Microwave-assisted Chemical Bath Deposition Research Articles

Crystallographic, Electric and Optical Analysis of Cs1+ Doped H3PW12O40 Nanocrystalline Thin Films Deposited by Microwave Assisted Chemical Bath Deposition Method

AbstractThe polyoxometalates like phosphotungstic acid (PTA) (H3PW12O40) and Cesium (Cs+) doped phosphotungstic acid (Cs‐PTA) (Cs3‐PW12O40) nanocrystalline thin films were effectively deposited by microwave assisted chemical bath deposition (MA‐CBD) technique. The structural characterization of microwave aided H3PW12O40 and Cs3‐PW12O40 thin films were done by Thermo gravimetric (TG) and Differential thermal analysis (DTA) techniques, X‐ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and Energy dispersive X‐ray analysis (EDAX). The TGDTA analysis revealed that the complete decomposition process of Cs‐PTA compound is carried out at 600 °C and which is comparatively lower than that of other chemical method. The X‐ray diffractogram confirms the polycrystalline nature of the synthesized H3PW12O40 and Cs3‐PW12O40 thin films having spinel cubic crystal structure. The lattice parameter of H3PW12O40 and Cs3‐PW12O40 compound found to be in the range of 11.34 Å to 11.46 Å. The main absorption peaks observed nearly 800, 1000 and 1100 cm−1 confirms the formation of H3PW12O40 and Cs3‐PW12O40 materials. The porous structure of nanocrystalline spherical grains morphology of H3PW12O40 and Cs3‐PW12O40 films were confirmed from SEM analysis. An appropriate peaks of metal ions like P, W, O and Cs observed in EDAX spectra shows the stoichiometric formation of H3PW12O40 and Cs3‐PW12O40 thin films.

Rapid synthesis of ZnO nanostructures on woven carbon fiber using microwave treated chemical bath deposition and their characterization

Microwave-assisted chemical bath deposition (MACBD) is a new method for synthesizing metal-oxide layers and nanostructures efficiently. The fast synthesis of ZnO nanostructures (NSs) on woven carbon fiber (WCF) is reported in this study employing the MACBD technique. An aqueous solution of tetra ammonium zinc complex was used to create several morphologies of ZnO NSs on WCF fabric, including nanopetals, twinned nanospheres, nanoflowers, and nanoflakes. Under microwave heating, plain WCF fabric samples were treated with several precursor solutions. When compared to conventional CBD, the development time of ZnO NSs is lowered to roughly 2–4 min. Field-emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), and an X-ray diffractometer were used to evaluate as-developed ZnO NSs morphologies on WCF. The processing of ZnO NSs on the strands of carbon fibers was interpreted using FESEM, and it was discovered that variations in microwave duration and precursor solution are the primary causes of ZnO morphology development. With the formation of nanostructures, the crystalline peak height of the nanostructures increases. For the fabrication of high performance ZnO nanostructured WCF hybrid polymer composites vacuum bagging technique were used along with resin transfer system. Epoxy resin was applied as a matrix material with the five layers of ZnO grown WCF for varied applications.

Structural and Optical Properties of Nanocrystalline Pbs Thin Films Prepared by Microwave-Assisted Chemical Bath Deposition

Structural and Optical Properties of Nanocrystalline Pbs Thin Films Prepared by Microwave-Assisted Chemical Bath Deposition

Copper Oxide Films Deposited by Microwave Assisted Alkaline Chemical Bath

Copper oxide (CuO) films were deposited onto glass substrates by the microwave assisted chemical bath deposition method, and varying the pH of the solution. The pH range was varied from 11.0 to 13.5, and the effects on the film properties were studied. An analytical study of the precursor solution was proposed to describe and understand the chemical reaction mechanisms that take place in the chemical bath at certain pH to produce the CuO film. A series of experiments were performed by varying the parameters of the analytical model from which the CuO films were obtained. The crystalline structure of the CuO films was studied using X-ray diffraction, while the surface morphology, chemical composition, and optical band-gap energy were analyzed by scanning electron microscopy, X-ray photoelectron spectroscopy, and UV–Vis spectrophotometry, respectively. The CuO films obtained exhibited a monoclinic crystalline phase, nanostructured surface morphology, stoichiometric Cu/O ratio of 50/50 at%, and band-gap energy value of 1.2 eV.

Study of optical properties of ZnS and MnZnS (ZnS/MnS) nanostructure thin films; Prepared by microwave-assisted chemical bath deposition method

The main objective of this work is the preparation of ZnS and MnZnS (ZnS/MnS) nanostructure thin films in an ammonia-free solution by microwave-assisted chemical bath deposition (MA-CBD) method and decreasing consume of energy via decreasing deposition time from several hours to several minutes compared to conventional CBD method. ZnS and MnZnS films were deposited on commercial microscope slide glass substrates using acetic acid as a safe complexing agent. Growth rate of the film thickness was obtained approximately 1.8–2.0 nm/min. The influence of [S2−/Zn2+] molar ratio on the formation, quality, and optical properties of the films was investigated. X-ray diffraction results approved the formation of MnS/ZnS hybrid films with a cubic structure for the ZnS and MnS. Atomic force microscopy (AFM) measured the average of roughness around 6.4 nm. Field emission scanning electron microscopy (FE-SEM) exhibited that the layers were dense, homogenous, and free of pinhole or crack with very small particles at about 10–40 nm. Energy-dispersive X-ray spectrometer (EDX) revealed the presence of the Mn in the ZnS thin film and confirmed the deficiency of sulfide in the films. Fluorescence (FL) emission spectra of the films showed a strong dependence on composition as well as population (density) of defect states such as S vacancies. UV–vis results indicated that all films are highly transparent, and their band gap energy varies from 3.6eV to 3.85eV.

Study of Microwave-Assisted MoS2 and Graphene Composite Counter Electrode for Dye-Sensitized Solar Cells

Graphene-MoS2 composites were synthesized via one-step microwave-assisted chemical bath deposition and used as counter electrodes for dye-sensitized solar cells, instead of traditional Pt film which has high cost and poor stability. The effects of graphene additive amount on the performance of cells were studied. The results reveal that sheet porous structure graphene and MoS2 particles has been incorporated tightly, which is the benefit of electrical conductivity and catalysis ability. A maximum efficiency of 6.3% has been achieved under 100 mW cm−2 illumination when the Mo:C is 1:1.

The structural and optical properties of ZnO:Sn nanostructured films by MW-CBD

ZnO and ZnO:Sn films have been deposited by microwave assisted chemical bath deposition (MW-CBD) technique. Effect of tin dopant on the structural, optical and morphological properties of ZnO films has been investigated using XRD, UV–vis absorption spectra, AFM and SEM. The XRD pattern indicated that all of the films are of polycrystalline hexagonal wurtzite nature. The average crystal size (D) values of the films decreased from 58 nm to 46 nm with increasing amount of Sn. The optical properties of the films were analyzed by Transmittance (T %) and Reflectance (R %) spectra. The energy band gap (Eg) and T % values of the films increased with the amount of tin dopant. Eg values were found to be in the range of 3.27-3.37 eV. The surface morphology of the films was affected by Sn dopant. Hexagonal nanorods were observed on the films surface.

Enhancement characterization of the MSM detector based on Mn doped-ZnO NRS synthesized by microwave assisted chemical bath deposition

In this work, ZnO nanorods (NRs) were doped with (0, 3, and 6)% Mn and grown on the glass slide by the Microwave-Assisted Chemical Bath Deposition (MACBD) method, at 80 °C. Al contacts were evaporated on the prepared thin film by thermal evaporation technique to produce metal-semiconductor-metal detector (MSM). The novelty of this work is to obtain a UV detector device that works at room temperature using a simple method and low synthesis temperature. The structural properties and the surface morphology of the prepared samples were investigated. The XRD results of un-doped and Mn-doped Zinc Oxide (MZO) NRs reveals sharp and strong peaks, confirming high crystallinity structure. The FE-SEM images showed that the Zinc Oxide NRs were good-aligned and well distributed throughout the glass substrate. At a room temperature, the fabricated detectors were showed an important difference among the current density of the UV wavelengths 365 nm, 385 nm and dark current density. Under 5 V of the applied source voltage, the responsivity of MSM photodetectors based on MZO (0, 3, and 6)% were (0.0361, 0.044 and 0.0765) A/W at a wavelength 365 nm, (0.0232 and 0.0324 and 0.0391) at UV wavelength of 385 nm, at power density of 40 μW/cm2, respectively. All devices in this work demonstrated high response to the UV radiation and showed almost no response to the visible spectrum.

Effect of Deposition Time on the Optoelectronics Properties of PbS Thin Films Obtained by Microwave-Assisted Chemical Bath Deposition

PbS thin films with thickness between 100 and 150 nm were grown for the first time by microwave-assisted chemical bath deposition in a commercial automated system with deposition times not exceeding 5 min. X-ray diffraction analysis shows that the thin films have cubic rock salt type structure with good crystallinity. The grain size increased from 18 to 20 nm, as the deposition time increased. Energy dispersive X-ray results confirm that the films are stoichiometric. Optical measurements show that thin films have relatively high absorption coefficients between 104 and 105 cm-1 in the visible range. In addition, the films exhibit a direct gap, within the energy range from 1.0 to 1.35 eV. The electrical properties, such as conductivity, the Seebeck coefficient, carrier concentration, and carrier mobility, are discussed.

Defect-Rich ZnO Nanorod Arrays for Efficient Solar Water Splitting

A novel ultrarapid synthetic method for the production of vertically aligned ZnO nanorod (NR) arrays has been demonstrated, using a microwave assisted chemical bath deposition method. High quality ...

Lead sulfide films synthesized by microwave-assisted chemical bath deposition method as efficient counter electrodes for CdS/CdSe sensitized ZnO nanorod solar cells

In this study, PbS thin films are deposited on FTO substrate via a rapid and facile microwave-assisted chemical bath deposition (MACBD) and then used directly as the counter electrodes (CEs) for CdS/CdSe quantum dots co-sensitized ZnO nanorods array solar cells (QDSSC). The resultant PbS CEs show good uniformity, strong adhesion to the FTO and superior electrocatalytic activity for the reduction of polysulfide electrolyte compared to the PbS CEs prepared with conventional CBD method. The combination of ZnO/CdS/CdSe photoanode with the optimum PbS CE shows appreciated power conversion efficiency (PCE) of 4.85%. The augmented photovoltaic performance can be attributed to its high electrocatalytic activity for polysulfide reduction in QDSSC, which results in a low charge transfer resistance at the interface of CE/electrolyte. The results demonstrate the potential application of this MACBD method in fabricating efficient metal sulfide counter electrode for QDSSC.

Effect of the zinc salt concentration on the ZnO thin films properties grown by MWCBD

Nanostructured ZnO thin films with different surface morphologies have been synthesized by the microwave assisted chemical bath deposition technique (MWCBD), adjusting the pH of the reaction solution between 9 and 11.14. Newest results are presented in this work supported by previous investigations. Morphology, structure and optical properties of the films have been studied by scanning electron microscopy (SEM), x-ray diffraction (XRD) and room temperature photoluminescence (PL) techniques. It has been observed that the zinc salt concentration and the pH of the reaction solution determines the reaction kinetics, affecting strongly the morphology of the final product. However, the rapid heating in microwave irradiation process facilitates the crystallization of the formed nano-/microstructures. Effects of composition and morphology of the grown nano-/microstructures on their photoluminescence (PL) behaviors have been discussed.

Rapid Synthesis of Semipolar ZnO Nanorod Arrays on M-Sapphire by Microwave-Assisted Chemical Bath Deposition

ZnO is a wide-band gap (3.37 eV) II–VI semiconductor with large exciton binding energy of 60 meV which is larger than other materials commonly used for light emission devices, such as ZnSe (22 meV) and GaN (25 meV). Especially ZnO nanorods due to their unique physical and chemical properties have many important applications for devices, such as transparent electronics, sensors, detectors, etc. It is well known that wurtzite ZnO in c-plane orientation has strong polarization which significantly reduces light-emitting efficiency. Though the polarization is eliminated for nonpolar ZnO, it is difficult to grow nonpolar ZnO nanorods as they are normally grown along c-axis normal to the substrate surface. Polarization can be greatly reduced for semipolar ZnO which is likely to be obtained if nanorods can be grown with c-axis in an inclined angle with substrate surface; however, well-aligned semipolar oriented ZnO nanorods have been rarely reported. Here, we report the first observations of growth of epi-ZnO nanorods with semipolar orientation on m-sapphire by microwave-assisted chemical bath deposition (CBD) with a fast growth rate. ZnO nanorods have been widely grown by CBD which is a simple, low cost and low temperature process but with a low growth rate generally in the range of 5-10 nm/min. Microwave-assisted CBD is a newly developed technique because of microwave can directly transmit its energy to dielectric medium by radiation, such that quick and uniform heating without much energy loss caused by conduction is feasible for aqueous solution. In recent years, microwave heating has been demonstrated to have much higher ZnO nucleation and growth rates than with conventional heating. Furthermore, a several microns thick epitaxial c-plane ZnO film can be deposited on MgAl2O4 (111) substrate in just a few minutes by microwave assisted CBD. In this study, 1 x 1 cm2 m-sapphire substrates were seeded with semipolar ZnO at a temperature between 500-700 °C by using mist chemical vapor deposition. The seeded substrate was then placed in a 90 °C aqueous solution for microwave-assisted CBD of ZnO nanorods. The solution was pre-formulated at room temperature with 0.0375 mol/L zinc nitrate hexahydrate and 0.0375 mol/L hexamethylenetetramine. The microwave power can be automatically tuned to maintain the solution at a constant temperature during CBD. Microstructural characterization was performed with X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) to understand the growth process. Cross-sectional TEM specimens were prepared with focused ion beam. Photoluminescence (PL) spectroscopy was performed with He-Cd laser for measurements of optical properties. For ZnO nanorods formed after growth for 10 minutes at 90°C, SEM in Fig. 1 shows that tilted hexagonal columns of ZnO with diameter about 100-200 nm are formed as a well-aligned and inclined array on the sapphire. Figure 2 shows a typical bright field TEM micrograph in cross-section view, illustrating that the ZnO nanorods grown on the 30 nm thick seed layer have an inclined angle about 30° with m-sapphire surface and an average length about 500 nm which gives a growth rate of 50 nm/min and an aspect ratio of 2.5-5 for the nanorods. Furthermore, high-resolution TEM and atomic-resolution annular dark field STEM micrographs with FFT patterns of sapphire and ZnO as shown in Fig. 2 reveal that the semipolar ZnO seed layer has an epitaxial relationship with m-sapphire as ZnO[1-100] || sapphire[11-20] and ZnO(0001)|| sapphire(1-10-4). Hence, the c-plane of ZnO seed has a 30° tilt away from the surface normal of the sapphire, resulting in the following growth of nanorods along the c-axis direction. As a result, the inclined nanorods has a semipolar orientation of (-1-122) || sapphire m-plane. It should be pointed out that ZnO (-1-122) reflection is hardly seen in XRD as its interplanar spacing is very close to that of sapphire (3-300). A typical PL spectrum of the ZnO nanorods measured at 10K is shown in Fig. 3 from which a strong narrow near band emission (NBE) peak centered at 3.31 eV is clearly seen with and a weak deep-level emission peak at around 2.17 eV, implying that the nanorods have a reasonably good quality. Keywords: ZnO, nanorod, chemical bath deposition microwave Figure 1

Rapid Synthesis of Semipolar ZnO Nanorod Arrays on M-Sapphire by Microwave-Assisted Chemical Bath Deposition

Microwave-assisted chemical bath deposition (CBD) is a newly developed technique for fast growth of single-crystalline ZnO nanorods in a solution containing zinc nitrate at temperature below 100°C. ZnO nanorods have many applications for devices, however, semipolar oriented ZnO nanorods have been rarely reported. In this study, epitaxial growth of well-aligned arrays of inclined semipolar ZnO nanorods on a ZnO seed layer on m-plane sapphire substrates is successfully fabricated by using microwave-assisted chemical bath deposition for 10 min at 90 °C. TEM analysis reveals that The ZnO nanorods have an inclined angle about 30° with m-sapphire surface and an average length about 500 nm which gives a growth rate of 3 μm/h. Micro-photoluminescence measurements show that ZnO nanorods are of a reasonably good quality.

Synthesis and characterization of polypyrrole thin film by MW-CBD method for NH3 gas sensor

The microwave-assisted chemical bath deposition method is used for synthesis of polypyrrole (Ppy) thin film. The structural, morphological, optical absorption and wettability properties of deposited Ppy thin films are studied using various characterization techniques. The X-ray diffraction pattern shows amorphous nature of Ppy thin film. To confirm the formation of Ppy compound, Fourier transform infrared spectroscopic study is used. The scanning electron microscopy study shows porous structure of Ppy thin film. The optical study revealed that Ppy thin film exhibits band gap of 3.5 eV. The Ppy film exhibited hydrophilic nature with contact angle of 41°. The Ppy films show 85% response to ammonia (NH3) gas at room temperature.

Fabrication of p-Si/n-ZnO:Al heterojunction diode and determination of electrical parameters

We present a fundamental experimental study of a microwave assisted chemical bath deposition (MW-CBD) method for Al doped ZnO films. Field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) spectroscopy were used to analyze the microstructures and crystalline structures of these films, respectively. The p-Si/n-ZnO:Al heterojunction diodes were fabricated. The current–voltage (I–V) characteristics of these diodes were measured at room temperature. The important electrical parameters such as series resistance, the ideality factor and the barrier height were determined by performing plots from the forward bias I–V characteristics using different methods. The obtained results indicate that Al doping improve the electrical properties of the p-Si/n-ZnO diode. The best rectification properties were observed in the p-Si/n-ZnO:5%Al heterojunction diode, so only capacitance–voltage (C–V) measurements of this diode were taken. Electrical parameter values such as series resistance, the built-in potential and the acceptor concentration calculated for this heterojunction diode.

Fast formation of CdS thin films prepared via the microwave-assisted chemical bath deposition process

Cadmium sulfide (CdS) ceramic thin films were successfully synthesized via the microwave-assisted chemical bath deposition process in a short reaction period of 5min at 65°C. As long as the molar ratios of thiourea to cadmium sulfide ([TU]/[CdSO4] molar ratios) were below 50, dense CdS films formed on Cu(In,Ga)Se2 absorbers. Upon elevating the [TU]/[CdSO4] molar ratios, a large number of CdS particles precipitated in the bulk solutions, leading to the formation of holes on CdS films and a reduction in the film thickness. These phenomena imply that elevating the concentration of thiourea facilitates homogeneous nucleation and suppresses the growth of CdS films. The photovoltaic properties of Cu(In, Ga)Se2 solar cells were influenced by the different [TU]/[CdSO4] molar ratios. When the [TU]/[CdSO4] molar ratio was 30, a relatively high efficiency of 10.83% was achieved. According to diode analysis, increasing the [TU]/[CdSO4] molar ratios raised the diode factor (A) values. The microwave-assisted chemical bath deposition process was demonstrated to be a potential process for the fast deposition of CdS ceramic thin films.

Zinc-doped CdS nanoparticles synthesized by microwave-assisted deposition

Cd1−xZnxS nanoparticles were grown on pre-cleaned glass substrates using microwave-assisted chemical bath deposition technique. Nanoparticles obtained by this method were smooth, uniform, good adherent, brownish yellow in color where the brightness of the yellow color nature decreases with increasing Zn2+ content. The elemental composition analysis confirmed that the nanoparticles comprise of Cd2+, Zn2+ and S2−. Scanning electron microscope images confirmed the surface uniformity of the Cd1−xZnxS nanoparticles devoid of any void, pinhole or cracks and covered the substrate well. The particle size also decreases with increasing Zn ion content. X-ray diffraction (XRD) indicates the hexagonal structure (002) without phase transition. The grain size decreases from 36.45 to 9.60 nm, dislocation density increases from 0.000745 to 0.01085 Line2/m2 and lattice parameter decreased from 6.868 to 6.155 nm with increasing Zn2+ content. The best transmittance of about 95% was achieved for x = 1.0. The nanoparticles showed reduction in the absorbance as Zn ion content increased. Four point probe revealed that the electrical resistivity increased from 1.51 × 1010 to while electrical conductivity decreases from 6.62 × 10−11 to with increasing Zn2+ content. The other electrical properties such as sheet resistance increased from 1.52 × 108 to , charge carrier mobility decreased from 0.777 to 0.0105 cm2/(V s) and charge carrier density increased from 1.06 × 1012 to 3.95 × 1012 cm−3.

Nanostructured ZnO-based biosensor: DNA immobilization and hybridization

An electrochemical DNA biosensor was successfully fabricated by using (3-aminopropyl) triethoxysilane (APTES) with zinc oxide (ZnO) nanorods synthesized using microwave-assisted chemical bath deposition method on thermally oxidized SiO2 thin films. The structural quality and morphology of the ZnO nanorods were determined by employing scanning electron microscopy (SEM) and X-ray diffraction (XRD), which show a hexagonal wurtzite structure with a preferred orientation along the (101) direction. The surface of the SiO2 thin films was chemically modified with ZnO. Label-free detection DNA immobilization and hybridization were performed using potassium hexacyanoferrate with cyclic voltammetry (CV) measurements. The capacitance, permittivity, and conductivity profiles of the fabricated sensor clearly indicate DNA immobilization and hybridization. Results show that the capacitance values of bare, ZnO- modified surface immobilization, and target DNA hybridization were 46×10−12F, 47×10−8F, 27μF, and 17μF, respectively, at 1Hz. The permittivity measurement increased from 3.94×103 to 251×103 and 165×103 at the frequency range of approximately 200 to 1Hz for bare and DNA immobilization and hybridization, respectively. The measured conductivity values for the bare, ZnO, immobilized, and hybridization device were 2.4×10−9, 10×10−8, 1.6×10−7, and 1.3×10−7Scm−1, respectively.

Effects of ammonia concentration on the formation of CdS fabricated via microwave‐assisted chemical bath deposition

AbstractThe microwave‐assisted chemical bath deposition (MACBD) process was successfully developed in this study for the preparation of cadmium sulfide (CdS) films as the buffer layers in Cu(In,Ga)Se2 solar cells. The MACBD process reduces the reaction time to just 8 min. During the MACBD process, increasing the concentration of NH4OH in the solution effectively reduced the thickness of the films as well as the particle sizes of in CdS films. At high NH4OH concentrations, the heterogeneous nucleation of CdS dominated, and the formation of films was controlled via the ion‐by‐ion growth mechanism. Increasing the concentration of NH4OH from 1 to 2.5 M significantly increased the conversion efficiency of the fabricated CIGS solar cells from 7.15% to 9.12%. The increase in the efficiency was attributed to an increase in the absorption of incident light and the enhancement of the carrier collection due to a reduction in the thickness of the prepared CdS films. According to diode analysis, the improvement in the diode ideality factor and leakage current was owing to the uniform coverage of CdS films and a reduction in series resistance associated with a decrease in the thickness of CdS films. When the concentration of ammonia was further increased to 3 M, incomplete coverage of CdS films on CIGS layers resulted in the formation of shunt paths and degraded the cell performance. This study demonstrated that CdS films prepared using the MACBD process with the optimum concentration of ammonia effectively improved the photovoltaic performance of Cu(In,Ga)Se2 solar cells.