Deposited ZnO Thin Films Research Articles

The evolution of morphology and structure of spin-coated Zinc Acetate thin films and their impact on ZnO film morphology

The deposition of ZnO thin films using sol-gel technology is a straight forward and widely used method for fabricating ZnO films with diverse morphologies and tunable electrical and optical properties. Notably, the preparation of ZnO compact layers from a zinc acetate and monoethanolamine (ZA:MEA) solution via spin-coating has gained popularity due to its simplicity. The pretreatment of spin-coated ZA:MEA films significantly impacts the morphology and structure of the resulting ZnO films. While the effects of preheating and its rate on ZnO precursor films have been extensively studied, the morphological and structural evolution of ZA:MEA films immediately after spin-coating and its subsequent impact on the final ZnO film have not been previously explored. In this study, we present the topography and phase composition of as-grown ZA:MEA films using atomic force microscopy (AFM). We conduct an in-situ investigation of the morphological evolution of ZA:MEA films. Our results reveal that as-grown ZA:MEA films possess an inhomogeneous structure. AFM phase image shows two distinct domains in the ZA:MEA films. Over time, we observe the growth of crystals in both vertical and perpendicular directions. ZA:MEA film aged for at least 20 h develops arrays of vertically oriented crystals throughout the film covered with sheet-like crystals forming on the film surface. This temporal evolution in the morphology and structure of ZA:MEA films significantly influences the morphology of the final ZnO film.

Nanostructured ZnO thin film to enhance gutta-percha’s adhesion to endodontic sealers

BackgroundGutta-percha (GP) combined with an endodontic sealer is still the core material most widely used for tridimensional obturation. The sealer acts as a bonding agent between the GP and the root dentinal walls. However, one of the main drawbacks of GP core material is the lack of adhesiveness to the sealer. ZnO thin films have many remarkable features due to their considerable bond strength, good optical quality, and excellent piezoelectric, antibacterial, and antifungal properties, offering many potential applications in various fields. This study aimed to explore the influence of GP surface’s functionalization with a nanostructured ZnO thin film on its adhesiveness to endodontic sealers.MethodsConventional GP samples were divided randomly into three groups: (a) Untreated GP (control); (b) GP treated with argon plasma (PT); (c) Functionalized GP (PT followed by ZnO thin film deposition). GP’s surface functionalization encompassed a multi-step process. First, a low-pressure argon PT was applied to modify the GP surface, followed by a ZnO thin film deposition via magnetron sputtering. The surface morphology was assessed using SEM and water contact angle analysis. Further comprehensive testing included tensile bond strength assessment evaluating Endoresin and AH Plus Bioceramic sealers’ adhesion to GP. ANOVA procedures were used for data statistical analysis.ResultsThe ZnO thin film reproduced the underlying surface topography produced by PT. ZnO thin film deposition decreased the water contact angle compared to the control (p < 0.001). Endoresin showed a statistically higher mean bond strength value than AH Plus Bioceramic (p < 0.001). There was a statistically significant difference between the control and the ZnO-functionalized GP (p = 0.006), with the latter presenting the highest mean bond strength value.ConclusionsThe deposition of a nanostructured ZnO thin film on GP surface induced a shift towards hydrophilicity and an increased GP’s adhesion to Endoresin and AH Bioceramic sealers.

Effect of deposition time on properties of the ZnO by USD Method

This investigation aims to improve the properties of 304 L stainless steel (SS) substrates for use in corrosion, mechanical, and biomedical applications by depositing ZnO thin films. The ultrasonic spraying technique was used to prepare ZnO thin films with depositional times of 1, 4, and 9 minutes. XRD and Raman studied the surface characteristics of ZnO samples. XRD analysis revealed a hexagonal structure with an average crystallite size of 22 nm for ZnO. Indentation nano measurements indicated an increase in the hardness of the films examined. To determine the type of conductivity and estimate the charge carrier density, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and Mott-Schottky analysis were performed. The thin film deposited for 9 minutes was found to be the most effective in improving corrosion resistance.

Sputtering Deposition of ZnO Thin Films for Photocatalytic Hydrogen Production: Perspectives on Upscaling

This study presents the successful implementation of ZnO thin films (denoted as z01, z02, and z03) through magnetron sputtering in the photocatalytic production of hydrogen using a low-intensity UV source (3 mW cm−2). The one-step synthesis process demonstrates simplicity and scalability. The deposited coatings, with thicknesses ranging from 62 to 209 nm, exhibit a hexagonal crystalline structure and display visible luminescence in the yellow-red range, attributed to point defects in the ZnO lattice. Among the samples, z03 (62 nm in thickness) exhibited the most promising performance in photocatalytic hydrogen production, achieving a rate of (5387.2 ± 151.6) µmol g⁻¹ h⁻¹ when utilizing methanol as a hole scavenger. These findings hold great potential for upscaling such coatings in energy harvesting applications. The present work opens new avenues for efficient and scalable hydrogen production, contributing to improving clean energy technologies.

Deposition of ZnO thin films with different powers using RF magnetron sputtering method: Structural, electrical and optical study

Zinc Oxide thin films at room temperature with good crystallinity quality have been deposited at different Radio Frequency powers. Magnetron sputtering technique has been carried out on glass and oriented Si(100) substrates. The film structure has been characterized by X-ray Diffraction (XRD) and MicroRaman spectroscopy, which possesses a wurtzite structure with (002) preferential orientation selecting suitable conditions. Scanning electron microscope (SEM) and atomic force microscopy (AFM) have been utilized to determine the films surface morphology. The stoichiometry has been verified by Energy dispersive X-ray spectroscopy (EDX) analysis. The optical behaviors of the deposited films have been characterized by Ultraviolet Visible (UV-Vis) (optical transmittance measurements) as well as by Photoluminance characterization. Electrical properties, Current-Voltage (I-V) and Capacitance-Voltage (C-V) have been studied in details for Zinc Oxide on Silicon film that deposited at different Radio Frequency power. The high transparency, electrical behavior and smooth surface allow to use these Zinc Oxide films in photovoltaic cells and optoelectronics application.

Safeguarding Cork’s Beauty and Longevity: Innovations in Deposition of Protective Thin Films

Cork is a sustainable natural material widely used as a wine stopper. However, some other uses, such as wall coverings, flooring, bags and shoes, face UV damage. To mitigate this issue, we explored the deposition of TiO2 and ZnO thin films via magnetron sputtering on glass and cork substrates. Both films displayed uniformity and the lack of any discernible cracks or voids, remained transparent in the visible region, and offered UV protection. Thus, TiO2 and ZnO blocked UV light with a wavelength of up to 310 nm (Eg = 4 eV) and 370 nm (Eg = 3.3 eV), respectively. Exposure tests, under a sun simulator lamp, revealed that the uncoated cork showed noticeable color changes, even when located under a glass substrate. The TiO2 coating did not prevent cork discoloration, while ZnO prevented it. This study highlights ZnO thin films as a durable solution to safeguard cork materials from UV damage and extend their usability.

Photovoltaic ZnO/SnSx heterostructures obtained by “electrochemical deposition-successive ionic layer adsorption and reaction” approach

In this work, ZnO/SnS/indium tin oxide (ITO)/glass functional heterostructures have been developed using a combined approach of electrodeposition of a SnSx layer and successive ionic layer adsorption and reaction (SILAR) of the ZnO layer. The high-quality 400 nm-thick orthorhombic SnS0.9–0.95 films were formed on the ITO substrates with a thickness of 130 nm and an electrical conductivity of less than 40 Ω/□. Chemical deposition of ZnO thin films by the SILAR method allowed to deposit hexagonal films with a thickness of about 200 nm. The morphology, elemental and phase composition of the films were characterized by Scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The band gap (1.4 eV for SnSx and 3.3 eV for ZnO), as well as the high light absorption coefficient of SnSx films (1–2) × 104 cm–1 were determined. The obtained ZnO/SnSx/ITO heterostructures formed by the electrodeposition–SILAR cycle showed a photoEMF value of 198 mV. These properties make ZnO/SnS heterostructure promising for low-cost solar cells based on affordable materials.

Sol–gel deposition of Al-doped ZnO thin films: effect of additional zinc supply

Sol–gel deposition of Al-doped ZnO thin films: effect of additional zinc supply

Exploring the effects of substrate and substrate temperature on the properties of radio frequency magnetron sputtered ZnO thin films

The physical and optical properties of zinc oxide thin films strongly depend on the film deposition techniques. In this work, RF magnetron sputtering was used to deposit ZnO thin films on various substrates (glass, quartz, ITO-coated glass, FTO-coated glass, Si(100), Si(100)/ SiO2) to study the role of substrate and substrate temperature on the morphological, structural and optical properties of the film grown. A detailed discussion on various aspects like surface morphology, strain, photoluminescence, bandgap, surface roughness, and material composition has been done. Compressive stress was present in the films created at room temperature and differed for various substrates based on the lattice mismatch. The nature and temperature of the substrate are found to affect the surface topography of films. Substrate and substrate temperature influenced the emission characteristics of ZnO thin films. In oxygen-rich substrates, defect emissions differed. We found that quartz is a better substrate to fabricate ZnO at room temperature and both Si and Si/SiO2 are preferable at high temperatures due to the lower lattice mismatch and thermal expansion coefficient. Comparing the electrical characteristics of ZnO thin films grown on glass and quartz substrates, ZnO on glass exhibited lower resistivity and higher carrier concentration. The Triboelectric nanogenerator (TENG) combining ZnO and PDMS, was developed to operate in vertical contact-separation mode. The obtained open circuit voltage was 30 V and 33 V for ZnO grown over ITO and FTO respectively, and the slight increase is due to the rougher film's surface on FTO than ITO. The selection of substrate is crucial in many applications and our findings provide an overview of the suitability of substrate and substrate temperature for the fabrication of ZnO thin film-based optoelectronic devices.

Tuning the texture and polarity of ZnO thin films deposited by spatial atomic layer deposition through the addition of a volatile shape-directing agent

Many functional devices are nowadays based on thin films deposited by physical or chemical vapour deposition methods. Being able to control the texture of the films is very important to tune their functional properties. Texture is commonly tuned by either using single crystalline substrates or seed layers, or by modifying the deposition parameters (gas flows, precursor concentration, temperature, etc.). In this study a volatile shape-directing agent (VSDA), namely 4-(5)-Methylimidazole (4-(5)-MeIM), is used during the deposition of ZnO thin films by Atmospheric-Pressure Spatial Atomic Layer Deposition (AP-SALD) to control the texture and growth rate of the films. In particular, ZnO thin films can be grown preferentially along [001], resulting in an enhanced piezoelectric coefficient. In addition, the polarity of the ZnO films also depends on the amount of VSDA used. An innovative industry-compatible approach to control texture and polarity of ZnO thin films is presented, having a clear potential for other functional materials and applications.

Effect of Au Doping on ZnO Nanoporous Structure for H2S Gas Sensing

This research mainly constitutes the fabrication of semiconductor gas sensors using high Power pulse magnetron sputtering (HiPIMS) technology to deposit ZnO thin films. As a doping substance, different thicknesses of gold plating is deposited on the surface of ZnO thin films. Various thicknesses of gold used in the study are 3.3 nm, 6.6 nm, 10 nm, 13.3 nm and 16.6 nm. The structural properties of thin films were identified by X-ray- diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS). EDS analysis conveyed that gold particles filled the pores of nanoporous ZnO structures, which increased the films surface area and enhancing the gas sensing response. Various concentrations of H2S gas is used to test the gas sensing properties and the results proved the Au doped ZnO thin film sensor has enhanced sensing than the pure ZnO thin film sensor. 10 nm thickness doped Au has prime sensing properties with the operating temperature of 300 °C. Other sensing properties such as repeatability, selectivity and effect of humidity are tested and presented the data which shows the Au doping ZnO superiority over pure ZnO thin films.

The effect of thickness on structural, optical, and electrical properties deposited ZnO thin films by PLD

In this paper, the effect of film thickness on structural, electrical, and optical properties of ZnO thin films deposited by Pulsed laser Deposition (PLD) over a quartz substrate has been studied. In PLD the thickness of the deposited thin films varies from 200 nm to 300 nm by increasing the number of laser shots from 9000 shots to 12,000 shots respectively. Deposited thin films were studied by Grazing angle X-ray diffraction (Gi-XRD), Ultraviolet–Visible transmittance spectroscopy (UV–Vis), Lateral I-V measurements, Field emission scanning electron spectroscopy (FESEM), and energy dispersive X-ray spectroscopy (EDX). Gi-XRD result shows that films deposited over quartz are poly-crystalline in nature and are oriented along (002), (102), and (103) planes. FESEM analysis shows that 300 nm thick film is distributed uniformly over the surface and 200 nm ZnO thin film is distributed mainly at the center. EDX results show the presence of Zn and O elements in both deposited thin films. I-V characteristics in the dark show Schottky contact with Vc 2.9 V and 1 V for 200 nm and 300 nm thin films respectively. The optical band gap of ZnO thin films intersects at the same photo energies for both thicknesses. Tauc’s plot of both films reveals the similar optical band gap energies of 3.25 eV in both deposited films.

Dipole plasmon vitalized efficient white light emission via charge transfer in all oxide-based heterojunctions

Solid-state white-light emission, which is rapidly becoming the standard in a wide range of lighting applications, can be regarded as the best possible light source for next-generation cost-effective lighting. Herein, we report a simple solution-based technique to get efficient white-light emission using all-oxide semiconductor-based heterojunction. In this work, vertically oriented CuO nanorods were used for outstanding white-light emission by depositing ZnO thin films over CuO nanorods. The resulted bi-layered ZnO/CuO heterojunction arrangement have shown excellent optoelectronic properties. Furthermore, the inclusion of Au layer between ZnO/CuO heterojunction has improved white-light emission significantly and as an integral, a white light photoluminescence (PL) with a chromaticity coordinate of (0.32, 0.34) was obtained. Ab-initio calculations have supported our mechanism of charge transfer from CuO to ZnO especially with Au insertion. The presented work will provide insights into the intriguing optoelectronic properties of oxide hetero-structures.

Evaluation of the Structural, Optical and Photoconversion Efficiency of ZnO Thin Films Prepared Using Aerosol Deposition

As compared to other deposition techniques such as atomic layer deposition, chemical vapour deposition and sputtering, aerosol deposition (AD) is a simple and cost-effective technique to produce ZnO thin films. In this work, the effect of deposition cycles on the structural, optical, and photo-conversion efficiency (PCE) of dye sensitized solar cells of ZnO thin films deposited by AD (AZ) was systematically studied. The structural, optical, and PCE% of two-cycle deposited ZnO thin film (AZ-II) exhibited the highest performance. Further increment in deposition cycle caused deterioration in the structural, optical, and PCE performance. The thickness of ZnO thin films decreased due to abrasion of the deposited film by the subsequent stream of highly energetic ZnO particles. Loosely bound particles could be found on the surface of ZnO thin film after three deposition cycles (AZ-III). The AZ-III films exhibited poor crystal quality, with many crystal defects such as interstitial oxygen as suggested in room temperature photoluminescence analysis.

The role of Zn-complexing agents in the chemical bath deposition of ZnO and ZnS thin films

In order to control the deposition of Zn-related films by chemical bath deposition, the effects of Zn-complexing agent are analyzed. ZnS films were produced by chemical bath deposition technique employing sodium citrate, ethanolamine and Triethanolamine as complexing agents. The deposition conditions for ZnS (ZnO) thin films were obtained through a thermodynamic analysis, using distribution diagrams for molar fraction of Zn complexes. From species distribution diagrams of Zn-ethanolamine, Zn-Triethanolamine and Zn-citrate. It was found that for pH values between 4 and 6 the highest Zn fraction is obtained. The results highlight the importance of complexing agent morphology, while the use of ethanolamine and triethanolamine produce ZnO films due to their high reactivity; the use of sodium citrate produce ZnS films. Deposited ZnS films have a cubic structure, n-type conductivity, resistivity of 8.36×104 ??cm with a 3.75 eV bandgap.

Spray deposition of the nanostructured ZnO thin films for non-volatile resistive switching memory applications

Spray deposition of the nanostructured ZnO thin films for non-volatile resistive switching memory applications

Insight of the role of F-impurity on the structural, electro-optical properties of ZnO: DFT and experiment

A comprehensive study is performed to investigate the consequence of F doping on the structural, electronic, optoelectrical, and photoluminescence properties of ZnO. In the theoretical part, the density functional theory (DFT) is used to study the electronic and optical properties of F-doped ZnO. Whereas, the role of F on the structural, morphological, and optoelectrical characteristics of spray deposited ZnO thin films are studied by experimental means. Electronic band structures, density of states, and optical properties indicated that F is an efficient donor and broadened the direct band gap of F:ZnO system because of the well-known Burstein-Moss effect which matches the experimental data. Shifting of the Fermi level into conduction band (CB) fallouts the improvement of electrical conductivity and carrier concentrations of the doped system. The lattice constants of ZnO are increased due to F doping which is in accord with our experimental results. The existence of F1s in the films is confirmed by X-ray photoelectron spectroscopy (XPS) inspection. Surface morphology reveals the formation of nano-wall structures with different aspect ratios. Photoluminescence spectra show PL emissions for un-doped and 5% F-doped samples at 3.38 eV assigned to the near band edge (NBE) emission and weak peaks at 2.74 and 2.63 eV are attributed to emission from defect states. The optical band gap value first decreased up to 1% F content and then started to increase with increasing F concentration, which is well supported by the theoretical results. The findings from this study will be helpful for further investigation and selecting suitable areas of applications.

Atomic layer deposition of Zr-sandwiched ZnO thin films for transparent thermoelectrics

Atomic layer deposited (ALD) transparent thermoelectric materials enable the introduction of energy harvesting and sensing devices onto surfaces of various shapes and sizes in imperceptible manner. Amongst these materials, ZnO has shown promising results in terms of both thermoelectric and optical characteristics. The thermoelectric performance of ZnO can be further optimized by introducing extrinsic doping, to the realization of which ALD provides excellent control. Here, we explore the effects of sandwiching of ZrO2 layers with ZnO on glass substrates. The room-temperature thermoelectric power factor is maximised at 116μW m−1 K−2 with samples containing a 2% nominal percentage of ZrO2. The addition of ZrO2 layers is further shown to reduce the thermal conductivity, resulting in a 20.2% decrease from the undoped ZnO at 2% doping. Our results contribute to increasing the understanding of the effects of Zr inclusion in structural properties and growth of ALD ZnO, as well as the thermal and thermoelectric properties of Zr-doped ZnO films in general.

Design, implementation, and characterization of an automated SILAR system: validation with ZnO thin film deposition

Design, implementation, and characterization of an automated SILAR system: validation with ZnO thin film deposition

Effect of annealing temperature on response time of ZnO photoconductor fabricated using thermal evaporation technique

ZnO has been deposited on SiO2/Si substrate using thermal evaporation technique. Further, the deposited ZnO thin film has been annealed at 400 °C, 600 °C, and 800 °C separately. The deposited ZnO thin films have been characterized using Ultraviolet-visible Diffuse Reflectance Spectroscopy (UV–vis DRS), Atomic force microscopy (AFM), x-ray diffraction (XRD) technique, and Scanning electron microscopy (SEM). The deposited ZnO thin films have multiphase structures of ZnO such as hexagonal, unknown and cubic. UV-visible spectra of deposited films show absorbance edges in UV and visible regions. The average particle size of non-annealed ZnO is ∼60 nm, whereas annealed ZnO (at 800 °C) is ∼124 nm. The average surface roughness of ZnO sample annealed at 800 °C is lower than that of non-annealed ZnO sample and ZnO samples annealed at 400 °C and 600 °C. Sputtering technique has been used to make gold contact on ZnO film for testing the photoconductivity property. The rise time of ZnO photoconductor annealed at 800 °C (Tr = 0.04 s) is very fast as compared to that of all other ZnO photoconductors prepared using non-annealed ZnO sample and ZnO samples annealed at 400 °C and 600 °C.