F-doped ZnO Research Articles

Synthesis and Characterization of Optically Transparent and Electrically Conductive Mo-Doped ZnO, F-Doped ZnO, and Mo/F-Codoped ZnO Thin Films via Aerosol-Assisted Chemical Vapor Deposition

Synthesis and Characterization of Optically Transparent and Electrically Conductive Mo-Doped ZnO, F-Doped ZnO, and Mo/F-Codoped ZnO Thin Films via Aerosol-Assisted Chemical Vapor Deposition

Effect of fluorine doping on the improvement of electrical and photocatalytic properties of ZnO films

ZnO:F thin films were produced by ultrasonic spray pyrolysis (USP) technique. For photovoltaic and photocatalytic applications, the properties of ZnO films have been tried to be improved by adding the flourine (F) element. The average optical transmittance was higher than 85%. Photoluminescence (PL) spectra depict blue, green and yellow emission in deposited films. Photocatalytic activity of ZnO and ZnO:F thin films was evaluated with methylene blue (MB) organic pollutant under UV irradiation. 5% doped ZnO:F film successfully decomposed ~ 80% using MB as photocatalyst. The lowest resistivity (3.54 × 10–3 Ωcm), high carrier concentration (2.52 × 1020 cm−3) and high hall mobility (8.28 cm2V−1 s−1) were observed in ZnO:F (5%) film. With this study, it was concluded that F-doped ZnO films were effective in the degradation of MB, which is widely used in the food and pollutant industries. Therefore, it makes ZnO:F films a promising material in both optoelectronic and photocatalytic applications due to their optimum properties.

High-concentration F-incorporated ZnO thin films doped via femtosecond-laser hyperdoping

ZnO is a transparent conductive oxide that has received great attention over the past few decades, as it is a key component in light-emitting diodes, gas sensors, and solar cells. However, the electrical conductivity of intrinsic ZnO is not ideal, and thus, ZnO is often doped with appropriate elements such as fluorine (F). Unfortunately, the lack of adequate precursors in traditional doping methods may increase the difficulty of ZnO doping with F. In this work, we realized, for the first time, high-concentration F-doped ZnO thin films with a high Hall mobility of 20.7 cm2/V/s via femtosecond-laser hyperdoping. The highest atomic percentage of F was determined to be 8.3 at.%, which was over three times larger than that of previously reported F-doped ZnO films. Compared with pristine ZnO, the highest carrier concentration of the F-doped ZnO could be increased by four orders of magnitude, and the resistivity could be reduced by three orders of magnitude. Our results demonstrated that the femtosecond-laser hyperdoping technology could achieve efficient non-metallic hyperdoping of ZnO with high transparency and Hall mobility, thereby reducing the power dissipation and improving the current carrying capacity of ZnO-based devices.

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.

Near room-temperature synthesis of transparent conducting fluorine-doped ZnO thin films as window layer for solar cells

Highly transparent and conducting fluorine-doped ZnO (FZO) thin films were developed by 13.56 MHz RF magnetron sputtering near room-temperature (∼45 °C) on glass substrates. The effects of sputtering gas pressures in the range (10–40) mTorr were studied on the morphological, electronic, and optical characteristics of the FZO thin films. At a plasma pressure of 20 mTorr, the optimum FZO films were obtained with a wide optical band gap Eg ∼3.28 eV and high electrical conductivity of ∼102 S cm−1 via minimization of strain in the network containing 1.2 at.% F. A structurally favored c-axis orientated F-doped ZnO network has been achieved with an average grain size of ∼29 nm, high electrical mobility, μ ∼13 cm2 V−1 s−1 and carrier concentration, ne ∼1020 cm−3 that provided an excellent conduction channel for the stacked-layer devices. Using the optimized FZO films as a transparent conducting (TCO) window layer of the nc-Si solar cell in ‘Glass/FZO/p-nc-SiOX:H (∼20 nm)/i-nc-Si (∼2000 nm)/n-a-Si:H (∼30 nm)/Ag/Al’ configuration, a photovoltaic conversion efficiency (η) of 5.68% with short-circuit current density, JSC ∼13.36 mA cm−2, fill factor, FF ∼58.4%, and open-circuit voltage, VOC ∼727.5 mV was obtained.

Structural characteristics, impedance spectroscopy, ac-conductivity and dielectric loss studies on RF-magnetron sputtered F doped ZnO (FZO) thin films

The manuscript demonstrates the structural characteristics, impedance spectroscopy, ac-conductivity and dielectric loss studies on F-doped ZnO films grown by RF-magnetron sputtering at TS ∼50 and 125 °C. The electrical impedance spectroscopy enables separately recognizing the contributions of grain and grain-boundary on the electronic properties. The relaxation time distribution on temperature results in the asymmetric and depressed nature of the semi-circular arcs in the Cole-Cole plot and endorses a non-Debye type response under changing electric fields. The negative temperature coefficient of resistance behaviour indicates the semiconducting characteristics. A parallel equivalent circuit model (R || CPE) is designed to fit the semi-circular arc. The grain boundary being more resistive than ZnO-grain, its activation energy appears more significant because of the dynamic disorder characteristics. The ac-conductivity obeys Jonscher power law, and frequency exponent n < 1 suggests hopping of charge carriers with translation motion under ac electric field. The temperature-dependent dc-conductivity follows the Arrhenius behaviour. Sample deposited at higher TS has a greater carrier lifetime due to the improved crystalline structure and lesser defects. Although, the dielectric loss in the form of conduction loss is higher for the low temperature grown sample owing to the relatively effortless movement of charge carriers and formation of dipoles due to its elevated dc conductivity consequent to increased doping.

Molluscicidal and biochemical effects of green-synthesized F-doped ZnO nanoparticles against land snail Monacha cartusiana under laboratory and field conditions

The glass clover snail, Monacha cartusiana (M. cartusiana) is one of the most seriously impacting economic animal pests spreading across Egypt which inflicts severe damages to the agriculture. A green route is developed by deploying an abundant Rosemary plant leaves aqueous extract to synthesize ZnO and F-doped ZnO (F–ZnO) nanoparticles (NPs) that display high molluscicidal activities against the M. cartusiana land snails via leaf dipping and contact techniques. The effect of lethal concentrations, that kills 50% of exposed snails (LC50) value of the treatments, is examined on the activity of alkaline phosphatase (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), enzymes, total protein (TP), total lipids (TL) and cholesterol level of snails, including the histopathological evaluation of the digestive gland and foot of M. Cartusiana. Their molluscicidal activity as poisonous baits under field conditions is also evaluated and compared to the recommended molluscicide, Neomyl. The results show that F− doping dramatically improves the snail control capability of ZnO NPs, and promotes a considerable increase in both ALT and AST enzymes with an enhancement of TL and Cholesterol levels, but a significant decrease in TP content and ALP activity in treated snails compared to the control group. The LC50 values are found to be 1381.55 and 2197.59 ppm using the leaf dipping for F–ZnO and ZnO, while 237.51 and 245.90 ppm can be achieved using the contact technique, respectively. The greenly synthesized F–ZnO and ZnO NPs induce severe histological alterations in the digestive gland and foot of M. cartusiana, including a complete destruction of the digestive tubules. The histological evaluation of the foot of M. cartusiana exposed to ZnO, shows a rupture of the epithelial layer of the foot sole, while F– ZnO NPs causes the folds of the foot becoming deeper and the rupture of epithelial layer. Our field experiments further demonstrate that F–ZnO achieves 60.08% reduction, while ZnO attains 56.39% diminution in snail population compared to the commercial, Neomyl (69.55%), exhibiting great potentials in controlling the harmful land snail populations.

High-mobility sputtered F-doped ZnO films as good-performance transparent-electrode layers

Point-defect engineering is an effective way to control the mobility and transparent-conducting performance of sputtered fluorine-doped ZnO (FZO) thin films. In this study, doping with fluorine (F) is accomplished through a simple one-step deposition process and is demonstrated to enhance the crystal quality, eliminate the point defects, and boost the mobility as well as the performance of the films. Furthermore, the films’ characteristics are observed to be strongly dependent on F content. At the optimum F content of 1%, the FZO films exhibited the best crystal quality and the lowest concentration of Zn interstitial and O vacancy defects due to F passivation. Moreover, a mobility as high as 45.3 cm 2 /V and the greatest figure-of-merit performance are achieved for cutting-edge transparent electrode applications. However, a further increase of F content brought about an increased concentration of defects relating to Zn vacancies, especially F interstitials, which yielded the low mobility and poor performance due to the degraded structure.

Synthesis and optical analysis of nanostructured F-doped ZnO thin films by spray pyrolysis: Transparent electrode for photocatalytic applications

In this paper, spray pyrolysis as a valuable cost-effective deposition technique was used to obtain nanostructured thin films of ZnO and ZnO: F on soda-lime glass substrates at 400 °C. The crystal structure and surface morphology of the as-deposited thin films have been characterized by the X-ray diffraction (XRD) technique and high-resolution atomic force microscope (AFM). XRD patterns indicated the wurtzite hexagonal structure of the deposited films with mean grain size in nanoscale. AFM and XRD confirmed that the mean grain size of ZnO film was increased with the F doping level. The optical parameters like refractive index, absorption coefficient, and optical bandgap have been obtained through Swanepoel's model depending on the transmission spectra of the deposited films. The direct optical band gap of ZnO film was slightly decreased with the F doping level. The single oscillator model was applied to determine the dispersion parameters of the films under study. The photocatalytic activity of the ZnO and ZnO: F thin films for the phenol photodegradation under UV-irradiation also has been evaluated to purify water from phenol as colorless organic waste. 3%F doped ZnO film has the highest constant rate of phenol photodegradation with high stability in reusing and recycling, confirming the high efficiency of F doped ZnO films as environmentally friendly photocatalysts for the removal of phenol from water.

F-doped ZnO nano- and meso-crystals with enhanced photocatalytic activity in diclofenac degradation

Diclofenac (DCF), a non-steroidal anti-inflammatory drug, is considered one of the most widespread emerging contaminants. Its incidence in water can favor the growth of drug-resistant bacteria and harm aquatic organisms endangering both the human health and the ecosystem. Advanced oxidation processes (AOPs) based on the action of reactive oxygen species are very effective technologies for the removal of this contaminant from water. In this context, ZnO is one of the most studied semiconductors for photocatalytic water treatment.In this work, the photocatalytic activity of fluorine-doped ZnO nano- and meso-crystals synthesized by a hydrothermal approach is reported, exploring the role of a low F atomic concentration (0.25, 0.5 and 1 at. %) on the degradation of DCF in comparison with bare ZnO. All doped samples show high rates of DCF degradation and mineralization, which were realized primarily thanks to their high efficiency in the generation of hydroxyl radicals (OH). The property-structure-function relationships of the materials are investigated by complementary techniques, such as SEM, XRD, EPR, UV–vis DRS and PL, with the aim to evaluate the role of fluorine in determining their morphological, electronic and optical properties.

NO2 sensing properties of N-, F- and NF co-doped ZnO nanoparticles

Zinc oxide nanoparticles (ZnO NPs) doped with N and F ions were prepared by a simple sol-gel technique in the presence of various additives. The morphology and microstructure of the synthesized nanoparticles were characterized by means of SEM, XRD, BET surface area, UV–Vis-DRS, micro-Raman and photoluminescence. Characterization data highlighted the microstructural changes subsequent to introduction of the dopants into the lattice structure of ZnO nanoparticles. Conductometric gas sensors based on the N-doped ZnO, F-doped ZnO and NF co-doped ZnO NPs synthesized were fabricated and tested in the monitoring of low concentrations of NO2 in air. The effect of the different dopants on the sensing properties have been investigated and correlated with the morphological and microstructural characteristics. The impact of UV–Vis irradiation (λ = 400 nm) on the sensors performances was also studied. Results obtained have demonstrated that N-doped ZnO sensor displays the best NO2 sensing performances in dark and furthermore can be activated under UV–Vis irradiation to operate effectively at room temperature (RT).

Effect of anionic fluorine incorporation on structural, optical and electrical properties of ZnO nanocrystalline films

ZnO and ZnO:F (fluorine doped Zinc oxide) films have been deposited on glass substrates at 325 ± 5 °C through ultrasonic spray pyrolysis method (USP). X-ray diffractometer (XRD) has been utilized to determine the crystal structural and some structural parameters such as lattice constants, texture coefficients TC (hkl), crystallite size and dislocation densities of all the ZnO films. The XRD results have revealed that all the ZnO films have the hexagonal wurtzite structure and F incorporation shows no significant effect on the crystal structure. X-ray photoelectron spectroscopy (XPS) measurements have confirmed the presence of fluorine atoms in the ZnO lattice and also the existence of Zn–F bonding states. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) measurements have been carried out to investigate the effect of F doping on the surface morphology of the ZnO films. The optical properties of the films have been analyzed by utilizing transmittance, absorbance and reflectance measurements. Some optical parameters such as extinction coefficient (k), refractive index (n) and optical conductivity have been determined depending on the change in F incorporation. Increasing the F doping initially led to a decrease in the optical band gap, but later increased. Electrical resistivity and carrier concentration values of the deposited films have been determined with Hall effect measurement system and it has been detected that 6% F-doped ZnO film has the minimum resistivity and maximum carrier concentration.

Solar photocatalytic degradation of diclofenac aqueous solution using fluorine doped zinc oxide as catalyst

The photocatalytic degradation of a sodium diclofenac (DCF) solution (10 mg/L) under simulated solar radiation was evaluated using a ZnO semiconductor modified by the incorporation of 10, 15, and 20 wt.% fluorine (ZnO-F10, ZnO-F15 and ZnO-F20). The ZnO-F catalysts were synthesized by the sol-gel method using zinc acetate as a precursor of zinc oxide and NH4F as a fluorine source. The photocatalytic performance of the F-doped ZnO material was compared to that of bare ZnO. The obtained photocatalysts were characterized using X-ray diffraction (XRD), Scanning electron microscopy with Energy dispersive spectroscopy (SEM-EDS) and X-ray photoelectron spectroscopy (XPS) techniques. The Brunauer-Emmett-Teller (BET) surface area, pH of zero charge (pHpzc), and band gap of the solids were also evaluated. An experimental Box-Behnken design combined with response surface methodology was applied to establish the optimal conditions for the photocatalytic degradation of the DCF solution. Complete DCF degradation, total release of chloride ions, and approximately 90% mineralization were achieved during degradation of the drug at an accumulated energy of 400 kJ/m2 under the optimized experimental conditions (1 g/L of ZnO-F20 catalyst with the pH of the DCF solution maintained at 6.5).

Photoelectric properties of F-doped ZnO thin films prepared by sol-combustion

ABSTRACTIn this study, fluorine-doped ZnO (FZO) transparent conductive film was prepared using sol-combustion method at a low temperature. The optimized synthesis conditions were evaluated based on the analysis of crystal structure, morphology, and photoelectric properties. The results of X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–visible absorption spectroscopy (UV–vis), and Hall test (HALL) show that under the optimal ratio of precursor solution and optimal doping concentration (10%), the sol-combustion method can produce FZO transparent conductive film with a higher transmittance (80%), higher conductivity (36.9 Ω cm), and better crystalline quality and surface morphology at a relatively low temperature of 250°C. The FZO films produced using sol-combustion method have good application prospect.

Synthesis and Surface Modification of Nanostructured F-Doped ZnO: Toward a Transducer for Label-Free Optical Biosensing

In this work, the surface of nanostructured fluorine-doped ZnO (nZnO·F) is functionalized with protein A (PrA), and used as a model biomolecule. The chemical procedure is characterized by several analytical techniques such as Fourier Transform Infrared Spectroscopy, water contact angle analysis, and fluorescence microscopy. The surface modification of nZnO·F by binding increasing concentrations of PrA is also investigated by two label-free optical techniques, i.e., the spectroscopic reflectometry and the steady-state photoluminescence. The results are compared with those obtained using undoped nZnO substrates in order to highlight the better performances of nZnO·F due to the fluorine doping. The results of this study pave the way for the design and realization of a ZnO-based nanostructured platform for label-free optical sensing.

Effect of deposition temperature and F2 flow rate on the characteristics of F-doped ZnO films

In this study, we would investigate the fluorine (F)-doped ZnO films (FZO) using radio frequency (RF) magnetron sputtering method at room temperature (RT) and [Formula: see text]. At first, ZnO powder was used to form the ZnO ceramic target. The F2 flow rate [Formula: see text] was changed in the range of 0–0.25%, and the F2 ratio was controlled using the mixing gases of (F2(5%) + 95% Ar) and pure Ar. FZO films were deposited on the EagleXG glass (Corning) and the films’ thickness was about 330 nm by controlling the deposition time. After the FZO films were deposited, their crystalline structure and optical and electrical characteristics were well investigated as a function of deposition temperature and F2 flow rate. We would prove that the characteristics of the [Formula: see text]-deposited FZO films were better than those of the RT-deposited FZO films.

Fluorine-doped ZnO (FZO) films produced by corona-discharge-assisted ultrasonic spray pyrolysis and hydrogenation as electron-selective contacts in FZO/SiOx/p-Si heterojunction crystalline silicon solar cells with 11.7% efficiency

In this paper, we report the fabrication of an F-doped ZnO (FZO)/SiOx/(pp+)Cz-Si heterostructure by growing thin FZO films on (pp+)Cz-Si substrates by a novel, corona-discharge-assisted ultrasonic spray pyrolysis (CDA-USP) technique in combination with post-deposition annealing in hydrogen. We examine the effect of the F/Zn ratio and acetic acid concentration in film-forming solution on the structure, morphology, growth rate, and electrical properties of the FZO films and on the photovoltaic properties of FZO/SiOx/(pp+)Cz-Si structures. Under 1-sun illumination, a solar cell produced using the FZO/SiOx/(pp+)Cz-Si structure has an open-circuit voltage of 542 mV, a short-circuit current of 35.3 mA/cm2, and a solar cell efficiency (referred to the total area) of 11.7%, the highest value reported to date for TCO/Si heterojunction solar cells with ZnO-based TCOs.

EFFECT OF SEEDING FILM TYPE ON MORPHOLOGY AND ELECTRICAL PROPERTIES OF Ga-DOPED ZnO NANOSTRUCTURES GROWN BY HYDROTHERMAL PROCESS

In the present work, we are interested in modifying the structures and electrical properties of Ga-doped ZnO (GZO) nanostructures by incorporation of Ga and F elements into ZnO seeding films. The ZnO, Ga-doped ZnO and F-doped ZnO thin film layers were grown by sol–gel dip coating onto glass substrates. The GZO nanostructures were grown by hydrothermal method starting from zinc nitrate and gallium (III) nitrate hydrate with a crystal growth assistance using the different types of seeding film layers. The X-ray diffractometer (XRD) and field emission scanning electron microscope (FE-SEM) are observe for the crystal structures and surface morphologies of GZO nanostructures. The changes in electrical resistance of the GZO nanostructures due to the different seeding layers were analyzed by the four-point probe technique. It is shown that the structural and electrical properties are found to be affected by the types of seeding layers.

Using Oxygen Plasma Pretreatment to Enhance the Properties of F-Doped ZnO Films Prepared on Polyimide Substrates

In this study, a radio frequency magnetron sputtering process was used to deposit F-doped ZnO (FZO) films on polyimide (PI) substrates. The thermal expansion effect of PI substrates induces distortion and bending, causing FZO films to peel and their electrical properties and crystallinity to deteriorate. To address these shortcomings, oxygen (O2) plasma was used to pretreat the surface of PI substrates using a plasma-enhanced chemical vapor deposition system before the FZO films were deposited. The effects of O2 plasma pretreatment time on the surface water contact angle, surface morphologies, and optical properties of the PI substrates were investigated. As the pretreatment time increased, so did the roughness of the PI substrates. After the FZO films had been deposited on the PI substrates, variations in the surface morphologies, crystalline structure, composition, electrical properties, and optical properties were investigated as a function of the O2 plasma pretreatment time. When this was 30 s, the FZO films had optimal optical and electrical properties. The resistivity was 3.153 × 10−3 Ω-cm, and the transmittance ratios of all films were greater than 90%. The X-ray photoelectron spectroscopy spectra of the FZO films, particularly the peaks for O1s, Zn 2p1/2, and Zn 2p3/2, were determined for films with O2 plasma pretreatment times of 0 and 30 s. Finally, a HCl solution was used to etch the surfaces of the deposited FZO films, and silicon-based thin-film solar cells were fabricated on the FZO/PI substrates. The effect of O2-plasma pretreatment time on the properties of the fabricated solar cells is thoroughly discussed.

Effect of F incorporation on physical and optical properties of hydrothermally grown ZnO nanorods

F-doped ZnO nanorods were synthesized via hydrothermal process with variation of Fluorine doping contents (0-10%) starting from zinc oxide thin film as a seeding layer for nanorod growth. The zinc oxide seeding thin film was prepared by sol-gel spin coating at 2000 rpm on glass substrate using zinc acetate precursor with annealing at 500°C in air for 2 h. Ammonium fluoride (NH4F) was used as F doping precursor. The properties of F-doped ZnO nanorods were characterized by field emission electron microscope (FESEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX) and UV-Visible spectrophotometer. Corresponding results indicated that growth of ZnO:F nanorods with good crystallinity and grown in (002) plane in undoped ZnO and F-doped ZnO 5%. The average size diameter of undoped and F-doped ZnO nanorods at 3%, 5% and 10% are 56, 96, 70 and 103 nm, respectively. From cross section images the average length of undoped and F-doped ZnO nanorods at 3%, 5% and 10% are 400, 375, 199 and 478 nm, respectively. The transmittance spectra shows moderate transparency (<80%) of the ZnO nanorod film in visible region with corresponding band gap range of 3.25-3.28 eV.