Growth Of ZnO Research Articles

Enhancing the electrical, optical, and structure morphology using Pr2O3-ZnO nanocomposites: Towards electronic varistors and environmental photocatalytic activity

In this proposed research, the samples of undoped and several concentrations of praseodymium-doped zinc oxide (Pr2O3- ZnO) nanoparticles ranged from 0.001 g to 5 g were synthesized using a combustion technique as a simple, efficient, inexpensive, and environmental method. The structure, morphology, and chemical bonding were investigated by X-ray diffraction (XRD), and scanning electron microscopy (SEM), respectively, of the prepared Pr2O3-ZnO photocatalysts. The attained data from the previous devices sustained the ZnO growth from crystalline to satisfactory nanoparticle structure through changing the Pr3+-doping concentrations inside the host matrix. Furthermore, the optical features have been investigated via UV–Vis diffused reflectance spectroscopy (DR), and AC electrical conductivity was studied to investigate the Pr3+-nanoparticles' influence on the optical characteristics, energy bandgaps, of all proposed Pr2O3-ZnO nanostructured samples. The addition of Pr3+ dopants decreases the energy bandgap slightly and confines the photogenerated electron-hole recombination. The studied Pr2O3-ZnO nano-samples have been applied in photocatalytic degradation of methylene blue (MB) as an example for organic dyes and p-chlorophenol (p-CP) under visible light irradiation. The influence of Pr3+-concentration, H2O2 concentration, and pH of the medium on the photocatalytic reaction have been studied. As the praseodymium doping ratios increased; the photocatalytic efficiency increased. After the addition of moderate Pr3+-doping, further generation of hydroxyl radicals over ZnO. For 1% Pr3+-ZnO, the optimal photocatalyst is a degradation of 100% of p-chlorophenol and methylene blue solutions. The prepared Pr2O3-ZnO nanostructured samples are amazing, promising candidates in novel potential nano-applications for wide-ranged from varistors, wastewater treatments, biomedical and photocatalytic degradation for phenol and organic dyes to different environmental fields.

Low-Cost Electrodeposition of Size-Tunable Single-Crystal ZnO Nanorods

In this paper we report a low cost, simple, electrochemical method for large-area growth of single crystal ZnO nanorods. The method utilizes a metallic zinc foil as the source of the necessary zinc ions for ZnO growth on indium-doped tin oxide (ITO) glass slides. The method is thoroughly discussed and investigated varying all the parameters involved. The resulting ZnO nanorods are highly oriented along c-axis and densely packed, while their length and diameter can be tuned by varying the growth parameters. Two different types of seed layers on the ITO glass slides are tested. A seed layer made by spin coating of ZnO nanoparticles results in a twofold increase of the ZnO nanorod surface density as compared with a ZnO thin film seed layer by physical vapor deposition. Additionally, the effect of oxygen supply during electrodeposition was investigated as a crucial regulatory parameter not only for the geometrical and topological characteristics of the ZnO nano-arrays but for their physical properties as well.

Room temperature selective sensing of benzene vapor molecules using mixed oxide thin film of zinc oxide and cadmium oxide

The demand for the sensing of benzene vapor increases in recent times as its exposure to even 1 ppm concentration for 8 h leads to adverse health effects. Towards this, for the first time, we are reporting the room temperature benzene sensing properties of nanostructured ZnO–CdO mixed oxide thin films deposited using the spray pyrolysis technique. Three different ratios of ZnCl2 and CdCl2 (0.08:0.02 M), (0.06:0.04 M) and (0.04:0.06 M) were considered for the deposition of ZnO–CdO mixed oxide thin films. For the comparative analysis, pure ZnO thin film was also deposited and investigated. XRD pattern divulged the growth of cubic phased CdO and hexagonal wurtzite phased ZnO for the mixed oxide thin films deposited in the three different ratios. Surface morphologies revealed the formation of spherical nanograins for the pure ZnO thin film, whereas it started to aggregated randomly for the films deposited in the ratio of (0.08 M:0.02 M) and (0.06 M:0.04 M). In contrast, the mixed oxide thin film deposited in the ratio of (0.04 M:0.06 M) showed nanoflakes-like morphology. The pure ZnO thin film was selective towards ammonia vapor, whereas all the mixed oxide thin films were selective towards benzene vapor. In particular, the film deposited in the ratio of (0.04 M:0.06 M) showed a selective response of 453 towards 100 ppm of benzene with a response and recovery times of 57 and 65 s respectively at room temperature (48%RH). The detection range was found to be 1–200 ppm of benzene. The influence of grain boundary effect on the sensing response was also studied and reported.

Photothermal Study of ZnO Nanoparticle-Bi2O3-Mn2O3 Ceramics Doped with Different Compositions from Al2O3 at Various Sintering Temperatures

In this work, the optical absorption behavior of ZnO nanoparticle–Bi2O3–Mn2O3 doped with different compositions of Al2O3 at various sintering temperatures was investigated using photopyroelectric spectroscopy (PPE). Different Al2O3 concentration and sintering temperatures affect significantly the varistor characteristics, predominantly promoting ZnO growth at a lower amount of Al2O3. However, the addition of larger amounts of Al2O3 inhibits the grain growth by the increasing amount of spinel phase. The large surface properties of the nanoparticles enhanced the surface interactions even at minimal sintering temperatures. The density is increased depending on increasing the Al2O3 amounts and sintering temperature. X-ray diffraction measurements provided that Al2O3 additive to ceramics leads to construction of the pyrochlore and spinel phase during the sintering process at various temperatures. The energy band gap (Eg) of nanoparticle powder added with 0.0 mol% to 3.0 mol% Al2O3 and sintered through different temperature is obtained by PPE. Optical energy band gap (Eg) was constant at approximately 2.51 eV for 950 °C sintering temperature during all dopant compositions. The energy of band gap reduces in varistors doped with 0.5 mol% Al2O3 doping amount and sintered at 1050 and 1200 °C temperatures. With further increase in Al2O3 up to 1.0 mol%, the value of Eg was 2.15 and 2.21 eV for 1200 °C and 1050 °C, respectively. The superior nonlinearity value (α) is approximately 58 for 950 °C sintered temperature at various adding concentrations. However, at higher sintering temperatures, α value decreases with of the increase in Al2O3 doping concentrations; the value becomes constant beyond 1.0 mol%. The slope of exponential optical absorption is distinguished by steepness factors “σ A” and “σ B,” which are investigated to determine the difference in the energy band gap.

Electrodeposition of ZnO nanorods on graphene: tuning the topography for application as tin oxide-free electron transport layer

The heterostructure of graphene and ZnO nanorods is attractive as a tin oxide-free electron transport layer for a broad variety of excitonic photovoltaic technologies. This work focuses on the effect of electrodeposition variables on morphology and performance of vertically aligned zinc oxide nanorods (ZVNRs) on graphene. This in situ growth technique has potential for fabrication of a wide variety of graphene heterostructures under mild synthesis conditions to prevent graphene damage. Large area graphene was grown by chemical vapor deposition, stacked up to four atomic layers, and transferred to glass. ZVNRs were electrodeposited on the graphene-coated glass and the topography was controlled by changing the electrodeposition parameters of the time, temperature, stirring, and seeding layers. The mechanisms controlling the cathodic electrodeposition of nanocrystals on graphene were studied by scanning electron microscopy of the ZVNRs topography. The effect of the topography of the ZVNRs on the electron generation and transport was studied for photoanode application in reference dye-sensitized solar cells. The charge transfer resistance and kinetics of the materials as photoanodes were measured with the techniques of linear sweep voltammetry, open circuit voltage decay, and electrochemical impedance spectroscopy. The optimization of ZnO growth resulted in an increase of the surface-to-volume ratio of the electrode from 10 to 250 mm−1, 60-fold increase of electron lifetime and ten-fold increase in power output. The results of this study provide fundamental understanding for designing electrodeposition processes of the hybrid ZVNR/graphene material.

Current transport mechanism of atomic layer deposited ZnO on 3C–SiC/p-Si heterostructure

The atomic layer deposition (ALD) growth of ZnO on n-SiC/p-Si heterojunction was carried out and the current transport mechanism of ZnO/n-SiC/p-Si heterojunction was investigated. The current–voltage (I–V) characteristics for n-SiC/p-Si heterojunction showed the normal p-n junction properties, which became reversal for n-ZnO/n-SiC/p-Si heterojunction. The Arrhenius plots of reverse currents versus 1/kT produced the activation energies of 0.42 and 0.21 eV for n-SiC/p-Si and n-ZnO/n-SiC/p-Si heterojunctions, respectively. The decrease of current values with the temperature for n-ZnO/n-SiC/p-Si heterojunction would be due to the interface states near the ZnO/SiC interface. Capacitance–voltage (C–V) characteristics revealed the higher interface state density for n-ZnO/n-SiC/p-Si heterojunction.

Epitaxial growth and properties study of p-type doped ZnO:Sb by PLD

Abstract Undoped and antimony (Sb) doped ZnO films were synthesized on sapphire (0001) substrates using Pulsed Laser Deposition (PLD) method. Structural and morphological studies proved the good crystallinity of the ZnO films with c-axis (0002) orientation growth. The substitution of Sb in ZnO lattice was proved from the analysis of XPS data. Interestingly, it was important that the presence of Sb5+ ions opened the way for the apparition of the complex acceptor (SbZn–2VZn) level with high stability. The decrease in the value of the band gap Eg with Sb doping evidenced the creation of energy levels related to such complex acceptor. From the study of photoluminescence (PL) at low temperatures, it was shown the dominant emission is related to free electron transition from neutral acceptor (e, A0), indicating the conductivity conversion from n to p with Sb doping. The reproducibility and stability of p-type conduction from the ZnO:Sb3% films were evaluated by Hall measurements. As application, ZnO homojunction device was carefully made and shows rectifying current-voltage (I–V) characteristics, typical to perfect diode. Thus, the prepared ZnO–Sb films are promising for application in optoelectronic field.

Formation and optical characteristics of ZnO:Eu/ZnO nanowires grown by sputtering-assisted metalorganic chemical vapor deposition

We report on the growth and optical characteristics of Eu-doped ZnO (ZnO:Eu) films on ZnO nanowires (NWs) by sputtering-assisted metalorganic chemical vapor deposition. ZnO:Eu films are grown by sputtering Eu2O3 targets during the growth of ZnO NWs. The crystal quality of ZnO host materials is improved by using the NW configuration due to a strain relaxation effect, which is elucidated by optical characterization. An enhancement of Eu3+ luminescence at 613 nm is observed at room temperature for the ZnO:Eu/ZnO NWs as compared to a conventional film. Site-selective spectroscopy by direct excitation of Eu3+ ions by a tunable dye laser reveals that the most intense emission peak is located at a wavelength of ∼613.5 nm, which coincides with the main peak under indirect excitation. This result indicates that the observed enhanced Eu luminescence is due to a relative increase in the number of Eu centers which can effectively be excited via the host material.

Influence of chemical and electronic inhomogeneities of graphene/copper on the growth of oxide thin films: the ZnO/graphene/copper case

The interaction of graphene with metal oxides is essential for understanding and controlling new devices’ fabrication based on these materials. The growth of metal oxides on graphene/substrate systems constitutes a challenging task due to the graphene surface’s hydrophobic nature. In general, different pre-treatments should be performed before deposition to ensure a homogenous growth depending on the deposition technique, the metal oxide, and the surface’s specific nature. Among these factors, the initial state and interaction of graphene with its substrate is the most important. Therefore, it is imperative to study the initial local state of graphene and relate it to the early stages of metal oxides’ growth characteristics. Taking as initial samples graphene grown by chemical vapor deposition on polycrystalline Cu sheets and then exposed to ambient conditions, this article presents a local study of the inhomogeneities of this air-exposed graphene and how they influence on the subsequent ZnO growth. Firstly, by spatially correlating Raman and x-ray photoemission spectroscopies at the micro and nanoscales, it is shown how chemical species present in air intercalate inhomogeneously between Graphene and Cu. The reason for this is precisely the polycrystalline nature of the Cu support. Moreover, these local inhomogeneities also affect the oxidation level of the uppermost layer of Cu and, consequently, the electronic coupling between graphene and the metallic substrate. In second place, through the same characterization techniques, it is shown how the initial state of graphene/Cu sheets influences the local inhomogeneities of the ZnO deposit during the early stages of growth in terms of both, stoichiometry and morphology. Finally, as a proof of concept, it is shown how altering the initial chemical state and interaction of Graphene with Cu can be used to control the properties of the ZnO deposits.

Temperature-Dependent Photoluminescence of ZnO Thin Films Grown on Off-Axis SiC Substrates by APMOCVD.

The growth of high-quality ZnO layers with optical properties congruent to those of bulk ZnO is still a great challenge. Here, for the first time, we systematically study the morphology and optical properties of ZnO layers grown on SiC substrates with off-cut angles ranging from 0° to 8° by using the atmospheric pressure meta–organic chemical vapor deposition (APMOCVD) technique. Morphology analysis revealed that the formation of the ZnO films on vicinal surfaces with small off-axis angles (1.4°–3.5°) follows the mixed growth mode: from one side, ZnO nucleation still occurs on wide (0001) terraces, but from another side, step-flow growth becomes more apparent with the off-cut angle increasing. We show for the first time that the off-cut angle of 8° provides conditions for step-flow growth of ZnO, resulting in highly improved growth morphology, respectively structural quality. Temperature-dependent photoluminescence (PL) measurements showed a strong dependence of the excitonic emission on the off-cut angle. The dependences of peak parameters for bound exciton and free exciton emissions on temperature were analyzed. The present results provide a correlation between the structural and optical properties of ZnO on vicinal surfaces and can be utilized for controllable ZnO heteroepitaxy on SiC toward device-quality ZnO epitaxial layers with potential applications in nano-optoelectronics.

Functionalization of Commercial Electrospun Veils with Zinc Oxide Nanostructures.

The present research is focused on the synthesis of hexagonal ZnO wurtzite nanorods for the decoration of commercially available electrospun nylon nanofibers. The growth of ZnO was performed by a hydrothermal technique and for the first time on commercial electrospun veils. The growth step was optimized by adopting a procedure with the refresh of growing solution each hour of treatment (Method 1) and with the maintenance of a specific growth solution volume for the entire duration of the treatment (Method 2). The overall treatment time and volume of solution were also optimized by analyzing the morphology of ZnO nanostructures, the coverage degree, the thermal and mechanical stability of the obtained decorated electrospun nanofibers. In the optimal synthesis conditions (Method 2), hexagonal ZnO nanorods with a diameter and length of 53.5 nm ± 5.7 nm and 375.4 nm ± 37.8 nm, respectively, were obtained with a homogeneous and complete coverage of the veils. This easily scalable procedure did not damage the veils that could be potentially used as toughening elements in composites to prevent delamination onset and propagation. The presence of photoreactive species makes these materials ideal also as environmentally friendly photocatalysts for wastewater treatment. In this regard, photocatalytic tests were performed using methylene blue (MB) as model compound. Under UV light irradiation, the degradation of MB followed a first kinetic order data fitting and after 3 h of treatment a MB degradation of 91.0% ± 5.1% was achieved. The reusability of decorated veils was evaluated and a decrease in photocatalysis efficiency was detected after the third cycle of use.

Self-assembly nuclei with a preferred orientation at the extended hydrophobic surface toward textured growth of ZnO nanorods in aqueous chemical bath deposition

Textured growth of ZnO nanorods with no restriction of the substrate material is beneficial to their applications. The approaches to grow ZnO nanorods with texture are based on preparing suitable surface structure on the growth substrate, e.g. using a crystalline substrate with a specific surface structures or pre-depositing seed layers by high-temperature annealing of precursors. In the aqueous nutrient solution of the chemical bath deposition (CBD) process for ZnO growth, the concentration of Zn2+ ions at the extended hydrophobic surface is sufficiently high for forming self-assembly nuclei with a preferred orientation, resulting in the subsequent textured growth of ZnO nanorods. In this research, the hydrophobic surface is prepared by modifying Si surface with a self-assembly octadecyltrimethoxysilane (OTMS) monolayer. The formation mechanism of the nuclei on this hydrophobic surface for the textured growth of ZnO nanorods is investigated. It is shown that the nuclei form at the beginning of the CBD process and later transform into the Wurtzite structure to seed ZnO growth. An alternative approach to prepare seed layers is therefore involved in the aqueous CBD process, which is applicable to a range of hydrophobic substrates for textured growth of ZnO nanorods.

Effective control of solution self-assembly of P3HT/zinc salt complex for in situ template synthesis of P3HT/ZnO nanohybrids

This study explored the detailed solution self-assembly of a P3HT/zinc salt complex system as well as the following in situ growth mechanism of ZnO nanocrystals within self-assembled nanotemplates. Through controlling the solvent selectivity and aging conditions, the geometric shape of the complex system could be directly tailored in solution, forming nanoscopic spheres or highly elongated nanofibrils. These solution self-assembled nanostructures could be efficaciously transferred onto substrates to fabricate nanostructured hybrid films through drop casting. In contrast to traditional P3HT systems with only form Ⅰ crystalline structure, nanostructured P3HT complex thin films revealed a metastable crystalline phase with overlapping alkyl side chains. The formation of this interdigitated crystalline feature could be attributed to the solvent evaporation‐induced crystallization of tightly assembled complex chains existing in solution self-assembled nanostructured domains. The nanostructured P3HT/zinc salt complex assemblies were further used as nanoreactors for the in situ growth of ZnO. As complex samples were thermally treated, a phase transformation of P3HT from the metastable crystalline phase to form Ⅰ structure as well as the formation of ZnO nanocrystals were clearly observed. Both nanospherical and nanofibrillar structured P3HT/ZnO hybrids exhibited lower photoluminescence intensity than did a P3HT/ZnO blend sample. In particular, the nanofibrillar structured hybrid provided an optimized donor/acceptor structure for exciton dissociation as well as interpenetrating nanochannels for charge transport, resulting in the most effective photoluminescence quenching effect among measured samples. We believe that our study can serve as a model system and provide guidelines for efficiently controlling the hierarchical structures of π-conjugated polymer/inorganic nanocrystal hybrids through the in situ synthesis, offering benefits for advanced photoelectronic applications.

Involvement of glucosinolates in the resistance to zinc oxide nanoparticle-induced toxicity and growth inhibition in Arabidopsis.

Zinc oxide nanoparticles (ZnO NPs) are widely used to manufacture textile fibers, synthetic rubber, and paint. However, crop yields and quality are threatened by the increased use of metallic NPs in industry, which has resulted in their accumulation in agricultural land. Many studies have shown that plants defend against biotic and abiotic stresses through the activities of metabolites and hormones. However, whether glucosinolates (GSs) are involved in plant responses to ZnO NP-related stress remains unknown. In this study, wild-type (WT) and GS mutant (myb28/29 and cyp79B2/B3) Arabidopsis plants were subjected to ZnO NP stress to address this question. Our results showed that exposure to ZnO NPs promoted GS accumulation and induced the relative messenger RNA (mRNA) expression levels of GS biosynthesis-related genes. Moreover, ZnO NP treatment adversely affected root length, the number of lateral roots, chlorophyll contents, and plant biomass. Importantly, our results showed that root growth, chlorophyll contents, and plant biomass were all decreased in the GS mutants compared with those in WT plants. Overall, our results showed that WT plants tolerated ZnO NP-induced stress more efficiently than the GS mutants, suggesting that GSs are involved in plant resistance to ZnO NP-induced toxicity.

Comparison of Thermoelectric Properties of ZnO and ZnSnO Thin Films Grown on Si Substrate by Thermal Evaporation

In this manuscript, we compared the thermoelectric properties of ZnO and ZnSnO thin films grown on silicon (100) substrate. We have evaporated Zn and Sn+Zn metal powders were evaporated in vacuum tube furnace alternatively, under same experimental conditions for the growth of ZnO and ZTO respectively. After the deposition, these grown films were cut into pieces and post growth annealed at different annealing temperatures from 600oC to 800oC in the air using programmable muffle furnace. Seebeck and Hall data suggested that ZTO sample shows highest value of Seebeck coefficient, electrical conductivity and power factor as compared to the ZnO samples. It is also observed that the value of Seebeck coefficient showing an increasing trend for both of the samples as we increase the post growth annealing temperature. The higher thermoelectric properties for ZTO are due the presence of Sn atoms in ZnO structure. Tin dopants may generate secondary phases and/or enhanced the carrier mobility which might be the reason that ZTO has improved thermo-electric properties as compared to ZnO. XRD and Raman measurements were used to confirm the formation of ZTO. XRD data verified the hexagonal structure of ZnO but a slight red shift is observed for the case of ZTO samples. To further justify our argument, we have also performed Raman spectroscopy measurements which confirmed the presence of Sn elements in ZTO.

RBS and NRA analysis for films with high growth rate prepared by atomic layer deposition

We present the design and operation of a specialized Atomic Layer Deposition (ALD) system, dedicated to stable isotopic tracing experiments of oxide film growth, using isotopically labelled water as the oxide reactant. A small chamber volume allows operation with only very small quantities of water vapor, minimising the consumption of the isotopically labelled water. The first results for growth of ZnO and TiO2 using Diethlyzinc (DEZ) and Tetrakis(dimethylamino)titanium (TDMAT) as the zinc and titanium precursors, and unlabelled water as reactant, are presented, to establish the growth conditions for stoichiometric ZnO and TiO2 on silicon. Absolute film compositions and thickness are determined by RBS and NRA as a function of vapor pulse duration, number of ALD cycles and substrate temperature. Physical thickness is determined by ellipsometry. The first results obtained for growth of ZnO using water highly enriched in 18O are also presented.

Experimental investigation and comparative analysis of electron beam evaporated ZnO/MgxZn1-xO/CdxZn1-xO thin films for photodiode applications

— This work reports the growth optimization and analysis of ZnO, Mg x Zn 1-x O, and Cd x Zn 1-x O thin films on silicon substrate using an electron beam evaporation system. The crystal phase purity, surface morphology, optical and electrical properties of deposited ZnO, Mg x Zn 1-x O, and Cd x Zn 1-x O thin films were studied. X-ray diffraction (XRD) spectra revealed that the deposited films were polycrystalline in nature with preferred (002) crystal orientation. Field emission scanning electron microscope study showed a dense-packed grained structure with an exact symmetrical distribution. The root-mean-square roughness of 3.03 nm was perceived by atomic force microscopy measurement for Mg x Zn 1-x O thin-film, indicating good morphology of the deposited film. Photoluminescence measurement demonstrated a near-band-edge emission peak around 363 nm for ZnO thin film. The energy band gap obtained for ZnO, Mg x Zn 1-x O, and Cd x Zn 1-x O were 3.36 eV, 3.86 eV, and 2.89 eV, respectively, as measured by Ultraviolet–Visible spectroscopy. The higher amount of photocurrent was detected in illumination condition compared to dark condition with responsivity 0.54 AW -1 for ZnO films, making it suitable for photodiodes applications. • The growth and characterization of ZnO, Mg x Zn 1−x O, and Cd x Zn 1−x O on a silicon substrate using an electron beam evaporation technique is presented. • From IV characteristics measured in dark and under illumination, it was inferred that ZnO based alloys are sensitive to light and can be utilized for fabricating photodiodes.

In-situ growth of ultrafine ZnO on g-C3N4 layer for highly active and selective CO2 photoreduction to CH4 under visible light

Photocatalytic CO2 reduction to solar fuels is considered as a promising strategy to address the global warming and energy shortages. Herein, a novel method is proposed to prepare g-C3N4/ZnO nanocomposites via refluxing zinc salt methanol solution containing pre-formed g-C3N4 with KOH methanol solution as precipitating agent. Some in-situ grown ultrafine ZnO nanoparticles are decorated on ultrathin g-C3N4 layers with well-defined interface, which not only causes efficient charge transfer and separation, but also creates more active sites for CO2 adsorption and activation. The resultant g-C3N4/ZnO composites demonstrate significant enhanced CO2 photoreduction activity and selectivity for CH4 production under visible light irradiation, and the optimal g-C3N4/ZnO composite delivers the best overall photoactivity (158.4 μmol g−1 h−1) with CH4/CO production rates of 19.8/0.37 μmol g−1 h−1, which is 9.42 times higher than that of g-C3N4 alone. This work provides an ideal synthetic strategy for g-C3N4-based hybrid materials with highly efficient CO2 photoreduction.

Effect of Electrolyte Concentration on Epitaxial Growth of ZnO on Cu Substrates through Electrochemical Deposition

The roles of zinc and nitrate ions in the electrochemical growth of ZnO were examined in this study. ZnO was deposited on a polycrystalline Cu substrate from electrolyte containing 0.0025–0.08 M zinc nitrate and 0.1–2.0 M potassium nitrate. The morphology, epitaxial orientation relationship, interfacial microstructure, and photoluminescence (PL) properties of the ZnO deposits were characterized. The ZnO morphology was found to be controlled mostly by the zinc ion concentration in the electrolyte. Here, 50–400 nm wide hexagonal pillars were deposited from electrolyte with potassium nitrate concentration as high as 0.4 M. All the deposited films had strong 〈0001〉//ND fibre texture. Most of the ZnO crystallites were grown epitaxially on Cu grains regardless of the electrolyte concentration. The major epitaxial orientation relationship was identified as (0001)ZnO//(103)Cu and [11 0]ZnO//[010]Cu, and three other epitaxial orientation relationships were also identified. Samples consisting of nanopillars or plates exhibited excellent PL characteristics with near bandgap–deep level emission intensity ratios of 2.4–4.3 and full width at half maximum of the NBE peak of 122–131 meV.

Growth and Characterization of ZnO and Al-Doped ZnO Thin Films by a Homemade Spray Pyrolysis

In this work, we have prepared the undoped and Al-doped ZnO thin films by a homemade spray pyrolysis method at 450°C onto glass substrates. The X-ray diffraction patterns of undoped ZnO and aluminized zinc-oxide (AZO) thin films exhibit hexagonal wurtzite crystal structure with high crystalline quality, the crystallite size is nanometric. The morphology of the undoped and Al-doped ZnO thin films also indicate that all samples have a nanoscale grain size around 50 nm, and the microstructure of ZnO films is highly influenced by the aluminum doping. The two films are characterized by UV-visible spectrophotometry showing that the films have a whole optical transmission above 85% in the visible range. The composition of our films is obtained by energy dispersive spectrum, confirmed by Auger electron spectroscopy (AES) and by Rutherford back-scattering spectrometry (RBS) techniques.