ZnO Substrates Research Articles

Adsorption and evolution of N2 molecules over ZnO monolayer: a combined DFT and kinetic Monte-Carlo insight

A large surface area, wide band gap, and unique bonding property between Zn and O atoms make the hexagonal ZnO monolayer attractive as a gas sensor. In the present work, the adsorption and evolution of nitrogen (N2) molecules over a ZnO monolayer have been studied using two different theoretical methods: van der Waals density functional theory (vdW-DFT) and kinetic Monte-Carlo (kMC) simulation. The adsorption and diffusion (hopping over the surface) energy of a N2 gas molecule has been calculated considering the different sites over the ZnO substrate using the revPBE-vdW functional. Bader charge, electron localization function analysis, density of states and band structure plotting have been used to understand the adsorption mechanism. Lateral repulsive interaction between two N2 molecules limits the maximum packing number of gas molecules within one hexagonal ring. The output of the vdW-DFT calculation has been fed to the kMC code to predict the rate of adsorption, desorption, and diffusion, along with the overall surface coverage at different temperatures and pressures. Finally, the change in the N2 adsorption energy has been predicted with the increase of the ZnO layer number.

Polarity of homoepitaxial ZnO films grown by Nd:YAG pulsed laser deposition

We investigate the stability of the polar surface of ZnO films grown homoepitaxially on atomically flat ZnO (0001¯) O-face substrates by neodymium yttrium aluminum garnet (Nd:YAG) pulsed laser deposition (PLD). For films grown in the temperature range from 500 to 700 °C, ion scattering spectroscopy showed that the film surface termination was the same as the ZnO substrate. Even for a Mg0.2Zn0.8O/ZnO superlattice, no polarity reversal occurred, indicating that the ZnO (0001¯) O-face is highly stable, despite the film surface sputtering caused by the high kinetic energy of the PLD plume generated by the Nd:YAG laser.

Stability Properties of Inverted Organic Solar Cells Prepared with a ZnO Buffer Layer

Organic solar cells (OSCs) of inverted structure (IOSC) were designed to enhancement the solar cell efficiency and stability in organic based solar cell. IOSC was built with the structure of Au/P3HT:PCBM/ZnO/ITO. ZnO thin layers were fabricated on ITO electrodes using the unbalanced magnetron sputtering method. ZnO layer is used as the buffer layer in this structure to prevent oxidation by UV light to the interface of the organic layer and reduce the energy barrier, allowing electron to be easily transferred between the ITO energy level and the organic acceptor energy level (LUMO). ZnO films are also used as a barrier layer to prevent hole injection from P3HT due to the lack of charge carrier recombination. XRD results exhibited that the particle size in ZnO layers increased as the substrate temperature increased. The conversion efficiency of IOSC improved with increasing ZnO substrate temperature. Moreover, compared to the existing device, the IOSC using a ZnO buffer layer was in a stable state for a longer period of time. After about 7 days, it woas found that the Voc of the hybrid solar cells remained almost constant over time and under all conditions. As a result, the ZnO film in the OSC plays an important role for protecting the organic layer of OSCs and enhancing the efficiency.

Cyanide Linkage Isomerization Induced by Cobalt Oxidation-State Changes at a Co-Fe Prussian-Blue Analogue/ZnO Interface.

Understanding the interfacial composition in heterostructures is crucial for tailoring heterogenous electrochemical and photoelectrochemical processes. This work aims to elucidate the structure of a series of Co-Fe Prussian blue analogue modified ZnO (PBA/ZnO) electrodes with interface-sensitive vibrational sum frequency generation (VSFG) spectroscopy. Our measurements revealed, for the first time, a cyanide linkage isomerism at the PBA/ZnO interface, when the composite is fabricated at elevated temperatures. In situ VSFG spectro-electrochemistry measurements correlate the CoII➝CoIII oxidation with the flip of the bridging CN ligand from Co-NC-Fe coordination mode to a Co-CN-Fe one. Photoluminescence measurements and X-ray photoelectron spectroscopy reveal that this unprecedented linkage isomerism originates from surface defects, which act as oxidation sites for the PBA. The presence of such surface defects is correlated with the fabrication temperature for PBA/ZnO. Thus, this contribution identifies the interplay between the surface states of the ZnO substrates and the chemical composition of PBA at the ZnO surface, suggesting an easily accessible approach to control the chemical composition of the interface.

Synthesis, characterization and corrosive resistance of ZnO and ZrO2 coated TiO2 substrate prepared via polymeric method and microwave combustion

The TiO2 substrate coatings containing varied ZnO or ZrO2 nanoparticles were made using the polymeric and microwave combustion methods and then thermally treated at various temperatures. Furthermore, before coating on the substrate, the produced nanoparticles undergo characterization and calcination to optimize the conditions for developing ZnO and ZrO2 phases and track their composition. The X-ray diffraction method (XRD), transmission electron microscopy (TEM), and infrared analysis (IR) are used to characterize the calcined produced nanoparticles. After heat treatment at 1000 °C, the TiO2 substrate is prepared. The produced coated substrate is studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared (IR), apparent porosity, bulk density, chemical corrosive properties and electrochemical measurement in 3.5 % NaCl and 1 M HCl solutions. The corrosion resistance of ZnO or ZrO2-covered TiO2 substrate is ascertained by anticorrosive behaviors, which include weight loss, apparent porosity, corrosion rate, and SEM. The findings showed that 800 °C is the ideal temperature for preparing ZrO2-coated substrate, whereas 1000 °C is the perfect temperature for preparing ZnO-coated substrate. The microstructure reveals surface micro-cracks on the ZrO2-coated TiO2 substrate. Good dispersion, homogeneity, and compaction were noted for the ZnO-coated substrate. Between 14 and 17 % of the ZnO-coated substrate and 20–21 % of the ZrO2-coated substrate, made via polymeric and microwave combustion techniques, had visible porosity when ZnO-coated samples exhibited greater corrosion resistance against NaCl media. In contrast, ZrO2-coated samples had much stronger anticorrosive qualities in HCl media than uncoated and Zn-coated samples. According to the electrochemical results, the ZnO-coated TiO2 synthesized by polymeric technique at 1000 °C showed 99.86 % inhibitory efficiency against NaCl. An inhibitory efficiency of 94.4 % was observed in a ZrO2-coated TiO2 substrate that was produced at 800 °C using a polymeric technique.

Morphological, structural and electronic properties of zinc oxide nano structures deposited on ZnO substrate layer – A theoretical perspective

The work investigates the deposition of zinc and oxygen atoms on a Zinc terminated ZnO substrate, maintaining their stoichiometric ratio (O:Zn) at 0.8, under varying incident energies (0.5 eV and 5 eV) and temperatures (300 K and 700 K) using the ReaxFF potential in Molecular Dynamics (MD) simulation. The study explores the impact of deposition conditions on growth mechanisms, film morphology, and structural parameters such as Radial Distribution Function (RDF) and Coordination Number (CN). RDF analysis highlights disordered atomic arrangements and diverse bonding configurations within the film, with CN showing deviations from perfect crystalline ZnO, indicating non-uniform, non-crystalline, and nano behaviour. Post-heating the films to temperatures approaching the ZnO melting point results in enhanced crystallinity, as evidenced by distinct, dominant, and multiple RDF peaks. Density Functional Theory (DFT) approach of the deposited structures elucidates the formation of ZnO nanoclusters-(ZnO)3 and (ZnO)4 and investigates their electronic structure properties. DFT analysis of the post-heated films reveals the formation of ZnO monomers (ZnO), indicating an approaching crystalline behaviour, yet the films exhibit non-epitaxial and non-uniform characteristics. DFT calculations were instrumental in validating the observed structural behaviours in the deposited films. The study underscores the significance of stoichiometric ratio in film deposition and demonstrates the temperature-dependent evolution of structural properties towards crystallinity, shedding light on the intricate dynamics of ZnO film growth offering tailored control over film properties for enhanced performance in practical applications such as optoelectronics and gas sensing.

Enhancing biogas yield of Xyris capensis grass using different nanoparticles additive

To enhance the efficiency of the anaerobic digestion process of lignocellulose feedstocks, there is a need for appropriate pretreatment methods. The influence of nanoparticles additive on biogas yield of new novel Xyris capensis grass as biogas feedstock was investigated. A laboratory-batch experiment was set up at mesophilic conditions (37 ± 2° C) to study the biogas production potential of Xyris capensis, and different nanoparticles were added as a means of pretreatment. 20 mg/L of Fe3O4, 1.4 mg/L of CuO, 10 mg/L of ZnO, and 10 mg/L of MgO were added to the anaerobic digestion process, and their influence on biogas and methane yield was compared with the untreated substrate. Biogas yield of 376.67, 156.86, 175.34, 190.00, and 290.00 mL/g VSadded was recorded for Fe3O4, CuO, ZnO, MgO additives, and untreated substrate, respectively, while methane yield of 282.50, 156.86, 97.66, 116.33, and 198.51 mLCH4/g VSadded were observed, respectively. It can be observed that only 20 mg/L of Fe3O4 increased biogas and methane yields by 29.89 and 42.31%, respectively.

Defective ZnO Nanoplates Supported AuPd Nanoparticles for Efficient Photocatalytic Methane Oxidation to Oxygenates

AbstractDirect photocatalytic methane oxidation into value‐added oxygenates under mild conditions enables the sustainable chemical production but suffers from the lack of active photocatalysts and the overoxidation issue. Herein, defective ZnO nanoplates supported AuPd nanoparticles for efficient methane oxidation with O2 as the oxidant at room temperature are reported. A maximum liquid oxygenates productivity of 152.2 mm g−1 h−1 and a selectivity of 86.7%, more than half of which is CH3OH, are achieved over the optimized AuPd/ZnO photocatalyst, resulting in a 16.5% apparent quantum efficiency at 380 nm. The superior photocatalytic performance is benefited from the synergistic effect between defective ZnO substrate and AuPd cocatalyst, wherein the former facilitates CH4 adsorption, and the latter promotes light absorption, charge separation, as well as O2 activation into the reactive oxygen species. This work provides new guidance for regulating the activity and selectivity of the photocatalyst toward methane oxidation.

Effect of morphology of ZnO on colorimetric hydrogen sensitivity of PdO@ZnO hybrids

The PdO decorated ZnO (PdO@ZnO) colorimetric hydrogen sensor garners attention for visually detecting hydrogen leaks without relying on external electrical systems. While sensitivity optimization primarily focuses on PdO variations, the influence of the ZnO substrate effect remains less explored. PdO@ZnO hybrids with four different morphologies (sphere, rod, plate, hexagonal disk) are synthesized using an acid-base reaction. The morphology of ZnO influences PdO adsorption due to variations in surface area and oxygen defects. The chemical state of adsorbed palladium species is also affected by the ZnO charge. Among these hybrids, the PdO@ZnO hexagonal disk demonstrates the quickest response time (T90; 182.4s) and the highest color difference (ΔE; 16) under exposure to 4 vol% hydrogen gas. This superior performance is attributed to the hexagonal disk's larger surface area, appropriate zeta potential, and oxygen defect, all of which enhance PdO adsorption. These findings enhance our comprehension of how morphology impacts the colorimetric hydrogen sensitivity of PdO@ZnO hybrids.

Interfacial electronic state between hexagonal ZnO and cubic NiO.

The interface of two dissimilar materials gives rise to a myriad of interesting structural, magnetic, and electronic properties that may be utilized to produce novel materials with unique characteristics and functions. In particular, growing a cubic oxide film on top of a hexagonal oxide substrate results in such unique properties due to the conflict of their respective stabilization mechanisms within the interface layer. This study aims to elucidate the electronic properties of the interface between hexagonal ZnO and cubic NiO by analyzing the interface electronic states within epitaxial NiO films grown on ZnO substrates, expressed in the form of ultraviolet photoemission spectroscopy (UPS) for valence band structure and X-ray absorption spectroscopy (XAS) spectra for conduction band structure. This is accomplished through a modeling approach in which the film, substrate, and interface signals are assumed to be related to each other by a set of mathematical equations, and then rearranging and modulating the equations to obtain unique UPS and XAS spectra that depict the interface electronic states.

Reactivity of organogermanes with ZnO substrate

Germanium (Ge)-based thin film through sol-gel coating technology can be a suitable alternative like their silane analogue to develop metal-free and solvent-free corrosion protective coating with additional functional properties for galvanized (GI) steel. In this work, adsorption mechanism and reactivity of functionalized (by functional groups such as epoxy, amine, and mercapto) and non-functionalized - organogermane alkoxides towards GI steel substrate were investigated using density functional theory (DFT), where (ZnO)12 cluster was adopted as model of GI steel and other ZnO substrate. Calculated global reactivity parameters of organogermanes suggested that functionalized organogermanes were more efficient for corrosion protection of ZnO substrate. Adsorption process was exothermic and free energy change (ΔG) in adsorption process lied between 27.4 kcal/mol and 51.9 kcal/mol which confirmed adsorption potentiality of organogermanes. Adsorptions of functionalized organogermanes were much more exothermic (∼50 kcal/mol) than that of non-functionalized one (∼27 kcal/mol) which suggested chemisorption of functional organogermane molecules. Geometry, MOs, and charge analyses of adsorbed structures further supported that all functional organogermanes chemisorbed on the GI steel. Multiple bonds were formed at the interface. Presence of heteroatoms, like O/N/S in organogermane molecules assisted in formations of chemical bonds with Zn atoms of the substrate. Ge center took hypervalency and formed non-classical Ge-O bond with O atom of the substrate in all functional organogermanes. Formation of OH—O hydrogen bonds were also observed at the interface. These Ge-O and OH—O bond formation played key roles in the interface and manifested stronger interaction, making functional organogermane alkoxides suitable for coating applications. Stronger adsorptions of functional organogermanes could be interpreted in terms of higher highest occupied molecular orbital (HOMO) energies and lower HOMO-lowest occupied molecular orbital (LUMO) gap values for functionalized organogermanes which favored the electron donation from the HOMOs of functionalized organogermanes to the LUMOs of (ZnO)12 cluster.

Adsorption mechanism of formaldehyde, ammonia and sulfur dioxide gases on inexpensive metal-doped ZnO surface: A DFT study

Here, the adsorption mechanisms and detection performance of three different hazardous gases, including formaldehyde (CH2O), ammonia (NH3), and sulfur dioxide (SO2), on undoped ZnO and inexpensive metal-doped ZnO surfaces were studied by density functional theory (DFT). CH2O and NH3 are physically adsorbed on the zinc top site (t-site) and six-membered ring pore site (p-site) on the undoped ZnO surface, and the adsorption energies are -0.56 eV and -0.32 eV. The difference is that SO2 is weakly chemisorbed on bridge site (b-site) of ZnO surface with an adsorption energy of 1.78 eV. The adsorption energy of Al-doped ZnO for CH2O, NH3, and SO2 is higher than that of undoped ZnO, reaching -1.64 eV, -1.69 eV, and -3.62 eV respectively. The adsorption properties of Cu-doped ZnO for CH2O and SO2 are not significantly improved with exception of NH3. Collectively, the adsorption mechanism of undoped and doped ZnO or hazardous gases is elucidated, which provides theoretical guidance for the further utilization of ZnO substrate materials in the field of gas sensitivity.

Theoretical calculation on adsorption of molecular hydrogen in monolayer ZnO

Adsorption, desorption, and diffusion dynamics of hydrogen gas molecules over a hexagonal ZnO monolayer have been studied thoroughly in the van der Waals Density Functional Theory (vdW-DFT) framework in association with kinetic Monte Carlo (kMC) simulations. Hydrogen molecules can attach to a ZnO sheet via a weak physisorption process with a limitation of maximum attachment of three molecules per hexagonal ring. Pressure and temperature are the main deciding parameters for the overall storage capacity of hydrogen on a ZnO substrate. kMC simulations are performed to capture the stochastic behavior of surface dynamics of gas molecules. Adsorption energy and diffusion barrier are predicted to be around 50–60 meV and 4–12 meV, respectively, according to vdW-DFT calculations. kMC simulations with these energy parameters estimate the surface coverage of hydrogen to be pretty high below room temperature and high pressure. Furthermore, the hydrogen adsorption in the ZnO monolayer leads to the increase of the bandgap value, subsequently changing the conductivity of the material. The present research work sheds light on the usage of a ZnO monolayer for suitable hydrogen gas storage and sensing applications.

Synthesis and structural feasibility of photonic materials

Based on the sample’s texture and colour changed at various temperatures, this study examined the optical-thermal dependency of chiral nematic liquid crystal ink samples. This work examines ZnO thin films from an optical and structural standpoint. The required layer thickness was produced by spinning a zinc oxide solution over a cleaned glass substrate at 4000 rpm for 30 seconds at room temperature. The samples were then subjected to annealing, which was done from 150 to 600°C in increments of 50°C. This thin coating’s optical characteristics were examined using an electron microscope and an ultraviolet-visible spectrophotometer. The optical transmittance, reflectance, and absorbance of zinc oxide were measured to estimate its optical band gap. When a light beam is transmitted or reflected, photonic crystals can display pertinent optical characteristics. The reflecting qualities in particular can be of interest in a two-dimensional photonic crystal and subsequently tuned for many technical applications, including selective high-reflection mirrors, photovoltaic solar systems, tuneable laser cavities, and many more. The development of Si has enabled the investigation of the reflective optical characteristics of two-dimensional photonic crystals grown on hybrid ZnO substrates with 10-45 nm size.

Substrate-induced bonding asymmetry leading to strong phonon anharmonicity and largely reduced thermal conductivity of monolayer XS2 (X = Mo and W) from first-principles calculations

Thermoelectric materials have properties such as direct conversion of waste heat into electricity and environmental friendliness, which make them promising for renewable energy utilization, however, the lower conversion efficiency limits the large-scale application of thermoelectric materials. Monolayer transition metal dichalcogenides (TMDs) are candidates for thermoelectric materials due to their high power factor, but their higher thermal conductivity (TC) limits the further improvement of the figure of merit (ZT). Here, we employ first-principles calculations and solve the Boltzmann transport equation (BTE) to compare the lattice TC of free-standing monolayer XS2 (X = Mo and W) and monolayer XS2 supported on SiC (0001) and ZnO (0001) substrates. We find that the lattice TC of monolayer XS2 supported on SiC (0001) and ZnO (0001) substrates are sharply reduced. Especially supported on the ZnO (0001) substrate, the lattice TC of XS2 reduce by 65 %–70 %, which is expected to improve the thermoelectric properties of monolayer XS2. In addition, we report the underlying cause of this significant reduction in TC. Firstly, the substrate drives softening of the acoustic branch, which leads to a decrease of phonon group velocity in the low-frequency and an enhancement of the three-phonon scattering. Then, the asymmetric bonding of XS2 is induced by the substrates, which enhance phonon anharmonicity and reduce the phonon lifetime. Our results demonstrate that the lattice TC of monolayer XS2 can be tuned by adjusting the substrate, which has certain reference values for the thermoelectric design of XS2.

Cu-substrate interfacial adhesion: A key factor in controlling the oxidation of Cu thin films on oxide substrates

Despite the likelihood of H2O adsorption on the highly defective surfaces of polycrystalline Cu thin films under ambient atmospheric conditions, the influence of adsorbed H2O on the oxidation of Cu thin films has not been fully recognized. This study explored the oxidation of 16 nm-thick polycrystalline Cu thin films deposited on SiOx and ZnO substrates under conditions mimicking accelerated oxidation at 85 °C and 85% relative humidity. Through experimental evaluations and numerical calculations, we discovered that enhanced Cu adhesion to oxide substrates effectively suppresses the oxidation of Cu thin films. A notable increase in adhesion at the Cu–ZnO interface resulted in a significant decrease of Cu oxidation on ZnO substrates, starkly contrasting with the accelerated Cu oxidation on SiOx substrates. The augmented adhesion between Cu and ZnO slowed the solid-state outward diffusion of Cu ions from the Cu–ZnO interface, thus inhibiting oxidation. Conversely, the weak adhesion between Cu and SiOx stimulated the outward diffusion of Cu ions, leading to void formation at the interface. These findings challenge prevailing beliefs by revealing a strong correlation between oxidation and metal–substrate adhesion. Our results provide valuable insights for identifying the key factors governing oxidation mechanisms.

First-principle calculations of structural and optoelectronic properties of wurtzite Zn1-x-yBexMgyO quaternary alloys closely lattice matched to the ZnO substrate for UV-A optoelectronic applications

Structural and optoelectronic properties of some wurtzite Zn1-x-yBexMgyO quaternary alloys closely lattice-matched to w-ZnO substrate are investigated with density functional theory. The Zn0·75Be0·0625Mg0·1875O, Zn0·6875Be0·0625Mg0·25O and Zn0·625Be0·0625Mg0·3125O alloys having Be/Mg composition ratio in the experimentally prescribed range 2.0–4.0 are considered to achieve high quality stable wurtzite quaternary crystals. Lattice constants (a0, c0) decrease, while direct band-gap (Γ-Γ) increases with increasing Be and Mg composition sum. These optically anisotropic quaternary alloys exhibit diverse optical properties due to electronic transitions from valence O-2p to Be-2p, Be-3s, Zn-5s, Mg-4s, Mg-3p states of conduction band. Calculated optical energy gap, slightly higher than band-gap, shows blue shift with increasing Be and Mg composition sum. Calculated static optical constants ε1(0), n(0), R(0) of these alloys reduce with increasing band-gap and vice versa. These quaternary alloys with band-gaps, fundamental absorption edges and optical energy gaps in the UV-A region would have potential applications in fabricating UV-A optoelectronic devices.

Substrate Morphology Directs (001) Sb2Se3 Thin Film Growth by Crystallographic Orientation Filtering.

Antimony chalcogenide, Sb2X3 (X = S, Se), applications greatly benefit from efficient charge transport along covalently bonded (001) oriented (Sb4X6)n ribbons, making thin film orientation control highly desirable - although particularly hard to achieve experimentally. Here, it is shown for the first time that substrate nanostructure plays a key role in driving the growth of (001) oriented antimony chalcogenide thin films. Vapor Transport Deposition of Sb2Se3 thin films is conducted on ZnO substrates whose morphology is tuned between highly nanostructured and flat. The extent of Sb2Se3 (001) orientation is directly correlated to the degree of substrate nanostructure. These data showcase that nanostructuring a substrate is an effective tool to control the orientation and morphology of Sb2Se3 films. The optimized samples demonstrate high (001) crystallographic orientation. A growth mechanism for these films is proposed, wherein the substrate physically restricts the development of undesirable crystallographic orientations. It is shown that the surface chemistry of the nanostructured substrates can be altered and still drive the growth of (001) Sb2Se3 thin films - not limiting this phenomenon to a particular substrate type. Insights from this work are expected to guide the rational design of Sb2X3 thin film devices and other low-dimensional crystal-structured materials wherein performance is intrinsically linked to morphology and orientation.

Study on Method of Doping Au Nanoparticles on ZnO Stratified Microstructure to Enhance Photocatalytic Ability and Antibacterial Activity

In this study, stratified microstructure gold/zinc oxide (Au/ZnO) composites were successfully prepared by the method of dispersing Au nanoparticles (Au NPs) on the surface of the hierarchical flower ZnO via HAuCl4 reduction in the presence of different reducing agents such as sodium citrate (SC), sodium borohydride (SB), sodium hydroxide and ethanol (SE), and Hg lamp 250W. Au-doped samples were named Au/ZnO-SC, Au/ZnO-SB, Au/ZnO-SE, and Au/ZnO-Hg lamp, respectively. Au/ZnO-SC and Au/ZnO-SB revealed the uniform distribution of Au nanoparticles on the ZnO substrate, meanwhile, Au nanoparticles were very densely distributed in Au/ZnO-SE and Au/ZnO-Hg lamp samples. The pure ZnO only showed an absorption peak in the ultraviolet (UV) region, Au/ZnO samples indicated additional absorption peaks in the visible light region (500-600 nm), which were characteristic of the surface plasmon resonance (SPR) effect of Au NPs in composites. Therefore, their bandgap energy was reduced compared to ZnO (3.202 eV), leading to increased photocatalytic efficiency under visible light irradiation. Among the doped samples, Au/ZnO-SC (with Au content as 5 wt%) had the largest surface area (26.23 m2/g) and the highest pore volume (0.263 cm3/g) and average pore width (33.2 nm). As a result, it showed the highest catalytic efficiency through complete degradation of tartrazine (TA) within 30 min with a reaction rate of 0.124 min−1 under Hg lamp 250 irradiation. In addition, both pure ZnO and Au/ZnO nanocomposites exhibited high antimicrobial activity in killing Escherichia coli (E. coli), and their enhancing effect of them was reliant on the weight ratio of Au on ZnO and the concentration of tested samples. These results indicated that Au/ZnO material has prominent potential for applications in water environment treatment. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Characterization of CdxTeyOz/CdS/ZnO Heterostructures Synthesized by the SILAR Method

CdxTeyOz/CdS/ZnO heterostructures were obtained by the SILAR method using ionic electrolytes. A CdS film was formed as a buffer layer for better adhesion of the cadmium-tellurium oxides to the substrate surface. In turn, the ZnO substrate was previously prepared by electrochemical etching to form a rough textured surface. In addition, an annealing mode was used in an oxygen stream to complete the oxidation process of the heterostructure surface. The resulting nanocomposite was investigated using RAMAN, XRD, SEM, and EDX methods. We assume that the oxides CdO and TeO4 initially form on the surface and later evolve into TeO2 and TeO3 when saturated with oxygen. These oxides, in turn, are the components of the ternary oxides CdTeO3 and CdTe3O8. It should be noted that this mechanism has not been fully studied and requires further research. However, the results presented in this article make it possible to systematize the data and experimental observations regarding the formation of cadmium-tellurium films.