Electrochemical Deposition Of ZnO Research Articles

Thin-Film Nanocrystalline Zinc Oxide Photoanode Modified with CdO in Photoelectrocatalytic Degradation of Alcohols

Thin-film nanocrystalline zinc oxide electrodes were fabricated by electrochemical deposition of ZnO on FTO-coated glass slides. ZnO electrodes were promoted by CdO coating on top of ZnO in amounts corresponding to 0.8, 0.1, and 0.05 C cm−2 in electric units. Modification of ZnO by a small amount of CdO, corresponding to 0.05 C cm−2, shifts the photoactivity of the composite photoanode into the visible part of the solar spectrum. It is shown that the ZnO/(0.05C)CdO/FTO electrode demonstrates high efficiency in photoelectrochemical degradation of methanol, ethylene glycol, and glycerol when irradiated by a simulated sunlight. According to intensity-modulated photocurrent spectroscopy (IMPS), the effect is due to suppression of the electron–hole pairs recombination and increase in the rate of photo-induced charge transfer. Therefore, thin-film photoanodes based on zinc oxide modified by CdO can be used for photoelectrochemical degradation of byproducts of biofuel production glycerol, and of other alcohols.

Enhanced optoelectrical performance of ultraviolet detectors based on self-assembled porous zinc oxide nanostructures

A templated self-assembly technique was utilized in the present study to grow porous zinc oxide nanostructures. The nanostructures were formed by the electrochemical deposition of ZnO through the interstitial spaces between polymer microsphere templates. After the deposition, polymer microspheres were removed by dissolving in chloroform solvent, leaving porous ZnO nanostructures. This technique is benefited from facile controllability of the pore morphology and size by varying the diameter of microspheres. X-ray diffraction analysis showed a dominant peak corresponding to the hexagonal ZnO structure. Moreover, no significant structural strain was observed after the removal of spheres unlike the other synthesis methods of porous materials. The improved photoluminescence (PL) properties revealed an enhancement in the light capturing capability of the systems due to the multiple scattering of light in the pore walls. The porous sample showed a PL blue-shift compared to the flat one, indicating a reduction in crystallite size of ZnO nanostructures. To assess the photonic applications of synthesized porous ZnO substrates, a metal-semiconductor-metal photodetector was developed via the metallization of ZnO nanostructures, and their optoelectrical properties were tested under UV radiation. The results showed an improvement in photosensitivity and quantum efficiency of devices based on porous ZnO substrates which can be assigned to the larger exposed area and elevated rates of electron-hole generation in this sample.

Controlled growth of ZnO nanorods via self-assembled monolayer

A simple method to achieve tailored growth of ZnO nanorods by employing self-assembled monolayer of alkanethiol molecules on a conductive substrate is introduced. Defects or pinholes in self-assembled monolayer are used to define the nucleation sites of ZnO during electrochemical deposition. The density of ZnO nanorods is tuned by the quality of self-assembled monolayer. A corresponding growth model for the growth of ZnO on self-assembled monolayer-modified substrate is proposed. The dimensions and the nucleation density of ZnO nanorods are tailored by systematically varying the quality of self-assembled monolayer and the parameters of electrochemical deposition. Furthermore, it is shown that this method also allows for laterally patterned growth of ZnO nanorods via microcontact printing of self-assembled monolayer. Electrochemical deposition of ZnO on Au surface results in dense coverage of ZnO nanorods. Self-assembled monolayers are applied on Au to tune the density of ZnO nanorods. The pinholes in self-assembled monolayer are used to define the nucleation site of ZnO.

Electrodeposition and characterization of ZnO thin films using sodium thiosulfate as an additive for photovoltaic solar cells**Project supported by the Algerian Ministry of Higher Education and Scientific Research, Algeria (No. J0101520090018).

Zinc oxide thin films have been grown by electrodeposition technique onto Cu and ITO-coated glass substrates from an aqueous zinc nitrate solution with addition of sodium thiosulfate at 90 °C. The effects of sodium thiosulfate on the electrochemical deposition of ZnO were investigated by cyclic voltammetry and chronoamperometry techniques. Deposited films were obtained at −0.60 V vs. SCE and characterized by XRD, SEM, FTIR, optical, photoelectrochemical and electrical measurements. Thickness of the deposited film was measured to be 357 nm. X-ray diffraction results indicated that the synthesized ZnO has a pure hexagonal wurtzite structure with a marked preferential orientation along (002) plane. FTIR results confirmed the presence of ZnO films at peak 558 cm−1. SEM images showed uniform, compact morphology without any cracks and films composed of large flower-like ZnO agglomerates with star-shape. Optical properties of ZnO reveal a high optical transmission () and high absorption coefficient ( in visible region. The optical energy band gap was found to be 3.28 eV. Photoelectrochemical measurements indicated that the ZnO films had n-type semiconductor conduction. Electrical properties of ZnO films showed a low electrical resistivity of , carrier concentration of and mobility of 7.35 cm2 V−1 s−1.

Flower-like ZnO decorated polyaniline/reduced graphene oxide nanocomposites for simultaneous determination of dopamine and uric acid

A novel sensor was fabricated by electrochemical deposition of ZnO flower-like/polyaniline nanofiber/reduced graphene oxide nanocomposite (ZnO/PANI/RGO) on glassy carbon electrode (GCE) for direct detection of dopamine (DA) and uric acid (UA) in the presence of fixed concentration of ascorbic acid (AA). Surface morphology and characterization of the modified electrodes were confirmed by field emission scanning microscopy (FE-SEM), X-ray diffraction (XRD), Raman and FT-IR spectroscopies. For individual detection, the linear responses were in the two concentration ranges of 0.001–1 μM and 1–1000 μM with detection limit 0.8 nM (S/N = 3) for DA, and also 0.1–100 μM and 100–1000 μM with detection limit 0.042 μM (S/N = 3) for UA. Simultaneous determination of these species in their mixture solution showed the linear responses in the two concentration ranges of 0.1–90 μM and 90–1000 μM with detection limit 0.017 μM (S/N = 3) for DA and also showed two linear range of 0.5–90 μM and 100–1000 μM with detection limit 0.12 μM (S/N = 3) for UA, with coexistence of 1000 μM AA. The applicability of sensor for the analysis of DA, and UA in dopamine injection solution, human serum and human urine samples was successfully demonstrated.

Influence of counter-anions during electrochemical deposition of ZnO on the charge transport dynamics in dye-sensitized solar cells.

Porous ZnO/EosinY films have been electrochemically deposited by oxygen reduction in the presence of a zinc salt from EosinY-containing aqueous solutions, with either chloride or perchlorate as the counter anion. EosinY was removed and the films were sensitised by D149. These electrodes were used for dye-sensitised solar cells (DSCs), and charge transport in the porous network was studied by intensity modulated current/voltage spectroscopy (IMVS/IMPS) and electrochemical impedance spectroscopy (EIS) under illumination. Doping of ZnO during the electrodeposition could be proven by changes in the charge transport in ZnO and could be shown to occur when chloride was used as the counter ion. By using perchlorate as the counter ion, on the other hand, a more reproducible occupation of trap levels was obtained at, however, slightly lower voltages in DSCs whose origin is discussed in detail.

Initial Growth Process in Electrochemical Deposition of ZnO

ZnO thin films were prepared by electrochemical deposition on (111)Pt/c-sapphire from zinc nitrate aqueous solution by supplying constant current. All films were epitaxially grown, but with a wide distribution of in-plane orientation. For several tens of seconds after the start of the deposition, the time course of cathodic potential showed positive potential versus Ag/AgCl, which is out of range for ZnO growth. Then, the potential decreased abruptly to a negative value and remained constant in the growth range. To evaluate the initial crystal growth, the deposition was stopped immediately after the decrease in potential and the resultant film was characterized by reflective high-energy electron diffraction analysis. The sample was found to contain Zn(OH)2; therefore, the distribution of the in-plane orientation of the ZnO films is considered to arise from this initial growth of Zn(OH)2.

Initial Growth Process in Electrochemical Deposition of ZnO

ZnO thin films were prepared by electrochemical deposition on (111)Pt/c-sapphire from zinc nitrate aqueous solution by supplying constant current. All films were epitaxially grown, but with a wide distribution of in-plane orientation. For several tens of seconds after the start of the deposition, the time course of cathodic potential showed positive potential versus Ag/AgCl, which is out of range for ZnO growth. Then, the potential decreased abruptly to a negative value and remained constant in the growth range. To evaluate the initial crystal growth, the deposition was stopped immediately after the decrease in potential and the resultant film was characterized by reflective high-energy electron diffraction analysis. The sample was found to contain Zn(OH)2; therefore, the distribution of the in-plane orientation of the ZnO films is considered to arise from this initial growth of Zn(OH)2.

Improvement of Schottky Contact Characteristics by Anodic Oxidation of 4H-SiC

Anodic oxidation was performed to 4H-SiC in order to suppress the negative impacts on the Schottky diode characteristics. The electrochemical deposition of ZnO before and after the oxidation revealed a reduction in the number of areas with low Schottky barrier height. Before and after the oxidation, current-voltage characteristics of Ni Schottky contacts was compared, and it was found out that the characteristics were improved after the oxidation. These results suggest that the anodic oxidation is a promising technique to suppress the negative influence of the crystal defects.

Electrochemical deposition of zinc oxide on a thin nickel buffer layer on silicon substrates

Electrochemical deposition of ZnO from aqueous nitrate solutions on nickel and platinum electrodes was investigated using the voltammetry technique to determine the optimal regimes in both potentiostatic and galvanostatic modes for acquiring polycrystalline ZnO films. Scanning electron microscopy, X-ray diffractometry, and X-ray microanalysis of the formed ZnO films are presented, showing a polycrystalline structure of the ZnO films with a preferable orientation in the (0 0 0 2) direction and an exact stoichiometric composition. The deposited ZnO films demonstrate a strong visible yellow-greenish photoluminescence at room temperature with a maximum at 600 nm that can be referred to crystal lattice oxygen defects. The maximum of the photoluminescence excitation spectrum at 370 nm corresponds to the band gap of ZnO (3.3–3.35 eV) confirming that band-to-band excitation mechanism takes place.

Electro-chemical deposition of ZnO under irradiation of UV for stabilization of the growth rate

Electro-chemical deposition of ZnO under irradiation of UV for stabilization of the growth rate

Electrodeposition of porous zinc oxide electrodes in the presence of sodium laurylsulfate

Thin porous films of crystalline ZnO have been prepared by cathodic electrodeposition from aqueous oxygen saturated zinc chloride solution in the presence of additives, such as different small organic acids (benzoic acid, p-toluenesulfonic acid, benzenetetracarboxylic acid) and a surfactant (sodium laurylsulfate). The small negatively charged additives influence the growth rate of ZnO due to the increase in the current density during electrodeposition with increasing number of functional groups. However, they do not change the morphology of the resulting ZnO films.The influence of sodium laurylsulfate on the growth rate of ZnO depends on its concentration. As long as the concentration is low there is only slight effect. However, if the provided concentration is high enough to achieve formation of micelles and to get assembly of these micelles on the charged electrode surface, the current density found during electrochemical deposition of ZnO was extremely high, indicating a strongly increased growth rate due to the catalysis by sodium laurylsulfate. The resulting films show remarkably different morphology, large surface area and good porosity. Sodium laurylsulfate incorporated in the ZnO films could be removed almost completely from the pores by extraction with ethanol without affecting the crystallinity of the material.