Ag-doped ZnO Thin Films Research Articles

Investigating the role of Ag-doped ZnO thin films in UV photodetectors produced via laser assisted chemical bath growth technique

This study introduces the innovative fabrication of Ag-doped ZnO thin films (AgxZnO(100−x) TFs) with varying silver (Ag) concentrations (x) of 0.5, 1.0, 1.5, and 2.0 at% on glass substrates using a simple and cost-effective method known as laser-assisted chemical bath growth (LACBG). This process aims to create metal-semiconductor-metal (MSM) ultraviolet (UV) photodetectors. A continuous wave semiconductor laser with a 444.5 nm wavelength, 5 W power, and 6 min irradiation time was employed to synthesize high-quality Ag-doped ZnO TFs on the glass substrate. Ag electrodes were utilized as Schottky contacts to form MSM UV photodetectors. Structural and morphological analyses conducted using XRD and SEM revealed vertically aligned nanorods and nanoflowers with a high c-axis orientation and hexagonal wurtzite facets, while EDX confirmed Ag incorporation into the ZnO lattice. The UV–Visible absorbance spectra indicated a decrease in bandgap from 3.28 to 2.84 eV with increased Ag content. The current-voltage (I–V) characteristics of the Ag-doped ZnO TFs UV photodetector showed significantly enhanced conductivity at a 2.0 at% concentration level, achieving a responsivity of 10.78 A/W, an external quantum efficiency of 34.67 % at −3 V bias voltage. Finally, the modified device exhibited a sensitivity of 14661.9 %, a gain of 147.62, and a detectivity of 2.25 ×107 Jones, demonstrating its suitability for optoelectronic applications.

Evaluation of the effect of Ag- doping ZnO microstructure on optical and structural properties and application in photocatalytic properties

The chemical bath deposition technique was successful in producing silver-doped ZnO thin films. On the glass substrates, pure and silver-doped ZnO thin films have been deposited. By using a variety of sophisticated techniques, including X-ray Diffraction (XRD), Field emission Scanning Electron Microscope (FESEM), UV-vis spectrophotometer, and photoluminescence (PL) spectroscopy, the generated pure and Ag-doped ZnO thin films were studied. According to X-ray analysis, Ag-doped ZnO crystallized as a hexagonal wurtzite structure with a preference for growth in the (002) planes, the pure and Ag-doped ZnO's hexagonal wurtzite structures provided evidence for the microparticles' luminescent characteristics. The analysis of the methylene blue degradation revealed that the best photocatalytic response was displayed by the doped ZnO thin film. All thin films' optical bandgaps were broad, and they generally decrease after more doping, it was possible to determine that the particles were elliptical and rod-shaped and that their diameters were on the order of micrometers. for both the doped and pure ZnO microparticles were seen to exist. The outcome shows that the produced microparticles' average grain diameter was determined to be (15,20.5,14.5) um, with noteworthy band gaps of 3.39,3.34 eV, and 3.08 eV, respectively.

Ag Doped ZnO Thin Films Deposited by Spin Coating for Silicon Surface Passivation

Ag Doped ZnO Thin Films Deposited by Spin Coating for Silicon Surface Passivation

Development of Ag-Doped ZnO Thin Films and Thermoluminescence (TLD) Characteristics for Radiation Technology.

This work examined the thermoluminescence dosimetry characteristics of Ag-doped ZnO thin films. The hydrothermal method was employed to synthesize Ag-doped ZnO thin films with variant molarity of Ag (0, 0.5, 1.0, 3.0, and 5.0 mol%). The structure, morphology, and optical characteristics were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), photoluminescence (PL), and UV–vis spectrophotometers. The thermoluminescence characteristics were examined by exposing the samples to X-ray radiation. It was obtained that the highest TL intensity for Ag-doped ZnO thin films appeared to correspond to 0.5 mol% of Ag, when the films were exposed to X-ray radiation. The results further showed that the glow curve has a single peak at 240–325 °C, with its maximum at 270 °C, which corresponded to the heating rate of 5 °C/s. The results of the annealing procedures showed the best TL response was found at 400 °C and 30 min. The dose–response revealed a good linear up to 4 Gy. The proposed sensitivity was 1.8 times higher than the TLD 100 chips. The thermal fading was recorded at 8% for 1 Gy and 20% for 4 Gy in the first hour. After 45 days of irradiation, the signal loss was recorded at 32% and 40% for the cases of 1 Gy and 4 Gy, respectively. The obtained optical fading results confirmed that all samples’ stored signals were affected by the exposure to sunlight, which decreased up to 70% after 6 h. This new dosimeter exhibits good properties for radiation measurement, given its overgrowth (in terms of the glow curve) within 30 s (similar to the TLD 100 case), simple annealing procedure, and high sensitivity (two times that of the TLD 100).

Ag-doped ZnO hydrogen sensor grown by the USP method

Undoped and Ag doped ZnO thin films were grown on glass substrate at 500 °C by ultrasonic spray method (USP). In order to observe the effect of Ag doping on ZnO thin films, doping rates of 0.5%, 1%, 2%, 3% and 4% were carried out. Some measurements were taken to investigate the effects of Ag dopant for example Uv–Vis spectroscopy and photoluminescence (PL) measurements for optical, scanning electron microscope (SEM) measurements for morphological, X-ray Diffraction (XRD) and Energy Dispersive X-ray spectroscopy (EDAX) measurements for structural, sensor measurements for H2 sensor properties. Uv–Vis spectroscopy and photoluminescence (PL) measurements show that the band gap of ZnO decreased from 3.21 eV to 2.79 eV and PL intensity of ZnO from 3.21 eV to 2.79 eV with increasing amount of Ag dopant. SEM measurements show that surface morphology changed and shrinkage was observed on the surface with Ag dopant. XRD results show that the presence of Ag peaks was found in the crystal structure of Ag doped ZnO thin films and EDAX measurements have supported this AG presence in the ZnO structure. Hydrogen sensor measurements show that the sensor response decreased from 92.7% to 45.6% with the increase of Ag dopant.

Catalytic effect of Ag embedded with ZnO prepared by Co-sputtering on H2S gas sensing MEMS device

Ag doped ZnO thin films are deposited on a micro electromechanical systems (MEMS) device incorporating a microheater and sensing electrodes using a co-sputtering system. Structural properties and sensing properties were tested with pure Zn alongside with 0.15%, 0.3%, 0.5%, 1% and 2% Ag doping concentrations. The H2S gas sensing performance of the MEMS-based devices is evaluated for H2S concentrations in the range of 0.2–1.0 ppm and heating temperatures of 150–300 °C. The optimal sensing performance is obtained with a Ag concentration of 0.5% and a working temperature of 250 °C. For an H2S gas concentration of 1 ppm, the sensor achieves a sensing response of 16% and a response time of 3 s. The sensor additionally shows good selectivity for H2S gas compared to that for CO, NO2, NH3 and SO2, respectively. Finally, different response time phenomenon is explained due to the formation of Ag+ on doped ZnO surface.

Effect of annealing on the properties of transparent conducting Ag doped ZnO thin films prepared by r.f. magnetron sputtering method

Ag doped ZnO thin films were prepared by r.f. magnetron sputtering method and then heat treated at 450 °C in 2 h in different ambients (air, O2/O3). Evolution of morphology, optical and electrical properties of the as-prepared thin films upon annealing environments was studied. XRD analysis demonstrated that annealing had resulted in better crystallization as well as higher transparence. Optical absorption showed that the band gap of the films also reduced after heat treatment. The results also showed that conductivity of the films could be tuned from 10−3 Ω cm to 10+5 Ω cm by an appropriate annealing process.

Characterization of Ag-doped ZnO thin films by spray pyrolysis and its using in enhanced photoelectrochemical performances

In this work, Ag:ZnO thin films have been prepared by spraying a mixture of zinc acetate dehydrate and silver nitrate precursors on (ITO)-coated glass substrates at optimized conditions of substrate temperature and a solution concentration. In the current study, we show the effect of Ag doping on the morphological and photoelectrochemical properties of ZnO thin films. The SEM observations exhibit indeed a low change in the size of the surface crystallite after doping. For instance, we have investigated the silver doping effect on the electrochemical behavior taking place at the ZnO/electrolyte interface. The interface has been modeled as an equivalent circuit consisting of a parallel charge transfer resistance RCt and a constant phase element (CPE) in series with a resistance of electrolyte RS. An optimization of the doping percentage has shown that the ZnO photoanode doped with 2% Ag gives the best photoelectrochemical performances.

Dielectric and magnetic properties of dilute magnetic semiconductors Ag-doped ZnO thin films

Ag-doped ZnO thin films are prepared by the cost-effective sol–gel dip-coating method at room temperature. The Ag dopant percentage varies between (2–10) wt%. The magnetic and dielectric properties have been studied. The dielectric and magnetic properties of ZnO are significantly tailored by the increase in the Ag doping percentage. High dielectric constant and tangent loss have been observed at low frequencies which decreases with the increase in frequency. The AC conductivity is lower in the low-frequency region but has larger values in the high-frequency region. The ferromagnetic behavior of films has been recorded at room temperature. Magnetic polarons play a pivotal role in the development of room temperature ferromagnetism in Ag-doped ZnO thin films. So, ferromagnetism in thin films is governed by bound magnetic polarons. As the doping concentration increased, the saturation magnetization decreased and coercivity increased due to the combined effect of the decrease in crystallite size, generation of large defects, and formation of bound magnetic polarons. These Ag-doped ZnO thin films are suitable for spintronics.

Investigation of dielectric properties of Ag-doped ZnO thin films

In this study, undoped and Ag-doped ZnO thin films were grown on p-type Si substrates using Sol-Gel spin coating technique at room temperature. Optical properties, such as refractive index (n) and extinction coefficient (k) were determined using the optical data in terms of wavelength and photon energy, respectively. Depending on Ag doping concentration, some changes in optical properties thin films were observed. Also, the frequency and voltage dependence of some dielectric properties of thin films have been evaluated using the admittance spectroscopy method in the wide frequency range of 10 kHz to 1 MHz at room temperature. Experimental results show that the real (ε') and imaginary parts (ε'') of dielectric constants, loss tangent (tanδ), real (M') and imaginary (M'') parts of electric modulus were strong functions of frequency and applied bias voltage in the depletion region. The loss tangent versus applied bias voltage curves shows an increase with increasing frequencies and shifts to applied forward bias region giving a peak at about 3 V. M' and M'' values decreased with increasing frequency and shifts to reverse bias region. In addition, it was determined that a.c. electrical conductivity (σ∗) values of thin films increased with increasing voltage as a function of dielectric loss.

Methylene Blue Photodegradation under Visible Irradiation on Ag-Doped ZnO Thin Films

This study synthesized and characterized Ag-doped ZnO thin films. Doped ZnO powders were synthesized using the sol-gel method, and thin films were fabricated using the doctor blade technique. The Ag content was determined by optical emission spectrometers with inductively coupled plasma (ICP plasma). Additionally, X-ray diffraction, Raman spectroscopy, Atomic Force Microscopy (AFM), diffuse reflectance, and X-ray photoelectron spectroscopy (XPS) measurements were used for physicochemical characterization. Finally, the photocatalytic degradation of methylene blue (MB) was studied under visible irradiation in aqueous solution. The Langmuir-Hinshelwood model was used to determine the reaction rate constant of the photocatalytic degradation. The physicochemical characterization showed that the samples were polycrystalline, and the diffraction signals corresponded to the ZnO wurtzite crystalline phase. Raman spectroscopy verified the ZnO doping process. The AFM analysis showed that roughness and grain size were reduced after the doping process. Furthermore, the optical results indicated that the presence of Ag improved the ZnO optical properties in the visible range, and the Ag-doped ZnO thin films had the lowest band gap value (2.95 eV). Finally, the photocatalytic degradation results indicated that the doping process enhanced the photocatalytic activity under visible irradiation, and the Ag-doped ZnO thin films had the highest MB photodegradation value (45.1%), as compared to that of the ZnO thin films (2.7%).

Characteristics of Ag Doped ZnO Thin Films Prepared by Sputtering Method

This paper presents results of preparation of Ag doped ZnO bulk sample by solid state reaction and Ag doped ZnO thin films by sputtering method. Effect of doping concentration (1, 2 and 4%) on the properties of the thin films was investigated. Various methods were utilized to investigate characteristics of the samples: X-ray diffraction, Raman scattering spectroscopy, photoluminescence, energy dispersive X-Ray spectroscopy, scanning electron microscopy, atomic force microscope, absorption spectroscopy and Hall measurement. The results show that Ag diffused into ZnO crystal lattice after heat treatment at 1200oC. As-prepared thin film samples exhibit low resistivity in the order of 10-3Ω.cm. The film doped with 2% Ag shows the lowest resistivity of 1.8´10-3Ω.cm which is potential for making transparent electrodes in optoelectronics.

Surface segregation of Ag and its effect on the microstructure, optical properties and conduction type of ZnO thin films

Ag doped ZnO thin films have potential applications in many electronic and optoelectronic devices. Effective control of the chemical state of Ag is important for adjusting the electrical and optical properties of Ag-doped ZnO materials. So far, the influence of annealing temperature on the physical properties of Ag-doped ZnO thin films prepared by sol-gel method has rarely been reported. In this work, Ag-doped ZnO thin films were prepared by spin-coating technique and the evolution of microstructure, optical properties and conduction type with the rise of annealing temperature were investigated. The experimental results show that with the increase of annealing temperature, the crystalline quality of Ag-doped ZnO thin film is gradually improved and the grains gradually grow up. The ultraviolet emission has been also enhanced step by step. When the annealing temperature exceeds 450 °C, the surface segregation of Ag is directly observed by a field emission scanning electron microscope. In addition, the diffraction peak of metallic Ag is also perceived on the XRD patterns. The X-ray photoelectron spectroscopy shows that the chemical valence of Ag has been changed from +1 to 0. The surface segregation of Ag leads to the conduction type of the ZnO thin film to change from P type to N type. The surface segregation of Ag is caused by the high annealing temperature combined with a rapid cooling treatment.

Seawater desalination using distillation method based on convex lens and Ag doped ZnO thin film to improve freshwater productivity and quality

Water is the most important need to support human life. Potentially, seawater is an alternative solution to solve water crisis problem especially in coastal areas. However, seawater have 3,5% salinity level. Water with high salinity is certainly not consumable. One effort that can be done to overcome the clean water crisis in the coastal areas is through desalination of seawater to produce water with low salinity. Some of the desalination methods that ever existed were MSF (Multi Stage Flash Distillation) and Reverse Osmosis. But both of these methods have high investment cost. Therefore, a cheaper and easier method to apply such as distillation is required. Distillation is done by drying the seawater under the sun which triggers the evaporation of water that evaporates and condenses to obtain freshwater. In this research, distillation system is combined with convex lens and Ag doped ZnO thin film. The convex lens is a lens that can focus heat and sunlight after passing through the lens. The use of the convex lens in the distillation system can speed up the evaporation process of seawater. The distillation system is made of glass and aluminum. Ag doped ZnO thin film was synthesized from AgNO3 and ZnCH3COOH by sol-gel method. Based on photocatalyst activity, when the Ag doped ZnO thin film is exposed with visible light, it will form a superoxide compound that can degrade pollutant such as heavy metals, eliminating harmful microbes and bacteria. This material also has a hydrophilicity that makes the water absorbed by the material coated with the thin film. With this characteristic, it can make the water more easily move on the glass due to the influence of gravity. Tests carried out include characterization of a thin layer of Ag doped ZnO, evaporation rate and water quality. From this technology, it can increase the production of freshwater and quality from the seawater desalination process with distillation method.

Effect of annealing temperature on the properties of Ag doped ZnO thin films

ZnO-Ag thin layers were prepared by thermal evaporation under vacuum and then subjected to recrystallization annealing heat treatment under atmosphere at 300, 400 and 500 °C to ensure oxidation and crystallization of ZnO. The results showed the evolution of these properties as a function of the annealing temperature. XRD analysis indicate that the crystallization of ZnO increase with annealing temperatures. The same observation was underlined for the transmittance with annealing temperature. However, the samples without annealing and those annealed at 300 and 400 °C appeared to be conductive with a resistance of 1.1 Ω, 0.67 Ω and 2.1 Ω while the sample annealed at 500 °C have a resistance of 1.73.105 Ω which belongs to a semiconductor material. As recognized, the hardness of the deposited layers as a function of the grain size does not respect the Hall-Petch relationship because of the grains size lower than 100 nm.

Biological and optical properties of sol-gel derived ZnO using different percentages of silver contents.

The role of Ag dopant on ZnO thin films are studied. Ag doped ZnO thin films were deposited by sol-gel dip coating on glass substrates. The X-ray diffraction analysis shows hexagonal wurtzite with preferred orientation along the (101) plane. The crystallite size decreases from 33.40 nm to 28.37 nm with increase in silver doping percentage. Optical examination shows that the band gap decrease with an increase in the Ag doping in ZnO. The structural and optical results prove that Ag has substituted Zn in ZnO lattice. Silver doped ZnO is effective against Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) bacteria. The roughness and the surface oxygen species accelerate the bacteria killing properties of Ag doped ZnO. They have pharmacological utility as a replacement of the antibiotics, bactericide and disinfectants. The TGA study showed that the thermal stability of the Ag doped ZnO takes place between 380-435 °C.

Studying structural, morphological and optical properties of nanocrystalline ZnO:Ag films prepared by sol–gel method for antimicrobial activity

Pure and Ag-doped zinc oxide sol–gel thin films were prepared by spin-coating process. Pure and Ag–ZnO films, containing 2–8% Ag, were annealed at 500 °C for 2 h. All thin films were prepared and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and UV–visible spectroscopy. X-ray diffraction studies show the polycrystalline nature with hexagonal wurtzite structure of ZnO and Ag:ZnO thin films. The crystallite size of the prepared samples reduced with increasing Ag doping concentrations. AFM and SEM results indicated that the average crystallite size decreased as Ag doping concentration increased. The transmittance spectra were then recorded at wavelengths ranging from 300 to 1000 nm. The films produced yielded high transmission at visible regions. The optical band gap energy of spin-coated films also decreased as Ag doping concentration increased. In particular, their optical band gap energies were 3.75, 3.55, 3.4, 3.3, and 3.23 eV at 0%, 2%, 4%, 6%, and 8%, respectively. Antibacterial activity of pure and Ag-doped zinc oxide against Escherichia coli and Staphylococcus aureus was evaluated by international recognized test (JIS Z 2801). The results showed that pure and Ag-doped ZnO thin film has an antibacterial inhibition zone against E. coli and S. aureus. Gram-positive bacteria seemed to be more resistant to pure and Ag-doped ZnO thin film than gram-negative bacteria. The test shows incrementally increasing in antibacterial activity of the thin films when dopant ratio increased under UV light.

Characterization of Ag-doped ZnO thin film for its potential applications in optoelectronic devices

Ag-doped ZnO thin films have potential applications in many optoelectronic devices. In this work, Ag-doped ZnO thin films were prepared by a low-cost sol-gel method and the effect of annealing time on the optical and electrical properties of the samples was studied. The results showed that all the samples were pure ZnO phase with a wurtzite structure. As the annealing time increased, the ZnO grains grew up and the films became denser. In addition, photoluminescence behavior dependent strongly on the annealing time was found. These Ag-doped ZnO films exhibited co-emission of ultraviolet, green, and red light. Considering the results of X-ray photoelectron spectroscopy and other researchers' proposals, the green emission centered at 549 nm was suggested to be related to the zinc vacancy defects, and the red emission centered at 652 nm was probably associated with oxygen interstitials or oxygen species adsorbed on the ZnO surface. Electrical measurement results showed that Ag-doped ZnO films with annealing time longer than 10 min presented P-type conductivity, and as the annealing time increased, the resistivity decreased first and then increased again.

Effect of Ag doping on the properties of ZnO thin films for UV stimulated emission

Ag doped ZnO thin films have been prepared using sol-gel spin coating method, with different doping concentrations. Structural and morphological properties of the films have been investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Thin films have been optically pumped and stimulated emission has been observed with strong peaks in the UV region. The UV stimulated emission is found to be due to exciton-exciton scattering, and Ag doping promoted this process by increasing the excitons concentrations in the ZnO lattice. Output-input intensity relation and peak emission, FWHM, and quantum efficiency relations with pump intensity have been reported. The threshold for which stimulated emission started has been evaluated to be about 18 MW/cm2 with quantum efficiency of about 58.7%. Mechanisms explaining the role of Ag in enhancement of stimulated emission from ZnO thin films have been proposed.

Laser-assisted approach for synthesis of plasmonic Ag/ZnO nanostructures

We report an experimental investigation on room-temperature synthesis of porous metal - semiconductor plasmonic nanocomposites by using laser deposition and annealing with nanosecond pulses. Ag/ZnO nanostructures are elaborated by using Ag-doped ZnO targets and the effects of silver concentration and laser annealing on the morphology and optical properties of the Ag/ZnO embedded nanostructures are studied. Ag-doped ZnO thin films are deposited by pulsed laser deposition on quartz substrates and subsequently laser annealed. Homemade Ag/ZnO targets with a silver doping concentration of 2, 4 and 6 at.%, prepared by ceramic technology, are exploited in the film deposition process. Then, the influence of laser irradiation on the microstructure and plasmon resonance absorption of the samples is investigated for three values of the number of laser pulses used for annealing. As the number of laser annealing pulses increases the resonance absorption is magnified. The net-like morphology of nanowires transforms to nanoparticles with increasing the silver concentration at the fixed number of ten laser annealing pulses. The composite systems show interesting plasmonic properties, which can be easily tuned by controlling the nanostructures morphology from nanowires through nanochains to nanoparticles. The experimental optical properties are in agreement with predictions of theoretical calculations showing that the extinction efficiency of AgNPs in ZnO environment peaks at about 490 nm.