Ultrasonic Spray Method Research Articles

The Effect of the Cu Source on Optical Properties of Cu-Doped ZnO Films

Cu-doped ZnO (CZO) films have been widely discussed due to its potential applications in semiconductor devices, such as gas sensors or solar cells, but few articles were reported to show the effect on properties of CZO films by using different Cu sources. The article demonstrates that CZO films have been prepared by using different Cu source via a simple ultrasonic spray method, in which copper nitrate and copper acetate were used as copper sources. Optical properties of CZO films prepared by copper nitrate and copper acetate were investigated by transmittance and photoluminescence measurement. The X-ray diffraction analysis and field emission scanning electron microscopy were used to investigate the composition and the morphology of the films. The CZO films prepared by using copper acetate shows better optical properties by comprehensive analysis.

A comparative study on structural and optical properties of ZnO and Al-doped ZnO thin films obtained by ultrasonic spray method using different solvents

Transparent conducting ZnO and Al doped ZnO thin films were deposited on glass substrate by ultrasonic spray method. The thin films with concentration of 0.1M were deposited at 350°C with 2min of deposition time. The effects of ethanol and methanol solution before and after doping on the structural, optical and electrical properties were examined. The DRX analyses indicated that ZnO films have nanocrystalline nature and hexagonal wurtzite structure with (100) and (002) preferential orientation corresponding to ZnO films resulting from methanol and ethanol solution, respectively. The crystallinity of the thin films improved with methanol solution after doping to (002) oriented. All films exhibit an average optical transparency about 90%, in the visible range. The band gaps values of ZnO thin films are increased after doping from 3.10 to 3.26eV and 3.27 to 3.30eV upon Al doping obtained by ethanol and methanol solution, respectively. The electrical conductivity increase from 7.5 to 15.2 (Ωcm)−1 of undoped to Al doped ZnO thin films prepared by using ethanol solution. However, for the methanol solution; the electrical conductivity of the film is stabilized after doping.

Correlation between crystallite size–optical gap energy and precursor molarities of ZnO thin films

We investigated the structural and optical properties of ZnO thin films as an n-type semiconductor. The films were deposited at different precursor molarities using an ultrasonic spray method. In this paper we focused our attention on a new approach describing a correlation between the crystallite size and optical gap energy with the precursor molarity of ZnO thin films. The results show that the X-ray diffraction (XRD) spectra revealed a preferred orientation of the crystallites along the c-axis. The maximum value of the crystallite size of the films is 63.99 nm obtained at 0.1 M. The films deposited with 0.1 M show lower absorption within the visible wavelength region. The optical gap energy increased from 3.08 to 3.37 eV with increasing precursor molarity of 0.05 to 0.1 M. The correlation between the structural and optical properties with the precursor molarity suggests that the crystallite size of the films is predominantly influenced by the band gap energy and the precursor molarity. The measurement of the crystallite size by the model proposed is equal to the experimental data. The minimum error value was estimated by Eq. (4) in the higher crystallinity.

Fabrication of gas diffusion electrodes via electrophoretic deposition for high temperature polymer electrolyte membrane fuel cells

The Electrophoretic Deposition (EPD) method was adapted to fabricate Gas Diffusion Electrodes (GDEs) for Membrane Electrode Assemblies (MEA) for High Temperature Polymer Electrolyte Membrane Fuel Cells (HT-PEMFC) operating at 160 °C. Suspensions containing the Pt/C catalyst, polytetrafluoroethylene (PTFE) and NaCl were studied. Stable catalyst suspensions were observed when the NaCl concentrations were ≤0.1 mM. Mercury intrusion porosity analysis showed that the GDEs obtained via the EPD method had higher porosity (30.5 m2 g−1) than the GDEs fabricated by the ultrasonic spray method (25.2 m2 g−1). Compared to the ultrasonically sprayed MEA, the EPD MEA showed ∼12% increase in peak power at a slightly lower (∼4 wt %) Pt loading. Electrochemical Impedance Spectroscopy (EIS) analysis showed a lower charge transfer resistance for the EPD MEA compared to the ultrasonically sprayed MEA while Cyclic Voltammetry (CV) analysis showed ∼16% higher Electrochemical Surface Area (ECSA) for the EPD MEA compared to the ultrasonically sprayed MEA. These observations were attributed to the higher porosity and better catalyst particle size distribution of the EPD GDEs. A comparison between PTFE and Nafion® ionomer in the Catalyst Layers (CL) of two EPD MEAs revealed that PTFE yielded MEAs with better performance and is therefore more suitable in HT-PEMFCs.

Effect of the Cu Source on Optical Properties of CuZnO Films Deposited by Ultrasonic Spraying.

CuZnO (CZO) films have received considerable attention, owing to their potential applications in semiconductor devices, including gas sensors or solar cells. However, exactly how these films affect the properties of CZO films by using different Cu sources has seldom been investigated. This study demonstrates the feasibility of preparing CZO films by using different Cu sources via a simple ultrasonic spray method, in which copper nitrate and copper acetate were used as copper sources. Optical properties of CZO films prepared by copper nitrate and copper acetate were also investigated, based on transmittance and photoluminescence measurements. Additionally, the composition and the morphology of the films were investigated using the X-ray diffraction analysis and field emission scanning electron microscopy. The results of this study demonstrate that the CZO films prepared by using copper acetate exhibit better optical properties.

Effect of Urbach energy with precursor molarity on the crystallite size in undoped ZnO thin film

We investigated the structural and optical properties of ZnO thin films as the n-type semiconductor, the thin films were deposited at different precursor molarities by ultrasonic spray method on glass substrate at 350 ◦ C, as discussed in our published paper. In this paper we focused our attention on the present a new approach to the description of correlation between crystallite size and Urbach energy with precursor molarities, this correlation based on experimental data of our study previously published. The correlation between structural and optical properties with precursor molaritie was investigated. The measurement of the crystallite sizes of undoped ZnO thin films were realized at different model proposals; these measurements shows that the crystallite sizes of the films can be estimated by varying the Urbach energy and the concentration of ZnO solution, which are in qualitative agreements with the experimental data. The best estimate result is measured by Equation (9) with minimum relative errors values were limited to 1 %. Thus results indicate that the ZnO thin films are chemically purer and have many fewer defects and less disorder owing to an almost complete chemical decomposition.

Physical and photo-electrochemical characterizations of ZnO thin films deposited by ultrasonic spray method: Application to HCrO4− photoreduction

ZnO thin films, prepared by ultrasonic spray onto glass substrate, crystallize in the wurtzite structure. The XRD pattern shows preferential orientation along the [002] direction. The films deposited at 350°C consist of 60nm crystallites with an average thickness of ∼150nm and SEM images show rough surface areas. The gap increases with increasing the temperature of the substrate and a value of 3.25eV is obtained for films deposited at 350°C. ZnO is nominally non-stochiometric and exhibits n-type conduction because of the native defects such as oxygen vacancies (VO) and/or interstitial zinc atom (Zni) which act as donor shallows. The conductivity is thermally activated and obeys to an exponential type law with activation energy of 57meV and an electron mobility of 7cm2V−1s−1. The capacitance-voltage (C−2V) measurement in acid electrolyte (pH∼3) shows a linear behavior with a positive slope, characteristic of n-type conduction. A flat band potential of −0.70 VSCE and a donors density of 5.30×1016cm−3 are determined. The Nyquist plot exhibits two semicircles attributed to a capacitive behavior with a low density of surface states within the gap region. The centre is localized below the real axis with a depletion angle of 16° ascribed to a constant phase element (CPE) due to the roughness of the film. The energy band diagram assesses the potentiality of ZnO films for the photo-electrochemical conversion. As application, 94% of chromate (3.8×10−4M) is reduced after 6h under sunlight (AM 1) with a quantum yield of 0.06% and the oxidation follows a first order kinetic.

The effects of solvent nature on spray-deposited ZnO thin film prepared from Zn (CH3COO)2, 2H2O

Transparent conducting zinc oxide was deposited on glass substrate by ultrasonic spray method. The ZnO samples with concentration of 0.1M were deposited at 300, 350 and 400°C with 2min of deposition time. The effects of substrate temperature, ethanol and methanol solution on the structural, electrical and optical properties were examined. The DRX analyses indicated that ZnO films have polycrystalline nature and hexagonal wurtzite structure with (100) and (002) preferential orientation corresponding to ZnO films resulting from methanol and ethanol, respectively. The crystallinity of the thin films improved with ethanol solution. All films exhibit an average optical transparency about 80%, in the visible range. The band gap energy of ZnO films obtained with methanol solution higher than of ethanol solution for all the films. The electrical resistivity decrease with ZnO obtained from ethanol indicated; due to the maximum crystallite size retched at this point.

The effect of the film thickness and doping content of SnO2:F thin films prepared by the ultrasonic spray method

This paper reports on the effects of film thickness and doping content on the optical and electrical properties of fluorine-doped tin oxide. Tin (II) chloride dehydrate, ammonium fluoride dehydrate, ethanol and HCl were used as the starting materials, dopant source, solvent and stabilizer, respectively. The doped films were deposited on a glass substrate at different concentrations varying between 0 and 5 wt% using an ultrasonic spray technique. The SnO2:F thin films were deposited at a 350 °C pending time (5, 15, 60 and 90 s). The average transmission was about 80%, and the films were thus transparent in the visible region. The optical energy gap of the doped films with 2.5 wt% F was found to increase from 3.47 to 3.89 eV with increasing film thickness, and increased after doping at 5 wt%. The decrease in the Urbach energy of the SnO2:F thin films indicated a decrease in the defects. The increase in the electrical conductivity of the films reached maximum values of 278.9 and 281.9 (Ω·cm)−1 for 2.5 and 5 wt% F, respectively, indicating that the films exhibited an n-type semiconducting nature. A systematic study on the influence of film thickness and doping content on the properties of SnO2:F thin films deposited by ultrasonic spray was reported.

Preparation of transparent, conductive ZnO:Co and ZnO:In thin films by ultrasonic spray method

This paper examines the growth of undoped and doped thin films with (Co and In) on glass substrate at 350°C using ultrasonic spray technique. We have investigated the influence of doping concentrations ranging from 0 to 4 wt.% on structural, optical, and electrical properties of ZnO thin films. Zinc acetate dehydrate, CoCl3 4H2O or InCl3, ethanol, and monoethanolamine were used as a starting materials, dopant source, solvent, and stabilizer, respectively. The X-ray diffraction analysis indicated that the undoped and doped ZnO thin films have polycrystalline nature and hexagonal wurtzite structure with (002) preferential orientation. The maximum average crystallite sizes of ZnO:Co and ZnO:In were 55.46 and 45.78 nm at concentrations of 2 wt.% Co and 3 wt.% In, respectively, indicating that the crystallinity of doped films improved after doping. The optical absorption spectra showed that all undoped and doped ZnO films are transparent within the visible wavelength region. The band gap energy of ZnO:Co thin films increased after doping from 3.25 to 3.36 eV; however, the optical gap of ZnO:In decreases after doping from 3.25 to 3.18 eV, indicating the increase and decrease, respectively, in the transition tail width. The electrical conductivity of doped films is stabilized after doping. Transparent, conductive Co-doped ZnO thin films deposited by ultrasonic spray technique are of good quality.

Correlation between the physico-chemical properties and the oxygen reduction reaction electro catalytic activity in acid medium of Pd–Co alloys synthesized by ultrasonic spray method

Pd–Co alloys electro catalysts were synthesized for the oxygen reduction reaction (ORR) for polymer electrolyte membrane fuel cells by a new ultrasonic spray method. This allows for the first time the preparation of reproducible small particle size with dominant dimensions between 2.5 and 6.5nm for all samples of the Pd–Co electro catalysts. This method is also based on less time consuming and steps than the classical methods. The physico-chemical properties of Pd–Co electro catalysts from different compositions were characterized. Samples of Pd/C, Pd5Co1/C, Pd3Co1/C, Pd2Co1/C, and 5 Pd1Co1/C where synthesized and Pt/C for comparison. The samples of Pd–Co alloys prepared here are substitution solid solutions where some atoms of Pd are replaced by Co atoms. Based on experimental bending energies, the main composition of the samples is found to be metallic Pd and Co. The physic-chemical composition and properties of the alloys were correlated to the ORR electro catalytic activity in an acid medium. A volcano plot was observed between the variation of the mass activity and the Pd content or Pd–Pd distance of the Pd–Co alloys. The optimum value of the mass activity was obtained for Pd3Co.

A comparative study on the nanocrystalline ZnO thin films prepared by ultrasonic spray and sol⿿gel method

Nanocrystalline ZnO thin films are deposited through two different chemical methods: (i) the films prepared by ultrasonic spray with 0.1M and (ii) dip-coating from zinc acetate complex solutions with 0.5M, the films obtained at different temperatures. The XRD analyses indicated that ZnO films have nanocrystalline hexagonal structure with (002) preferential orientation and the maximum crystallite size value of 103nm measured from the films prepared by dip-coating. UV⿿vis measurement indicated that all films are transparency in the visible region. The optical band gap increased with decreasing of the Urbach tail energy indicating that the increase in the transition tail width and decrease of the defects, respectively.

Microstructure and opto-electrical properties of SnO<SUB align="right">2:In<SUB align="right">2O<SUB align="right">3 alloys thin films prepared by ultrasonic spray

In this work, we study the effect of indium weight ratio in solution: R = [In/Sn] on the properties of SnO2:In2O3 thin films prepared by ultrasonic spray method at fixed temperature of 300°C. The used precursors are tin chloride dehydrate and indium trichloride dissolved in methanol. To prepare hybrid SnO2:In2O3 thin films with different concentrations, the ratio R is varied in the range of 10–95 wt%. The resulting films were characterised by X-ray diffraction, scanning electron microscopy analysis, UV-visible spectrophotometer and conductivity measurement. The XRD results indicate segregation between SnO2 and In2O3 phases in all films. The optical transmittance is in the range of [75–85]%. The conductivity values of pure oxides are very low [~10–3 (Ω.cm)–1] and it is increased with R ratio until a maximum value of 1.2 × 102 (Ω.cm)–1 obtained at R = 95 wt%. Consequently, the higher figure of merit (Fm = σ.T.d) is obtained at this later ratio.

Janus micro-reactors

Janus hollow spheres, with different compositions compartmentalized onto both interior and exterior surfaces of the same shell and P25 nanoparticles encapsulated in the cavities, are synthesized by the ultrasonic spray method to selectively enrich desired reagents in a confined environment for further reaction.

Preparation of YAG nano-powders via an ultrasonic spray co-precipitation method

Nanometer-sized particles (1–100 nm) are of considerable interest for a wide variety of applications, due to their unique and improved properties primarily determined by size. In this study, homogenously dispersed nanocrystalline YAG powders were synthesized by calcination of the YAG precursors prepared by an ultrasonic spray method. The effects of spray droplets moving path, calcination temperature and aluminum ion concentration on the preparation of pure-phase YAG powders were intensively studied. The results show that the well-dispersed YAG nano-powders can be prepared by this ultrasonic spray co-precipitation method. Well-crystallized YAG powers can be generated when the precursors, produced through top symmetric spray with ammonia as precipitation agent, are calcined at 1000 °C for 3 h. The average size of YAG particles is about 50 nm and well-dispersed.

Size Control of Particles with Changing Concentration of TIP used as a Precursor for Synthesis of TiO2 by Ultra-Sonic Spray and Pyrolysis Method

The nano sized titanium dioxide was synthesized by the ultra-sonic spray method and pyrolysis of TIP (titanium iso-propoxide), which was employed as the precursor solution. The fine liquid drop of the TIP sprayed by the ultra-sonic spray nozzle was conversed into TiO2 nano particles by pyrolysis through the hot tubular reactor. The concentration of TIP solution was controlled in the range of 0.1∼1.0 M and the morphology, the particle size, the crystal structure, and the surface area of synthesized TiO2 were investigated by SEM, TEM, XRD and N2-adsorption method, respectively. DSSC (dye sensitized solar cells) was also prepared by employing the synthesized TiO2 nano powder as the electrode and the photo-electrical property of TiO2 was compared in terms of efficiency of solar cells. It was further confirmed that the particle size of TiO2 was controlled with changing concentration of TIP solution. When 0.1 M TIP was used as the precursor solution, the size, the surface area and the crystal structure of synthesized TiO2 were approximately 10 nm (by TEM), 56 m2/g and the anatase structure, respectively. The particle size of TiO2 decreased with decreasing concentration of TIP solution. Therefore, it was concluded that the efficiency of DSSC's can be improved by employing high surface area and nano-sized TiO2 as the electrode.

Influence of annealing temperature on structural and optical properties of ZnO: In thin films prepared by ultrasonic spray technique

Transparent conducting indium doped zinc oxide was deposited on glass substrate by ultrasonic spray method. The In doped ZnO samples with indium concentration of 3wt.% were deposited at 300, 350 and 400°C with 2min of deposition time. The effects of substrate temperature and annealing temperature on the structural, electrical and optical properties were examined. The DRX analyses indicated that In doped ZnO films have polycrystalline nature and hexagonal wurtzite structure with (002) preferential orientation and the maximum average crystallite size of ZnO: In before and annealed at 500°C were 45.78 and 55.47nm at a substrate temperature of 350°C. The crystallinity of the thin films increased by increasing the substrate temperature up 350°C, the crystallinity improved after annealing temperature at 500°C. The film annealed at 500°C and deposited at 350°C show lower absorption within the visible wavelength region. The band gap energy increased from Eg=3.25 to 3.36eV for without annealing and annealed films at 500°C, respectively, indicating that the increase in the transition tail width. This is due to the increase in the electrical conductivity of the films after annealing temperature.

Modeling thin film formation by Ultrasonic Spray method: A case of PEDOT:PSS thin films

Recent improvements in electronic and optoelectronic devices based on solution processable polymers have motivated development of scalable processing techniques like Ultrasonic Spray technique. Including potential for roll to roll fabrication, it has many other strengths. However, with spray coating it can be difficult to prepare films with a smooth surface. Here, we present model for Ultrasonic Spray deposition of thin films, which establish a clear correlation between process parameters and the film formation process, which ultimately decide the structural features of the thin films. Based on the time to cover the spray deposition area by the sprayed droplets and the time for droplet evaporation, a balance parameter has been defined. It provides a mean to determine suitable process parameters for uniform film formation by Ultrasonic Spray method. The model is further modified for the region of higher solution flow rates, where non-uniformity in droplet distribution is introduced. The predictions based on the model have been experimentally verified with thin films of poly(3,4-ethylene dioxythiophene) doped with polystyrene sulphonic acid (PEDOT:PSS). The method presented here can be used to predict proper deposition parameters for smooth film deposition by Ultrasonic Spray technique. Finally, the effect of film morphology on the sheet resistance of thin films of PEDOT:PSS is also presented.

The pH Sensing Characteristics of the Extended-Gate Field-Effect Transistors of Multi-Walled Carbon-Nanotube Thin Film Using Low-Temperature Ultrasonic Spray Method

A novel, simple and low-temperature ultrasonic spray method was developed to fabricate the multi-walled carbon-nanotubes (MWCNTs) based extended-gate field-effect transistors (EGFETs) as the pH sensor. With an acid-treated process, the chemically functionalized two-dimensional MWCNT network could provide plenty of functional groups which exhibit hydrophilic property and serve as hydrogen sensing sites. For the first time, the EGFET using a MWCNT structure could achieve a wide sensing rage from pH = 1 to pH = 13. Furthermore, the pH sensitivity and linearity values of the CNT pH-EGFET devices were enhanced to 51.74 mV/pH and 0.9948 from pH = 1 to pH = 13 while the sprayed deposition reached 50 times. The sensing properties of hydrogen and hydroxyl ions show significantly dependent on the sprayed deposition times, morphologies, crystalline and chemical bonding of acid-treated MWCNT. These results demonstrate that the MWCNT-EGFETs are very promising for the applications in the pH and biomedical sensors.

Influence of substrate temperature and Cobalt concentration on structural and optical properties of ZnO thin films prepared by Ultrasonic spray technique

Pure and Cobalt doped zinc oxide were deposited on glass substrate by Ultrasonic spray method. Zinc acetate dehydrate, Cobalt chloride, 4-methoxyethanol and monoethanolamine were used as a starting materials, dopant source, solvent and stabilizer, respectively. The ZnO samples and ZnO:Co with Cobalt concentration of 2wt.% were deposited at 300, 350 and 400°C. The effects of substrate temperature and presence of Co as doping element on the structural, electrical and optical properties were examined. Both pure and Co doped ZnO samples are (002) preferentially oriented. The X-ray diffraction results indicate that the samples have polycrystalline nature and hexagonal wurtzite structure with the maximum average crystallite size of ZnO and ZnO:Co were 33.28 and 55.46nm. An increase in the substrate temperature and presence doping the crystallinity of the thin films increased. The optical transmittance spectra showed transmittance higher than 80% within the visible wavelength region. The band gap energy of the thin films increased after doping from 3.25 to 3.36eV at 350°C.