peak about 886 cm−1 and 748 cm−1 was created by the characteristic stretching vibration mode of the Zn–O. The resistivity of the produced films significantly changed with AA concentration in the bath solution. Antibacterial potentials of bare ZnO and ascorbic acid added ZnO films were examined against economically important Staphylococcus aureus (ATCC 25923) gram-positive bacteria and Escherichia coli (ATCC 35218) gram-negative bacterial disease agents via handling paper disc diffusion assay. The obtained diameter of the zones of inhibition was 20.1 mm for E. coli and 28.1 mm for S. aureus at the dose of ZnO+AA 8.0%. These inhibition diameters were larger than the diameter of ampicillin as our positive control alone. This proves that the newly synthesized compound is a powerful antibacterial agent.

Structural and Optical Characterization of Chemically Synthesized Nanostructured Zinc Oxide Thin Film

Zinc Oxide (ZnO) thin film has been synthesized using the chemical spray pyrolysis technique and ethylene glycolhas been used as solvent during the synthesis. X-ray diffraction (XRD) results show cubic and tetragonal phasesof ZnO and the grain size was calculated to be 2.57nm. Optical characterization reveals very high transmittancewithin the visible-ultraviolet region and a bandgap of 3.49 eV was obtained for ZnO thin film. Scanning ElectronMicroscopic (SEM) analysis showed a void-free non-homogenous surface.Keywords: ZnO; Spray pyrolysis; Ethylene glycol; Grain size.

Large Surface Nanostructured Zinc Oxide Thin Film Phosphor Fabrication on Different Conductive Substrates

Large Surface Nanostructured Zinc Oxide Thin Film Phosphor Fabrication on Different Conductive Substrates

Towards the development of a gas micro-sensor based on nano-structured zinc oxide thin film for ethanol gas detection

In this paper, we present the results of our work on the development and characterization of nano-structured Zinc Oxide (ZnO) thin films successfully grown via a simple SILAR process. The deposition is carried out on a ceramic micro-sensor at room temperature. The deposited film was annealed at 400 °C for 1 h in an oxygen atmosphere.X-ray diffraction (XRD) and scanning electron microscopy (SEM) characterizations show that the film completely covers the substrate and exhibits a hexagonal Wurtzite structure. The effect of the film growth conditions on the film morphology and structure was assessed. The bandgap values of the different films grown on glass substrates were also studied by means of UV–Vis spectroscopy, and it was found that the bandgap value varies from 3.2 to 3.8 eV depending on the growth conditions. The sensor response behavior against ethanol vapor was investigated under thermo-activation at 300 °C.

Efficacy of Ion Implantation in Zinc Oxide for Optoelectronic Applications: A Review

Unlike the majority of the silicon-based electronic devices, optoelectronic devices are predominantly made using III–V and II–VI semiconductor compounds and their alloys because of their direct bandgap. Among these, zinc oxide (ZnO) is a multifunctional wide bandgap II–VI semiconductor material that has distinctive properties, such as large excitonic binding energy, high-sensitivity, nontoxicity, and good compatibility, which favors it to be considered for various optoelectronic applications including photoelectrochemical (PEC) water splitting, light-emitting diodes (LEDs), photovoltaics, and photodetectors. Though the research concentrated on ZnO started many decades ago, the renewed interest is rekindled only with the availability of high-quality single-crystal substrates, easy growth techniques of various nanostructures, and reports on p-type ZnO. Therefore, ZnO is being treated as a concentrated research focus during the last two decades by researchers encompassing a vast field starting from luminescent materials, energy storage and conversion, to biomedical sensors, and so on. Ion beam irradiation is a fruitful approach to modify the properties of semiconducting oxides by introducing not only impurities but also defects, strains, structural transitions, and others. The necessity of a timely in-depth and critical review of the progress on ion implantation in ZnO is the origin of this Review, which focuses on the recent implantation efforts in nanostructured ZnO thin films as well as single crystals. In the beginning, with an introduction to the general principles of ion implantation, this Review presents interactions and distribution of implantation-induced defects in ZnO. Next, comprehensive analyses on the influence of ion implantation on the optical, electrical properties, and optoelectronic applications including PEC water splitting and LEDs have been revealed. Most importantly, in each section from a “state-of-the-art” of the domain, some critical connections have been provided between the results of the theoretical simulations of the implanted ion-induced defects and the reported data, which in particular would be able to offer significant insights for both theoretical and experimental research community working with the oxide semiconductors. At the end, a summary with future directions for utilizing ion implantation for achieving ZnO thin-film-based high-performance devices has been presented. By including a sufficient breadth and depth of literature coverage in this Review, we believe that it would also tend to reveal the inconsistencies in the extant body of research.

Effect of Oxygen Flow Rate on the Characteristics of RF Sputtered ZnO Thin Films

Zinc Oxide (ZnO) thin films were deposited on glass substrate by radio frequency (RF)reactive magnetron sputtering technique at variable Oxygen flow rates while Argon flow rates waskept constant. The effect of oxygen flow rate on structural, electrical, optical properties of nanostructured ZnO thin films were investigated by X-ray diffractometer, scanning eletron microscopy(SEM), Hall effect measurements and UV-Visible spectrophotometer. X-ray diffraction (XRD) datareveals films are polycrystalline hexagonal structure with (002) peak as a preferred orientation andcrystallite size was found to be in range12 nm-16 nm.The electrical resistivity of films decreasesfrom 10-1 Ω-cm to 10-2 Ω-cm. All deposited ZnO thin films shows high transmittance above 95% inthe visible range 360 nm-800 nm. The optical band gap and refractive indices have been calculatedusing UV-Vis transmission spectra. Oxygen gas flow rates found to have large impact onoptoelectronic properties of ZnO films.

The role of process temperature on structural, optical, vibrational and electronic environments of thermal chemical vapor-deposited copper-doped zinc oxide nanostructured thin films

Copper incorporated zinc oxide (Cu–ZnO) nanostructure thin films were deposited by using a high-temperature chemical vapor deposition technique at 650–800 °C with Cu and Zn powder in O2 and N2 gas atmosphere. The Cu–ZnO thin films were characterized by AFM, XRD, FTIR, Raman spectroscopy, UV–Vis spectroscopy, and XPS to investigate the structural, vibrational, optical, and electronic environments of Cu–ZnO thin films. The AFM study revealed that nanoparticles of Cu–ZnO films are varied from 225 to 74 nm with increasing process temperature from 650 to 800 °C. The relative intensity of E2(high) phonon increases with increase in the process temperature 650–800 °C. The photoluminescence spectra of Cu-doped ZnO films showed a strong orange emission peak centered at 635.12 nm and 700.06 nm due to bound excitation and intrinsic defects, respectively. The Tauc optical bandgap of Cu–ZnO thin films decreased from 2.72 to 2.22 eV, due to the increase with an increase in copper doping concentration. Moreover, the semiempirical electronic environments of Zn 2p3/2, O(1 s), and Cu (2p) core orbital are analyzed by the Origin software.

Structural and chemical network studies of thermal chemical vapour deposited ZnO nanostructured thin films

In this work, we have investigated the role of process temperature on microstructural, structural, vibrational and phonon behaviour of Zinc Oxide Nanostructured (ZnO-NS) thin films deposited via thermal chemical vapour deposition reactor (TCVD) on Si substrate. The various spectroscopic methods such as Atomic Force Microscopy (AFM), X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR) and Raman Spectroscopy were used to evaluate its morphology, structural, vibrational and phononic behaviour. We have observed that the change in process temperature considerably modifies the inherent material properties of ZnO-NS thin films. The AFM result revealed that the density distribution of agglomerated ZnO-nanograins increases with increasing process temperature from 650° C to 750° C. XRD result revealed that the average crystallites size of ZnO-NS thin films was decreased from 22.35 to 12.47 nm with increasing process temperature. The lattice strain and stress in ZnO-NS thin films decrease with increasing process temperature. The FTIR spectra revealed the decreasing intensity of ZnO stretch with increasing process temperature indicates a change in defect distribution of nanostructure at the higher temperature. The Zn-O–H bond shows asymmetry towards the lower wavenumber region can be attributed to the presence of another chemical compound with similar bonding strength overlap with each other. The Raman spectrum confirmed that the FWHM of E1(TO), E2(high), A1(LO) and E1(LO) phonon were increased whereas FWHM of A1(TO) and SO phonon decreased with increasing process temperature. The phonon lifetime of various phonons was calculated using energy-time uncertainty relation and found that the phonon lifetime of E1(TO), E2(high), A1(LO) and E1(LO) phonon decreased with increasing process temperature.

Annealing Effect on Microstructure and ElectricalCharacteristics of n-ZnO/p-Si HetrojunctionDiode Fabricated by RF Sputtering Process

This article reports fabrication and microstructural characterization ofn-ZnO/p-Si heterojunction diode. Nanostructured Zinc Oxide (ZnO) thinfilm was deposited on p-type silicon (Si) and glass substrates using RFsputtering process for fabricating n-ZnO/p-Si heterojunction diode. Theeffect of annealing temperature on the structural and morphologicalproperties of ZnO thin films has been observed. After deposition,these films are annealed. Structural properties, surface morphologyand quality of thin film have been studied using XRD, AFM, FE-SEMand Energy Dispersive X-ray Spectroscope (EDX) measurements. XRDresults confirms the formation of ZnO. The crystallite size of ZnO filmswas increased by annealing it at 523 K. The average crystallite size ofas deposited nanostructured ZnO thin film was found to be 28 nm.The junction properties of n-ZnO/p-Si heterojunction diodes wereinvestigated using current–voltage measurements. The current wereanalyzed by sweeping the voltage from -6V to +6V and and the kneevoltage was found to be around 1.9V.

Investigation of aluminum doping on structural and optical characteristics of sol–gel assisted spin-coated nano-structured zinc oxide thin films

In this research, Al-doped (with 2, 4, 6, and 8 mol%) zinc oxide thin films deposited onto glass substrates using wet chemical spin coating technique were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and UV–Vis spectroscopic methods to realize the doping effect of Al on structural and optical properties of ZnO thin films. XRD analysis revealed that the Al-doped ZnO (AZO) thin films were polycrystalline in nature with hexagonal lattice structure, and crystallite growth along c-axis. SEM images on the film surface at lower Al content exhibited granular nanostructures. At higher Al content, the nanostructural features of ZnO thin films was observed to be diminished. The compositional analysis via EDS measurements indicated the presence of zinc, oxygen, and aluminium into the AZO thin films. AZO thin film containing 2 mol% Al exhibited higher transmittance of 97% and absorption edge at 385 nm in the visible region. Optical bandgaps of AZO thin films were varied within 3.30–3.37 eV. Noticeable variations on structural features, and optical parameters of AZO thin films were detected, and the changing trend showed was non-linear and non-monotonic in nature.